Introduction to Direct Bonded Copper Ceramic Substrate (DBC).

DBC Ceramic Substrate process is to add oxygen elements between copper and ceramics, obtain Cu-O eutectic liquid at a temperature of 1065 ~ 1083 ° C, and then react to obtain an intermediate phase (CuAlO2 or CuAl2O4), so as to realize the combination of Cu plate and Ceramic Substrate chemical metallurgy, and finally through lithography technology to achieve pattern preparation, forming a circuit.

The Ceramic PCB Substrate is divided into 3 layers, and the insulating material in the middle is Al2O3 or AlN. The thermal conductivity of Al2O3 is typically 24 W/(m·K), and the thermal conductivity of AlN is 170 W/(m·K). The coefficient of thermal expansion of the DBC ceramic substrate is similar to that of Al2O3/AlN, which is very close to the coefficient of thermal expansion of the LED epitaxial material, which can significantly reduce the thermal stress generated between the chip and the Blank Ceramic Substrate.

Merit:

Because the copper foil has good electrical conductivity and thermal conductivity, and alumina can effectively control the expansion of cu-Al2O3-Cu complex, so that the DBC substrate has a coefficient of thermal expansion similar to that of alumina, DBC has the advantages of good thermal conductivity, strong insulation and high reliability, and has been widely used in IGBT, LD and CPV packaging. Especially due to the thick copper foil (100~600μm), it has obvious advantages in the field of IGBT and LD packaging.

Insufficient:

(1) The preparation process uses the eutectic reaction between Cu and Al2O3 at high temperature (1065 °C), which requires high equipment and process control, making the cost of the substrate high;

(2) Due to the easy generation of micropores between Al2O3 and Cu layers, the thermal shock resistance of the product is reduced, and these shortcomings have become the bottleneck of the promotion of DBC substrates.

In the preparation process of DBC substrate, the eutectic temperature and oxygen content need to be strictly controlled, and the oxidation time and oxidation temperature are the two most important parameters. After the copper foil is pre-oxidized, the bonding interface can form enough CuxOy phase to wet Al2O3 ceramic and copper foil, with high binding strength; If the copper foil is not pre-oxidized, CuxOy wettability is poor, and a large number of holes and defects will remain in the bonding interface, reducing the bonding strength and thermal conductivity. For the preparation of DBC substrates using AlN ceramics, it is also necessary to pre-oxidize the Ceramic Substrates, form Al2O3 films, and then react with copper foils for eutectic reaction.