Technical language barriers are quite commonplace today, and
most of us have been confronted with at least a few elements
of such a barrier from time to time. Advances in technology,
and the introduction of new or unfamiliar product areas, all
require an expansion of our technical vocabulary if we are
to communicate effectively. Hopefully, this edition of the
Glossary will serve as a valuable reference for improved
communications.
Acceptable Quality Level:
The maximum number of defects per every 100 units that are
considered to be satisfactory as a process average.
Acrylic:
A synthetic resin made from acrylic acid or a derivative
thereof. Acrylics possess the property of transparency, as
well as offer flame resistance.
Activated Rosin Flux:
A mixture of rosin and small amounts of organic-halide
activators or organic-acid activators.
Activators:
A substance that enhances the ability of a flux to remove
oxides and other contaminants from surfaces being joined.
Active Components:
Electronic components such as semiconductors, transistors,
diodes, etc., that can operate on an applied electrical
signal and change its basic characteristics (e.g.,
switching, amplification, rectification).
Active Hold-Down:
The process of pressing a component lead directly in contact
with a bonding pad during soldering to ensure intimate
contact between the lead and pad. Intimate contact is
important for proper heat transfer through the lead to
reflow the solder. This is a characteristic of hot bar
soldering, which utilizes a thermode to press the leads
against the bonding pads.
Additive Plating:
A process in which the conductive, resistive, and insulating
materials are successively plated to define traces, pads,
and elements.
Adhesion:
The state in which two surfaces are held together by means
of interfacial forces.
Adhesive:
A substance capable of holding materials together by surface
attachment.
Adsorption:
The adhesion of gases or liquid molecules to the surface of
solids or liquids with which they are in contact.
Aerosol:
Fluid or gas particles small enough to be airborne.
Aerosol:
Fluid or gas particles small enough to be sprayed.
Aging:
The change in the properties of a material over time and
under varying conditions of humidity, temperature, pressure,
etc.
Alignment Holes (or Tooling Holes):Holes
specifically designed in
TAB tape
for registration of a TAB frame. These holes can be located
virtually anywhere on the tape site, however, locations are
standardized in many cases.
Alloy:
A mixture of two or more metals combined to achieve
properties, such as a lower melting point or greater
strength, that the individual metals do not possess.
Analog Circuit:
An electrical circuit that provides a continuous
relationship between its input and output.
Angle of attack:
The angle between the squeegee face and the plane of the
stencil.
Anisotropic Conductive Adhesive:
Conductive adhesives that conduct electricity in one
direction only. Also referred to as "Z-axis conductive
adhesives." When using this type of adhesive, high Z-axis
forces are required during bonding. Components attached
using this material use the pick, place, and attach process.
Anisotropic:
A material that exhibits different properties when tested
along axes in different directions.
Annular Ring:
That portion of conductive material completely surrounding a
hole.
AOI:
(Automatic Optical Inspection) To inspect a pattern or
object using a camera in an automated system.
APQP:
Advanced Product Quality Planning is a structured method of
defining and establishing the steps necessary to assure that
a product satisfies the customer. The goal of a product
quality planning is to facilitate communication with
everyone involved to assure that all required steps are
completed on time.
AQL:
Abbreviation for "Acceptable Quality Level". A method of
random sampling rather than 100 percent inspection.
Aqueous Cleaning:
A cleaning technique that uses water as the primary cleaning
fluid.
Aqueous Flux:
An organic-chemical soldering flux that is soluble in water.
Area Array TAB:
A mounting configuration for a TAB frame to an IC where the
inner leads are connected to bumps in an array pattern on
the surface of the IC instead of on the perimeter, which is
the case for typical TAB components.
Array:
A group of elements, such as solder bumps, or circuits
arranged in rows and columns on a substrate.
ASIC:A
custom made circuit used for a specific application.
Assembly:
A group of components physically joined to a PCB or ceramic
board.
ATE:
Equipment that automatically analyzes functional or static
parameters to evaluate performance.
Azeotrope:
A blend of two or more polar and nonpolar solvents that act
as a single solvent and can be used to remove both polar and
nonpolar contaminants.
Azeotropic Mixture:
A liquid mixture of two or more substances that behaves as a
single substance.
Bake Out:
Subjecting a laminate to an elevated temperature in order to
remove moisture and unwanted gases prior to final sealing.
Ball Grid Array:A leadless surface-mountable package in which solder ball
interconnects cover the bottom surface of the package in a
check board fashion. BGAs are reflow soldered to PCBs using a
mass reflow process.
Bare Board:
An unassembled (unpopulated) printed board.
Bed-of-Nails Fixture:
A test fixture consisting of a frame and holder containing a
field of spring-loaded pins that make electrical contact
with a planar test object.
Bend Radius:
The radius at the inside of the bends at both the lead
shoulder leading to the leg and the base of the leg leading
to the foot.
BGA:
A leadless surface-mountable package in which solder ball
interconnects cover the bottom surface of the package in a
check board fashion. BGAs are reflow soldered to PCBs using a
mass reflow process.
Bias Cut:
Material cut at 45 degrees from the normal weave pattern.
Binder:
the organic or inorganic material which encapsulates and
holds together the base in reinforced or otherwise
heterogeneous composites.
Blind Via:
A via hole extending only to one surface of a printed
circuit board.
Blister:
A localized swelling and separation between any of the
layers of a laminated base material, or between base
material and conductive foil. It is a form of delamination.
Blow Hole:
A void caused by outgassing. (Outgassing is a gaseous
emission from a printed circuit assembly when exposed to a
reduced pressure or heat or both.
Board:
An organic printed circuit card or board on which smaller
components, cards, or modules can be mounted.
Bond lift-off:
A failure by separation of a bonded (or soldered) lead from
the pad surface (substrate).
Bond Strength:
The force per unit area required to separate two adjacent
layers of a package. The force is applied perpendicular to
the surface of the package.
Bonding Alloy:
A term sometimes substituted for solder. The "bonding alloy"
can be application specific; the most common to fine pitch
bonding is eutectic Sn/Pb solder.
Bonding Pads:
Copper traces, or pads, on a substrate to which leads are
bonded. Dimensions and thermal path from the bonding pads
must be properly designed to achieve uniform solder reflow.
Bonding:
The joining of two materials. For instance, the attachment
of a component to a substrate.
Boundary Scan:
An approach to the testing of printed circuit board
assemblies that can be used to diagnose individual circuit
failures by embedding the test circuits into the board and
in the most failure-prone integrated circuits.
Bow:
The deviation from flatness of a board characterized by a
roughly cylindrical or spherical curvature such that if the
board is rectangular, its four corners are in the same
plane.
Breakaway panels:
PCBs held together with breakaway tabs to make handling,
placement and soldering easier and more efficient. Boards
are snapped apart at the end of processing.
Bridge:
Solder that effectively joins two conductors that should not
be electrically connected, causing a short.
British Thermal Unit (B.T.U.):
the quantity of heat required to raise the temperature of
one pound of water 1°F from 58.5°F to 59.5°F (its point of
maximum density).
Built-in Lead Stress:
The force within leads of a molded carrier ring or TAB
component that result in lead skew or splay after the
excising process. Possible causes include the dam bar
removal process, the stamping process used to produce lead
frames, or stress induced during prior thermal or mechanical
processing of the components.
Built-In Self Test:
An electrical testing technique in which hardware is added
to the chip to allow the integrated circuit to test itself
with minimal use of test equipment.
Bump:
A small mound formed on the device or the substrate pads
that can be used as a contact for face-down bonding. This is
a method of providing connections to the terminal areas of a
device.
Burn-In:
The process in which a device is electrically stressed by
subjecting it to an elevated temperature and voltage for an
adequate period of time to cause the failure of a marginal
device.
