Lead-Free Solder

Lead-Free Solder – Some of Its Characteristics and Problems and How to Handle It

Since RoHS legislation came into force in Europe, the nature of electronics manufacturing and welding in particular has changed forever. RoHS compliance and lead-free soldering presents many new challenges for companies involved in the manufacture of printed circuit boards.

No one seriously contests that lead-free soldering is healthier for everyone involved in plate assembly, but lead-free solder has some problems. Lead-free solder does not flow as easily as lead solder and soldered joints on a printed circuit board look different on a lead plate compared to a board constructed using lead-free solder.

The first thing you will notice is the lack of top padding on your PCB boards. It is rare to get more than 75% padding on your printed circuit boards.

The second thing you’ll notice is that your lead-free solder joints are not as shiny as the old lead joints you’ve ever used. This is simply a real blend of lead-free solder and should not be of undue concern.

Does lead-free solder melt at the same temperature as lead solder?

Not! Lead free solder will melt at a higher temperature, the exact temperature will vary depending on the solder mix you choose to use. A common blend is 99% Tin, Copper 0.7% and Silver 0.3%. This melts and flows without much difficulty at 275 degrees.

Lead-Free Solder

Preparing to use lead-free solder for the first time.

Who has to use lead-free solder?

Almost all PCB assembly will have to be done using processes without lead.

What about welding equipment?

It is very likely that most of your welding equipment will require replacement or adjustment to prepare you for the unleaded service.

At a minimum, your soldering irons will require new tips to avoid contamination problems, and you may find that you need to replace all soldering iron if you feel you have trouble reaching the new, higher temperature required for lead-free soldering.

Larger welding equipment, such as a wave soldering machine, will probably need to have your solder baths replaced, and you may want to consider replacing the flux you use, since the printed circuit boards you are now welding will also be free of lead.

Solder pots and other manual welding equipment can have your baths replaced or, for a cheaper option, you can try to empty them from soldering, clean the bath and coat them with a layer of rust paint. Once dry, you can fill the bath with a new lead-free solder and you are ready to start welding again.