CPU

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The CPU is the brain of the computer and contains the main calculating unit. This is usually a large chip with a lot of connections to the rest of the computer. Over the years the technology to build CPU:s have changed so there are a lot of different models of chips out there and consequently there are a lot of different processes to get the gold out of them.

Traditionally the CPU have been a good source of gold from all the bond wires, but recent developments of solder bumped flip chips have made it possible to build CPU:s with a minimum of precious metals.

Contents

Some common types of CPU:s

Ceramic CPU:s

This is the classical old style CPU with a ceramic body and often a gold plated lid.

Black fiber chips

This CPU is a bit special, it's the first generation where the chip is mounted on a fiber base, a small circuit board. The CPU is still connected with bond wires but it's been encased in a black resin and needs incineration to access the gold.

Green fiber, no metal

In this generation of CPU:s the chip is no longer connected with bond wires, it is mounted upside down on the fiber base via microscopic solder bumps. The only viable source of gold for the home refiner is in the plating of the pins.

Green fiber with heatspreader

This CPU contains an integrated heat spreader. Commonly soldered on top of the CPU with an indium solder and the heat spreader have a gold plated area where it is soldered. Otherwise it is basically the same as the green fiber without metal above.

Pinless with heatspreader

Next step is elimination of the pins all together, the signals are connected via gold plated landing pads and the gold content is even lower than the previous generation.

Yields

  • Successful engineer : Gold from the bottom parts of pinless CPU:s Not counting the gold on the lid. The final yield was 1.63 mg gold per CPU.
  • Göran : 0.1 +/- 0.05g gold for 20 CPU:s including gold on the heat spreader.

Black surface mounted CPU

As there are too many other models and CPU:s out there we can't list them all, but a special mentioning of the surface mounted CPU:s is warranted. As more and more devices becomes computer controlled there are CPU:s hiding everywhere. It will not look like a classic CPU with a ceramic body and lots of gold, but the major part is inconspicuous looking black plastic chips , for example the 386 CPU in earlier computers but also many embedded CPU:s in modern devices. As the refining process isn't concerned with what a chip was used for but only how it was built it is refined via the same process as other black plastic chips.

References

  • [ GRF : ...]
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