Back-end Design Tools (Physical Design):Thermal Design Tools

Thermal Design Tools

Larry:

Not the wires, usually, but hot spots are a problem area, particularly for large chips and those used in portable products. Power is turned into heat when electrical current passes through a resistance. We can generate less power (and heat) by reducing the IC voltage and minimizing the current.

For many digital products, power usage occurs only when the transistors switch. (They use almost no power when not switching. See Appendix A.) The faster they switch, the more power they use, and the more heat they generate. High-speed chips generate a lot of heat, unevenly distributed across the chip. Transistor characteristics such as noise margin vary with temperature. Therefore, signals between different temperature logic blocks are more susceptible to noise.

Too much heat generated in a small area can cause a hot spot. Thermal analysis tools analyze the power and display a thermal chip map showing hot spots.

Extreme differences in temperatures on the chip may cause mechanical stress in the silicon. This may result in cracks and breaks in the metal wire interconnect.

Nora:

I didn't realize the ICs could get that hot.

Larry:

Yes, some microprocessor chips use 60 watts or more, and require fans to operate.

Nora:

Is there anything else done before the chip is ready for manufacture?

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