materials | Thermally conductive
Expansion can be adjusted to the same level of copper used in printed circuit boards, for example. 3M Boron Nitride Cooling Filler Platelets are suitable
Figure 1: In plane and through plane thermal conductivity data of different 3M boron nitride additives in PA6 moulded plates
Fillers, which the company describes as a “game changer” for functional integration in advanced electronic constructions. “Not only the known excellent thermal conductivity but the balance of properties make it the preferred fi ller choice for functionally integrated designs as shown by the LED torch demonstrator,” says Armin Kayser, Manager for Product and Application Development in 3M’s Advanced Materials Division in Kempten, Germany.
Kayser points out that the thermal conductivity of
compounds can be adjusted between 1 and 15 W/mK with the addition of between 10 and 50% (by volume) of the same fi ller product. “This can be basis for a platform concept of compounds addressing the whole spectrum of application needs,” he says. For medium performance compounds (containing 20-30% of the BN additive for a conductivity of 3-5 W/mK), secondary additives such as glass fi bres, pigments and fl ame retardants can be added without compromising the processing characteristics of the compound. The good fl ow and moulding properties of BN-based
Right: 3M’s
Boron Nitride Cooling Filler
Flakes are said to offer
improved thermal
performance at thinner wall sections
compounds allow complex and thin-walled moulds to be fi lled, Kayser adds. Injection pressure is typically increased by less than 50% compared to unfi lled compounds. This is important for several reasons, not least of which is that low injection pressures are neces- sary for functional integration of printed circuit boards and other electronic components. Kayser further claims that thermally conductive compounds commonly result in high wear of steel moulds, “but this becomes a non-issue when using dry lubricating 3M BN Cooling Fillers.” The 3M fi llers show an optical refl ectivity of over 90% in all visible light bands. On this basis, compounds can be used for highest optical quality refl ectors. Meanwhile the platelet structure of these particular additives effectively reduces the thermal expansion of polymer compounds.
48 INJECTION WORLD | May 2016
for most thermoplastic compound applications requiring excellent heat dissipation properties, Kayser claims. However, for applications requiring high thermal transfer through thin electrical insulating walls 3M has developed a new generation of fi llers that achieves up to 4 W/mK in the through-plane direction at 50% loading by volume (Figure 1). “3M BN Cooling Filler Flakes offer a unique combination of high in-plane and through plane conductivity,” Kayser says. “At fi ller loadings of up to 50%, compounding normally becomes challenging with BN products, but not when using 3M BN Cooling Filler Flakes. Due to their larger size (200 microns) and high density, they can easily be com- pounded at even higher concentrations than 50%.” Saint Gobain also supplies BN additives. The
company’s Marketing Manager Neelam Kumar reports an increase in awareness in the market for the product in what he says are still niche applications for thermally conductive, electrically isolating (TC, EI) plastics. “As electronics are becoming smaller yet more powerful with every generation, the need for TC and EI plastics for casings, housings and enclosures of these devices is growing tremendously,” she says. The company’s CarboTherm PCTP30D grade is designed specifi cally for use in plastics and performs well in thermoplastic compounding applications, Kumar says. “It fl ows well in high-volume automated dispensing equipment, providing up to 25% increase in throughput, which has been a challenge for most BN fi llers,” she claims. “Because of its unique particle size distribution after dispersion in a twin screw compounder, it offers highly optimised thermal paths along the matrix, and therefore higher thermal conductivity along the z-plane.” Silatherm aluminosilicate mineral fi llers from HPF The Mineral Engineers, a division of the Quartzwerke Group, have been used in serial thermal management
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