PCB glossary

The printed circuit board industry is full of specific terminology and acronyms. The following is a list of common terms that might come in handy both if you are in the business, or just curious about it.


As Agreed Upon Between User and Supplier

Access Hole:
A series of holes in successive layers of a multi-layer board each set having their centers on the same axis. These holes provide access to the surface of the land on one of the layers of the board.
Acrylic Adhesive:
An adhesive used to bond Multi-layered flex circuits together and also used to adhere the Coverlay used on flex layers / boards.


Aluminum is a metal often used as a conductor or packaging material. It is also sometimes used to wrap up leftovers. Unwrap them before heating in the microwave!

Formula or Composition:Al
Bulk Resistivity:2.65 -cm
Temperature Coefficient of Resistivity (TCR):4300 ppm/°C
Mass Density:2.702 gr/cc
Heat Capacity:902.1 J/kg/°C
Thermal Conductivity (k):238 W/m°C
Temperature Coefficient of Expansion (TCE):23.03 ppm/°C
Melting Point, °C:660 °C
Melting Point, °F:1221 °F

American National Standards Institute

Annular Ring:
The portion of conductive material completely surrounding a plated hole or via.  This is found on inner and outer layers.

Automated Optical Inspection

Aperture Information:
This is a text file describing the size and shape of each element on the board. These are also known as D-code lists. These lists are not necessary if your files are saved as Extended Gerber with embedded Apertures (RS274X).
A group of elements or circuits (or circuit boards) arranged in rows and columns on a base material.
An accurately scaled configuration used to produce the artwork master or production master.
Artwork Master:
The photographic film that embodies the image of the PCB pattern, usually on a 1:1 scale.

Aspect Ratio:
A ratio of the PCB thickness to the diameter of the smallest hole.

Asymmetric Stripline:
Similar to the symmetric stripline except that the dielectric thickness above and below the trace are different. The material is typically of the same kind.


Automated Optical Inspection (AOI):
Visual inspection of the circuit boards using a machine scanner to assess workmanship quality.

Assembly File:
A drawing describing the locations of components on a PCB.
Automatic Test Equipment (ATE):
Equipment that automatically analyzes functional or static parameters in order to evaluate performance.


Bare Board:
An unpopulated PCB.

The cylinder formed by plating through a drilled hole.
Base Copper:
The thin copper foil portion of a copper-clad laminate for PCBs. It can be present on one or both sides of the board, and on inner layers.
Base Material:
The insulating material upon which a conductive pattern may be formed. It may be rigid or flexible or both. It may be a dielectric or insulated metal sheet.
Base Material Thickness:
The thickness of the base material excluding metal foil or material deposited on the surface.
Bed-Of-Nails Fixture:
A test fixture consisting of a frame and a holder containing a field of spring-loaded pins that make electrical contact with a planar test object (i.e., a PCB).
An angled edge of a printed board.

Ball Grid Array

Bikini-Cut/ Partial Coverlay
This is the coverlay material that is used to insulate the circuitry on the flexible layers. This coverlay is flexible as well. This material only partially covers the flexible layer and should not extend more than .050” into the rigid portion of the board.

Bilateral Tolerance
A tolerance in which variation is permitted in both directions from the specified dimension.

Blind Via:
A conductive surface hole that connects an outer layer with an inner layer of a multi-layer board.

A localized swelling and separation between any of the layers of a laminated base material, or between base material or conductive foil. It is a form of Delamination.
Board Thickness
The overall thickness of the base material and all conductive materials deposited thereon

Bill of Material
Bond Strength:
The force per unit area required to separate two adjacent layers of a board by a force perpendicular to the board surface.
Border Area
The region on a base material that is external to that of the end product being fabricated within it.

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.
Brominated Epoxy
An epoxy resin containing chemically bound bromine, which is added to act as a flame retardant.
B-Stage Material:
Sheet material impregnated with a resin cured to an intermediate stage (B-stage resin). Prepreg is the popular term.
B-Stage Resin:
A thermosetting resin that is in an intermediate state of cure.
Buried Via:
A via hole that does not extend to the surface of a printed board.
Rough material left on a PCB after drilling or cutting
Button Print and PlatingThis is where the pad and holes are imaged and plated in lieu of the entire layer pattern. This is typically done on flex product to reduce cracking of the signals caused by hydrogen embrittlement introduced during the electro plating process.

Button Print and Plating:
This is where the pad and holes are imaged and plated in lieu of the entire layer pattern. This is typically done on flex product to reduce cracking of the signals caused by hydrogen embrittlement introduced during the electro plating process.

See Computer-Aided Design.
See Computer-Aided Manufacturing.
Cap Lamination
A process for making multi-layer printed boards with surface layers of metal-clad laminate bonded in a single operation.

CEM-1 / CEM-3
CEM = Composite Epoxy Material) is very similar to FR-4. 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 of FR-4. CEM-1 is is a paper based laminate with one layer of woven glass fabric.It is not suitable for Plated Through Hole, same as FR1-3. CEM-1 is used for single sided PCBs.

A broken corner to eliminate an otherwise sharp edge.

The interconnection of a number of devices in one or more closed paths to perform a desired electrical or electronic function.
Circuitry Layer:
A layer of a printed board containing conductors, including ground and voltage planes.
Circumferential Separation
A crack or void in the plating extending around the entire circumference of as plated through hole, a solder fillet around lead wire or eyelet, or the interface between a solder fillet and a land.
Clad – Cladding
A condition of the base material to which a relatively-thin layer or sheet of metal foil has been bonded to one or both of its sides, e.g. “a metal-clad base material.”
A room in which the concentration or airborne particles is controlled to specified limits.
Clearance Hole
A hole in a conductive pattern that is larger than and coaxial with a hole in the base material of a printed board.

