Novel Photo-definable Low Dk & Df Polyimide for Advanced Package of High Frequency Application

Advanced package requires photo imageable dielectric which possesses low Dk & Df properties for low transmission loss. This paper will introduce a new novel low temperature curable (200 °C), low Dk (2.8) & Df (0.006) and photodefinable polyimide designed with suitable polymer and cross-linking reagent. The novel polyimide shows good patternability with conventional photolithographic equipment. 10 $\mu \mathrm{m}$ line & space can be open at 10 $\mu \mathrm{m}$ thickness. Furthermore, glass transition temperature after cure is around 125°C degree, elongation is over 50 % and the stripper chemical resistance is also exceptional. We investigated insulation properties by bias-HAST (130°C degree & 85%, 5 $\mu \mathrm{m}\ \mathrm{L}/\mathrm{S}$ (copper), 5V, 96hr), yet no failure was observed. Microstrip lines were fabricated using the novel polyimide and conventional polyimide. New PI's insertion loss (S21 parameter) was lower than conventional one's. We fabricated RDL structure of antenna in package (AiP) using the novel polyimide and evaluated antenna property at 80GHz. These results indicate our novel polyimide can be applicable to RDL structure for high frequency application.