JP2008203077A - Circuit inspection device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit inspection device and method capable of discovering a fine insulation failure more accurately even when an impurity exists. <P>SOLUTION: When a measured resistance value is higher than a reference value, control is performed so that a high voltage 3 having a polarity different from that of a high voltage 2 is output. After switching the polarity at a prescribed timing, a measuring part 13 measures a current flowing between probes 11. Then, a measured resistance value between circuits is compared with a reference value. When the measured resistance value is lower than the reference value, it is determined that an insulation failure is generated, and the results are recorded in a recording part 15. When the measured resistance value is higher than the reference value, it is determined that the interval between the circuits is nondefective, and an insulation inspection between the circuits is finished. An insulation failure can be discovered precisely without overlooking even a fine insulation failure, and without generating deterioration such as a damage by a fire of an insulation failure spot. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inspection apparatus and method for an electronic circuit, particularly a circuit to be inspected, for a printed wiring board, and more particularly to a printed wiring board inspection apparatus and method for detecting an insulation failure of a circuit in the printed wiring board.

  Generally, a printed wiring board has a plurality of circuits electrically connected using through holes or the like, and whether the circuit of the manufactured printed wiring board is correctly formed as designed, that is, the printed wiring board. It is necessary to electrically inspect whether the circuit is formed as designed without disconnecting the internal circuit and causing a continuity failure or short-circuiting with other circuits and causing an insulation failure.

  As an electrical inspection method for insulation inspection (short-circuit inspection), a voltage is applied between the circuits to be inspected, and the insulation resistance between the circuits is determined from the voltage at that time and the measured current. The insulation resistance is below the reference value. In such a case, there is known a method for determining that the portion is an insulation failure portion.

  In addition, when there is a minute insulation failure called micro short, in order not to burn out the defective portion, first, a low voltage is applied to inspect, and if the insulation resistance is below the reference value, If it is determined that there is an insulation resistance greater than or equal to a reference value, an inspection method in which a high voltage is applied only between these circuits for inspection is known from Patent Document 1 below.

JP-A-6-230058

  However, in the inspection method described in Patent Document 1, when the resistance value decreases due to the presence of a conductor and a short circuit is about to occur, an insulation failure can be found, but the short circuit is about to occur due to impurities. In some cases, the circuit may not be detected simply as a drop in voltage with respect to the DC voltage. For example, when an AC current is applied, the circuit may exhibit diode-like characteristics or capacitor-like characteristics. There is a problem that it is difficult to do.

  An object of the present invention is to provide a circuit inspection apparatus and an inspection method which can solve the above-described drawbacks and can detect fine insulation defects with higher accuracy even when impurities are present.

In order to achieve the above object, the present invention is configured as follows. According to one feature of the present invention, in a circuit inspection apparatus for inspecting a target circuit using a plurality of inspection voltages,
First application means for applying a first voltage to the circuit under test;
Second application means for applying a second voltage higher than the first voltage to the circuit to be inspected;
There is provided a circuit inspection apparatus comprising: a third application unit that applies a voltage having the same voltage as the second voltage and a different polarity.

  In a preferred embodiment, the circuit to be inspected is formed on a printed board.

According to another feature of the present invention, in a circuit inspection method for inspecting a target circuit using a plurality of inspection voltages,
Performing an inspection by applying a first voltage to the target circuit;
Performing a test by applying a second voltage higher than the first voltage to the target circuit;
There is provided a circuit inspection method including a step of applying a voltage having the same voltage as the second voltage and a different polarity to the target circuit, and further performing an inspection.

  In a typical embodiment, an inspection apparatus according to the present invention includes a plurality of probes that can contact a circuit of a printed wiring board and a DC voltage source with variable applied voltage.

  In the inspection, first, as a first step, a plurality of probes are brought into contact with each inspection point of the circuit, and an arbitrary first DC voltage is sequentially applied between the pair of probes to measure a current. Next, a second voltage higher than the voltage applied in the first stage is applied between the probes, and the current is measured. Subsequently, a voltage having the same voltage as the second voltage but having a different polarity is applied to the circuit.

  In the present invention, even when there is an insulation failure due to a semiconductor behavior due to impurities as well as an insulation failure due to a decrease in resistance value caused by a normal conductor, by adding both polarities, fine insulation can be made with higher accuracy. Can detect defects.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing the overall configuration of the printed wiring board inspection apparatus 10.

