Interesting, never heard of changing the electrical properties by baking
under cured FR-4.
If we had low peel or significant change in peel after solder float which
always also had low Tg we would bake the FR-4 for 10 to 12 hours at 345F.
If you have solder on these boards keep the temp below 310F and extend the
time, probably 24 hours. Best if you place a steel plate and some weight on
top of a stack of boards.
Have you had the Tg and UTg checked. If there is a gap in these numbers
greater than about 2 ppm the material is probably under cured.
I do not think you will get any additional cross linking of the resin until
above 285 F for a really long time. Days and days.
Good Luck
Chuck Brummer
Siemens
-----Original Message-----
From: Kaye Clayo [mailto:[log in to unmask]]
Sent: Wednesday, April 27, 2005 12:53 PM
To: [log in to unmask]
Subject: Re: [TN] How to Bake FR4 Boards
Judy
From what I understand, and that is not a lot, hook is when
Er changes with frequency at low frequencies, which changes
the capacitance, which results in distortion of output signals.
If anyone has any other information about this phenomenon,
please enlighten us.
Kaye
At 03:36 PM 4/27/2005, Judy Brown wrote:
>What is a "hook problem"?
>
> Judy
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Kaye Clayo
>Sent: Wednesday, April 27, 2005 12:10 PM
>To: [log in to unmask]
>Subject: [TN] How to Bake FR4 Boards
>
>Dear Technet:
>
>Can someone tell me what temperature and duration
>we should bake some unpopulated FR4 (HASL) boards?
>
>We are attempting an experiment to see if we can "bake" a
>potential problem out of certain boards, but we don't know
>what the baking temperature / time should be. The potential
>problem we are looking to bake out is under cured laminate
>which could be causing a hook problem.
>
>Please help.
>
>Kaye
>
>
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