JP2010210510A - Insulation inspection apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize high-speed and accurate insulation inspection of a circuit board. <P>SOLUTION: An insulation inspection apparatus and an insulation inspection method for inspecting insulation of the circuit board having a plurality of wiring patterns. The insulation inspection apparatus includes a voltage source applying a voltage to the inspection object wiring patterns of the circuit board; an ammeter measuring a current value of the wiring patterns for every unit time, to which the voltage has been applied by the voltage source; and a control section identifying for every wiring pattern a measurement wait time satisfying a condition of I ≤ a threshold, based on the current value measured by the ammeter for every unit time. The insulation inspection method includes a function to process the control section. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an insulation inspection apparatus and an insulation inspection method for performing an insulation inspection of a circuit board having a plurality of wiring patterns.

  As an inspection method for confirming insulation between a plurality of electric wirings (wiring patterns) constituting a printed wiring board or the like, there is an insulation resistance inspection. In the insulation resistance test, for example, in order to accurately measure the super-insulating property of 10 GΩ level, a measurement waiting time is required to wait for the charge to be sufficiently charged after the measuring needle is brought into contact with the pattern under test. is there. And since this measurement waiting time is long, inspection time will become long.

  As an example of such an insulation inspection apparatus, there is an insulation inspection apparatus of Patent Document 1. In the insulation resistance inspection by this insulation inspection device, a relatively high voltage (for example, 200V) is applied between each wiring pattern to calculate a resistance value between the wiring patterns, and the quality of the insulation state is determined based on this resistance value. Was judged.

  Then, by determining whether the insulation state is good (whether sufficient insulation is ensured), it is determined whether the circuit board is a good product or a defective product.

Japanese Patent No. 3953087

  However, in the insulation resistance test of Patent Document 1, although improvement has been made with respect to the occurrence of sparks, the measurement standby time has not been improved, and an improvement in this respect is desired.

  In this case, if the measurement standby time is simply shortened in order to shorten the inspection time, the measurement is performed before the charge is sufficiently charged. As a result, there is a problem that a false report of the measurement as if the insulation property is poor occurs despite the fact that the printed circuit board has a sufficient insulation property.

  The present invention solves these problems of the prior art, and provides an insulation inspection apparatus and insulation inspection method that realizes high speed and accuracy of inspection for confirming super insulation of a circuit board having a plurality of wiring patterns. The purpose is to provide.

  The present invention has been made in view of the above-described problems, and an insulation inspection apparatus according to the present invention is an insulation inspection apparatus that performs an insulation inspection of a circuit board having a plurality of wiring patterns, and is a wiring to be inspected of the circuit board. Based on the voltage source that applies voltage to the pattern, the ammeter that measures the current value of the wiring pattern to which the voltage is applied by the voltage source per unit time, and the current value that is measured per unit time by the ammeter And a control unit that specifies a measurement standby time that satisfies the condition of I ≦ threshold for each wiring pattern. The insulation inspection method is provided with the processing function of the control unit.

  The measurement standby time can be shortened by specifying each wiring pattern, and inspection speed and accuracy can be realized.

It is a flowchart which shows the processing function of the control part of the insulation test | inspection apparatus which concerns on this invention. It is a functional block diagram which shows the structure of the control system of the insulation test | inspection apparatus which concerns on this invention. It is a graph which shows the conventional measurement timing with respect to the change of an electric current value. It is a graph which shows the measurement timing of this invention with respect to the change of an electric current value.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Since the overall configuration of the insulation inspection apparatus according to the present embodiment is substantially the same as that of the above-described insulation inspection apparatus of Patent Document 1, the description thereof will be omitted here, and the description will focus on the control system.

  As shown in FIG. 2, the control system 1 for the insulation inspection apparatus according to the present embodiment includes a control unit 2, a voltage source 3, an ammeter 4, and a determination unit 5.

  The control unit 2 is a device for controlling the voltage source 3 and the like, and stores processing functions shown in a flowchart described later. The voltage source 3 is a device for applying a voltage to the wiring pattern (pattern to be inspected 6) to be inspected on the circuit board. The ammeter 4 is a device for measuring the current value of the pattern capacitance 6 to be inspected.

  The determination unit 5 determines the quality of the circuit board based on the current value measured by the ammeter 4, and whether the slope of the transition amount of the current value is equal to or less than the threshold value based on a condition “I ≦ threshold value” described later. It is an apparatus for determining whether or not.

  Next, an insulation inspection method using this control system will be described. Here, the insulation inspection method according to the present embodiment and the conventional insulation inspection method will be described in comparison.

