Partnering makes difference for packaging, testing, assembly

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Oct. 29, 2003 – The right manufacturing partner can make the difference between failure and success for MEMS startups.

Startups are generally short on infrastructure and under pressure to generate an immediate return, while large firms have the equipment and the time to refine their processes. Given these pressures, experts say, startups need to find partners who not only can integrate packaging with sensor design, but who also can test MEMS devices and address additional aspects of assembly, such as calibration.

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“That’s really where the hurdle is going to be,” said Marlene Bourne, senior MEMS analyst at In-Stat/MDR.

Mike Steidl agreed. MEMS technology has particularly demanding requirements for startups, said the senior vice president of advanced product development for packaging firm Amkor Technology Inc. For starters, he said, MEMS often require dedicated production lines because their production and packaging processes are customized.

The clean rooms for MEMS packaging, test and assembly also often must meet a more demanding spec than the electronics industry. For example, Steidl said, if a customer wants to package a MEMS device whose moving parts are protected by a cap, Amkor can use its standard equipment lines.

 “There’s no real special handling or custom equipment or customized processes required for it,” he said. As a result, it’s a cheaper job.

On the other hand, if a device does not have a cap and its MEMS element is exposed, then Amkor’s challenge is to make the assembly process rigorously clean. Packaging, sawing and sealing must all be done in a higher quality clean room than what would ordinarily be used. In the case of high volume custom jobs such as Texas Instruments’ digital micromirror device, Amkor sets up a dedicated production line for package and assembly.

That’s certainly not the kind of thing a MEMS startup can do on its own. Further complicating matters, experts say, is the fact that startups need to pay attention to the often-overlooked differences between sensors and integrated circuits, especially calibration.

Sensors fresh off a production line usually don’t register the exact same readings, said Joe Giachino, industrial liaison at the Wireless Integrated Microsystems Engineering Research Center at the University of Michigan. They must be calibrated so that they give the correct result.

Too many MEMS companies consider calibration even more of an afterthought than packaging, Giachino said. The trend toward integrated microsystems could help alleviate that problem. For example, electronics integrated with a MEMS sensor could automatically perform a self-calibration, eliminating a time-consuming step and letting engineers off the hook for including calibration among their packaging concerns.

There will be no such shortcuts for testing devices, however. MEMS developers can avoid the unnecessary cost of packaging defective chips by testing them before they are completely packaged. Companies that don’t integrate some form of test into the package and assembly process will only have to do it later — with fully packaged products.

Given the challenges involved, there is a dearth of firms that specialize in packaging MEMS. Experts say startups must look to MEMS specialists familiar with packaging or electronics specialists familiar with MEMS.

In-Stat’s Bourne pointed to Corning IntelliSense (which announced in September that it would close) and MEMSCAP for their ability to address both MEMS processes and packaging concerns. She also singled out Teledyne, Ziptronix  and Xanoptix  for their work integrating packaging options with MEMS processes.

Xanoptix is using a micromechanical attachment process to make hybrid wafers that include both electronics and sensors all on one piece of silicon. Ziptronix is working with a bonding technology that hermetically seals MEMS and other devices. Its complementary interconnect process is intended to attach MEMS and CMOS circuits.

On an international front, Bob Mehalso, a packaging consultant with Microtec Associates, cited Grenoble, France as a “phenomenal” hot spot for microsystems development. The area is home to LETI, the French government lab pushing microsystems and developing local infrastructure. Mehalso also said the European microsystems community understands the issues better.

“MEMS is a term that was coined here in the U.S.,” he said, adding that the acronym suggests that the microelectromechanical sensor or actuator is more important than package, test and assembly.

On the other hand, “When you talk about microsystems,” Mehalso said, referring to the Europeans’ term, “that’s the whole device.” By definition, he said, a microsystem is packaged, tested and assembled.

Over time, Mehalso said, the United States’ perspective will change, especially as new companies partner with established firms. Bill Trimmer, a veteran MEMS consultant, agreed: the more industry knowledge that is shared, the better. After all, he pointed out, the easier it is to package a MEMS device, the more likely it is to make it to market. In fact, the history of commercial MEMS has largely been determined by which devices could most easily be packaged first.

Overall, Trimmer said, it sums up nicely: “Package it and they will come.”


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