Coated Microstrip:
Similar to the “embedded microstrip”, differing from it because of the dielectric thinness on top and the construction process. The dielectric on top is usually the solder mask coating the PCB surface. It is an extreme case of Embedded Microstrip with different dielectric constant than the material below.
The impedance does not usually change significantly from the regular Microstrip case except in case of very thin traces, which change a few units percent

Coefficient of Thermal Expansion CTE  (The expansion of the PCB thickness)
Z-CTE are measured as PPM per oC, or as the total material expansion from 50-260oC, in % of thickness. It is specially interesting to know the thermal expansion above Tg, where the expansion rate exellerates rapidely. Here you can sort the good from the ”less good” laminates!
Z-CTE is described in IPC TM650 2.4.24C
CTE values are important since they influence the reliability of the finished circuit.
Other things being equal, less thermal expansion will result in greater circuit reliability as less stress is applied to plated holes

Conformal Coating
An insulating protective coating that conforms to the configuration of the object coated and is applied on the completed board assembly

CTI  Comparative Tracking Index

What is Comparative Tracking Index(CTI)?

Here CTI is a quality item that refers to copper clad laminate which is widely used in home electrical appliance or other high-voltage(110V, 220V) electrical apparatus.
It is a simulated conditon that the PCB is polluted in its working environment, which result in leakage or short-circuit at the track gap of the PCB surface, being accompanied by heat releasing and charring.

The way of experiment is that continous 50 drops of 0.1% ammonium chloride solution are dropped between two points on the PCB surface, 30 seconds per drop, turning on high voltage AC current to do the test.
Firstly trying 300V to generate 1A current. There’s ammonium chloride solution on the surface, so after current is switched on it will produce resistance who also bring out heat, then the solution is slowly evaporated. 2nd drop is on and till to 50 drops to see if the PCB has leakage or not. Once the PCB has 0.1A creepage and exceeds 0.5 seconds, it’s judged Failure.

The quality of CTI of laminate refers to the externally applied voltage value and without failure of 50 drops. If abovementioned 300V passed, we can increase the voltage to 400V, 500V or 600V till to the high value before failure, that is the data of the laminite CTI.

Bicheng offers high CTI PCB’s (high CTI 600V FR-4 and aluminum backed material) which is working in such harsh environment of high voltage, filth and humidity.

Performance Level Categories (PLC) were introduced to avoid excessive implied precision and bias.

Tracking Index (Volt)    PLC
600 and Greater             0
400 through 599            1
250 through 399            2
175 through 249            3
100 through 174            4
<100                            5

NOTE: PLC=Performance Level Category 

As per the standard of IEC,the smaller a substrate of CTI grade, the better resistance to tracking. Normal FR-4 ranges 175-225V

Compensated Artwork (Scaling)
Production master or artwork data that has been enlarged or reduced in order to meet the needs of subsequent processing requirements.

An electronic device, typically a resistor, capacitor, inductor, or integrated circuit (IC), that is mounted to the circuit board and performs a specific electrical function.
Component Hole:
A hole used for the attachment and electrical connection of a component termination, such as a pin or wire to the circuit board.
Component Side:
The side of the circuit board on which most of the components will be located. Also called the “top side.”
Computer-Aided Design (CAD):
A software program with algorithms for drafting and modeling, providing a graphical representation of a printed board’s conductor layout and signal routes.
Computer-Aided Manufacturing (CAM):
The use of computers to analyze and transfer an electronic design (CAD) to the manufacturing floor.
Computer-Integrated Manufacturing (CIM):
Software that takes assembly data from a CAD or CAM package and, using a pre-defined factory modeling system, outputs routing of components to machine programming points and assembly and inspection documentation.
A thin conductive area on a PCB surface or internal layer usually composed of lands (to which component leads are connected) and paths (traces).
Conductor Spacing:
The distance between adjacent edges (not centerline to centerline) of isolated conductive patterns in a conductor layer.
Conductor Thickness:
The thickness of the conductor including all metallic coatings, non-conductive coatings excluded.
Conformal Coating:
An insulating protective coating that conforms to the configuration of the object coated and is applied on the completed board assembly.
Acrylic resin (AR): Acrylics are fairly easy to apply and dry rapidly, reaching optimum physical properties in minutes, while providing a long pot life.
Furthermore, acrylics have good humidity resistance, are low exothermic and give off little or no heat during cure, eliminating damage to heat-sensitive
components, and do not shrink due to the solvent evaporation process during cure. Their main disadvantage is solvent sensitivity, but this is also an
advantage, as it makes them the easiest coatings to rework.
Urethane resin (UR): Polyurethane coatings are available in both single- and two-part formulations. Both formulations provide good humidity and high
chemical resistance. Due to these variations, some polyurethane coatings are easy to
apply and cure rapidly, with other materials more difficult to apply because of their shorter pot life. With their wide range in good-to-excellent material
properties, these characteristics also become their drawbacks in that chemical and mechanical removal techniques may become difficult and costly.
Epoxy resin (ER): Epoxies are more complicated to apply than other materials because of their shorter pot life since they are usually available only as
two-part compounds. Furthermore, as a result of their cross-linking design, they provide average humidity resistance and high chemical resistance
compared to other coating materials. However, their strength versus other coating materials is their abrasion resistance, but this also adds to their
rework complexity, as chemical removal may attach to epoxy-coated components and the board itself and cannot easily be removed via mechanical
methods due to abrasion resistance.
Silicone resin (SR): Silicones are a different form of coating, compared to other materials, with their main advantage being resistance to higher
continuous temperatures and thermal expansion properties. Furthermore, silicones have high humidity resistance, and thanks to their 100%-solids
design, have extended pot life, providing a fairly easy application and quick drying. Their main disadvantage is abrasion resistance and rework
complexity. With the abrasion resistance a disadvantage, this should lead to lower rework complexity. However, the rework disadvantage is not in the
coating removal, but rather the removal of residues that may be left from the coating.

