To meet this demand, device manufacturers are using pressure-sensitive adhesives (PSAs) for interconnects, grounding, and shielding applications. For more information see the IDTechEx Research report Thermal Interface Materials 2016-2026.
PSAs were developed as a heat sink attachment method to eliminate the need for clamping. They feature an adhesive coated on to a continuous web of a substrate material such as polyimide film, fiberglass mat, or aluminium foil in either single-faced, double-faced, or transfer adhesive constructions, and wound into large rolls that are then converted to the exact specifications required for the end application. They have the capability to be precisely die cut into custom shapes and narrow widths for improving manufacturing efficiency with mess-free processing.
Tapes are clean, low waste, and easily processed. Larger bonding areas are problematic for pastes and liquids, as voids may result. Tapes deliver uniform, void-free bondlines of controlled thicknesses. However, PSAs have very limited compliance.
As device manufacturers face the pressures of faster prototyping, quick changeovers, and the increased use of automation, the advantages of PSAs over labor-intensive soldering operations are becoming more evident. Additional desirable functional capabilities, such as an electrically conductive or thermally conductive adhesive, makes simplification of electronic device design and manufacturing possible. For more information see the IDTechEx Research report Electrically Conductive Adhesives 2016-2026.
Implantable devices are also incorporating the latest technological advancements for sophisticated and targeted therapies ranging from drug delivery and pain management to the treatment of neurological disorders. Popular fitness, health and lifestyle wearables are capable of performing sophisticated data monitoring and processing, despite being no larger or more disruptive than the average bracelet or watch. For more information see the IDTechEx Research report Wearable Technology 2015-2025: Technologies, Markets, Forecasts.
Many devices of these devices may lack the necessary space for such traditional cooling systems and thermal interface materials. Thinner form factors also mean that skin temperature is a key concern. First degree burns occur at 43°C, but the user is uncomfortable far below that, as low as 38°C when it is touching their face.
Surface area to dissipate heat is also very small. In a watch, the stack sequence can be used to make sure the heat is dissipated on the world-facing side, not the hand-facing side. Components are spread out on single-sided boards. Manufacturers also need to emphasize flexible form factors. Highly conductive materials are typically not flexible, and desired shapes of wearables are complex.