Ask Me Anything with Jim Smith

Use this thread to post your soldering questions and Jim Smith will answer on October 4th!

And for anyone interested in a hands-on workshop, Jim will be in Sunnyvale, CA on November 1st and 2nd for his famous Science of Soldering © seminar.

What would you recommend to be sure to meet the J-STD-001 requirements?

Hi Jim! What are common soldering defects, and how can they be detected and corrected?

What are the best practices for soldering and desoldering components on a PCB to minimize damage and ensure a reliable connection?

What are the different soldering techniques commonly used in PCB assembly, and how do they differ? Is there a method you would recommend?

Can you explain the significance of soldering quality and how it impacts the reliability of PCBs?

How do environmental regulations, such as RoHS, impact PCB soldering practices and materials?

Hello Jim. How to choose the best iron? Does expensive mean better?

Hello! In wave soldering, what role do solder masks and selective soldering techniques play in preventing solder bridging and ensuring precise solder connections?

Are there specific considerations for surface mount technology soldering versus through-hole soldering?

I have difficulties with pure indium solder. When hand-soldering THT components into ENIG PTHs I have issues with insufficient wetting, solder waves and solder bridges. SAC305 by comparison shows none of these issues. The indium solder does not have a flux core. I have tried half a dozen of fluxes and different temperatures, but to no avail.
Some of the issues I have with indium solder can be seen in this video (not my video, but the issues look very similar):

Hi Jim. What is your opinion on soldering tin-plated parts?

What flux do you recommend for bismuth tin solder plus ENIG pads plus THT component leads made from steel with a nickel and tin plating?

It seems like simple question but actually comes down to knowing how to solder. J-STD-001 specifies how far from perfect work can be and still be sold. The book is written in legalese and poorly organized. I typically teach J-STD-001 after the Science of Soldering course because it is not possible to work effectively with J-STD-001 without knowing the process science.

The worst defects are invisible caused by overheating components to make solder appear acceptable. Solder will stick to oxidized or contaminated surfaces at soldering iron temperature to produce a defect that looks reliable. Most component failures are caused by overheating components that degrades bonds inside the component.

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You may find this answer self-serving but what you ask is the knowledge provided in the Science of Soldering workshop. Most of what people have been told about good soldering practices is wrong.

That question would require at least a couple of days to answer properly. In general terms, the options are hand soldering, wave or selective soldering and surface mount reflow as the major categories with some robotics options for replacing manual soldering. Each of the approaches requires considerable education, however. I don’t like this answer but it’s honest.

Soldering is the heart of electronics. It is also the least understood. Rules that were devised more than 50 years ago are still being followed today. However, all the components – the PCB being one of the most important – are not at all like the technology of 1950. It is easy to produce a solder connection that will pass inspection but hidden factors may mean that the connection is not only defective but the component was damaged during application of the solder.

Great question and the removal of lead from solder is the least serious issue. When Europe banned lead, our entire business changed. Before RoHS, almost all components were plated with tin or tin/lead and those platings melted during application of the solder. But mixing melted metals (the component plating and the solder) is not soldering. Soldering is a chemical process between the solder and metal that has not melted. Soldering requires more process steps than mixing melted metals. So RoHS ended one of the two platings that melt. Multileaded components today have leads that are so closely spaced that tin whiskers can cause shorts. So tin plating is much less common. The change in surfaces from ones that melt to metals that do not melt is enormously consequential. But the industry continues to follow the same practices with disastrous results.