Leo,

It is possible to achieve .5, but the design of the bare board has
to have balanced construction, fairly uniform copper distribution
on all internal layers, etc.  Suspect the IPC has not ventured into
this area because meeting tighter bow and twist requirements is so
design dependent.

Regards,

  Karl Sauter, Staff Engineer
  VLSI/Advanced Component Engineering
  Sun Microsystems Inc.
  (650) 786-7663


> Date: Wed, 2 Apr 2003 15:10:36 -0100
> From: Leo Lambert <[log in to unmask]>
> Subject: [TN] Warp and Twist
> X-To: [log in to unmask]
> To: [log in to unmask]
>
> Hello folks:
>
> Received this comment from one of our customers and the problems they have
> with boards that meet the warp and twist requirements of 600 but still are
> problematic in the manufacturing operation. The equipment they use is state
> of the art high volume type of equipment which is used by many people in the
> industry.
>
>
> We are looking for comments and facts relative to this happening with other
> manufacturers, and whether or not enough information exists to request a
> change to 600 and to provide product which is compatible to existing
> manufacturing processes.
>
>
> When we receive fabs for our complex SMT assemblies that are barely in spec.
> We still cannot use them to build without great difficulty. From Screen to
> reflow we have issues. Is anyone else wishful of a tighter spec? I can
> require a .5 for our specific boards, but if I were to suggest .5 to IPC,
> would I be unfairly restricting the fab houses?
>
> Looking forward to your comments.
>
> Leo Lambert
> EPTAC Corp.
> 71 Route 101 A
> Amherst, NH. 03031
> 603-673-7822
> www.eptac.com,
>
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