Wiring inspection device, wiring inspection method, and wiring inspection program

Abstract

A wiring inspection device (100) comprises: a temperature acquisition unit (14) for acquiring, in relation to a printed circuit board (18) on which wiring (30) is formed, a temperature image extending along the longitudinal direction of wiring (30) that is between one part of the wiring (30) that is heated and another part of the wiring (30) that is cooled; and a calculation unit (10) for determining, on the basis of the value of the temperature gradient of the wiring (30) calculated from the temperature image, whether disconnection of the wiring (30) has occurred.

Description

Wiring inspection device, wiring inspection method, and wiring inspection program

[0001] The present disclosure relates to a wiring inspection device, a wiring inspection method, and a wiring inspection program.

[0002] In printed circuit boards, in which conductive wiring is printed on an insulating material, particularly flexible printed circuit boards, in which conductive wiring is printed on a flexible film-like insulator, it is necessary to inspect whether the wiring is printed without any breaks.

[0003] The presence or absence of a break in a wiring can be confirmed by checking the continuity of each wire with a tester, but with the recent remarkable miniaturization of wiring, the task of checking each wire with a tester is cumbersome and extremely difficult from a technical standpoint.Patent Document 1 discloses an invention of a non-destructive testing method that heats a joint of a flexible printed circuit board and measures the change in the surface temperature of the joint over time to test the electrical connection state of the joint.

[0004] Special Publication No. 2008-532009

[0005] However, the non-destructive testing method described in Patent Document 1 makes a judgment based on the time constant of the change in surface temperature over time, and therefore requires that the environmental conditions that affect the heat dissipation rate be made uniform, which poses a problem in that the test must be performed inside a test facility such as a thermostatic chamber where the spatial temperature is uniformly controlled.

[0006] An object of the present disclosure is to provide a wiring inspection device, a wiring inspection method, and a wiring inspection program that are capable of detecting the electrical connection state of wiring regardless of environmental conditions.

[0007] The wiring inspection device of the present disclosure includes a temperature acquisition unit that acquires a temperature image along the longitudinal direction of the wiring between a heated part of the wiring and another cooled part of the wiring on a printed circuit board on which wiring is formed, and a calculation unit that determines whether or not the wiring is broken based on the value of the temperature gradient of the wiring calculated from the temperature image.

[0008] The wiring inspection method disclosed herein is a wiring inspection method executed by a computer, and includes the steps of: calculating a value of the temperature gradient of a wiring formed on a printed circuit board from a temperature image along the longitudinal direction of the wiring between a heated part of the wiring and another cooled part of the wiring; and determining whether or not the wiring is broken based on the value of the temperature gradient of the wiring.

[0009] The wiring inspection program disclosed herein causes a computer to execute the following steps in a printed circuit board on which wiring is formed: calculating a value of the temperature gradient of the wiring from a temperature image along the longitudinal direction of the wiring between a heated part of the wiring and another cooled part of the wiring; and determining whether or not the wiring is broken based on the value of the temperature gradient of the wiring.

[0010] According to the present disclosure, it is possible to provide a wiring inspection device, a wiring inspection method, and a wiring inspection program that are capable of detecting the electrical connection state of wiring regardless of environmental conditions.

[0011] 1 is a schematic diagram showing an example of the configuration of a wiring inspection device according to a first embodiment; FIG. 2 is a block diagram showing an example of the hardware configuration of a calculation unit according to the first embodiment; FIG. 3 is a temperature image when no break occurs, and FIG. 4 is a temperature image when a break occurs; FIG. 4 is a graph showing the temperature distribution in the longitudinal direction of the wiring on the printed circuit board; FIG. 5 is a graph showing an example of the temperature gradient in the longitudinal direction of the wiring on the printed circuit board; and FIG. 6 is a graph showing the temperature distribution in a direction perpendicular to the longitudinal direction of the wiring on the printed circuit board. FIG. 5 is a schematic diagram showing an example of a temperature image when a break occurs in the wiring; and FIG. 6 is a schematic diagram showing an example of an image showing a wiring pattern obtained by image analysis of a visible image. FIG. 7 is a schematic diagram showing an example of the configuration of a wiring inspection device according to a second embodiment; and FIG. 8 is a flowchart showing an example of the processing of a wiring inspection method according to the first embodiment.

