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From:	"Erich Heinzle (a1039181 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Date:	Thu, 23 Mar 2017 08:45:32 +1030
Message-ID:	<CAHUm0tOOZm8RoJgi37PyObp71bJtxEJ3=dWFwVWvgNUyJDNcdg@mail.gmail.com>
Subject:	Re: [geda-user] handsolder QFN packages
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I've had success reflow soldering with a simple lift-off jig made from
bits and pieces lying around to gently lift the reflowed board away
from the hot plate at around 280 seconds.

The key features are a ~3mm thick plate to spread the heat, having the
800W hot plate starting at ambient remain on for 250 seconds, then
turned off, then lifting off the board with the jig at about 280
seconds, to get a really good fit to the recommended JEDEC heating
curve.

http://vk5hse.blogspot.com/2011/05/finishing-off-sdr-cube-transceiver.html

being able to lift the board without jostling at 280 seconds avoids
the problem of thermal inertia of the hot plate continuing to heat the
board longer than necessary. I usually just chock the jig after
lifting it away from the hot plate.

for a tiny board, slightly less than 250 seconds may be sufficient,
and can be judged by the solder paste elsewhere going from grey to
shiny.

I started with a thermocouple, but the process is so predictable you
really only need a clock that shows elapsed seconds.

Cheers,

Erich.

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