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There are many types of ceramic chips, most famous is older CPU:s with gold plated lids. Thanks to it's construction there are a lot of different places where precious metals were used.
- Bond wire for connecting the die to the internal wiring.
- Gold silicon braze to braze the die to the ceramic body.
- Palladium silver braze, an alternative to the gold silicon braze.
- Gold plated legs, to minimize the risk of a bad connection.
- Gold plated landing pads for the bond wires to connect to. The base metal is often a molybdenum manganese alloy.
- Gold plated lids and heat spreaders. Plated to minimize oxidation during heat treatment of the CPU.
There are a whole lot of different ceramic CPU:s. The one thing they have in common is that the ceramics doesn't dissolve in normal circumstances. For refiners of electronic scrap the following groups are most common.
- CPU with gold plated heat spreader - Most famous is the Pentium Pro but many other CPU:s have been made with the same technology. The main detail that separates it from other CPU:s are the copper tungsten sintered alloy heat spreader. That alloy have the same thermal expansion as the ceramics while still conducting heat quite well.
- Gold Capped CPU - Example of this is 486, 386 and many motorola CPU:s. The cap is often made of kovar
- Ceramic capped CPU - Most common among pentium chips without integrated heat spreader. The lid that covers the die is made of ceramics and soldered to the body. More or less processed as the Gold capped CPU:s except there is no gold on the lid.
- AMD K6 - This one makes up it's own class. The top of the CPU is covered with an aluminum heat spreader.
Another way to "refine" CPU:s is to examine if it is a rare model. There are people collecting CPU:s and can pay a lot more than the gold content for rare ones. A good place to search for information is the CPU World site where there are a lot of data about CPU:s and a vibrant forum where CPU:s are traded and discussed.
Ceramic DIL chips are made up of two halves with a lead frame in the middle and mounted with a glass frit holding the pins and the pieces together. In a cavity in the center a die is brazed to the ceramic body and the connection to the pins is made with bond wires.