A reader writes:
My company makes an electronic product that requires a 40- year shelf life. We assemble with tin-lead solder on FR-4 PWBs. The product is to replace older technology (i.e. 1960-70s), but has some newer components such as BGAs, SOICs, and PQFPs. The product will be stored in dry nitrogen at 70F. We take great care in manufacturing, by cleaning, inspecting, and testing the end product.
My question is, Do you know of any studies that would discuss the reliability of products stored or in use for 40 years?
My sense is that our reader will be successful, but his question is profound and hard to answer with confidence. The military would like their electronics to perform for that long, but realistically much of it is replaced every 10 years or so. If you look at something like the B-52 bomber, which debuted in 1952, the electronics have been upgraded regularly. So there isn’t as much 40-year electronics experience as one might think. An exception being the IBM AP-101 computer. This computer was kept in service for over 30 years, because it served its function and had survived the rigorous and expensive military qualification testing.
However, anecdotal data might support optimism for 40-year shelf life. In a class I teach at Dartmouth, The Technology of Everyday Things, I have sought out some old transistor radios from the late 1960s and early 70s to show the class how this old technology works. Anytime I have every found an old device like this, they always work, unless the batteries have leaked inside the radio.
This question raises an interesting thought. Although those of us in electronics assembly are concerned with tin-lead and lead-free solder joint life, what about the modern devices inside the components? Forty years is a long time. How will the 3D-22 nanometer copper circuit lines in a modern microprocessor hold up over this amount of time? These circuit lines lines are so fine that the 22nm width is only about 70 atoms. In addition, copper integrated circuits are still a relatively new technology. I’m sure much accelerated life testing has been done on such circuits, but would such testing confirm 40 years of shelf or service life?
I would appreciate any thoughts that readers have on these questions.
For the past five years we have been doing accelerated aging tests for the Army on lead free versus tin lead solders. Our preferred method of accelerated aging included HALT testing at the IPC TM650 most extreme -55C to 125C at a 60 degree/minute ramp rate. Not a perfect solution but you could use that to approximate aging. Or maybe visit a salvage yard and look for radios or instrument panels from vintage cars.