JP2006343103A - Circuit board inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board inspection device capable of accurately inspecting a circuit board. <P>SOLUTION: The circuit board inspection device comprises a signal output section 2 for outputting a signal for inspection including an alternating current signal of a predetermined cycle, and a magnetic field detection section 3 that detects, as a detection signal Ss, a magnetic field generated by applying the signal for inspection to a conductor pattern of the circuit board, extracts a component corresponding to the cycle of the alternating current signal from the detection signal Ss, and outputs an extraction signal Se to it. The circuit board inspection device determines goodness/badness of the circuit board based on the extraction signal Se. In this case, the signal output section 3 generates the signal Ss for inspection by superimposing a direct current signal on the alternating current signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circuit board inspection apparatus configured to be able to inspect a circuit board.

As this type of circuit board inspection apparatus, an inspection apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-131365 is known. This inspection apparatus includes an inspection unit, a power source, a control circuit, a measuring instrument, and the like, and is configured to be able to inspect circuit circuit breaks and short circuits on a circuit board. When inspecting two circuit wirings to be inspected on the circuit board using this inspection apparatus, first, current (inspection signal) is supplied from the power source to the two circuit wirings. At this time, a magnetic field is generated from both circuit wirings, and the magnetic sensor of the inspection unit detects this magnetic field and outputs an electrical signal. Next, the measuring device compares the electrical signal output from the magnetic sensor with a value obtained in advance through a preliminary experiment or the like to determine whether the circuit wiring is disconnected or short-circuited. Thereby, the disconnection and the short circuit of the circuit wiring in the circuit board are inspected.
JP 2002-131365 A (page 5-8, FIG. 2)

  However, the conventional inspection apparatus has the following problems. In other words, in this inspection apparatus, the circuit wiring is inspected for disconnection or short circuit by comparing the magnetic field generated in the circuit wiring when the inspection signal is supplied with the value obtained in advance. In this case, when the inspection signal supplied to the circuit wiring is a direct current, a magnetic field that does not change with time (less changes) is generated. Therefore, it is determined whether the magnetic field detected by the magnetic sensor is due to geomagnetism or the like. It becomes difficult. For this reason, in an inspection using this type of inspection apparatus, it is preferable to use an AC signal as an inspection signal supplied to the circuit wiring. On the other hand, in this type of inspection apparatus, since the probe and the magnetic sensor are moved by the moving mechanism, a high frequency is generated from the power source or the like. In addition, high and low frequencies may be generated from various facilities existing around the inspection apparatus. As a result, it becomes difficult to accurately measure the magnetic field generated by the inspection signal due to the influence of the magnetic field generated due to these high and low frequencies flowing through the circuit wiring on the circuit board to be inspected. ing. Therefore, this inspection apparatus has a problem that it is difficult to accurately inspect the circuit board.

  The present invention has been made in view of such problems, and a main object of the present invention is to provide a circuit board inspection apparatus capable of accurately inspecting a circuit board.

  In order to achieve the above object, the circuit board inspection apparatus according to claim 1 includes a signal output unit that outputs an inspection signal including an alternating-current signal having a predetermined period, and application of the inspection signal to the conductor pattern of the circuit board. A magnetic field detection unit that detects a generated magnetic field as a detection signal and extracts a component corresponding to the period from the detection signal and outputs the extraction signal, and determines whether the circuit board is good or bad based on the extraction signal . In this case, “inspection of the circuit board” includes a quality inspection of the connection state between the electronic component mounted on the circuit board and the conductor pattern of the circuit board and a quality inspection of the conductor pattern.

  According to a second aspect of the present invention, in the circuit board inspection apparatus according to the first aspect, the signal output unit generates the inspection signal by superimposing a direct current signal on the alternating current signal.

  According to a third aspect of the present invention, in the circuit board inspection apparatus according to the second aspect, the signal output unit is configured to be able to be superimposed on the alternating current signal by switching the polarity of the direct current signal.

  According to the circuit board inspection apparatus of the first aspect, the magnetic field detection unit extracts the component corresponding to the period of the AC signal from the detection signal and outputs the extraction signal, for example, the power in the moving mechanism for moving the probe The influence of the magnetic field generated due to the high frequency from the source and the low frequency from the periphery of the circuit board inspection apparatus flowing through the conductor pattern of the circuit board can be sufficiently reduced. Therefore, the circuit board can be accurately inspected by the amount that the influence of the magnetic field caused by these is reduced.