[0012] Hereinafter, a wiring inspection device according to an embodiment will be described with reference to the drawings. The following embodiments are merely examples, and the embodiments can be appropriately combined and modified.

[0013] 1 is a schematic diagram showing an example of the configuration of a wiring inspection device 100 according to a first embodiment. A printed circuit board 18 to be inspected has wiring 30 formed thereon. The wiring inspection device 100 includes a heating unit 12 that heats one end of a partial region of the wiring 30 on the printed circuit board 18, a cooling unit 16 that cools the other end of the wiring 30, which is connected to the partial region of the wiring 18 heated by the heating unit 12 and different from the partial region, a temperature acquisition unit 14 that acquires a temperature image along the longitudinal direction of the wiring 30 between the heated partial region and the cooled partial region, and a calculation unit 10 that determines whether or not the partial region has a break based on a temperature gradient calculated from the temperature image acquired by the temperature acquisition unit 14. Note that in this embodiment, the partial region of the wiring 18 heated by the heating unit 12 is described as one end of the wiring 18, and the other region of the wiring 18 cooled by the cooling unit 16 is described as the other end of the wiring 18. However, the partial region of the wiring 18 heated by the heating unit 12 does not have to be one end of the wiring 18. That is, the partial region of the wiring 18 heated by the heating unit 12 may be any part of the wiring 18. Furthermore, the other region of the wiring 18 cooled by the cooling unit 16 may be any other part of the wiring 18 that is different from the heated part of the wiring 18.

[0014] The heating unit 12 has a mechanism for heating a portion of the wiring 30 of the printed circuit board 18, and may be of a contact type or a non-contact type. A contact-type heating unit 12 can heat the printed circuit board 18 by contacting it with a heating wire, for example. A non-contact-type heating unit 12 can heat the printed circuit board 18 by bringing a lit incandescent light bulb into close proximity to the printed circuit board 18, for example. The heating unit 12 can also be configured to use heat generated by the device being inspected as the heating unit 12 and transfer it to the printed circuit board 18 for heating. Furthermore, the heating unit 12 can be configured to use heat generated by a portion of the power distribution equipment in which the printed circuit board 18 is used, through which a large current flows, for example. In this way, when heat generated by the device being inspected or heat generated by the equipment in which the printed circuit board 18 is used as the heating unit 12, there is no need to provide a separate heating unit 12, and thermal energy can be used efficiently. In addition, in such a case, the number of parts of the wiring inspection device 100 can be reduced, improving maintainability and reducing costs.

[0015] The cooling unit 16 has a mechanism for cooling a portion of the wiring 30 on the printed circuit board 18 that is different from the portion of the wiring 30 heated by the heating unit 12, and may be either a contact type or a non-contact type. Contact and non-contact cooling units 16 can, for example, provide forced cooling by placing a heat sink or a Peltier element in close proximity to or in contact with the printed circuit board 18. Non-contact cooling units 16 can also provide air cooling using a fan, for example. Furthermore, the cooling unit 16 may be naturally cooled by the difference in temperature with the ambient temperature without using a special mechanism. In this way, when no special mechanism is used as the cooling unit 16, thermal energy can be utilized efficiently. Furthermore, in such a case, the number of components in the wiring inspection device 100 can be reduced, improving maintainability and reducing costs.

[0016] The temperature acquisition unit 14 acquires a temperature image of the wiring area where wiring is formed on the printed circuit board 18, and may be of a contact type or a non-contact type. A known method can be used to acquire a contact type temperature image. An infrared thermograph or a thermopile can be used to acquire a non-contact type temperature image. Alternatively, a temperature image can be acquired as a camera image by applying paint or film that changes color in response to temperature.

