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June 2004

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 11 Jun 2004 14:06:29 -0400
Content-Type:
text/plain
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text/plain (152 lines)
I have been watching this thread with interest because I, as quality manager
at a former employer, lost a debate over this issue. Dewey's is the first
one of the post to allude to risk.

Daan said the part was expensive. There are all kinds of expensive. How
about we need to remove and replace these parts or shut the line down,
because they have a 26 week lead time?  How about $5000 per part?

So, risk, let's get real here. How many thermal excursions, through reflow,
can the component take without sacrificing a significant portion of its
life?
Dewey is right again, it depends.

But, I don't think the questions are that tough. How well did the EE derate
the component (Will we run the crap out of the part)?

How difficult is the part to remove? Do we have the right tools to remove
the part without huge thermal gradients on the component? Does the design
permit easy removal?

What are the package materials? Ceramic . . . Plastic?

Easy rework + good design + solid package = low risk

Here was my experience, as an OEM / EMS: We removed many hundred processor
ports from a customer's board (40 pin plastic DIP). Installed new ceramics
into their product (a noise immunity issue).
We installed the removed plastic components in our product, with a 10 year
warranty. There was a 56 week lead time on the component and we were about
20 weeks short (This was before JIT). I thought they were nuts. It turned
out to be work the risk. I never saw a single return attributed to that
component.

I do think Bill had an interesting point, the board. Don't forget what
happens to the PWB during a rework cycle. I personally think there is more
risk to the board than the component. But, Daan's asking about recovering
components from boards that are known bad, delaminating.

Daan's problem is to find a reference that suggests the components can
withstand rework. It will be buried in the design specifications for the
package. It will not be public and they will not be part of and IPC industry
consensus.


> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of
> Whittaker, Dewey (AZ75)
> Sent: Friday, June 11, 2004 12:22 PM
> To: [log in to unmask]
> Subject: Re: [TN] Reusing desoldered components
>
> Bill,
> This question is perfect for Doug's patented answer " it
> depends". Can you or have we made a case where it is
> acceptable to re-use components? Yes.
> Should you, if you have to ask, re-use components? No.
> Knowing your end-use requirements and environment is a must,
> but just the time and money to read and gather all the things
> you need to consider before making a decision will probably
> exceed the cost to scrap initially.
> Dewey
>
> -----Original Message-----
> From: Kasprzak, Bill (sys) USX [mailto:[log in to unmask]]
> Sent: Friday, June 11, 2004 8:17 AM
> To: [log in to unmask]
> Subject: Re: [TN] Reusing desoldered components
>
>
> Daan,
>
> Our policy is to not re-use any soldered parts. I've tried to
> rationalize situations instances where this would be
> feasible, such as prior to powered up conditions, but can't
> win support due to a lack of proof that parts are not over-stressed.
>
> Pragmatically, I think there should be some guidelines for
> re-using parts, limited to prior to powered up conditions.
> The same pundits who argue that re-use of parts is verboten
> don't seem to have a problem re-using a board from which
> parts were replaced.
>
> Bill Kasprzak
> Moog Inc., Systems Group, Process Engineer
>
>
> -----Original Message-----
> From: Dobbs, Marie [mailto:[log in to unmask]]
> Sent: Friday, June 11, 2004 10:34 AM
> To: [log in to unmask]
> Subject: Re: [TN] Reusing desoldered components
>
>
> Our rule of thumb.  If it is removed it is replaced.  We have
> never conducted any studies on potential heat damage, but.
> Better safe than sorry.
>
> -----Original Message-----
> From: Dehoyos, Ramon [mailto:[log in to unmask]]
> Sent: Friday, June 11, 2004 10:27 AM
> To: [log in to unmask]
> Subject: Re: [TN] Reusing desoldered components
>
>
>         Hi Daan:
>                    I am not aware of any standards for
> recycle parts, but wouldn't these parts be  in the same
> situation as reworked parts? Some times there is a need to
> move  parts due to misalignment or for trouble shooting.
> This requires them to go through the reflow process. Just my one cent.
>         Regards
>         Ramon
>
> -----Original Message-----
> From: Daan Terstegge [mailto:[log in to unmask]]
> Sent: Friday, June 11, 2004 7:20 AM
> To: [log in to unmask]
> Subject: [TN] Reusing desoldered components
>
>
> Hi Technet,
>
> We've recently had delamination problems on boards which are
> populated with some very expensive QFP's. To minimize the
> damage we want to desolder these parts and use them again.
> Our customer wants some kind of evidence that the
> functionality and long term reliability are not affected, and
> they want this evidence (i.e. thermal profiles) to be related
> to IPC specifications.
>
> I'm not aware of any standard that specifies if reuse of
> desoldered components is allowed, and which limitations apply
> to the temperature profiles, but perhaps some of you knows
> such a standard ?
>
> Best regards,
>
> Daan Terstegge
> Thales Communications
> Unclassified mail
> Personal Website: http://www.smtinfo.net

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