Re: SMD solder paste

Robin Szemeti - G1YFG

It is a common mix, I've not heard of the particular brand but I expect it will behave just like any other lead-free paste.

My advice would be to use standard 60/40 lead solder for the lower melting point and just place a zig-zag of solder under the device.  The lower melting point will pay dividends.

All I did for mine was to use some liquid solder flux on a cotton bud applied to the device and the slab, a zig-zag of solder in the trough  (See W6PQL's YouTube video) and then slowly heated the 1/2" thick copper slab on the gas ring ... as soon as the solder melted I waited a few seconds and then turned off the burner, gave the device a little shuffle left-right to make sure it was well bedded, and nudged it back onto the pencil marks. I would say it was in the molten state for about 30 seconds.  As soon as it was solidified, I lifted the slab off the ring and put it on the heatsink, easy peasy.

So my advice would be that solder paste sounds like a good idea, but I'd go with 60/40 tin lead.

On Thu, 20 Aug 2020 at 12:53, G0FVI via <> wrote:
Hi all, 
some advice needed! Been given a tube of SMD solder paste with a view to using it for copper spreader on LDMOS amps. This stuff is called 'Easy Print' and composition is 96.5% Sn, 3% Ag and 0.5% CuO (other stuff in there as well, made in Eastern Europe). I'm wondering if it's worth risking using this stuff (anyone else heard of it?). I know this topic has probably been covered before, but alternative recommendations would be appreciated (what are people using?), four LDMOS amp projects on the go here, rather not blow any more LDMOS devices (lost one recently to bias problems)!

many thanks

Andy G0FVI

Robin Szemeti - G1YFG

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