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Subject:
From:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 17 May 2017 11:25:04 -0400
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depends what is the soldering material, what is the solder joint stand
off, geometry... environment required;  thermal shock, thermal cycle, cte
mismatch, size of components, location of components, vib, mechanical
stress of the PWA, drop, etc. etc.  that is why I am not reply... I just
don't know... you need rel test to figure out what is acceptable... (e.g.
QFN large size with high temp operation will most likely left very little
solder left at end of product life... it might be shorten the service life
significantly).
> Hi TechNet! I was holding off to see what folks posted. My question is
> "why
> does it matter?". An industry colleague and I are collaborating on a paper
> that covers "industry soldering myths" and intermetallic compound (IMC)
>  failure is right at the top of the list. Its a true statement that IMCs
> are brittle but, as an industry, we seem to translate/proliferate that
> statement into a solder joint defect. There are very very very few
> industry
> reports/publications of solder joint integrity failures due to IMC in
> product use environments. There are tons of reports of IMC failures
> created
> because of grossly incorrect or abusive solder joint processes which isn't
> the same thing. Victor - my suggestion is to focus on having a correct
> soldering process using acceptable time/temperature parameters regardless
> if its the initial soldering process or a rework activity. If the solder
> process is correct, whatever the IMC thickness turns out to be, it will be
> acceptable.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Tue, May 16, 2017 at 4:58 PM, George Wenger <[log in to unmask]>
> wrote:
>
>> Victor,
>>
>> I haven't seen and TechNetter responses but I'll give you my two cents.
>> The
>> IMC thickness numbers you heard sound much too high.  I think the IMC
>> thickness should be half as thick as those numbers.
>>
>>
>> Regards,
>> George Wenger
>>
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of
>> [log in to unmask]
>> Sent: Tuesday, May 16, 2017 8:35 AM
>> To: [log in to unmask]
>> Subject: [TN] IMC Formation Thickness in OSP
>>
>> Fellow TechNetters:
>>
>>    What is the acceptable guideline for IMC Formation thickness on OSP
>> after
>> 2x rework..   IPC-4555 is still pending.  I've heard of 3-5 microns on
>> first
>> pass and 5-10 microns on 2x RW.   All comments/suggestions welcomed.
>>
>> Victor,
>>
>

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