The circuit board is dead.

At least that's what the The New York Times proclaimed. In a Sept. 22 article, "New Sun Microsystems Chip May Unseat the Circuit Board," the paper described Sun research that would permit bare die to be placed edge-to-edge without the need for traditional PCB or package interconnect. "It could represent the end of the printed circuit board," said Jim Mitchell, director of Sun Laboratories. Maybe not. For starters, chips don't float in the air; they must be attached to something. Second, power is delivered to the chips somehow. Finally, the signals are going off substrate to talk with those pesky peripherals. Hmmm, as I see it, PCBs are pretty good at doing these functions already. To paraphrase Dr. "Bones" McCoy, "It's a PCB, Jim," but not as we know it. If you've read this far, I'm really just having a bit of fun with the spin. Actually, it's great to see Sun innovating and the technology looks interesting, but it clearly has a long way to go before it would be considered commercial. Today's supercomputers are implemented with multiple bare dice on a substrate--commonly known as multichip modules or system-in-package (SiP). A key reason for implementing MCM or SiP is to improve system performance because these methodologies permit the intervening package around the die to be removed.

Sun is presenting a concept that takes that idea a step further and removes the intervening interconnect of the package and module. I can see a few challenges to applying this Sun technology. The designer would have to architect the system so that all of the die I/O line up to form a complete system--kind of like a Rubik's Cube but in two dimensions! Of course, that implies the I/Os of the chips would have to be arranged "just so" and even then, it might not be physically possible. Another big issue: ICs come from different vendors for use in many different applications and they need to plug and play with each other. So the statement, "obsolete the traditional circuit board," may have been better said as "obsolete some of the interconnects between some of the ICs on a circuit board," but somehow that just doesn't catch the eye.

Why do folks keep trying to kill off the poor old PCB? In my view, the PCB is truly a remarkable invention. It permits those amazing ICs to actually do something useful. The PCB permits companies large and small to bring IP together from many sources in a highly cost-effective way with very low risk. Long live the PCB! Jamie Metcalfe is vice-president of strategic marketing, Silicon-Package-Board Business Unit, Cadence Design Systems and a member of PCD&M's editorial review board.