Development of high-performance insulated circuit substrate “DBA substrate with Ag fired film” for next-generation power modules

Mitsubishi Materials Corporation (President: Hiroshi Yao, Capital: 119.4 billion yen) has developed a high-performance insulated circuit substrate for use in next-generation power modules “DBA (Direct Bonded Aluminum) substrate with Ag fired film” which directly formed a silver (Ag) fired film on the Aluminum (Al) circuit. The substrate is intended as an insulated circuit substrate for installation in high-temperature semiconductor devices which are expected to see increased future use in technology such as power control invertors for hybrid vehicles (HVs).

[Background/reasons for development]

In the field of high-output motor power control invertors for HVs, it is expected that there will be increased usage of SiC (silicon carbide), GaN (gallium nitride) and other high-temperature semiconductor elements which can operate in high-temperature environments of 200°C or more over, thus dramatically reducing power loss by responding to heat generated when converting to direct current or alternating current.
However, the conventional element bonding material of solder cannot be used in such high-temperature environments. Generally, Ag bonding material is used because of its outstanding heat resistance properties. Unfortunately, the use of Ag bonding material makes it necessary to perform complicated surface preparation such as adding a plate to the Al surface. The use of plating solution results in problems such as environmental load and increased manufacturing cost.
Our company has succeeded in forming an Ag fired film that possesses sufficient bonding strength on the Al circuit of our highly-reliable DBA substrate.
Plating surface preparation is not necessary for our substrate. By using Ag bonding material such as nano Ag, it is possible to directly bond elements to the Al surface. In the future, we expect increased usage in automobiles and railways as an insulated circuit substrate for SiC and other high-temperature semiconductor elements in power control invertors installed in HVs and other technology.


By optimizing glass components within the Ag paste, we form a fired film which is strongly bonded to Al after Ag firing (Figure 1).
A DBA substrate (Figure 2) with an Ag fired film is placed on top of the Al circuit for the DBA substrate which has a high thermal stress relaxation effect. Ceramic cracking was prevented even in extreme temperature cycle testing (-40°C to 200°C for 1,000 or more cycles).
By using nano Ag paste and oxidized Ag paste to bond high-temperature semiconductor elements to the substrate (Figure 3), it is possible to manufacture power modules capable of high-temperature operation.

In the future, our company will contribute to the growth of electric power equipment by using our unique technology to develop high-performance insulated circuit substrate products for power modules.

Cross-section of Al/Ag bond Figure 1: Cross-section of Al/Ag bond

Exterior of DBA substrate with Ag fired film Figure 2: Exterior of DBA substrate with Ag fired film

Example of element bonding composition Figure 3: Example of element bonding composition