GLOSSARY OF TERMS USED IN SOLDERING

This glossary is intended to give a brief explanation/definition of a term/acronym that may be used in electronics manufacturing.

Activator



ANSI

AOI


ASIC

ASTM

Automated Test Equipment


Ball Grid Array


Bridging


Bumped circuit boards


CFC

Chip carrier


Chip component




Chip on board


CMOS

CSP

Component

Component lead


Contact angle


Copper mirror test

CTE see TCE

Dewetting


DFM

DFT

DIL

DIP

Double sided assembly

ESD



Eutectic



Fillet

Fine pitch


Flatpack



Flip chip attach


Flux



Flux classification



Flux residue

Footprint

FR4


Gull wing lead




Icicle

In circuit test


Infra red (IR)






Integrated circuit (IC)


Intermetallic layer


IPC



J lead


J Standard


Land


LCCC

Leaching



Lead configuration


Lead-free


Lead pitch

Legend


Liquidus

Low temperature alloy


MELF


Melting point



Metallisation


Mid-chip beads


Multilayer

MLCC

Pad

PCA, PCB, PWA, PWB

PLCC


Popcorning

Populate

Preheat



Print head

PTH

Quadpack (QFC)

Reflow soldering



Repair


Residue



Resist


Rework


Rheology



Rosin







Rosin activated (RA)

Rosin mildly activated (RMA)

Saponifier



Shadowing




Silk screen




SMA

SMC


SMD


SMT




Snap off distance


SO


SOIC

Solder





Solder balls



Solder beads

Solder bridge


Solder mask


Solder paste


Solderability


Soldering


Solidus

Solvent

SOT



Squeegee


Stencil


SIR

Surfactant


TAB

TCE

Termination

Thermal cycling


Thixotropy



Tinning


Tin whiskers



Tombstoning




Vapour phase reflow

Via


Viscosity



Void

Water Soluble paste


Wettability


Wetting
An addition to solder paste to promote cleaning of oxidised conductor pads during the solder reflow operation and thereby improve the quality of solder joints

American National Standards Institute

Automated Optical Inspection. Test fixture whereby printed-circuit boards are automatically inspected. The boards may be bare or populated

Application Specific Integrated Circuit

American Society for Testing and Materials

ATE. Equipment that automatically analyses functional characteristics for board degradation/fault isolation

BGA. A component with solder ball shaped terminations on the bottom of the package arranged in a grid pattern

Excess solder deposit or icicles leading to a connection made between adjacent legs of a component or conductor tracks

Printed circuit boards with conductor pads soldered prior to component addition

Chlorinated fluorocarbon

A low profile, surface mount, component package housing an integrated circuit with external connections on all four sides of the package

Small, surface mounted component. The numbering system refers to the size of the component, eg a 0403 device is 0.04” (1mm) x 0.03” (0.75mm). The term is normally used of passive components (resistors, inductors, capacitors) but sometimes integrated circuits (ICs) are called chip components

COB. Bare silicon integrated circuit chips mounted on to the substrate with connections made by wire bonds or by flip chip attach

Complementary Metal Oxide Semiconductor

Chip Scale Package. It is no larger than 125% the size of the integrated circuit

An active or passive device that is added to a board to provide functionality

The conductor that extends from a component package and serves as an electrical connection

The angle that the solder fillet makes with the conductor pad. Contact angles in excess of 90º are unacceptable

A method for testing the corrosion of the flux in solder pastes

Coefficient of thermal expansion measured in ppm/ºC

An undesirable state that is a result of molten solder coating a surface but then receding leaving some areas covered by solder and others not

Design for Manufacturability

Design for Test

Dual in Line. Component with two parallel rows of connections

Dual in line package for semiconductors

Components on both the front and rear sides of a board

Electrostatic Discharge. A transfer of electrostatic charge that damages semiconductors. ESD protection is necessary when handling integrated circuits

The alloy of metals that has a lower melting point than any of its constituents. Eutectics melt to form a liquid without exhibiting an intermediary solid/liquid mix

The solder connected to both the component lead and pad

Different definitions. Less than 1.27mm (0.050”); more commonly 0.635mm (0.025”) and under. Others say between 0.4 and 0.8mm

A thin plastic, square surface mount chip package that contains connecting leads (pins) on all four sides that extend straight outward. The leads are bent and cut for the specific application