Connector Area:
The portion of the circuit board that is used for providing electrical connections.
Controlled Impedance:
The matching of substrate material properties with trace dimensions and locations to create specific electric impedance as seen by a signal on the trace.


Formula or Composition:Cu
Bulk Resistivity:1.673 -cm
Temperature Coefficient of Resistivity (TCR):3930 ppm/°C*
Mass Density:8.92 gram/cc
Heat Capacity:385.2 J/kg/°C
Thermal Conductivity (k):416 W/m°C
Temperature Coefficient of Expansion (TCE):16.6 PPM/°C
Melting Point, °C:1083 °C
Melting Point, °F:1981 °F

* Recent correction to table. Tempco value is at 20 degrees C (it’s a slight function of temperature).

Core Construction:

PCB fabrication process that piles up core materials with intermediate prepeg material. This method always results in an even number of layers.

Core Thickness:
The thickness of the laminate base without copper.
Cover Coat
*See “Cover Lay.”
Cover Lay (Flexible Circuit)
The layer of insulating material that is applied covering over a conductive pattern on the outer surfaces of a printed board.
Crazing (Base Material)
An internal condition that occurs in reinforced laminate base material whereby glass fibers are separated from the resin at the weave intersections. (This condition manifests itself in the form of connected white spots or crosses that are below the surface of the base material.) It is usually related to mechanically induced stress.
The breaking up of large conductive areas by the use of a pattern of voids in the conductive material.

Date Code
Marking of products to indicate their date of manufacture.

Process of removing burrs after drilling

Decomposition temperature, Td

The decomposition temperature is a measure of actual chemical and physical degradation of the resin system.  This test uses thermo-gravimetric analysis (TGA), which measures the mass of a sample versus temperature.
The decomposition temperature is reported as the temperature at which 5% of the mass of the sample is lost to decomposition when heating up to 550C at 10C/min rate.  (IPC 650 2.4.24-6)

Any non conformance to specified requirements by a unit or product.

The fidelity of reproduction of pattern edges, especially in a printed circuit relative to the original master pattern.
A separation between any of the layers of the base of laminate or between the laminate and the metal cladding originating from or extending to the edges of a hole or edge of board.
Dendritic Growth
Metallic filaments that grow between conductors in the presence of condensed moisture and an electric bias.
Design Rule Checking:
The use of a computer program to perform continuity verification of all conductor routing in accordance with appropriate design rules.
The removal of friction-melted resin and drilling debris from a hole wall.
A condition that results when molten solder has coated a surface and then receded, leaving irregularly shaped mounds separated by areas covered with a thin solder film and with the base material not exposed.
An insulating medium that occupies the region between two conductors.
Dielectric Constant
The ratio of the capacitance of a configuration of electrodes with a specific material as the dielectric between them to the capacitance of the same electrode configuration with a vacuum or air as the dielectric.
Dielectric Strength
The maximum voltage that a dielectric can withstand under specified conditions without resulting in a voltage breakdown, usually expressed as volts per unit dimension.
Digitizing (CAD)
The converting of feature locations on a flat plane to its digital representation in X-Y coordinates.
Dimensional Stability:
A measure of the dimensional change of a material that is caused by factors such as temperature changes, humidity changes, chemical treatment, and stress exposure.
Dimensioned Hole
A hole in a printed board whose location is determined by physical dimensions or coordinate values that do not necessarily coincide with the stated grid.

Dimensional Stability
A measure of the dimensional change of a material that is caused by factors such as temperature changes, humidity changes, chemical treatment, and stress exposure.

Dissipation factor:

A meassure index of the tendency of an insulating material to absorb some of the ac energy from electromagnetic field passing through it. Low values are important for RF applications, but relatively unimportant for logical applications.

Dual Access Flex Circuits
Dual Access flex circuits (also known as back bided flex circuits), contain only a single conductor layer, but are processed to allow access to the conductors from both sides. This construction is often employed in IC packaging
Double-Sided Board:
A printed board with a conductive pattern on both sides.
The act of forming holes (vias) in a substrate by mechanical or laser means.
Dry-Film Resists:
Coating material specifically designed for use in the manufacture of printed circuit boards and chemically machined parts. They are suitable for all photomechanical operations and are resistant to various electroplating and etching processes.
Dry-Film Soldermask:
Coating material (dry-film resist) applied to the printed circuit board via a lamination process to protect the board from solder or plating.


Export Administration Regulations

Edge Clearance:
The smallest distance from any conductors or components to the edge of the PCB.

Edge Connector:
A connector on the circuit-board edge in the form of gold plated pads or lines of coated holes used to connect other circuit board or electronic device.

E-glass or “electronic glass”
is the primary glass used in yarns that are used to construct fiberglass fabrics, and is the least expensive among the three, E-glass, S-Glass or NE-Glass.

Electrodeposited Foil
A metal foil that is produced by electro deposition of the metal onto a material acting as a cathode.
Electro Deposition
The deposition of a conductive material from a plating solution by the application of electrical current.

Electrical breakdown voltage DBV.
The voltage per unit thickness of an insulator at which an arc may develop through insulator.

Electroless / Electro less Copper:
A thin layer of copper deposited on the plastic or metallic surface of a PCB from an autocatalytic plating solution (without the application of electrical current).

Electroless / Electro less Deposition
The deposition of conductive material from an autocatalytic plating solution without the application of electrical current.

Electromagnetic Interference (EMI)
Unwanted electromagnetic energy that may couple into electrical circuits and adversely affect their performance.

