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Baking FR-4 PWB's prior to reflow

Charles Barker

#4611

Baking FR-4 PWB's prior to reflow | 21 March, 2000

Greetings all you knowledgable SMT persons!

1. Typically, for multi-layer (6-8 layers), FR4, SMT boards stored in an air conditioned environment at about 50+/- 10% RH, how many months (or years) would you allow to pass before you would recommend baking them prior to reflow?

2. What would be your bake cycle?

Thanks,

Charlie B.

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#4612

Re: Baking FR-4 PWB's prior to reflow | 21 March, 2000

Charlie: I�d plan never bake boards. Check the SMTnet Archives. Dave F

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Marc

#4613

Re: Baking FR-4 PWB's prior to reflow | 29 March, 2000

Charlie B: You mentioned that you have an air conditioned environment and a RH 0rf 50, baking the boards is predominately done when the history of the PCB delivery and / or previous storage conditions are un known. When I was with a CM, we did this as a matter of course ( being in NZ, as we don't have the stable contol wrt to Customers boards). Baking is usually done in a temperature changer, with adequate circulation for each PCB and baked at a constant 80 degrees for 12 hours. A similar practise can be performed with micros to avoid "pop-corning)

The other thing I was a bit conserned about is you mentionedyour shelf life of PCBs. How long you can store PCBs is dependant on the finish. From what I understand HASL, 1 year, then they need to be re done idealy, gold flash, 6 months, and OSP 3 months.

I hope I have helped

Marc

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