Changes
Added section on PCB markings
*671-9408078 => Thailand Factory 71 - April 1989 (it's a 6128)
=PCB Markings=
There are some markings on some boards that denote the materials used to build the board or adherence to certain standards.
==UL94 Flammability testing standard==
The standard determines the material’s tendency to either extinguish or spread the flame once the specimen has been ignited.
Classifications from lowest (Least flame-retardant) to highest (Most flame-retardant):
* HB: slow burning on a horizontal specimen; burning rate < 76 mm/min for thickness < 3 mm or burning stops before 100 mm
* V-2: burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed.
* V-1: burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
* V-0: burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
* 5VB: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may develop a hole.
* 5VA: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may not develop a hole.
So, a board with a 94V-0 marking is supposed to stop burning after 10 seconds and may drip non-inflamed particles.
Please visit the [https://en.wikipedia.org/wiki/UL_94 Wikipedia page] on the UL94 standard for more information.
==NEMA grade designations==
[https://www.nema.org NEMA (National Electrical Manufacturers Association)] is the largest trade association of electrical equipment manufacturers in the United States, and publishes standards for electrical products.
One of these standards is the Insulating Material Standard, which includes designation for flame retardant materials (FR), like the ones the PCBs are made of.
Examples of NEMA designations include the following:
* FR-2 : Synthetic resin bonded paper. ([https://en.wikipedia.org/wiki/FR-2 Wikipedia FR-2])
* FR-4 : Glass-reinforced epoxy laminate material, typically employing bromine as flame retardant. ([https://en.wikipedia.org/wiki/FR-4 Wikipedia FR-4])
For information on the different substrates used in PCB manufacturing, please check this [https://en.wikipedia.org/wiki/Printed_circuit_board#Common_substrates Wikipedia page].
==Material codes==
There are other codes referring also to materials and their properties, please check the table below:
[[File:UL_Material_Standards.png|600px]]
==Other markings==
There are some boards which have some combinations of letters and numbers surrounded by white dot patterns:
[[File:PCB_White_Dot_Marking.png]]
These may be production line identification markings for quality control.
=Boards=
