Tsutomu Iikawa

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 aluminums 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.

Assessment of specific environments by metal piece test kits

To investigate corrosive gases in computer installation areas, we developed an original method called the “Metal piece test kit”. The test kit, which consists of five metal strips—copper, silver, aluminum, iron and iron-nickel alloy—is mounted on an acrylic ☐ that is a little smaller than a cigarette ☐. In this method, this kit is placed in various environments for 1 month. The five metals react with gases and form corrosive products if the environment is contaminated by corrosive gases such as SO2, H2S, HCl/NaCl and H2O as humidity. By comparing the X-ray reflecting intensities of oxygen, sulfur, and chlorine contained in the corrosive products by using an X-ray fluorescence, it is able to predict the environment, determine what kinds of corrosive gases exist and judge if the environment is suited for installation of computers. By using this original method in various computer installation environments, we can adopt a suitable countermeasure to prevent system failure by corrosive gases in the computer installation environment.