Influence of thermal contact resistance on thermal impedance of microelectronic structures

The thermal impedance Zth(jω) has been calculated numerically for a silicon chip glued on a ceramic substrate. The non perfect thermal contact is taken into account by modelling the chip-substrate interface as a thermal contact resistance rc. If Zth is represented as a Nyquist plot, mainly two circular arcs are observed. The high frequency arc is found to be almost independent from rc, whereas the low frequency part is largely influenced by rc. The thermal resistance Rth = Zth(jω = 0) increases linearly with rc, as known from the literature. Additionally, our simulations have shown that similar conclusions can be drawn for the real and imaginary part of Zth at a fixed frequency ω ≠ 0.