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Subject: [Homebrew_PCBs] Solder paste refolw - why to preheat

From: Stefan Trethan <stefan_trethan@...>
Date: 2003-10-01

Hi

I finally could convince myself to buy a steinel heat gun (the good one
with lcd and feedback controller markus suggested). It is a good unit and i
searched the web for some information on reflow soldering (repair with heat
gun etc.).
So i found the following, if you are interested in reflow, either hand
applied or oven, read this:

http://www.howardelectronics.com/desoldering_update.html

it says why the preheat is needed (vaporize the solvent in soldering paste
BEFORE solder melts
or you end up with small "explosions" and drops over the board).

it also shows a chart for reflow temperature over time (helpful for making
a oven).

the total soldering time is about 6 minutes.. i did assume a much shorter
time (if you take the 3 seconds stated in the most datasheets).
Maybe this is because the part is only over the critical temperature for a
very short time, not the whole
6 minutes, maybe there are other reasons. anyways i find it very long.

stefan