PCB Design Glossary

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A land or pad is a conductive part of a printed circuit board that is meant to connect to the pin of an integrated circuit.  



Light Emitting Diode.  These are devices that convert electrical energy into light.


Pure substances undergo phase changes at specific temperatures.  Mixtures undergo phase changes over a range of temperatures.  Liquidus is the temperature at which all solids have melted in a warming mixture.

Phase Diagram

LPI Soldermask

Liquid Photo Imagable Solder Mask is the outermost coating on a printed circuit board that sits between the copper and the components -- it's what gives PCBs their color.

Colored SolderMask

LPI is applied as a liquid coat that covers an entire PCB.  Then patterns of light are projected on the liquid and the high energy photons cause the material to harden and adhere to the PCB.

LPI protects copper traces and prevents liquid solder from migrating during the reflow process.



The tops of printed circuit boards and the bottoms and sides of discrete components are often made of a variety of metals or are coated with a thin layer of a metallic compound to make the surface-layer conductive.  These areas can then be soldered or further processed.  


Microchip Technologies is an electronic component manufacturer based in North America.  Among their very popular offerings is the Atmel328P, the main microcontroller in the Arduino.

Minimum Order Quantity

The minimum order quantity is the absolute lowest number of parts that can be ordered at a time.  Below this quantity, the manufacturer or distributor's profit margins are so low, it doesn't make sense to invest employee time or company resources to sell the item.



A net is a network of pads, traces, and copper pours that are electrically connected.  The theoretical resistivity of a net is zero.  Nets can extend from layer to layer through vias, but nets do not extend through components.

All nets should be given meaningful names.




A pad is a conductive copper shape on a PCB that is meant to act as a connection point for pins or probes.


Printed Circuit Boards are made from sheets of material that comes in standard sizes of 12" x 18", 18" x 24", or 24" x 36".  To keep manufacturing costs down, multiple printed circuit boards are combined on a panel during fabrication.  

The entire panel is not available for usable space.  A 1" margin is used for tooling and test coupons.

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