SIP with TSV for Class 1 Medical Devices

The demand for greater performance of hearing instruments in smaller form factors continues to drive the need for miniaturization of microelectronic packages. Reported here is how TSV technology was used to shrink the size of a conventional DSP-based system in package (SIP) used in the smallest In-The-Ear (ITE) hearing instruments. The conventional SIP is a heterogeneous multichip module containing a wire bonded EEPROM die mounted atop a DSP flip chip die along with 10 passive components built upon a high density alumina substrate. The wire bonds of the conventional SIP, along with the extra space they require, are eliminated and replaced by TSV structures fabricated in the DSP IC wafer using the via last method. A redistribution layer on the back side of the DSP IC enables direct attachment and electrical interconnection of the memory IC to the DSP IC. The result is a 23% smaller SIP with functionality demonstrated in hearing aid prototypes. This is believed to be the first demonstration of TSV in a heterogeneous hearing aid multichip module. This paper describes the design approach, materials, basic process steps, results, and challenges encountered in creating this novel TSV-SIP.