The package is a functional filter; it selects what should be let in from what is kept outside. What does that mean for MEMS sensor packaging?
MEMS sensor packaging has a significant impact on device cost, performance, and final integration. They need to provide mechanical protection, electrical interconnection, and thermal management.
New MEMS sensor packaging designs boast lower cost and miniature integration, allowing them to become a commodity, but they mostly rely on existing technology platforms. Therefore, the new innovative packaging designs are mostly based on the existing process blocks.
When it comes to MEMS packaging, there is a critical need for the understanding of the key parameters for each device versus an application. Producing trillions of sensors at low cost is challenging in the absence of a packaging technology roadmap.
But there is no standard roadmap for MEMS packaging because each sensor is different.
An outline of the key packaging design requirements for inertial and environmental MEMS sensors. Image courtesy of ASE Group.
For instance, consumer applications are cost-sensitive while automotive systems demand high reliability. Then, there is the next big thing in electronics—the Internet of Things. In the IoT, each module or system-in-package (SiP) has at least one MEMS device or sensor.
But there is no single packaging architecture that fits all the needs of IoT products. Instead, the packaging is driven by the needs of the end-products at the sensor fusion, MCU, and application processor level. Moreover, each MEMS sensor has its own specificities for stress decoupling, hermeticity, etc.
The IoT Case Study
"The IoT is a highly fragmented market, and you have to define packaging for each segment with specific configurations," said Christophe Zinck, senior application engineering manager at ASE Group.
So how can anyone produce sensor modules by the billions when there is no package roadmap per application? Zinck says the key is forming partnerships through the supply chain for plug-and-play modularization.
"The current MEMS packaging is low-cost, and it takes advantage of the miniature integration enabled by optimized technology platforms," Zinck said. He quoted the use of simulation and material characterizations that are key steps to define suitable package architecture and adapted BOM.
The low-stress packaging is a key trend in the MEMS sensor industry. Image courtesy of ASE Group.
Zinck added that supply chain integrators—OSAT and EMS firms—can also be helpful in carrying out a range of critical tasks from suitable package selection to supply chain management. "These companies have expertise across the board," Zinck said. "And co-development leads to faster time-to- market."
According to Zinck, the new packaging technologies—TSV last, plasma dicing, SeSUB, innovative cavity solutions, etc.—are coming but it will take time. "The packaging ecosystem has to evolve to accommodate these new technology developments," he concluded.