3D packaging for an implantable hemodynamic control system

In this presentation, the 3D packaging for an implantable hemodynamic control system is proposed. The system consists of a pressure sensor, an ASIC for data and energy management, an accelerometer for measuring the position of the patient and an interposer as a base. The interconnects of a MEMS accelerometer, the integration of all components on the interposer and the encapsulation were elaborated within the Fraunhofer Lighthouse Project ""Theranostic Implants"" by Fraunhofer ENAS. The ASIC and the pressure sensor were developed by Fraunhofer IMS. The base of the system, the interposer, features an LTCC technology with 75 mm line/space and 13 layers. It also contains a coil for inductive energy supply and data transmission. The ASIC and the MEMS accelerometer are mounted on the interposer either by flip-chip bonding with gold studbumps or by glueing and wire bonding. The bonds are stabilized with an underfiller and the wire bonds are protected by a glob top with a high thixotropy. The MEMS accelerometer is fabricated using deep reactive ion etching. After fabricating the MEMS core, it is wafer-level packaged with through-silicon vias. These through-silicon-vias are produced by etching square shaped holes in the silicon cap wafer. The buildup is investigated regarding bond quality and voids with micro computer tomography (Micro-CT) equipment and scanning acoustic microscopy (SAM). An Al2O3/Parylene system is used as a biocompatible and hermetic encapsulation. The system is highly miniaturized (length: 15 mm, diamter: 3 mm) due to the packaging technologies used and proved to be functional in first tests at Fraunhofer IMS.