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86 SMT007 MAGAZINE I MAY 2021 conductivity and dielectric strength of the cooling system. In addition, there are now different prepreg dielectrics available that meet and exceed, the high requirements for thermal conductiv- ity and especially for high dielectric strength. Optimizing the processability of manufactur- ing thermal PCBs is a key development target, especially for high-volume, serial productions such as the automotive sector. One example is a dual thermal coating (DTC) process by which two glassless dielectric layers are applied directly to a metal carrier (copper or aluminum). With this new type of dielec- tric thermal technology, the heat-conducting/ insulation dielectric layer is a direct part of a metal carrier utilizing very thin layers, decreas- ing thermal resistance. e lower layer of the dielectric which is in direct contact with the metal base mate- rial is cured to a C-stage during the manufac- turing process to obtain the desired electrical and thermal properties as specified in the data- sheet. An additional layer of B-stage material is applied to the cured dielectric layer, which allows for further lamination processing by the user. is structure (metal carrier plus two- layer dielectric) is laminated under pressure and heat to form a homogeneous overall PCB. e result is a highly compact power module with optimized electrical and thermal prop- erties, which does not require any mechani- cal components for pressing the different lay- ers of the cooling system together. DTC offers an extended application lifetime throughout rough operational conditions, plus excellent longevity—meeting the strict requirements of the electronics industry. Conclusion e new thermal thin film B- and C-stage dielectric systems allow multilayer PCB designers to increase thermal conductance while providing higher voltage solutions with direct lamination to heat sinks or to a thermal metal base material. SMT007 Jeff Brandman is president of Aismalibar North America. Figure 6: Copper substrate coated with two thermally conductive polymer resins, supplied as a B-stage over a polymerized C-stage layer. (Source: Aismalibar)