"They found it to be a gold coffin of comprehension."
I guess that means something in Sweden.
Yours perplexedly,
On 24/11/2010 10:56, Inge wrote:
> Werner,
>
> Thanks for the posting with declarations and illustrations of IMC impact on
> solder ductility etc.
> I'm not a chrystallography guy, nor a thermodynamic freak, so I need some
> further explanation. Have patience with me, please. At my age, the brain is
> not so quick any longer.
>
> If one gradually increases the Au percentage in SnPb, the size and number of
> IMC platelets undergo a increase. The forbidden level is assumed to be when
> you pass 4 wt%. Over that level you get to brittle solder joints. That's
> clear.
>
> If one lowers the Lead content gradually, I've seen that the size and number
> of IMC platelets undergo a decrease until, finally, they vanish completely.
> With other words, if you have just Sn, you can increase the Au percentage
> until you get the much used 80AuSn. In this case you get an extremly fine
> grade, dense and IMC-free solder joint. How come that no AuSn IMCs are grown
> now? Is the reason for IMC growth in SnPb that you have a binary situation?
>
> I'll send a diagram to Steve. An old one which I have been using for 20
> years when speaking to colleagues. Are the figures still actual or do you
> use different data today? From these graphs, I used to tell people, don't
> feel too safe about the 4wt% rule, things happen to the solder joint before
> that level.
>
> (The diagram is from Dr Willy Beckers at Ericsson, retired since many
> years. He was our solder guru. There is none of his kind today at Ericsson)
>
> 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 can see it,
>> they are needles.
>>
>> Inge
>>
>>
>>
>>
>> Hi Inge,
>> 1. Not a good simile—the steel in concrete only adds strength in tension,
>> not compression, it is not brittle, and it is round; IMCs are NOT
>> needles—they only appear that way when the platelets are sectioned at
>> acute angles; the adhesion of the concrete to steel is very 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 as well.
>> 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 and needles 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 IMCs or 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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Eric Christison
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