  The printed wiring board inspection apparatus 10 includes a probe 11, a movement mechanism unit 12, a measurement unit 13, a variable DC power supply 14, a recording unit 15, and a control unit 16. A probe 11 is attached to the moving mechanism part 12 via a probe support part 17, and the probe 11 is parallel to the printed wiring board 18 including the circuit to be inspected (XY direction) and perpendicularly (Z direction). It is movable. The measurement unit 13 is connected to the probe 11 and measures the resistance of the circuit in the printed wiring board by passing a current between the probes or applying a voltage. The variable DC power source can arbitrarily change the inspection voltage. The recording unit 15 temporarily records the calculation result of the measured value. The control unit 16 performs drive control of the moving mechanism 12, processing for determining whether the resistance value measured by the measurement unit 13 is defective, voltage control of the variable DC power source 14, and the like.

  On the other hand, as shown in FIG. 2, the printed wiring board 18 to be inspected has a large number of various forms of circuits 19 to 23 formed thereon. FIG. 3 shows a circuit having two desired manufacturing qualities, circuit 24 and circuit 25. On the other hand, in the circuit shown in FIG. 4, a conductor burr is generated in the conductor 26 of one circuit and reaches the vicinity of the other circuit 27. That is, it has a structure in which a short circuit may occur between circuits. In such a case, the tip of the burr of the circuit 26 and the circuit 27 are close to each other, and insulation failure is likely to occur. In this case, if an impurity having a semiconductor behavior instead of a conductor is interposed between the two, there is a possibility that an insulation failure cannot be identified by simply applying a DC voltage from one direction. That is, for example, when a short circuit is about to occur due to the presence of impurities that exhibit semiconductor behavior between the circuits, such a circuit may exhibit diode-like characteristics or capacitor-like characteristics. is there. In the inspection of this example, the inspection apparatus is configured to operate so that the state of insulation failure can be properly detected even for such a circuit state.

  Hereinafter, the insulation inspection processing operation by the printed wiring board inspection apparatus will be described with reference to FIG.

First, the printed wiring board 18 including the circuit to be inspected is fixed using a printed wiring board fixing tool (not shown). Next, the control unit 16 controls the moving mechanism unit 12 to control and move the probe 11 so that the probe 11 is positioned at a predetermined terminal to be inspected by the circuit and brought into contact with a pair of circuits that are insulated from each other. (Step 1). Subsequently, the control unit 16 performs control so as to output the first voltage, that is, the low voltage V1 (step 2). Subsequently, the measurement unit 13 measures the current flowing between the probes 11. When the measured current is _Io applied voltage and V is V, the resistance R between the circuits is measured as R = V / _Io .

  Subsequently, the measured resistance value between the circuits is compared with a reference value to determine whether there is an insulation failure (step 3). If the measured resistance value is lower than the reference value, it is determined that the insulation is defective, the insulation inspection is terminated between the circuits, the process returns to Step 1, and the probe 11 is moved again between other circuits. , Perform the same operation. When the resistance value measured in step 3 is higher than the reference value, control is performed so as to output a high voltage 2 (step 5). Subsequently, the measurement unit measures the current flowing between the probes 11. Subsequently, the measured resistance value between the circuits is compared with a reference value (step 6). If the measured resistance value is lower than the reference value, it is determined that there is an insulation failure due to a micro short (step 7). Then, the insulation inspection of the circuit is finished and the inspection target circuit is specified, and the result is recorded in the recording unit 15. Note that a micro short is a kind of insulation failure, and occurs when a circuit is short-circuited with a minute hook-shaped conductor, and generally has a high resistance value (several MΩ or more). Insulation failures are those with insufficient insulation between circuits, and are generally from short-circuited (resistance value = 0Ω) to tens of MΩ, but in the case of printed wiring boards for special applications Even 1 GΩ is treated as an insulation failure.

  On the other hand, when the measured resistance value is higher than the reference value, control is performed so as to output a high voltage 3 having a polarity different from that of the high voltage 2 (step 8). In this case, the circuit switching configuration can be, for example, a circuit configuration as shown in FIG. That is, the polarity switching circuit 30 includes a change-over switch 31 connected to the control unit 16 in order to switch the variable DC power source 14 applied to the inspection target circuit 18 on the printed wiring board. In order to switch the power supply, an ammeter 32 for measuring the current of the power supply circuit and an A / D converter 33 for converting the current value from the ammeter and inputting it to the control unit are provided.

