Hi Werner - yes, there is always the issue of distribution of gold for the
entire solder joint versus segregation of the gold in a specific location
of the solder joint.
Dave
Werner Engelmaier <[log in to unmask]>
11/24/2010 02:21 PM
To
[log in to unmask], [log in to unmask]
cc
Subject
Re: [TN] Ductile to Brittle transition
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
-----Original Message-----
From: [log in to unmask]
To: TechNet E-Mail Forum <[log in to unmask]>; Werner Engelmaier
<[log in to unmask]>
Cc: [log in to unmask]
Sent: Wed, Nov 24, 2010 11:35 am
Subject: Re: [TN] Ductile to Brittle transition
Hi Werner - I am a bit confused as there is significant published data
demonstrating that 3-5% range will result in the gold embrittlement of a
solder joint and decrease the solder joint integrity. Did I miss a portion
of the discussion?
Happy Turkeyday!
Dave Hillman
Rockwell Collins
[log in to unmask]
Werner Engelmaier <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
11/24/2010 09:00 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Werner Engelmaier <[log in to unmask]>
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Subject
Re: [TN] Ductile to Brittle transition
Hi Inge,
Indeed, the 4% is a 'red flag' without much scientific validity?see
attached columns.
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 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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