NEC SCHOTT - Reed Switch Glasses

"Reed Switch Glass" – a name derived from its application: The glass encapsulation of reed switches using special cut to size precision glass tubing.

Product Description

SCHOTT’s 8516 reed glass tubing was specially developed for the encapsulation of reed switches. Typical tubing diameters range from just more than 1 to more than 5 mm. According to individual customer requirements, tubing is precisely cut to size. Sections can be as short as 5 mm for truly miniaturized applications. To ensure excellent rim quality, all sections are slightly fire-polished at both ends.

8516 is green due to its high iron content, which ensures particularly high IR absorption rates. This enables our customers to seal this glass in their process absolutely contamination free by using light (e.g. using Nd-Yag lasers or tungsten halogen lamps) rather than flames.

Product Advantages

With automated cutting and cleaning technology, SCHOTT meets the most stringent requirements for applications in the electronic and automotive fields:

Excellent accuracy in terms of glass composition and dimensional tolerances
All products are lead-free
Automated online-quality control
Uniform fire-polished ends
Suitable for sealing with all IR heat sources
Superior cleanliness for long-term reliability
Fast and flexible sampling for custom-made solutions

Applications

Reed switch glasses are specially designed for the hermetic encapsulation of reed switches:

Each reed switch has two electrically conductive metal contacts (reeds). The ends of these two reeds are hermetically sealed into the opposite ends of the SCHOTT glass tube. While the switch is open, the reeds do not touch each other and form a gap. An electrical circuit is created when a magnetic field causes the encapsulated contacts to close. Once the magnetic field ceases, the stiffness of the reeds causes them to separate again.

Due to the hermetic encapsulation, reed switches are extremely reliable over millions of switching cycles. Another advantage is that they don’t consume any power in the “stand-by” mode. This sets them apart from semiconductor solutions.

End-use applications are found in a variety of fields:

Automotive applications include brake fluid control, seat belt or crash sensors.
Home appliance applications include switches for electrical appliances such as toothbrushes, water heaters etc.
In semiconductor test equipment, reed switches guarantee loss-free switching of signals during test cycles.

Technology

The fabrication of glass tubes is one of SCHOTT's key competencies.

All high-precision cutting equipment has been developed in-house. Key developments in the last years were focused on reducing dimensional tolerances as well as miniaturization. Washing and packing in modern clean rooms ensures excellent cleanliness and direct usability in our customers’ processes.

Features / Specifications

Please refer to the following table for properties of SCHOTT’s 8516 reed glass:

Glass number		8516
Sealing alloy		NiFe 52
Evaporation tendency 1)		o
CTE	10^-6/K	8.9
Transformation temperature	°C	440
Softening point (10^7.6dPas)	°C	650
Working point (10⁴dPas)	°C	990
Density	g/cm³	2.56
Modulus of elasticity	GPa	72
Refractive index		1.516
t_k100 (DIN 52326)	°C	250
Electrical volume resistivity (in cm) log ρ at 250°C		8.1
Electrical volume resistivity (in cm) log ρ at 350°C		6.4
Dielectric constant	(25°C, 1MHz)	6.5
Loss angle tanδ	(25°C, 1MHz)	25x10^-4
Classes of chemical stability
Transmiss. of 0.5 mm glass at 1.1μm		16
Water resistance (DIN 12111) class		3
Acid resistance (DIN 12116) class		1
Alkali resistance (DIN 52322) class		2

Forms of Supply and Product Packaging

Reed glass tube sections are packed in antistatic trays
Other special packaging options upon request
Products can be delivered with special cleaning and packing in clean room conditions

Quality Assurance

For information on our quality assurance programs, please refer to our quality assurance pages.