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August 2001

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Subject:
From:
David Douthit <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 8 Aug 2001 13:56:50 -0700
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Karen,

Your questions are too generic.

"cracking inside a printed circuit board due to moisture absorption"

1. Is it delamination or cracking? Is it occurring randomly or in certain locations or near
    certain similar patterns/components on the board ( vias, ground planes, large traces,
    heat sinks, BGAs, ...etc)?

2. What type of laminates are involved and the thickness?

3. Are all layers identical materials and thickness?

4. Are you sure it is a moisture problem and not a thermal or contamination problem?
    (correct and accurate profiles)

5. Is this occurring with boards from one vendor or several vendors / same date code or
    different date codes?

There are many variables that must be studied and understood before an answer can be found.
The 5 questions above are just the beginning. You must also consider the cost of
the correcting action. This type of problem can get you from the frying pan to the fire very
quickly. Find someone you trust or get some outside help to go "on site".

David A. Douthit
Manager
LoCan LLC

----------------------------------------------

Karen Walters wrote:

> I am trying to solve the problem of cracking inside a printed
> circuit board due to moisture absorption, temperature in the oven and the
> thermal gradient observed on the board.  After the drying process, the
> boards are left outside
> in the manufacturing area, but due to the environment they are absorbing
> moisture again.  I would like to know which products would fit better(sealed
> bags,vacuum bag,with/without desiccant,low humidity or nitrogen filled
> storage cabinets...).  Also has anyone done a study on moisture absorption
> in a PCB under different environment conditions, and baking requirements for
> different environmental conditions?
> If you have any data, please advise.
>
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