Butt Joint:
A solder joint where the end of the lead sits on the solder
pad.
- C -
C-4 (Controlled Collapse Chip Connection):
A solder joint connecting a substrate directly to an IC in a
flip chip configuration. In this packaging scheme, a solder
ball is formed on the IC, the IC is placed active circuitry
down onto a substrate, and the solder is reflowed. As the
solder melts, the solder balls collapse into a shape
controlled by the surface tension of the liquid solder while
supporting the weight of the IC.
C-5 (Controlled Collapse Chip Carrier Connection):
The same technology as C-4 except the IC is mounted in an
intermediate carrier (ceramic or FR-4) using conventional
technology, and the chip carrier, having the solder balls,
is mounted directly to the substrate and reflowed.
C-Stage:
Refer to "laminate."
CAD/CAM:
Computer-aided design is the use of special software tools
to formulate printed circuit patterns. Computer-aided
manufacturing translates such designs into actual products.
These systems include mass memory for data processing and
storage, inputs for design creation and output devices for
converting stored information into drawings and reports.
Capillary Action:
The effect of surface tension that draws a liquid into a
small opening. So a combination of natural causes that
forces molten solder to flow against gravity between closely
spaced solid surfaces.
Card:
A printed circuit board of smaller dimensions is commonly
referred to as a card. A card is generally one level lower
than the printed circuit board in the hierarchy of
packaging. A card is also referred to as a daughter board.
Celsius:
also referred to as Centigrade, is equal to the difference
between the temperature in Fahrenheit less 32 and the
quantity divisible by 1.8.
formula: °C = (°F-32) ÷ 1.8
CEM-1:
CEM-1 is a paper based laminate with one layer of woven
glass fabric. It is not suitable for PTH.
CEM-3:
CEM-3 is a laminate very similar to FR4. Instead of woven
glass fabric a 'flies' type is used. CEM-3 has a milky white
color and is very smooth. It is a complete replacement for
FR4 and has a very large market share in Japan.
Ceramic Column Grid Array (CCGA):
The same as CBGA except the solder balls are replaced by
solder columns. The advantage of columns is that the
inherent flexibility of the columns help compensate for CTE
mismatch between the ceramic component and the FR-4 board.
Columns are required rather than solder balls for components
greater than 25mm square.
Ceramic:
An inorganic, nonmetallic material. Examples include alumina
or glass-ceramic. Ceramics are often used in forming ceramic
substrates for the packaging of semiconductor chips.
CFC:
A chlorinated fluorocarbon that can cause ozone layer
depletion. The use of CFCs is restricted by the
Environmental Protection Agency. CFCs are primarily used in
air conditioning and refrigeration, foam insulators, and
cleaning solvents.
Chip Carrier:
An integrated circuit package that is usually square and may
possess a cavity for a chip in the center and whose
connections are typically on all four sides.
Chip:
The individual circuit or component of a silicon wafer. The
leadless form of an electronic component part, either
passive or active, discrete or integrated.
Circuit:
The interconnections of electrical elements and devices that
perform a desired electrical function.
Circuit tester:A object that has the means to test a circuit
Clamshell Fixture:
An in-circuit test fixture designed to probe both sides of a
PCB.
Cleaning:
An operation involving the removal of flux residues and
other contaminants from the surface of a PCB assembly.
Cluster Testing:
A variation of the in-circuit testing procedure in which a
cluster of components are tested as a functional unit.
Coating:
A thin layer of material, conductive or dielectric, applied
over components or a base material.
COB:
A configuration in which a face-up bonded chip is directly
attached to a printed circuit board or substrate and
exclusively interconnected to the substrate conventionally,
i.e., by flying wires.
Coefficient of Thermal Expansion (CTE):
The ratio of change in dimensions to original dimensions per
degree rise in temperature, expressed in ppm/ºC.
Cofiring:
A process for forming multilayer ceramic substrates in which
thick- film conductors and dielectrics are simultaneously
processed by a firing cycle.
Cold solder joint:
A connection reflecting poor wetting action and
characterized by a gray, porous appearance owing to
insufficient heat or inadequate cleaning.
Comb Pattern:
A set of comb-like arrays of uniformly spaced conductors.
Component:
An individual functional element in a physically independent
body (e.g., resistor, capacitor, or transistor).
Component density:
The number of parts on a PCB divided by board area.
Component Lead:
A wire or formed conductor that extends from a component and
serves as a mechanical and/or electrical connection. Leads
can readily be formed to a desired configuration.
Conduction:
The thermal transmission of heat energy from a hotter region
to a cooler region in the presence of a conducting medium.
Conductor, Electrical:
A class of materials-usually metals-that easily conducts
electricity. Examples include silver, copper, gold, and
super-conducting ceramics.
Conductive Epoxy:
A polymer material made to pass electrical current by the
addition of metal particles, usually silver.
Conductor, Thermal
: A class of materials-usually metals-that easily conduct
heat. Examples include copper, aluminum, and beryllia.
Conformal Coating:
A thin non conducting coating that is either plastic or
inorganic and is applied to a circuit for environmental and
mechanical protection.
Contact Angle:
The angle between bonding material and a bonding pad. Also
called the wetting angle.
Contact Printing:
A type of printing where there is no gap between the stencil
and the substrate.
Contact Resistance:
The maximum resistance allowed between a pin and the socket
contacts of a connector when assembled and in use.
Contact Time:
Refer to "Dwell time."
Contaminant:
An undesirable material that can adversely influence the
properties of a material or the quality of a product. A
contaminant can be liquid or solid.
Continuous Tape:
A TAB tape handling scheme that uses a continuous reel of
polyimide tape to mount and carry TAB components through the
assembly process. Typically, the tape width conforms to
industry standards, with 35mm, 48mm, and 70mm widths being
the most common.
Control Limit:
Lines drawn on a control chart that illustrate the
boundaries of variation from sample to sample, or
roll-to-roll. It is calculated from process data. It is not
an arbitrary boundary.
Convection:
The transfer of heat by movement of hot air. (Often used in
conjunction with infrared radiation to reduce the effect of
IR shadowing. )
Coplanarity:
The maximum distance between the lowest pin and the highest
pin when a package rests on a perfectly flat surface.
Copper Clad Laminate:
laminates (i.e. FR4) having copper foil bonded to one or
both surfaces and intended primarily for use in printed
circuits.
Copper foil:
A cathode-quality electrolytic material deposited as a thin,
continuous sheet on substrates as a conductor for PCBs. It
readily bonds to insulators, accepts the printed resists and
etches out to form the circuit pattern.
Copper mirror test:
A flux corrosivity test using a vacuum-deposited film on a
glass plate.
Corrosion:
A chemical action that causes the gradual deterioration of
the surface of a metal by oxidation or chemical reaction.
Corrosive Flux:
A flux that contain levels of activators like halides,
amines, or organic acids that can cause the corrosion of
copper.
Cp Index:
(Capability Performance) A measure of the relationship
between the allowable process spread (part tolerance) and
the actual process spread (natural tolerance). (A Cp value
greater than 1.0 indicates that the process is capable of
achieving its desired results.)
Cpk Index:
(Process Capability Index) Ability to meet a customer's
specification. A measure of the relationship between the
scaled distance between the process mean value and the
closest specification limit.
Crazing:
Minute lines appearing in or near the surface of materials
such as plastics, usually resulting as a response to
environment. Crazing cannot be felt by running a fingernail
across it (if the fingernail catches , it is a crack).
CTE:
(Coefficient of Thermal Expansion) A characteristic
thermomechanical property of a material or a composite. It
is the tendency of a material to expand as it is heated. In
laminate, in-plane (x and y direction) and out-of-plane
(z-direction).
