Hi,
I am trying to solder four 28AWG wires onto a USB PCB. The PCB has four plated thru holes. The board is about .095" thick and I am using lead free solder @ 650 degrees F with a HAKKO FX951 and a heavy tip. I cannot get the solder to flow all the way through the thru holes with out having the wire insulation melting back up the wires. Will I need to preheat the boards? Thank you.
Steve55

 

Ideas:
1) use wire that has insulation that doesn't melt back.
2) add shrink tubing over the bare part.
3) don't worry about it. They aren't going to melt back far enough to cause a short.
4) pre-solder the board and insert the wire end later.

 

Thanks for the ideas. I will try #2 but will probably end up using #3. I should have mentioned that the wires are in a jacket. It looks like regular USB extension cable. They would also like me to keep the distance from the cable jacket to the board at 5/16". I tried pre-soldering the holes and it worked great for the first wire, but I don't have the skill to get the other three wires in with out butchering up the insulation.

 

There are some things you can do.

Pretin the wire, so the soldering goes faster.

Often not neccessary but add some flux.

Use a lead solder for lower temp.

Use a broad tip.

All this should work.

 

Clip a heat sink or hemostat to the wire just above the joint area prior to soldering to prevent heat damage to the insulation.

Remember that heat rises. Sometimes you can gain some advantage by orienting the work with the most heat sensitive parts to the side or below the heat source.

 

You absolutely do not need 100% solder hole fill (that's high reliability/mil spec stuff). Just enough to keep/attach the wires there.

 

Thanks to everyone who replied with their comments and advice. This is what I ended up doing. I applied heat with an Aoyue hot air tool to the cable side of the board after the wires were installed. I had to shield the wires with tin foil to keep the insulation from receding. I am very happy with the way it turned out. The company I'm doing this work for wanted to see at least some solder on the destination side of the board.

I used a PanaVise to hold the board and duct taped the hot air tool to the side of the bench. Again, thanks for all the great input.
Steve55

 

you could solder some pcb pins and solder the wire to the pin and sleeve it.....