FCA. The attachment of a bare integrated circuit to a substrate using solder bumps between chip and substrate

A chemical composition applied to a surface to be joined by welding, soldering, or brazing to facilitate the wetting of solder and prevent the formation of/remove oxides. In solder pastes the flux is an integral part of the paste

There are four broad categories of fluxes - rosin (RO), resin (RE), organic (OR) and inorganic (IN) - in J-STD-004, a popular flux classification system from the IPC and EIA

See residue

The surface space occupied by the lead of an electronic component

Commonly used epoxy/fibre glass material for printed circuit boards. FR stands for Flame Retardant

A lead on a chip package that is formed with two opposing 90º bends such that the lead at its foot runs parallel with the part of the lead that extends from the package. Gull-wing leads are used on surface mount chips such as QFPs and SOICs

Solder that protrudes out of a solder joint

An electrical test of an assembly in which each component is tested individually, even though there are many components soldered to the board

The band of electromagnetic wavelengths existing between the extreme of the visible part of the electromagnetic spectrum and the shortest microwaves. There are three recognised bands IR-A: 700 nm–1400 nm IR-B: 1400 nm–3000 nm IR-C: 3000 nm–1 mm. The strong absorption of infrared by many substances (especially black bodies) renders it a useful means of applying heat energy

A small, complete circuit usually made on silicon. Can be used bare or packaged as part of an assembled board

An intermediary alloy formed between the solder and the conductor pad that is often brittle

The Institute for Packaging and Connection is a body that has developed a set of international and industry recognised standards to ensure conformity and quality of soldering in electronics assemblies

A lead on a chip package that is formed to resemble the letter ‘J’ when looked at in cross-section

J-STD-00X, Joint Industry Standard, ‘Requirements for Soldered Electrical and Electronic Assemblies’, was first published in January 1992

The area of a conductor track where the component is attached - also called pads (see Pad)

Leadless ceramic chip carrier

The dissolution of conductor material into molten solder during the soldering process which in worst cases results in the complete removal/disappearance of the conductor pad

The shape of the lead that extends from a component and that is formed to give the desired arrangement (J lead, gull wing, etc)

The absence of the element lead (Pb) in solder pastes in particular. It does not mean zero component pins on chip packages!!

The distance between the centres of leads on a component

A mark or notation printed onto the circuit board to identify component locations for ease of assembly/rework. A legend is normally in an alphanumeric format

Temperature above which a non-eutectic alloy is completely molten

Solder alloy that melts at a low temperature: The tin/bismuth alloy, 42Sn/58Bi, melts at 138ºC

Stands for metal electrode leadless face and is a component type that is cylindrical (capacitors)

Temperature at which a solid becomes a liquid. Some solder alloys are not eutectic (see definition) and have an intermediary solid/liquid mix before becoming completely molten

A metal deposited onto substrates and component leads to facilitate electrical connection

Large balls of solder embedded in a pool of flux and located next to components somewhere near their centre

A circuit board composed of many conductor layers or levels and joined by vias

Multilayer chip capacitor

Part of a conductor track that is used for connecting to a component

The board and the assembly

Plastic leaded chip carrier. The plastic refers to the packaging material and not to the leads (plastic instead of ceramic)!!

Moisture induced cracking of plastic packages during reflow soldering

The act of attaching components to a PCB or substrate

Printed circuits boards are raised to a temperature of about 150ºC prior to the reflow operation. In practice both preheat and reflow are parts of the same temperature profile

The part of the screen printer which houses the squeegee

Plated through hole

Package with leads on all four sides

The passage of a populated printed circuit board through a heated tunnel to melt the solder paste deposit and form solder joints between the components and the board

Normally refers to bare printed circuit boards that are made to function (see rework which applies to populated pcbs)

Resinous remains from the solder paste once it has done its work. It may be necessary to remove this immediately after the solder process to assist functionality/testing of completed printed circuit boards

Sometimes known as solder resist or solder mask as a coating of this material prevents solder reaching underlying conductors

This process normally involves de-soldering and re-soldering in order to make defective, populated, printed circuit boards function correctly

The flow characteristics of any paste especially under stress induced by printing and described by terms like thixotropic, viscous, etc. rather than given a numerical value

Rosin fluxes contain abietic acid, a chemical extracted from pine tree sap. Type R fluxes are the least active of the rosin-based products. They are designed for use with very clean surfaces. RA fluxes are the most active rosin fluxes but they leave the most residues. RMA fluxes contain a small amount of an additional activator, typically a halide, which assists by the removal of oxides from surfaces to be soldered. These fluxes leave small amounts of an inert residue that is usually non-corrosive and tack-free

See above

See above

An alkaline chemical added to water to improve its ability to dissolve non-water soluble rosin flux residues. Taken literally the word means to convert into soap!!

