[TriEmbed] need stupid pet trick immediately

Pete Soper pete at soper.us
Wed Oct 15 15:56:51 CDT 2014


Thanks very much to all!

As of now I'm getting stupendously better performance from the T-962 
oven than what I was moaning about Monday night. Cutting out air leaks, 
propping the boards up with a air gap over the drawer metal, and making 
a custom profile that lies and compensates for the profoundly messed up 
reckoning of time of the oven have combined to make me pretty happy 
about the future with this ($#Q!!$$@$$@!), uh, inexpensive Chinese 
reflow oven.

Here are the readings from three thermocouples on three corners of the 
the synchronous counter board I'm preparing to solder. This has 10 
74HC192 and three 74HC373 chips plus 13 bypass caps. (TSSOP chips and 
0603 caps). The soak-time ramp rate is very fast compared to the 
(straight line Kester recommended) profile, so I need to do some more 
tweaking, but it isn't clear how much difference this will really make. 
The peak temperature is a bit high, but there's some margin to play with 
there wrt what the components can stand (I'm using plain solder and 
they're all designed for lead-free these days). Degrees C on Y, elapsed 
seconds on X.

http://triembed.org/blog/wp-content/uploads/2014/10/20141015-thermoleads.pdf

But to give you an idea of where things were earlier, here are 
measurements with the same thermocouples (plus one that obviously popped 
loose) while a little breakout board was being soldered. The orange dots 
show the timing and temperatures that Kester recommends for the solder 
paste I'm using. The oven was super-slow warming the boards up and held 
high heat (or feeble, too-low heat) for very long periods, then cooled 
the boards way way too slow. Other than that the performance was 
spectacular.

http://triembed.org/blog/wp-content/uploads/2014/10/2014-10-05-T962-Actual-With-Text.jpg

   And yet the tiny board in the middle of the drawer soldered well 
enough that it works.

-Pete




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