JP2005300386A - Circuit board inspection device and inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board inspection device and a method capable of inspecting a circuit board at high speed by shortening the time required for inspection, concerning a device and a method for allowing a test current formed by superimposing a direct current on an alternating current to flow in order to inspect the circuit board having a plurality of circuits, and observing a secondary harmonic of the alternating current generated from a crack or a narrowed part caused by a temperature characteristic of heating and cooling of an inspection circuit by Joule heat, to thereby detect a potential defect. <P>SOLUTION: This circuit board inspection device includes the first direct-current power source 21a, the second direct-current power source 21b and an alternating-current power source 22, first probe group 23a, 24a and second probe group 23b, 24b pairing respectively in order to be connected to both ends of the inspection circuit, and a switch 40 for switching and connecting the alternating-current power source to the first probe group or the second probe group. Preheating and inspection are switched between the plurality of inspection circuits by the switch, and preheating is performed in parallel before inspection, to thereby shorten the whole inspection time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a circuit board inspection apparatus and inspection method, and more particularly, to detect a potential defect such as an abnormally thin portion (a narrowed portion or a crack) of a circuit to be inspected in a nondestructive manner. And a test current in which AC current is superimposed on the circuit to be inspected. At that time, the second harmonic of the test current resulting from the heating and cooling cycle due to Joule heat generated in an abnormally thin part of the circuit to be inspected. Circuit board inspection apparatus and inspection method for observing

  It is necessary to inspect whether a circuit board manufactured before shipment functions electrically correctly as designed in the circuit board. For this circuit inspection, it is possible to inspect whether the circuit to be inspected is exposed on the circuit board for the presence or absence of disconnection or short circuit by visual observation or an enlarged image. However, at locations where the circuit under test is wired in the circuit board and not exposed, a non-destructive inspection such as continuity inspection (disconnection inspection) or insulation inspection (short circuit inspection) is performed by passing a test current through the circuit under inspection. There is a need to.

  However, in the continuity test performed by passing a test current, even if there is an abnormally thin portion (stenosis or crack) in the circuit under test, it cannot be detected if the abnormally thin portion or the like conducts electricity. Although such an abnormally thin portion of the circuit to be inspected cannot be detected as a disconnection defect in the continuity inspection before shipment, the narrowed portion is cut or the crack is enlarged as the circuit board is used by the user after shipment. This is a potential defect. Therefore, it is necessary to detect a potential defect such as an abnormally thin portion of the circuit to be inspected before shipment.

  Patent Document 1 describes an apparatus and method for nondestructively detecting such a potential defect in a circuit board. The principle of this detection apparatus and method is that a secondary current of a test current generated due to a temperature cycle of heating and cooling by Joule heat generated when a test current in which a direct current and an alternating current are superimposed is passed through a circuit to be inspected. A potential defect is detected by observing harmonics. That is, when a test current in which a direct current and an alternating current are superimposed is passed through the circuit to be inspected, and an abnormally thin portion exists in the circuit to be inspected, Joule heat is generated by the resistance at that portion. Since the circuit to be inspected is on or in an insulator having high thermal insulation, the temperature of an abnormally thin portion locally and cyclically changes in relation to the change of the alternating current. Since the resistance value is a function of temperature, the resistance value at that location changes as the temperature changes. According to the change in the resistance value, the current flowing through the abnormally thin portion changes. A current flowing through an abnormally narrow portion having a resistance value that changes in this way generates a voltage response including even-order harmonics of an alternating current. By observing the second harmonic of the alternating current, it is possible to detect an abnormally thin portion in the circuit to be inspected.

JP 58-191973

  However, since the inspection apparatus and the inspection method described in Patent Document 1 use the temperature characteristics of the circuit pattern to be inspected and the insulating substrate, the heating and cooling of the circuit pattern to be inspected constantly. It is necessary to wait for the preheating time to the cycle state and observe the second harmonic. As a result, when there are multiple circuit patterns to be inspected in the circuit board, the inspection time becomes longer to inspect all of them. There are drawbacks.

  The present invention provides a circuit board inspection apparatus and inspection method capable of detecting a potential defect of a circuit in a circuit board with higher accuracy in addition to solving the above-described drawbacks and performing high-speed inspection. The purpose is that.

  In order to achieve the above object, the present invention provides a circuit board inspection apparatus and inspection method having the following configuration.

