Inge,
Indeed,some of the IMCs in these figures are needle-like, but I am not at all sure they are SnAg-IMCs. They could just as well be Cu6Sn5, which has not shown to embrittle the solder structure.
Werner
-----Original Message-----
From: Inge <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Nov 23, 2010 6:01 pm
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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