Electrostatic Discharge (ESD)
The rapid spontaneous transfer of electrostatic charge, induced by a high electrostatic field.

The electrodeposition of an adherent metal coating on a conductive object. The object to be plated is placed in an electrolyte and connected to one terminal of a direct current (DC) voltage source. The metal to be deposited is similarly immersed and connected to the other terminal.
The increase in length of a material that is caused by a tensile load.

Embedded Microstrip:
Similar to the plain or “surface microstrip” but buried into the dielectric material.

Engineering Drawing
A document that discloses the physical and functional end-product requirements of an item by means of pictorial and/or textual presentations.
A family of thermosetting resins. Epoxies form a chemical bond to many metal surfaces.
Epoxy Glass Substrate
A two-part epoxy resin that polymerizes spontaneously when the two components are mixed, combined with glass fiber to form a substrate
Epoxy Smear:
Epoxy resin that has been deposited on edges of copper in holes during drilling either as uniform coating or in scattered patches. It is undesirable because it can electrically isolate the conductive layers from the plated-through-hole interconnections.
Etch Factor
The ratio of the depth of etch to the amount of lateral etch, i.e., the ratio of conductor thickness to the amount of undercut.
Etchback / Etch Back:
The controlled removal of all components of the base material by a chemical process acting on the sidewalls of plated-through holes to expose additional internal conductor areas.

Negative Etchback    Typically when a PCB is manufactured, Plated Though Holes (PTH) are manufactured through a process which begins with the
laminate material containing the copper conduction land being drilled. After a number of intermediate processes, the drilled holes which are to be plated
are cleaned (or desmeared).
The process inherently causes the copper land to be recessed in from the edge of the hole walls.


The panel assembly is then put through a complex series of processes which sees the holes plated with copper and hence electrically and mechanically
bonding to the copper land of the different layers within the PCB structure.
Positive Etchback
While traditional Negative Etchback provides a cost effective and moderately reliable solution for the majority of applications, certain applications such as
Military, Medical or Aerospace applications cannot afford to make this cost/performance trade off. In such applications where reliability is paramount, PTH
holes manufactured with an Etchback (Positive) process is the solution.

This process causes the dielectric material in the hole walls to be etched back, causing the copper land to protrude out past the edge of the hole walls.


This enables the THP hole plating process to bond to up to three sides of the copper land, providing the greatest degree of reliability and immunity against
metal fatigue due to mechanical stresses imposed by both external mechanical shock and thermal shock.


Etchback relates to the relationship between the edge of the copper land and the edge of the hole wall prior to the plating process. While the majority of
PCBs are manufactured using a Negative Etchback technique, which provides a cost affective moderately reliable solution for the majority of application,
Etchback (positive) is seen as a better solution for applications requiring the highest levels of reliability.

The chemical, or chemical and electrolytic, removal of unwanted portions of conductive materials.
Fiducial Mark
A printed board artwork feature (or features) that is created in the same process as the conductive pattern and that provides a common measurable point for component mounting with respect to a land pattern or land patterns.

Fine Pitch:
Fine pitch is more commonly referred to surface-mount components with a lead pitch of 25 mils or less.

A gold-plated terminal of a card-edge connector. Also see Gold Finger.

First Article:
A sample part or assembly manufactured prior to the start of production for the purpose of assuring that the manufacturer is capable of producing a product that will meet specified requirements.

Flux:The material used to remove oxides from metal surfaces and enable wetting of the metal with solder.

Flying Probe:
A testing device that uses multiple moving pins to make contact with two spots on the electrical circuit and send a signal between them, a procedure that determines whether faults exist.

Foil construction:
PCB fabrication process similar to the Core Construction except in the external layers. The external layers are added using sheets of copper foil on top of prepeg material.  Even though this method can theoretically produce odd number of layers it is recommended to still
use an even number due to the risk of warpage and cost (it is usually cheaper to add a layer).

Foil Lamination
A process for making multilayer printed boards with surface layer(s) of metal foil bonded in a single operation.

FR-1 is basically the same as FR-2. FR-1 has a higher TG of 130°C instead of 105°C for FR-2. Some laminate manufacturers who produce FR-1 may not produce FR-2 since the cost and usage are similar and it is not cost effective for having both. Usally used for 1-2 layer boards without connection through the holes.
FR2 laminates are composed of multiple plies of cellulose (‘Kraft’) paper that have been impregnated with a flame-retardant phenolic resin. FR-2 laminate is less expensive than FR-4, and the cost difference becomes even greater for the finished board, because holes and profile can be created by punching. FR-2 is typically used in applications where tight dimensional stability is not required, such as in radios, calculators, toys, and television games. FR-2 is an opaque brown in colour. Usally used for 1-2 layer boards without connection through the holes.

FR-3 is is also basically FR-2. But instead of phenolic resin it uses an epoxy resin binder. Not recommended for multilayer builds.

The UL-designated rating for a laminate composed of glass and epoxy that meets a specific standard for fire-retardance. FR-4 is the most common dielectric material used in the construction of PCBs.

Fully Additive Process
An additive process wherein the entire thickness of electrically- isolated conductors is obtained by the use of electroless deposition.


Gallium Arsenide

GaAs is the semiconductor that spawned the entire MMIC industry. In addition to it’s great semiconductor properties, it is also an excellent substrate for microwaves because its resistivity is so high (much higher than even “high resistivity” silicon). GaAs wafers are usually referred to as semi-insulating. GaAs also has very low loss tangent.

This data came from various sources including TriQuint and Avago. Some of this info came from Russia’s Ioffe Institute.

