A study of microwave curing process for underfill used in flip chip packaging. Part 2: 3D FEM simulation of microwave power distribution inside variable frequency microwave oven

A three dimensional finite element method was used to simulate the microwave field distribution inside a variable frequency microwave (VFM) oven containing a microwave reflective substrate board. The method was verified first by analyzing two simple cases which have analytical solutions. It was found that the positions of the substrate of flip chip can affect the harmonic frequencies. The power density can be very different at various natural frequencies. It was also found that VFM oven achieve better power distribution. This may be the first instance to simulate the microwave power distribution for VFM oven