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To: Square_Dealings who wrote (236101)	4/16/2003 11:06:12 PM
From: benwood	Read Replies (2) \| Respond to of 436258

Silver has the lowest resistance in carrying current, but that's not the whole story. Copper is still the "best" conductor for electricity. A quick internet search turned up this useful data: You have asked about the use of copper for electrical interconnects on chips, and why not use gold or silver. Let us look at the electrical resistivity of the metals gold, silver, aluminum, and copper: Metal Resistivity (Micro-Ohm Centimeters)@300Deg K Gold:............2.271 Ref: Handbook of Physics and Silver...........1.629 Chemistry-CRC Publishing 1998 Aluminum.........2.733 Copper...........1.725 We want the smallest resistivity possible. Note that Copper is smaller than gold and aluminum; and is almost as small as silver. The difference between copper and silver is very small, but copper offers the advantage of being less expensive, easier to work with metallurgically, and so it is the natural selection which has been made. In addition silver suffers from serious electromigration-problems. This means that when a silver conductor is carrying large electrical currents the atoms tend to become mobile and the grains physically move causing mechanical problems with the metal connections. Copper suffers much less from this problem. Therefore copper has been selected as the best choice. [Reference: Handbook for Multilevel Metallization; Wilson, Tracy, and Freeman; Noyes Pubilication 1993].