There was a lot of buzz last week surrounding Apple’s announcement regarding new product releases and enhancements. With the release of the iPhone 6, iPhone 6 Plus, and the long-anticipated Apple Watch, reactions were a mixed bag. But what do these announcements mean for the world of microelectronics? One thing is certain—the MEMS industry was definitely feeling the love.
An article from IEEE Spectrum explored specific features that will include sensors in the Apple Watch that will boost the MEMS (microelectronic mechanical systems) industry. Some of these features include a heart monitor, microphone, and a pressure sensor that determines elevation.
What are MEMS?
So what are MEMS really? MEMS technology includes, essentially, very micro machines—small mechanical devices driven by electricity. They allow greater power and extensive complexity in a single, small system. MEMS devices typically combine electronic circuitry with mechanical structures to produce different outcomes. With optical switches, the key mechanical components are MEMS-based micro-machined mirrors. MEMS can also be found in products such as video projectors, accelerometers, inkjet printers, and optical switching in data communications.
Manufacturing Complex MEMS
In the past, due to the characteristically low volume and high complexity, process automation has been a low priority in the manufacturing of complex MEMS. However, especially with the release of products like the Apple Watch, volume will likely increase to a level that should prompt further consideration for automation.
MEMS are fragile and must be handled with care. The slightest shock to these devices can easily damage the microstructures causing altered performance. Human intervention in the manual packaging process can be a cause for lower yield. One of the major considerations for automation is that it allows for minimal human intervention.
Attachment Methods
There are three main attachment methods for MEMS packaging:
- Epoxy - either thermally curable or UV-light curable, can be daubed or dispensed to attach the device.
Advantages: flexible, can provide necessary support, and ensure components do not move.
- Eutectic soldering - using either a eutectic solder preform, or by having the submount pad pre-metallized with the solder alloy while the MEMS itself is metallized with gold on its attaching surface.
Disadvantages: Some MEMS manufacturers feel that eutectic attach is too rigid or induces stresses at the bondline that will inhibit the operation of the microstructure.
Advantages: Using the correct eutectic solder will provide adequate flexibility at the bondline. Also, by tightly controlling the eutectic solder reflow through accurate and repeatable temperature control, the stresses at the bondline can be minimized during the attachment process. Through this control, voiding is also minimized, further reducing the bondline stresses and increasing the quality of the mechanical, electrical, and thermal characteristics of the attach.
- Ball bumping - can be used to put small deposits of pure gold bumps on the top side of the die and inverted in a flip chip process followed by a thermalcompression bond attach. Another method of ball bumping is to deposit solder bumps on the submount pad, place the MEMS device onto the pads, and then reflow the solder.
To learn more about MEMS automation, packaging, and attachment methods, check out the resources below:
| Automating MEMS Packaging technical paper  |
Epoxy Die Attach eBook |
Eutectic Die Attach eBook |
Introduction to Automated Flip Chip Assembly eBook  |
| 3800 Die Bonder data sheet  |
Assembly Services data sheet |
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Janine Hueners
Marketing Specialist
Palomar Technologies, Inc.