Die shear analyze of electrically conductive adhesives in GaN wafer application

Because of the demand for high-speed and broadband networks, 5G technology has paid much attention. On the one hand, due to the transit frequency of 5G, which is 450 MHz - 6GHz and 24 GHz - 52 GHz, the RF component has to deal with a higher frequency than previous communication. On the other hand, a massive high-power channel is required for some applications, like wireless communication base stations, military applications, satellite communication, and TV broadcasting. Therefore, GaN has become a good choice for highpower and high-frequency RF applications. In GaN RF chips, electrically conductive adhesive (ECA) is a key component that restricts heat, electrical conductivity, and reliability. This research studied two ECAs in the die attach process of a 5G base station RF amplifier chip, ABP 8068TA from LOCTITE Corporation and ASP 295-09P9 from Heraeus Group. During the research, ASP 295-09P9 has different die shear performance for GaN and GaAs die. After troubleshooting, operation error, such as the uneven spread of ECA and height of ECA, is excluded. By testing the wafer back surface, it is found that both GaN die and GaAs die back are pure Au, but GaAs die back's roughness is 0.049um, which is rougher than GaN's (0.032um). It is reasonable to assume that a smoother surface is a disadvantage for the necking mechanism.