Key insulation materials of power supply module
In the development of power semiconductor modules, with the improvement of integration and the reduction of volume, the power consumption per unit heat dissipation area increases, and heat dissipation becomes the key problem in module manufacturing. However, the traditional module structure (welding and crimping) has been unable to successfully solve the heat dissipation problem. Therefore, new requirements are put forward for the heat-conducting and insulating materials between the heat-dissipating backplane and the chip. At present, this kind of material used in power electronics industry at home and abroad is generally ceramic-metal composite plate structure, referred to as DBC plate (Dircet Bonding Copper).
The so-called DBC technology refers to the technology of directly bonding copper to ceramic materials at high temperature. DBC board is mainly made of Al2O3, AIN, BeO and other thermal conductive and insulating ceramic substrates. BeO is rarely used in industry because of its toxicity. Although AIN has good thermal conductivity and thermal expansion coefficient similar to that of silicon, its price is too high. Therefore, at present, Al2O3 has been widely used as the insulation substrate of DBC board, and AIN is also developing.
At present, foreign DBC substrates have been put into industrial production, and are widely used in power semiconductor modules, microwave transmission, sealing and other fields. In the same power semiconductor, compared with the common welding module, the welding module of DBC board is not only small in size, light in weight and saves parts, but also has better thermal fatigue stability and higher integration. The research in this field in China has just started, and has not yet formed industrial production. The Institute of Electrical Insulation of Xi 'an Jiaotong University, combined with the "Eighth Five-Year Plan" task of GTR module packaging structure, developed Al2O3-Cu composite board by DBC Technology, and provided it to Xi 'an Institute of Power Electronics Technology, Beijing Power Electronics New Technology Research and Development Center and other units for trial use. At present, small batch production in laboratory has been formed. The market prospect is considerable. The roles of DBC board in the power module are as follows:
1) As the carrier of silicon wafers, there are no other materials or connecting lines between them. Substrate, wiring is similar to printed circuit board.
2) Good insulation performance, isolating the conductive part from the heat dissipation part.
3) The heat dissipation performance is good, and the heat generated by the silicon wafer is transferred to the heat dissipation device through the heat conduction engine oil.
Therefore, DBC substrate is a substrate with excellent thermal conductivity and insulation.Al2O3-Cu substrate has the following excellent characteristics:
1) Low thermal resistance, same thermal expansion coefficient as Al2O3, close to silicon (7.4 10-5k-1). When in use, the transition layer is not needed, and the silicon chip can be directly welded on the DBC substrate.
2) Good mechanical properties, adhesive force greater than 5,000 N/cm2 and peeling resistance greater than 90 N/cm;3) Corrosion resistance, no deformation, and can be used in the temperature range of -55 ~ 860;
4) Excellent electrical insulation, the withstand voltage of porcelain plate is more than 2.5KV.5) Good thermal conductivity with a thermal conductivity of 24 ~ 28w/mk；;6) Good weldability, over 95%. DBC board will be the basic material of electronic circuit structure and connection technology in the future. When the traditional organic copper clad laminate can't meet the thermal shock performance of components, DBC board will be used as the basic material of high-power electronic components. In use, because the thicker copper layer (0.3mm) can bear higher current load, under the same cross section, only 12% of the conductor width of the printed circuit board is needed. Good thermoelectric rate makes it possible to densely install power chips. It can transmit more power per unit volume, and improve the reliability of the system and equipment. It can be widely used in the following related fields of power electronics:
(1) Power semiconductor devices such as IGBT, GTR, SIT, etc.
(2) Power control circuit;
(3) Hybrid power lines and new power structure units;
(4) Power supply of solid-state relay and high-frequency switch module;
(5) the temperature control unit of the electronic heating device;
(6) Inverter, motor speed regulation, AC contactless switch;
(7) Electronic ceramic devices. According to our research, the barium titanate copper-fired electrode made by DBC technology has lower contact resistance and superior performance compared with ordinary silver-fired electrode and copper-plated electrode.
(8) Structural units such as automotive electronics and aerospace military technology. DBC technology is the foundation of future "core board" technology and represents the development trend of future packaging technology. With the application of DBC board, it takes a step towards the future "core board" technology, and at the same time forms the foundation of creative product concept and highly integrated equipment design. At present, with the development of new devices such as GTR, IGBT and SIT, DBC boards with better thermal conductivity are needed. AIN copper clad laminate was developed in Japan for IGBT packaging.
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