Researchers Use High-Power Diode Lasers to Microweld Thermoplastics

SANTA CLARA, Calif., June 14 -- Ohio State University researchers are using a Coherent Inc. high-power diode laser system to microweld thermoplastics that may enable lower-cost, disposable MEMS device housings for biomedical engineering, communications and sensor applications.

"One of the hottest topics in engineering research and development is micro electro-mechanical systems (MEMS)," said David Grewell, a researcher at Ohio State. "We feel that thermoplastics' chemically inert nature, low cost and ease of processing gives them a potential for use as MEMS device housing in a wide variety of applications. And, in fact, the low manufacturing cost of polymers may allow industry to fabricate disposable MEMS. But rapid, consistent and inexpensive assembly or packaging is critical to the commercialization of polymer-based MEMS."

One promising method of joining thermoplastics for MEMS housings is direct diode laser transmission welding. In this process, a laser beam passes through one of the components to be joined and is focused on the second absorbing material. Using a Coherent near-infrared F-package system, Ohio State University researchers have generated welds less than 15-µm wide. This small seam could be especially relevant in the production of small-scale biotechnology MEMS devices.

According to Grewell, diode lasers are ideal for high-precision welding because the power is controllable down to a very low level of fluence. However, on this small scale, weld testing, quality assurance and process control are far more challenging than for larger welds. Each of these stages is currently under study at Ohio State. In addition, process modeling is underway to improve theoretical understanding of the process.