Heat dissipation is one of the key challenges for high-power electronics due to high heat generation and elevated operational temperatures, on the order of 300oC. Direct bond copper (DBC) substrates, composed of aluminum nitride (AlN) or silicon nitride (SiN) ceramics with copper (Cu) directly bonded to one or both sides, are used to dissipate heat due to their high thermal conductivity (200 W/m*K and 50 W/m*K respectively), and consequently high heat dissipation ability. However, to firmly adhere copper to such ceramic surfaces requires a high-temperature process, as high as 1000oC.
The high thermal expansion mismatch (CTE) between Cu (17 ppm) and AlN (4.5 ppm) or SiN (3 ppm) leads to high mechanical stresses on cool-down that can cause cracking and failure after just a few cycles of heating and cooling. High-power devices commonly experience a large number of thermal cycles during their lifespan. Therefore, managing thermal mismatch is an area of extreme importance to ensure high reliability and long life in the field.
While SiN is strong enough to handle thousands of thermal shock cycles, its thermal conductivity is 5 times lower than AlN. However, AlN is weaker than SiN and tends to yield to mechanical stresses and breaks quickly, which has greatly limited its utility.
Kuprion’s ActiveCopperTM Materials Provide a Robust & Less Costly Solution.
Kuprion’s engineered ActiveCopperTM sintering materials exhibit extremely high conductivity, up to 393 W/m*K, and easily bond directly to AlN and other ceramics at temperatures below 250o C. Kuprion’s innovative ActiveCopperTM materials can be formulated with CTE values that closely match a variety of ceramics and wide-bandgap (WBG) substrates including silicon carbide (SiC) and gallium nitride (GaN). Recent test results show superior reliability and performance by surviving more than 4,000 thermal shock cycles in air (-55o C to +150o C) without delamination or voiding (CSAM), achieving a world record for DBC AlN.
Kuprion’s ActiveCopperTM formulations can be deposited in a wide range of thicknesses, from 100 to at least 600 microns, using standard stencil and screen-printing techniques. Once cured, Kuprion’s ActiveCopperTM materials convert to bulk copper that can be easily soldered or bonded to using standard industry solders and adhesives. It can even be electroplated and etched using standard chemistries.
Kuprion’s technology enables lower processing temperatures and significantly reduces DBC AlN fabrication costs, opening up a wide range of opportunities for new multi-chip power module designs and heterogeneous integration of new semiconductor packages with much improved operating characteristics.