Micro-electro-mechanical systems (MEMS) are used as sensors and actuators in many electronics. Their sensing or actuating structures are produced by semiconductor front-end processes. The most popular MEMS components include microphones, inertial sensors and gyros. The MEMS components typically consist of MEMS, ASIC, substrate, wire bonds, and capping/molding. MEMS assembly has unique challenges because of their unique characteristics such as MEMS accessibility to environment and protection from environment. Nordson ASYMTEK customers are using a range of fluid dispensing equipment for applications for MEMS manufacturing.
Capping for MEMS and ASIC
MEMS die and ASIC are attached and connected with wire-bonds to a substrate. They are protected by a metal cap in many cases. The metal caps are attached with solder paste sealing on the substrate after all the components are attached. Fluid dispensers have to dispense the solder paste instead of screen printers, due to the existing components. As one board includes hundreds of MEMS components in the production process, the solder sealing line should be narrow to hundreds of microns for denser component production. The challenge for a fluid dispensers is applying finer solder paste sealing line and location accuracy.
Some MEMS components are capped at the wafer level. This wafer-level capping also needs a sealing line on the wafer. In many cases, the sealing material is glass frits rather than solder paste to create a hermetic seal for those MEMS that require a vacuum environment. This application also needs fluid dispensing equipment for finer sealing lines and location accuracy.
MEMS and ASIC protection
MEMS and/or ASIC need encapsulation sometimes for wire-bond protection, light blocking, stress diminishing and so on. The encapsulation material is silicone in many cases. The challenge is to cover the components fully and productively: odd-form components have to be covered with one or a few dots for shorter cycle time.