  In order to inspect a circuit board including a plurality of circuits, the present invention described in claim 1 applies a test current obtained by superimposing a direct current and an alternating current to a circuit to be inspected on the circuit board, thereby generating a Joule heat of the test current. An apparatus for observing a second harmonic of an alternating current generated from a crack or constriction of a circuit to be inspected by a temperature characteristic of heating and cooling of the circuit to be inspected by detecting a potential defect of the circuit to be inspected, First and second DC power sources for generating a DC current, an AC power source for generating an AC current of a predetermined frequency, and a first and a second that are paired to connect to both ends of the circuit to be inspected. A probe set, a switch for switching and connecting the AC power supply to the first probe set or the second probe set, and a frequency twice the frequency of the AC power supply included in the current extracted from the first or second probe set Have two A sensing circuit for observing harmonics and detecting potential defects in the circuit under test, wherein the switch provides direct current from either the first or second DC power source for preheating prior to inspection. Is passed through the circuit to be inspected via the first or second probe set, and a test current is generated by superimposing the DC current from either the first or second DC power supply and the AC current from the AC power supply during the inspection. The preheat and the inspection are switched between the circuit to be inspected connected to the first probe set and the circuit to be inspected connected to the second probe set. Provided is a circuit board inspection apparatus capable of

  In order to inspect a circuit board including a plurality of circuits, the present invention described in claim 2 applies a test current in which a direct current and an alternating current are superimposed to a circuit to be inspected on the circuit board, thereby generating a Joule heat of the test current. An apparatus for observing a second harmonic of an alternating current generated from a crack or constriction of a circuit to be inspected by a temperature characteristic of heating and cooling of the circuit to be inspected by detecting a potential defect of the circuit to be inspected, First and second DC power sources for generating a DC current, first and second AC power sources for generating AC currents of predetermined first and second frequencies that do not interfere with each other, and both ends of the circuit under test Generating a test current in which a pair of first and second probes paired for connection, a direct current from the first or second direct current power supply and an alternating current from the first or second alternating current power supply are superimposed; To the first or second probe set And a defect including a potential defect in the circuit to be inspected by observing a second harmonic having a frequency twice as high as the first frequency of the first AC power source included in the current extracted from the first probe set. And a second harmonic having a frequency twice as high as the second frequency of the second AC power source included in the current extracted from the second probe set and observing the potential in the circuit under test. A circuit board inspection apparatus capable of simultaneously inspecting two circuits to be inspected with a first and second probe set.

  The present invention described in claim 3 is a circuit width input means for inputting the size of a cross-sectional area of a circuit of a circuit to be inspected (hereinafter also referred to as “circuit pattern”), and a current value of a direct current or an alternating current. And a means for adjusting the magnitude so that the second harmonic observed in the detection circuit becomes larger based on the size of the cross-sectional area of the circuit to be inspected inputted by the circuit width input means. A circuit board inspection apparatus according to any one of the preceding claims is provided.

  According to the present invention, the circuit length input means for inputting the circuit length (ie, circuit pattern length) of the circuit to be inspected and the material type of the circuit board, and a predetermined frequency of the AC power supply Is adjusted so that the second-order harmonics observed in the detection circuit are increased based on the circuit length of the circuit under test input by the input means such as the circuit length and the type of material of the circuit board. And a circuit board inspection apparatus according to any one of the preceding claims.

  According to the fifth aspect of the present invention, in order to inspect a circuit board including a plurality of circuits, a test current in which a direct current and an alternating current are superimposed is passed through a circuit to be inspected on the circuit board, and the test current is generated by Joule heat. A method for detecting a potential defect of a circuit under test by observing a second harmonic of an alternating current generated from a crack or constriction of the circuit under test by the temperature characteristics of heating and cooling of the circuit under test, Generating a first and second direct current, generating an alternating current having a predetermined frequency, flowing one of the first and second direct currents through a circuit to be inspected before inspection, and preheating; Passing a test current in which either the first or second DC current and the AC current are superimposed on the circuit to be inspected after preheating; and twice a predetermined frequency included in the test current taken out from the circuit to be inspected Have frequency To provide a circuit board testing method comprising the steps of detecting a potential defect in the observation to the circuit under test second harmonic.

  According to the circuit board inspection apparatus of the present invention described in claim 1, by providing two DC power supplies and a switch for alternately switching the AC power supply to the first and second probe sets, preheating of the circuit to be inspected and Since the inspection can be switched, the time required for preheating and the time required for the inspection can be executed in parallel, and the inspection time of the circuit board having a plurality of circuits can be shortened.