  According to another aspect of the circuit board inspection apparatus of the present invention, the signal output unit generates and outputs a signal in which a DC signal is superimposed on an AC signal as an inspection signal. When conducting a pass / fail inspection of the connection state between the electronic components mounted on the circuit board and the conductor pattern of the circuit board and a pass / fail inspection of the conductor pattern at the location where the conductor patterns overlap, It is possible to restrict the inspection signal from flowing through a predetermined conductor pattern. Therefore, since the generation of a magnetic field in this predetermined conductor pattern can be suppressed, the influence of the magnetic field from this conductor pattern can be reduced at or near the inspection target location, and the detected magnetic field strength and the reference at that location are reduced. As a result of clarifying the difference from the magnetic field intensity, these pass / fail inspections based on the difference can be accurately performed.

  Further, according to the circuit board inspection apparatus of claim 3, by configuring the signal output unit so that the polarity of the DC signal is switched and can be superimposed on the AC signal, the shape of each conductor pattern on the circuit board and the state of the overlapping, Further, by switching (reversing) the polarity of the DC signal in accordance with the internal structure of the electronic component mounted on the circuit board, generation of a magnetic field that affects the circuit board inspection can be further reduced.

  Hereinafter, the best mode of an inspection apparatus according to the present invention will be described with reference to the accompanying drawings.

  First, the configuration of the inspection apparatus 1 will be described with reference to the drawings.

  An inspection apparatus 1 shown in FIG. 1 is an example of a circuit board inspection apparatus according to the present invention, and is configured to be able to inspect whether the electronic circuit board 100 shown in FIG. In this case, the electronic circuit board 100 includes a circuit board 101 and an integrated circuit 111 as an electronic component mounted on the circuit board 101, as shown in FIG. As an example, the circuit board 101 is a board having a three-layer structure including a ground layer 101a, a power supply layer 101b, and a signal layer 101c. Each of the layers 101a, 101b, and 101c includes a conductor pattern 102a as a ground wiring and a power supply wiring. And a conductor pattern 102c (hereinafter also referred to as “conductor pattern 102” when the conductor patterns 102a, 102b, and 102c are not distinguished) are formed. The integrated circuit 111 is, for example, a BGA (Ball Grid Array) type integrated circuit in which a plurality of pads (electrodes as an example of connection portions) 112, 112,. The pads 112 are connected to the conductor pattern 102 of the circuit board 101.

  On the other hand, the inspection apparatus 1 includes a signal output unit 2, a magnetic field detection unit 3, a moving mechanism 4, a control unit 5, and an operation unit 6, as shown in FIG. The signal output unit 2 includes, for example, an AC signal output circuit 21 that outputs an AC signal Sa shown in FIG. 3 and a DC signal output circuit 22 that outputs a DC signal Sd shown in FIG. In this case, the signal output unit 2 generates and outputs an inspection signal St (see FIG. 5) in which the DC signal Sd is superimposed on the AC signal Sa in accordance with the control of the control unit 5. In addition, as shown in FIG. 2, the signal output unit 2 includes probes 23a, 23b, and 23c (hereinafter referred to as distinctions) for applying inspection signals St to the conductor patterns 102a, 102b, and 102c of the electronic circuit board 100, respectively. When not, it is also referred to as “probe 23”. As shown in FIG. 1, the magnetic field detection unit 3 includes a magnetic field sensor 31 and a filter 32. For example, the magnetic field sensor 31 is configured by an MR (Magneto Resistance) sensor, detects a magnetic field generated in the conductor pattern 102, and outputs a detection signal Ss. The filter 32 functions as an extraction unit, and as an example, is configured by a narrowband bandpass filter. Specifically, the filter 32 passes only a frequency component in a narrow band centered on the frequency f1 of the test signal St (AC signal Sa) from among a plurality of frequency components included in the detection signal Ss. The extracted signal Se including the component is output. Here, the reciprocal of the frequency f1 corresponds to a predetermined period in the present invention.

