1958 · Silicon Mesa Transistor · Work 832 of 1,871
A production room in a low industrial building in California, on a black table top under a magnifier lamp a hand in a white cotton glove holding with tweezers a plain smooth unmarked matt black metal can six millimetres across with a flat lid and three thin gold wires, beside it a flat aluminium tray with rows of identical black cans standing in perforated strips, a stereo microscope on a grey stand, a small rubber-bulb suction pick-up, a closed wooden box, through the window dry brown hills in afternoon light.
What it was used for
Fairchild Semiconductor built the silicon transistor for an order no established manufacturer could meet: drivers for the magnetic core memory of the B-70 bomber's on-board computer, ordered by IBM's Federal Systems Division at $150 apiece. The device was designed, per the Computer History Museum, within 5 months, together with crystal growing, photolithographic masks, aluminium contacts and the firm's own production and test equipment. It was introduced as type 2N697 at the Wescon trade show in August 1958; radiomuseum.org dates the earliest manufacturer's literature on the 2N697 to the same month. The Computer History Museum reports that the Autonetics Division of North American Aviation selected the 2N697 for the Minuteman I guidance computer, a 24-bit serial machine.
What was new
"Mesa" denotes the shape: the Computer History Museum says the type was so named for its raised plateau-like structure. The same source calls it the first commercial double-diffused (emitter and base) silicon mesa transistor. The shape itself was the weak point: late in 1958 the firm faced a reliability problem, in the museum's account, because tiny particles flaking off the inside of the metal package threatened to short across the exposed junctions on the mesa structure. Autonetics reported it; Fairchild then applied a pencil tap test to every device to detect errant metal flakes before shipment. Hoerni's answer, covering the junction with silicon dioxide, became the planar process.
What the sources leave open: On the size of the first order, two pages of the same museum give different figures: the Silicon Engine page 100 transistors, the compilation The Legacy of Fairchild 500 core-memory drivers, both at $150 each and both from the Federal Systems Division. No source opened gives electrical data for the 2N696 and 2N697; production and sales figures are missing. The planar patent US 3,025,589 was unreachable.