-----Original Message-----
From: joyce [mailto:[log in to unmask]]
Sent: Friday, April 25, 2003 8:46 AM
To: 'Dougal Stewart'
Subject: RE: [TN] Warpage NSTC
Not so much about tech content:
The problem is two fold:
(1) board house should make their capability matrix known to the
designer and provide "guidelines" or "do's and don'ts" prior to the
layout. This should work for long time relationship (such as "marriage"
contracts....). Most of the time, I have to ask for the capability
matrix... 70% of time, it took some time to get it (not sure if it not
exist or it is safe guided top secrete).
(2) designer should select board shop prior to finalize the design, so
it got no potato chips in the bag for future. The design should only
finalized after the board shop signed and reviewed for symmetrical
design, edge clearance, ground plane thickness, etc.etc. (I am asking
for trouble I know... The board shop will come want everything so
"perfect" the designer thinking about quitting the job for good.... The
board shop also want so much safe guide for their own good, so you can
almost forget the "pushed boundary design"...yada, yada, yada).
Only real good friends can get both of them.... But in the real world,
everybody should be "good friend".... Just like marriage, we can not
live with other half, we can not live without the other half...(don't
forget, it is usually called "the better half")... So much for NSTC
now...(just wondering, why Doug is switch to light weighted Dew... No
more sugar coated TechNet? ;-) My 2 cents.
jk
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Dougal Stewart
>Sent: Friday, April 25, 2003 4:19 AM
>To: [log in to unmask]
>Subject: Re: [TN] Warpage
>
>
>I have watched the various responses to this question, and
>basically the problem is it is a BAD design. board layouts
>should always be as symmetrical as possible in terms of
>construction and copper fill. The issue of crossed ply glass
>may indeed be the case. It is most likely to be found in the
>28mil core which will be constructed of 4 plies of 7628 glass.
>The behaviour of this particular dummy core will dominate the
>behaviour of the whole package, and the material should be
>looked at in isolation before looking at anything else. There
>is no mention of the copper distribution or thickness, which
>may also cause the problem if all the planes are concentrated
>in one area (vertical or horizontal). The control of heat up
>and cool down in the press may alleviate some of the issues of
>flatness later, but essentially the design would naturally
>bend like a banana due to that huge dummy core. Dougal Stewart
>
>email: [log in to unmask]
>phone: +44 1896 822204
>mob: +44 7984 629667
>www.pwbsolutions.co.uk
>----- Original Message -----
>From: <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Wednesday, April 23, 2003 8:03 AM
>Subject: [TN] Warpage
>
>
>> Fellow technetters,
>>
>> I am back with the same old problem: bow & twist
>>
>> we are producing a 14 layer , cap lamination board for one of our
>customer
>>
>> the construction is as shown below:
>>
>> - - - - - - - - - - - - - - - - - - -
>> ************************** 3 mil core
>> - - - - - - - - - - - - - - - - - -
>> ^^^^^^^^^^^^^^^^^^^ 1080
>> - - - - - - - - - - - - - - - - - - -
>> ************************** 28 mil dummy core
>> - - - - - - - - -- - - - - - - - -
>> ^^^^^^^^^^^^^^^^^^^ 2116
>> - - - - - - - - - - - - - - - - - - -
>> ************************** 3 mil core
>> - - - - - - - - - - - - - - - - - -
>> ^^^^^^^^^^^^^^^^^^^ 1080
>> ^^^^^^^^^^^^^^^^^^^ 2116
>> - - - - - - - - - - - - - - - - - - -
>> ************************** 3 mil core
>> - - - - - - - - - - - - - - - - - -
>> ^^^^^^^^^^^^^^^^^^^ 1080
>> ^^^^^^^^^^^^^^^^^^^ 2116
>> - - - - - - - - - - - - - - - - - - -
>> ************************** 3 mil core
>> - - - - - - - - - - - - - - - - - -
>> ^^^^^^^^^^^^^^^^^^^ 1080
>> ^^^^^^^^^^^^^^^^^^^ 2116
>> - - - - - - - - - - - - - - - - - - -
>> ************************** 3 mil core
>> - - - - - - - - - - - - - - - - - -
>> ^^^^^^^^^^^^^^^^^^^ 1080
>> ^^^^^^^^^^^^^^^^^^^ 2116
>> - - - - - - - - - - - - - - - - - - -
>> ************************** 3 mil core
>> - - - - - - - - - - - - - - - - - -
>> ^^^^^^^^^^^^^^^^^^^ 1080
>> ^^^^^^^^^^^^^^^^^^^ 2116
>> - - - - - - - - - - - - - - - - - - -
>> ************************** 3 mil core
>> - - - - - - - - - - - - - - - - - -
>>
>> Obviously, we are getting warpage in boards
>> the construction is customer given and he is not ready to change this
>>
>> Are there any solutions to avoid warp in these boars
>>
>> cheers,
>> Madhu
>>
>>
>>
>>
>>
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