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July 2013

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Subject:
From:
Rex Waygood <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Rex Waygood <[log in to unmask]>
Date:
Wed, 31 Jul 2013 14:19:04 +0100
Content-Type:
text/plain
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text/plain (158 lines)
I was taught that a random failure is one for which you don't know the
cause. The implication being that there is no such thing as a random
failure.
However pragmatically, I'd log all available data and wait for instance
2 :-) 

rex

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: 31 July 2013 13:22
To: [log in to unmask]
Subject: Re: [TN] Singular 30% Void and Oversize Ball Diameter

Hi Wayne - One of my mentors always stated " a single random failure
does not constitute a trend". It is sometimes hard to convince a
customer of that rationale.

Dave



From:   Wayne Thayer <[log in to unmask]>
To:     <[log in to unmask]>
Date:   07/31/2013 06:27 AM
Subject:        Re: [TN] Singular 30% Void and Oversize Ball Diameter
Sent by:        TechNet <[log in to unmask]>



In  a high quality operation, all failures are supposed to be rare
events. 
 If you don't look at these very carefully and treat them as precious,
they will quickly multiply and overwhelm you.

This means investigation, but as I presume you are pointing out, it
probably doesn't warrant a herculean effort with just one example.  But
it does mean pretty thorough documentation in case it happens again.

Wayne

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kerr, Bryan (UK)
Sent: Wednesday, July 31, 2013 3:04 AM
To: [log in to unmask]
Subject: Re: [TN] Singular 30% Void and Oversize Ball Diameter

Hi Leland

Seems like a random event to me if you are running thousands of boards a
day. Even a minute trace of some volatile material on the ball or PEC
pad could cause this. Perhaps not worth losing sleep over and put it in
the memory banks !

Regards


Bryan Kerr
Principal Quality Engineer
CMA Lab and Process Engineering
BAE Systems Maritime Services
Manufacturing Hillend
Hillend Industrial Estate
Hillend
Nr Dunfermline
Fife
Scotland
KY11 9HQ
01383-836097


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: 30 July 2013 19:18
To: [log in to unmask]
Subject: [TN] Singular 30% Void and Oversize Ball Diameter

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Folks,

We run thousands of boards a day, and almost every one carries a BGA.
We inspect each with inline X-ray.

Last week, we had one single ball to fail for a 30% void and an oversize
diameter.  We contacted the supplier, and they said their process was
incapable of sending out such a defect.

We've never had a void over 5%, and even those are incredibly rare.

What within our process might have caused this, and do you agree with
the statement of the supplier?  How do you recommend we analyze the
failure?

Thanks in advance for your help!

Leland

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