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Subject:
From:
"George Franck Jr" <[log in to unmask]>
Date:
Fri, 15 Nov 1996 16:23:18 -0500
Content-Type:
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Ajay,
I am not trying to cause problems for you, but....
I am shocked that your company would continue using a supplier who 
delivers product which averages 40-50% known defective.  Are you not 
worried about the remaining boards on the panel?  If half the boards are 
known bad boards, I would be afraid the remainder were going to be bad, 
but I just didn't know it yet.

The causes for your supplier to X-out one board could be the cause of 
the solder balls/outgas problem on the "good" board next to it.

I would requote the job allowing 2 x-outs per panel, also require a 
minimum of 95% of the boards delivered to be good boards.  Most 
importantly, I would get quotes from 3-4 other PWB shops.  The boards 
may cost more, but look how much money you are wasting on assembly 
yield. You also have twice the handling costs since your panels are only 
half full.  Look at your total cost not just purchase price of your PWB!

My 2 x-out per panel is just a guess in terms of thermal mass.  You 
could also place reusable plastic blocks which approximate the mass of 
the parts on the top of the x-out boards, if you remain sensitive to 
thermal mass.

By the way, I buy boards for my company to assemble, but do not buy them 
panelized due to low volume.

George Franck Jr
Raytheon E-Systems
Product Assurance Engineer
Falls Church Va



On Nov 15,  6:52pm, [log in to unmask] wrote:
> Subject: ASSLY:X-OUT PROBLEM IN PANELS
> Date : 15/11/96 17:49
> Msg From: PROCESS ENGINEERING
> WE ARE MANUFACTURING  SIMM MODULES WHICH ARE IN THE FORM OF PANELS.
> EACH PANEL HAS 10 SIMM MODULES( 5X2). ON AN AVERAGE WE ARE GETTING 4
> TO 5 X- OUTS SIMM MODULES PER PANEL WHICH ARE NOT BEING POPULATED. WE
> ARE FACING THE PROBLEM OF SOLDER BALLS IN BETWEEN THE LEADS OF IC's,
> THIS PROBLEM IS RANDOM IN NATURE(i.e IT VARIES WITH NO. OF X- OUTS IN
> A PARTICULAR PANEL.).
> WE SUSPECT THAT THIS PROBLEM MAY BE BECAUSE OF VARIBLE THERMAL MASS
> IN THE PANELS. IS THERE ANY WAY OF AVOIDING THIS PROBLEM. ALSO IS
> THERE ANY GUIDLINE FOR THE ALLOWABLE NO. OF X - OUTS IN A PANEL THAT
> WILL NOT AFFECT THE THERMAL MASS OF THE PANEL SIGNIFICANTLY.
> 
> REGARDS
> 
> 
> AJAY AGARWAL
> ALTOS INDIA LIMITED
> 
> 

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