Eddy current inspection method

Abstract

The present application aims to provide an inspection method capable of determining the bonding state of an electrode to a substrate without contacting the electrode as an inspection object. A coil-embedded probe (1) in an alternating current application state is scanned along the formation direction of an electrode lead (40) as an inspection object. The coil-embedded probe (1) at the time of scanning is not in contact with the electrode lead (40), but is located above the electrode lead (40) at a prescribed distance from the surface of the electrode lead (40). Thereafter, a plurality of detection signals corresponding to a plurality of ultrasonic bonding portions (41) are obtained by an eddy current gauge (3). Finally, based on the comparison results of each of the plurality of detection signals with a reference level, the bonding state of the electrode lead (40) to a substrate (30) is determined. That is, for each of the plurality of ultrasonic bonding portions (41) provided in the electrode lead (40), which state of an unbonded state, a broken state, and a normal state is determined.

Description

Technical Field

[0001] This application relates to an eddy current inspection method that uses electrodes disposed on a substrate as the object of inspection and performs the inspection using an eddy current measuring device. Background Technology

[0002] As inspection methods that examine electrodes and the like provided on a substrate, there are, for example, the first inspection method disclosed in Patent Document 1 and the second inspection method disclosed in Patent Document 2.

[0003] The first inspection method is as follows: the condition of the electrode lead is determined based on the insulation resistance value measured between the outer surface of the metal cylinder of the electrode lead portion and the conductive pin of the electrode lead portion.

[0004] The first inspection method can be used even in confined spaces and is a relatively inexpensive solder-based inspection method that uses an inspection device.

[0005] The second inspection method takes the leads attached to the lead frame of the substrate as the object of inspection. The second inspection method includes the following first to fourth steps.

[0006] The first step... is to set up a pressure device and apply pressure from above to the lead wires of the lead frame, and to illuminate the ring-shaped lighting device.

[0007] The second step... is to take a picture using an imaging device in a manner that includes the lead wire joint, and then convert the image data obtained from the picture into a digital image signal using an A / D converter.

[0008] The third step... uses a processing device to extract the image data corresponding to the lead wire joint from the image data and binarize it by retaining the part that is brighter than a certain value.

[0009] The fourth step...determines the state of the lead wire based on the binarized image.

[0010] The second inspection method described above can accurately distinguish between unbonded leads and bonded leads.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Publication No. 2016-151484

[0014] Patent Document 2: Japanese Patent Application Publication No. 10-185527 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] However, although the first inspection method described above is non-destructive, it has the problem that it requires contact with the object being inspected in order to perform the inspection.

[0017] Furthermore, in the first inspection method, if the object being inspected contains a fractured part, there is a problem that if the contact point is not the fractured part but a normal part, the existence of the fractured part cannot be detected.

[0018] Furthermore, the second inspection method described above applies pressure to the lead wire, which is the object to be inspected, during the execution of the first step. Therefore, there is a problem that the inspection cannot be performed if the lead wire does not come into contact with the object to be inspected.

[0019] Furthermore, while the second inspection method can theoretically detect unbonded conditions at the ends of the leads, it still faces the problem of finding it extremely difficult to determine the bonding condition in the middle region of the leads. Moreover, the second inspection method also suffers from the problem of not being able to accurately identify broken sections of the leads.

[0020] The purpose of this application is to address the problems of conventional inspection methods that include the first and second inspection methods described above, and to provide an inspection method that can determine the bonding state of the electrode to the substrate without contacting the electrode that is the object to be inspected.

