Apparatus and method for inspecting soldered portions

• US 4,772,125 A
• Filed: 06/19/1986
• Issued: 09/20/1988
• Est. Priority Date: 06/19/1985
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Karasaki, Kohichi, Hamada, Toshimitsu, Hiroi, Takashi, Ninomiya, Takanori, Yoshimura, Kazushi, Nakagawa, Yasuo
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US06/875,974
• Time in Patent Office: 824 Days
• Field of Search: 356/237, 356/240, 356/387, 250/458.1, 250/459.1, 250/461.1, 358/106
• US Class Current: 356/237.1
• CPC Class Codes: G01N 2021/95646 Soldering
• CPC Class Codes: G01N 21/64 Fluorescence; Phosphorescence
• CPC Class Codes: G01N 21/95684 Patterns showing highly reflecting parts, e.g. metallic elements
• CPC Class Codes: G06T 2207/10064 Fluorescence image
• CPC Class Codes: G06T 2207/30152 Solder
• CPC Class Codes: G06T 7/0006 using a design-rule based approach

Abstract

An apparatus for inspecting an appearance of soldered portions connected between the pads formed on a printed circuit board and leads of an electronic body part. A slit light beam is directed to portions to be inspected and scanned thereon with a light fluorescent image generated from the substrate portion of the printed circuit board and a dark fluorescent image generated from the leads, pads and soldered portions being detected with an image signal being generated in accordance therewith. The image signal is binarized and different functions are extracted from the binarized signal which functions are utilized in connection with other functions and previously obtained data to determine whether an abnormal portion is present or not in a predetermined position on the circuit board.

Claims

1. An apparatus for inspecting an appearance of a plurality of soldered portions connected between pads formed on a printed circuit board and leads of an electronic body part comprising:

irradiating means for irradiating a slit-like X-direciton excitation light onto leads of an electronic body part extending in a Y-direcition and for scanning in the Y-direction for generating fluorescence from a substrate portion of a printed circuit board on a part of the printed circuit board adjacent a plurality of soldered portions connected between pads formed on the printed circuit board and the leads of the electronic body part;

detecting means for detecting a two-dimensional fluorescent image formed by a light fluorescent image generated from the substance portion of the printed circuit board and a dark fluorescent image generated from said leads, said pads, and said soldered portions, said detecting means including an image detector means for converting said two-dimensional fluorescent image to an image signal;

binarization circuit means for converting said image signal to a binarized signal corresponding to said light fluorescent image and said dark fluorescent image;

Ys(x) detecting means for extracting from said binarized signal a function Ys(x) of Y coordinates for x coordinates of the X-direction indicative of the boundary initially detected as said light fluorescent image from an edge line of a body part proximate to a side edge of said pads in the Y-direction, said Ys(x) detecting means including memory means for storing said function Ys(x);

Q(x) detecting means for extracting a function Q(x) of projection data by adding picture elements corresponding to said dark fluorescent image of said binarized signal detected on an opposite side of said body part for said boundary Ys(x) in the Y-direction for x coordinates of the X-direction, said Q(x) detecting means including memory means for storing said function Q(x);

Ys₁ (x) calculating means for calculating a function Ys₁ (x) by removing line coordinates previously determined from said function Ys(x) read out from said memory means of the Ys(x) detecting means without being influenced by a shade effect of said body part or a lead shoulder portion; and

defect detecting means for detecting at least one defect of a bridge of solder and a lead slide error in accordance with signals B₁ (x) and B₂ (x) obtained by comparing said function Ys₁ (x) obtained by said Ys₁ (x) calculating means and said function Q(x) read out from said memory means of the Q(x) detecting means with pad position information B(x). and masking an x-area of said function Ys₁ (x) and said function Q(x) by the pad positional information B(x).

2. An apparatus according to claim 1, wherein the pad positional information B(x) of the defect detecting means is predetermined data.

3. An apparatus according to claim 1, wherein said defect detecting means includes adding means for adding said function Ys₁ (x) and said function Q(x) to obtain a function P(x), said defect detecting means detecting the defect in accordance with the signal B₃ (x) by comparing said function P(x) with the pad positional information B(x), and masking the x-area of said function P(x) by the pad positional information B(x).

4. An apparatus according to claim 1, wherein said defect detecting means detects the defect by utilizing predetermined values ξ

₁ and ξ

₂ or ξ

₅ for each of the function Ys₁ (x) and function Q(x).

5. An apparatus according to claim 3, wherein said defect detecting means detects the defect by utilizing predetermined values ξ

₃ for the function P(x).

6. An apparatus according to claim 1, wherein said defect detecting means further detects as the defect of a lead slide error when a width W which extends outwardly from an end of the pad in the X-direction on a tip of said lead is greater than a predetermined value ξ

₄.