Hi Dave,
The 3-5% range is a 'red flag' warning based on gross content, but if you have unequal distribution you can get critical concentrations with less than a 4% Au content on average.
Werner
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To: TechNet E-Mail Forum <[log in to unmask]>; Werner Engelmaier <[log in to unmask]>
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Sent: Wed, Nov 24, 2010 11:35 am
Subject: Re: [TN] Ductile to Brittle transition
Hi Werner - I am a bit confused as thereis significant published data demonstrating that 3-5% range will resultin the gold embrittlement of a solder joint and decrease the solder jointintegrity. Did I miss a portion of the discussion?
Happy Turkeyday!
Dave Hillman
Rockwell Collins
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Re: [TN] Ductile to Brittletransition
Hi Inge,
Indeed, the 4% is a 'red flag' without much scientific validity—see attachedcolumns.
There also was a Gerd Becker at Ericsson.
Werner
-----Original Message-----
From: Inge <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, Nov 24, 2010 5:56 am
Subject: Re: [TN] Ductile to Brittle transition
Werner,
Thanks for the posting with declarations and illustrations of IMC impacton solder ductility etc.
I'm not a chrystallography guy, nor a thermodynamic freak, so I need somefurther explanation. Have patience with me, please. At my age, thebrain is not so quick any longer.
If one gradually increases the Au percentage in SnPb, the size and numberof IMC platelets undergo a increase. The forbidden level is assumed tobe when you pass 4 wt%. Over that level you get to brittle solderjoints. That's clear.
If one lowers the Lead content gradually, I've seen that the size and numberof IMC platelets undergo a decrease until, finally, they vanish completely.With other words, if you have just Sn, you can increase the Au percentageuntil you get the much used 80AuSn. In this case you get an extremly finegrade, dense and IMC-free solder joint. How come that no AuSn IMCs aregrown now? Is the reason for IMC growth in SnPb that you have a binarysituation?
I'll send a diagram to Steve. An old one which I have been using for 20years when speaking to colleagues. Are the figures still actual ordo you use different data today? From these graphs, I used to tellpeople, don't feel too safe about the 4wt% rule, things happen to the solderjoint before that level.
(The diagram is from Dr Willy Beckers at Ericsson, retired sincemany years. He was our solder guru. There is none of his kind today atEricsson)
Inge
PS. I forwarded your excellent report to RUAG Space analysis lab.They found it to be a gold coffin of comprehension.
----- Original Message ----- From: "Inge" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, November 24, 2010 12:01 AM
Subject: Re: [TN] Ductile to Brittle transition
> In fig 14 and 15 you say that IMCs are sticking out , and as I cansee it, > they are needles.
>
> Inge
>
>
>
>
> Hi Inge,
> 1. Not a good simile—the steel in concrete only adds strength intension, > not compression, it is not brittle, and it is round; IMCsare NOT > needles—they only appear that way when the platelets aresectioned at > acute angles; the adhesion of the concrete to steel isvery high, not so > solder to IMC.
> 2. Crystal growth at times appears [at least] chaotic.
> 3. I think it is the basic material properties—similar to all crystal> structure—high modulus and little ductility.
> 4. Certainly the presence of the constituent metals is required—Margareta> Nylen in Sweden has shown that when all the Sn was used up in forming> IMCs, no more dissolution took place—elegant experiment; solidification> speed certainly would have an impact, I would think impurities aswell.
> Skoal,
> Werner
>
>
>
>
>
>
> ----- Original Message ----- > From: "Inge" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, November 23, 2010 10:28 PM
> Subject: [TN] Ductile to Brittle transition
>
>
>> Hi,
>> have a few questions on Konstantina's and your report.
>>
>> 1. If you place steel bars or steel nets in the concrete,the strength >> will increase significantly, but the IMC plates andneedles in the >> sollder joint do the opposite. How com?
>>
>> 2. Why are so many geometries created? Large plates, small plates,>> needles, bars, all in a chaotic oder.
>>
>> 3. What causes the predominant brittleness, size of IMCsor geometric >> form or anything else?
>>
>> 4. What is the major driving force to build up the IMC structure,>> percentage of xx in the solder, or solidification speed or what?
>>
>> Inge
>>
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