Formula or Composition:GaAs
Dielectric Constant ():12.88
Dissipation Factor (a.k.a. loss tangent, or tan ):0.0004
Temperature Coefficient of :6.8 ppm/°C
Bulk Resistivity:>10E5 Ohm-cm
Temperature Coefficient of Resistivity (TCR):ppm/°C
Mass Density:5.32 gr/cc
Specific Heat:0.33 J/g/°C
Thermal Conductivity (k):55 W/m°C
Temperature Coefficient of Expansion (TCE):5.7 ppm/°C
Melting Point1238°C
2260 °F

Glass Transition Temperature , Tg

The temperature at which an amorphous polymer, or the amorphous regions in a partially crystalline polymer, changes from being in a hard and relatively brittle condition to being in a viscous or rubbery condition.
Tg is important to understand since the properties of base materials are different above the Tg versus below the Tg.

Golden Board:
See Known Good Board.

Gold Finger:
The gold-plated terminal of a card-edge connector. Also see Finger.

Ground / Ground Plane:
A conductor layer, or portion of a conductor layer, used as a common reference point for circuit returns, shielding, or heat sinking.
Ground Plane Clearance
Removed portions of a ground plane that isolate it from a hole in the base material to which the plane is attached.

A laminate consisting of woven epoxy-glass cloth impregnated with epoxy resin under pressure and heat. G10 lacks the anti-flammability properties of FR-4. Used mainly for thin circuits such as in watches.

Mechanically induced fracturing or delamination, on or below the surface of a base material that is usually exhibited by a light area around holes or other machined features.

HDI (High Density Interconnect)
Ultra fine-geometry multi layer PCB constructed with conductive surface Microvia connections between layers. These boards also usually include buried and/or blind vias are made by sequential lamination.

Heat Sink
A mechanical device that is made of a high thermal-conductivity and low specific-heat material that dissipates heat generated by a component or assembly.
Hole Breakout:
A condition in which a hole is partially surrounded by the land.
Hole Pattern:
The arrangement of all holes in a printed board with respect to a reference point.
Hole to Copper
Any copper feature location relative to the nearest drilled hole, measured without plating.
Hole Void
A void in the metallic deposit of a plated-through hole that exposes the base material.
Hot Air Solder Leveling (HASL):
A method of coating exposed copper with solder by inserting a panel into a bath of molten solder then passing the panel rapidly past jets of hot air.

International Electrotechnical Commission

Institute of Electrical and Electronic Engineers

International Standards Organization

International Traffic in Arms Regulations

The process by which panelization data are transferred to the photoplotter, which in turn uses light to transfer a negative image circuitry pattern onto the panel.
Immersion Plating
The chemical deposition of a thin metallic coating over certain basis metals that is achieved by a partial displacement of the basis metal.
The total passive opposition offered to the flow of electric current. This term is generally used to describe high-frequency circuit boards.
The internal layers of laminate and metal foil within a multi-layer board.
Inner layer Connection
A conductor that connects conductive patterns on internal layers of a multilayer printed board, e.g. a plated-through hole.
Insulation Resistance:
The electrical resistance of an insulating material that is determined under specific conditions between any pair of contacts, conductors, or grounding devices in various combinations.
Internal Layer
A conductive pattern that is contained entirely within a multilayer printed board.

Known Good Board (KGB):
A board or assembly that is verified to be free of defects. Also known as a Golden Board.

The plastic material usually reinforced by glass or paper that supports the copper cladding from which circuit traces are created.
Laminate Thickness:
Thickness of the metal-clad base material, single- or double-sided, prior to any subsequent processing.
Laminate Void:
An absence of epoxy resin in any cross-sectional area that should normally contain epoxy resin.
The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components. Also called a pad.

Laser – Laser Drilling
Dual Head Laser, UV – copper ablating laser  and CO2 – Dielectric ablating laser.

Laser Photo-Plotter
A plotter that uses a laser, which simulates a vector photo-plotter by using software to create a raster image of the individual objects in a CAD database, then plots the image as a series of lines of dots at a very fine resolution. A laser photo-plotter is capable of more accurate and consistent plots than a vector plotter.

Layer-to-Layer Registration
The degree of conformity of a conductive pattern, or portion thereof, to that of any other conductor layer of a printed board.

Layer-to-Layer Spacing
The thickness of dielectric material between adjacent layers of conductive patterns in a printed board.
The process in which treated prepregs and copper foils are assembled for pressing.
A format of lettering or symbols on the printed circuit board: e.g. part number, serial number, component locations, and patterns.
Lifted Land
A land that has fully or partially separated (lifted) from the base material, whether or not any resin is lifted with the land.
Liquid Photoimageable Soldermask (LPI):
A mask using photographic imaging techniques to control deposition.
See Conductor.
A quantity of circuit boards that share a common design.

Major Defect:
A defect that is likely to result in failure of a unit or product by materially reducing its usability for its intended purpose.
A material applied to enable selective etching, plating, or the application of solder to a PCB. Also called soldermask or resist.
Manufacturing Drawing (Fabrication Drawing)
A document that shows the dimensional limits or grid locations that are applicable to any and all parts of a product to be fabricated, including the arrangement of conductors and nonconductive patterns or elements; the size, type, and location of holes; and all other necessary information.
Mass Lamination
The simultaneous lamination of a number of pre-etched, multiple-image, C-staged resin panels or sheets that are sandwiched between layers of B-staged resin and copper foil.

Metal Core Printed Circuit Pcb.

A condition that occurs in laminated base material in which internal glass fibers are separated from the resin at the weave intersection. (This condition manifests itself in the form of discrete white spots or “crosses” that are below the surface of the base material. It is usually related to thermally induced stress.)

Metal-Clad Base Material
Base material covered with conductive foil on one or both sides.

Metal Foil:
The plane of conductive material of a printed board from which circuits are formed. Metal foil is generally copper and is provided in sheets or rolls.
The preparation of a specimen of a material, or materials, that is to be used in metallographic examination. This usually consists of cutting out a cross-section followed by encapsulation, polishing, etching, and staining.

