[sdiy] Soldering copper to aluminum using indium

cheater cheater cheater00social at gmail.com
Wed Aug 18 08:35:15 CEST 2021


I did hear that indium based solder was more ductile, but at my
scales, the expansion differences of a 5cm plate of copper vs the alu
base plate on a swing from 10 to 90 degrees is going to be 0.03mm,
that's nothing. I think even 60/40 solder should be able to take that
much swing, right?

Putting the heatsink in an oven is a bad idea, the fins would just
straight fall off.


On Wed, Aug 18, 2021 at 1:49 AM peter foti via Synth-diy
<synth-diy at synth-diy.org> wrote:
>
> One of the reasons we were using Indium in our application was that it remains soft and can take up the difference when bonding materials with CTE mismatches. We were soldering glass-like materials to copper.
>
> We were operating at cryogenic temperatures, so the huge swings from 77K to room temp would eventually fatigue the solder joint, but they typically lasted several months of daily temperature cycles.
>
> On Tue, Aug 17, 2021 at 5:54 PM Gordonjcp <gordonjcp at gjcp.net> wrote:
>>
>> On Tue, Aug 17, 2021 at 03:59:49PM +0200, cheater cheater via Synth-diy wrote:
>> >
>> >
>>
>> I don't know about the difference in thermal conductivity, but for this bit you might want to consider getting the heatsink good and hot in an oven.  Do it slowly and let it get to an even temperature right through.
>>
>> Also consider that the dissimilar metals will expand and contract at different rates, and it might just crack itself free after a few cycles of heating and cooling.
>>
>> --
>> Gordonjcp
>>
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