Tag Archives: CTE mismatch

Highly Thermally Conductive Z-axis Adhesive Film

btechcorp uses millions of graphite fibers per square inch aligned through the thickness of a thermoplastic adhesive to produce a Thermal Interface Material with very low thermal resistance….HM-2.

We just completed the first phase of our program to further reduce the HM-2 resistance by 25% for the thicker bondlines needed for larger bond areas. The original HM-2 resistance of 0.07 C-cm2/W at 100 microns thick is now down to 0.05 C-cm2/W and this modified HM-2 is currently in production.

HM-2’s low modulus thermoplastic provides excellent stress absorption… ceramic/Al coupons (10 cm2) had no degradation after thousands of thermal cycles. Customer thermal cycling in the -40C to +150C range is now underway using 25 cm2 coupons for an automotive application.

The second phase of our resistance reduction effort is underway. It is focused on adding an interposer layer to the graphite fiber ends to reduce the phonon scattering at their interface with metallic substrates.

Other polymers can also be used with the graphite fibers to meet a variety of application requirements.

Microelectronics Reliability 52 (2012) 2443-2446, Yasushi Yamada

A power semiconductor module using a bonding film with anisotropic thermal conduction has been studied.
The bonding film consists of polyamide with a low Young’s modulus and Z-axis-oriented fine graphite
fibers. All the materials of this device, including the insulated substrate and base plate, have low
coefficients of thermal expansion. The bonding film is inserted between the baseplate and an aluminum
active heatsink. No significant changes in the thermal resistance or cross-sectional microscopy images
were found after thermal cycling tests.

HM-2 TIM thermal cycling