Service Life

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.


Dr. Ron

Procurement Puzzles

While I’m pleased to see IPC is taking a stand in urging the US State Department to take a harder line when it comes to the potential export printed circuit board design data, it must have been cause for no small amount of angst in Bannockburn over whether IPC should be involved at all.

To bring readers up to speed, IPC seeks to make clear that ITAR covers PCB designs intended for defense equipment.

While it seems patently obvious that PCB data should be on the ITAR list, it puts IPC in the semi-awkward position. The largest PCB supplier to the US DoD is TTM Technologies, with about $170 million in defense sales through the first three quarters of last year. TTM’s largest shareholder is a Chinese national. And TTM’s COO is on the IPC board of directors.

So does IPC support the continued DoD drive for COTS products, keeping with the Perry Initiative of 1994, which some cite as the beginning of the end for the US PCB industry?* (COTS in effect forces prices to their lowest common denominator, which gives certain offshore suppliers a leg up on their US competitors.) Does it seek to aid the competitiveness of a major member? Or does it put the interest of the multinational members that want the lowest prices, regardless of the potential security risks? What about the potential risk to the US PCB infrastructure? Which of these priorities should take precedence?

*I don’t agree, but that’s a different blog.