  After switching the polarity at a predetermined timing, the measurement unit 13 measures the current flowing between the probes 11. Subsequently, the measured resistance value between the circuits is compared with a reference value (step 9). If the measured resistance value is lower than the reference value, it is determined that the insulation is defective (step 7), and the result is recorded in the recording unit 15. If the measured resistance value is higher than the reference value, the circuit is determined to be non-defective and the insulation test between the circuits is terminated. After the above procedure is completed, the probe is moved and the above procedure is performed between other circuits to determine whether or not the inspection of all the circuits to be inspected has been completed (step 10). The inspection operation is performed in the above procedure between all the predetermined inspection target circuits, and when it is determined as a non-defective product among all the target inspection circuits, the printed wiring board is determined as a non-defective product, but even at one place If there is a defective portion, it is determined that the product is defective and a circuit related to the defective portion is specified and recorded, and all the inspection operations are terminated.

  As described above, a general insulation test is performed by applying an arbitrary voltage. Also, if you do not want to burn fine insulation failure, first, apply a low voltage to inspect, and if the insulation resistance is below the reference value, determine that the part is an insulation failure location, When the insulation resistance is equal to or higher than the reference value, the inspection is performed by applying a high voltage only between these circuits.

  In the inspection according to the present invention, first, a low voltage is applied and the inspection is performed. When the insulation resistance is less than the reference value, it is determined that the portion is an insulation failure portion, and the insulation resistance is more than the reference value. In some cases, the inspection is performed by applying a high voltage only between these circuits, and further, the inspection is performed with the polarity changed at a high voltage. Therefore, the inspection takes time as compared with the conventional inspection method.

  As a result of the experiment, assuming that the inspection time when a general insulation inspection is performed is 100 (in the experiment, the inspection voltage is set to 30 V), first, a low voltage (30 V) is applied, and then the inspection is performed. The inspection time was 114 when the inspection was performed by applying a voltage (set to 250 V in the experiment). Further, the inspection time by the inspection method according to the present invention was 139 (in the experiment, the low voltage was set to 30V, the high voltage was set to 250V, and the voltage changed in polarity with the high voltage was set to -250V).

  As is apparent from the above results, the present invention increases the number of inspection steps compared to the conventional insulation inspection method compared to the conventional insulation inspection method, but the inspection time is not so long and cannot be detected by the conventional method. It is possible to accurately detect the insulation failure without overlooking the subtle insulation failure and without causing deterioration such as burnout in the insulation failure portion.

  The present invention can be used for inspection of a printed wiring board.

The block diagram which shows the structure of the printed wiring board inspection apparatus which concerns on embodiment. The figure which shows an example of the printed wiring board containing a test object circuit. The figure which shows the state in which two circuits have desired quality. The figure which shows two circuits which have a possibility of short-circuiting. The flowchart which shows the flow of the insulation test | inspection of the printed wiring board test | inspection apparatus concerning embodiment of this invention. Schematic explanatory drawing which shows an example of a polarity switching circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Circuit test | inspection apparatus 11 Probe 12 Movement mechanism part 13 Measurement part 14 Variable direct-current power supply 15 Recording part 16 Control part 17 Probe support part 18 Printed wiring board 19-27 containing a test object circuit 31 Test object circuit 31 Switch 32 Ammeter 33 A / D converter

Claims (4)

In a circuit inspection device that inspects a target circuit using a plurality of inspection voltages,
First application means for applying a first voltage to the circuit under test;
Second application means for applying a second voltage higher than the first voltage to the circuit to be inspected;
A circuit inspection apparatus comprising: third application means for applying a voltage having the same voltage as the second voltage but having a different polarity.   The circuit inspection apparatus according to claim 1, wherein the circuit to be inspected is formed on a printed board. In a circuit inspection method for inspecting a target circuit using a plurality of inspection voltages,
Performing an inspection by applying a first voltage to the target circuit;
Performing a test by applying a second voltage higher than the first voltage to the target circuit;
Applying a voltage having the same voltage as the second voltage and a different polarity to the target circuit, and further performing a test.   The circuit inspection method according to claim 3, wherein the circuit to be inspected is formed on a printed board.

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