Reed Switch Production
Building Reed Switches is no easy job. Being the most modern factory of its kind in Europe our production in Thuringia is a world of its own. The size of these high precision components is extremely small, the coating ultra-thin, and meticulous work is required in every step of the production. This micro-technology enables the mass production of high quality products at competitive prices.
A Reed Switch consists of relatively few components: A precisely formed and cut glass capillary; two switching blades sputtered with hard metal; and inert gas comprised of nitrogen.
Extreme cleanliness and high precision are a must for the manufacturing of Reed Switches and therefore the whole process is carried out in a clean room environment. This requires constant professional supervision, as even the microscopic particles can threaten the reliability of the components. The entire manufacturing process takes place in a Classification 1000 clean room under strict control.
The switching blades are made of a nickel-iron-alloy and are delivered to us in large sheets. The sheets are manufactured by using a special etching technique.
The highly precise contours are then punched out on a press. Separated strips, each containing 20 Reed Switches blades are then soft annealed. This takes place in a special oven with reduced atmosphere and takes around 12 hours. During this process of annealing a special temperature profile has to be followed. The magnetic remenance is thereby removed from the metal, which makes the reed magnetically stable and helps to prevent malfunctioning.
The blades are then thoroughly cleaned in a CO2-cleaning operation, the tiny CO2 crystals are blasted on the metal surface in order to remove the microscopic particles.
The soft annealed strips are now coated with rhodium or rhutenium by a sputtering process. These layers have a thickness of one micron and have to be applied most accurately. The underlayer is a sputtered layer of tungsten of around 2,2 microns. This complex ion exchange procedure is carried out in a high vacuum chamber and constantly monitored by computer. A precise layer thickness measure instrument using X-ray technology enables this highly sensitive processing.
The glass tubes are another special concern. Once a particle of any kind has entered the glass tube, it is almost impossible to remove. In order to avoid this occurrence we purchase the glass in continuous tubes of 1,20 m in length. These tubes are closed on either end and so no debris whatsoever can enter the tubes.
Even for external professional companies the cutting of high-precision glass capillaries poses many difficulties. Our engineers have not only mastered this challenge, they have gone one step further. Instead of using the conventional scoring technology the apply laser technology and thereby precise geometries can be guaranteed. This system is able to cut even the world’s smallest Reed Switch, our STM 4 with a length of only 4 mm.
The next step is to seal these structures consisting of the glass body and the nickel-iron-blades – as usual with the highest precision, cleanliness and care.
We have made our decision in favor of the most innovative option: sealing by laser. These laser robots are located in the clean room and have been developed specifically for our needs.
The sealing process is monitored by highly accurate process controls and sensors. The laser energy is distributed evenly to all 20 assemblies by a scanner, thereby ensuring precise and consistent seals. The process parameters are monitored constantly, which results in a consistent high quality of our components.
During this process the air is completely removed and the Reed Switch is filled with an inert gas mixture consisting mostly of nitrogen prior to sealing. Using this process, the insulation voltage can be increased considerably.
After sealing, the glass is annealed whereby any residual stress is removed from the glass structures. The external lead of the Reed Switch are now tinned to ensure an as satisfactory electrical connection as possible. The tinning takes place in a fully automatic tinning galvanic. A coating of pure tin of a thickness of around 8-12 microns is applied in a lead-free procedure, according to the new RoHS regulations.
Custom-designed test- and handling systems guarantee that our quality Reed Switch is checked extensively for all critical parameters. First, the lead frames, strips consisting of 20 Switches each, are transported to the measuring systems automatically. Then the Switches are separated from the lead frames by special punching tool. In the measuring station the Reed Switches are further tested with an increased voltage of around 350 Volt. A positive result shows that the Reed Switch is filled with gas and sealed properly. All parts showing negative results are sorted out.
After having passed the high voltage test, all critical parameters like magnetic sensitivity, contact resistance, stability and remanence of every switch are tested. The good parts are separated in tightly selected groups and packed accordingly. To ensure our high quality we further take a sample quantity out each lot, which is tested under full load or its life span.
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