Understanding Smart Sensors - Nomads.usp

10Packaging, Testing, and ReliabilityImplications of Smarter SensorsI regret that there are no more worlds to conquer.—Alexander the Great10.1 IntroductionAll the advances and research that are occurring in micromachining would leadone to believe that breakthroughs in those areas will be sufficient to revolutionizesensing. Unfortunately, the problems associated with the basic sensor packagingare compounded when the sensor is combined with higher levels ofelectronics. These problems initiate at the lowest level of die and wire bondingand extend to encapsulation, sealing, and lead-forming issues. Fundamentalassembly differences frequently exist between sensor and microelectronics packagingand are among the problems that must be solved to achieve smarter sensors.These differences include die bonding for stress isolation instead of forheat dissipation and wire bonding procedures.Packaging is essential to establishing the reliability of the sensor. Thereforethe reliability requirements must be taken into account in the design of thepackage, especially for custom packages in specific applications. Testing of thesensor-circuitry combination also requires combining test capability from bothtechnologies. This chapter addresses sensor packaging technology, especiallynew technology from the semiconductor industry, that should be applied tosmart sensors, reliability, and testing concerns for smarter sensors.227