Figure 3 shows the relationship of these three parameters with respect to acceptable bond adhesion. Temperature is the variable that produces the most effects on the bonding process. The uniformity of the pressure application is also a critical parameter, especially for large dice. Without uniform pressure, a void-free bond cannot be produced. To get this uniform pressure, a pickup tool that provides full face contact is required.
Acceptable adhesion requires a suitable combination of time, temperature and pressure.
Once the thermoplastic and the two surfaces to be joined reach a minimum temperature permitting the flow of the material, pressure becomes the dominant factor. The pressure forces the softened adhesive into the microstructure of the two surfaces. Obviously, when the adhesive flows more freely, less force is required. Time is required to allow the joint to reach the needed temperature and let the adhesive penetrate the microstructure. When the pressure and temperature are removed, the adhesives freezes back into its glassy state.