Soldering onto small solid contacts

urban_winter

I've been soldering for years, but mainly on circuit boards. I consider myself to be basically competent. I've been getting frustrated with a recent project because it has some panel mounted components with small, solid tabs - i.e. with no hole. Soldering advice is invariably "make a good mechanical connection before you solder" but I can't think of any way to do this in this case. My most successful approach is to generously tin both the tab and the wire and then hold the wire in place long enough to melt the tinning together, if you see what I mean. It works but is annoyingly finicky. Is there a better way?

U.

LastMantra

I'd just tin both parts and some solder on the iron and just hold in place. 

I don't always do what's recommended with soldering though. I don't like "making a good mechanical connection" usually as it doesn't make the solder any stronger and usually makes it a pain to remove again. Not had any problems so far!

BillDL

I agree.  If it's in a place where the wires are never likely to be tugged, bent or moved you don't really need a mechanical connection in addition to the solder bond.  Lining up the wire at the correct approach angle and then holding the wire and the components still until the solder cools is the hard part.  For jobs like that it is useful to mechanically hold the wire in place with a "helping hands" or similar crocodile clip type gizmo.  If you have space on the leg beyond where you are going to tack the wire to it with solder you can strip extra insulation off and use a small crocodile clip to secure the end of the wire, then just trim it off afterwards.  Alternatively you can bend the wire so that it lines up with and touches the leg and temporarily clip, tie or tape the wire further back to something else like another wire so it stays in place.  If it is possible to line the wire up so that it goes straight onto the leg in the same alignment, a piece of shrink tubing pushed onto the wire before soldering can strengthen the connection after it is pushed forward over the joint and shrunk.  I have a tub of rosin flux that I dip wire ends and component legs into before tinning them.  It makes the solder stick quickly and more uniformly so I don't have to hold the soldering iron against the wire and leg for more than a couple of seconds.

Sporky

The above advice is good.

I'd add that solid end contacts are hard to work with, but it is doable. Back when I did a bit of site work there was a standard connector for camera control that had 8 tightly-packed connectors (maybe 0.5mm apart) with no solder buckets, and in a thermoplastic carrier. Heat them too much and the carrier would melt so the pins would shift and the connector wouldn't work right.

All that in a very small backshell, and you had to get two jumper wires in too. I was very happy when I found little adaptor cables that turned them into a DE9.