[0021] Methods for solving problems

[0022] The eddy current inspection method of this application is an eddy current inspection method using an eddy current measuring device. The eddy current measuring device induces eddy currents in the object under inspection and obtains a detection signal representing the state of the eddy currents. The eddy current measuring device has a detector with a built-in coil, and the object under inspection is an electrode disposed on a substrate. The eddy current inspection method includes: (a) applying an alternating current to the coil in the detector to achieve an alternating current applied state; and (b) scanning the detector in the alternating current applied state along the formation direction of the electrode. During the execution of step (b)... The detector does not contact the electrode, but is positioned above the electrode surface at a predetermined distance. During step (b), eddy currents are generated on the electrode surface. The detection signal is continuously acquired by the eddy current measuring device. The eddy current inspection method further includes: (c) a step of determining the bonding state of the electrode to the substrate based on a comparison result of the continuously acquired detection signal and a reference level. The electrode has a plurality of discrete bonding portions, which are assigned as bonding areas with the surface of the substrate. The eddy current inspection method further includes: (d) The step of selecting one joint from the plurality of joints as a reference joint is performed after step (a) and before step (b). The reference level is the signal value of the detection signal when the detector is arranged above the reference joint. During the execution of step (b), a plurality of detection signals are obtained corresponding to the plurality of joints. In step (c), (c-1) if there is a first detection signal among the plurality of detection signals that has a significant difference from the reference level in one of the positive and negative directions, the joint corresponding to the first detection signal among the plurality of joints is determined to be in an unjoined state. (c-2) if there is a second detection signal among the plurality of detection signals that has a significant difference from the reference level in the other of the positive and negative directions, the joint corresponding to the second detection signal among the plurality of joints is determined to be in a broken state. (c-3) if there is a third detection signal among the plurality of detection signals that does not belong to either the first or the second detection signal, the joint corresponding to the third detection signal among the plurality of joints is determined to be in a normal state.

[0023] Invention Effects

[0024] In step (b) of the eddy current testing method of this application, the detector is not in contact with the electrode, but scans along the formation direction of the electrode to obtain a detection signal.

[0025] Therefore, the eddy current testing method of this application can determine the bonding state of the electrode to the substrate during the execution of step (c) without contacting the electrode that is the object to be tested.

[0026] The purpose, features, aspects, and advantages of this application will become clearer from the following detailed description and accompanying drawings. Attached Figure Description

[0027] Figure 1 This is an explanatory diagram schematically illustrating an eddy current inspection method according to an embodiment of this application.

[0028] Figure 2 It means Figure 1 A flowchart illustrating the processing sequence of the eddy current inspection method in the embodiment shown.

[0029] Figure 3 This is an explanatory diagram showing the output waveform displayed on the monitor of a PC used for voltage detection.

[0030] Figure 4 It means Figure 2 The flowchart shows the processing sequence of the selection process for the calibration reference section.

[0031] Figure 5 This is a schematic diagram illustrating the inspection items required for eddy current pre-inspection.

[0032] Figure 6 It is an explanatory diagram schematically illustrating the inspection method based on basic techniques. Detailed Implementation

[0033] <Basic Techniques>

[0034] Figure 6 This is a schematic diagram illustrating the inspection method based on basic techniques. Figure 6 The XYZ orthogonal coordinate system is marked in the middle.

[0035] As shown in the figure, electrode leads 40 are provided on the substrate 30, and the electrode leads 40 have multiple ultrasonic bonding portions 41. Each of the multiple ultrasonic bonding portions 41 is a metal foil portion that forms a bonding area to the surface of the substrate 30 using ultrasonic bonding. That is, the electrode leads 40 are bonded to the surface of the substrate 30 by the multiple ultrasonic bonding portions 41.

[0036] The basic technical inspection method is to use a 90-degree peel strength tensile tester 60 to contact the electrode lead 40 to check the bonding status of each of the multiple ultrasonic joints 41 with the substrate 30.

[0037] The 90-degree peel strength tensile tester 60 has a clamp 62 connected via a connecting cable 64, which can hold the front end portion 40t of the electrode lead 40.

[0038] The basic technical inspection method involves holding the front end portion 40t of the electrode lead 40 by the clamp 62, raising the 90-degree peel strength tensile tester 60 along the tensile direction F6, and forcibly peeling the electrode lead 40 from the substrate 30.

[0039] Since the substrate 30 and the electrode leads 40 are disposed in Figure 6 As shown in the XY plane, the stretching direction F6 (+Z direction) has a 90-degree orientation relative to the substrate 30.

