Thick Film Technology For Today's Hearing Products

There has been continuous worldwide effort to increase the volumetric efficiency of electronic packaging. Much of this effort has been driven by the telecommunications industry that has succeeded in reducing cell phone size while simultaneously increasing functionality. The hearing aid business has always had the need to use extremely small electronic packaging because hearing aids pack electronics into the ear canal. The first commercial product using the transistor in 1952 was a hybrid vacuum tube-transistor hearing instrument. Today's hearing aids, such as Starkey's 3-Series product, have significant computing power and run complex hearing algorithms that have enormous impact on a patient's quality of life. The industry trend is to put more memory, more signal processing capability and more wireless capability into hearing aids to increase functionality and to improve performance. In order to achieve this increase in performance, the hearing business has had to develop and execute 3D packaging well ahead of other industries. This paper will examine the history of ceramic hybrid packaging at Starkey. The challenges and drivers for major technology steps will be addressed. The following technical advancements, transitions, considerations and limitations will be examined: changing ASIC technologies, impact of chip metallization, solder interconnect temperature hierarchy, impact of RoHS legislation, overcoming routing design limits, miniaturization realized by flip chip attach, impact of chip stacking on size, migration to stacked thick film ceramic interconnect layers using vertical interconnect channels, advances in thick film materials to support higher interconnect density, and incorporation of integrated passive devices.