New adhesive for power semiconductors from DELO

29th May 2020

Alex Lynn

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DELO has developed an adhesive for electronics that is both thermally conductive and electrically insulating. DELO MONOPOX TC2270 shows good strength, even after standardized humidity tests with subsequent reflow cycles are performed. This new adhesive ensures fast heat transfer and long-term reliable operation of semiconductors in power electronics.

A common reason that power semiconductors fail is because heat develops in their extremely small components with no place for it to dissipate. By using an adhesive like DELO MONOPOX TC2270, not only is a permanent bond and electrical insulation created, but heat is able to dissipate.

Due to its ceramic filler, aluminum nitride, DELO’s new one-component, heat-curing epoxy 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 main advantage to using DELO MONOPOX TC2270 over ICA is that it provides both heat dissipation and electrical insulation of assemblies. Using the new electronic adhesive additionally allows proportionate component costs to be reduced. After it has been cured, DELO MONOPOX TC2270 has a compression shear strength of 34 MPa on the FR4 composite material and 11 MPa on high-performance LCP plastics. When bonding microchips, the adhesive reaches values of 60 N in the die shear test (1x1mm² silicon dies on gold surface).

DELO MONOPOX TC2270 shows good strength after standardized humidity tests. 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. The adhesive retained its high strength level with these loads.

To enable the bonding of temperature-sensitive assemblies and prevent them from damage caused by excessive curing temperatures, the adhesive is 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 completed in 15 minutes. That way, production processes can be individually adapted to the component types and quantities to be manufactured. The adhesive's service temperature range is between -40 and +150°C.