A composite material can be defined as a material in which two or more different materials are bonded together. It is sensible to make a distinction between macrocomposites and microcomposites. The first group usually has a layered structure, and PCBs are the main application. The second group looks uniform to the naked eye; materials from this group are often used for packages … [Read more...]
The thermal conductivity of ceramics
Ceramics are increasingly used in packages and printed circuit boards, because they have a number of advantages over plastics: much higher thermal conductivity, possible match of the coefficient of thermal expansion, and hermetic sealing. Unfortunately, the cost of ceramics is still much higher than that of plastics, prohibiting their use in low-cost high-volume products. … [Read more...]
The thermal conductivity of aluminum oxide
Aluminum Oxide (Al2O3) is an important ceramic for the electronics industry. Besides its use as a passivation layer on Silicon, the ceramic is often used as a carrier for thick and thin film passive components and for other small printed circuit boards. A relatively low cost is combined with a relatively high thermal conductivity, especially when compared to FR4 board material. … [Read more...]
The thermal conductivity of pure metals
As discussed previously in this section, the measurement of the thermal conductivity is notoriously difficult. The consequence is that, while the measurement accuracy by individual researchers is claimed to be of the order of 2%, laboratories participating in round-robin tests produce results differing from each other by 15% or more [1]. Even the measurement of pure metals is … [Read more...]
The thermal conductivity of gases
The value of thermal conductivity for most gases and vapors range between 0.01 and 0.03 W/mK at room temperature. Notable exceptions are Helium (0.15) and Hydrogen (0.18). The most common theoretical explanation of heat conduction in gases is provided by the kinetic gas theory, which treats the collisions between the atoms or molecules as the prime mode of transfer of energy. … [Read more...]
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