Alumina ceramics (Al2O3) is well known as an excellent material for insulation equipment, such as insulation breaks and feed-through terminals, at room temperature. A mechanical test of the ceramics was carried out for the application of an insulation break at low temperature. The insulation break consisted of the ceramics and the transition metal with a joint between them. The brazing was applied to the joint and its mechanical strength was measured. A mechanical test of the ceramics itself was also carried out. The testing temperatures were 4.2K, 77K and room temperature. The tensile strength of the alumina was slightly increased at the liquid helium temperature comparison with room temperature. The maximum of the tensile strength on the brazing joint was achieved as 270MPa at 4.2K testing, which consists of copper and alumina of 95% purity. The stress distribution at the joint was evaluated by the finite element analysis to discuss the tensile strength of the brazing joint. A trial fabrication of the insulation break was carried out by using alumina. The results of the trial showed that the insulation break made from alumina had sufficient enough mechanical and electric properties for a low temperature application.
