Circuit board misalignment detection apparatus and method

• US 6,353,327 B2
• Filed: 05/13/1998
• Issued: 03/05/2002
• Est. Priority Date: 05/13/1997
• Status: Expired due to Fees

• Current Assignee: Nidec-Read Corporation (Nidec Corporation)
• Original Assignee: Nidec-Read Corporation (Nidec Corporation)
• Inventors: Nishikawa, Hideo
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Nguyen, Jimmy
• Application Number:
  US09/078,250
• Publication Number:
  US 20020011861A1
• Time in Patent Office: 1,392 Days
• Field of Search: 324/758, 324/754, 324/755, 324/661, 324/662, 324/452, 324/457, 324/158.1, 324/130, 324/71.5, 324/537, 228/180.21, 228/180.22
• US Class Current: 324/750.17
• CPC Class Codes: G01R 1/06794 Devices for sensing when probes are in contact, or in position to contact, with measured object
• CPC Class Codes: G01R 31/2805 Bare printed circuit boards
• CPC Class Codes: G01R 31/2887 involving moving the probe head or the IC under test; docking stations moving single probes G01R1/06705; moving individual probes in multiple probes G01R1/07392

Abstract

Position detection electrodes are disposed so as to be point-symmetrical relative to an arbitrary point on a line X that extends almost along the center of a printed pattern on an opposite circuit board and is parallel with the Y axis. Position detector electrodes are disposed in the same manner. A probe selector switch section can provide a probe selection signal, and a position detector sensor selection which section can provide a signal for selecting among the position detection electrodes. A detected voltage varies depending on how the position detection electrode is opposed to a printed pattern. Thus, misalignment can be detected by detecting the opposition relationship between each of the position detection electrodes and the printed pattern.

Claims

1. A method for detecting misalignment between printed circuit patterns on a circuit board at its inspection position and probes carried on a jig for the circuit pattern conductivity inspection in a printed circuit board inspection apparatus, the method comprising the steps of:

bringing the circuit board and probes into their relative inspection positions;

facing a pair of electrodes with a gap to respective predetermined portions of an electrically conductive wiring of the circuit patterns to form capacitive couplings between the electrodes and the portions of the conductive wiring, the electrodes being associated with the jig to move correspondingly and arranged such that the electrodes are at different positions along the center line of the conductive wiring and in the direction of width of the conductive wiring, and when the circuit patterns and the probes are at expected relative positions, the electrodes being located such that the electrodes are point symmetrical with each other with respect to a point on a center line extending along the center of the conductive wiring and that the electrodes cover the same amount of areas of the conductive wiring;

supplying a test signal to the conductive wiring, the test signal being of the nature changing its electric parameter to be transmitted through the capacitive coupling;

comparing the test signals transmitted to the electrodes through the capacitive couplings, the transmitted test signal being representative of the areas of the circuit pattern faced by the electrodes; and

determining alignment between the probes and circuit patterns in accordance with the comparison.

2. A method for detecting misalignment between the printed circuit patterns and the probes according to claim 1, further comprising the steps of:

facing a second pair of electrodes with a gap to respective predetermined portions of a second electrically conductive wiring of the circuit patterns to form capacitive couplings between the second pair of electrodes and the portions of the conductive wiring, the second conductive wiring being at right angle with the first conductive wiring, the second pair of electrodes being associated with the jig to move correspondingly and arranged such that the electrodes are at different positions along the center line of the second conductive wiring and in the direction of width of the second conductive wiring, and when the circuit patterns and the probes are at expected relative positions, the electrodes being located such that the electrodes are point symmetrical with each other with respect to a point on a center line extending along the center of the second conductive wiring and that the electrodes cover the same amount of areas of the second conductive wiring;

supplying a test signal to the second conductive wiring, the test signal being of the nature changing its electric parameter to be transmitted through the capacitive coupling;

comparing the test signals transmitted to the second pair of electrodes through the capacitive couplings, the transmitted test signal being representative of the areas of the conductive wiring faced by the second pair of electrodes; and

determining alignment between the probes and circuit patterns in accordance with the comparisons of test signals transmitted to the first and second pairs of electrodes.

