3D integration technologies for ceramic substrates in a SHM application

Many applications restrict the lateral dimensions of a substrate. LTCC is one way to overcome this restriction by integrating passive components into the substrate. LTCC is used for building structural health monitoring (SHM) sensors in aerospace. One goal is to obtain compact and reliable sensors that are as intelligent as possible, resulting in a high number of passive and active components. This leads to a demand for more than one or two component layers, requiring substrates to be arranged 3-dimensionally. Research goals were to build a stack of sintered LTCC substrates, being reliable, high enough to give room for components and easy to manufacture. The paper analyzes several ways to build such a stack. The first part describes stacking technologies known from literature. In the second part, several technologies to build frames for stacking are analyzed. Technologies to connect the frame to ceramic substrates are also examined, including conductive paths through the frame. Finally, a SHM system built from a piezoelectric sensor (LTCC substrate one) and its signal preamplifiers (LTCC substrate two) is shown.