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October 2011

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Subject:
From:
Inge Hernefjord <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Inge Hernefjord <[log in to unmask]>
Date:
Thu, 20 Oct 2011 18:34:33 +0200
Content-Type:
text/plain
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Rich,

this question has been up a number of times, so you'll find many answers in
TN's archive.
Basically, there are no real good diagrams, at least I have not seen any,
not even Werner Engelmaier presented any.
Why is it so? It's because of so many 'it depends'. Nono, it's not Dough's
fault, even if many think so..chuckle..

One use to say, that the yield strength is between 20 and 40 N/mm2 and to
get closer, you need know such things as
- time from solidification
- grain size
- test method (most used is annular ring)
- soldering process parameters (how good the chemical reactions were)
- diffused components from the members on which you solder
- adds (usually ppms)
- possibly more details, which I don't remember at the moment.

A thumb rule says that the strength changes from room temperature:
-minus 50 % up to +125 C
-plus 50% down to -55 C

It won't be much better ways, I'm afraid. Yes, there could be, but those who
have spent a lot of money to come closer are not always willing to share.
Let's see if Mr Solder himself got something deeper, i.e. Mike Fenner. He
use to spend most of his time doing safari  trips nowadays, but if we are
lucky, he may be at home unloading souvenirs.

By the way, perhaps not all Netters know how risky it is to hang things in a
solder joint, such as wire bundles, transformers etc. From my time at
Ericsson, we estimated that the time to failure for a mechanically loaded
solder joint is :

12 N/mm2  > 12 hs
 6 N/mm2  >   600 hs
 3 N/mm2  >  3000 hs
 1 N/mm2  >  1,000 000 hs

Not very exact values, but it gives the design engineer a good idea.

TinTin

alias Inge



On 18 October 2011 18:37, Richard Kraszewski
<[log in to unmask]>wrote:

> Can anyone recommend a link to a good table showing 63/37 strength at
> various temperatures?
>
> Thanks in advance.
>
> Rich  Kraszewski / PLEXUS
>
>
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