[0040] For example in Figure 6 In the figure, when the ultrasonic joint 41 located on the far left (-X direction side) is peeled off, the joint strength measured by the 90-degree peel strength tensile tester 60 becomes the measured joint strength.

[0041] In the basic technology, when the measured joint strength is above the reference strength, it can be determined as a normal joint 41A, and when it is below the reference strength, it can be determined as an unjoined joint 41C. In addition, the ultrasonic joint 41 can be visually inspected to confirm whether there is a gap 44, thus identifying whether it is a fractured joint 41B.

[0042] For example, such as Figure 6 As shown, consider the following scenario: from left to right, the four ultrasonic joints 41 are a normal joint 41A, a broken joint 41B, an unjoined joint 41C, and another normal joint 41A. In this case, the measured joint strength of the first and fourth ultrasonic joints 41 from the left is above the reference strength.

[0043] On the other hand, the measured bonding strength of the third ultrasonic joint 41 from the left is lower than the reference strength. Since the unbonded part 41C is in a state where there is a floating space 48 between it and the surface of the substrate 30, it cannot be confirmed by visual observation from above the electrode lead 40. In the inspection method of the basic technology, the unbonded part 41C can be accurately identified.

[0044] As described above, the basic technology inspection method involves using a 90-degree peel strength tensile tester 60 to peel the electrode lead 40 from the substrate 30, thereby inspecting the bonding status of each of the multiple ultrasonic joints 41 with the substrate 30.

[0045] However, in the basic inspection method, the assembly structure of the substrate 30 and the electrode lead 40 is destroyed by contacting the electrode lead 40 and then peeling the electrode lead 40 off the substrate 30. Therefore, the substrate 30 used in the inspection cannot be used.

[0046] That is, similar to the first and second inspection methods described as prior art, the basic technical inspection methods have the problem that the bonding state of the electrode to the substrate cannot be determined without contact with the electrode. The inspection method of the embodiments described below eliminates the above-mentioned problem.

[0047] <Implementation Method>

[0048] Figure 1 This is an explanatory diagram schematically illustrating an eddy current testing method according to an embodiment of this application. Figure 1 The XYZ orthogonal coordinate system is marked in the diagram. Furthermore, the eddy current measuring device 10, except for the coil-built detector 1, is not an object belonging to the XYZ orthogonal coordinate system. The oscilloscope 7, connecting cable 8, and the PC 9 for displaying the measured voltage are also not objects belonging to the XYZ orthogonal coordinate system.

[0049] As shown in the figure, electrode leads 40 are provided on the substrate 30, and the electrode leads 40 become the objects to be inspected. The electrode leads 40 have multiple ultrasonic bonding portions 41, and are bonded to the surface of the substrate 30 through multiple ultrasonic bonding portions 41 by ultrasonic bonding processing.

[0050] Electrode leads 40 correspond to "electrodes" provided on substrate 30, and multiple ultrasonic joints 41 correspond to "multiple joints" provided discretely on electrode leads 40.

[0051] Multiple ultrasonic bonding portions 41 are multiple metal foil portions allocated as bonding areas for bonding with the surface of the substrate 30. That is, multiple ultrasonic bonding portions 41 become bonding areas for bonding with the surface of the substrate 30 using ultrasonic bonding.

[0052] The electrode lead 40 has a film thickness of approximately 1.1 mm and is formed on the surface of the substrate 30 extending along the X direction. Each ultrasonic joint 41 has the same size, with an area of ​​at least a square comprising 1 mm × 1 mm, and a thickness of, for example, approximately 1.1 mm.

[0053] The eddy current testing method of this embodiment is a method of checking the bonding status of each of the multiple ultrasonic joints 41 with the surface of the substrate 30 without contacting the electrode leads 40 using an eddy current measuring device 10.

