Most IMC failures are actually design issues related to delta CTEs between components and substrates, and to varying degrees. I respect the challenge you have of summarizing the perfect storm of these design issues, alloy factors (including nucleation and brittleness), aging, and incorrect or abusive solder joint processes (including rework)  that could contribute or lead to catastrophic SJ failure.



And yet, we all manage to do this every day in this industry.

Dean



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman

Sent: Wednesday, May 17, 2017 7:16 AM

To: [log in to unmask]

Subject: Re: [TN] IMC Formation Thickness in OSP



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,

>