Thermal Solutions from Smart to Finish
   contact us  |  (603) 635-2800    |     Linkedin   Twitter   YouTube

Glossary of Terms

The terms as defined below cross many scientific and engineering boundaries relating to heat transfer, die casting, and mechanical industries. As such, the terms are generalized and not meant to be inclusive of all possible variations of that definition within a particular industry.

Accelerator: an organic compound which is added to an epoxy resin to shorten the curing time.

Adhesion: the state at which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking action or both.

Adhesive: a substance which applied as an intermediate is capable of holding material together by surface attachment.

Ambient temperature: the average temperature of the surrounding air or other medium comes in contact with the equipment or instruments under test.

Anodizing: to subject a metal to electrolytic action as the anode of a cell in order to coat with a decorative or protective film.

Application Specific Integrated Circuit (ASIC): an integrated circuit chip with personalization customized for a specific product. Personalization refers to the integrated circuit chip.

Array: a group of elements (pads, pins) or circuits arranged in rows or columns on one substrate.

ASIC: Application Specific Integrated Circuit

Back Panel: a planar package components holding plugged in lower level package components as well as discreet wires and cables interconnecting these components.

Braze: a joint formed between two different materials by formation of liquid at the interface.

Ceramic: inorganic nonmetallic materials such as alumina, beryllia, or glass ceramic, whose final characteristics are produced by subjection to high temperatures. Often used in forming ceramic substrates for packing semiconductor chips.

CFM: the volumetric flow of liquid or gas in cubic feet per minute.

Chemical Treatment: the process of treating a clean surface by chemical means. The chemical nature of the substance is altered to make it highly receptive to adhesion

Chip: the uncased and normally leadless form of an electronic component part, either passive or active, discreet or integrated. Also referred to as die.

Chip Carrier: a special type of enclosure or package to house a semiconductor device. It has electrical terminations around it’s perimeter, or solder pads on its underside, rather than an extended lead frame of plug-in pins.

Chromate: a conversion coating consisting of trivalent and hexavalent chromium compounds.

Coefficient of Thermal Expansion (CTE): the ratio of change in dimensions to the change in temperature per unit starting length, usually expressed in cm/cm˚C

Conduction: thermal transmission to heat energy from a hotter region to a cooler region in a thermal medium

Conductive Adhesive: adhesive material, usually epoxy, which has metal powder added to increase electrical conductivity. Usual conductor added is silver.

Convection: transmission of a thermal energy from a hotter to a cooler region through a moving medium, such as air or water.

CDFP: Ceramic Quad Flat Pac

Cure Time: the interval of time from start of reaction to the time at which specified properties of reacting thermosetting or rubber composition is reached. For materials which react under the conditions of mixing, the start of the reaction is the time of initial exposure to the conditions necessary for reaction to occur

Curing Agent: an inorganic or organic compound that initiates the polymerization of a resin

Custom Design: a form of design in which the choice and arrangement of components and wiring on a package may vary arbitrarily within tolerances from a regular array

Die Casting: a process in which molten metal is injected at a high velocity and pressure into a mold (die) cavity

Dual In-Line Package (DIP): a package having two rows of lead extending at right angles from the base and having standard pin spacings between rows and between rows of leads

EMI: Electromagnetic interference

Emissivity: the ratio of energy emitted by an object to the energy emitted by a black body of the same temperature. The emissivity of an object depends on its material and surface texture; a polished metal surface can have an emissivity of around 0.2 and a piece of wood around 0.95

Endothermic: absorbs heat

Error: the difference between the correct or desired value and the actual reading on the value taken

Exothermic: gives off or releases heat

External Resistance: a term used to represent thermal resistance from a convenient point on the outside surface of an electronic package to an ambient reference point

Flat Pac: an integrated circuit pack having its leads extending from all four sides and parallel to its base

FPM: flow velocity in feet per minute

Gate Array: a semicustom product, implemented from a fully diffused or ion-implanted semiconductor wafer carrying a matrix of identical primary cells arranged into columns with routing channels between them in the X and Y directions

GPM: volumetric flow rate in gallons per minute

Hardener (Curing Agent): a substance or mixture of substances added to an adhesive to promote or control the curing reaction by taking part in it

Heat: thermal energy

Heat Flux: the rate of flow of heat energy across or through a surface, measured in watts/cm2

Heat Sink: a heat transfer component to which electronic components or their substrate or their package bottom are attached. This is usually a heat conductive metal with the ability to rapidly transmit heat from the generating source

Heat Transfer: the process of thermal energy floating from a body of high temperature to a body of low temperature. Means of transfer are conduction, convection, and radiation.

Injection: the act of forcing molten metal into a die

Integrated Circuit: a microcircuit consisting of interconnected elements inseparably associated and formed in situ or with a single substrate to perform and electronic function.

Interface: the boundary of dissimilar materials, such as between a film or a substrate, or between two films.