[0054] The eddy current measuring device 10 comprises, as its main components, a coil-embedded detector 1, a connecting cable 2, an eddy current measuring instrument 3, a connecting detector 5, and a detector clip 11. The eddy current measuring device 10 is a device that obtains a detection signal indicating the state of the eddy currents occurring on the surface of the electrode lead 40.

[0055] The coil-embedded detector 1 is a detector with a built-in coil inside. By flowing an alternating current of a predetermined frequency through the built-in coil within the coil, the coil-embedded detector 1 is brought into an alternating current applied state, generating a magnetic field in the built-in coil. Additionally, the eddy current measuring device 3 has an alternating current application function.

[0056] The detector clip 11 holds the coil-in-the-coil detector 1 with the front end of the coil-in-the-coil detector 1 exposed.

[0057] The coil-embedded detector 1 is connected to the eddy current meter 3 via the connecting cable 2. The eddy current meter 3 performs a prescribed operation to obtain a detection signal based on the eddy current detection result detected by the coil-embedded detector 1. The detection signal is a signal that is positively correlated with the eddy current detection result.

[0058] As a result of eddy current detection, for example, considering the impedance of the built-in coil within the coil-embedded detector 1, the state change of the eddy current can be identified by the change in the impedance of the built-in coil. Therefore, the detection signal obtained by the eddy current measuring device 3 becomes a signal representing the state of the eddy current occurring on the surface of the electrode lead 40. In addition, the state of the eddy current includes the magnitude and distribution of the eddy current.

[0059] As an external device connected to the eddy current measuring device 10, a detection voltage display PC (Personal Computer) 9 is provided. The detection voltage display PC 9 is connected to the eddy current measuring device 10 via an oscilloscope 7 and a connecting cable 8 to a connection detector 5.

[0060] The detection signal obtained in the eddy current measuring device 3 is transmitted to the oscilloscope 7 via the connection detector 5. The oscilloscope 7 converts the received detection signal into a display detection signal that can be displayed on the monitor of the detection voltage display PC 9. This display detection signal is output to the detection voltage display PC 9 via the connection cable 8.

[0061] The PC 9 for voltage detection display displays the output waveform LV of the detection signal on the display.

[0062] The eddy current measuring device 10 configured in this way is used to perform the eddy current testing method of this embodiment. The eddy current testing method of this embodiment is a method for determining the bonding state of the plurality of ultrasonic joints 41 provided on the electrode lead 40 to the surface of the substrate 30.

[0063] Figure 2 It means Figure 1 The flowchart shows the processing sequence of the eddy current inspection method of this embodiment. Hereinafter, refer to... Figure 2The processing steps of the eddy current inspection method in this embodiment will be explained.

[0064] First, in step S1, an alternating current is applied to the built-in coil of the coil-built-in detector 1 to form an alternating current application state.

[0065] Following step S1, in step S2, one of the multiple ultrasonic joints 41, which are multiple joints, is selected as the calibration reference (reference joint). The selection of the calibration reference will be described in detail later.

[0066] For ease of explanation, the following assumes... Figure 1 The leftmost ultrasonic joint 41 among the four ultrasonic joints 41 shown is selected as the calibration reference 41S (reference joint).

[0067] After step S2, in step S3, the initial setting of the calibration reference part 41S is performed. That is, the front end of the coil-built detector 1 is positioned above the surface of the calibration reference part 41S at a predetermined distance, and eddy currents are generated on the surface of the calibration reference part 41S.

[0068] Therefore, based on the eddy current detection results obtained from the coil-in-the-loop detector 1, a calibration reference detection signal is obtained from the eddy current measuring device 3. Thus, by pressing the calibration button or similar device provided on the eddy current measuring device 3, a calibration process is performed, and an initial setting is performed with the signal value of the calibration reference detection signal becoming the initial setting value ("0"). In this way, the signal value "0" represented by the calibration reference detection signal corresponding to the calibration reference unit 41S becomes the reference level. That is, the reference level becomes the signal value of the detection signal when the coil-in-the-loop detector 1 is positioned above the calibration reference unit 41S.