  The moving mechanism 4 moves the probe 23 according to the control of the control unit 5 to bring the tip of the probe 23 into contact with the conductor pattern 102 on the electronic circuit board 100. The moving mechanism 4 moves the magnetic field sensor 31 on the electronic circuit board 100 according to the control of the control unit 5. The control unit 5 calculates the magnetic field strength (hereinafter, this magnetic field strength is also referred to as “detected magnetic field strength Md”) based on the extraction signal Se output from the magnetic field detection unit 3. In addition, the control unit 5 does not have a disconnection or a short circuit in the conductor pattern 102, and the magnetic field intensity generated by application of the inspection signal St (the conductor pattern 102 and the pad 112 of the integrated circuit 111 are well connected). Hereinafter, this magnetic field strength is also referred to as “reference magnetic field strength Ms”) and the calculated detected magnetic field strength Md to compare the quality of the conductor pattern 102 and the quality of the connection state between the conductor pattern 102 and the pad 112. Determination (determination of circuit board quality in the present invention) is performed. Further, the control unit 5 controls the movement of the probe 23 and the magnetic field sensor 31 by the moving mechanism 4. The operation unit 6 sets the frequency f1 and voltage of the AC signal Sa output from the AC signal output circuit 21 of the signal output unit 2 and the voltage setting and polarity (“+” of the DC signal Sd output from the DC signal output circuit 22. "-") And other operations are possible.

  Next, a circuit board inspection method for inspecting the quality of the connection state between the pads 112 of the integrated circuit 111 and the conductor pattern 102 in the electronic circuit board 100 using the inspection apparatus 1 will be described with reference to the drawings.

  First, the operation unit 6 is operated to set the voltage (crest value) of the AC signal Sa output from the AC signal output circuit 21 of the signal output unit 2 to 1.4 V as shown in FIG. Set f1 to 1 kHz. Further, for example, the voltage of the DC signal Sd output from the DC signal output circuit 22 of the signal output unit 2 is set to 0.8 V, and the polarity thereof is set to “+”. Next, the control unit 5 operates the signal output unit 2 according to these setting operations. At this time, the DC signal Sd output from the DC signal output circuit 22 is superimposed on the AC signal Sa output from the AC signal output circuit 21, and the test signal St shown in FIG. (Also referred to as “inspection signal St1”) is output from the signal output unit 2. In this case, since the + 0.8V DC signal Sd is superimposed on the AC signal Sa having a voltage of 1.4V, the test signal St1 varies within the range of + as shown in FIG. Signal (polarity + signal). Subsequently, the control unit 5 controls the moving mechanism 4 to move the probes 23a, 23b, and 23c, thereby moving the probes 23a, 102b, and 102c to the conductor patterns 102a, 102b, and 102c, as shown in FIG. The tip portions of 23b and 23c are brought into contact with each other. At this time, the inspection signal St <b> 1 output from the signal output unit 2 is applied to the conductor pattern 102 via the probe 23.

  Here, as shown in FIG. 2, for example, in the integrated circuit 111 of the electronic circuit board 100, the connection between the pad 112a and the conductor pattern 102c among the pads 112, 112... Is poor (both are not connected). Sometimes, as shown in FIG. 4, the test signal St1 does not flow to the element 111a in the integrated circuit 111 connected to the pad 112a. Further, as shown in FIG. 2, the pad 112b of the pads 112, 112... Is connected to the conductor pattern 102c in a good state, and the integrated circuit is connected to the pad 112b as shown in FIG. When a protection diode or a parasitic diode exists in the element 111b in the circuit 111, the inspection signal St1 applied through the probe 23c does not flow through the conductor pattern 102a, but flows through the element 111b and the conductor pattern 102b. Become. Further, since the inspection signal St1 has a positive polarity, the inspection signal St1 does not flow from the probe 23a to the conductor pattern 102a. Therefore, in this state, as shown in the figure, the inspection signal St1 flows only through the route R1 indicated by the alternate long and short dash line.

  Next, the control unit 5 controls the moving mechanism 4 to move the magnetic field sensor 31 of the magnetic field detection unit 3 along the upper surface of the integrated circuit 111 in the electronic circuit board 100. At this time, as shown in FIG. 2, when the magnetic field sensor 31 is positioned in the vicinity of the pad 112b in the integrated circuit 111, the magnetic field sensor 31 detects the magnetic field M1 generated in the conductor patterns 102b and 102c and detects the detection signal Ss. The filter 32 inputs the detection signal Ss and outputs the extraction signal Se. Subsequently, the control unit 5 calculates the detected magnetic field strength Md based on the extraction signal Se output from the magnetic field detection unit 3, and compares the reference magnetic field strength Ms in the vicinity of the pad 112b with the detected magnetic field strength Md. At this time, when the reference magnetic field strength Ms and the detected magnetic field strength Md are the same (or substantially the same) value, that is, when the difference between the two magnetic field strengths Md and Ms is within a predetermined allowable range, the control unit 5 It is determined that the pad 112b and the conductor pattern 102c are connected in a good state. In this case, as described above, the filter 32 outputs the extraction signal Se including only the narrow-band frequency component centered on the frequency f1 of the inspection signal St1 from the detection signal Ss. For this reason, a magnetic field having a frequency different from the frequency f1 generated in the conductor pattern 102 due to a high frequency generated in the power source of the moving mechanism 4 or a low frequency generated around the inspection apparatus 1 (hereinafter, this magnetic field is referred to as “ The influence of “disturbance” is sufficiently reduced. Therefore, the above determination by the control unit 5 is accurately performed as much as the influence of the disturbance is reduced.

