Investigation of the Influence of Boron Nitride Filler Combinations on the Thermal Conductivity and Viscosity of Thermoset Compounds
Topic(s) : Special Sessions
Co-authors :
Benedikt NEITZEL (GERMANY), Florian PUCH (GERMANY), Robert KRÜMMER (GERMANY), Tobias REIMANNAbstract :
Dynamically operating power electronic systems are inevitably accompanied by energy losses that result in heating. Excessive temperature increases must be avoided in order to prevent the operating points from shifting to less efficient ranges. Intelligent thermal management must therefore be utilized to operate systems within predetermined temperature ranges.
The diversion of heat using thermally conductive thermosets is a tried and tested method of passively cooling components. Potting of electrical systems with resin-based compounds improves heat transfer and provides protection against mechanical loads and stresses.
Aim of the study was to use particle filled thermoset resin to infiltrate electronic circuit boards via resin transfer molding, to increase the thermal conductivity towards its casings. Seven different shapes and sizes of boron nitride particles, consisting of flakes, platelets and agglomerates of different grades were compounded with an epoxy resin matrix and tested regarding the effect on viscosity and thermal conductivity. Higher filler contents were generally accompanied with increased thermal conductivity and increased viscosity. While maximizing the thermal conductivity is desirable, there are limitations to the processability of high viscosity fluids in the resin transfer molding process. Viscosity measurements for a wide variety of born nitride compounds were performed by rotational rheometry. Thermal conductivity measurements of the compounds were conducted by light flash analysis. Filler contents above 30 %wt. have shown to cause incomplete potting in the resin transfer molding process at lab scale with a maximum of 4 bar injection pressure. The maximum resin viscosity for adequate potting of electric components was determined as 7.500 mPas.
By combining different particle geometries, the compound viscosity was significantly reduced to processible levels while minimizing losses of thermal conductivity. An optimized compound for the potting of power electronics by resin transfer molding was developed and tested. Conclusively a lossy electrical system was embedded in an aluminum casing with different potting compounds and the effects on the heat development during operation was investigated. The differences in the temperature progression shows the advantages of thermally conductive potting materials. The potting of power electronics with boron nitride compounds enables higher power densities, which is highly valuable for mobile and dynamic applications.
The diversion of heat using thermally conductive thermosets is a tried and tested method of passively cooling components. Potting of electrical systems with resin-based compounds improves heat transfer and provides protection against mechanical loads and stresses.
Aim of the study was to use particle filled thermoset resin to infiltrate electronic circuit boards via resin transfer molding, to increase the thermal conductivity towards its casings. Seven different shapes and sizes of boron nitride particles, consisting of flakes, platelets and agglomerates of different grades were compounded with an epoxy resin matrix and tested regarding the effect on viscosity and thermal conductivity. Higher filler contents were generally accompanied with increased thermal conductivity and increased viscosity. While maximizing the thermal conductivity is desirable, there are limitations to the processability of high viscosity fluids in the resin transfer molding process. Viscosity measurements for a wide variety of born nitride compounds were performed by rotational rheometry. Thermal conductivity measurements of the compounds were conducted by light flash analysis. Filler contents above 30 %wt. have shown to cause incomplete potting in the resin transfer molding process at lab scale with a maximum of 4 bar injection pressure. The maximum resin viscosity for adequate potting of electric components was determined as 7.500 mPas.
By combining different particle geometries, the compound viscosity was significantly reduced to processible levels while minimizing losses of thermal conductivity. An optimized compound for the potting of power electronics by resin transfer molding was developed and tested. Conclusively a lossy electrical system was embedded in an aluminum casing with different potting compounds and the effects on the heat development during operation was investigated. The differences in the temperature progression shows the advantages of thermally conductive potting materials. The potting of power electronics with boron nitride compounds enables higher power densities, which is highly valuable for mobile and dynamic applications.