关键词: 低温共烧陶瓷, 方形扁平无引脚封装, 高速链路, 阻抗匹配

Abstract: Aiming at the problem that the packaging substrates with QFN（Quad Flat No-lead Package）packaging structure and cavity slots are difficult to test, this paper proposes a method to obtain the performance of LTCC（Low Temperature Co-fired Ceramic）packaging substrates by using auxiliary test board and de-embedding based on 2X Thru principle. An ideal impedance matching structure is obtained by simulating and optimizing the interconnection structure between QFN and test board. On this basis, the entire link including two test adapter boards, interconnection gold wire, vertical through-hole of LTCC substrate and output of QFN structure to transmit DC-40 GHz differential signal is simulated and analyzed jointly. Through physical test, the performance of the auxiliary test board after de-embedding is basically consistent with the simulation results, which shows that the method can solve the test problem of LTCC packaging substrate with this structure. At the same time, the signal transmission performance of entire link is obtained: insertion loss value is less than 2.7 dB, echo loss is less than –10 dB, which meets the requirements of our products for high-speed bandwidth.

Key words: LTCC, QFN, high speed link, impedance matching