  Next, as shown in FIG. 2, when the magnetic field sensor 31 is positioned in the vicinity of the pad 112a in the integrated circuit 111, the magnetic field sensor 31 detects the magnetic field M2 generated in the conductor patterns 102b and 102c and outputs the detection signal Ss. Then, the filter 32 outputs the extraction signal Se. Subsequently, the control unit 5 calculates the detected magnetic field strength Md based on the extraction signal Se, and compares the reference magnetic field strength Ms in the vicinity of the pad 112a with the detected magnetic field strength Md. In this case, as shown in the figure, when the pad 112a and the conductor pattern 102c are in a non-connected state, the conductor pattern does not flow to the element 111a in the integrated circuit 111 connected to the pad 112a. Since the inspection signals St1 flowing through the lines 102b and 102c are also small, the detected magnetic field strength Md is smaller than the reference magnetic field strength Ms. At this time, the control unit 5 determines that the connection state between the pad 112a and the conductor pattern 102c is defective because the difference between the two magnetic field strengths Md and Ms exceeds a predetermined allowable range. Here, as described above, the inspection signal St1 is a positive polarity signal by superimposing the DC signal Sd on the AC signal Sa. For this reason, as a result of the inspection signal St1 not flowing through the conductor pattern 102a, a magnetic field due to the inspection signal St1 is not generated from the conductor pattern 102a. Accordingly, the difference between the detected magnetic field strength Md and the reference magnetic field strength Ms appears clearly in the vicinity of the pad 112a because there is no influence of the magnetic field from the conductor pattern 102a. Based on the above determination is made accurately.

  Next, whenever the magnetic field sensor 31 is positioned in the vicinity of each pad 112 in the integrated circuit 111, the control unit 5 performs the same determination as described above. When the above determination is completed for all the pads 112 of the integrated circuit 111, the control unit 5 displays the determination result for each pad 112 on a display unit (not shown). In this case, the control unit 5 displays a determination result indicating that the electronic circuit board 100 is good when all the pads 112 are well connected, and indicates that the electronic circuit board 100 is defective when there is a defective connection. The determination result is displayed, and this circuit board inspection is completed.

  Next, a circuit board inspection method for inspecting the electronic circuit board 200 shown in FIG. 5 using the inspection apparatus 1 will be described with reference to the drawings. In this case, the electronic circuit board 200 includes a circuit board 201 and an integrated circuit 211 as an example of an electronic component mounted on the circuit board 201, as shown in FIG. The circuit board 201 is a board having a three-layer structure including a ground layer 201a, a power supply layer 201b, and a signal layer 201c. Each of the layers 201a, 201b, and 201c includes a conductor pattern 202a as a ground wiring and a conductor as a power supply wiring. A pattern 202b and a conductor pattern 202c as a signal wiring (hereinafter also referred to as “conductor pattern 202” when the conductor patterns 202a, 202b, and 202c are not distinguished) are formed. In the integrated circuit 211, a plurality of pads 212, 212... Arranged on the back surface (the lower surface in the figure) are connected to the conductor pattern 202 of the circuit board 201.

