View Full Version : Tip for soldering triacs
06-22-2009, 12:45 PM
I've always done it, and never thought about it until a friend was over, and asked why I did it that way...
When you are soldering triacs, voltage regulators, and anything in a T-220 package, the long lead sticking out of the board is a VERY effective heatsink. This causes you to put a lot of heat on the lead, for a long time, and still often get cold solder joints.
If you cut the lead off the thickness of the board plus 3/32-1/8", so that about 3/32 - 1/8" sticks out on the bottom of the board, before putting it in the holes, the heatsink is gone, and you can solder the lead in nothing flat. It is so quick, you don't even heat up the triac.
I've been doing it this way for years, and believe me, it can make life a LOT simpler...especially with the number of triacs we have a tendency to solder.
I need to try that. Thanks for the tip.
06-22-2009, 05:53 PM
I have always cut leads off AFTER soldering, mainly because it acts as a heatsink, as well as can be an effective way of holding parts in place by gently bending apart. A quick tug on the lead just prior to soldering can ensure they are straight and hard up against the board on the other side.
06-22-2009, 06:10 PM
On the T-220 cases, you don't want the heatsink...it makes you get the entire lead hot because of the heatsink effect. It doesn't take heat away from the triac - just the opposite. It increases the heat on it. You need to get the whole lead hot enough to solder, which means holding the iron on the lead MUCH longer, which builds up more heat on the triac itself. And heat is it's enemy...
I agree on most components - clipping the leads after soldering. But give my suggestion a try...I think you'll find a lot less time with the iron on the lead, and less heat on the triac.
06-23-2009, 12:51 AM
Using too small of a tip will cause the lead to heat up too slow and cause the part to heat up too much also.
You can compensate by removing the excess material so that it won’t need to be heated too. Use the method that works for you.
I use a large tip set to about 800 degrees.
I have always believed it's best to use high heat for a short amount of time instead of less heat for a longer amount of time.
06-23-2009, 03:59 AM
I set mine to 400C with a fine tip for heavier gear, and drop it slightly for the rest of the soldering.
06-23-2009, 08:36 PM
I have always cut leads off AFTER soldering,
Many years ago, I attended a High reliability Hand soldering Course (HRHS). we were taught to trim the lead prior to soldering.
The tow main reasons were heat buildup in the part, and to get a nice solder fillet and cap over the cut end of the lead.
We used to cut the leads with carbide side cutters, using a length or lead as a spacer, at the finished height before soldering, but after cleaning.
Cleaning was board, lead, tip and solder for each connection. and we had to trim the end off the solder every time to open up the core to allow the flux to run out before the solder melted.
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