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Baking PCB's before Assembly

Greg denham

#4829

Baking PCB's before Assembly | 24 February, 2000

Does anyone have any information on baking boards to remove moisture before reflowing and waving assemblies? I've been told that we should do this to stop such problems as delamination of boards, blow holes, solder balls, etc. I don't know have any evidence for or against this procedure. Can someone shed some light on this.

Thanks,

Greg Denham

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Travis Slaughter

#4830

Re: Baking PCB's before Assembly | 24 February, 2000

Baking boards, especially multi layer, will help with blowholes and delimitation, but not with solder balls. Normally about 120c for 1 hour or so is sufficient. I usually will not go to this trouble unless a board has proven to be a problem or if there is a reason to suspect it might be.

Hope this is some help,

Travis

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#4831

Re: Baking PCB's before Assembly | 25 February, 2000

Greg,

If you are having a problem, i would first check board manufacturers process. Also are they shipping boards to you in seal packages (a must if you are in a humid part of the country.) Most of the time with a few simple process controls moisture will not be a problem.

Thanks, Roger Scalia

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#4832

Re: Baking PCB's before Assembly | 28 February, 2000

We just got a lesson on the effectiveness of heat sealed metalized vapor barrier bags. A customer sent us two bags of 100% saturated PBG components by air freight. This was for a demoisturizing test. When we found the devices 80% dry when they arrived. They were only in transit for approximately 20 hours. The spec for these bags is 0.026 grams/100 hours square inch per 24 hours.

Stu Leech

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