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First, we asked you to send in your questions for Happy Holden and Joe Fjelstad in our “Just Ask” series. Now, it’s Eric Camden’s turn! A regular SMT007 columnist, Eric is a lead investigator at Foresite Inc., an analytical testing and consulting laboratory. As a reliability expert, Eric has worked with many large OEMs and contract manufacturing companies to optimize their manufacturing processes and assist with the identification of electronic hardware failures utilizing various analytical techniques. He also specializes in optimizing PCBA processes and identifying hardware failures through analysis. We hope you enjoy “Just Ask Eric.”
Q: How can I pick out the right lead-free solder for my application?
A: That’s a great question. It’s one I regularly get regarding choosing solder and other process materials. As with most questions like this one, the first answer is always, “It depends.” It depends on variables, such as end-use operating environment, expected life cycle, which IPC product class you need to build to, etc.
You can refer to the IPC J-STD-001 and the related test methods in the TM-650 for determining acceptance criteria like hole-fill, circumferential wetting, etc., but all those requirements are just a start. You may also need to consider additional testing above and beyond what is in the IPC documents or even on the print.
Depending on the operating environment, you might need to consider extended vibration testing or thermal cycling to determine if the solder candidate is a good option. One of the most important things to consider is the ability of your equipment to process it.
At the risk of painting with a broad brush, almost any solder will probably work, but you must be sure you know how to set your equipment parameters to yield a reliable solder joint. If you use cross-section to determine the quality of the solder joint, you need to know how to make parameter adjustments to correct any issues you might be seeing. Picking the solder is really only one part of the equation.
To submit your questions to Eric Camden, click here.