  According to the circuit board inspection apparatus of the present invention described in claim 2, two AC power supplies having frequencies that do not interfere with the two DC power supplies, the first and second probe sets, the first and second detection circuits, With this, it is possible to inspect two circuits to be inspected simultaneously with the first and second probe sets, and to reduce the inspection time of a circuit board having a plurality of circuits.

  According to the circuit board inspection apparatus of the present invention described in claim 3, a normal circuit to be inspected is burned by a test current based on the size of the cross-sectional area of the circuit to be inspected. By adjusting the current value so as to increase the observed second harmonic while preventing the problem, it is possible to inspect the circuit board with high accuracy.

  According to the circuit board inspection apparatus of the present invention as set forth in claim 4, the circuit length of the circuit to be inspected and the material of the circuit board (glass epoxy, ceramic, etc. constituting the insulating portion of the circuit board) The circuit board can be inspected with high accuracy by adjusting the frequency so that the observed second-order harmonic becomes larger based on the type of

  According to the circuit board inspection method of the present invention as set forth in claim 5, after the circuit to be inspected is preheated with a direct current from either the first or second direct current power supply before the inspection, the alternating current from the alternating current power supply is supplied. Since the inspection is performed with the test current superimposed, the inspection time can be shortened.

  First, in order to detect a potential defect such as an abnormally thin portion (constriction or crack) of the conventional non-destructive circuit described in Patent Document 1, a direct current and an alternating current are superimposed. A circuit board inspection device for observing second harmonics of test current caused by heating and cooling cycles caused by Joule heat generated at abnormally thin locations in the circuit under test when a test current is passed through the circuit under test The principle of the inspection method will be briefly described.

FIG. 1 shows a potential defect that is an abnormally thin portion 11 modeled of a circuit 10 to be inspected included in a circuit of a circuit board. The abnormally thin portion 11 has a relatively high resistance value R, and when a test current (for example, shown in FIG. 7) in which a direct current and a sinusoidal alternating current having a frequency f ₀ are superimposed is passed through the circuit under test 10. As described above, the second harmonic voltage 2f ₀ GV is generated due to the heating characteristic and the cooling characteristic due to the Joule heat generated in the abnormally thin portion 11. It is shown in the lower left column on page 4 of Patent Document 1 that the magnitude of the second harmonic voltage 2f ₀ GV is approximately proportional to the cube of the resistance value R of the abnormally thin portion 11. For this reason, if the magnitude of the second harmonic voltage is measured and is equal to or greater than the threshold value, it is detected as a potential defect. Note that the circuit under test 10 also generates a second harmonic voltage 2f ₀ CV that is not caused by the abnormally thin portion 11 at the same time. Since the phase differs from the second harmonic voltage 2f ₀ GV by about 90 degrees, it can be removed by passing it through a phase detector.

FIG. 2 shows a block diagram of a main part of a conventional detection circuit 20 described in Patent Document 1 in order to detect a potential defect. The power source 1 has a DC power source 21 and a sine wave AC power source having a frequency f ₀ . The direct current from the direct current power source 21 is superimposed on a sine wave alternating current having a frequency f ₀ from the alternating current power source 22 to generate a test current (for example, shown in FIG. 7). And then flow to the circuit under test 10. The current from the circuit under test 10 taken out from the probe 23 is removed from the fundamental frequency f ₀ component by the f ₀ removal filter 25, and the current including the second harmonic component (2f ₀ GV + 2f ₀ CV) is a linear amplifier. After being amplified at 26, only the current containing the second harmonic component (2f ₀ GV + 2f ₀ CV) is taken out by the 2f ₀ band filter 27 and amplified by the amplifier 28.

On the other hand, the sine wave current having the frequency f ₀ generated by the AC power supply 22 is doubled by the frequency doubler 29 and only the 2f ₀ output of the second harmonic is taken out by the 2f ₀ band filter 30. In the detection circuit 20, the phase of the second harmonic voltage 2f ₀ GV generated due to the abnormally thin portion 11 of the circuit under test 10 is not caused by the abnormally thin portion 11 of the circuit under test 10 that is generated simultaneously. Using the fact that the phase of the second harmonic voltage 2f ₀ CV is shifted by 90 degrees, the second harmonic voltage 2f ₀ GV generated due to the abnormally thin portion 11 of the circuit under test 10 is discriminated. In order to maximize the discrimination, the phase of the second harmonic output is slightly shifted by the phase shifter 31.

