Vijay Sarihan

Designing small footprint, low-cost, high-reliability packages for performance sensitive MEMS sensors

Packaging micro-electro-mechanical systems (MEMS) is still recognized as a show stopper for wider application and extensive commercialization. The challenge in MEMS package design is to deliver a robust, low cost, small footprint, high reliability package that helps to deliver flawless MEMS performance over the customer regime. These are ongoing MEMS packaging challenges. This paper outlines how freescale semiconductor has successfully met the packaging challenge for the MEMS acceleration sensor. A packaging strategy was chosen from low cost and small footprint considerations. However packaging stresses impact the performance of the transducer. Coupled packaging stress and MEMS transducer response simulation was done to identify the package related parameters that were impacting the MEMS performance. As is typically the case, the packaging fix to correct for the performance resulted in a reliability challenged package that did not meet the customer life cycle expectations. An advanced package design methodology was developed to couple simulations for package reliability prediction with package performance predictions to deliver a robust, low cost, small footprint, high reliability package that delivers flawless MEMS performance to satisfy an ever tightening customer requirement. The predictive design methodology was extensively validated with experimental results at every stage for reduced cycle time for new product introduction.

A multidisciplinary approach for effective packaging of MEMS accelerometer

Micro-electro-mechanical systems (MEMS) packaging is becoming increasingly critical and plays a major role in the successful commercialization of MEMS product. The packaging system should eable the MEMS perform the sensing function and at the same time protect it from the environmental disturbance, and help improve product quality to the sub-ppm level. One of our accelerometers in an SOIC package experienced a low ppm occurrence of device fracture. This MEMS package is unique in that the package has to maintain a certain resonance frequency to protect the transducer from sticking or clipping. At the same time, the package has to deliver a reliable and intact transducer with no cracking or output offset. A multidisciplinary approach inclusive of vibration analysis, electrical response determination, stress analysis, and fracture mechanics was used to determine the appropriate die attach material to completely resolve the device fracture issue.

Multidisciplinary Approach for Robust Package Design of MEMS Accelerometers

Micro-electro-mechanical systems (MEMS) packaging is becoming increasingly critical and plays a major role in the successful commercialization of MEMS products. The packaging system should enable the MEMS to perform the sensing function and at the same time protect it from environmental exposure. The design of the package should be robust enough to be able to withstand minor handling and manufacturing induced defects. Failures due to these defects are not unusual, one of our accelerometers in a small outline integrated circuit package has experienced a low ppm occurrence of device fracture. A multidisciplinary approach inclusive of vibration analysis, electrical response determination, stress analysis, and fracture mechanics are utilized to determine the appropriate package design. It is demonstrated here on a MEMS package for automotive airbag deployment. Along with the usual temperature exposure, this package also has to withstand a harsh vibration environment. The package is designed to avoid exciting MEMS resonance frequency to protect the transducer from sticking or clipping. At the same time, it delivers a reliable and intact transducer with no device fracture failures or output signal offset.

Engineering New Package Ideal Materials Using Polymer Resins and Nanoparticles

The trend in new electronic packages is to deliver smaller, thinner space-sensitive packages that meet or exceed customer package reliability expectations. This poses new material challenges in terms manufacturability and reliability. Size, space and manufacturability constrain typical packaging material choices available to meet the desired package performance. This often results in non optimal package performance and some times results in severe reliability challenges. Instead of compromising reliability expectations, the proposed approach engineers new materials to meet or exceed the desired packaging performance while meeting manufacturability criteria. In this paper, nano-particles are used as filler particles for polymer resins to modify the composite material properties. However, instead of a trial and error approach, a predictive simulation based approach is used to achieve the desired results. Advanced nonlinear finite element methodology first determines the desired material properties necessary to meet package reliability requirements. Then, achievable material property variations for a system of polymer resins and nano-particles are predicted. The optimal match is determined between achievable properties and those that will maximize package reliability. A new material was formulated using the predicted polymer resin nano-particle combination. Formulation addressed additional manufacturability issues of uniform dispersion, particle surface chemistry and a manufacturing necessity of photo definition capability. Mechanical properties were characterized to validate the property prediction capability. This validated simulation based approach is very effective in determining the ideal formulation resulting in the desired achievable properties and package reliability.Copyright