2D Computational Fluid Dynamics Simulation Analysis of the Assembly of Low-Temperature Cofired Ceramics/Low-Temperature Cofired Ceramics and Si/Si Sandwiches by Reactive Bonding

Numerical computational fluid dynamics simulations have been performed on 2D sandwich models to compare the performance of low-temperature cofired ceramics (LTCC)/LTCC and Si/Si sandwiches used in reactive bonding. In the sandwich model layers of solder, silver and a reactive multilayer used to bond the substrates are modeled. Additional to this, the surrounding air environment is also modeled. For simulating the heat released by the multilayer system, a user-defined function in the form of a square wave is written for the heat source with a defined width, corresponding to the reaction width, and this propagates at a fixed speed. Two sandwiches, one with LTCC/LTCC, and the other with Si/Si, are simulated and their response analyzed in terms of the solidification/melting of the solder and their respective time-temperature histories. In this article, it is shown that numerical computational fluid dynamics simulations reveal that low-temperature cofired ceramics (LTCC)/LTCC assemblies experience significantly higher temperatures than Si/Si during reactive bonding, due to LTCC's lower thermal conductivity. This leads to prolonged solder melting, increased stresses, and potential bonding issues. In these findings, it is suggested that optimizing solder thickness and reactive multilayer system deposition could address these thermal challenges, which are difficult to measure experimentally.image (c) 2024 WILEY-VCH GmbH