PCB Glossary

This glossary explains 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 is intended to cover the most usual terms. For a more comprehensive overview 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 the IPC standard, as this glossary was written to closely reflect everyday language in our business.

AOI Automatic Optical Inspection. A method of inspecting pattern of any layer of a PCB.
AR Aspect Ratio. The relation of PCB thickness divided by the nominal size of the plated hole. Related to drilling and plating capabilities.
Buried via Mechanically drilled plated hole that starts and ends inside the PCB (an interlayer connection that does not extend to the surface of the board).
BGA Ball Grid Array. Commonly used surface mount package for ICs.
CAD Computer Aided Design.  Design of the circuitry and features of the PCB. Outputs graphical data (Gerber files) or database (ODB++).
CAM PCB document checking and handling step and first process step in PCB manufacturing. Checks and modifies customer files to PCB manufacturing documents.
DS Double-sided PCB. Has two conductive layers (top and bottom).
DDU Delivered Duty Unpaid. A delivery term indicationg that the supplier takes care of transportation. See details in Incoterms 2010.
EAU Estimated Annual Usage in pieces. Usually forecasted by customer.
ENIG Electroless Nickel Immersion Gold. A metallic solderable surface finish for component contact areas and for mechanical contacts like keypads or spring-loaded contacts.
ET Electrical Test. A test for PCB electrical contacts.
ETA Estimated Time of Arrival
ETD Estimated Time of Delivery
FCA Free Carrier. A delivery term.  For example FCA Oulu means that the supplier in Oulu will give the goods to the transportation company arranged by the customer. See details in Incoterms 2010.
Floor life Max allowable time between opening vacuum package and the soldering of the PCB (see also MSL).
FPC Flex PCB. Designed and manufactured for flexible assembly or a dynamic flexible application.
FQC Final Quality Control
FR4 FR= Flame Retardant. FR4 is one of the UL classifications of the most commonly used PCB dielectric material, a mixture of epoxy resin and glass cloth (may also contain some fillers).
Gerber Commonly used format for PCB manufacturing files. Most commonly extended gerber RS-274X.  Also sometimes used as a name of a complete PCB file package (including drawings, specification files, drill files, netlist and other necessary documents).
HASL Hot Air Solder Levelling. Metallic solderable surface finish for component contact areas, consisting of Sn-Ag (lead-free, such as CN100) or Sn-Pb (leaded).
HDI High Density Interconnection. A PCB with laser vias and overall high packaging density.
Impedance control Controlling impedance in PCB manufacturing. Impedance is an electrical property of a transmission line in a PCB, for example 50ohm +/-10%.
IC Integrated Circuit. A silicon chip containing the functionality of an electronic component.
IPC Association Connecting Electronics Industries. A trade association providing PCB standards and other useful resources for the 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 finished 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 finished PCBs. Class3 is a performance class for “high reliability electronics products” (this classification usually has a cost impact).
Laser via A plated via hole drilled by laser (CO2 or UV or combined), typically between only two layers, for example a 100u diameter hole between layer 1 and layer 2.
LDI Laser Direct Imaging. A method for exposing a PCB pattern with excellent accuracy by laser beam (no films needed).
LPI, LPISM, LPISR Liquid Photoimageable solder mask, Liquid Photoimageable solder resist.
Microvia Synonym of laser via (the IPC definition includes small via made 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
ML Multilayer PCB, with more than two conductive layers.
MOT Maximum Operating Temperature
MSL Moisture Sensitivity Level. Defines the max floor life and soldering conditions. For details see standard IPC/JEDEC J-STD-020  (rigid PCBs are mostly close to MSL3 in lead-free soldering).
MOQ Minimum Order Quantity (in pieces). Defined as the minimun possible order quantity in pcs at the certain price.
MOV Minimum Order Value (in currency). Defines the minimum possible order value.
NPTH Non-Plated Through Hole. A mechanically drilled hole through the PCB, no copper plating.
ODB++ PCB document database including all the necessary data for PCB manufacturing.
OSP Organic Solder-ability Preservative. An organic solderable surface finish to cover component contact areas (Cu).
OZ Ounce. Fairly commonly used to define nominal copper thickness in non-plated PCB layers, for example 1 oz = 35u; 1/2 oz = 18u.
PCB Printed Circuit Board. A non-populated board that provides point-to point connections between electrical components.
PCBA Printed Circuit Board Assembly. A PCB with populated electrical components.
PP Prepreg
Prepreg An adhesive layer between conductive layers (bond ply) in ML stack-up. Will usually turn into the same laminate material during the bonding process. For example FR4 prepreg will become FR4 laminate after pressing.
PTFE PolyTetraFluoroEthylene. Teflon, a dielectric material used for some RF PCBs.
PTH Plated Through Hole. A copper-plated hole that connects PCB layers to each other. Can also be used for component assembly (component hole like a pressfit hole).
PWB Printed Wiring Board. A synonym for PCB (IPC defines a slight difference).
QC Quality Control
QFP Quad Flat Pack is a commonly used SMT IC package that has leads on all four sides.
QTA Quick Turn-Around. Express delivery with a leadtime below standard leadtime.
RCC, RCCu Resin Coated Copper foil. Dielectric for layers for laser drilling, max 75u thick, only epoxy resin (no glass).
RFQ Request For Quotation
RoHS Restriction of Hazardous Substances, EU directive 2002/95/EC, restricting the use of lead for example. RoHS compliant means that the part fulfils the RoHS directive and meets 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 reoccur in repeat orders with the same document revisions.
SIT Secondary Imaging Technology. A combination of two different solderable surface finishes, typically a combination of OSP and ENIG on the same PCB.
Shelf life The time that PCBs can be stored in an unopened vacuum package without compromising the use-ability of the product.
SM Solder Mask, also solder resist. A permanent coating material on a PCB, covering the areas of the PCB that will not be soldered (most commonly green, but also comes in other colors).
SMT Surface Mount Technology
SPC Statistical Process Control
Tooling cost See startup cost.
UL Underwriters Laboratory. A testing organization for fire safety and classification of PCBs like UL94V-0 (flammability and MOT ratings of PCB materials, technologies and manufacturers).
WD, working day Working day is a unit used to describe delivery time. It excludes days off like Saturday, Sunday and public holidays. For example 10wd usually means a delivery time of two weeks (2×5 days/week).