Research on design and processing technology of 0.4mm pitch CQFN package

Based on the high-density multi-layer co fired ceramic technology system, a 0.4mm pitch ceramic quad flat nonleaded package is successfully developed for the first time in China. The pin pitch of this kind of package is reduced from the traditional 0.5mm to 0.4mm. Through the research of key technologies such as small-size hollow hole processing and ultra-narrow center distance hollow center metallization, the processing of 0.4mm pitch hollow hole is mastered. In this paper, the structural reliability of 0.4mm pitch CQFN package is simulated and optimized by using the finite element analysis software ANSYS, and the high-frequency transmission performance of the package is simulated by using the electromagnetic simulation software HFSS. In the design of microwave transmission path, this kind of package adopts the three-dimensional RF transmission structure of grounded coplanar waveguide line-hollow via-grounded coplanar waveguide line. Through the side hollow metallized via structure, the transmission of microwave signal from the pad at the bottom of the package to the internal strip line and bonding area micro strip line is realized. A transition structure is added between the transmissions lines with different forms of side hollow holes and strip lines, so that each RF port can achieve a 50 Ω matching. The bottom of the package eliminates the cavity resonance effect by adding a dense array grounding via structure. The microwave performance of the package was tested by vector network analyzer and microwave probe platform. In the DC ~ 26GHz band, the return loss of the RF pin of the package is less than 15dB and the insertion loss is less than 0.50dB. The test results are in good agreement with the simulation results. The package structure and RF pin three-dimensional transmission model designed in this paper can be effectively applied to the design of other RF surface mount ceramic high-density packaging packages.