CTE Mismatch:
The difference in the coefficients of thermal expansions of
two materials or components joined together, which produces
strains and stresses at joining interfaces or in attachment
surfaces.
CTI:
Comparative Tracking Index. Indicates the highest usable
voltage for alaminate. It becomes important in application
with high humidity, such as washing machines or cars. A
higher index means a better protection. Similar is 'PTI' and
'KC'.
Cure:
to change the physical, chemical, or electrical properties
of a material by chemical reaction, by the action of heat
and catalysts alone or in combination, with or without
pressure. Specifically to convert a low molecular weight
polymer or resin to and insoluble, infusible state.
Curing Cycle:
The time-temperature profile needed to cure a thermosetting
material like a bonding adhesive.
Curing Time:
The time needed to properly cure a thermosetting plastic
material.
Curing:
A change in the physical properties of a material via
chemical reaction or by reaction to temperature-time
profile.
Cycle rate:
A component placement term measuring machine speed from
pickup to board location and return. Also called the test
rate.
Dam Bar:
A temporary part of the lead frame used to inhibit the flow
of plastic during the molding process for molded carrier
ring (MCR) and plastic quad flatpack (PQFP) components. The
dam bar is removed prior to testing or placing the component
because it is a part of the copper lead frame and thus
shorts all of the leads together.
DCA:
Direct Chip Attach. A chip-to-substrate connection intended
to reduce the first level of packaging. Here, the silicon
die is inverted and mounted directly to the PCB. Also
referred to as chip-on-board technology.
Defect:
Any nonconformance to specified requirements by a unit or
product.
Deionized Water:
Water that has been treated to remove ionized material.
Delamination:
A separation between plies within the base material, or
between the base material and the conductive foil, or both.
Dendritic Growth:
The metallic growth between pads in the presence of moisture
and an electrical bias.
Density:
The weight of a material in relationship to its volume.
Device:
An individual electrical circuit element that can't be
further reduced without destroying its intended function.
Dewetting:
A situation where a lead or pad was at one point in the
soldering process wetted by the solder, but due to extended
time or temperature, the presence of intermetallics,
volatiles or other causes, has become withdrawn from the
wetted surface.
Die Bonder:
The placement machine for chips in a chip-on-board process
line.
Die Bonding:
The attachment of an integrated circuit chip to a substrate.
Die Sorter:
Equipment that picks die from a wafer and presents them for
their next process step. When used in reference to bare die
placement machines, the die are presented for pick by the
machine's placement nozzles.
Die:
Integrated circuit chip as diced or cut from the finished
wafer.
Dielectric:
Non conducting material used to encapsulate circuitry and in
the manufacture of capacitors and printed circuit boards.
Diffusion:
A material transport phenomena that occurs in solids, and is
caused by the continual physical motion of atoms from one
position to another. This results in the flow of material
from regions of high concentration to regions of low
concentration.
Dilatant:
Fluid characterized by an increase in viscosity with an
increasing shear rate.
DIP Socket:
A connector for a Dual In-Line Package, or one that has its
leads in two parallel rows.
Direct Chip Attach Module :
A component type developed by IBM® consisting of a small
substrate with flip chips attached using the
DCA
process. This small substrate, or module, is now a component
with solder pads on the bottom side that can be mounted to a
board using conventional surface mount processes.
Dispersants:
Organic and inorganic phosphates and polymers used in
aqueous cleaning to assist in the removal of insoluble
particles.
DOE:
(Design of Experiment) Procedure for establishing an
experiment in which the results (output variables) can be
related to a structured set of factors (input variables).
Double-Sided Assembly:
A fully assembled PCB with components on both sides of the
substrate.
Downtime:
The period in which equipment is not producing product owing
to maintenance or failure.
Dross Content:
A measure of the cleanliness of solder powder.
Dross:
Any oxide or other contamination formed on the surface of
molten solder.
Dry Film Photoresist:
Solid photoresist applied to a surface by lamination of
prefabricated film.
Dual In-Line Package (DIP):
A package with two rows of leads extending at right angles
from the base with standard spacing between the leads and
row. This package is intended for through hole mounting.
Durometer:
The measure of rubber or plastic hardness, as with the
squeegee blade.
Dynamic Flex:
A flex circuit in constant motion, for example, in a printer
head.
- E -
Elastomeric:
A material that at room temperature can be stretched
repeatedly to at least twice its original length, and upon
release of the stress, will return with force to its
approximate original length. A rubber band is an example.
Electro-Deposit Copper:
Copper used in manufacturing TAB tape. From a sputtered seed
layer of copper, the copper is electroplated (grown) to a
desired thickness, typically 1 ounce or 1.4 mils thick. The
copper is usually grown on a base material, and is separated
from this material upon completion of the deposition
process.
Electrode:
A conductor through which a current enters or leaves an
electrolytic cell, vacuum tube, or any nonmetallic
conductor.
Electroless Plating:
Deposition of metal (without any external electric current)
by an exchange reaction between metal complexes in the
solution and the metal being coated.
Electroplating:
A method of electrically depositing metals of very precise
compositions and thicknesses onto a base metal.
Electromigration:
The electrolytic transfer of metal from one conductor to
another conductor separated from the first conductor by a
dielectric medium.
Electronic Packaging:
The technology of interconnecting semiconductor and other
electronic devices to provide an electronic function.
Electroplating:
Deposition of metal onto a cathodic surface by passing DC
current into an electrolytic solution.
Elongation:
the fractional increase in length of a material stressed in
tension.
Emissivity:
The ratio of the radiant energy emitted by a source to the
radiant energy of a perfect radiating surface (black box)
having an equivalent surface area with all other relevant
conditions being the same.
Emulsion:
A stable mixture of two or more immiscible liquids held in a
suspension by small percentages of emulsifiers.
Encapsulant:
The material used to cover
COB
devices to provide mechanical protection and to ensure
reliability, typically an epoxy.
Encapsulation:
The sealing or covering of an element or circuit for the
purpose of mechanical and environmental protection.
Epoxy Resin:
A material that forms straight chain thermoplastic and
thermosetting resins. Expoxy resins have excellent
mechanical properties and good dimensional stability.
Epoxy:
A thermosetting polymer containing the oxirane group.
Eutectic:
The minimum melting point of a combination of two or more
materials. The eutectic temperature of an alloy is always
lower than the melting point of any of its individual
constituents. The eutectic temperature is the particular
temperature at which the eutectic occurs. Eutectic alloys,
when heated, transform directly from a solid to a liquid and
do not show any pasty regions. For example, eutectic solder
paste has a composition of 63% tin (Sn) and 37% lead (Pb),
and has a eutectic temperature of 183ºC.
Excising:
Cutting component leads free from the remainder of the
package to prepare the component for forming or placement.
- F -
Failure:
The temporary or permanent functional impairment of a
component or device caused by physical, mechanical,
chemical, or electrical damage.
Fahrenheit:
equals 1.8 multiplied to the sum of the temperature in
Celsius and 32.
formula: - °F = 1.8 x (°C + 32)
Fiducial:
A specific mark incorporated in the circuit artwork and used
by machine vision to identify artwork orientation and
location.
Filler Materials:
Ceramic or metallic particles used to modify the properties
of polymers.
Fillet:
A smooth, concave junction where two surfaces meet. The
quality of a solder fillet determines the strength of the
joint.
Fine Pitch:
Surface mount components with a lead pitch of at least 50
mils. Fine pitch is more commonly used to refer to
components with a lead pitch of 25 mils or less. These
packages usually require vision assistance for accurate
placement.
Fixture:
A device that interfaces the PCB to the process machine
center(s).
Flat Pack:
An integrated circuit package with leads on two or four
sides. The leads on these packages are either gull wing or
flat, and have standard spacing. Packages with a lead pitch
below 50 mils are referred to as fine pitch packages.
