When I started, we were building microcontrollers in P-well cmos. It was very prone to latch up. I had problems on the tester with bondwires melting due to latch up. The ceramic parts would be dead after that, but the plastic parts would recover. The bond wire would melt and reform when it cooled. It took some work to figure out what was going on. Once I decapped a ceramic part, I knew.
I remember substrate SCR latchup, all right. I tend to be a little more paranoid about designing the circuit to be robust against that kind of problem in the first place. Carefully placed TVSs, clamp diodes, minimizing inductance from the chip to the ground plane, sometimes Faraday cages and eddy current shields to stop electric and magnetic fields from getting in, that sort of thing. I've salvaged a good many product designs with EMI hardening modifications.
Perhaps if the VP had talked to the engineering guys instead of going past them, the problem would have been seen before it happenned.
I can't help thinking that in an antistatic environment, the conveyor belts themselves should be antistatic and there should be one or more dedicated discharge roller(s) that are verified as working. But then the former may already be true and if the rollers were all supposed to be conductive, maybe my thought is unreasonable.
Guys, you're trying to defend the indefensible. Yes, the conveyor manufacturere did what he was asked for. He probably didn't know what the conveyor was to be used for and even if he did, he's a conveyor guy, not an electronics guy.
And yes, the Veep has every right to ASK if the bearings can be made quieter. Unless he was an engineer (sounds like he wasn't) he should have ASKED about it and deferred to the opinion of someone who WAS an engineer and knew what the project was about.
I agree we don't have ALL the facts here, but with what we do have, it does sound like the Veep was interfering in the project without consulting anyone who was running it.
And that is a total no-no.
C'mon be fair guys...
From the story related here, the VP did not say something like "change to insulated bearings" or specify any particular bearing. He said "make the noise go away" and the belt manufacturer replaced the bearings with insulating ones.
It would be perfectly valid for the VP to assume that the conveyor engineers would change the noise without changing other operational parameters. After all, anybody that has been building conveyors should understand the issues of static (even in non electronic industries) and if they change the bearings should then design in new grounding paths.
I'll put the blame squarely on the conveyor engineers.
In any industry, the only people that never screw up are the people doing NOTHING!
DM has a good point. I too would not be so quick to ID the VEEP as "the enemy...", to paraphrase the Author. If it came down to nixing the grounding option due to cost, assuming the conveyor vendor offered such an option with their nylon bearings, then yes, a rotten fruit barrage of the VEEP is justified. On the other hand, the request for a quieter conveyor may have been out of genuine concern, or even acting on suggestions from the line staff, to reduce noise stress on line personnel. Whether EE or not, the conveyor grounding issue may have been missed if it is not a common knowledge kind of point in the EM industry. Perhaps the VEEP is guilty of not consulting the line manager before requesting the nylon bearings, but I hate to say, EE's do not have a monopoly on collaborative and consesus thinking either.
And if the senior VP knew -anything- about electronics, he would have thought twice before changing to insulating bearings on a conveyor for sensitive electronic assemblies.
As above, this is why I call them PSMs....
While I have a dim view of "senior" management, the moral of this story seems to be complexity and compartmentalization.
The Sr. VP only knew the original bearings were noisy, and asked for quieter ones. He had no idea why the original design was spec'd as it was. (And in fairness, why should he? Not his problem.)
The conveyer manufacturer had the specs, but had they been told *why* those particular specs were given? They just filled the customer's order. So when the Sr. VP complained about the noise, they changed the bearings, blissfully unaware it would cause problems. You can argue that someone on their end should have raised a query about it, but hey, a Sr. VP at the customer site changes the specs...
Problems occurred because each group knew only it's particular piece of the puzzle, and no one with an overview was in a position to say "Wait a minute!" when the Sr. VP meddled.
Good detective work, indeed! And isn't it interesting how those who should stay away instead cause problems by making changes that are certainly not backed up by engineering. It is even more fun when they keep it a secret. It sometimes demonstrates, at least to those who can learn, that engineering design is far more than just drawing straight lines and doing neat lettering.
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