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| Direct bonded copper (DBC) substrates are composed of a ceramic insulator, Al2O3 (aluminum oxide) or AlN (aluminum nitride) onto which pure copper metal is attached by a high temperature eutectic melting process and thus tightly and firmly joined to the ceramic. |
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The unique usefulness of DBC substrates in power electronics is owed especially to the high thermal conductivity of Al2O3 (24 W/mK) and AlN (130 to 180 W/mK), and the high thermal capacity and heat dissipation of the thick copper layer (200-600 µm).
Although silicon chips are, in general, attached bare (unpackaged), the mechanical stress load on them is small, since the coefficients of thermal expansion of aluminum oxide (7.1 ppm/K) and aluminum nitride (4.1 ppm/K) are closer to that of silicon (4 ppm/K) than is the case with substrates based on metal or polymers.
The use of high-purity copper enables current carrying capability superior to any achieved with alternative technologies. As with ceramic printed circuit boards, customer-specific layouts may be designed.
Surfaces may be plated with nickel or nickel/gold or covered with solder resist.
Multilayer DBC for hermetically sealed packages are assembled with interconnections and, due to their light weight and reliability, are increasingly being utilized in aerospace applications.
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| Advantages |
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High thermal conductivity and thermal stability |
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High insulating voltage |
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High heat dissipation |
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Similarity of expansion coefficients enables chip-on-board applications |
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