Flex Circuits:
Flexible printed circuit boards made using thin polyimide or
polyester film with copper circuitry on one or both sides of
the flex. Flex circuits can be single or multilayer.
Flip Chip:
Any packaging scheme in which the active circuitry of an IC
is placed facing the surface of the substrate. So A leadless
structure which is designed to electrically and mechanically
interconnect to the circuit by means of an appropriate
number of bumps located on its face which are covered with a
conductive bonding agent. Examples are flip TAB and C-4.
flip chip interconnection:
In this process, the bumped device is mounted to the
substrate active side down. The technique is called "flip
chip" because the active circuitry faces down instead of up,
as in the case of wire bonded devices.
Flip TAB:
A mounting configuration for a TAB component where the
active circuitry of the IC is placed facing the surface of
the substrate.
Flood bar:
A device on a stencil-printing system that drags solder
paste back to the starting point after the squeegee has made
a printing stroke.
Fluorocarbon:
The liquid vaporized in Vapor Phase reflow soldering.
Flux Activation Temperature:
The temperature at which flux is active enough to remove
oxides from the metals being joined.
Flux Activity:
The efficiency of a flux to promote the wetting of a surface
with molten solder.
Flux Characterization:
Tests performed to determine the properties of fluxes and
flux residues.
Flux Residue:
A flux-related contaminant present on or near the surface of
a solder connection.
Flux Solder Connection:
A solder joint with entrapped flux, causing high electrical
resistance.
Flux:
A chemically- or physically-active formulation capable of
cleaning oxides and enabling wetting of metals with solder.
FMEA:
Failure Mode and Effects Analysis. An FMEA can be described
as a systemized group of activities intended to: 1)
Recognize and evaluate the potential failure of a
product/process and its effects, 2) identify actions which
could eliminate or reduce the chance of the potential
failure occuring, and 3) document the process.
Foot Angle:
The angle of the lead foot after lead forming with respect
to the plane defined by the bottom of the component.
Foot Length:
The part of the component lead that comes in contact with
the bonding pad on the substrate.
Footprint:
The pattern on the printed circuit board to which the leads
on a surface mount component are mated. Also called a land
or a pad.
FR-1:
Is basically the same as FR2. FR1 has a higher TG of 130ºC
instead of 105ºC for FR2. Some laminate manufacturer which
produce FR1 will not produce FR2, since cost and usage are
similar and there is no advantage for having both.
FR-2:
FR2 is a Paper material with phenolic binder.
FR-3:
FR3 is mainly a european product. It is basically FR2 - but
instead of phenolic resin it uses a epoxy resin as binder.
The basic layer is paper.
FR-4:
FR4 is a glass fiber epoxy laminate. It is the most commonly
used PCB material. 1.60mm FR4 uses 8 layers of glass fiber
material. It is usually transparent. The green color comes
from the solder mask in the PCB finished product.
Functional Test:
The electrical testing of an entire assembly that simulates
the intended function of the product.
Gang Bonding:
A process in which multiple mechanical or electrical bonds
are made by means of a single stroke of a bonding tool.
GelPak:
A matrix tray style feeder without pockets, that consists of
a tacky gel over a mesh. The components are placed in a
regular array on the tray and are held in place by the tacky
gel. When picking components, vacuum is applied through the
bottom of the tray, pulling the gel through the mesh and
releasing the die.
Glass Fabric:
Glass yarns woven in a specific pattern.
Glass Transition Temperature:
The temperature above which a polymer loses its properties
of glass and behaves as an elastomer. Glass transition
temperature is characterized by a decrease in elastic
modulus and an increase in CTE.
Golden boy:
A component or assembly tested and known to function to
spec, then used to test other units via comparison.
Green Strength:
The strength of a substance, joint, or assembly before it
has been cured.
Ground Plane:
An electrically-conductive plane in a multilayer circuit
that connects a number of circuit elements to grounding
electrodes.
Gull Wing Lead:
A lead configuration, usually found on small outline
packages, where the leads are bent. The end view of these
packages resembles a gull in flight.
- H -
Halide:
Compounds containing fluorine, chlorine, bromine, iodine or
astatine. They may be part of a flux system (as activators)
and, as corrosives, must be removed.
Halide Content:
The ratio of the mass of free halides to the mass of solids
in a flux, expressed in mass percent of free chloride ions.
Halo:
A bright or dark ring around a drop of molten solder on a
flat surface.
Hard water:
Water containing calcium carbonate and other ions that may
collect on cleaning equipment interiors and cause clogging.
Hardener:
A chemical added to a resin to advance curing, i.e., a
curing agent.
Heat Treating:
A process that uses precise heating and cooling of metals
after stamping and forming in order to optimize internal
stresses and spring properties.
Hermetic:
The sealing of an object so it is airtight.
Hot Bar Soldering:
A process in which a heated bar simultaneously solders all
the leads of a device to the pads on a PCB.
Hot Gas Reflow:
A solder reflow process that uses a heated gas, including
air, as the mode of heat transfer.
Hydrophilic Solvent:
Refer to "polar solvent."
Hydrophobic Solvent:
Refer to "nonpolar solvent."
- I -
ICT:
An electrical test of a PCB assembly in which each component
is tested individually, even though many components are
soldered to the PCB.
ILB Window:
The opening in TAB tape where the innermost extremities of
the lead are bonded to the IC.
In-Circuit Test:
Inert Atmosphere:
A gaseous atmosphere that is not conducive to chemical
reactions, such as helium or nitrogen.
InfraRed (or IR) Reflow:
A technique in which long wavelength light serves as the
heat source to reflow solder and form solder joints.
Innovation:
Innovation is the whole process from: invention,
development, pilot production, marketing, production.
Invention is just invention (.Innovation = creative idea +
implementation.)
IR Shadowing:
When connector bodies or other components prevent the
infrared energy from directly striking some solder joints,
causing non-uniform heating.
Injection Molded Boards:
Printed circuit boards made by molding filler-reinforced
resins into a desired shape. Routing and through hole
metallizations are performed by seeding and plating, or by
printing. An alternative approach is to transfer mold the
interconnect directly onto the injection molded cards.
Inner Lead Bonding (ILB):
The process of attaching the IC to a TAB tape site.
Inner Lead:
The innermost portion of the lead on a TAB tape site that
extends into the ILB window.
Inner Ring:
A strip of polyimide between the inner and outer lead
bonding areas on a TAB tape site. This strip typically
encircles the entire IC. It is a common feature in many
TAB tape
designs, but is not found in all cases.
Inorganic Flux:
An aqueous flux solution of inorganic acids and halides.
Insulators:
A class of materials that do not conduct electricity and are
characterized by high resistivity.
Integrated Circuit:
A microcircuit that consists of interconnected elements
inseparably associated and formed in-situ on or within a
single substrate, usually silicon, to perform an electronic
circuit function.
Interconnect:
The conductive path required to achieve connection from one
circuit element to another.
Interconnection:
The conductive path required to achieve a connection from a
circuit element to the remainder of the circuit.
Interleaver:
A polyester film used to protect and separate TAB tape
layers. It is used whenever
TAB tape
or TAB components are handled in a continuous tape format.
Intermetallic:
Chemical compounds formed between the metals present in the
solder, base metal and protective platings. Intermetallic
formation is necessary for good solder joints, but excessive
intermetallics can cause brittleness.
Isotropic Conductive Adhesive:
Isotropic adhesives conduct electricity in all directions.
This means the adhesive can be dispensed only on those areas
(pads) where a circuit path is required (i.e., where bumps
will attach).
JIT:
Minimization of inventory by supplying material and
components to the production line directly before placement
into the product.
Just-In-Time:
J-Lead:
A lead configuration usually used on plastic chip carrier
packages. J-leads are bent underneath the body of the
package, with a side view resembling the shape of the letter
"J."
