Thermo-mechanical Analysis of Thermal Compression Bonding Chip-Join Process

Abstract

Heterogeneous Integration (HI) Packaging has enabled high-bandwidth, low-latency communication between package components such as CPUs, GPUs and memory units for AI workloads. Examples of enabling HI packaging technologies include Si interposers, high-density laminates with thin films, silicon bridges and stacked chips.Thermo-compression bonding (TCB) chip-join process is achieved by the application of pressure and temperature to the mating surfaces which can be silicon-silicon or silicon-laminate substrate. A silicon-silicon structure has minimal thermal expansion mismatch while there is a large thermal expansion mismatch between silicon and laminate substrate. Also, the pressure and temperature capabilities of the TCB tools can be vastly different for different manufacturers. As a result, it is important to understand the effects of varying the TCB process parameters on the package components and interconnect quality.In this study, transient finite element models were created for the TCB process for a silicon-bridge structure with direct bonded heterogenous integration (DBHi) packaging. The package model consists of processor and bridge chips, interconnects between the chips, and underfill around the interconnects. In addition, our models also included TCB tool components in direct contact with the package, such as the ceramic heater, nozzle and heated pedestal. Appropriate thermal and mechanical boundary conditions were applied to the models based on the assembly process parameters for the different packages. The quality of the bonds was assessed from the resultant temperature profiles, stress distribution and warpage in the package components and interconnects. The effect of process parameters including bond temperature, bond force and temperature ramping rate was also studied to provide guidance toward improving the TCB bond profiles. Our work presents the first extensive modeling effort for thermal compression bonding of HI package structures to complement our prior thermo-mechanical analysis of the isolated package systems.