Feedthroughs produced with glass-to-metal sealing technology provide reliable electrical connections into hermetic packages.
Glass-to-metal feedthroughs are employed when other sealing options, such as epoxy resins, are no longer sufficient. They can withstand extreme conditions and provide the required reliability for critical applications.
Glass-to-metal seals are produced with special-purpose furnace equipment, using multiple temperature zones and inert or reducing atmospheres. The housings, pins and sealing glasses are assembled into oven fixtures which are then passed into the furnace for sealing.
The furnace temperature (usually at around 1000 °C) causes the sealing glass to melt and wet around the housing and the pins. To prevent oxidation of the parts, the furnace atmosphere must be tightly controlled and consists of an inert or reducing atmosphere. The actual sealing happens during the cooling phase when the glass temperature passes the strain point. The sealing mechanism can be a compression seal or a matched seal depending on the application and chosen materials. It is critical to find the right furnace setting for every part while accounting for the geometry, the used material and the total thermal mass.
After sealing, a plating process is performed for many types of feedthroughs. The function of the plating can be corrosion protection (carbon steel) or enhancing the electrical properties (plating of pins for soldering or wire-bonding). Hermetically sealed connectors often use Gold or Palladium-Nickel plated pins to enable many mating cycles.
At final inspection, multiple properties can be checked to ensure quality. Testing possibilities include: Optical inspection, hermeticity test, burst-pressure test, insulation testing.
Dietze Group precision furnaces for high-end, oxide-free quality
With the precision furnaces we developed in-house, we are especially suited to assist you with miniaturized parts, such as sensor packages. Compared to traditional belt furnaces, our equipment allows precise control of temperature and process-gas conditions. This prevents discoloration and contamination of parts, which is often seen in standard processes. Titanium parts, regarded as especially critical, can be produced completely oxide-free by our equipment, without the need to be chemically or mechanically post-treated.
Ceramics and Sapphires in combination with glass-to-metal seals
Apart from standard electrical feedthroughs, our processes additionally offer to hermetically integrate ceramic or sapphire parts into glass-to metal seals. This opens up new possibilities for various sensor applications (e.g. For optical process sensors or high-vacuum gauges).
Special technical glasses are employed in glass-to-metal sealing to match the chemical and CTE requirements of the application. These glasses are pre-produced as either sintered glass preforms or drawn glass tubes. Sintered glass preforms are created by pressing and sintering glass granulate. With this technique, custom geometries can be created, such as preforms for multiple-pin feedthroughs. However, a custom tool has to be created for each geometry and there are some limitations on wall thickness and length in relation to the diameter. Drawn glass tubes can be manufactured with a higher precision and thin walls are possible. They are, however, limited to “tubing” geometries.
The Dietze Group helps its customers with custom interconnection solutions from concept to series production. Our products are designed in close collaboration with our customers and engineered to meet the application’s specific needs.