A photodiode detector array is bonded to a first surface of a first substrate and electrically coupled to the second surface of the first substrate. A shield, opaque to X-ray radiation is attached to the second surface of the first substrate. A processing chip is flip chip bonded and electrically coupled to the first surface of the second substrate. A portion of the first surface of the second substrate is physically and electrically joined to a portion of the second surface of the first substrate so as to allow processing of electrical signals from the photodiode array. The shield associated with the first substrate is aligned so as to prevent X-ray radiation from reaching the processing chip associated with second substrate. The shield and the processing chip are separated by an air space providing thermal and electrical isolation.