How to avoid/fix solder bridges V3 board

[Homer Jones]

The straight-line layout of transistors just asks for solder bridges. Other boards I've worked with use a triangle layout, which is much easier/safer to assemble. Anyway, I just completed JimStim, and got a bridge across two of the three leads. I fixed it by re-melting the solder and quickly knocking the excess off by tapping the edge of the board on my ESD mat while holding the board vertically. The excess solder flipped off, and the bridge was gone. This is not the way it should be done because the "flying" solder could land somewhere else on the board, and cause other problems. Fortunately, the JimStim board is simple, and easy to inspect for solder splashes. I've never needed a solder sucker before, but I bought one from Radio Shack for possible use on the V3 board I've just started.

I'm using a 15 Watt RS iron with a tip that tapers to a tip-radius of about 1/32" (a little less than 1/16" diameter). I could make it more pointed if you think that would help. My solder is 0.032 - rosin core - low temp. Judging from my JimStim experience, I expect to have problems on the V3 board. I would appreciate any tips on avoiding and/or fixing those little bridges. I have a steady hand, and good lighting, but those little transistors are tricky, and I'm open to suggestions. Thanks in advance. Oh, BTW, this is my first MegaSquirt assemble.

[Homer Jones]

I don't think there is a sure way to avoid transistor bridges, but I think I can minimize them using the following:
1. Use a clip-on heat sink to bridge all three leads right under the transistor body.
2. Once the leads have been inserted, turn the board over and bend the outer leads away from the center one. It will look a little like the letter W.
3. With the leads bent, hold the soldering tip against the outside of the bent lead, and the soldering pad. You'll have more room and better visibility because it is bent. Hold the iron at a steep angle.
4. Wait until their is enough heat to melt solder before applying any. Then, apply a wee little bit of solder to the tip, and let it run down to the joint. If you apply solder directly to the joint, it will probably be too much, and cause a bridge. Do this to both outside leads.
5. If too much solder is applied to the joint, use a wick to remove some.
6. The center lead is the tricky one. If you are going to get a bridge, it will be here. Try bending that lead away from the other two (90 degrees to the plane in which the outside leads were bent).

I'm open to suggestions or comments.

[Homer Jones]

Bridges happen even using the technique outlined in my previous post. I now fix them by remelting the bridge and brushing the joint (while molten) with a small wire brush that was part of a soldering tool kit I found at Radio Shack. They are available from other sources. I couldn't figure out how to include a photo I took of my tool, so here is a link http://toolboom.com/en/Soldering-Aid-To ... 08-361.php
This is a sure way to clean up a bridge, and it does a good job of removing excess flux.

[trakkies]

I use 0.7mm solder, which is much the same as yours, but a tapering conical tip in the iron which is about the same size as the solder at the tip. You also need to see what you're doing, so for most this will need some magnifying. If you have normal eyesight, ready read specs of about +5 dioptres are a cheap way of doing this. If you already have specs, there are various types of over lenses that can be used with them. And plenty light.

Clean to tip before each joint on a damp sponge and tin it with the minimum of solder. Do the centre pin first, then the outside ones with the iron applied to the outside of those.

FWIW, I never mount those transistors tight to the PCB. There's no need to - and if you do you can't then see any solder bridge on that side.

[Homer Jones]

I agree about the need for plenty of light and magnification. I can get by without them on all components except the transistors. For them I put inexpensive reading glasses over my regular ones. I also use an additional light on a flexible goose neck. It allows me to put the light right where I need it. Otherwise my technique is pretty close to yours except I think the tip of my iron is a bit larger than yours, and I've been doing the center lead last. Thanks for the suggestion. I'll try doing it first and look for a smaller tip. Oh, I keep a powerful magnifying glass handy for final inspection. Even with the readers, those things are darn close. Thanks again.

[trakkies]

I have a headset with clip in lenses of various powers. Quite inexpensive - and leaves both hands free.

I also have a vacuum de-solder iron - but they ain't cheap. Before that I used solder braid to remove excess solder.

[Homer Jones]

I have thought about buying something like the image below. I already have loop lenses that clip onto the temple bar of my glasses, but they only work for one eye. That's a little tiresome after a while.