Polyimide Based Embedding Technology For RF Structures and Active Components

Abstract

Flexible materials are being used already today as base substrates for electronic assembly. A lot of mounted components, both active and passive components, could be integrated in flexible polyimide substrates. Very interesting advantages of integrating components into the flex are compactness and enhanced flexibility: not only the interconnection but also the components themselves can be mechanically flexible. Two polyimide based embedding technologies are described. First, a polyimide based 60 μm foldable chip package is presented: the ultra-thin chip package (UTCP). Chips thinned down to 20 μm are packaged in between two polyimide layers.Next, very thin, flexible RF structures are realized. Multilayers are built-up on temporary rigid carrier substrates by repetitive application of polyimide layers by a spin-on process and metal layers by sputtering. Sputtered NiCr is used as resistor material, a thin spincoated PI as capacitor dielectric. Inductors, capacitors and resistors are interconnected with microstrip transmission lines, realizing multilayer RF structures. Key words: chip package, RF structure, flexible, 3D.