Hi Pat.

We assemble boards with surface mount componants on both sides and we ask to
our suppliers to hold .6% and most of them told us it was feasable but
TIGHT. (I think the rest of them did not read our spec!).  I agree with you
that 95% of the time the PCB are flat but once in a while....

Just a suggestion: You should get IPC-6012 wich superseeds IPC-276 and calls
for .75% for boards with surface mount componants.

Hope this help!


At 04:48 PM 12/15/97 -0600, you wrote:
>Hello, TechNetters,
>
>I was wondering what others are calling out for flatness requirements on
>double sided boards with surface mount components.  IPC-A-600 calls out
>1.5% but with a caveat that automated assembly and surface mount may
>require more stringent requirements, and refers to IPC-D-275.  The most
>stringent callout in D-275 for a 0.062" double sided board is 0.9%, and
>this is classed "reduced producibility".  If we have, say, an 8.5"x11"
>board with 0.9% bow or twist, I know we'll have difficulty running it down
>our lines.  What are others calling out, and how have your fabricators
>responded?  Some of mine are balking at 0.7%, saying it can't be held
>(would have to be sorted, possibly increasing cost) because of variability
>in the base material.  I think 0.7% is met most of the time, but every once
>in a while...
>
>Thanks for any input.
>
>*****************************
>* Pat Bailey                *
>* Supplier Quality Engineer *
>* Zytec Corporation         *
>* 1425 E. Bridge Street     *
>* Redwood Falls, MN  56283  *
>*                           *
>* phone 507 637-2966 x355   *
>* fax   507 644-3720        *
>* e-mail [log in to unmask]     *
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--------------------------------------------------
Annie Laberge
--------------------------------------------------
Ingenieure Qualite
Les Systemes Electroniques Matrox

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