[0017] The calculation unit 10 calculates a temperature gradient value from the acquired temperature image and determines whether or not there is a disconnection based on the temperature gradient value. The detailed operation will be described later. The result of the determination by the calculation unit 10 is notified to the facility manager via a display device or communication device (not shown).

[0018] 2 is a block diagram showing an example of a hardware configuration of the calculation unit 10 according to embodiment 1. As shown in Fig. 2, the calculation unit 10 is configured by a computer in which a CPU (Central Processing Unit) 21, which is a calculation element (processor), a main memory 22, an input / output interface (I / O interface) 23, and a memory unit 24 are each connected to a system bus 25. The calculation unit 10 may be configured by a plurality of computers connected via a network, or may be configured by a processing circuit.

[0019] The CPU 21 is an integrated circuit (IC) that performs arithmetic processing. In addition to the CPU 21, arithmetic elements such as a digital signal processor (DSP), a graphics processing unit (GPU), a network processor, or a field programmable gate array (FPGA) may be used. By executing the wiring inspection program according to the first embodiment, the CPU 21 realizes a wiring inspection method having a function of calculating a temperature gradient value from an acquired temperature image (step S1) and a function of determining the presence or absence of a disconnection based on the calculated temperature gradient value (step S2), as shown in FIG. 7 . As a result, the CPU functions as a temperature gradient calculation unit and a disconnection determination unit by executing the wiring inspection program. The wiring inspection program may be provided, for example, on a recording medium on which the program is recorded.

[0020] The main memory 22 is configured by a volatile storage device such as a RAM (Random Access Memory) or a non-volatile storage device such as a ROM (Read Only Memory). The storage unit 24 is configured by a non-volatile storage device such as a HDD (Hard Disk Drive) or a flash memory.

[0021] The I / O interface 23 is a port to which the heating unit 12, the temperature acquisition unit 14, etc. are connected.

[0022] Next, a method for determining whether or not the wiring 30 is broken based on the temperature gradient will be described with reference to FIGS.

[0023] FIG. 3 shows an example of a temperature image obtained when a printed circuit board 18 having wiring 30 (30A, 30B, 30C, 30D) is heated at one end 32 as a partial region and cooled at the other end 34 as a separate region, and reaches a steady state. In FIG. 3, the higher the dot density, the higher the temperature. FIG. 3A shows a temperature image obtained when no break occurs, showing a gradual temperature decrease from the one end 32, the heated partial region, to the other end 34, the cooled partial region. FIG. 3B shows a temperature image obtained when a break occurs. In the region between the heated partial region (one end 32) of wiring 30C and the broken region 38, the heat dissipation path connecting to the other region cooled by the cooling unit 16 is cut off, resulting in a high-temperature region 36 exhibiting a higher temperature than the surrounding area. The high-temperature region 36 exhibits a temperature gradient higher than the surrounding area.

