Analysis and Solution of Glass Cracking of Low Frequency Connector in Multi-Chip Module

Abstract

Multi-chip modules contain a large number of bare chips, which are sensitive to moisture in the packaging atmosphere. In order to ensure the long-term reliability of this kind of modules, it is necessary to seal the module package. Low-frequency connector is an indispensable part of multi-chip module, which is used to transmit internal and external electrical signals of modules. During the screening test, the phenomenon of unqualified hermeticity of some sealed modules appeared. Modules exhibit a leak rate greater than 1.0×10-3 Pa•m3/s during the tracer gas helium (He) fine leak test. Further inspection of the low-frequency connector body reveals that there are slender cracks in the connector glass body. The analysis shows that the reason of glass cracking is the thermal stress level of the module during welding heating exceeds the tensile strength of the glass, which leads to failure. Temperature difference exists in different positions of the connector during laser welding of cover plate, and cannot be eliminated by welding process optimization. After eliminating the internal defects of the glass body, the problem of glass body cracking did not occur in the process of multi-round step-by-step screening test, and the sealing test of module products was qualified after each test.