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Some Commen PCB Terms-I&L
Jun 25, 2018
ImagingThe process of taking the electronic data of the circuit patterns and transferring that data to the photo plotter or image device to apply the image to the film. 
Immersion PlatingA plating process that does not use electroplating to transfer various metals to the copper base of a PCB.  Most commonly used to apply Gold or Silver in an immersion process. 
Immersion SilverThe purpose of this silver plating is to protect the copper from corroding as well maintaining its solderability.  It does have a shorter shelf life than some other finishes and must be shipped with separator sheets to prevent tarnishing. 
Immersion TinCommonly referred to as White Tin, Immersion Tin is a chemical process which applies a very thin layer of tin to the copper.  The appearance is mostly white, has a shorter shelf life and is good for tight pitched components.
ImpedanceElectrical impedance is the measure of the opposition (resistance) that a circuit presents to the passage of a current when a voltage is applied in an alternating current circuit. 
Inspection GuidelinesFor printed circuit boards the standard and guidelines that are followed are published by the IPC Association (See IPC).  The primary criteria is based on the document titled “IPC-A-600” which provided the necessary guidelines for the acceptability for printed circuit boards for Classes 1 to 3.
Institute for Interconnecting an Packaging Electronic Circuits (IPC)Primary industry governing body and often, the final authority on how to design and manufacture printed circuit boards.

L

LaminateRefers to the fiberglass material used in a PCB.  Typically in reference to a multi-layer circuit board.
Laminate ThicknessThe thickness of the fiberglass material before the soldermask, silkscreen or finishes have been applied to the PCB.
Laminate VoidA space that opens inside the fiberglass material of a PCB that can be seen with a visual inspection.
LandThe land or pad is the copper area that is designated for the mounting of components to the circuit board.
Laser Photo PlotterAs opposed to a vector plotter, a laser plotter is able to produce very fine lines and dots to create a more accurate photo plot.
Lead Free HASLSimilar in appearance and use as Leaded Solder with Hot Air Solder Level.  Contains a mix of 99.3% Tin and 0.6% Copper.  It may be referred to as SN100CL. The temp at which it flows is around 515 degrees as compared to around 485 for Leaded Solder.
LPI (Liquid Photo Imageable) InkLPI is an epoxy based ink that is applied to a PCB for solder mask or silkscreen through photographic imaging techniques.   The PCB panel is covered in the ink then the image is exposed and developed.  This method allows for a very precise thickness and accuracy for the solder mask application.


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