[0024] For each temperature distribution described in FIG. 3 , the temperature distribution along the longitudinal direction of the wiring 30 of the printed circuit board 18 is shown in FIG. 4A , and an example of the temperature gradient is shown in FIG. 4B . The longitudinal direction of the wiring 30 refers to the direction along the longest length of the wiring 30 between the portion heated by the heating unit 12 and the other portion cooled by the cooling unit 16. When one end 32 of the wiring 30 is heated and the other end 34 is forcibly cooled, the temperatures of the ends 32 and 34 are uniform regardless of whether a break is present. Therefore, the temperature distribution along the longitudinal direction of the wiring 30 shown in FIG. 4A shows a temperature distribution 40 that continuously and monotonically decreases in the absence of a break, whereas when a break is present, it shows a temperature distribution 42 that abruptly changes in the break region. Furthermore, when the absolute value of the temperature gradient, i.e., the absolute value of the temperature change per unit length, is calculated, it is as shown in FIG. 4B , and the temperature gradient 44 (absolute value) in the absence of a break is uniform. On the other hand, if a wire breaks, the absolute value of the temperature gradient, as shown in temperature gradient 46 (absolute value), increases in the region where the wire breaks compared to the value when there is no localized break and decreases in regions other than the region where there is a break. That is, the calculation unit 10 calculates the maximum absolute value g1 of the temperature gradient during the inspection, compares it with a temperature gradient threshold tg1, which is a predetermined threshold for the absolute value of the temperature gradient, and determines that a wire break has occurred if g1 > tg1. The calculation unit 10 also calculates the kurtosis k1 of the absolute value of the temperature gradient using the following formula (1) as an index indicating the ratio between the absolute value of the temperature gradient in the region where the wire breaks and the absolute value of the temperature gradient in the region without the break. The calculation unit 10 compares this with a kurtosis threshold tk1, which is a predetermined kurtosis threshold, and determines that a wire break has occurred if k1 > tk1. The index is not limited to kurtosis, and any index indicating the sharpness of the frequency distribution may be used. For example, the calculation unit 10 may determine that a wire break has occurred if the ratio between the peak value and the median value of the absolute value of the temperature gradient exceeds a predetermined ratio threshold. The temperature gradient threshold value tg1, the kurtosis threshold value tk1, and the ratio threshold value are each specifically determined through experimental determination using a plurality of samples in which no break has occurred and a plurality of samples in which a break has occurred.

[0025] X: Each absolute value of the temperature gradient μ: Average value of X σ: Standard deviation of X

[0026] 4C is a graph showing a temperature distribution 48 at cross section A-A' in FIG. 3A, a temperature distribution 50 at cross section B-B' in FIG. 3B, and a temperature distribution 52 at cross section C-C'. When there is no break, the temperature distribution 48 at cross section A-A' is substantially constant, and the absolute value of the temperature gradient is very small. When there is a break, the temperature distribution 50 at cross section B-B' increases in absolute value because the temperature near the broken wiring 30C is higher than the surrounding area. Furthermore, when there is a break, the temperature distribution 52 at cross section C-C' increases in absolute value because the temperature near the broken wiring 30C is lower than the surrounding area.

[0027] Next, a method for calculating the temperature gradient value from a temperature image will be described. Fig. 5(A) is a schematic diagram showing an example of a temperature image (thermography) taken by an infrared thermo camera or the like when a break occurs in the wiring 30C, and Fig. 5(B) is a schematic diagram showing an example of an image showing a wiring pattern obtained by image analysis of a visible image (a camera image taken using visible light).

[0028] In the first embodiment, when calculating the temperature gradient value from the temperature image, the temperature image and information on the wiring pattern are integrated to calculate the temperature gradient value in the longitudinal direction along the wiring pattern. The temperature gradient value of the wiring pattern is calculated from the temperature image using the following method. In the first embodiment, a camera that captures visible images is further provided, and the temperature image and the visible image are superimposed using known technology. For example, the temperature acquisition unit 14 is a portable device that can simultaneously acquire the temperature image and the visible image.

[0029] In the first embodiment, the wiring position is obtained by image analysis of the captured visible image. There are various methods for image analysis to obtain the wiring position, but as an example, the Canny method is used to extract a line drawing from the visible image.

[0030] In the temperature image shown in Fig. 5(A), only the temperature distribution is obtained, and the wiring position is unknown. In the image analyzed visible image shown in Fig. 5(B), an image in which the wiring 30 is visible is obtained, but breaks in the wiring 30 are not visible. In the first embodiment, the wiring position is obtained by applying a known image processing technique such as the Canny algorithm, and the coordinates of the start point, route, and end point of one or more wirings 30 are calculated.

[0031] In the first embodiment, a temperature image and an image showing a wiring pattern obtained from a visible image are superimposed using a known technique, and the temperature values ​​of the wiring pattern are referenced for each distance from the starting point. In this way, the temperature gradient value can be calculated from the temperature image.

