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September 2001

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Subject:
From:
Jack Crawford <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 19 Sep 2001 09:57:34 -0500
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>>> "Charles McMahon" <[log in to unmask]> 09/18/01 07:00PM >>>

Hello All:

In response to the issues for short-run assembly, I have found that each
assemblers profile status is a moving target based on the particular
expertise and equipment of the supplier. In my experience I have found the
primary cause for re-work is the paste method application & ste4ncil along
with the calculation of dwell time at reflow etc.

I believe that this variable is the cause of most of the re-work incidences.
If we can control the paste factor, we would
have a material impact on the result in my view. With that said, are there
any opinions on the PPT technology (precison pad)for controlled paste
deposition that is now being introduced? IMHO it appears this could address
the short run issue specifically. And, as a board/assembly supplier
providing DFM services, it would have a demonstrable benefit for the
customers I serve.

Any opinions are respectfully solicited on this process.

Charlie McMahon


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jack Crawford
Sent: Tuesday, September 18, 2001 4:39 PM
To: [log in to unmask] 
Subject: Re: [TN] SMT Process Validation


>>> Barry Gallegos <[log in to unmask]> 09/18/01 03:08PM >>>
Rich,
We too are in this same boat. If you find an answer, please would you share
your findings.

Barry Gallegos
Process Engineer
Western Electronics
1550 South Tech Lane
Meridian, Idaho 83642
Phone: 208/955-9771
Fax: 208/955-9755

-----Original Message-----
From: Jack Crawford [mailto:[log in to unmask]] 
Sent: Tuesday, September 18, 2001 12:20 PM
To: [log in to unmask] 
Subject: Re: [TN] SMT Process Validation


>>> Rich Lasko <[log in to unmask]> 09/18/01 12:56PM >>>
Good afternoon everyone,

We have been doing some smaller qty prototype or very low volume production
runs (Qty 5-10pcs) on our SMT equipment.  We have been encountering some low
yields at the SMT inspection for this type of production/prototype runs
(They are nearly fixing each board for some reason or another).  The
feedback that I am getting from that department is that they can not
accurately "tweak" the process with this low number of qtys (by the time
they get close to having the machine programs set, they have completed all
the boards in that order).  So the next time we run the job, we continue to
"tweak" the process in order to improve the yields.

What this has caused us is some continuous rework at the end of the SMT line
repairing the slid, shifted, or tombstoned components or incomplete solder
reflow.

Have any of you encountered a similar type experience and if so how was it
handled in order to improve the yields?

Thanks in advance for your help on this matter.

Rich Lasko
Badger Electronics

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