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Printed Circuit Board Assembly & PCB Design Forum

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PCB Baking

Damian Lai


PCB Baking | 27 February, 2003


I would appreciate some advice / recomendations regarding conditioning of PCB's before use. Our standard PCB's are double sided and rigid multilayer FR4.

We are currently baking everything over 3 months old for 2 hours at 125 degrees C. Is this suitable?

Is there another process that can be introduced to a no-clean process to improve the conditioning of PCB's.

Your help is much appreciated.


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PCB Baking | 28 February, 2003


I don't know what FR4 you are using, so check it out to make sure 125 isn't too high.

I have seen this done occassionally when the PCBs have bad moisture or other problemx where baking helps prior to assembly and solder, yet I haven't seen it done routinely as a matter of course as you note.

I guess it depends on your local, plant environment and your storage facility.

I would be careful about your surface finish that needs to still wet and solder well.

YiEng MA/NY DDave

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PCB Baking | 28 February, 2003

We used to bake [100*C for 6 hours] all of our boards, but no longer bake at all.

Before going off, your bake recipe is probaly OK. If anything, it's probably too short. Consider measuring the weight of wet boards, baking for a time, measure, bake, etc. to determine a proper bake time.

Boards are hydroscopic. If barrel plating is below 1 thou, the absorbed moisture vents through the barrels at soldering temperature. This causes voiding and volcanos in the solder. Both are very tough to rework.

Consider changing the situation to stop this non-value added baking [In fact baking is negative value added, because it makes it harder to solder a good board.]: * Suppliers must provide board with a minimum of 1 thou of copper on plated holes. * Buyers must buy no stop greater than three months in advance of production. * Boards must be stored in a controlled environment [ANSI-J-STD-001: 18-30*C, 30-70%RH]

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