Inductive Heating Based on VHF-ISM Radio Band Frequencies as Technology Platform for Efficient Heating of Metallic Micro-Scaled Bonding Layers in MEMS Packaging

This article presents a technique for selective and energy-efficient induction heating of aluminum (Al) frames to support and enhance the thermocompression bonding (TCB) for electronics packaging in the field of heterogeneous integration. The technological challenges include the use of an adapted induction coil for homogeneous heat distribution, the implementation of industrial, scientific, and medical (ISM) radio band frequencies in the high frequency (HF) and very high frequency (VHF) range up to
$f_{0}$
= 40.68 MHz, and the assembly of a heating system based on an RF generator and automatic matching unit for impedance modulation. Finite element analysis (FEA) was used to calculate the electromagnetic (EM) fields based on the coil design used. The inductive heating was successfully carried out using a generator power of
$P$
= 100 W with coil currents in the range of
$I_{0}$
= 10.1–11.3 A (amplitudes). With this setup, a peak temperature of
$T_{f\_{}{\text {max}}}$
= 633 °C in the Al frames could be achieved after
$t_{h}$
= 10 s. This corresponds to an average heating rate of dT / dt = 63.3 K/s.