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MAY 2021 I SMT007 MAGAZINE 85 cular application, the heat-conducting dielec- tric film achieves the best technical/com- mercial combination of heat dissipation and dielectric strength compared to alternative TIM techniques. Dielectric Manufacturing/Contouring e dielectric prepreg is manufactured as a glass fiber cloth, type 106 and 1078/1080, which is then enriched with mineral fillers in a proprietary process to achieve high thermal conductivity of the dielectric film. Apart from the pure filler material properties, particle size and distribution throughout the dielectric material are key factors in achieving a homo- geneous thermal conductivity of the TIM film. e revolutionary prepreg film in B-stage is used by PCB shops worldwide for pressing thermally conductive multilayers in their PCB production. In following the process steps, the B-stage prepreg is cured, where it achieves its specified high Tg values and thus obtaining maximum thermal conductivity and dielectric strength. e bonding prepreg sheet in cured form is manufactured in sheets as large as 1245 mm x 945 mm, for use directly by custom- ers who can machine the insulative thermal sheets to fit into their power module assem- bly. Customers can also purchase common PCB panel formats, such as 18x24 inches (460x610 mm). PCB manufacturers can request that the bonding prepreg cured film be supplied pre- machined to any rectangular or square for- mat to be delivered in stacks of several hun- dred individual films for further manual or automated processing. For pre-production test samples, prototypes, and small quantity pre- run tests, the bonding prepreg is offered pre- machined and specifically contoured, accord- ing to the customer's specification. is allows for a direct dielectric placement between the PCB and the heat sink in the customer's power module assembly. e usage of the bond film dielectric will achieve high thermal conduc- tivity without requiring any oil, grease, paste, or silicone thermal material. is provides for easy mounting, as well as ease of disassembly. For high-volume serial production, punch- ing the bonding dielectric with a customized punching tool has proved to be the most cost- effective solution. Future Outlook for TIM/Cooling— Concept Developments Future research of the TIM dielectric tech- nologies, where a combination of a cured ther- mal conductive dielectric layer, plus a PCB core, plus B-stage glue to a heat sink will allow the lamination of high count, multiple dielec- tric layer solutions for the customer's power module manufacturing, optimizing thermal Figure 4: Bonding prepreg pre-cured, manufactured in formats: 1245x945 mm and 1245x1040 mm. (Source: https://www.aismalibar. com/de/product_group/bond-sheet-cured-de) Figure 5: Example of bonding prepreg pre-cured and contoured. (Source: Aismalibar)