On the Application of Quantum Probability Tunneling to Improve Manufacturability of Printed Circuit Board Designs: A Case Study
by Rick Cook & Peter L. Manly
Illustrated by Ron Chironna
(Tape recording of interview between Jason Payne and his attorney, Lawrence Fisk, at Federal Jail)
“Yeah, OK, I guess. But Larry, you gotta get me out of here.”
(Unintelligible)
“Dammit, I did cooperate. I told them the truth, just like you said, to get immunity. Yes, the whole truth. No, OK you’re right. It’s just that if that damn Sanchez hadn’t come in to get a cup of coffee…
“No, I guess it doesn’t make a lot of sense. OK, let me go back over the whole thing, just like I told it to them.”
The coffee was a real sore point with us. Some Cost Containment Weenie had noticed the printed circuit board shop used more coffee than the average department and slapped a ceiling on our supply. It did no good at all to point out that we were as far as hell and gone from the cafeteria and we worked all kinds of weird hours. All that got us was a form letter spouting the Cost Containment Credo for Effective Engineering. I was damn glad none of us had digestive problems. If we had, the Cost Containment Weenies probably would have rationed our toilet paper—not to mention flushes.
“I hear over in the main cafeteria they’ve got an espresso bar for afternoon coffee break,” Sanchez said that afternoon when we broke for coffee.
Wilson finished the last of the stuff in his cup and ambled over to the beat-up old urn in the corner of the board shop. “Jeez,” he said as he pulled the handle. “I wish this thing could make espresso.” Then he looked down at his cup and his eyes bugged out.
We didn’t have to ask why. From clear across the room we could smell the sharp, rich aroma of espresso wafting out of his cup.
“What did you guys do to this thing?” he demanded.
“Nothing,” Sanchez protested. “We fixed the heating element like I said.”
Wilson raised the cup to his lips and took an experimental sip. “You sure you didn’t load it up with espresso or something? ’Cause this sure tastes like espresso to me.”
I couldn’t stand it any longer. I went over, got my cup off the rack and stuck it under the spout. What came splashing into my cup was weak, brown, and by no stretch of the imagination espresso.
I looked at Wilson and Wilson looked at me. “Don’t ask me,” he said, “all I did was pour out the coffee. Here.” He pulled another mug off the drain board and tried again. This time he got the same brown junk that usually passed for coffee.
“Maybe you gotta ask it nice,” Sanchez said.
I don’t know why I did it. I mean to this day I really don’t. But I dumped the stuff out of my cup, stuck it back under the spout, said “espresso please” and pulled.
The liquid that filled the cup sure looked like espresso. It smelled like it too when I raised the cup to my nose. And it tasted like it as it burned its way down my gullet.
“Let me try that,” Sanchez said, grabbing his cup off the drain board. But Sanchez, he can’t do anything straight. He puts his cup under the spigot and says “café latte.”
And the thing hisses and spits and he gets café latte.
So there are the three of us, standing around the coffee urn, looking at each other and everyone’s eyes are bigger than his neighbors’.
“Shit,” says Sanchez at last. “A magic coffee urn. We got us a magic coffee urn.”
For once the little bastard wasn’t exaggerating.
If we’d had any sense we would have left it there. We would have kept our mouths shut and we would have drunk our coffee and that would have been the end of it. But we were engineers and we couldn’t leave it there. I mean we just couldn’t. We had this unexplained phenomenon and we had to mess with it until we found out what was causing it—and what else it was good for.
The obvious place to start was the repairs to the urn. A couple of days before the thermostat had gone out on it and we’d haywired a fix with a piece of old circuit board from the scrap bin. It hadn’t even been a working board, just something we’d thrown together with a lot of microwave elements on it and some more-or-less random scribbles. See, we’d been having trouble with the line widths on some of this high-frequency stuff and…
Oh, yeah. Well anyway we had this funny-looking printed circuit board wired into a standard coffee urn. So we stuck meters and probes and capacitance checkers and all sorts of stuff on that board. The readings we got didn’t make much sense; I mean the damn thing was covered with doodles, but we kept at it.
We tried stealing the coffee urn from Drafting down the hall and cannibalizing it to repair ours. That produced the usual swamp water for coffee, no matter what we asked for. Then we took off the unit we’d cannibalized and put the PC board back in place and we got whatever kind of coffee we asked for. (Except Irish. Sanchez couldn’t get it to add whiskey.) We snuck the other urn back into Drafting and settled down to try to make sense out of that damn PC board.
That was especially tricky because at microwave frequencies things go funny and the leads themselves become part of the active circuit elements. So (sound of chair scraping) you put something like this on the board:
and that’s a capacitor. This:
is a transformer. And so on.
No, listen, dammit, this is important. It’s the key to the whole thing.
Anyhow, what was on that board was one part standard microwave components from the CAD library placed sort of at random and strung together any which way, and one part just doodles. But it did something.
And we couldn’t duplicate it. I mean not at first. We copied the doodles and the components exactly and it didn’t do anything.
Then Wilson came up with this crazy idea. Have you met Wilson’s wife? His second one, Sherri, the one with the little tiny voice and the great big… anyway, she’s really into all this New Age crap.
So here we are sitting around, staring at that damn board and drinking our gourmet coffee. (Mine was Kenyan, the kind with the smoky taste that goes for $25 a pound when you can get it.) Then Wilson sets down his mug and squints sorta sideways at the board.
“You know,” he says slowly, “if I didn’t know better I’d swear some of that stuff looks like pictures in a book Sherri’s got, a grimoire.”
Well, what the hell? Anything’s worth a try. Besides, screwing with that damn coffee maker kept us sane while we wrestled with our real problem. The, ah, Mighty Fine Board—TMFB for short.
If the coffee was a sore point, TMFB was acute appendicitis, kidney stones, and third-degree hemorrhoids. Some bright, young, freshly minted engineer over in Circuit Design had figured out that you could save a bundle on parts and production costs if you minimized the number of passive components on this particular board. So he cranked up his shiny new software and turned out a design that did away with maybe a third of those resistors, capacitors and such. Of course management loved him for such a shining example of Effective Engineering through Cost Containment. (Supposedly pronounced “eekks.” In our shop it sounded more like a fart.)
Unfortunately the bright, young, etc. was so green he believed what the software told him. The result was that the circuit was manufacturable, but would only work right if the tolerances stacked just so. Which meant that a lot of the time it didn’t work at all, and the board shop caught the flak because our implementation was supposed to make up for the missing components.