A New Laser Hermetic Sealing Technique for Aluminum Package

A new laser hermetic sealing technique which combines nickel plating with laser welding has been developed for aluminum packages. Laser welding has proved to be the most promising hermetic sealing technique for the aluminum packages. However, laser welding of the package has been difficult because of aluminum´s tendency to suffer centerline cracks in the weld zone. Nickel was added in the weld zone by laser welding nickel-plated aluminum to strengthen the weld metal and prevent centerline cracks. With this aim, the optimum plating method and plating thickness were investigated. Consequently, electroless Ni-1wt%B, 5 µm in thickness was found to be best suited to the new technique, because the laser weld zone of the package exhibits a high joint strength almost equal to the tensile strength of the parent metal, and a package leakage of less than 10^-9atm · cm³/s. The reliability of the hermetically sealed package was tested in accordance with MIL-STD-202F. It was confirmed that the new technique is suitable for the aluminum package for use in space, in the stratosphere and in salt-laden air.