Examination of articles by x-rays

Claim 1

A method of closely examining an article of manufacture for normally invisible defects in manufacture comprising: holding the article to be examined in an accurately controlled position and orientation relative to an x-ray film; exposing said article and film to x-rays for a predetermined interval of time and with a predetermined intensity and direction of radiation; developing said film into a transparency containing a visible image of the density features of said article; superimposing said developed transparency, for viewing, over another x-ray photograph of the same article taken at a different stage of manufacture thereof with the article held in identical position and orientation and exposed to x-radiation; adjusting said superimposed x-ray photographs into registration relative to an accurate frame of reference common to both radiographs; and visually inspecting said adjusted superimposed radiographs for signs of variation in the images of said article density features.

Claim 2

A method of closely examining an article of manufacture for normally invisible defects in manufacture comprising: holding the article to be examined in an accurately controlled position and orientation relative to an x-ray film; exposing said article and film to x-rays for a predetermined interval of time and with a predetermined intensity and direction of radiation; developing said film into a transparency containing a visible image of the density features of said article; superimposing said developed transparency, for viewing, over another x-ray photograph of the same article taken at a different stage of manufacture thereof with the article held in identical position and orientation and exposed to x-radiation; adjusting said superimposed x-ray photographs into registration relative to an accurate frame of reference common to both radiographs; and visually inspecting said adjusted superimposed radiographs for signs of variation in the images of said article density features.

Claim 9

A method of examining laminar printed circuit device articles for positional deviations in the density features of individual lamina caused by stresses of the lamination process comprising: at a first particular stage of said lamination process exposing said article to x-rays while said article is held in a fixed position and orientation relative to an x-ray sensitive radiographic film, said article being held in contact with said film over a substantial surface area of interest thereof; at the sAme said first particular stage of said lamination process exposing said first film separately to x-rays without said article, through a reference-marking template held adjacent said first film in the same relative position and orientation as said article during said first mentioned step of exposing; said x-rays directed respectively at said article and template being in the same direction relative to said film whereby an accurate composite image of mark openings in said template and features of said article as formed at said first particular stage is produced on said first film; at a second particular stage of said lamination process repeating the above steps of separately exposing said article and template to x-rays in the said predetermined position and orientation relative to a second film, to produce a composite image on said second film of the said template mark openings and the density features of said article as formed at said second particular stage; developing said first and second films into respective first and second visible radiographs of said composite x-ray exposure images; and examining said first and second photographs comparatively employing said reference marks as a common frame of reference for locating corresponding density features in said photographs.

Claim 10

A method of examining laminar printed circuit device articles for positional deviations in the density features of individual lamina caused by stresses of the lamination process comprising: at a first particular stage of said lamination process exposing said article to x-rays while said article is held in a fixed position and orientation relative to an x-ray sensitive radiographic film, said article being held in contact with said film over a substantial surface area of interest thereof; at the sAme said first particular stage of said lamination process exposing said first film separately to x-rays without said article, through a reference-marking template held adjacent said first film in the same relative position and orientation as said article during said first mentioned step of exposing; said x-rays directed respectively at said article and template being in the same direction relative to said film whereby an accurate composite image of mark openings in said template and features of said article as formed at said first particular stage is produced on said first film; at a second particular stage of said lamination process repeating the above steps of separately exposing said article and template to x-rays in the said predetermined position and orientation relative to a second film, to produce a composite image on said second film of the said template mark openings and the density features of said article as formed at said second particular stage; developing said first and second films into respective first and second visible radiographs of said composite x-ray exposure images; and examining said first and second photographs comparatively employing said reference marks as a common frame of reference for locating corresponding density features in said photographs.