One of the major driving forces for the electronic industry is the consumer handheld units, where even more functions in a smaller volume and with longer battery time are requested. This leads to a higher energy‐ and interconnect‐density. Two challenges related to this request, that the industry is facing, are thermal management and reliability. This paper aim to discuss some aspects of using flip chip (FC) technology on low temperature cofired ceramics (LTCC) for this kind of products and to focus on the heat dissipation problem of an FC mounted die.
Test designs were developed and built to investigate SnAgCu bumps on LTCC, underfill and five different LTCC designs. The LTCC design parameters were thermal vias and heat spreaders. In the experimental part, the semiconductor junction temperature was measured over a diode in the semiconductor. Cross sections and infrared thermal imaging were used. The experiments were accompanied by FE‐modeling using ANSYS workbench.
The main reduction in temperature is related to the use of thermal vias and a via offset smaller than 60 μm. A 100 μm via diameter gives only a minor increase in the semiconductor junction temperature. Reducing the LTCC substrate thickness will decrease the junction temperature further.
This paper shows that FC on LTCC is a promising key technology for power amplifier modules.
