On Sat, 27 May 2006 05:16:45 +0200, Trevor Matthews
<
trev.matthews@...> wrote:
>
> I've tried a couple of things and here are my results:
> 1) I placed a couple of blobs of paste on my scrap PCB and melted
> them with my soldering iron - success, the flux burnt off, and nice
> shiny paste. Even the paste I did not heat directly did the right thing.
> 2) Heated the scrap PCB in the skillet to about 250C. No change to
> the previous - grey looking surface to the reflowed paste. Took the lid
> off while it was still very hot and there was a puddle of grey surfaced
> paste with a brown/yellow liquid (?flux) mixed in and surrounding it.
> 3) Tried again without the lid on. Noticed at about 120-150C the
> paste seemed to partially melt - there was small balls of bright solder
> inside the grey muck. Over the next 20-30C the balls seemed to
> disappear under the grey stuff. The flux did not obviously activate, no
> fumes. Continued to let the board heat up. Got the board so hot that the
> substrate started to smoulder and the binding glue bubbling out the
> sides of the board. Still no joy. Thought I'd try adding my soldering
> irons heat to the process to see what happened. Flux activated and the
> paste seemed to do the right thing.
> Theory: Skillet not transferring enough heat to the paste. Would it
> have anything to do with the board being unetched????
> Don't know how to fix the problem. Should I try a toaster oven??
> sparkfun.com document lots of problems with melting SMD connectors using
> an oven and I've already tried to hand solder one compact flash
> connector to a board - I'd prefer to reflow it with the other smd
> devices if I could.
> What do those experts out there think???
> Trev
I still think your temperature is too low.
What board material did you use that decomposed?
I don't use a hotplate, so i don't know the tricks there, i use hot air
from the component side.
Maybe try that. You need a hot air gun (preferrably with temperature
control) or some other hot air tool.
The oven could be just as problematic if you cannot get the temperature to
rise fast enough.
ST