Michael Weal - RD wrote:
> 
> We have had a little problem in the past with placement files.  We were
> providing pick and place files for our vendors for a couple years.  We found
> that we received a couple boards back where two components had been
> interchanged.  After further investigation into this we found that all our
> vendors were not using the pick and place files, but would  "bomb-site" the
> silk-screen for component locations.   With the density of many of the SMT
> boards it is not surprising that a couple of  reference designators could be
> confused.  We have played with the idea of providing "placement gerbers" to
> vendors which would eliminate most of this confusion (reference designators
> could be placed under the components).
> 
> My question is:  What is standard in the industry for most board assembly
> houses with respect to placement files? What do most people provide as
> placement files?
> 
> Thanks,
>      MSW

	This is analogous to the old days when fabricators would bomb-site
	drill info rather than use drill tapes. (now I feel really old!)

	In fairness to the assemblers, often a CAD system's output will not
	differentiate the sides of the board by view, "It's a little difficult
	to install back side parts *through* the board".  We found this to be
	the big obstacle, and once we committed to presenting the data in
usable
	fashion we found it got used (split the two sides apart and present the
	data from the appropriate perspective).

	These days a number of front-end packages are gaining acceptance, these
	tools take input from a number of CAD systems and produce outputs for
	the specific machines on the factory floor (Unicam, Fabmaster,
CIMbridge,
	ADI to name a few).

	The best answer is dialogue with your assemblers, as long as it's a
	containable number of them.  Depending on your CAD system type, there
	are numerous answers to the data transfer problem.

	Another thought would be to produce your silkscreen as normal, but make
	the assembly drawing as the crystal-clear guideline, so that
bomb-siting
	can be done from that.

	Good luck,
-- 
 
      Jeff Seeger                             Applied CAD Knowledge Inc
      Chief Technical Officer                      Tyngsboro, MA  01879
      [log in to unmask]                               508 649 9800

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To subscribe/unsubscribe send a message <to: [log in to unmask]>   *
* with <subject: subscribe/unsubscribe> and no text in the body.          *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************