The present invention provides an improved method for investing radioactive sources which takes into account variations in the materials potentially making up the samples. The silicon substrate is characterized by a monocrystalline silicon lattice constant. Also, at least one of the cooling trajectories follows a non-linear temperature-time path. In the side where the distance from the edge of the deflected semiconductor chip to the edge of a module substrate is longer, the electrode pad on the first semiconductor chip and the electrode pad on the second semiconductor chip are combined with the corresponding bonding lead on the module substrate with a wire. The lamp holder improves an image display quality of a display device.