Understanding heat transfer in the lead-on-chip die bonding process

Temperature is, besides pressure and bonding time, the key parameter controlling the lead-on-chip (LOC) die bonding process. It determines how fast the thermoplastic adhesive melts and thus how small the minimum lamination time can be. On the other hand, overheating the LOC tape may cause bubbles or decomposition of the polymers. Therefore, the absolute temperature of the LOC tape is an important issue. The paper describes the measurement of the evolution of temperature in the bonding process using a temperature sensor located between the die surface and the LOC tape. The experimental data is compared with numerical calculations. The paper concludes with analysis of how heat transfer is influenced by the thermal properties of the heated bonding tools and the thermal contact conductance between package and tools.