Selective Soldering Tips: Dwelling for Better Hole Fill

This is just one article in a series of articles discussing tips and tricks for using a selective soldering machine. Here at Worthington Assembly Inc. we have a selective soldering machine manufactured by RPS Automation. Our particular model is a 2010 Rhythm model. These article are written by the same person who's used this machine every day for over a year. Some of the parts our customers ask us to solder can absorb a lot of heat. And I mean a LOT of heat. One particular part that we solder has 16 solder joints, is made completely of metal (not sure what but it seems like a tinned copper), and nearly every pin sits on an enormous ground plane. Not to mention, the holes are by no means oversized to make this any easier. Needless to say, it gave us some trouble.

We tried using a local spot preheat. This helped a little but at the end of the day, that solder still did not want to flow up through that ground plane. So we thought, why not just sit there with the nozzle. Turns out, that was the trick.

It's fairly simple really. Using RPS's software we just added an extra point at the four pins that absorbed the most heat. Then we just add a couple seconds of dwell at each point.

Selective Soldering Tips: Dwell for Hole Fill

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This worked like a charm. You can actually watch from the top of the machine as the solder climbs up the joint. It happens slowly, but once it makes it all the way through you can see a beautiful solder joint remains.

Dwelling on specific points will add to your cycle time obviously. But in an effort to make the best product possible, it's a small price to pay.

As always, if you have any questions, feel free to give me a call or send me an email.