Modeling & Investigating Packaging Effects on Sensing Devices

Abstract

The continued drive for digitization is making our everyday experiences to be greatly interwoven with sensing devices. Sensors are nowadays embedded seamlessly in our various daily activities and interconnected together through a network. Different types of sensors are today well ingrained in our life, some sensing changes in environment such as temperature or pressure, some sensing dynamic movements such as acceleration others sensing physical quantities such as magnetic fields in piezoresistive sensors or light for proximity purpose. Various kinds of sensing technologies exist: Micro-electromechanical systems (MEMS) [1] sensors, Optical sensors, Hall sensors. When packaging these type of sensors, regardless of their different operating principles one common aspect converges for all of them: the package housing needs to be designed in such a way to reduce stress transmissions to their sensitive parts. Failure to do so will result in unwanted drifts influencing the sensor final output and hence its performance. When stress is high enough it will result in unwanted deformations leading to a shift. As thermomechanical modeling engineers, and in collaboration with package design, in our strive of Design for X (DFX), we must identify and propose packaging solutions that lead to thermomechanical stability in such a way that our final device is as flat as possible and/or the sensitive parts are well decoupled from the remainder of the plastic package such that thermomechanically induced stresses are eliminated or reduced to a minimum. In addition to this, the thermo-mechanical modeling engineer, needs to ensure that in the strive for DFX, all thermo-mechanical aspects and potential detractors are bottomed down including but not limited to Design for Reliability (DfR) and Design for Manufacturability (DfM) [2], [3]. While this paper will not go into specific details of the latter it is fundamental for the thermo-mechanical expert to ensure a holistic approach in the recommendations made. It is also understood that in a thermo-mechanically stable structure, a device is expected to benefit in various ways including in reliability, in its operational performance and during manufacturing.