| Advanced Ceramic Heaters Improve IC Packaging and System Performance |
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| Jan 01 2007 | |
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Critical CoolingOne challenging aspect of designing the die bonder heater lies in the fast cooling. Even if the heater has high thermal conductivity, its cooling rate is too long when only natural convection is involved. It is not surprising that a heater could take more than 250 seconds to cool from 400ºC to 50ºC, as shown in Figure 1. The cooling time is significantly reduced (~55 s) when forced air (20 m/s) is applied onto both heater surfaces for cooling purposes. The time can be further reduced to 8.7 s when assisted with water flow through the channel inside the steel block attached to the heater bottom, as shown in Figure 2. As predicted by the cooling model, a heater assembly design for achieving 10- to 15-s cycle time is quite feasible when water cooling can be designed into the system. Because of the unique combination of material properties such as large thermal conductivity >140 W/Km, small coefficient of thermal expansion of 4.5×10-6/ºC, high dielectric strength of 15KV/mm, high electric resistivity of 10×1014 ohm-cm, and large elastic modulus of 330 GPa, AlN ceramic is an ideal candidate for a heater matrix among the high-performance ceramic materials. |