- K -
Keeper Bar:
A nonconductive polyimide strip located at the end of the
leads to be bonded. Its purpose is to maintain lead
integrity from the time the component is excised until it is
bonded in place. Keeper bars are typically formed during the
excising process, and are mainly found on extremely fine
pitch components.
Kelvin:
The absolute temperature scale (metric).
formula: - K = °C + 273
- L -
Laminate:
A stack of prepregs with copper foils on either surface
after lamination during PCB fabrication.
Lamination:
A heat and pressure cycle used to consolidate a stack of
prepregs into a solid block. The term also refers to the
consolidation of a stack of laminates (with circuitry) to
form a PCB. Lamination is referred to as the C-stage in PCB
fabrication.
Land Pattern:
The complete configuration of the lands to which a surface
mount component is attached. Also called a footprint or a
pad.
Land:
A metallized conductor on a PCB that is designed to accept a
surface mount component lead.
Laser Soldering:
A method of soldering in which the heat required to reflow a
solder interconnection is provided by a laser (YAG or CO2).
In this process, the solder joints are heated sequentially
and cooled rapidly.
Laser:
An acronym for "Light Amplification by Stimulated Emission
of Radiation."
Leaching:
The movement of metal atoms from the lead base metal into
liquid solder. This is prevented by nickel plating. May also
refer to alloying of a gold protective plating into the
solder.
Lead (Pb):
A soft heavy gray metal used in solder and other alloys.
Lead Configuration:
The conductors extending from a device, which function as
both mechanical and electrical connection points.
Lead Coplanarity:
The position of all of the component leads with respect to
one another using a reference plane defined by the three
lowest leads of a component.
Lead Forming:
After excising, forming the lead into a specific shape or
profile required for placement and bonding. The typical lead
form profile is a gull-wing shape.
Lead Frame:
A sheet metal framework etched to form an array of metal
traces (leads). An IC is attached to the lead frame at the
innermost portion of the leads, and the outermost portion of
the leads is attached to the next level of the assembly.
However, lead frames are the basis for molded carrier ring
(MCR) and plastic quad flatpack (PQFP) components, while TAB
frames are the basis for TAB components.
Lead Pitch:
The sum of the lead width and lead spacing. Typically stated
as the distance between the center of one lead to the center
of an adjacent lead.
Lead Plating:
The metal coating on a component lead. Common lead plating
materials are pure tin (Sn), pure gold (Au), and eutectic
tin/lead solder (63% Sn/37% Pb).
Lead Spacing:
The distance between adjacent leads in a defined area of a
component.
Lead Thickness:
In reference to component leads, it is the sum of the
thickness of the base metal, plating, and total fabrication
tolerances. Lead thickness is a critical element in
determining the dimensions and proper clearances in excise
and form tooling.
Lead Width:
The width of the lead in a defined area of a component.
Lead:
A wire that connects two points in a circuit; it is usually
self-supporting.
Leaded Device:
Electronic devices that have electrical leads extending from
the body of the package.
Leadless Device:
Electronic devices which do not have electrical leads
extending from the body of the package. These packages could
have solder bumps or lands located on the package.
Leakage Current:
A small amount of current that flows through or across an
insulator between two electrodes.
Leg Angle:
The angle of the vertical portion of a lead with respect to
a plane perpendicular to the plane defined by the bottom of
the component.
Leg Length:
The part of the component lead between the two bend radii.
The leg length is directly related to the overall lead form
height.
- M -
Mean time between failure:
Melting Range:
The difference between the solidus and liquidus temperature.
Mesh Porosity:
The ratio of the amount of open area in a mesh versus the
amount of closed area in a mesh.
Mesh Size:
The number of openings per inch in a screen. For example, a
325 mesh screen has 325 openings per inch.
Metal Composition:
The composition of metals in an alloy that go into solder
paste.
Metal Content:
The percentage weight of the solder alloy powder in solder
paste.
Metal-Core Boards:
Boards built with a metallic core and an organic or
inorganic insulation on either sides of the core. The core
could be made of steel, stainless steel, aluminum, copper,
or a laminate of metals (in most cases copper invar copper
or copper tungsten copper). The insulation of the core is
done prior to metallization.
Metering Rolls:
Successive rollers used to control the fabric to resin ratio
during the impregnation of resin onto glass fabric.
Micron:
One millionth of a meter, and another term for micrometer.
An easy conversion scheme is to remember that 25.4
microns=0.0254mm=0.001"=1 mil=1,000 microinches. With this
formula memorized, it is simple to translate between inch
and metric references.
Microstructure of Material:
Atomic structure of a material. In bonding applications,
refers to the effect of atomic structure on material
behavior during various steps in the excise, form, and
bonding processes.
Misalignment:
Misregistration of the centerline of the component lead with
respect to the centerline of the bonding pad on the
substrate.
Misregistration:
The lack of adequate dimensional conformity between two or
more patterns or features. Examples include misregistration
of a board with respect to a stencil or the misaligment
between layers of a printed circuit board.
Mold Flash:
Plastic debris remaining on a plastic molded package after
the component manufacturing process. This can occur on
molded carrier ring (MCR) and plastic quad pack (PQFP)
components.
Molded Carrier Ring (MCR) Component:
A packaging technique for ICs that utilizes a plastic molded
body and guard ring. MCR were developed to reduce damage to
leaded surface mount packages caused by normal handling. The
guard ring also acts as a common form factor for the
development of automation such as test, burn in, and excise
and form.
MTBF:
The statistical mean average time interval, usually in
hours, that may be expected between failures of an operating
unit. Results should be designated actual, predicted or
calculated.
Multichip Module:
A module capable of supporting several ICs in a single
package. Typically, multichip modules are based on ceramic,
contain high performance ICs with high pin count, and use
some form of advanced interconnect technology such as TAB,
COB,
or C-4. The parameters used to define a multichip module are
vague, but one basic criterion is a package that is no less
that 20% silicon, has no fewer that 100 I/O on a substrate,
and has no fewer that four layers.
Multilayer Board:
A PCB that uses more than two layers for conductor routing.
Plated via holes are used to connect the internal layers to
the outer layers.
Multilayer Ceramic:
A stack of alternating metallic and ceramic layers with vias
interconnecting them.
Multilayer Substrate:
Organic substrates composed of more than one laminate.
Cofired multilayer ceramic substrates are also referred to
as multilayer substrates.
Multiple Metal Layer Tape:
An advanced TAB tape that has more than one conductive
layer. This tape design is complex, including ground planes
and interconnections between conductive layers, and is only
used in select high performance applications.
Neutralizer:
An alkaline chemical added to water to improve its ability
to dissolve organic acid flux residues.
Nitto tape:
Tape that sliced silicon wafers are placed on prior to
dicing.
Nonactivated:
A natural or synthetic resin flux without activators.
Nonionic:
Refer to "nonpolar."
Nonpolar Solvent:
A solvent that is not electrically conductive and will
dissolve nonpolar compounds such as hydrocarbons and resins.
Nonpolar:
A condition in which a substance does not ionize in water.
Nonwetting:
A condition in which molten solder has contacted a surface,
but the solder has not adhered to all of the surface, and a
portion of the base metal may be exposed. Nonwetting occurs
when there is a barrier (intermetallic or oxide) between the
two joining surfaces.
- O -
Off-Contact:
A stencil printing method in which the printer is setup so
there is a space between the stencil and the substrate.
OLB Window:
An opening in TAB tape that the outer leads span. Typically,
this opening is where outer leads are excised from the tape.
Omegameter:
An instrument that measures ionic residues on PCB surfaces
via immersion of an assembly into a water-alcohol mixture of
a known high resistivity, after which a drop in resistivity
due to ionic residue over time is measured and recorded.
