Understand, especially with through hole mounting and the problems with
blow holes. But I believe Dewey was talking about SMT. With thin
coatings in a humid environment I'm sure the copper can become oxidized
and create soldering problems. What about moisture after assembly and
prior to say conformal coating?
Rick

>-----Original Message-----
>From:  Alain Savard [SMTP:[log in to unmask]]
>Sent:  Wednesday, March 22, 2000 7:16 AM
>To:    [log in to unmask]
>Subject:       Re: [TN] Baking FR4 boards
>
>There is no actual requirement, it is more of a factual moisture absorption
>effect. Polyimide absorbs water a lot faster then FR4. I don't know of much
>of a problem with using FR4 up to 6 months old. After that we may recommend
>prebake. This is an in-house specification, I don't know of any IPC
>specification for it.
>
>
>
>Alain Savard, B.Sc.
>Chemical Process Analyst
>CAE Electronics Ltd.
>e-mail: [log in to unmask]
>
>-----Original Message-----
>From: Dewey Whittaker
>Subject: Re: [TN] Baking FR4 boards
>
>
>"Howieson, Rick" wrote:
>Out of curiosity, where are these requirements stated?
>Rick
>>-----Original Message-----
>>From:  Dewey Whittaker
>>Subject:       Re: [TN] Baking FR4 boards
>>
>>Alain Savard wrote:
>>
>>> Isn't the 72 hours before bake a requirement for polyimide instead of
>FR4?
>>>
>>> Alain Savard, B.Sc.
>>> Chemical Process Analyst
>>> CAE Electronics Ltd.
>>> e-mail: [log in to unmask]
>>>
>>> -----Original Message-----
>>> From: Dewey Whittaker
>>> 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 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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