Like David I didn't see any failures that where cause because the IMC was thick. I saw ruptures in BGA solder joints in the IMC after vibrations but these IMCs where not extremely thick. What interests me at the moment is the ongoing miniaturisation. If I look at solder joints of 01005s I see that the entire gap between the component and the pad is only IMC. This means that our knowledge about low cycle fatigue of the solder joints as a failure mode will have to be reviewed since the IMC does not creep but the entire stress due to the CTE mismatch is transferred into the PCB and the component body and we might observe new failure mechanisms such as degradation of the Epoxy, forced rupture of the components etc.
Best regards
Günter
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> -----Ursprüngliche Nachricht-----
> Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Zilber Gil
> Gesendet: Donnerstag, 19. Mai 2016 17:44
> An: [log in to unmask]
> Betreff: Re: [TN] Intermetallic and high temperature operation
>
> Thank you for your advice.
>
> Have a great weekend ,
>
> Gil
>
> From: David Hillman [mailto:[log in to unmask]]
> Sent: Thursday, May 19, 2016 6:22 PM
> To: Zilber Gil
> Cc: TechNet E-Mail Forum
> Subject: Re: [TN] Intermetallic and high temperature operation
>
> Hi Gil - cool! I hadn't seen this data set so I'll be reading it this week. A quick
> glance thru the investigation shows they were documenting the IMC
> thicknesses for a variety of solders for different conditions which could be
> very useful to have for future comparison assessments. The next step would
> be to investigate how these IMC thicknesses interact with different product
> use environments. Thank you for the data source!
>
> Dave
>
> On Thu, May 19, 2016 at 9:54 AM, Zilber Gil
> <[log in to unmask]<mailto:[log in to unmask]>> wrote:
> Hi David,
> Thank you for your prompt response. The paper I found is:
> app.aws.org/wj/supplement/<http://app.aws.org/wj/supplement/>WJ_197
> 2_11_s536.pdf
> 1.
> So for the moment I can tell my boss that we can use the board at 100 deg c
> for years, unless we will find more data that will warn us.
>
> Thank you and best regards,
>
> Gil
> From: David Hillman
> [mailto:[log in to unmask]<mailto:david.hillman@rockwellco
> llins.com>]
> Sent: Thursday, May 19, 2016 4:12 PM
> To: TechNet E-Mail Forum; Zilber Gil
> Subject: Re: [TN] Intermetallic and high temperature operation
>
> Hi Gil - you hit on one of my soapbox topics so I have respond! What data
> source are you citing that shows 6 micrometers of IMC results in solder joint
> failure? And for the IMC, is it the Cu3Sn or the Cu6SN5 phase? The industry is
> constantly "reminded" that thick IMC is brittle and will cause a loss of solder
> joint integrity but where is the data? Everyone is in consensus that IMC
> phases have been shown to have brittle properties but when I push for hard
> data/investigations/studies, demonstrating failures due to excessive, thick
> IMC phase, the real root cause has always turned out to be an out of control
> or excessive, abusive soldering process - typically a soldering process most
> folks would say "ohh, I wouldn't do that with my soldering process". For a
> dwell temperature of 100C, I will grow approximately 5 micrometers of IMC (
> combine Cu3Sn and Cu6Sn5 phases) in 1660 hours using the standard IMC
> equations for tin over copper (my calculations don't match the details you
> listed). There are multiple examples of electronic products in many different
> product use environments that easily exceed that time and operate at that
> temperature yet we don't see reports of product integrity data. Unless you
> have some nontypical variable for your product in its use environment
> (basically, a variation of Doug saying "it depends" but with less gray area), I
> don't believe you have a solder joint integrity concern. Don't get me wrong, I
> think its great that folks are looking at how much IMC phase is
> produced/found on their solder joints but I think we overstate the topic on
> most occasions.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]<mailto:[log in to unmask]
> m>
>
> On Thu, May 19, 2016 at 7:34 AM, Zilber Gil
> <[log in to unmask]<mailto:[log in to unmask]>> wrote:
> Hello Technet`s,
>
> As we know above 6 micrometers of intermetallic (CuSn) could cause failure
> due to brittle structure of the intermetallic. I found in some experiment that
> at 100 deg C after 32 days the intermetallic (CuSn from Sn-40Pb) grow in
> about 6 micron. Is it true? What should I do if the board should see 100 deg C
> for long time and what about >=90 dig?
>
> Thanks,
>
> Dr. Gil Zilber
> Technologiest
> Elta Systems Ltd.
>
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