Then, the phase detector 32 extracts only the second harmonic voltage 2f ₀ GV generated due to the abnormally thin portion 11 of the circuit under test 10. The extracted second harmonic voltage 2f ₀ GV passes through a logarithmic amplifier 33 and a threshold detector 34, and instructs the failure indicator 35 to detect an abnormally thin portion 11 which is a potential defect. used.

As described above, the second harmonic voltage 2f ₀ GV generated due to the abnormally thin portion 11 of the circuit under test 10 is due to the heating and cooling cycle by the Joule heat of the test current flowing through the abnormally thin portion 11. Therefore, the temperature characteristics of heating and cooling of the circuit pattern to be inspected and the insulating substrate are used. As a result, if the second harmonic is not observed after waiting for the preheating time for the circuit pattern to be inspected to reach a steady heating and cooling cycle state, the circuit pattern to be inspected 10 is generated due to an abnormally narrow portion 11. The second harmonic cannot be measured accurately. For this reason, it is necessary to preheat so as to reach a steady state before the test current is supplied to the circuit under test 10 for inspection. Therefore, in the conventional circuit board inspection apparatus and inspection method disclosed in Patent Document 1, there is a problem that the preheating time by the test current is required separately before inspecting the circuit to be inspected, and the inspection time is long. In particular, when the number of circuits to be inspected included in the circuit board increases, the inspection time becomes long. The present invention solves this problem by enabling preheating and inspection of the circuit to be inspected in parallel.

  FIG. 3 shows a circuit block diagram of a main part of a circuit board inspection apparatus according to a preferred embodiment of the present invention. In FIG. 3, the same parts as those in FIG.

  In the embodiment of FIG. 3, two circuits under test 10a and 10b are shown. However, in reality, two or more circuits to be inspected are included in a circuit board (not shown), and only two are shown for simplicity. The circuit board inspection apparatus according to this embodiment includes a power source 1c including two identical DC power sources 21a and 21b and one AC power source 22. Further, the circuit board inspection apparatus of this embodiment includes two pairs of probe sets 23a, 24a and 23b, 24b so that they can be simultaneously connected to both ends of the two circuits to be inspected 10a and 10b. Each DC power source 21a, 21b of the power source 1c is connected to each of two pairs of probe sets 23a, 24a and 23b, 24b.

  Each of the two pairs of probe sets 23 a and 24 a and 23 b and 24 b is connected to the AC power supply 22 via the switch 40. The switch 40 selectively connects the AC power supply 22 of the power supply 1c to any one of the two pairs of probe sets 23a, 24a and 23b, 24b. The circuit board inspection apparatus according to the present embodiment includes any of the two pairs of probe sets 23a, 24a and 23b, 24b that include the same detection circuit 20 as in FIG. 2 and are selectively connected to the AC power supply 22 via the switch 40. Or connected to one set. The circuit board inspection apparatus according to the present embodiment further includes a control device 41. The control device 41 switches the switch 40 to connect the AC power source 22 and the detection circuit 20 to one of the two probe sets 23a, 24a and 23b, 24b, and the two probe sets 23a, 24a and 23b, Only the DC power supplies 21a and 21b are connected to either one of 24b.

  In the present embodiment, the switch 40 controlled by the control circuit 41 supplies a DC current for preheating the probe sets 23b and 24b to which only the DC power supply 21b is connected to the circuit under test 10b before the inspection. Further, the switch 40 controlled by the control circuit 41 connects the DC power source 21a and the AC power source 22 to the probe sets 23a and 24a, and inspects a test current 10a for inspecting a test current in which a DC current and an AC current are superimposed. Shed. As described above with reference to FIG. 2, the detection circuit 20 observes the second harmonic from the circuit under test 10a to which the test current is passed, and detects whether or not an abnormally thin portion 11 that is a potential defect exists. .

  When the observation of the circuit under test 10a by the detection circuit 20 is completed, the control circuit 41 switches the switch 40 for the next inspection, connects the AC power source 22 to the probe sets 23b and 24b, and has been preheated by the DC power source 21b. A test current in which a direct current and an alternating current are superimposed is passed through the circuit under test 10b. The detection circuit 20a can immediately observe the second harmonic from the preheated circuit to be inspected 10b to detect whether or not an abnormally thin portion 11 that is a potential defect exists.