Consists of a trace running on the surface of a PCB separated by one or more layers of dielectric material from a ground plane located underneath. It is also called “surface microstrip” to distinguish it from the “coated” or “embedded” variations.

Usually defined as a conductive hole with a diameter of 0.15mm or less that connects layers of a multilayer PCB. Often used to refer to any small geometry connecting hole the creation of which is beyond the tradition practical drilling capabilities.

Minimum Annular Width
The minimum width of metal(s) at the narrowest point between the edge of a hole and the outer edge of a circumscribing land. (This determination is made to the drilled hole on internal layers of multilayer printed boards and to the edge of the plating on external layers of multilayer and double-sided printed board.)
Minor Defect:
A defect that is not likely to result in the failure of a unit of product or that does not reduce the usability for its intended purpose.
Mounting Hole
A hole that is used for the mechanical support of a printed board or for the mechanical attachment of components to a printed board.
Multi-Layer Board:
Printed boards consisting of a number (four or more) of separate conducting circuit planes separated by insulating materials and bonded together into relatively thin homogeneous constructions with internal and external connections to each level of the circuitry as needed.


Nail Heading
The flared condition of copper on an inner conductive layer of a multilayer printed board that is caused by hole drilling.

NE-glass has improved electrical and mechanical performance over E-glass and is typical used in the Nelco 4000-13SI and N6000-21SI  high-performance laminate product lines. glass_property.jpg

OSP   Organic Solderability Preservative
Surface PCB finish, thickness 0.3um. Typical use = soldering.

The top and bottom sides of any type of circuit board.

The gaseous emission from a laminate printed board or component when the board or the printed board assembly is exposed to heat or reduced air pressure, or both.

See Land.

The description of copper and dielectric layers constituting a PCB, specifying each thickness. It consists of a number of pre-peg, cores and copper layers. Since the optimum padstack is PCB fab technology dependent, it is always a good idea to check a proposed padstack with your PCB manufacturer.

A rectangular sheet of base material or metal-clad material of predetermined size that is used for the processing of one or more printed boards and, when required, one or more test coupons.
Panel Drawing
A document that shows the production master with related manufacturing patterns and artifacts that relate to the fabrication of printed boards.
Panel Plating
The plating of an entire surface of a panel including holes.
Partial (Bikini) Coverlay
This coverlay is typically used in the manufacture of Rigid-Flex boards where the coverlay material is only in the flexible portion of the board. This removes acrylic adhesive from the rigid portions of the board increasing board reliability.

The configuration of conductive and nonconductive materials on a panel or printed board. Also, the circuit configuration on related tools, drawing, and masters.

Pattern Plating:
The selective plating of a conductive pattern.
Peel Strength
The force per unit width that is required to peel a conductor foil from a laminate perpendicular to the surface of the substrate.
Developed by Baekeland and Thuslow in the early 1900s, the products formed by the condensation of phenols with formaldehyde were sold as Bakelite and Novolac. Phenol-formaldehyde resins (phenolics) were the first thermosets to be used for electrical laminates because they are easy to process and have good resistance to heat and chemicals.

Photographic Image:
An image in a photo mask or in an emulsion that is on a film or plate.
A photographic process whereby an image is generated by a controlled light beam that directly exposes a light-sensitive material.
Photo Print:
The process of forming a circuit pattern image by hardening a photosensitive polymeric material by passing light through a photographic film.

Photo Resist
A material that is sensitive to portions of the light spectrum and that, when properly exposed can mask portions of a base metal with a high degree of integrity.
Photo Resist Image
An exposed and developed image in a coating on a base material.
A transparent film that contains the circuit pattern, which is represented by a series of lines of dots at a high resolution.

Pinhole (Material)
An imperfection in the form of a small hole that penetrates entirely through a layer of material.
Pinhole (Photo tool)
A clear defect that is completely within a black pattern or in the black background of a clear pattern.
An imperfection in the form of a small hole that does not penetrate entirely through a layer of foil.
The nominal center-to-center distance of adjacent conductors. (When the conductors are of equal size and their spacing is uniform, the pitch is usually measured from the reference edge of the adjacent conductors.)

Plastic Leaded Chip Carrier (PLCC)
A component package with J-leads.

Plated Through-Hole:
A hole with plating on its walls that makes an electrical connection between conductive layers, external layers, or both of a printed board.
A flat plate of metal within the lamination press in between which stacks are placed during pressing.
Plating Void:
The area of absence of a specific metal from a specific cross-sectional area.
The mechanical converting of X-Y positional information into a visual pattern such as artwork.

Post Curing
Heat aging in order to stabilize material through stress relieving.

Pouch Material
The protective barrier material used in the manufacture of Rigid-Flex Boards. This material is typically removed from the flexible portion of the board prior to shipment.  The pouch is Covercoat material used to protect the exposed flexible materials during the normal processing of the rigid-flex boards.

Sheet material (e.g. glass fabric) impregnated with a resin cured to an intermediate stage (B-stage resin).
Most PCB manufacturers currently utilize five types of prepreg with 106, 1080, 2116, 1500 and 7628 glass styles.
Due to various limitations as to the number of plies and/or types of prepreg that can be utilized between layers of a board, specific applications need to be discussed with the PCB manufacturer. Not all styles are common in all markeds.