Open:
A complete break in a metal conductor path.
Open:
A condition in which solder fails to bridge the gap between
lead termination and the pad, resulting in a loss of
electrical continuity.
Organic PCB:
A printed circuit board made from organic material (epoxy,
polyimide, etc.).
Outer Lead Bonding:
The process of joining the leads of a component to the next
level of the assembly immediately following placement.
Commonly referred to as OLB. The bonding method can be
laser, hot gas, or hot bar.
Outer Lead:
The length of lead that extends across the OLB window. It is
typically excised, formed, and attached to a substrate.
Outgassing:
The gaseous emission or de-aeration from a PCB or solder
joint.
Over Molded Plastic Array Carrier (OMPAC™):
Motorola®'s trade name for plastic ball grid array
components (PBGA).
Oxide Content:
The amount of oxides present on the surface of solder
powder.
- P -
Packaging Density:
The quantity of components, interconnections, and mechanical
devices per unit volume.
Packaging Level:
The various members that comprise the packaging hierarchy,
such as chip, chip carrier, PCB, system, etc.
Pad:
A portion of the conductive pattern that is typically used
for the connection, and/or attachment of components. Also
called footprint or a land.
Passive Hold-Down:
The process of holding the component lead in contact with
the bonding pad by pressing on the body of the component
during the soldering process to ensure intimate contact
between the lead and bonding pad. Intimate contact is
important for proper heat transfer through the lead to
reflow the solder. This is commonly used in laser and hot
gas soldering.
PBGA:
Generic name for a BGA component constructed on organic
substrate material, such as FR-4, overmolded with plastic.
PCB:
The term generally used for printed circuit configurations
such as rigid or flexible, single, double, or multilayered
boards that are completely processed. A PCB or PWB is a
substrate of a glass fabric impregnated with a resin (ususally
epoxy) and cured and clad metal (almost always copper) upon
which a pattern of conductive traces is formed to
interconnect components.
PCMCIA:
Personal Computer Memory Card International Association.
This association was formed with the goal of promoting
interchangeability of IC cards among a variety of computer
and other electronic products. Both memory and peripheral
expansion (I/O) card types are defined by this standard. The
cards are all 85.6mm in length and 54mm in width with a
68-pin edge connector. There are three different formats for
different applications with thicknesses of 3.3mm, 5.0mm, and
10.5mm.
Peel Strength:
A true test of the adhesion between the lead and the bonding
pad after it has been soldered. This parameter is determined
by peeling the component lead off the bonding pad using
special fixturing on a pull tester.
Phenolic Resin:
as synthetic resin produced by the condensation of phenol
with an aldehyde (usually formaldehyde).
Photolithography:
The science of replicating complex circuitry onto the
surface of the specimen.
Pick-and-Place:
The assembly process in which components are selected and
placed onto specific locations of the PCB.
Pitch:
The center-to-center spacing between pads, rows of bumps,
pins, etc.
Placement:
The manual, semiautomatic, or automatic placement of a
component, device, or chip at its intended position at a
given packaging level.
Planarity:
Planarity refers to substrate surface flatness. It is
another term for board warpage.
Plasma Cleaning:
A cleaning process that uses electrically excited gas
molecules to remove surface contamination. Most commonly
found in applications where extreme cleanliness is required,
such as bonding pad preparation on the chip and substrate
for wire bonding.
Plastic Ball Grid Array:
Plastic Deformation:
With respect to materials science, the deformation of a
material resulting from it being stressed beyond its ability
to return to its original shape.
Plastic Leaded Chip Carrier (PLCC):
A component package with J-leads on all four sides.
Plated Through Hole (PTH):
A plated hole in a PCB used as an interconnection between
the top and bottom sides or the inner layers of a PCB. PTH
is intended to mount component leads in through hole
technology.
Plating Inconsistency:
Variance in overall lead plating thickness and
cross-sectional characteristics, which can cause lead form
variation during the lead forming process.
Polar Solvent:
A solvent with the ability to dissolve polar compounds such
as inorganic salts. However, polar solvents cannot dissolve
nonpolar compounds such as resins and hydrocarbons.
Polyimide:
A nonconductive polymer used as base material for two and
three layer
TAB tape.
Polyimides:
Thermosetting ring chain polymers characterized by -NH
group. They are being increasingly used as dielectrics in
high performance circuits.
Polymerize:
To chemically unite two or more polymers or monomers of the
same kind to form a molecule with higher molecular weight.
Polymerized Rosin:
Rosin that has reacted with itself during the course of a
soldering operation.
PPAP:
Production Part Approval Process defines generic
requirements for production part approval, including
production and bulk material. The purpose of PPAP is to
determine if all customer engineering design record and
specification requirements are properly understood by the
supplier and that the process has the potential to produce
product consistently meeting these requirements during an
actual production run at the quoted production rate.
PQP:
Product Quality Planning.
Preflow:
The period of time in the reflow profile after preheat and
before the reflow spike occurs. During this time, the
temperature of the metals being joined is allowed to
equalize.
Preheat:
A preliminary phase of a process during which the product is
heated at a predetermined rate from the ambient temperature
to a desired elevated temperature.
Preheating:
Increasing the temperature of a material above the ambient
temperature to reduce the thermal shock and influence the
dwell time during subsequent elevated temperature
processing.
Prepreg:
Partially-cured fiber-reinforced resin fabric. Also referred
to as the B-stage in the manufacturing of PCB.
Printed Circuit Board:
Printed Wiring Assembly:
Also called printed circuit assembly, this term is used for
a printed wiring board in which all the individual
components have been completely attached.
Printed Wiring Board:
Probe:
A rigid, pointed, metallic, wire-shaped device used for
making electrical contact to a circuit pad for electrical
test purposes.
Profile:
A graphical representation of the time versus temperature of
a continuous furnace or oven cycle.
Pseudoplastic:
A fluid that displays a decrease in viscosity with an
increase in the shear rate.
Pull Strength:
A measure of the quality of a solder joint formed between a
component lead and a bonding pad on a substrate. This
parameter is typically determined by placing a hook under
the shoulder of a lead and pulling up.
Quad Flat Pack (QFP):
A ceramic or a plastic chip carrier in which the leads
project down and away from all four sides of a square
package.
- R -
Radiation:
The combined process of emission, transmission, and
absorption of thermal energy between bodies separated by an
empty space.
Reflow Soldering:
A process for joining surface mount parts into a solder
paste for permanent interconnection via passage through
various stages including preheat, stabilization/drying,
reflow spike and cooldown.
Reflow:
The application of heat to a surface containing a thin
deposit of a low melting point metal or alloy (e.g., solder
paste tin lead alloy), resulting in the melting of the
deposit, followed by its solidification.
Reliability:
The continued conformance of a device or system to a
specification over an extended period of time.
Repair:
An operation that restores a part or assembly to a condition
in which it can be used.
Repeatability:
The ability of a process to accurately return to a specific
target. A designation for evaluating process equipment and
consistency.
Residues:
Contaminants left behind on the surface of the substrate or
the PCB as a consequence of both preassembly and assembly
operations.
Resin Flux:
A resin and small amounts of organic activators in an
organic solvent.
Resin Impregnation:
The process of coating a glass fabric by resin using
metering rolls to control the fabric to resin ratio.
Resin:
An organic polymer which, when mixed with a curing agent,
crosslinks to form a thermosetting plastic.
Resistance:
The property of a material to oppose the flow of current.
Rework:
A manufacturing operation that restores a part or an
assembly to an operable condition. The reworked
part/assembly should meet or surpass specifications.
Rheology:
The study of the change in the form and flow of matter,
embracing elasticity, viscosity, and plasticity.
