New glass-to-metal seal is close to perfect

March 17, 2005
A process that takes place at temperatures to 1,000°C hermetically seals optical glass to an alloy frame.

The empty frame on the left is produced by FloMet's metal-injection technology of an alloy with the same coefficient of thermal expansion as the glass in front of it. The process joins the two at high temperature to produce a stress free bond. The glass is polished to optical requirements after joining (right), for the lowest stresses possible in a hermetically sealed window.


A process that takes place at temperatures to 1,000°C hermetically seals optical glass to an alloy frame. A key point: the glass and alloy have the same coefficient of thermal expansion. The alloy, specially formulated by ceramic engineers and metallurgists, is then manufactured using Metal Injection Technology (MIT) at FloMet LLC, DeLand, Fla. Leak tests on the glass-to-metal seal come in at less than 2 X 10 10 atm-cc/sec of helium. This is significantly lower than conventional sealing methods.

The seal goes on optical windows for protecting cameras, photodetectors, and imaging semiconductors such as CCDs, CMOS, and optical MEMS devices used in highdefinition televisions. The oxide-free process, developed with Tekna Seal LLC, Minneapolis, solves quality problems stemming from thermal-expansion mismatches in older methods. These problem manifested themselves as compromises between seal reliability and image quality. The seal also better protects optical equipment from contamination such as hydrocarbons and moisture, thereby extending its useful life.

"Until now, such windows were made by first selecting an alloy then finding a glass that matched its coefficient of thermal expansion (CTE) as closely as possible," says FloMet manager of materials technology Mitchell Gross. "The optical properties of the glass were secondary to matching the CTE of the alloy. A thermal-expansion mismatch between the alloy frame and glass can weaken the bond while placing stress on the glass. Sufficiently high stress distorts the transmitted image," he adds.

Other pluses include sealing a wider range of optical glasses than would be possible with conventional methods, and a significant cost advantage. Also, the MIT method allows making material in smaller batches than those used to make conventional wrought alloys.

MAKE CONTACT

FloMet LLC,
(386) 736-4890,
[email protected]

Sponsored Recommendations

NEW Low Profile, Ultra Compact Power Supplies

March 13, 2024
Learn more HERE about Altech's Power supplies!

Altech's Liquid Tight Strain Relifs Catalog

March 13, 2024
With experienced Product Engineers and Customer Service personnel, Altech provides solutions to your most pressing application challenges. All with one thought in mind - to ensure...

Industrial Straight-Through Cable Gland

March 13, 2024
Learn more about Altech's cable glands and all they have to offer for your needs!

All-In-One DC-UPS Power Solutions

March 13, 2024
Introducing the All-In-One DC-UPS, a versatile solution combining multiple functionalities in a single device. Serving as a power supply, battery charger, battery care module,...

Voice your opinion!

To join the conversation, and become an exclusive member of Machine Design, create an account today!