Critical Links

Thought I would touch on the subject of lead-free soldering again as you, our Critical Links readers, always provide me with an interesting response. Whether we like it or not, and even allowing for the unsatisfactory way that it arrived and the lack of life-cycle assessment before lead was banned from solder, it seems that lead-free soldering is here to stay.

A few days ago, a UK customer wrote to me detailing their lead-free experience.

“A couple of years or so before the deadline for going lead free, we began experimenting with the use of lead-free solder.  At that time, the biggest problem going entirely lead free was the lack of information available. So one had to assume that lead-free resistors and capacitors were not available.

The initial finding was that lead-free soldering (all hand soldering in our case) was more costly. For example, $50 for the lead-free equivalent of a $30 reel of 60/40, and $10 for lead-free plumbing solder. Soldered copper pipe joints are easier and better with lead-free.

Electrical soldering took longer than with 60/40, and it helped to use extra flux. Soldering anything larger than 0.5-mm² cables was almost impossible, and lead-free solder would not flow around to the blind side as did 60/40.

The Mec-Seal coating on PCBs is excellent, and makes soldering easy. But it is easier to get dry joints which look OK than it was with 60/40 because the component lead is not adequately wetted.  When soldered, the mechanical strength of the joint seems better with lead-free solder, suggesting better reliability.

When unsoldering items, this is much harder than it was with 60/40 because of the much longer time needed to get heat to flow from the soldering iron bit into the harder solder. A drop of 60/40 helps a lot here, bridging between two convex surfaces.  Even then, working lead-free is a much slower process.

While lead-free works well on a new circuit board, I have concluded that there is a case for tin-lead solder for any situation where you have to solder something in a hurry, especially when jointing cables.”

So, what do you think, does lead-free suggest better reliability?

Are you becoming more comfortable with the process and what challenges have you faced?

As always, I would be delighted to hear from you. Post your comments below.

About the author
As director of legislation and environmental affairs, Gary Nevison is Newark's and Farnell's spokesperson and customer interface on legislation that affects the electronics industry, such as the ROHS (all variations around the world, including China ROHS), REACH, EuP, and WEEE directives. For more on Gary, click here.