[0032] In the first embodiment, a GUI for specifying the wiring pattern to be inspected may be provided on the temperature image or the visible image. Specifically, the coordinates of the wiring pattern are specified by tracing the temperature image or the visible image displayed on the display unit connected to the calculation unit using a mouse or a touch panel connected to the calculation unit 10. Alternatively, the numerical coordinates of the wiring pattern are input via an input device such as a keyboard connected to the calculation unit 10. The coordinates of the wiring pattern are obtained, for example, from a design drawing.

[0033] Then, from the visible image or temperature image of the wiring 30, one end 32 and the other end 34 of the wiring 30 formed on the printed circuit board 18 on the image are calculated, and aligned with the wiring position on the design drawing, and the temperature values ​​of the wiring pattern on the design drawing are referenced for each distance from the starting point. In this way, the temperature gradient value can be calculated from the temperature image.

[0034] Furthermore, the temperature gradient value may be calculated by extracting temperature information of the wiring using a portable temperature sensor that can trace directly above the wiring pattern.

[0035] The calculation unit 10 can calculate the absolute value of the temperature gradient by performing a calculation to take the absolute value of each temperature gradient value calculated by the various means described above. Note that the calculation unit 10 does not necessarily need to calculate the absolute value of the temperature gradient, and may determine the presence or absence of a wire break based on the temperature gradient value calculated by the means described above. When determining the presence or absence of a wire break based on the temperature gradient value, instead of the absolute value of the temperature gradient described above, the value of the temperature gradient before the calculation of the absolute value may be used, and a threshold value corresponding to the temperature gradient value may be used.

[0036] As described above, according to the first embodiment, the presence or absence of a wire break is detected based on the temperature gradient value, so that the presence or absence of a wire break can be determined even in an environment where the ambient temperature is not controlled. As a result, it is possible to perform wiring inspection without having to match various conditions, such as heating performance, cooling performance, and space temperature, with predetermined test conditions. In particular, when determining the presence or absence of a wire break based on the kurtosis of the temperature gradient, the value of the kurtosis of the temperature gradient does not depend on the temperature difference between the heated and cooled regions, so a uniform threshold can be set regardless of the performance of the heating unit 12 and the cooling unit 16. This has the effect of enabling determination with fewer conditions set than in the past.

[0037] The presence or absence of a wire break can also be determined using the value of the temperature gradient in the direction perpendicular to the longitudinal direction. Specifically, as shown in FIG. 4C, when there is no wire break, the temperature distribution 48 at cross section A-A' is approximately constant, and the absolute value of the temperature gradient is very small. When there is a wire break, the temperature distribution 50 at cross section B-B' increases in absolute value because the temperature near the wire 30C with the break is higher than the surrounding area. Furthermore, when there is a wire break, the temperature distribution 52 at cross section C-C' increases in absolute value because the temperature near the wire 30C with the break is lower than the surrounding area. Based on this change in temperature gradient, it is possible to determine the presence or absence of a wire break in the wire 30.

[0038] Next, a second embodiment will be described. Fig. 6 is a schematic diagram showing an example of the configuration of a wiring inspection device 200 according to the second embodiment. The wiring inspection device 200 according to the second embodiment differs from the first embodiment in that it is newly equipped with an external storage unit 20. However, the other configuration is the same as that of the first embodiment, and therefore the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.

[0039] The external storage unit 20 is controlled by the calculation unit 10 to measure and store in advance the value of the temperature gradient in a state without any disconnections, provided that it is guaranteed that there will be no disconnections immediately after the printed circuit board 18 is installed. The external storage unit 20 is configured with a non-volatile storage device such as a flash memory. In the second embodiment, after the printed circuit board 18 is installed, the calculation unit 10 measures the value of the temperature gradient of the printed circuit board 18 through an optional interface (not shown) that starts an operation to store the temperature gradient value, and stores the value in the external storage unit 20. The optional interface is, for example, a portable device capable of simultaneously acquiring temperature images and visible images, as described in the first embodiment.