  When the measuring needle is brought into contact with the wiring pattern to be inspected, a transient current corresponding to the wiring capacity of the wiring pattern flows at the moment of contact. The time during which this transient current flows tends to increase in proportion to the size of the wiring capacitance of the wiring pattern. The time during which the transient current flows is about 10 to 100 ms, although it depends on the wiring pattern.

  In the conventional insulation inspection method, the electric current value is measured after the electric charge is sufficiently charged in the wiring capacitance of the wiring pattern. That is, the inspection apparatus measures the current value after the electric charge is sufficiently charged in the wiring capacitance of the wiring pattern after the transient current has converged, as in the conventional measurement timing of the graph of FIG. Calculate the value.

  At this time, the measurement standby time needs to be based on the measurement timing according to the maximum electric capacity possessed by the DUT (printed wiring board) for measuring the insulation resistance. For this reason, it is necessary to wait for the measurement standby time according to the maximum electric capacity even for a wiring pattern that essentially requires a shorter measurement standby time. That is, even if sufficient charging is completed at an early stage, there is a waiting time from the completion until the measurement waiting time elapses. As a result, it takes a long inspection time to measure the entire DUT. If the measurement standby time is shortened to the average value of the whole or the like, there are cases where the charge is not sufficient, and in that case, there is a risk of false information being generated in the measurement result.

  On the other hand, in the insulation inspection method of this embodiment, the optimum measurement standby time is specified by sampling the current value every set unit time. When a voltage is applied while the measuring needle is in contact with the wiring pattern, a transient current corresponding to the wiring capacity of the wiring pattern flows at the moment when the voltage is applied by contact, so that a very short period ( The current value sampling is repeated for the set unit time), and the slope of the transition amount of the current value is detected by differentiation. This sampling period (unit time) is shortened. In order to perform current measurement and calculation during one cycle, the change in the slope of the transition amount of the current value is accurately detected in real time in the shortest time within the limit.

  If a sufficient charge is charged in the wiring pattern, the transition amount of the current value becomes small. The amount of transition of the current value is converted into the slope of the graph by differentiation, and the value is compared with the threshold value to determine whether or not the threshold value is not exceeded, so that the wiring pattern is charged sufficiently. I know if it's not. Therefore, by differentiating the transient current transition at the time of insulation resistance measurement, the state where sufficient charge is charged is detected early, and the measurement is completed early, so that the shortest time is achieved according to the charge completion time. To complete the measurement.

  This will be described based on the graph of FIG. Sampling is repeated in a short cycle immediately after the voltage is applied to the wiring pattern, and the slope of the transition amount of the current value is accurately detected in real time. That is, the transition of the current value is differentiated to determine the slope of the transition amount, the slope is compared with the threshold value, and the time point when the slope becomes equal to or less than the threshold value is detected as the charge completion time point. For this reason, the measurement of the current value is started with that time as the time when the measurement standby time has elapsed. The measurement standby time elapses for each wiring pattern, and the optimum measurement standby time corresponding to each wiring pattern is sequentially detected for each wiring pattern, and measurement is started based on the measurement standby time. As a result, it becomes possible to specify the optimum measurement standby time for the wiring pattern.

  This makes it possible to select a measurement standby time according to the capacitance of each wiring pattern, unlike the conventional measurement standby time regardless of the capacitance of the wiring pattern. Inspection time can be shortened.

Specifically, sampling is performed according to the following equation to detect the time when the measurement standby time has elapsed. That is, if the slope (differential value) of the transition amount of the current value is I,
I = [(Tx current value−Tx + 1 current value) / cycle]
Is used to detect the gradient of the transition amount of the current value. x is 1 to 4 in FIG.

Then
Based on I ≦ threshold, a time point at which the slope of the transition amount of the current value becomes equal to or less than the threshold value is detected as a measurement standby time elapsed time point.

  Here, the threshold value is set to the following value. The threshold value ranges from a tilt of 0 (horizontal state) to a state tilted several degrees. It is desirable that the threshold value be tilted several degrees. This is because the current value measurement start time is shortened. The curve in the graph of FIG. 4 varies depending on various conditions such as the material of the insulating substrate. In the case of a steep curve, the current value may stabilize at the start of measurement even if the inclination angle is large to some extent. In the case of a gentle curve, the current value may not be stable at the start of measurement even if the tilt angle is somewhat small. For this reason, experimentally, it was determined whether the current value can be measured in a stable state when measured at how many inclinations according to various conditions such as insulating substrates using various materials, wiring patterns, etc. Let the slope be a threshold.

  Hereinafter, specific control in the control unit 2 will be described based on the flowchart of FIG. The inspection apparatus uses the same apparatus as the conventional inspection apparatus, and a description thereof is omitted.

