Anew touch screen provides advantages for environments where cleanliness is a top priority. The CleanScreen from Microtouch Systems Inc. (Methuen, MA, USA) is the world's first touch screen to incorporate antibacterial technology registered with the US Environmental Protection Agency. A resistive membrane is permanently bonded to the glass surface of the company's ClearTek 3000 touch screen, creating a surface that inhibits the growth of bacteria and other microbial contaminants. The screen is designed for applications where hygiene is a prime concern, such as cleanroom manufacturing and hospitals.

CleanScreen was developed in response to rising consumer concern about bacterial and microbial contamination. In the United States, the number of products incorporating antibacterial properties increased from 36 in 1992 to 242 in 1998, according to a New York–based research firm. The rise of touch screen systems in healthcare and cleanroom environments also prompted the advent of this technology. According to Janet Muto, MicroTouch vice president of worldwide marketing, "The touch screen is rapidly replacing the keyboard and buttons as the common user interface in many systems because it is intuitively easy to use. CleanScreen gives users a new level of confidence that the surface of the touch screen is protected from contaminants."

Bonded to the touch screen's surface, a resistive membrane prevents the growth of bacteria and other microbial contaminants.

The membrane has several advantages over traditional touch screen cleaning procedures: it has no effect on display optics or clarity, it is resistant to contamination, and it is easily cleaned. The product is also safe for the user and the environment, because it contains no arsenic, heavy metals, or polychlorinated phenols. The resistive membrane does not leach into the environment, migrate to a user's hands, or wear off when the screen is cleaned. Moreover, unlike conventional antimicrobials and disinfectants, the technology does not allow bacteria or fungi to adapt or create resistant organisms.

MicroTouch is delivering ClearTek 3000 touch screens with CleanScreen to customers at no extra cost.

—Jodi Triplett

Novel Process Enables Automated Assembly of Flexible Circuits and Devices

Thin, flexible polyimides are a key component in miniaturized hearing aids, but they are difficult to process and do not lend themselves well to automated assembly methods. High Tec MC AG (Lenzburg, Switzerland) has overcome these difficulties by adapting techniques traditionally used with rigid substrates to the manufacture of flexible circuits.

CIC (completely in the canal) hearing aids typically require high package density, says High Tec general manager Josef Link. Because the devices must conform to the narrow confines of the auditory canal, components must be configured in a three-dimensional arrangement. Thin polyimide multilayer substrates are well suited for this application, "but they create a lot of problems during assembly and generally require additional machining," says Link.

By using a sacrificial substrate to carry a flexible polyimide used in miniature hearing aids, High Tec MC AG was able to automate the assembly process and eliminate additional machining.

"HiCoFlex technology uses a sacrificial substrate during the fabrication of highly flexible interconnection cables and multichip module deposition layers," says Link. "The substrate carries the flexible polyimide through the entire production cycle and dissolves once its job has been done," he says. The same tooling and instrumentation used with thin-film hybrids is sufficient to perform this task, adds Link.

Fully automated production of the miniaturized devices is a three-step process. The flexible circuits are first fabricated on the sacrificial substrate, after which the surface-mount device components are placed on the circuits. During the final phase, the assembly undergoes reflow soldering and underfilling, and the substrate is separated from the flexible circuit.

The film, which can have up to four metallization layers, attains a thickness of 20–70 µm.

—Norbert Sparrow

Producers of microcomponents often find themselves entangled in the intricacy of measuring a minuscule part without altering it in the process. A new fibre-optic testing machine tackles this problem by combining noncontact optical sensors and a contact probe to produce accurate measurements down to 0.5 µm. The Fiber Probe, developed by Werth Messtechnik GmbH (Giessen, Germany), was designed to provide measurements of 3-D geometry or free-form surfaces in microscale applications.

The Werth Fiber Probe (in position under video lens) can be combined with a conventional touch probe (shown at left) to provide optimized measurements of parts down to 0.5 µm.

The Fiber Probe consists of a fibre-optic stem terminating in a spherical stylus. The minute stem is highly flexible, which allows the probe to exert less than 50 µN of force on surfaces, reportedly less than any other contact probe. "This low force means that very soft or thin-walled products can now be measured without deflection, and with the highest accuracy," says Detlef Ferger, export sales manager at Werth. He adds that strong interest in the Fiber Probe has already been expressed by manufacturers of precision medical components in metal, plastic, and rubber. Werth is in discussion with clients working on such applications as valves and fittings for intravenous blood delivery, diaphragms and filters for blood analysis, plastic components in endosurgical tools, and surgical components such as forceps and biopsy scoops.

"The trend toward miniaturization has exceeded the capabilities of most gauges and inspection devices to measure parts adequately to the print requirements," says Ferger. "The combination of our Fiber Probe with a video measuring system allows manufacturers to measure microfeatures accurately, repeatably, and with confidence, so they can truly refine their manufacturing processes and ensure the quality of their products."

The Fiber Probe was developed by Werth in collaboration with the German Physikalisch-Technische Bundesanstalt (Braunschweig) as a solution to the challenge of measuring microelectromechanical devices.

—Benjamin Lichtman