| abstract |
An insulating substrate in which through holes for conductors are arranged is provided. The thickness of the insulating substrate is 25 to 100 µm, and the diameter of the through hole is 20 µm to 100 µm. The insulating substrate includes a body portion and an exposed region exposed to the through hole. The insulating substrate is made of an alumina sintered body. The relative density of the alumina sintered body is 99.5% or more, the purity of the alumina sintered body is 99.9% or more, the average particle diameter of the alumina sintered body in the body portion is 3-10 µm, and the alumina particles constituting the alumina sintered body in the exposed area Has a plate shape, and the average length of plate-shaped alumina particles is 8 to 25 µm. |