  On the other hand, when the control circuit 41 finishes observing the circuit under test 10a by the detection circuit 20, the control circuit 41 moves the probe sets 23a and 24a from the circuit under test 10a that has been inspected, and the circuit under test (not shown) that receives the next inspection And is preheated by a direct current from a direct current power source 21a.

FIG. 8A shows a time chart of an inspection process by a circuit board inspection apparatus having a pair of conventional probes. As shown in FIG. 8A, a step 81 of moving the pair of probe sets 23 and 24 and connecting them to both ends of the circuit under test 10 and a step of preheating the circuit under test 10 using a direct current before the inspection. 82. A step 83 of inspecting a potential defect by supplying a test current in which a direct current and an alternating current are superimposed on the circuit to be inspected 10 is performed in a single line and in series. That is, the inspection process 83 can be performed only once in one cycle including the moving process 81 and the preheating process 82.
FIG. 8B shows a comparison of the inspection process by the circuit board inspection apparatus having two pairs of probe sets according to the embodiment of the present invention shown in FIG. As shown in FIG. 8B, two pairs of probe sets 23a, 23b, 24a, 24b are moved and connected to both ends of the circuits to be inspected 10a, 10b 81a, 81b. Steps 82a and 82b for preheating 10a and 10b with direct current, and steps 83a and 83b for inspecting for potential defects by supplying a test current superimposed with direct current and alternating current to the circuits under test 10a and 10b are the same steps. They are shifted from each other so as not to overlap in time, and are performed in a double track or in parallel. In the step shown in FIG. 8B, the switch 40 (FIG. 3) is switched at a time corresponding to the second dashed vertical line from the left in the figure, and the AC power source 22 (FIG. 3) is connected to the probe set 23b. The AC current is switched from 24b to the probe sets 23a and 24a, and the process immediately proceeds from the inspection process 83b of the circuit under test 10b to the inspection process 83a of the preheated circuit 10a. In this way, the movement process of the probe set, the preheating process of the circuit to be inspected, and the inspection process can be performed in parallel, and the detection circuit 20 can perform the other during the process of moving or preheating one probe set. Inspection of the circuit to be inspected can be executed by the probe set. As a result, inspection of a circuit board including a large number of circuits to be inspected can be executed at high speed.

  FIG. 4 shows a circuit block diagram of a main part of a circuit board inspection apparatus according to another embodiment of the present invention. 4, parts similar to those in FIG. 3 are denoted by the same reference numerals.

  In the embodiment shown in FIG. 4, two sets of power supplies 1a and 1b each provided with an AC power source that generates sinusoidal AC currents having different frequencies f1 and f2 and a DC power source that generates DC currents so as not to interfere with each other. Have The power sources 1a and 1b connect test currents generated by superimposing sine wave alternating currents having different frequencies f1 and f2 on direct currents to two pairs of probe sets 23a and 24a and 23b and 24b, respectively. The two pairs of probe sets 23a, 24a and 23b, 24b are connected to the circuits under test 10a, 10b, respectively, to pass a test current. Two detection circuits 20a and 20b similar to the detection circuit 20 in FIG. 2 are connected to the probes 23a and 24a, respectively, and the frequency f1 of the alternating current superimposed on the respective test currents from the circuits under test 10a and 10b. , F2 second harmonics are observed simultaneously and in parallel. Then, the detection circuits 20a and 20b determine whether or not the abnormally thin portion 11 is present as a potential defect included in the circuits to be inspected 10a and 10b based on the observed second harmonics of the frequencies f1 and f2. Is detected.

  The control circuit 42 simultaneously connects two pairs of probe sets 23a, 24a and 23b, 24b to the two circuits 10a, 10b, respectively, and is superimposed on the respective test currents by the two detection circuits 20a, 20b. Operation to observe the second harmonic of the frequency of the alternating current simultaneously and in parallel. Since the AC power supplies included in the respective power supplies 1a and 1b have different frequencies f1 and f2 so as not to interfere with each other, simultaneous and parallel inspection is possible with the two detection circuits 20a and 20b.

  Therefore, two inspected circuits can be inspected at the same time, and the circuit board inspection time can be reduced to about half compared to the conventional inspection apparatus of FIG. 2 using a pair of probes and a single power source. .

