Thermally conductive, electrically insulating adhesive for power chips
DELO in Germany has developed a new electronic adhesive that is both thermally conductive and electrically insulating and shows good strength even after standardized humidity tests with subsequent reflow cycles.
The DELO MONOPOX TC2270 ensures fast heat transfer and long-term reliable operation of semiconductors in power electronics.
A common reason for the failure of power semiconductors is the heat development in the often very small components, as there is usually no efficient heat dissipation. Adhesives not only ensure a permanent bond, but also dissipate heat and provide electrical insulation.
The adhesive is a one-component, heat-curing epoxy resin. Ceramic filler aluminum nitride in the resin provides very high thermal conductivity of 1.7 W/(m∙K), measured by the criteria of ASTM D5470. This is comparable with silver-filled isotropic conductive adhesives (ICA), which have a thermal conductivity of ~1.5-2.0 W/(m∙K).
One advantage of the TC2270 adhesive over ICA is that it also provides electrical insulation. This ensures both reliable heat dissipation and electrical insulation of assemblies. Using the new electronic adhesive additionally allows proportionate component costs to be reduced.
In cured condition, the TC2270 adhesive has a compression shear strength of 34 MPa on the FR4 composite material and of 11 MPa on high-performance LCP plastics. When bonding microchips, the electronic adhesive reaches values of 60 N in the die shear test (1×1 mm² silicon dies on gold surface). Even after standardized humidity tests, TC2270 shows suitable strength. To determine the moisture sensitivity level (MSL 1), silicon dies were bonded to different PCB materials, stored for one week at 85 °C and 85 % air humidity, and then subjected to three consecutive reflow cycles. Even with these loads, the adhesive retained its high strength level.
To enable the bonding of temperature-sensitive assemblies and prevent them from damage caused by excessive curing temperatures, the adhesive has been designed with a chemical system, ensuring that final strength is reached after 90 minutes at a curing temperature of 60 °C. With a temperature of 80 °C, the curing process can be reduced to 15 minutes. In this way, production processes can be individually adapted to the component types and quantities to be manufactured. The temperature range is between -40 and +150 °C.
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