Highly nanotextured nickel-electroplated bismuth vanadate micropillars for hotspot removal via air- and spray-cooling

Overheating and hotspots in high-power and high-density microelectronics can cause device malfunction and shortened device lifespans; however, cooling films with highly textured surfaces may alleviate these concerns by efficiently removing and dissipating heat. In this study, the electrospraying of bismuth vanadate (BiVO₄) facilitated the formation of micropillars via diffusion-limited aggregation, yielding a highly textured surface. This was subsequently metallized via Ni electroplating for use as an efficient heat-removing and -spreading film. Because of their large surface areas, the BiVO₄ micropillars acted not only as heat removers and spreaders, but also as an electrically insulating layer that could prevent unexpected electrical shocks to the device underneath the cooling film. The thermal resistance, electrical insulating properties, heat dissipating features, and convective heat transfer coefficient of the BiVO₄-Ni bilayer films were studied, and the films were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The obtained cooling films were very flexible and light and could be readily attached to portable electronics without adding much weight. Such films could become commercially viable solutions for the problem of overheating in portable electronics.