  FIG. 5 shows a flowchart of a main part of an inspection method of a circuit board inspection apparatus according to still another embodiment of the present invention. The circuit board inspection apparatus used in the inspection method of the present embodiment has a circuit cross-sectional area size of the circuit pattern of the circuit under test 10 on the circuit board and both ends of the circuit under test 10 in contact with the pair of probe sets. Input means (not shown) for inputting position information is provided. This input means can input circuit board manufacturing data (including the circuit width and circuit pattern thickness of the circuit pattern to be inspected from the design data) and digitized information of design information such as the positions of both ends. It may be a computer and storage means connected thereto. The cross-sectional area of the circuit may be obtained by a product operation of the circuit width obtained from the design data input for each circuit pattern (number) and the thickness of the circuit pattern (circuit pattern layer thickness). Further, the magnitude of the test current in which the direct current and the alternating current output from the power source 1 including the direct current power source 21 and the alternating current power source 22 are superimposed is determined by the cross sectional area of each circuit pattern to be inspected. Based on the size, set the value to maximize the second harmonic generated by potential defects such as abnormally thin parts in the circuit pattern to be inspected without burning out the normal circuit pattern to be inspected. Means such as a computer is provided.

  In the lower left column on page 4 of Patent Document 1, the magnitude of the second harmonic is proportional to the square of the magnitude of the alternating current, proportional to the square of the magnitude of the direct current, and the resistance value R of the abnormally thin portion is measured. It is disclosed that it is proportional to the cube. Therefore, when the magnitude of the test current is large, the magnitude of the second harmonic becomes large. On the other hand, the magnitude of Joule heat generated by the circuit pattern to be inspected when the test current flows increases in proportion to the square of the magnitude of the test current and the power of the entire resistance value of the circuit under test. In addition, if the test current is large and the cross-sectional area of the circuit pattern to be inspected is small, the circuit pattern to be inspected may be burned out. For this reason, based on the size of the circuit cross-sectional area of each circuit pattern to be inspected, the normal circuit pattern to be inspected may not be burned out and may be caused by a potential defect such as an abnormally thin portion in the circuit pattern to be inspected Set the test current value to the value that maximizes the generated second harmonic.

  In the inspection method according to the embodiment of the present invention shown in FIG. 5, after the start of inspection (step 50), the circuit width and circuit thickness of the circuit pattern to be inspected from manufacturing information, design information, etc. input to a computer (not shown). And the information such as the positions of both ends of the circuit in contact with the probe are read (step 51), and the circuit pattern to be inspected is divided into several groups depending on whether the cross-sectional area of the circuit is smaller or larger than the set values 1, 2, 3 Classify (step 52).

  In step 52, the minimum output current 1 is selected for the circuit under test 10 having the circuit cross-sectional area of the setting value 1 or less (step 53). An output current 2 greater than the output current 1 is selected for the circuit under test 10 having a circuit cross-sectional area greater than the set value 1 and less than or equal to the set value 2 (step 54). An output current 3 greater than the output current 2 is selected for the circuit under test 10 having a circuit cross-sectional area greater than the set value 2 and less than or equal to the set value 3 (step 55). In this way, the magnitude of the output current is selected based on the cross-sectional area of the circuit. Next, in order to apply a test current in which a direct current and an alternating current having a magnitude of the selected output current are superimposed from the power source 1 to both ends of the circuit under test 10 through a pair of probes, The probe set is moved (step 56). Then, a test current having the selected output current is passed between both ends of the circuit under test 10 to observe the second harmonic (step 57). As a result of observing the second harmonic, the circuit under test is observed. Data indicating the presence or absence of a potential defect 11 in 10 is stored (step 58). It is determined whether the inspection of all the circuit patterns to be inspected in the circuit board has been completed (step 59). If all the inspections have been completed, the inspection is completed. If not, the next circuit pattern to be inspected is inspected. Return to step 51.

  According to the method of the present embodiment, based on the size of the cross-sectional area of the circuit to be inspected, the magnitude of the test current in which the alternating current is superimposed on the direct current without burning the normal circuit to be inspected. The second harmonic generated by a potential defect such as an abnormally thin part is selected to be large. For this reason, the precision of detection of a potential defect can be improved.

