[EE] lead free solder alloys?

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[EE] lead free solder alloys?

Jason White-20
Hi,

I recently started using some old lead free solder that I purchased from
RadioShack years ago. To my surprise, it didn't "flow" and tended to form
"icicles" from the joint and the soldering iron at both 750F and 850F.
Turns it the alloy was 99.7 Sn (tin) and 0.3% Cu (copper).

Nowadays, what lead free alloys have good working characteristics?

According to a Hackaday articleon the matter - a bunch of patents are
expiring related to lead free solder.

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Jason White
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Re: [EE] lead free solder alloys?

RussellMc
On Wed, 10 Feb 2021 at 07:00, Jason White <[hidden email]>
wrote:

> ... Turns it the alloy was 99.7 Sn (tin) and 0.3% Cu (copper).
>
> An aside: High tin solders are liable to exhibit the dread "tin whisker"
effects - sometimes many years after use, sometimes sooner.


        Russell
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Re: [EE] lead free solder alloys?

Alan Pearce
On Wed, 10 Feb 2021 12:17:08 +1300
RussellMc <[hidden email]> wrote:

> On Wed, 10 Feb 2021 at 07:00, Jason White
> <[hidden email]> wrote:
>
> > ... Turns it the alloy was 99.7 Sn (tin) and 0.3% Cu (copper).
> >
> > An aside: High tin solders are liable to exhibit the dread "tin
> > whisker"  
> effects - sometimes many years after use, sometimes sooner.
>
>
>         Russell

That depends on the alloy. I'll need to dig out my ESA books tomorrow
to check the alloy ratios, but all of the lead free solders have high
tin content. It is the other metals introduced into the alloy that stop
the whiskers. I seem to recall that one combination has something like
2% silver to 90+% tin. There are other traces elements used like
palladium and copper to stop leaching of the same metals out of
component leads and connections.
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