Mike,
I had a feeling that if anybody knew what hook was, it would be you.
And to answer your curiosity question, I suppose it was an older
engineer type (I think he is around 30) who read a 1978 Tektronix article
and is curious of how to determine if a board contained hook effect
or not from an experimental approach.
It appears that this is a specific board problem within a specific batch of boards.
Prior to this particular batch, the boards were great. The board vendor said
that no changes were made to the laminate or stack up.
Do you happen to know of a method that you can share to test raw boards for hook effect?
Thanks,
Kaye
At 05:18 PM 4/27/2005, Barmuta, Mike wrote:
>Hi Kaye: AAHHH the infamous "hook" demon has returned. Just out of
>curiosity, did an older engineer type come up with this under cured laminate
>theory?
>I thought it had finally gone away back in the early 80's. The term hook
>comes from the signature or appearance of the phenomena when captured on an
>oscilloscope. It actually dips down and then comes back up giving the
>appearance of a hook.
>
>Without giving out too many secrets I think you will find you cannot bake
>hook out. We went down that road back in the 70's and 80's, used to post
>bake the hell out of it. Didn't make any difference. We even specified "low
>hook" laminate which never truly existed.
>
>The phenomena and effect you are experiencing may truly be related to under
>cured laminate, however hook is usually attributable to improper design as
>opposed to a pure materials issue.
>
>
> Regards
>
>Michael Barmuta
>
>Staff Engineer
>
>Fluke Corp.
>
>Everett WA
>
>425-446-6076
>
>
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of Kaye Clayo
>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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