Vacuum seal welding method for window and optic window of low temperature metal Dewar

Abstract

The present invention discloses the method of low temperature vacuum sealing and welding between the window frame and the optical window of metal Dewar. In the welding between the window frame of kovar alloy material and the optical window of infrared transmitting material, the optical window is first vacuum plated to form Cr/Au coating as the transition layer in the parts to be welded, and the welding in performed with In as welding material at low temperature. The present invention has the outstanding advantage of low temperature welding producing no negative effect on the antireflective coating in the infrared window. Using soft In as the welding material can buffer the difference between the optical window material and the kovar alloy material in expansion coefficient. The metal Dewar has gas leakage rate superior to 3E(-12) torr.liter/sec and gas releasing rate far lower than that of traditional technological process.

Description

technical field [0001] The invention relates to a low-temperature metal Dewar welding process for an infrared focal plane detector, in particular to a vacuum-tight welding method for a window frame and an optical window of a low-temperature metal Dewar. Background technique [0002] The high-vacuum low-temperature metal Dewar is the key component to ensure the normal operation of the low-temperature infrared focal plane detector. The infrared radiation signal is incident on the infrared focal plane detector through the infrared optical window of the low-temperature metal Dewar, and the infrared focal plane detector converts the radiation signal into an electrical signal for output. The infrared optical window is made of glass, quartz, germanium, silicon, zinc sulfide, zinc selenide, sapphire and other materials through optical processing. It is connected with the metal Dewar through the Kovar alloy window frame. The quality will directly affect the vacuum degree of Dewar, a...

AI Technical Summary

Problems solved by technology

[0003] At present, there are usually two methods for the vacuum-tight connection of the Kovar window frame and the infrared optical window: one is to use low-melting point PbO-SiO 2 , PbO-B 2 o 3 -SiO 2 、B 2 o 3 , Li 2 O-B 2 o 3 、Na 2 O-P 2 o 5 、B 2 o 3 -P 2 o 5 ,P 2 o 5 -SnO-ZnO series glass is directly welded by solder. Its advantage is good mechanical strength. The disadvantage is that hydrogen and helium in the air penetrate glass-based solder, and the permeability increases exponentially with the increase of temperature. Therefore, , Dewar's long-term vacuum tightness is not good

The other is to use low-temperature organic glue bonding. The advantage of this method is that the process is simple, but because the low-temperature organic glue will continue to outgas under vacuum, it will contaminate the detector, and at the same time it is not resistant to high temperature (≤80°C), it is difficult to Long-term maintenance of vacuum in Dewar

Therefore, the existing methods for sealing the Kovar window frame and the infrared optical window are not ideal, and a new method must be explored to realize the long-term vacuum-tight connection of the Kovar window frame and the infrared optical window

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