  When inspecting the electronic circuit board 200, the operation unit 6 is operated to set the voltage (crest value) of the AC signal Sa output from the AC signal output circuit 21 to 1.4 V as shown in FIG. In addition, the frequency f1 is set to 1 KHz. Further, as shown in the figure, the voltage of the DC signal Sd output from the DC signal output circuit 22 is set to 0.8 V and the polarity is switched to “−”. Next, when the control unit 5 operates the signal output unit 2 in accordance with these setting operations, the DC signal Sd is superimposed on the AC signal Sa, and an inspection signal St (hereinafter, this inspection signal St shown in FIG. (Also referred to as “inspection signal St2”) is output from the signal output unit 2. In this case, since the -0.8V DC signal Sd is superimposed on the AC signal Sa having a voltage of 1.4V, the test signal St2 has a voltage in the range of-as shown in FIG. It is a fluctuating signal (a signal with a negative polarity). Subsequently, the control unit 5 controls the moving mechanism 4 to bring the tips of the probes 23a, 23b, and 23c into contact with the conductor patterns 202a, 202b, and 202c of the electronic circuit board 200, respectively, as shown in FIG. At this time, the inspection signal St <b> 2 output from the signal output unit 2 is applied to the conductor pattern 202 via the probe 23.

  Here, in this electronic circuit board 200, as shown in FIG. 5, for example, the connection between the pad 212a and the conductor pattern 202c in the integrated circuit 211 is poor, and the pads 212b and 212c are good for the conductor patterns 202c and 202a, respectively. As shown in FIG. 7, it is assumed that a protection diode and a parasitic diode exist in the element 211b in the integrated circuit 211 connected to the pads 212b and 212c. At this time, since the voltage of the test signal St2 is-, as shown in the figure, the test signal St2 applied from the probe 23a is a path of the conductor pattern 202a, the element 211b and the conductor pattern 202c, that is, the same figure. The inspection signal St2 flows only in the path R2 indicated by the alternate long and short dash line.

  Next, the control unit 5 controls the moving mechanism 4 to move the magnetic field sensor 31 of the magnetic field detection unit 3 along the upper surface of the integrated circuit 211 in the electronic circuit board 200. Subsequently, as shown in FIG. 5, when the magnetic field sensor 31 is positioned in the vicinity of the pad 212b in the integrated circuit 211, the magnetic field sensor 31 detects the magnetic field M3 generated in the conductor pattern 202c and outputs a detection signal Ss. The filter 32 outputs the extraction signal Se. Next, the control unit 5 calculates the detected magnetic field strength Md based on the extraction signal Se, and compares the reference magnetic field strength Ms in the vicinity of the pad 212b with the detected magnetic field strength Md. At this time, when the reference magnetic field strength Ms and the detected magnetic field strength Md are the same (or substantially the same) value, that is, when the difference between the two magnetic field strengths Md and Ms is within a predetermined allowable range, the control unit 5 It is determined that the pad 212b and the conductor pattern 202c are connected in a good state. In this case, as described above, only the narrow-band frequency component centered on the frequency f1 of the inspection signal St2 is included in the extraction signal Se, so that the influence of disturbances other than the magnetic field due to the inspection signal St2 is sufficient. As a result, the above determination by the control unit 5 is accurately performed.

  Subsequently, as shown in FIG. 5, when the magnetic field sensor 31 is positioned in the vicinity of the pad 212a in the integrated circuit 211, the magnetic field sensor 31 detects the magnetic field M4 generated in the conductor pattern 202c and outputs a detection signal Ss. The filter 32 outputs the extraction signal Se. Next, the control unit 5 calculates the detected magnetic field strength Md based on the extraction signal Se, and compares the reference magnetic field strength Ms in the vicinity of the pad 212a with the detected magnetic field strength Md. In this case, as shown in the figure, when the pad 212a and the conductor pattern 202c are in the non-connected state, the conductor pattern does not flow to the element 211a in the integrated circuit 211 connected to the pad 212a. Since the inspection signal St2 flowing through 202c decreases, the detected magnetic field strength Md becomes a value smaller than the reference magnetic field strength Ms. At this time, the control unit 5 determines that the connection state between the pad 212b and the conductor pattern 202c is defective because the difference between the two magnetic field strengths Md and Ms exceeds a predetermined allowable range. Here, as described above, since the inspection signal St2 is a negative polarity signal, the inspection signal St2 does not flow through the conductor pattern 202b. As a result, a magnetic field due to the inspection signal St2 is not generated from the conductor pattern 202b. . Accordingly, the difference between the detected magnetic field strength Md and the reference magnetic field strength Ms appears more clearly in the vicinity of the pad 212a because there is no influence of the magnetic field from the conductor pattern 202b. Based on the above determination is made accurately.

