Hello,
I am not sure how you are calculating the numbers, so.....
If memory serves me correctly you should be taking the percentage of the
long side of the PWB (10.98) to get the allowable. In this case .75% of
10.98" would allow for .082", or for the 1.5% on the 10.98" would allow
for .165". This would be the criteria for the long side.
Then you get into the fact that the IPC issues guidelines, as such design
or process or technology can dictate you use a different criteria. In a
previous life we used 1% until we started using technology and machinery
which called for us to tighten up to a .065%.
Hope this helps
Richard
At 01:58 PM 7/27/01 EDT, you wrote:
>>>>
Technetters,
IPC-6012 indicates that the allowable bow and twist of PCB is .75% for
SMT
and 1.5% for others.
I have a PCB that is exhibits bow and twisting and I want to make sure
that
it is inside of the acceptable parameters.
The board size is 10.98" x 6.81", so the allowable bow and twist would
be:
.75%- 0.561"
1.5%- 1.122"
Are my calculations/assumptions correct?
Any and all advise would be truly appreciated.
Regards,
<<<<<<<<
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