As the part is heated, the surrounding metal header expands, with the liquefied glass filling the space between it and the electrode. During cooling, the metal header (with its greater CTE) shrinks more than the glass and electrodes it surrounds, creating an extremely tight compression ring as the melted glass re-solidifies.

• Typical Materials In compression seals, headers are most often made from stainless steel, cold-rolled steel, or Inconel. The electrodes in compression seals are almost always iron-nickel alloys, such as 52 Alloy, Copper Cored 52 Alloy, 42 Alloy, and others.

The glasses used in compression seals are critically important to their reliable performance. Concept Group has worked with key suppliers to develop proprietary glasses whose density and other characteristics are optimized for use in compression seals, providing significantly greater strength and longer service life. If plating is required, Concept Group can perform this step in-house, for tighter quality control and timely delivery.

• Advantages Though somewhat heavier, compression seals give you very high mechanical and thermal strength, and are typically less expensive than other types, with a very wide range of applications. Concept Group's compression seals offer outstanding performance. They will withstand extreme temperatures, in some cases as much as -450°F to +840°F (-270°C to +450°C), with no loss of integrity.

• Common Applications Compression glass-to-metal seals are used in a wide variety of industries, including aerospace, automotive, microelectronics, and telecommunications, among many others. They are used in numerous applications, as well, including pressure sensors, hybrid power modules, diode packages, tilt switches, photodiode housings, microwave packages, and many more.