  FIG. 6 shows a flowchart of a main part of an inspection method of a circuit board inspection apparatus according to still another embodiment of the present invention. The circuit board inspection apparatus used in the inspection method of the present embodiment includes the circuit length of the circuit pattern of the circuit 10 to be inspected on the circuit board, the type of material constituting the insulating portion of the circuit board, and a pair of probes. An input means (not shown) for inputting position information of both ends of the circuit 10 to be inspected that the set contacts is provided. This input means includes design information such as circuit board manufacturing data, design data, circuit length of the circuit pattern to be inspected, type of material constituting the insulating portion of the circuit board (for example, glass epoxy or ceramic), and both end positions. A computer capable of inputting the digitized information and a storage means connected thereto. Further, the frequency of the AC power source of the power source 1 that generates the test current in which the DC current and the AC current are superimposed, the size of the circuit length of each circuit pattern to be tested and the insulating portion of the circuit board are configured. Based on the type of material to be equipped, there is a computer or other means for setting the value to maximize the second harmonic generated by a potential defect such as an abnormally thin part in the circuit pattern to be inspected. ing.

  In the inspection method according to the embodiment of the present invention shown in FIG. 6, after the start of inspection (step 60), the circuit length of the circuit pattern to be inspected and the circuit from the manufacturing information and design information input to a computer (not shown) Information such as the type of material constituting the insulating portion of the substrate and the positions of both ends of the circuit in contact with the probe is read (step 61). The circuit pattern to be inspected is preset in advance with the optimum frequency frequency of the AC power source for potential defect detection based on the size of the circuit length and the type of insulating material of the circuit board. Depending on whether it is smaller or larger than the set values 1, 2, 3, it is classified into several groups (step 62).

  In step 62, the predetermined frequency 1 is selected for the circuit under test 10 having the circuit length and the substrate insulating material having the optimum frequency equal to or less than the set value 1 (step 63). The predetermined frequency 2 is selected for the circuit 10 to be inspected having the circuit length and the substrate insulating material having the optimum frequency larger than the set value 1 and less than or equal to the set value 2 (step 64). The predetermined frequency 3 is selected for the circuit 10 to be inspected having the circuit length and the substrate insulating material having the optimum frequency larger than the set value 2 and not more than the set value 3 (step 65). In this way, the frequency magnitude of the AC power source is selected that optimizes detection of potential results based on the circuit length magnitude and the substrate insulation material. Next, in order to apply a test current in which an alternating current having a selected frequency and a direct current are superimposed from the power source 1 to both ends of the circuit under test 10 through the pair of probes, the pair of probes is Move (step 66). Then, a test current in which an alternating current of the selected frequency is superimposed on the direct current is passed between both ends of the circuit 10 to be inspected, and a second harmonic of the selected frequency is observed (step 67). As a result of observing the harmonics, data indicating the presence or absence of a potential defect 11 in the circuit under test 10 is stored (step 68). It is determined whether the inspection of all the circuit patterns to be inspected in the circuit board has been completed (step 69). If all the inspections have been completed, the inspection is completed. If not, the next circuit pattern to be inspected is inspected. Return to step 61.

  According to the method of the present embodiment, based on the circuit length of the circuit to be inspected and the type of the substrate insulating material, the frequency of the alternating current superimposed on the direct current is set to a potential such as an abnormally thin portion. The second harmonic generated by a simple defect is selected to be large. For this reason, the precision of detection of a potential defect can be improved.

  The present invention can be used for inspection of circuit boards.

The figure which shows the potential defect of the abnormally thin part of the to-be-inspected circuit modeled. The circuit block diagram of the circuit board inspection apparatus which detects the potential defect by flowing the test current which superimposed the conventional direct current and the alternating current through the circuit to be inspected, and observing the second harmonic. 1 is a block diagram of a circuit board inspection apparatus according to one embodiment of the present invention. The block diagram of the circuit board inspection apparatus by another embodiment of this invention. The flowchart figure which shows the flow of operation of the circuit board inspection apparatus by another embodiment of this invention. The flowchart figure which shows the flow of operation of the circuit board inspection apparatus by another embodiment of this invention. The figure which shows the test electric current which superimposed the direct current and alternating current on the vertical axis | shaft, and took time on the horizontal axis. Comparison between the inspection process (A) by the conventional circuit board inspection apparatus having a pair of probe sets and the inspection process (B) by the circuit board inspection apparatus having two pairs of probe sets according to the embodiment of the present invention shown in FIG. FIG.

