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January 1997

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Subject:
From:
Pat Kane <[log in to unmask]> (by way of [log in to unmask] (Jack Crawford))
Date:
Thu, 30 Jan 1997 12:38:32 -0500
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Following from the EMPF HelpLine in Indianapolis, prepared by Pat Kane:

The first issue here is that there seems to be a problem with the forming
operation and that is causing problems with the assembly process.  The
usual causes are misformed leads leading to inconsistant coplanarity.  If
its not consistant there is no way for the pick and place to have a large
enough acceptance window to be able to correct and place the part properly.
 I would suggest that once this problem is solved, the opportunity to gain
higher yields will fall into place.
You may consider having the lead forming done by an outside service or
repair and calibrate your equipment to meet spec.  One source we are aware
of is TINTRONICS.  They have this service as well as sell equipment.
Their address is 2122 Metro Circle, Suite A
                Huntsville, Alabama 35801
                205-650-0220
Contact K.C. Ogata
He has another phone # 616-889-4069
Let us know if you require more assistance in solving this problem.
Pat Kane / EMPF
317-655-3673

----------
>Date: Wed, 29 Jan 97 09:52:37 PST
>From: "David T. Novick" <[log in to unmask]>
>Subject: Optimizing for Fine Pitch Devices in SMT
>
>We have been working with a new surface mount line for the past year and
>are happy with the different pieces of equipment.  We process many printed
>wiring assemblies some of which have 25 mil flatpacks and quadpacks
>throughout the board.  We realize that fine pitch is not as forgiving as
50
>mil pitch and through hole technology, especially when the assembly is
>fully automated.  Our challenge is that we produce a large mix of
different
>assemblies, each at low volume, which we must process through the same
>surface mount line (typical batch size 10-25 boards).  This does not help
>when trying to stabilize a process.  One of our biggest issues is
>coplanarity.  In most cases we do not have the luxury of receiving these
>parts preformed and, therefore, must form them internally.  The handling
>does not help.
>
>We are evaluating all factors which have an effect on solder yields in an
>effort to optimize this assembly line.  We are interested in benchmarking
>with other companies in the industry.  My first question is:
>
>What is the typical defect rate from a surface mount assembly line, when
>fine pitch components are involved, considering the narrowness of the
>process window?
>
>And my next two questions are:
>
>What coplanarity reqirement do you impose?
>
>For those doing their own component lead forming, what procedures do you
>use to assure meeting this coplanarity requirement?
>
>Rosaura Corral-Perez
>[log in to unmask]


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