TECHNET Archives

April 2016

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Guy Ramsey <[log in to unmask]>
Date:
Mon, 11 Apr 2016 10:51:38 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (50 lines)
yup.
another way, destructive, is to cut the via out of the board to isolate 
it, and prove that the short is in the via. but a good high mag x-ray is 
a good idea.

On 4/11/2016 10:04 AM, Stadem, Richard D. wrote:
> If you have determined that the via in the picture is the culprit, or is very likely the issue, I would start by having a set of really good X-rays performed with a machine such as an Yxlon.
> Iff those X-rays prove the internal short condition, then you have justification for microsectional analysis by a testing house that has experience in this.
> Concurrently, electrical analysis using PWB layer artwork should be able to determine if there is +12V and -12V both in the same area with close approximation to each other. I am assuming the via in the picture is either one or the other.
> If that is the case, it may be a situation of CAF internal to the PWB, which is the only scenario that I can see that would develop over time. But that is speculation at this point.
> To answer your question, the more samples you can provide for the initial X-ray analysis, the better. Two may be enough, but perhaps 5 or 6 will provide more data; at least enough to justify sacrificing one for sectioning. Try to find one that displays gross shorting.
> An initial X-ray survey should cost less, perhaps 2-3K.
> If the X-Rays provide justification, then microsectioning would go to another $3K, depending on the number of cuts/mounts required.
> A good analysis house can give you a good estimate if you were to forward the pictures to them and explain what you are experiencing. They may have other ideas for confirming that the via is the culprit, and in determining the cause. Be prepared to provide the layer artwork. I would get approval from the customer first; there may be security or ITAR concerns.
> And I am assuming the large probe mark in the via is from troubleshooting to locate the short. The problem is, the short could be anywhere. How was it determined that that particular via is the source?
> dean
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> Sent: Friday, April 08, 2016 11:00 AM
> To: [log in to unmask]
> Subject: [TN] Recommendations for Failure Analysis / Root Cause of PCBA Failure...
>
> Good Morning All,
>
> We have an assembly that we build here for a customer that we built for some time, over 2,000 assemblies. There have been some failures that our customer has had field returns with that are beginning to escalate. There have been 12 field failures that we know of. The failures are avionic assemblies that have been in the field ranging from 111 days to 472 days.
> The actual failures are internal +12V to -12V shorts and we need to know why. I have two failed assemblies here. Here are a couple of external photos of a via that shows the short:
>
> http://stevezeva.homestead.com/Internal_Short.jpg
>
> http://stevezeva.homestead.com/Internal_Short_Close.jpg
>
> So my question is, can a lab take these boards and examine them to determine what the root cause actually is from the two assemblies that I have, or does there need to be more samples? What is the range we should expect to pay for this type of analysis?
>
> We're trying to work with our PCB vendor on this issue, but I have also been asked by my boss to pursue this with a third party.
>
> Thanks!
>
> Steve
>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

ATOM RSS1 RSS2