Medical Device Link.

Originally Published EMDM March/April 2002

PRODUCT UPDATE

3M Microinterconnect Systems Div.

Return to Article: Electronics Open New Avenues in Device Design

Flexible circuits enable designers to fit greater functionality into smaller packages and to extend the boundaries of miniaturization in hearing aids, biosensors, and other medical devices. A core advantage of thin, lightweight Microflex Circuits, according to the 3M Microinterconnect Systems Div. (Austin, TX, USA), is their adhesive-free construction, which reduces outgassing. The products are fabricated by means of a vacuum metallization technique developed by 3M, which eliminates the need for adhesives and allows smaller features than other methods without risk of delamination. The company has adapted this process to the manufacture of its newest products, flexible circuits created with liquid-crystal polymer (LCP) film.

Engineers have long known that LCP has the potential to offer better performance characteristics than polyimide substrates, which are typically used in the manufacture of flexible circuits. The difficulty of processing LCP has prevented its widespread use, however. The combination of vacuum metallization, chemical etching of the substrate, and the ability to create fine-line features in a roll-to-roll format has enabled the firm to overcome traditional obstacles to the use of LCP.

The primary benefits of LCP, according to marketing manager Bill Balliette, are its dimensional stability and low moisture-absorption and gas-transmission rates. LCP has a water absorption rate of 0.1% compared with polyimide, which has a 1 to 3% rate. The technology is suited for "applications in which the electronics are in close proximity to any kind of fluid or gas and where there is concern about contamination of the fluids, gases, or the electronics," says Balliette. "And the fact that LCP absorbs very little moisture makes the substrate more dimensionally stable with respect to changes in humidity and temperature than alternative materials," he adds.

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