USB memory sticks are a dime a dozen. Thanks to the ubiquity of flash memory, USB sticks are handed out like candy at shows like CES and sold online for less than a buck a gigabyte. We use them all the time, but do we ever wonder about how they're made? No need to, now; Bunnie Huang posted a blog on Tuesday about about visiting a USB memory factory, and he's posted some cool photos of the production process and explained how the whole thing works.
The whole production is carried out with an amusing mixture of low and high technology. Before the flash memory chips are mounted onto a printed circuit board, they're screened for quality and storage volume. The chips are mounted under a probe card, which connects to a tiny strip on the edge of each flash chip using metal needles for contact. Huang points out that the probe card is held together with rubber bands.
Then the most interesting stage of production: flash chips that pass muster are mounted onto printed circuit boards by hand. This is no austere automated factory, but a place where humans and machines each take part in the production process.
Workers use a long, thin tool that looks like a spudger or a bamboo chopstick. Once the chips have been placed, a machine wirebonds them to the circuit board. And if the wiring goes wrong, someone has to pull the microscopic wiring out of the board and re-feed it into the machine by hand. No easy task.
One last tidbit: Huang found out that the flash memory chips are flexible, even when mounted on printed circuit board. They only lose their flexibility when they're layered with epoxy and then cut into individual pieces. Because the silicon on the backs of the chips has been ground away for thickness, the entire circuit board can flex quite a bit.