Rolled Annealed Copper:
A type of copper used in manufacturing TAB tape. The copper
is passed through a series of rollers to achieve a desired
thickness, typically 1 ounce or 1.4 mils thick, and then
annealed to remove the internal stresses created by the
rolling process.
Rosin Flux:
Rosin in an organic solvent or rosin as a paste with
activators.
Rosin:
A hard, natural resin, consisting of abietic acid and
pimaric acids and their isomers, some fatty acids, and
terepene hydrocarbons. Resin is extracted from pine trees
and subsequently refined.
Saponifier:
An alkaline chemical added to water to improve its ability
to dissolve rosin flux residues.
Screen Printing:
The transfer of a pattern onto a surface by forcing a
suitable material through a screen with a squeegee.
Self-Alignment:
The tendency of certain slightly misaligned components
(during placement) to self-align with respect to their land
patterns during reflow soldering. It occurs due to the
surface tension of molten solder.
Self-Planarizing Head:
A mechanism integrated into the head of an outer lead bonder
that allows the bottom surface of the thermode blades to
adjust to the plane defined by the surface of the substrate.
Shadowing:
The failure of molten solder to wet the leads of surface
mount components due to their location on the board during
wave soldering or the cause for insufficient heating of
surface mount components due to their location on the board
during infrared reflow soldering.
Shear Strength:
The force required to shear apart adhesive-bonded and cured
materials and/or components.
Shipping Tube:
In reference to molded carrier ring or TAB components in
slide carriers, it is the tube in which components are
vertically stacked for shipping and feeding into excise and
form feeders.
Short:
An unwanted connection between conductor paths.
Silver chromate test:
A qualitative check for the presence of ionic halides in RMA
fluxes.
Single Layer TAB Tape:
Tape constructed with a single conductive metal layer,
typically 70 micron thick copper. This type of tape is
generally used in low lead count applications, and is not
commonly seen.
Single-Layer Board:
A printed circuit board that contains metallized conductors
on one side of the board only.
Slide Carrier:
A carrier for handling singulated TAB components. The slide
carrier looks and functions similarly to the outer ring of a
molded carrier ring component. It serves to facilitate
component test, burn-in, and mechanical registration in a
set of tooling. Slide carriers come in three basic sizes,
35mm, 48mm, and 70mm.
Slump:
A spreading of material (solder paste, adhesive,thick film,
etc.) after stencil printing (or dispence) but before
curing.
Small Outline Integrated Circuit (SOIC):
An integrated circuit surface mount package with two
parallel rows of gull-wing leads.
Small Outline J-Leaded (SOJ):
An integrated circuit surface mount package with two
parallel rows of J-leads.
Small Outline Transistor (SOT):
Discrete surface mount transistors with a molded plastic
outline that serve small and medium power applications.
Snapback:
The return of a stencil to normal (flat plane) after its
deflection by a squeegee across its surface.
Solder Balls:
Small spheres of solder adhering to the laminate, mask, or
conductor surfaces usually after wave or reflow soldering.
Solder Bridging:
Solder paste or solder on two or more adjacent pads that
come into contact to form a conductive path (forming a
bridge).
Solder Bumps:
Round solder balls bonded to the pads of components and
subsequently used for face-down bonding techniques.
Solder Connection:
The joining of two or more metal parts by means of an
electrical or mechanical connection.
Solder Mask:
A dielectric material used to cover the entire surface
(except where the joints are to be formed) of the PCB
primarily to protect the circuitry from environmental
damage. Solder mask also helps to reduce bridging.
Solder Paste:
A homogenous and kinetically stable mixture of minute
spherical solder particles, flux, solvents and binder that
is screen printed onto the printed circuit board and then
reflowed to form the solder joints.
Solder Powder:
The solder alloy in solder paste exists in the form of
powder. Solder powder is the major ingredient that affects
the printability of the paste and the quality of the solder
joint.
Solder Thickness:
The amount of solder deposited on a pad for reflow. Optimum
thickness will vary with pad size and pitch, but must be
consistent across a single bonding site.
Solder Wicking:
The capillary movement of molten solder onto a pad or
component lead or between metal surfaces, such as strands of
wire.
Solder:
A low melting point alloy, usually of lead (Pb) and tin (Sn),
that can wet copper, conduct current, and mechanically join
conductors.
Solderability:
The ability of a conductor to be wetted by solder and to
form a strong bond with the solder.
Soldering:
A process of joining metallic surfaces with solder, without
melting the base material.
Solids Content:
The metal powder content as a percentage of the mass of the
wet solder paste, or the percentage by weight of rosin in a
flux formulation.
Solvent Cleaning:
A cleaning method employing chlorinated and fluorinated
hydrocarbon liquids.
Solvent Extraction:
The removal of one or more components from a liquid mixture
by intimate contact with a secondary liquid that is nearly
insoluble in the first liquid and which dissolves the
impurities and not the substance to be purified.
Solvent:
A solution capable of dissolving a solute.
SPC:
The use of statistical techniques to analyze the outputs of
processes with the results guiding actions taken to adjust
and/or maintain a state of quality control.
Specific Heat:
The ratio of a material's thermal capacity to that of water
at 15ºC.
Spherically Compliant Suspension:
A patented mechanism based on a four-bar linkage that can be
integrated into an outer lead bonder to have
self-planarization of the thermode head to the substrate.
This mechanism has been developed and patented by Universal
Instruments Corporation.
Splice:
A strip of material used to join two pieces of tape. Splices
are used to connect strips of
TAB tape
when handled in continuous tape format.
Spread:
The distance a substance (e.g., an adhesive) moves after it
has been applied at ambient conditions.
Sprocket Holes:
Holes along both edges of
TAB tape
used for handling, indexing, and in some cases,
registration.
Sprocket Pitch:
The center to center distance of two adjacent sprocket
holes.
Squeegee:
A rubber or metal blade used in printing to wipe solder
paste (or glue) across the stencil's face, forcing the
material through the patterned apertures and onto the PCB.
Static Flex:
Flex circuits that are bent during installation, but do not
undergo any further movement in an assembly.
Statistical process control:
Stencil Printing:
Deposition of a specific material, such as solder paste,
using a stencil.
Stencil:
A metal mask in which patterns or apertures matching the
component locations on the PCB are made so a suitable
material can be forced through the apertures by a squeegee
onto a substrate. Common materials are stainless steel and
brass.
Storage life:
The period that an adhesive can be stored and remain viable
for use.
Stress Corrosion:
The gradual deterioration of the mechanical properties of a
material, usually accompanied by crack propagation, and
caused by the acceleration of applied stress. This
phenomenon usually occurs under high humidity conditions.
Substrate Geometry:
Substrate dimensions, typically dimensions critical to
implement a successful bonding process, including the
following: board size, bonding pad layout and dimensions,
solder thickness, adjacent components, planarity, fiducial
shape and dimensions, and board thickness and construction.
Surface Insulation Resistance (SIR):
The electrical resistance of an insulating material between
a pair of contacts or conductors. SIR is determined under
specified environmental and electrical conditions.
Surface Mount Device (SMD):
An active or passive device designed to be soldered to the
surface of the printed circuit board.
Surface Mount Technology (SMT):
A method of assembling printed circuit boards where the
components are mounted onto the surface of the board rather
than being inserted into holes in the board.
Surface Tension:
An effect of the forces of attraction between the molecules
on the surface of a liquid. Surface tension is the reason
water beads up better on the hood of your car when waxed
versus unwaxed. The wax increases the surface tension of the
water, and thus it beads up more readily.
Surfactant:
A chemical added to any substance to lower its surface
tension.
Surftape:
A punched carrier for tape and reel packaging of surface
mount devices. It features a flexible, pressure-sensitive
adhesive base, negating the need for cover tape.
Suspension Brake:
A pneumatic clamp on the spherically compliant suspension
which can be used to lock the head in a given orientation.