A condition in which component bodies block radiated infrared energy from striking certain areas of the board directly. Shadowed areas receive less energy than their surroundings and may not reach desired temperatures resulting in failure of the solder paste to reflow properly

Also known simply as screen. It is the wire mesh screen that is coated with emulsion in areas through which no deposit is required and used to screen print pastes. Solder pastes are often printed through completely open areas on a metal stencil

Surface mount assembly – another term for SMT

Surface mount component – a component whose leads have been formed to enable surface placement and reflow

Surface mount device – a component whose leads are formed to enable it to be placed and soldered onto a circuit board

Surface mount technology – the name given to the technique for populating circuit boards whereby components are placed directly onto the surface of the board and into pre-printed solder paste. The solder paste is reflowed to enable attachment of the component to the printed wire

The distance between the silk screen or stencil and the substrate. Part of the set up in a conventional screen print process

Small outline – a term used to describe a family of surface mount components so called because they are smaller than their equivalent dual in line packages

Small outline integrated circuit

An alloy, normally of two or three metals, that has a relatively low temperature melting point (normally <350ºC though the official figure is 427ºC or 800ºF) and that is used to join components to conductor tracks on circuit boards. Regular tin lead solders have a eutectic of 179ºC but the new generation lead-free solders have a higher melting (~220ºC)

Small spheres of solder that are separate from the solder joint, that sit at the edge of the solder flux and that remain on the board after the soldering operation. They can be the source of electrical shorts

See Mid-chip beads

An electrical short circuit between two conductors by solder “bridging” above the dielectric or solder resist

A coating applied over selected parts of a PCB or substrate that acts as a mask to prevent solder flow in the covered areas

The screen printable mixture of solder alloy powder, solvent, print medium and flux used to attach components in surface mount technology

The ability of a component lead or the conductor pad onto which it sits to accept solder

The process of joining metallic surfaces with solder, without melting either the conductor pad or the component lead materials

Temperature below which a non-eutectic alloy is completely solid



Small outline transistor – the common package is a SOT23 which has two leads on one side and a single lead on the other as expected with an individual transistor

The metal or hard rubber blade that is used in a screen printing machine to force paste through apertures in a stencil or screen

A metal formed mask that is suitable for solder printing and that has the desired areas

Surface Insulation Resistance

Contraction of “surface active agent.” A chemical added to water in order to lower surface tension and allow penetration of water under tighter spaces

Tape automated bonding

Thermal coefficient of expansion and same as CTE

The metallised surfaces on the ends of chip components

The accelerated testing of components and assemblies by repeatedly heating and cooling them to induce stress and thereby verify their long term reliability

The ability of a substance to remain gel like at rest but to flow freely when worked (as in screen printing) and to return to a gel like condition once the print operation is complete

The soldering of leads, conductors and terminations prior to the solder joining process to facilitate and enhance solderability

Thin needle shaped metallic growth on solders between conductors and lands. This phenomenon is noticed more on lead free solders compared to their leaded counterparts

One of a number of terms (the others include Manhattan skyline effect, draw bridging) that describe the raising of one end of tiny chip components up to a full 90º perpendicular to the board (resistor and capacitors in particular) during the soldering reflow process and, aggravatingly, requiring rework

An alternative solder paste reflow method

The plated or printed post that connects two different levels of conductors in a multilayer circuit

A measure (in Pa.s – Pascal. seconds) of a material’s resistance to flow or change shape. Frequently it is measured in centipoises (cPs), which is one millipascal

The absence of a material in any area

A paste whose residues may be removed with water after reflow soldering has taken place

The degree to which a component lead or conductor pad is wetted by solder that flows on it

The effect of solder spreading over both component lead and conductor pads to give complete and uniform coverage (see dewetting)