Method for inspecting filled state of via-holes filled with fillers and apparatus for carrying out the method

A method for inspecting the filled state of a plurality of via-holes which pass through a circuit board from a surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said method comprising the steps of:

• irradiating light to the surface of said circuit board in a plurality of directions so as to generate shadows depending on a concave or convex state of the fillers in the via-holes;
• detecting independently optical images of a plurality of shadows of a first via-hole generated by light irradiation in said plurality of directions;
• identifying whether the filler in said first via-hole is in the concave state or convex state according to a positional relationship of the detected images of said shadows;
• and detecting lengths of the detected images of said shadows and deciding whether the concave state of the filler in the via-hole is within a predetermined allowance according to the detection results.

A method for inspecting the filled state of a plurality of via-holes which pass through a circuit board from a surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said method comprising the steps of:

• irradiating light to a plurality of positions different from each other on the surface of the circuit board in a plurality of directions different form each other so as to generate shadows depending on a concave or convex state of the fillers in the via-holes;
• detecting independently optical images of a plurality of shadows of a via-hole generated by light irradiation in said plurality of directions;
• identifying whether the filler in one of the via-holes is in the concave state or convex state on the basis of a positional relationship of the detected images of said shadows;
• and detecting lengths of the detected images of said shadows and deciding whether the concave state of the filler in said one of the via-holes is within a predetermined allowance according to the detection results.

A method for inspecting the filled state of a plurality of via-holes which pass through a circuit board from a surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said method comprising the steps of:

• irradiating light to the surface of the circuit board so as to make the brightness of an image of the wall of a via-hole different from the brightness of an image of the filler in the via-hole;
• detecting an optical image of the surface of said circuit board irradiated by said light;
• detecting an area of each image of the fillers in said via-holes, existing in the detected image of said surface;
• and deciding that the amount of filler in the via-hole corresponding to said each image of the fillers is lacking when the detected area of said each image of the fillers is smaller than a predetermined value.

A method for inspecting the filled state of a plurality of via-holes which pass through a circuit board from a surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said method comprising the steps of:

• irradiating light to the surface of the circuit board in a plurality of directions so as to generate shadows depending on a concave or convex state of the fillers in the via-holes;
• detecting an optical image of the surface of said circuit board irradiated by said light;
• detecting one side boundary of each of the shadows of one via-hole, which exist in the detected optical image of said surface and are generated by light irradiation in said plurality of directions;
• identifying whether the filler in said one via-hole is in the concave state or convex state on the basis of a mutual position relationship of the detected boundaries;
• detecting a length of said each of the shadows and deciding whether the concave state or convex state of the filler is within a predetermined allowance according to the length detection results;
• and detecting an area of an image of the filler according to differences between the brightness of the board surface or of the via-hole wall and the brightness of the filler in the via-hole in the detected optical image of said surface, and deciding whether an amount of the filler in the via-hole is sufficient according to the detected area of the image of the filler.

A method for inspecting the filled state of a plurality of via-holes which pass through a circuit board from a surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said method comprising the steps of:

• detecting an optical image of the circuit board having the plurality of via-holes filled with the substance;
• dividing the detected optical image into a plurality of image areas each area containing an image of a via-hole respectively;
• analyzing the image existing in each of said image areas;
• and deciding whether a filled state of the via-hole whose image exists in each of said image areas is sufficient on the basis of the analytical results.

An apparatus for inspecting the filled state of a plurality of via-holes which pass through a circuit board from a surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said apparatus comprising:

• means for irradiating light to the surface of the circuit board in a plurality of directions so as to generate shadows depending on a concave or convex state of the fillers in the via-holes;
• means for detecting independently optical images of a plurality of shadows of a first via-hole generated by light irradiation in said plurality of directions;
• means for identifying whether the filler in said first via-hole is in the concave state or convex state on the basis of a positional relationship of the detected images of said shadows;
• and means for calculating lengths of the detected images of said shadows and deciding whether the concave state of the filler in the via-hole is within a predetermined allowance according to the calculation results.

An apparatus for inspecting the filled state of a plurality of via-holes which pass through a circuit board from a surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said apparatus comprising:

• means for irradiating light to a plurality of positions different from each other on the surface of the circuit board in a plurality of directions different from each other so as to generate shadows depending on a concave or convex state of the fillers in the via-holes;
• means for detecting independently optical images of a plurality of shadows of a first via-hole generated by light irradiation in said plurality of directions;
• means for identifying whether the filler in said first via-hole is in the concave state or convex state on the basis of a positional relationship of the detected images of said shadows;
• and means for calculating lengths of the detected images of said shadows and deciding whether the concave state of the filler in the via-hole is within a predetermined allowance according to the calculation results.

An apparatus for inspecting the filled state of a plurality of via-holes which pass through a circuit board from a surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said apparatus comprising:

• means for irradiating light to the surface of the circuit board so as to make the brightness of an image of the wall of a via-hole different from the brightness of an image of the filler in the via-hole;
• means for detecting an optical image of the surface of said circuit board irradiated by said light;
• means for calculating an area of each image of the fillers in said via-holes in the detected image of said surface;
• and decision means for deciding that the filler in the via-hole corresponding to said each image of the fillers is lacking when the calculated area of said each image of the fillers is smaller than a predetermined value.

An apparatus for inspecting the filled state of a plurality of via-holes which pass through a circuit board from the surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said apparatus comprising:

• means for irradiating light to the surface of the circuit board in a plurality of directions so as to generate shadows depending on a concave or convex state of the fillers in the via-holes;
• means for detecting an optical image of the surface of the circuit board irradiated by said light;
• means for detecting one side boundary of each of the shadows of a first via-hole, which exist in the detected optical image of said surface and are generated by light irradiation in said plurality of directions;
• means for identifying whether the filler in said first via-hole is in the concave state or convex state on the basis of a mutual position relationship of the detected boundaries;
• means for calculating a length of said each of shadows and deciding whether the concave state or convex state of the filler is within a predetermined allowance according to the calculation results;
• and means for detecting an image of the filler according to differences between the brightness of the board surface or of the via-hole wall and the brightness of the filler in the via-hole in the detected optical image of said surface, and deciding whether the amount filler in the via-hole is sufficient according to the detection results.

An apparatus for inspecting the filled state of a plurality of via-holes which pass through a circuit board from a surface thereof to the opposite surface and are filled with a substance whose electrical characteristics differ from the electrical characteristics of said circuit board, said apparatus comprising:

• means for detecting an optical image of the circuit board having the plurality of via-holes filled with the substance;
• means for dividing said detected optical image into a plurality of image areas, each said area containing an image of a via-hole respectively;
• means for analyzing the image existing in each of said image areas;
• and decision means for deciding whether a filled state of the via-hole whose image exists in said each of image areas is sufficient on the basis of the output of said analytical means.