[0040] During the inspection, the temperature gradient value measured in the same manner as in the first embodiment is compared with the temperature gradient value stored in the external storage unit 20, and if the difference is equal to or greater than a predetermined allowable threshold, it is determined that a disconnection has occurred. The allowable threshold is specifically determined, for example, through experimental determination using a plurality of samples without a disconnection and a plurality of samples with a disconnection.

[0041] In the second embodiment, the measured temperature gradient value is compared with the temperature gradient value stored in the external memory unit 20, and if the difference is equal to or greater than the allowable threshold, it is determined that a break has occurred. Since the absence of a break is the basis for determination, it has the effect of being able to determine whether or not a break has occurred regardless of the design information of the printed circuit board 18, such as the length and width of the wiring 30.

[0042] Alternatively, information on the wiring pattern indicating the position and shape of the wiring 30 formed on the printed circuit board 18 may be separately acquired, and the wiring pattern information and the temperature image may be integrated to calculate the longitudinal wiring pattern. The wiring pattern information may be obtained, for example, by acquiring and analyzing a visible image of the printed circuit board 18, as in the first embodiment, or by inputting design information for the printed circuit board 18. In this way, it is possible to check whether the area where the temperature gradient occurs coincides with the area where the wiring 30 is provided, thereby improving the accuracy of the inspection.

[0043] In the second embodiment, the temperature gradient value may be calculated as an absolute value of the temperature gradient, as in the first embodiment. In such a case, the wiring inspection device 200 measures in advance the absolute value of the temperature gradient in a state where there is no break and stores it in the external storage unit 20. The calculation unit 10 compares the absolute value of the temperature gradient measured in the same manner as in the first embodiment with the absolute value of the temperature gradient stored in the external storage unit 20, and determines that a break has occurred if the difference is equal to or greater than a predetermined allowable threshold. In this way, even when the absolute value of the temperature gradient is used, the same effects as in the second embodiment described above can be achieved.

[0044] Next, a third embodiment will be described. The third embodiment differs from the first and second embodiments in that the temperature gradient values ​​of adjacent wirings 30 on the printed circuit board 18 are compared, and a disconnection is determined when the difference between the temperature gradient values ​​is equal to or greater than a predetermined threshold (temperature gradient difference threshold). However, the other configurations are the same as those of the first and second embodiments, and therefore the same components as those of the first and second embodiments are denoted by the same reference numerals as those of the first and second embodiments, and detailed description thereof will be omitted.

[0045] In the third embodiment, the value of the temperature gradient in the longitudinal direction of each wiring 30 is measured as in the first embodiment. Then, for each of adjacent wirings 30, the value of the temperature gradient in the direction perpendicular to the longitudinal direction is compared, and if the difference between the compared temperature gradient values ​​is equal to or greater than the temperature gradient difference threshold, it is determined that a disconnection has occurred.

[0046] The temperature gradient difference threshold is specifically determined, for example, through experimental determination using multiple samples without a disconnection and multiple samples with a disconnection. However, the temperature gradient difference threshold, temperature gradient threshold tg1, kurtosis threshold tk1, ratio threshold, and tolerance threshold in embodiment 2 may each be adjusted based on the thermal conductivity of the wiring 30 estimated from the temperature image. Specifically, if the thermal conductivity of the wiring 30 estimated from the temperature image is higher than the thermal conductivity estimated from the material constituting the wiring 30 and the thickness of the wiring 30, the temperature gradient difference threshold, temperature gradient threshold tg1, kurtosis threshold tk1, ratio threshold, and tolerance threshold in embodiment 2 are adjusted higher. Furthermore, if the thermal conductivity of the wiring 30 estimated from the temperature image is lower than the thermal conductivity estimated from the material constituting the wiring 30 and the thickness of the wiring 30, the temperature gradient difference threshold, temperature gradient threshold tg1, kurtosis threshold tk1, ratio threshold, and tolerance threshold in embodiment 2 are adjusted lower.