Syringe:
A container for adhesive dispensing via its narrow opening.
- T -
TAB:
Tape Automatic Bonding. The process where silicon chips are
joined to patterned metal traces (leads) on polymer tape to
form inner leads bonds and subsequently the leads are
attached to the next level of the assembly, typically a
substrate or board, to form outer lead bonds. TAB is the
technique of interconnecting silicon with beam bonding as
opposed to wire bonding.
TAB Component:
An IC mounted on a TAB site.
TAB Tape Site or TAB Frame:
An individual component mounting site on
TAB tape.
TAB Tape:
A polymer film with patterned metal traces or leads. It is
only a temporary support that is almost completely removed
during the transfer of the chip from the tape to the
substrate. The TAB tape can be handled in continuous tape or
slide carrier format.
Tackiness:
The ability of solder paste to hold surface mount components
in place after placement but before reflow soldering.
Tape-and-reel:
Component packaging for placement via housing parts in
cavities in a continuous strip. The cavities are covered by
a plastic tape so that they can be wound in a reel for
presentation to a component placement machine.
Tape Automated Bonding:
Tape Bonding:
Utilization of a metal or plastic tape material as a support
to a carrier of a component in a gang bonding process.
Tape Ball Grid Array (TBGA):
A BGA package on a copper polyimide base like
TAB,
except TAB leads are replaced by an area array ball grid for
interconnects. A stiffener is added to ensure flatness for
the mass reflow assembly process.
Tear Strength:
Force required to initiate or continue a tear in a material
under specified conditions.
Tensile Strength:
The longitudinal stress required to break a prescribed
specimen divided by the original cross-sectional area at the
point of rupture (usually expressed in lbs. per square inch
or PSI).
Terminal:
A metallic device used for making electrical connections.
Test Board:
A printed circuit board deemed to be suitable for
determining the acceptability of a group of boards produced
with the same fabrication process.
Test Fixture:
A device that interfaces between test equipment and the unit
being tested.
Test Pads:
Contact points on TAB tape, located outside the OLB window,
that are used to facilitate testing and burn-in of the IC
while it is in the TAB frame. Test pads remain with the
discarded portion of the carrier after excising.
Test Pattern:
A pattern used for inspecting or testing purposes.
Test Point:
A specific point of access to an electrical circuit used for
electrical testing purposes.
Thermal Conductivity:
The property of a material that describes the rate at which
heat will be conducted through a unit area of the material
for a given period of time.
Thermal Cycling:
A method used to induce stresses on electrical components by
means of sequential heating and cooling in an oven. It is
used in accelerated reliability testing.
Thermal Profile:
A time versus temperature graph that displays the
temperatures an assembly is subjected to over time in an
oven during processes such as reflow soldering or the curing
of adhesives, encapsulants, and conformal coatings.
Thermocompression Bonding:
The joining of two materials without an intermediate
material by the application of pressure and heat in the
absence of electrical current.
Thermocouple:
A sensor made of two dissimilar metals which, when heated,
generate a small DC voltage used in temperature
measurements.
Thermode:
A set of blades or bars that are pulse-heated. A thermode is
used to hold component leads in place and reflow solder them
to bonding pads on a substrate during hot bar reflow
soldering.
Thermoplastic:
Polymer materials that can be repeatedly melted without
significant change in their properties.
Thermosetting Plastic:
Polymer materials that cure (irreversably polymerize) at
specific temperature and time conditions.
Thixotropic Ratio:
An indication of thixotropy as a ratio of viscosities at two
different shear rates.
Thombstoning:
A soldering defect in which a chip component is pulled into
a vertical position leaving one side unsoldered.
Three Layer TAB Tape:
Tape constructed with a conductive metal layer, typically 35
micron thick copper; a flexible heat resistant support
layer, typically 125 micron thick polyimide; and an adhesive
layer between the conductive layer and the flexible support
layer. The polyimide thickness is not limited in the three
layer tape manufacturing process because the openings in the
tape are punched out rather than etched. The copper is
usually tin or gold plated.
Threshold Limit Value:
A guideline for the exposure of humans to solvents; it is
expressed as a Time Weighted Average (TWA) of the parts per
million of vapor in air.
Through Hole:
A hole connecting the two surfaces of a printed circuit
structure.
Tie Bars:
Polyimide strips, or bars, connecting an inner ring at its
corners to the remainder of the
TAB tape
site. Also referred to as suspenders.
Tinning:
The process of coating metallic surfaces with a thin layer
of solder.
Tip-to-Tip Dimension:
With respect to component geometry, the distance between the
ends of the leads on opposite sides of a component after
excising and forming.
Tombstoning:
The lifting of one end of a passive surface mount component
during solder reflow caused by surface tension and
unbalanced forces of solder wetting.
Torsional Strength:
The torque required to separate adhesive bonded (and cured)
materials and/or components.
Touch-Up:
The identification and elimination of defects in a product.
Transistor:
An active semiconductor device capable of providing power
amplification. Transistors have three or more terminals.
Two Layer TAB Tape:
This tape is constructed with a conductive metal layer,
typically 35 micron thick copper, and a flexible heat
resistant support layer, typically 50 micron thick
polyimide. The support layer thickness is limited to 50
microns or less due to chemical etching limitations of the
two layer TAB tape manufacturing process. The copper is
usually tin or gold plated.
Type I Assembly:
A surface mount assembly with surface mount components on
one or both sides of the substrate.
Type II Assembly:
A surface mount assembly with surface mount components on
one or both sides of the substrate and through hole devices
on the primary side.
Type III Assembly:
A surface mount assembly with surface mount components on
the secondary side of a PCB and through hole devices on the
primary side.
Ultra-fine-pitch:
Center-to-center lead distances and conductor spacings of
0.010" or less.
Ultrasonic Cleaning:
The use of ultrasonic energy along with a chemical solvent
to clean a component or a PCB assembly immersed in solvent.
Mechanical oscillation is introduced by the ultrasonic
energy to facilitate cleaning.
Underfill:
In flip chip applications, the material injected under the
die after testing to ensure reliability. This material is
particularly important for flip chips mounted on substrates
with different CTEs than silicon, such as FR-4 and some
ceramics.
- V -
Vapor Phase Reflow:
A solder reflow technique in which the solder joints are
heated by the condensation of an inert vapor.
Vehicle System:
The vehicle dissolves flux and imparts paste-like
characteristics to solder paste.
Vias:
Drilled holes in laminate that interconnect different layers
of circuitry. Vias can be used for electrical connections or
thermal dissipation.
Void:
A cavity inside the solder joint formed by gases released
during reflow or by flux residues entrapped before
solidification.
- W -
Waffle Pack:
A matrix tray for holding bare die. Typically, waffle packs
are 2" x 2" or 4" x 4." The pockets for die in waffle packs
are typically designed for specific die sizes; they are not
standardized.
Wave Cleaning:
Cleaning a PCB by passing it through a wave of solvents
(similar to the concept used in a wave fluxer or a wave
soldering process).
Wave Soldering:
A process in which many potential solder joints are brought
in contact with a wave of molten solder for a short period
of time and are soldered simultaneously.
Wetting Balance:
An instrument used to measure wetting forces, and
consequently, estimate solderability.
Wetting:
The spreading of solder along the leads and pad to produce
complete and uniform solder coverage.
Whisker:
A metallic growth, needle-like in size, that appears on the
surface of a PCB.
Wire Bonding:
The use of fine wires to connect semiconductor packages to
the next level of packaging. Wires are composed of gold or
aluminum.
- X -
X-ray: is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by bombarding with high-energy X-rays or gamma rays.
- Y -
Yield:
The ratio of usable parts at the end of a manufacturing
process to the number of components submitted for
processing.
