Homebrew PCBs

On Thu, 25 May 2006 11:30:00 +0200, Trevor Matthews  
<trev.matthews@ozemail.com.au> wrote:

>  To test my reflow profile, I've been cooking scrap pieces of PCB with
> a small quantity of old RS electronics solder paste on the board to
> check that the solder melts etc.  The paste is best before wk 50, 2003.
>  During these reflows, I heat the board to 225C max.  I have noticed
> that the paste forms a crust on the board, which can be wiped off (as
> per Stefans  suggestion)  but am concerned about the crust with respect
> to its affect on component joints.
>  Does this crust form on in date paste on component joints??
>  Thanks for your help
>  Trev


Ok, this crust must be different from the one i described when using  
plumbing paste for tinning.
Does it seem to contain tin particles or is it flux?
Will it reflow fully if you crank up the temperature a bit more (maybe try  
with soldering iron if the skillet doesn't go higher).

I also use old SMD paste, it seems less tacky and harder to apply, but it  
doesn't form a crust. I don't really think the old age is the problem.

Not sure.. but my gut feeling tells me your might have too low temperature.

Thanks for posting on list, i'm sure you'll see the benefit of other  
people respondingn soon.


ST