  First, the probe is moved onto the installed circuit board to be inspected (step S1). Next, the probe is brought into contact with the circuit board wiring pattern (step S2), and it is confirmed whether or not the probe is in contact (step S3). If not, the contact operation (step S2) is repeated to bring the probe into contact with the wiring pattern.

  When the probe contacts the wiring pattern, a voltage is applied (step S4), and then the current value is measured (step S5).

  Next, it is determined whether or not the above-mentioned condition of “I ≦ threshold” is satisfied (step S6). If not satisfied, 1 is added to x in the above formula and the next sampling period is started (step S7), and again. The current value is measured (step S5). Next, it is determined again whether or not the condition “I ≦ threshold” is satisfied (step S6), and steps 5 to 7 are repeated until the condition “I ≦ threshold” is satisfied.

  The number of times to repeat Steps 5 to 7 varies depending on each wiring pattern. If the electric capacity of the wiring pattern is small, the number of times of repeating steps 5 to 7 is reduced. If the electric capacity of the wiring pattern is large, the number of times of repeating steps 5 to 7 increases. Thereby, the optimum measurement standby time is specified for each wiring pattern.

  Next, after the optimum measurement standby time has elapsed, the insulation resistance is measured (step S8), and the measurement result is recorded (step S9).

  This process is performed on all the wiring patterns to determine whether the circuit board is good or bad as a whole.

  As a result, the optimum measurement standby time is specified for each wiring pattern so that no waiting time is generated in all the wiring patterns, so that the measurement can be performed quickly and the insulation test can be speeded up. be able to. That is, the time-series current value transition is differentiated, and the optimum measurement timing is obtained from the value, thereby reducing the inspection time and speeding up the insulation inspection, and having a plurality of wiring patterns. The substrate can be inspected efficiently in a shorter time.

  In addition, since the optimum measurement standby time is specified for each wiring pattern, the current value is not measured before it is fully charged, and the accuracy of the insulation inspection can be realized.

  The present invention can be applied to all apparatuses for inspecting insulation between circuit wirings that are not electrically connected to each other. That is, the present invention can be applied not only to the above-described insulation inspection apparatus disclosed in Patent Document 1 but also to all apparatuses for performing an insulation inspection.

  In the embodiment, the optimum measurement standby time is specified using the slope of the transition amount of the current value. However, a difference value between the Tx current value and the Tx + 1 current value may be used. In this case, the time when the difference value becomes equal to or less than the set value is processed as the optimum measurement standby time for each wiring pattern.

  1: control system, 2: control unit, 3: voltage source, 4: ammeter, 5: determination unit, 6: pattern capacity to be inspected.

Claims (6)

An insulation inspection apparatus for performing an insulation inspection of a circuit board having a plurality of wiring patterns,
A voltage source for applying a voltage to the wiring pattern to be inspected on the circuit board;
An ammeter that measures the current value of the wiring pattern to which a voltage is applied by the voltage source every unit time; and
An insulation inspection apparatus comprising: a control unit that specifies, for each wiring pattern, a measurement standby time that satisfies a condition of I ≦ threshold based on a current value measured per unit time by the ammeter. The insulation inspection apparatus according to claim 1,
If the control unit does not satisfy the condition of I ≦ threshold for one of the current values measured per unit time by the ammeter, the condition of I ≦ threshold is satisfied for the current value of the next unit time. An insulation inspection apparatus characterized in that it is determined whether or not it is satisfied, and a time when the condition of I ≦ threshold is satisfied is set as a measurement standby time elapsed time. In the insulation inspection apparatus according to claim 1 or 2,
The above I ≦ threshold condition is I = [(Tx current value−Tx + 1 current value) / cycle]
Tx current value: current value in X unit time Tx + 1 current value: current value in X + 1 unit time An insulation inspection method for performing an insulation inspection of a circuit board having a plurality of wiring patterns,
Applying a voltage to the circuit pattern to be inspected on the circuit board with a voltage source;
With an ammeter, measuring the current value of the wiring pattern to which the voltage is applied every unit time; and
And a step of specifying, for each wiring pattern, a measurement standby time satisfying a condition of I ≦ threshold based on a current value measured every unit time in the control unit. In the insulation inspection method according to claim 4,
If one of the current values measured per unit time by the ammeter does not satisfy the condition of I ≦ threshold, it is determined whether or not the condition of I ≦ threshold is satisfied for the current value of the next unit time. Then, the time point when the condition of I ≦ threshold value is satisfied is set as the measurement standby time point. In the insulation inspection method according to claim 4 or 5,
The above I ≦ threshold condition is I = [(Tx current value−Tx + 1 current value) / cycle]
Tx current value: current value in X unit time Tx + 1 current value: current value in X + 1 unit time

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