tance.
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.
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 metal formed by combining two or more other metals. Analog Circuit: An electrical circuit that provides a continuous relationship
between its input and output.
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.
Aqueous Cleaning: A cleaning technique that uses water as the primary
cleaning fluid.
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 or circuits arranged in rows and columns on a
substrate.
Assembly: A group of components physically joined to a PCB or ceramic board.
Automated Test Equipment: 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.
B-Stage PCB: Refer to "prepreg."
Ball Grid Array (BGA): A leadless surface-mountable package in which solder
ball interconnects cover the bottom surface of the package in a checkboard
fashion. BGAs are reflow soldered to PCBs using a mass reflow process.
Bare Board: An unpopulated PCB.
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. Board: An organic printed circuit card or board on which smaller components,
cards, or modules can be mounted.
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.
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.
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."
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.
Ceramic Ball Grid Array (CBGA): A ball grid array package with a ceramic
substrate.
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-on-Board (COB): A configuration in which a chip is directly attached to a
printed circuit board or substrate by solder or conductive adhesives.
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. 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.
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.
Comb Pattern: A set of comb-like arrays of uniformly spaced conductors.
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.
Component: An individual functional element in a physically independent body
(e.g., resistor, capacitor, or transistor).
Conduction: The thermal transmission of heat energy from a hotter region to a
cooler region in the presence of a conducting medium.
Conductive Adhesive: Refer to "isotropic/anisotropic conductive adhesives."
Conductor, Electrical: A class of materials-ususally metals-that easily conducts
electricity. Examples include silver, copper, gold, and super-conducting ceramics.
Conductor, Thermal: A class of materials-ususally metals-that easily conduct
heat. Examples include copper,