PCB Glossary

The intention of this glossary is to explain the most commonly used terms and abbreviations that come up in PCB documents and daily business transactions. This glossary is not complete by any means but intention is to cover the most usual ones. For more comprehensive view of PCB related technical terms, please see the IPC standard IPC-T-50, Terms and Definitions for Interconnecting and Packaging Electronics Circuits. There may be some individual mismatches between this glossary and IPC standard as this glossary tries to match closely to everyday language of our business.



Automatic Optical Inspection, method of inspecting pattern of any layer in PCB

Aspect Ratio

AR, relation of PCB thickness divided by nominal size of the plated hole, is related to the capability of drilling and plating

Buried via

Mechanically drilled plated hole which starts and ends inside the PCB , for example via between layers 2 and 7 in some 8 layer PCB


Ball Grid Array, commonly used surface mount package for ICs


Computer Aided Design, design of the circuitry and features of the PCB, outputs graphical data (Gerber files) or database (ODB++)


PCB document checking and handling step and 1st process step in PCB manufacturing, checks and modifies customer files to PCB manufacturing documents


Double-sided PCB, has 2 conductive layers (Top and Bottom)


Delivered Duty Unpaid, a delivery term where supplier takes care of transportation, see details in Incoterms 2010


Estimated Annual Usage in pieces, usually forecasted by customer


Electroless Nickel Immersion Gold, metallic solderable surface finish for component contact areas and for mechanical contacts like keypad or spring loaded contact


Electrical Test, test for PCB electrical contacts 


Estimated Time of Arrival


Estimated Time of Delivery

FCA Free Carrier, a delivery term , for example FCA Oulu means that supplier in Oulu will give the goods to the transportation company organized by customer, see details in Incoterms 2010

Floor life

max allowable time between opening vacuum package and the soldering of the PCB (see also MSL)


Flex PCB, designed and manufactured for flexible assembly or dynamic flexible application


Final Quality Control


FR= Flame Retardant, FR4 is one of UL classifications of most commonly used PCB dielectric material, mixture of epoxy resin and glass cloth (possibly also some fillers)


Commonly used format for PCB manufacturing files, most commonly extended gerber RS-274X, also sometimes used as a name of complete PCB file package (including also drawings, specification files, drill files, netlist and other necessary documents)


Hot Air Solder Levelling, metallic solderable surface finish for component contact areas, consist of Sn-Ag (lead-free, such as CN100) or Sn-Pb (leaded)


High Density Interconnection, a PCB having laser vias and overall high packaging density

Impedance control

Controlling impedance in PCB manufacturing, Impedance is an electrical property of a transmission line in PCB, for example 50ohm +/-10%


Integrated Circuit, a silicon chip containing the functionality of electronic component


Association Connecting Electronics Industries, a trade association providing PCB standards and other useful resources for PCB and Electronics industry

IPC Class2

Most commonly used quality standard for PCBs, based on IPC standards IPC-6011 and IPC-6012 (rigid PCB), specifies requirements for finshed PCBs, Class2 is a performance class for 'dedicated service electronics products'

IPC Class 3

Commonly used quality standard for PCBs, based on IPC standards IPC-6011 and IPC-6012 (rigid PCB), specifies requirements for finshed PCBs, Class3 is a performance class for 'high reliability electronics products' (this classification has usually cost impact)

Laser via A plated via hole that has been drilled by laser (CO2 or UV or combined), typically between only 2 layers, for example diameter 100u hole between layer1 to layer2

Laser Direct Imaging, a method for exposing PCB pattern in excellent accuracy by laser beam (no films needed)


Liquid Photoimageable solder mask, Liquid Photoimageable solder resist

Microvia Synonym of laser via (by IPC include also possibility of small via by mechanical drilling or photovia but most commonly understood as laser via)
Mil 1/1000 of an inch, 25,4um, widely in use  (thou is synonym to mil),  For example 4 mils wide line is 100u wide

Multilayer PCB, having more than 2 conductive layers


Maximum Operating Temperature


 Moisture Sensitivity Level, defines the max floor life and soldering conditions, see details in standard IPC/JEDEC J-STD-020  (Rigid PCBs are mostly close to MSL3 in lead-free soldering)


Minimum Order Quantity (in pieces), defined the minimun possible order quantity in pcs for certain price


Minimum Order Value (in currency), defines the minimum possible order value


Non-Plated Through Hole, mechanically drilled hole through the PCB, no copper plating


PCB document database including all necessary data for PCB manufacturing


Organic Solder-ability Preservative, organic solderable surface finish to cover component contact areas (Cu)


Ounce, is fairly commonly used to define nominal copper thickness in non-plated PCB layers, for example 1 oz = 35u; 1/2 oz = 18u


Printed Circuit Board, non-populated board that provides point-to point connections between electrical components


Printed Circuit Board Assembly, PCB with populated electrical components




An adhesive layer between conductive layers (bond ply) in ML stack-up, usually will turn to the same laminate material during the bonding process, for example FR4 prepreg will become FR4 laminate after pressing


PolyTetraFluoroEthylene, Teflon, dielectric material for some RF PCBs


Plated Through Hole, a copper plated hole that connects PCB layers to each other, can be also for component assembly (component hole like pressfit hole)


Printed Wiring Board, synonym to PCB (IPC defines a slight difference)


Quality Control


Quad Flat Pack is a commonly used SMT IC package that has leads in all 4 sides


Quick Turn-Around, express delivery, leadtime below standard leadtime


Resin Coated Copper foil, dielectric for layers for laser drilling, max 75u thick, only epoxy resin (no glass)


Request For Quotation


Restriction of Hazardous Substances, EU directive 2002/95/EC, resitricting the use of lead for example, RoHS compliant means that the part fullfills the RoHS directive and meet the leadfree soldering process requirements

Setup cost

see startup cost

Startup cost

One-time cost for a new revision of the PCB, covers the tooling and documentation cost, does not occur in repeat orders with the same revision of documents


Secondary Imaging Technology, combination of 2 different solderable surface finishes,  typically combination of OSP and ENIG in the same PCB

Shelf life

Time that PCBs can be stored in none-opened vacuum package without compromizing use-ability of the product


Solder Mask, also solder resist, permanent coating material on PCB, covering the areas of PCB that will be not soldered (most commonly green, other colors also)


Surface Mount Technology


Statistical Process Control

Tooling cost

See startup cost


Underwriters Laboratory, a testing organisation for fire safety and classification of PCB like UL94V-0 (flammability and MOT ratings of PCB materials, technologies and manufacturers)

WD, working day Working day is an unit used to describe delivery time, it exludes days off like Saturday, Sunday and public holidays, for example 10wd means usually delivery time of 2 weeks (2x5 days/week)