What is the difference between DBA ceramic substrate and DBC ceramic substrate
With the continuous development of power electronic devices, heat dissipation has become a very important problem to be solved. In power electronic packaging, the heat dissipation substrate not only plays the role of electrical connection and mechanical support, but also is an important channel for heat transmission.
With the continuous development of power electronic devices, heat dissipation has become a very important problem to be solved. In power electronic packaging, the heat dissipation substrate not only plays the role of electrical connection and mechanical support, but also is an important channel for heat transmission. At present, the heat dissipation substrates used more in power electronic devices are DBA ceramic substrates and DBC ceramic substrates. So what is the difference between DBA ceramic substrates and DBC ceramic substrates.
First, what is a DBA ceramic substrate? What are the advantages?
The on-board high-power aluminum-clad substrate is a key component of the power control and conversion system of hybrid power vehicles, and it uses a DBA ceramic substrate.
Figure DBA ceramic substrate, source: Mitsubishi Materials Corporation
Directly bonded aluminum (DBA) is a new type of metal-bonded ceramic substrate developed based on DBC process technology. It is a substrate formed by bonding aluminum and ceramic layers. Its structure is similar to DBC. Similarly, various graphics can be etched like PCB.
Figure DBC substrate structure, source: Mitsubishi Materials Corporation
1.DBA ceramic substrate bonding principle
The DBA ceramic substrate bonding process is achieved by using aluminum in liquid state to have good wetting properties on ceramics. After the liquid Al and ceramic are wetted at above 660°C, as the temperature decreases, Al directly provides crystal nuclei for crystal growth on the ceramic surface, and the two are combined by cooling to room temperature.
Figure Traditional aluminum ceramic base coating method: a) liquid phase coating method, b) metal transition method
The aluminum substrate technology includes liquid aluminum coating method and metal transition method. Metal aluminum is very easy to oxidize in the air, and a dense aluminum oxide film is formed on the surface of the aluminum liquid, which greatly reduces the wettability of the aluminum liquid and the ceramic, affecting the aluminum coating process and bonding strength of the ceramic substrate. Therefore, improving the wettability of aluminum and ceramic is a necessary condition for preparing DBA ceramic substrates. The problem of poor wettability of the aluminum-ceramic interface can be solved by removing the aluminum surface oxide layer, taking certain measures to isolate oxygen, or forming a metal transition layer on the ceramic surface, through the Al-metal eutectic liquid phase.
2. Development status of DBA ceramic substrates
Based on the high thermal shock resistance and low weight of DBA substrates, it has a wide range of application prospects and the value of further promotion and improvement. At present, a lot of research work has been done on DBA technology at home and abroad, but the research on the structural details of the aluminum/ceramic interface is not in-depth enough. Due to the strict restrictions on oxygen content, DBA has high requirements for equipment and process control, high substrate production costs, and the thickness of the surface bonded aluminum is generally above 100 μm, which is not suitable for the production of fine circuits, limiting its promotion and application.
II. Characteristics, applications and differences between DBA ceramic substrates and DBC ceramic substrates
1. Characteristics and applications of DBA ceramic substrates
The temperature of copper and alumina bonding is high (>1000℃), and the interface forms the intermediate phase CuAlO2/CuAl2O4, so the internal stress of the copper-bonded alumina substrate is large and the thermal shock resistance is relatively poor. When subjected to thermal cycling, cracks are easily generated at the interface, resulting in the overall failure of the DBC substrate; and the poor thermal conductivity of CuAlO2/CuAl2O4 affects the overall heat dissipation performance of the substrate.
The bonding of aluminum and alumina ceramic substrates is physical wetting, and there is no chemical reaction on the interface. The good plasticity of pure aluminum itself can relieve the thermal stress caused by the different thermal expansion coefficients of the interface, and the peeling strength is large, which improves the reliability.
Currently, DBA ceramic substrates have been actually used as insulating circuit substrates for inverters of hybrid vehicles and industrial machines. Its excellent performance makes it have great potential in devices with special requirements for high reliability, and it is very suitable for automotive electronics, aerospace and other fields.
2. The difference between DBA ceramic substrate and DBC ceramic substrate
Although the conductivity of aluminum is not as good as that of copper, aluminum is abundant and cheap. Compared with copper, aluminum has a lower melting point, relatively good wettability with ceramic substrates, and excellent plasticity. DBA has different performance characteristics from DBC:
1) Excellent thermal shock fatigue resistance. Metal aluminum has a lower yield strength than copper, and its plastic deformation rate is more gradual. When subjected to thermal cycles, it can effectively reduce the internal stress between aluminum and ceramics.
2) Good thermal stability;
3) Light weight, 44% lighter than DBC of the same structure;
4) Good aluminum wire bonding ability;
5) The thermal stress between aluminum and ceramics is relatively small.
DBA and DBC are similar in many aspects, but compared with DBC, DBA has significant thermal shock resistance and thermal stability, and is light in weight and has low thermal stress, which is very effective in improving the stability of devices working at extreme temperatures. Therefore, it is particularly suitable for power electronic circuits. Similarly, DBC ceramic substrates can carry larger currents, have better thermal conductivity, and are more widely used because they are covered with copper. For more heat dissipation ceramic substrates, please consult Jinruixin Special Circuits.