3. A method for detecting misalignment between the printed circuit patterns and the probes according to claim 1, further comprising the steps of:

inspecting conductivity of the circuit patterns in advance of the detection of the misalignment; and

conducting detection of the misalignment when discontinuation of any circuit pattern is detected.

4. A method for detecting misalignment between the printed circuit patterns and the probes according to claim 2, wherein the first and second conductive wirings are electrically connected with each other, and a test signal is being supplied to the first and second circuit patterns.

5. A method for detecting misalignment between the printed circuit patterns and the probes according to claim 1, wherein the step of supplying a test signal including a substep of turning on a switch to connect a constant voltage source to the circuit patter faced by the probes.

6. A method for detecting misalignment between printed circuit patterns on a circuit board at its inspection position and probes carried on a jig for the circuit pattern conductivity inspection in a printed circuit board inspection apparatus, the circuit board having a reference wiring formed thereon, the method comprising the steps of:

facing a pair of electrodes with a gap to respective predetermined portions of the reference wiring to form capacitive couplings between the electrodes and the portions of the reference wiring, the electrodes being associated with the jig to move correspondingly and arranged such that the electrodes are at different positions along the center line of the reference wiring and in the direction of width of the reference wiring, and when the circuit patterns and the probes are at expected relative positions, the electrodes being located such that the electrodes are point symmetrical with each other with respect to a point on a center line extending along the center of the reference wiring and that the electrodes cover the same amount of areas of the reference wiring;

supplying a test signal to the reference wiring, the test signal being of the nature changing its electric parameter to be transmitted through the capacitive coupling;

comparing the test signals transmitted to the electrodes through the capacitive couplings, the transmitted test signal being representative of the areas of the reference wiring faced by the electrodes; and

determining alignment between the probes and circuit patterns in accordance with the comparison.

7. In a printed circuit board testing apparatus for testing conductivity of the circuit patterns formed on a printed circuit board, a device for detecting the misalignment between the circuit patterns and probes carried by a jig of the testing apparatus, comprising;

a first pair of electrodes fixedly carried by the jig and arranged such that, when the circuit patterns and probes are at their expected relative inspection positions, the electrodes face a selected wiring of the circuit patterns with a gap to form capacitive couplings with the wiring faced thereby, with the electrodes shifting sideways and lengthwise of the wiring from each other and being point symmetrical with each other with respect to a point on the center line of the wiring, whereby the electrodes cover the same amount of area of the wiring respectively;

a test signal supplier for supplying a test signal to the selected wiring, the test signal having a nature changing its electric parameter to be transmitted through the capacitive coupling;

a first comparator for comparing the test signals received by the electrodes through the capacitive coupling, the test signals being a function of the areas of the selected circuit pattern faced by the electrodes; and

misalignment detector for determining alignment and misalignment between the circuit patterns and probes in accordance with the output of the first comparator.

8. A device for detecting the misalignment between the circuit patterns and probes according to claim 7, wherein the selected wiring has a first line and second line which are at right angle with each other, and the first pair of electrodes faces the first line, and the device further comprising a second pair of electrodes fixedly carried by the jig and arranged such that, when the circuit patterns and probes are at their expected relative inspection positions, the electrodes face the second line with a gap to form capacitive couplings with the circuit patterns faced thereby, with the electrodes shifting sideways and lengthwise of the circuit pattern from each other and being point symmetrical with each other with respect to a point on the center line of the second line and the test signals received by the electrodes through the capacitive coupling, the test signals being as a function of the areas of the selected circuit pattern faced by the electrodes, whereby the electrodes cover the same area respectively and a second comparator for comparing the outputs of the second pair of electrodes;

and wherein said misalignment detector detects misalignment in two directions in accordance with the outputs of the first and second comparators.