  Subsequently, whenever the magnetic field sensor 31 is positioned in the vicinity of each pad 212 in the integrated circuit 211, the control unit 5 performs the same determination as described above. When the above determination is completed for all the pads 212 of the integrated circuit 211, the control unit 5 displays the determination result for each pad 212 on the display unit outside the figure in the same manner as the above display, and performs circuit board inspection. finish.

  Thus, according to this inspection apparatus 1, the magnetic field detection unit 3 extracts a component having the same frequency as the frequency f1 of the inspection signal St from the detection signal Ss output by the magnetic field sensor 31 and outputs the extracted signal Se. 32, the high frequency from the power source of the moving mechanism 4 and the low frequency from the periphery of the inspection apparatus 1 cause the conductor pattern 102 (or the conductor pattern 202) of the electronic circuit board 100 (or the electronic circuit board 200). The influence of the magnetic field generated due to the flow can be sufficiently reduced. Therefore, the connection state between the pad 112 (or pad 212) of the integrated circuit 111 (or 211) and the conductor pattern 102 (or conductor pattern 202) by the control unit 5 is reduced by the amount of the influence of the magnetic field caused by these. Can be accurately determined.

  Also, according to the inspection apparatus 1, the signal output unit 2 generates and outputs a signal obtained by superimposing the direct current signal Sd on the alternating current signal Sa as the inspection signal St, whereby a plurality of conductors in the circuit board 101 having a multilayer structure are output. When the connection state between the pad 112 and the conductor pattern 102 is inspected at the place where the patterns 102 overlap, the inspection signal St does not flow through the predetermined conductor pattern 102 of the overlapping conductor patterns 102. Can be regulated. Therefore, since the generation of the magnetic field in the predetermined conductor pattern 102 can be suppressed, the detection magnetic field strength Md and the reference magnetic field strength can be reduced by the amount that the influence of the magnetic field from the conductor pattern 102 can be reduced in the vicinity of the pad 112 to be inspected. As a result of clarifying the difference from Ms, the quality of the connection state between the pad 112 and the conductor pattern 102 based on the difference between the two magnetic field strengths Md and Ms by the control unit 5 can be accurately inspected.

  In addition, according to the inspection apparatus 1, the signal output unit 2 is configured to be superposed on the AC signal Sa by switching the polarity of the DC signal Sd, so that each conductor pattern 102 on the circuit board 101 and each circuit pattern on the circuit board 201 are arranged. By switching (reversing) the polarity of the DC signal Sd according to the shape of the conductor pattern 202, the overlapping state, and the internal structure of the integrated circuits 111 and 211, the generation of a magnetic field that affects circuit board inspection is further reduced. be able to.

  In addition, this invention is not limited to said structure. For example, although an example in which the filter 32 is configured by a narrowband bandpass filter has been described above, a highpass filter, a lowpass filter, a lock-in amplifier, and the like may be used instead of the narrowband bandpass filter. In addition, a notch filter can be used when a disturbance frequency affecting the inspection can be specified. Further, a plurality of types of these can be used. In addition, the example in which the magnetic field sensor 31 as the magnetic field detection unit in the present invention is configured by the MR sensor has been described above. However, instead of the MR sensor, the magnetic field detection unit is configured using a SQUID (superconducting quantum interference device) or a Hall element. It can also be configured.

  Further, an example in which the inspection apparatus 1 is used to inspect the connection state between the conductor pattern 102 (or conductor pattern 102) and the integrated circuit 111 (or integrated circuit 211) in the electronic circuit board 100 (or electronic circuit board 200). As described above, the inspection apparatus 1 can also be used when inspecting the disconnection or short circuit of the conductor patterns 102 and 202. In this case, the disconnection or disconnection of the conductor patterns 102 and 202 can be performed in the same manner as the circuit board inspection described above. A short circuit can be accurately inspected. In addition, the inspection target of the inspection apparatus 1 is not limited to the electronic circuit boards 100 and 200, but may be a single-layer circuit board, a circuit board having a layer structure of two layers or four layers, and these circuit boards. An electronic circuit board (as an example, an electronic circuit board 300 shown in FIG. 8) on which various electronic components are mounted is included.