Internal Resistance: a term used to represent thermal resistance from the junction of a device, inside an electronic package to a convenient point on the outside surface of the package (RINT)

Iridite: solution to application for base metal to produce corrosion resistant finish

Leadless Chip Carrier (LCC): a surface mounted package having metalized contacts in its periphery (rather than wire leads) which are soldered to metalized contracts on the printed circuit board or substrate

Maximum Operating Temperature: the maximum temperature at which a heater, sensor, device, or instrument can be safely operated.

Multichip Module (MCM): a module or package capable supporting several chips on a single package

NIST: National Institute of Standards and Testing

O.D.: Outside diameter

Peel Strength (Peel Test): a measure of adhesion between the conductor and the substrate. The test is performed by pulling or peeling the conductor off the substrate and observing the forces required

Pick and Place: the manufacturing process whereby chips are selected and placed on the correct substrate site in preparation for joining (or interconnecting) the chip to the substrate

Pin-Grid Array (PGA): a package or interconnect scheme featuring a multiplicity of plug-in type electrical terminals arranged in a pre-described matrix format or array.

PQFP: Plastic Quad Flat Pac

Pressure Sensitive Adhesive: attachment of materials by a means of a sustained force at the desired contact area through use of an adhesive

Protection Head: an enclosure usually made out of metal at the end of a heater or probe where connections are made

PSIA: Pounds per square inch absolute. Pressure referenced to vacuum

PSIG: Pounds per square inch gage. Pressure referenced to air pressure

Radiation: the combined process of emission, transmission, and absorption of thermal energy between bodies separated by empty space.

Reliability: the probability of survival of a component, or assembly, for the expected period of use

Resin: a term used for an organic polymer that when mixed with a curing agent crosslinks to form a thermosetting process

Resistance: the property of a conductor that opposes the flow of current by dissipating energy as heat. In packages, it causes voltage and current loss in signal and power distribution systems

SCR: Silicon Controlled Rectifier

Shrinkage: the decrease in volume or contraction of a material by the escape of any volatile substance, or by a chemical or physical change in a material

Solvent Cleaner: the process of removing soil from a substrate surface with an organic solvent. The solvent cleaning process does not alter the substrate physically or chemically

Specific Heat: the ratio of thermal energy required to raise the temperature of a body 1˚ to the thermal energy required to raise an equal mass of water 1˚.

Storage Life: the period of time during which a packaged adhesive can be stored under specific temperature conditions and remain suitable for use. Often called “shelf life”.

Surface Mount Technology (SMT): a method of assembling hybrid circuits and printed wiring boards where component parts are mounted onto, or rather into, the printed wiring board, as in the mounting of components on substrates in hybrid technologies.

Tack (Green Strength): the property of an adhesive that enables it to form a bond of measurable strength after adhesive and adherend are brought into contact under little or no pressure

Tape Automated Bonding (TAB): a process where silicon chips are joined to patterned metal or polymer tape using the thermocompression bonding, and subsequently attached to a substrate or board by outer lead bonding. Intermediate processing may be carried out in strip form through operations such as testing, encapsulation, bum-in, and excising the individual packages from the tape.

TCE: temperature coefficient of expansion

Temperature Curing: the temperature at which adhesive or assembly is subject to curing

Temperature Cycling: an environmental test where the film circuit is subjected to several temperature changes from a low temperature to a high temperature over a period of time

Thermal Conductivity: a measure of material’s ability to conduct heat; physical constant for quantity of heat that passes through unit volume of a substance in unit of time when difference of temperature of two opposite faces of unity.

Thermal Cycling: a method to impose cyclical stress on an assembly of microelectronic components by alternately heating and cooling in an oven. It is used for accelerated reliability testing of assemblies.

Thermal Expansion: an increase in size due to an increase in temperature expressed in units of an increase in length or increase in size per degree

Thermal Gradient: the plot of temperature variances across the bulk thickness of a material being heated

Thermal Mismatch: difference in thermal coefficients of expansion of materials which are bonded together

Thermal Resistance (˚C/W): the opposition offered by a medium to the passage through it of thermal energy

Thermocouple: the junction of two dissimilar metals which has a voltage output proportional to the difference in temperature between the hot junction and lead wires

Thermoset: material that will undergo or has undergone a chemical reaction by the action of heat, catalyst, ultraviolet light, etc., leading to a relatively infusible state

Transistor Outline (TO): industry standard packaging designation established by JEDEC of the EIA

Trim Die: die for shearing or shaving flash from a casting. Either die is forced over the casting, or the casting is forced through the die

Viscosity: a measure of the resistance of fluid to flow or the internal friction within the body or fluid

Working Life: the period of time during which a liquid resin or adhesive, after mixing with a catalyst, solvent, or other compounding ingredients remains usable. Also known as “pot life”.

Zero-Insertion-Force Connection (ZIF): a form of connector that allows the connector pins to be brought together under very low force, then wiped and pressed together during cam activation. Low insertion force is LIF.