Against core
with 17 um
copper and
signal traces
utilizing 30% of
the board area.
Against core
with 17 um
copper and
plane utilizing
70% of the
board area.
Against core
with 35 um
copper and
signal traces
utilizing 30% of
the board area.
Against core
with 35 um
copper and
plane utilizing
70% of the
board area.
Against core
with 70 um
copper and
signal traces
utilizing 30% of
the board area.
Against core
with 70 um
copper and
plane utilizing
70% of the
board area.
Against the
top and
copper layers
( Foil)
plies that are
not directly
1060.048 mm0.0558 mm0.0381 mm0.0508 mm0.0127 mm0.0381 mm0.0584 mm0.0533 mm
10800.066 mm0.0711 mm0.0533 mm0.066 mm0.0279 mm0.0558 mm0.076 mm0.0686 mm
21130.0889 mm0.094 mm0.076 mm0.0889 mm0.0508 mm0.0787 mm0.099 mm0.0889 mm
21160.120 mm0.1245 mm0.107 mm0.1194 mm0.0813 mm0.1092 mm0.1295 mm0.1168 mm
76280.165 mm0.1727 mm0.1524 mm0.1651 mm0.127 mm0.1549 mm0.1753 mm0.1575 mm

Aproximate values above. This thickness guide is provided as a guide only. The actual thickness will be affected by the copper distribution within the design as well as within the production panels

The process by which a combination of heat and pressure are applied to a book, thereby producing fully cured laminated sheets.
Printed Board:
The general term for completely processed printed circuit or printed wiring configurations. It includes single, double-sided, and multi-layer boards, both rigid and flexible.
Printed Circuit:
A conductive pattern that comprises printed components, printed wiring, or a combination thereof, all formed in a predetermined design and intended to be attached to a common base. (In addition, this is a generic term used to describe a printed board produced by any of a number of techniques.)
Printed Wiring Board:
A part manufactured from rigid base material upon which completely processed printed wiring has been formed.

The degree of conformity to the position of a pattern, or a portion thereof, a hole or other feature to its intended position on a product.

Registration Mark
A stylized pattern (symbol) that is used as a reference point for registration.
Any visual or measurable form of process-related contamination.
Resin Recession
The presence of voids between the plating of a plated-through hole and the wall of the hole as seen in micro sections of plated-through holes that have been exposed to high temperatures.

Resin (Epoxy) Smear:
Resin transferred from the base material onto the surface of the conductive pattern in the wall of a drilled hole.
Resin-Rich Area
The location in a printed board of a significant thickness of un-reinforced surface-layer resin that is of the same composition as the resin within the base material.
Resin-Starved Area:
The location in a printed board that does not have a sufficient amount resin to completely wet out the reinforcing material. (Evidence of this condition is often in  the form of low-gloss dry spots or exposed fibers.)

Coating material used to mask or to protect selected areas of a pattern from the action of an etchant, solder, or plating. Also called soldermask or mask.

Resistivity of Copper

With designs of finer lines, distributed resistance of copper is becoming increasingly important.  The formula for computing resistivity in copper traces is given by the following equation:
R = (0.679 X 10-6 ohm/inch)  /(width X thickness inches X Length)
Example: In fine-line designs, using 0.5 oz. copper, a .005” trace, 5 inches long, the resistivity will be:
(.679 X 10-6) / ((5 X 0.7 X 106)) X 5 = 0.97Ω
A PCB construction combining flexible circuits and rigid multi-layers usually to provide a built-in connection or to make a three-dimension form that includes components.

RoHS (Reduction of Hazardous Substances) Compliance
RoHS is the acronym for Restriction of Hazardous Substances. RoHS, also known as Directive 2002/95/EC, originated in the European Union and restricts the use of specific hazardous materials found in electrical and electronic products. All applicable products in the EU market after July 1, 2006 must pass RoHS compliance.
In an effort to support the RoHS initiative, Sunstone Circuits offers several options that comply with the directive. All of the laminate material, soldermask material, and silkscreen material supplied are compatible for assembly at lead free solder temperatures and do not contain (above the upper limits) any of the restricted materials.
A machine that cuts away portions of the laminate to form the desired shape and size of the printed board.
The sum of the cumulative-pitch error across a number of functional patterns on a step-and-repeat photo tool.


A technique in which grooves are machined on opposite sides of a panel to a depth that permits individual boards to be separated from the panel after component assembly.

Screen Printing:
A process for transferring an image to a surface by forcing suitable media through a stencil screen with a squeegee.

Sequentially Laminated Multilayer Printed Board
A multilayer printed board that is formed by laminating together through-hole plated double-sided or multilayer boards. (Thus, some of its conductive layers are interconnected with blind or buried via’s.)

SerDes – A Serializer/Deserializer. ( pronounced sir-deez)
A pair of functional blocks commonly used in high speed communications to compensate for limited input/output. These blocks convert data between serial data and parallel interfaces in each direction. The term “SerDes” generically refers to interfaces used in various technologies and applications. The primary use of a SerDes is to provide data transmission over a single/differential line in order to minimize the number of I/O pins and interconnects.


Read: Material Selection for SERDES Design

Shadowing, Etchback

A condition that occurs during an etchback process in which the dielectric material immediately next to the foil is not removed completely. (This can occur even though an acceptable amount of etchback may have been achieved elsewhere.)
Shear Strength
The force required to shear adhesive-bonded (and cured) materials and/or components.

Short, Electrical (n.)
A fault that causes to be connected two or more points that are normally electrically separated.

Signal Conductor
An individual conductor that is used to transmit an impressed electrical signal.


Silver provides the best electrical conductivity of all metals. It is an order of magnitude less expensive than gold, but it has a tendency to tarnish (oxidize). It is often used in low-loss waveguide components. The silver oxide layer is typically less than a skin depth so it has little effect on electrical loss. Silver pastes are often used in LTCC products in place of more expensive gold conductors.