Explanation of symbols

1, 1a, 1b, 1c Power supply 10, 10a, 10b Circuit under test 11 Abnormally narrow part (potential defect)
20, 20a, 20b Detection circuit 21, 21a, 21b DC power supply 22 AC power supply 23, 24, 23a, 24a, 23b, 24b Probe set 40 Switch 41, 42 Control circuit

Claims (5)

In order to inspect a circuit board including a plurality of circuits, a test current in which a direct current and an alternating current are superimposed is applied to the circuit under test of the circuit board, and the temperature characteristics of heating and cooling of the circuit under test by Joule heat of the test current A device for observing a second harmonic of an alternating current generated from a crack or constriction of a circuit to be inspected to detect a potential defect of the circuit to be inspected,
First and second DC power supplies for generating a DC current;
An AC power source for generating an AC current of a predetermined frequency;
A pair of first and second probes each paired to connect to both ends of the circuit under test;
A switch for switching and connecting the AC power source to the first probe set or the second probe set;
Detection for detecting a potential defect in the circuit to be inspected by observing a second harmonic having a frequency twice the frequency of the AC power source included in the current extracted from the first or second probe set. A circuit,
The switch causes a DC current from either the first or second DC power supply to flow through the circuit to be inspected via the first or second probe set in order to preheat before the inspection, and the first current is supplied during the inspection. Alternatively, a test current in which a direct current from either one of the second direct current power supplies and an alternating current from the alternating current power supply are superimposed is generated and passed to the circuit under test via the first or second probe set, and the first A circuit board inspection apparatus capable of switching preheating and inspection between a circuit to be inspected connected to one probe set and a circuit to be inspected connected to the second probe set. In order to inspect a circuit board including a plurality of circuits, a test current in which a direct current and an alternating current are superimposed is passed through the circuit under test on the circuit board, and the temperature characteristics of heating and cooling of the circuit under test by Joule heat of the test current A device for observing a second harmonic of an alternating current generated from a crack or constriction of a circuit to be inspected to detect a potential defect of the circuit to be inspected,
First and second DC power supplies for generating a DC current;
First and second AC power sources for generating AC currents of predetermined first and second frequencies that do not interfere with each other;
A pair of first and second probes each paired to connect to both ends of the circuit under test;
Means for generating a test current in which a direct current from the first or second direct current power supply and an alternating current from the first or second alternating current power supply are superimposed and supplying the test current to the first or second probe set;
A potential defect in the circuit to be inspected is detected by observing a second harmonic having a frequency twice the first frequency of the first AC power source included in the current taken out from the first probe set. A first detection circuit;
A potential defect in the circuit to be inspected is detected by observing a second harmonic having a frequency twice the second frequency of the second AC power source contained in the current taken out from the second probe set. A second detection circuit;
A circuit board inspection apparatus capable of simultaneously inspecting two circuits to be inspected with the first and second probe sets. Circuit width input means for inputting the size of the cross-sectional area of the circuit of the circuit under test;
The magnitude of the current value of the direct current or alternating current is determined based on the size of the cross-sectional area of the circuit to be inspected inputted by the circuit width input means, and the second harmonic observed by the detection circuit. A means of adjusting the waves to be large,
The circuit board inspection apparatus according to claim 1, further comprising: An input means such as a circuit length for inputting the size of the circuit line length of the circuit to be inspected and the type of material of the circuit board;
The magnitude of the predetermined frequency of the AC power source is observed by the detection circuit based on the magnitude of the circuit length of the circuit to be inspected and the type of material of the circuit board inputted by the input means such as the circuit length. Means for adjusting the second harmonic to be increased,
The circuit board inspection apparatus according to claim 1, further comprising: In order to inspect a circuit board including a plurality of circuits, a test current in which a direct current and an alternating current are superimposed is passed through the circuit under test of the circuit board, and the temperature characteristics of heating and cooling of the circuit under test by Joule heat of the test current A method for observing a second harmonic of an alternating current generated from a crack or constriction of a circuit to be inspected and detecting a potential defect of the circuit to be inspected,
Generating first and second DC currents;
Generating an alternating current of a predetermined frequency;
Preheating by flowing either the first or second direct current through the circuit under test before testing;
Passing a test current in which either the first or second direct current and the alternating current are superimposed on a circuit to be inspected after preheating;
Observing a second harmonic having a frequency twice the predetermined frequency included in the test current taken from the circuit under test to detect a potential defect in the circuit under test;
A circuit board inspection method including:

Images