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March 2018

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Subject:
From:
Bob Wettermann <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Bob Wettermann <[log in to unmask]>
Date:
Wed, 28 Mar 2018 15:17:20 -0500
Content-Type:
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text/plain (68 lines)
Very sophisticated customers place limits on much rework (IPC 7711) can be
performed on an electronics assembly. The most common items we see that are
"bounded" by the number of times rework include: BGA or leadless device
(usually 2-3 x max), total number of reworks on the assembly as a whole,
the ability to re-use or not re-use components (like RF shields), the
ability to reball, the maximum number of heat cycles a laminate can
withstand, etc.

Physical board damage (7721) is much more limited in terms of the maximum
number of repairs and is usually approved by engineering on a case-case
basis. (For example, one customer allowed pad repairs but not via in pad
repairs on an assembly)

As previously discussed each assembly is impacted from a  reliability
standpoint based on the materials used, the board layout, the type of
devices populated , etc
. Rework and repair is not a 100% yielding process as the inputs are
unknown and different each time.

Regards

Bob/BEST Inc.

On Wed, Mar 28, 2018 at 12:40 PM, Nutting, Phil <[log in to unmask]>
wrote:

> Respected colleagues,
>
> I was just asked a question to which I could not put a number.
>
> In the case of needing to fix a circuit board "right now" to fill the
> income stream there should be a logical point at which the reworks have
> become too extensive for production boards beyond the "right now" need and
> the board should be revised to eliminate the reworks.
>
> Is there an IPC or MIL standard that suggests a limit on the number of or
> amount of rework allowed on a circuit board before it should be revised?
>
>
> Phil Nutting  |  HVP Senior Development Engineer   |  Excelitas
> Technologies Corp
>
> Lab: +1 978.224.4332   |  Office: +1 978.224.4152
> 35 Congress St, Salem, MA  01970 USA
> [log in to unmask]<mailto:[log in to unmask]>
> www.excelitas.com<http://www.excelitas.com/>
>
>
> [Excelitas R_emailsig]
>
>
> Please consider the environment before printing this e-mail.
> ________________________________
> This email message and any attachments are confidential and proprietary to
> Excelitas Technologies Corp. If you are not the intended recipient of this
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> you.
>



-- 
Bob Wettermann
BEST Inc
[log in to unmask]
Cell: 847-767-5745

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