What is electronic grade silicon?

A1. Electronic grade silicone is a one-part, moisture- curing RTV (room temperature vulcanizing) silicone sealant/adhesive that is non-slump and cures to form a tough, permanently flexible rubber. The non-corrosive curing system of electronic grade silicone makes it ideally suited for protecting, sealing and insulating corrosion-sensitive electronic and electrical materials such as copper, brass, silver, etc.

A2. In the event the questioner was asking about silicon, not silicone, continue.

For the manufacture of electronic components, such as silicon-based semiconductor chips, a very high degree of purity is needed. Impurities must be below 1 part per billion. Sometimes called '9 nines purity', which is 99.9999999%.

There are a couple of methods for manufacturing to this purity, of which 'zone refining' is the more common.

Briefly, in this method, a cylinder of silicon is passed through an induction furnace, such that as the silicon rod is pulled through, only a small length of the rod is melted at any one time, and such is the propensity of silicon to crystallize, that any impurities are swept along the rod, to accumulate at one end. Repeated passages of the rod trough this induction furnace will move all the impurities. The part of the rod at the end, carrying the impurities is discarded.