  In this case, for example, as shown in FIG. 8, the electronic circuit board 300 has an electronic circuit on a circuit board 301 having a single-layer structure on which conductor patterns 302 a and 302 b (hereinafter, also referred to as “conductor pattern 302” when not distinguished) are formed. Capacitors 311a to 311d (hereinafter also referred to as “capacitor 311” when not distinguished) are mounted and configured as an example of components. Here, the capacitor 311 is, for example, a polarized capacitor such as a chip tantalum capacitor used for power supply decoupling, and electrodes (connection portions) are connected to the conductor patterns 302 and 302 on the circuit board 301. When inspecting the connection state between the electrode of the capacitor 311 and the conductor pattern 302 on the electronic circuit board 300 by using the inspection apparatus 1, first, the two probes 23a and 23c are attached to the conductor patterns 302 and 302, respectively. The inspection signal St1 described above is applied in contact.

  Here, as shown in the figure, for example, when the connection between the electrode of the capacitor 311d and the conductor pattern 302a is poor, the inspection signal St1 flows only in the path R3 indicated by the one-dot chain line in the figure. Next, when the magnetic field sensor 31 is positioned in the vicinity of the electrode of the capacitor 311d, the control unit 5 calculates the detected magnetic field strength Md based on the extraction signal Se output from the filter 32, and in the vicinity of the electrode of the capacitor 311d. The reference magnetic field strength Ms is compared with the detected magnetic field strength Md. In this case, as shown in the figure, since the current value of the test signal St1 flowing through the conductor pattern 302a is small because the test signal St1 does not flow through the capacitor 311d, the detected magnetic field strength Md is smaller than the reference magnetic field strength Ms. Value. At this time, the control unit 5 determines that the connection state between the electrode of the capacitor 311d and the conductor pattern 302a is defective because the difference between the two magnetic field strengths Md and Ms exceeds a predetermined allowable range.

  In this case, the inspection apparatus 1 uses an inspection signal St1 in which the direct current signal Sd is superimposed on the alternating current signal Sa. For this reason, in a conventional inspection apparatus using an AC signal as an inspection signal, the connection between the electrode of the polarized capacitor 311 and the conductor pattern 302 is caused by the possibility of damage due to reverse withstand voltage due to reverse application of voltage. While it is difficult to inspect the circuit board with respect to the state pass / fail inspection, the inspection apparatus 1 can reliably inspect the capacitor 311 without damaging it. Further, according to the inspection apparatus 1, since the magnetic field detector 3 includes the filter 32, the electrodes of the capacitor 311 are formed in the same manner as the circuit board inspection for the electronic circuit boards 100 and 200 described above. And the conductive pattern 302 can be accurately inspected for quality.

1 is a block diagram illustrating a configuration of an inspection apparatus 1. FIG. It is explanatory drawing which shows the test | inspection state with respect to the electronic circuit board 100 by the test | inspection apparatus. It is a voltage waveform diagram of AC signal Sa, DC signal Sd, and inspection signal St1. It is explanatory drawing which shows the test | inspection state with respect to the electronic circuit board 100 by the test | inspection apparatus. It is explanatory drawing which shows the test | inspection state with respect to the electronic circuit board 200 by the test | inspection apparatus. FIG. 6 is a voltage waveform diagram of an AC signal Sa, a DC signal Sd, and an inspection signal St2. It is explanatory drawing which shows the test | inspection state with respect to the electronic circuit board 200 by the test | inspection apparatus. It is explanatory drawing which shows the test | inspection state with respect to the electronic circuit board 300 by the test | inspection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inspection apparatus 2 Signal output part 3 Magnetic field detection part 5 Control part 21 AC signal output circuit 22 DC signal output circuit 31 Magnetic field sensor 32 Filter 100,200,300 Electronic circuit board 101,201,301 Circuit board 102a-102c, 202a- 202c, 302a, 302b Conductor pattern 111, 211 Integrated circuit 311a-311d Capacitor M1-M4 Magnetic field Sa AC signal Sd DC signal Se Extraction signal Ss Detection signal St, St1, St2 Inspection signal

Claims (3)

  A signal output unit that outputs an inspection signal including an AC signal having a predetermined period, and a magnetic field generated by applying the inspection signal to the conductor pattern of the circuit board is detected as a detection signal and a component corresponding to the period A circuit board inspection apparatus comprising: a magnetic field detection unit that extracts from the detection signal and outputs the extraction signal, and determines pass / fail of the circuit board based on the extraction signal.   The circuit board inspection apparatus according to claim 1, wherein the signal output unit generates the inspection signal by superimposing a DC signal on the AC signal.   The circuit board inspection apparatus according to claim 2, wherein the signal output unit is configured to be able to be superimposed on the AC signal by switching the polarity of the DC signal.

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