On Mar 1, 2010, at 10:50 PM, Donald Tillman wrote:
On Mar 1, 2010, at 7:12 PM, Mark Rages wrote:On Sat, Feb 27, 2010 at 5:27 PM, Donald Tillman <don@xxxxxxxx> wrote:Hey folks, What's considered Best Practices for TO-92 packages?Redesign with SOT-23. Easier to solder, faster than stuffing TO-92.Sheeshe...I probably will go to surface mount at some point. But for now I'm kicking it olde school.
If it is for yourself, you might want to try DJ's soldering challenge boards.
<http://www.delorie.com/pcb/smd-challenge/instructions.pdf> I also practiced on broken motherboards, for rework and such.
This particular project uses some analog IC design styles implemented with hand-matched discrete transistors; diff amps, current mirrors and so forth. So I'd need an efficient way to hand- match surface mount transistors. With TO-92's I can just slap them into a rig and collect them into batches. Surface mount? I dunno. Do they even make SOT-23 sockets?
I recall hand matching transistors at various times, and found it rather ineffective, let your parts warm up to operating temperature! The suggestions about using matched pairs in a single package are going to help you get much better results. I had to do my matching to build op-amps and and diff amps from scratch. We matched our transistors really close "near perfect" but it still was not as good as the matched pairs we put in to the circuit as the next step.
As for the statements that we were being elitist in suggesting SOT-23, I did not intend that, in my experience to-92 in a manufacturing environment today is an avoid.
From maneuverability if you have lots of components to populate then your going to need to determine the capabilities of the manufacture house, and those through holes are most likely going to drive your costs up, as a pick and place machine will be able to do the surface mount parts really quickly.
I know that our quick turn houses hand solder the through hole components and like charging extra ;-)
_______________________________________________ geda-user mailing list geda-user@xxxxxxxxxxxxxx http://www.seul.org/cgi-bin/mailman/listinfo/geda-user