X-ray transmission inspection apparatus and x-ray transmission inspection method

An X-ray transmission inspection method comprising:

• irradiating a sample with X-rays from an X-ray source;
• detecting transmitted X-rays when the X-rays pass through the sample by using an X-ray sensor installed on a side opposite to the X-ray source with respect to the sample;
• and
• calculating a planar area of a foreign object in the sample based on the transmitted X-rays detected by the X-ray sensor,
• wherein the step of calculating a planar area of a foreign object in the sample based on the transmitted X-rays detected by the X-ray sensor comprises:
• obtaining luminance distribution divided into a plurality of pixels according to luminance of the transmitted X-rays in a plane perpendicular to an irradiation direction of the X-rays;
• calculating, as a number of effective pixels, a number of the pixels having luminance reduction amounts greater than or equal to a luminance reduction threshold that is in a predetermined ratio to a maximum luminance reduction amount, which is the largest luminance reduction amount in the luminance distribution;
• and
• calculating the planar area of the foreign object based on the calculated number of effective pixels and a relationship between the number of effective pixels and the planar area of the foreign object obtained in advance.