A consortium of seven partners from industry and research has developed and characterized a reliable interposer technology as a system-in-package (SiP) based on glass for broadband millimeter wave modules that can be used in sensors and communication at frequencies above 100 GHz. The SiP technology platform constitutes a sensor packaging revolution. Compared to the state of the art, it uses various waveguide concepts, high-density micro wiring, and hermetic encapsulation to increase functions able to be integrated. In addition, it makes applications up to 300 GHz possible thanks to high precision and material qualities. This is implemented within a single material system (glass) with excellent waveguide properties and high-precision micromachining, among others.
A good example for this technology is in radar sensors for industrial and process metrology. Standard packages do not work as the frequencies exceed 100 GHz – higher than those of mobile communications technology – and the need for stricter environmental requirements. Such radar sensors need to cater for specialized sensor ASICs and permit manufacturing in medium-sized quantities at competitive prices.
The use of glass interposers with electric feedthroughs (vias) provides hermetic packaging able to enclose the components between two glass interposers. The SiP packages are manufactured at wafer level with a diameter of up to 300 mm. This allows for moderate costs thanks to the simultaneous processing of many components and alignment accuracy within the narrow tolerances of RF technology. Adapted standard systems originally used for machining silicon wafers are employed for this, accelerating commercial implementation. Glass is also available in large panels, simplifying scaling to large quantities.
The R&D project responsible for this work “Glass Interposer Technology for Implementing Highly Compact Electronic Systems for High-frequency Applications” (GlaRA) is sponsored by the BMBF (Bundesministerium für Bildung und Forschung, German Federal Ministry of Education and Research).