Seam solder cover sealing is a resistance heating process used to join cover and seal ring materials of Kovar™ 29=Ni/17-Co/Bal Fe alloy, CTE of 6 PPM, with 1.27µ Au/Ni plate on top for the cover and metalized seal ring on thick film. 80Au20Sn solder preform is pre-tacked to the cover seal flange for convenience. The 80Au20Sn solder is eutectic with moderate fluidity when molten. No forming gas is required. The solder joint is corrosive-resistance and compliant with MIL-STD-883 Test Method 1009 Salt Atmosphere.
Two conical shaped electrodes roll along the perimeter of the package where the cover and seal ring are joined with the 80Au20Sn eutectic. At the electrode point of contact, a low voltage electrical circuit is completed through the cover with I2R heating. As the electrodes travel on the seam the solder is molten and joins the two Au plated surfaces forming a gas-tight, hermetic seal.
Seam solder cover sealing is easily viewed. The cover is placed upon the seal ring with gravity maintaining the fit-up of the two faying surfaces. There are no special jigs, fixtures or fasteners required. Seam solder cover sealing is available from prototyping through high speed production rates sealing hundreds of packages per hour.