Formula or Composition:Ag
Bulk Resistivity:1.59 -cm
Temperature Coefficient of Resistivity (TCR):4100 ppm/°C
Mass Density:10.5 gr/cc
Heat Capacity:236.3 J/kg/°C
Thermal Conductivity (k):417 W/m°C
Temperature Coefficient of Expansion (TCE):18.9 ppm/°C
Melting Point, °C:961 °C
Melting Point, °F:1762 °F

Single-Sided Board:

A printed board with conductive pattern on one side only.
Traces that are neither parallel nor intersecting with the glass pattern.

Soldermask Over Bare Copper (SMOBC):
A method of fabricating a printed circuit board that results in final metallization being copper with no protective metal. The non-coated areas are coated by solder resist, exposing only the component terminal areas. This eliminates tin lead under the pads.
Surface Mount Technology (SMT):
Defines the entire body of processes and components that create printed circuit board assemblies with leadless components.
An alloy that melts at relatively low temperatures and is used to join or seal metals with higher melting points. A metal alloy with a melting temperature below 427°C (800°F).

Solder Coat
A layer of solder that is applied directly from a molten solder bath to a conductive pattern.
Solder Resist
A heat-resisting coating material applied to selected areas to prevent the deposition of solder upon those areas during subsequent soldering.

Soldermask / Solder mask:
Coating material used to mask or to protect selected areas of a pattern from the action of an etchant, solder, or plating. Also called resist or mask.
The ability of a metal to be wetted by molten solder.

Solder Wick:
A band of wire removes molten solder away from a solder joining or a solder bridge or just for desoldering.

Statistical Process Control. The collection of process data and creation of control charting is a tool used to monitor processes and to assure that they remain In Control or stable. Control charts help distinguish process variation due to assignable causes from those due to unassignable causes.

A method by which successive exposures to a single image are made to produce a multiple image production master.
A stiffener is a piece of material that is bonded to the printed board to provide mechanical support. A stiffener will be evaluated only as a mechanical support. Void-free bonding of the stiffener to the flexible printed wiring is not required. Specific requirements shall be as agreed upon between user and supplier.
Strain Relief (Connector)
A receptacle connector device that prevents the disturbance of the contact and cable terminations.
Trace running between two ground planes. See under the “symmetric” and “asymmetric” variations.

The process by which imaging material (resist) is chemically removed from a panel during fabrication.
Stress Relief
The portion of a component lead or wire that is formed in such a way as to minimize mechanical stresses after the lead is terminated
A material on whose surface adhesive substance is spread for bonding or coating. Also, any material that provides a supporting surface for other materials used to support printed circuit patterns.

Symmetric Stripline:
This geometry consists of a trace running between two ground planes located in layers above and below with the same dielectric thickness and material on both sides.

Test Coupon:
A portion of a printed board or of a panel containing printed coupons used to determine the acceptability of such a board.
Glass transition temperature. The point at which rising temperatures cause the solid base laminate to start to exhibit soft, plastic-like symptoms. This is expressed in degrees Celsius (°C).
Tetra Functional Resins
Materials that have four reactive groups per molecule.

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 driving force.
Thermal Expansion Mismatch
The absolute difference between the thermal expansion of two components or materials.
Thermal Relief
The crosshatching of a ground or voltage plane that minimizes blistering or warping during soldering operations.
Thermal Zone
A metal-integrity evaluation zone that extends a specified distance beyond the ends of the lands in a micro section of a vertical portion of a plated-through hole. (Unless otherwise specified, the- extended distance is 0.08 mm (0.003-inch).
A plastic that undergoes a chemical reaction when exposed to elevated temperatures that leads to it having a relatively infusible or cross-linked stated that cannot be softened or reshaped by subsequent heating.

Time to Delamination T260  – T288 – T300
The time to delamination is a measure of the time it takes for the resin and copper, or resin and reinforcement, to separate or delaminate.
Bring a sample to a specified temperature –  measure the time it takes for failure to occur.
With Pb-free assembly temperatures reaching above 260oC, T288/300 have become a relevant measure of performance.
IPC TM650 2.4.24-1.


Titanium is a lightweight metal with a low expansion coefficient. It is used in different plating schemes, and often mixed with tungsten and used as an adhesion metal between ceramic substrates and gold conductors.

Formula or Composition:Ti
Bulk Resistivity:55 -cm
Temperature Coefficient of Resistivity (TCR):8500? ppm/°C
Mass Density:4.5 gr/cc
Heat Capacity:523 J/kg/°C
Thermal Conductivity (k):21.9 W/m°C
Temperature Coefficient of Expansion (TCE):ppm/°C
Melting Point, °C:1660 °C
Melting Point, °F:3020 °F

Tooling Holes:

The general term for holes placed on a PCB or a panel of PCBs for registration and hold-down purposes during the manufacturing process.
Top Side:
See Component Side.
A common term for conductor.
The list of instructions describing the board, including any specific processing requirements. Also called a shop traveler, routing sheet, job order, or production order.
A laminate defect in which deviation from planarity results in a twisted arc.
Underwriters Laboratories, Inc., an independent product safety testing and certification organization.
Underwriters Symbol:
A logotype denoting that a product has been recognized (accepted) by Underwriters Laboratories Inc. (UL).
Unsupported Hole
A hole in a printed board that does not contain plating or other type of conductive reinforcement.

A plated through-hole that is used as an interlayer connection but does not have component lead or other reinforcing material inserted in it.
The absence of any substances in a localized area.

Wave Soldering:
A process wherein assembled printed boards are brought in contact with a continuously flowing and circulating mass of solder, typically in a bath.

Migration of copper salts into the glass fibers of the insulating material.
Wrought Foil
A metal foil that is formed by the rolling of cast metal.

The horizontal or left-to-right direction in a two dimensional system or coordinates.

The vertical or bottom-to-top direction in a two dimensional system of coordinates.

Perpendicular to the plane formed by the X and the Y datum reference.