[0047] In the third embodiment, a disconnection can be determined when the difference between the temperature gradient values ​​in the direction perpendicular to the longitudinal direction of adjacent wirings 30 on the printed circuit board 18 is equal to or greater than the temperature gradient difference threshold. Furthermore, in the third embodiment, it is possible to optimize the temperature gradient difference threshold, the temperature gradient threshold tg1, the kurtosis threshold tk1, the ratio threshold, and the tolerance threshold based on the thermal conductivity of each of the wirings 30.

[0048] In the third embodiment, the temperature gradient value may be calculated as an absolute value of the temperature gradient, as in the first and second embodiments. In such a case, even if the absolute value is used as the temperature gradient value, the same effect as in the third embodiment can be achieved.

[0049] REFERENCE SIGNS LIST 10 Calculation unit, 12 Heating unit, 14 Temperature acquisition unit, 16 Cooling unit, 18 Printed circuit board, 20 External memory unit, 21 CPU, 22 Main memory, 23 I / O interface, 24 Memory unit, 30 Wiring, 40, 42 Temperature distribution, 44, 46 Temperature gradient, 48, 50, 52 Temperature distribution, 100, 200 Wiring inspection device.

Claims

1. A wiring inspection device comprising: a temperature acquisition unit that acquires a temperature image along the longitudinal direction of a wiring formed on a printed circuit board between a heated portion of the wiring and another cooled portion of the wiring; and a calculation unit that determines whether or not there is a break in the wiring based on a value of the temperature gradient of the wiring calculated from the temperature image.

2. The wiring inspection device according to claim 1, further comprising: a heating section for heating the part; and a cooling section for cooling the other part.

3. The wiring inspection device according to claim 1, further comprising a heating section for heating said part.

4. The wiring inspection device according to claim 1, further comprising a cooling section for cooling said other section.

5. A wiring inspection device according to any one of claims 1 to 4, wherein the calculation unit calculates the temperature gradient value as an absolute value, and determines that the wiring is broken if the maximum absolute value of the temperature gradient is greater than a predetermined temperature gradient threshold value.

6. A wiring inspection device according to any one of claims 1 to 4, wherein the calculation unit calculates the value of the temperature gradient as an absolute value, and determines that the wiring is broken when the kurtosis of the absolute value of the temperature gradient is greater than a predetermined kurtosis threshold, or when the ratio of the peak value to the median value of the absolute value of the temperature gradient exceeds a predetermined ratio threshold.

7. A wiring inspection device as claimed in any one of claims 1 to 4, further comprising a memory unit that pre-measures and stores the value of the temperature gradient of the wiring when there is no break in the wiring, wherein the calculation unit compares the value of the temperature gradient of the wiring calculated from the temperature image with the value of the temperature gradient stored in the memory unit, and determines that there is a break in the wiring if the difference between the value of the temperature gradient of the wiring calculated from the temperature image and the value of the temperature gradient stored in the memory unit is equal to or greater than a predetermined allowable threshold.

8. A wiring inspection device as claimed in any one of claims 1 to 4, wherein the calculation unit compares the temperature gradient values ​​calculated from the temperature images of adjacent wiring on the printed circuit board, and determines that a wire is broken if the difference between the temperature gradient values ​​is equal to or greater than a predetermined temperature gradient difference threshold.

9. A wiring inspection method executed by a computer, comprising: a step of calculating a value of a temperature gradient of a wiring formed on a printed circuit board from a temperature image along the longitudinal direction of the wiring between a heated part of the wiring and another cooled part of the wiring; and a step of determining whether or not the wiring is broken based on the value of the temperature gradient of the wiring.

10. A wiring inspection program that causes a computer to execute the steps of: calculating a temperature gradient value of a wiring formed on a printed circuit board from a temperature image along the longitudinal direction of the wiring between a heated part of the wiring and another cooled part of the wiring; and determining whether or not the wiring is broken based on the temperature gradient value of the wiring.

Images