[0069] After step S3 is executed, if the signal value of the detection signal obtained from the eddy current measuring device 3 is positive, it becomes a signal value higher than the reference level; if the signal value of the detection signal is negative, it becomes a signal value lower than the reference level.

[0070] Next, in step S4, an eddy current check is performed on the electrode lead 40. That is, a scan SC1 is performed, in which the coil-embedded detector 1 with an alternating current applied scans along the forming direction (X direction) of the electrode lead 40. The starting position of the scan SC1 is above the left end of the electrode lead 40, and the scan speed of the scan SC1 along the X direction is set to, for example, 1 m / s.

[0071] During the execution of step S4, the coil-embedded detector 1 does not contact the electrode lead 40, but is positioned above it at a predetermined distance from the surface of the electrode lead 40. The predetermined distance is set to approximately 1 mm.

[0072] Therefore, during the execution of step S4, eddy currents are generated on the surface of the electrode lead 40, and the eddy current detection results are continuously obtained in the coil-embedded detector 1. Furthermore, through the computational processing of the eddy current measuring device 3, a detection signal based on the eddy current detection results is continuously obtained. As described above, the detection signal indicates the state of the eddy currents generated on the surface of the electrode lead 40.

[0073] During the execution of scanning SC1, the time period of the front end of the coil-in-the-loop detector 1 passing above each of the multiple ultrasonic joints 41 can be derived based on the position and size of each ultrasonic joint 41 and the scanning speed of the coil-in-the-loop detector 1.

[0074] Therefore, by executing step S4, multiple detection signals corresponding to multiple ultrasonic joints 41 can be obtained.

[0075] Finally, in step S5, an ultrasonic bonding state determination process is performed. That is, in step S5, the bonding state of the electrode lead 40 to the substrate 30 is determined based on the comparison results of the continuously obtained detection signals and the reference level.

[0076] In this embodiment, in step S5, the bonding state of each of the multiple ultrasonic joints 41 on the surface of the substrate 30 is determined based on the comparison results of multiple detection signals corresponding to the multiple ultrasonic joints 41 with the reference level.

[0077] The determination process performed in step S5 is to determine whether each of the multiple ultrasonic joints 41 belongs to a normal joint 41A, a broken joint 41B, or an unjoined joint 41C. The determination process performed in step S5 includes the following first to third determinations.

[0078] The first determination... If, among the multiple detection signals corresponding to the multiple ultrasonic joints 41, there is a first detection signal that is significantly different from the reference level (“0”) in the positive direction, the ultrasonic joint 41 corresponding to the first detection signal among the multiple ultrasonic joints 41 is determined to be in an unjoined state. As a result, the unjoined ultrasonic joint 41 is classified as unjoined joint 41C.

[0079] The second determination… If, among the aforementioned multiple detection signals, there exists a second detection signal that differs significantly from the aforementioned reference level in the negative direction, the ultrasonic joint 41 corresponding to the aforementioned second detection signal among the multiple ultrasonic joints 41 is determined to be in a broken state. As a result, the ultrasonic joint 41 in the broken state is classified as a broken part 41B.

[0080] The third determination... If, among the aforementioned multiple detection signals, there is a third detection signal that does not belong to either the first or second type of detection signal, the ultrasonic joint 41 corresponding to the third detection signal among the multiple ultrasonic joints 41 is determined to be in a normal state. As a result, the ultrasonic joint 41 in a normal state is classified as a normal joint 41A.

[0081] The following explains the reasons why the signals can be classified as the first to the third type of detection signals based on the first to third criteria.

[0082] like Figure 1 As shown, at least a portion of the fracture portion 41B contains a gap 44. In most cases, the gap 44 extends through the electrode lead 40. Therefore, the fracture portion 41B has a first distance characteristic, namely, the presence of a portion in the fracture portion 41B that is longer than the distance from the coil inside the coil-embedded detector 1 compared to the normal joint portion 41A corresponds to the amount of the gap 44 present.

[0083] like Figure 1 As shown, there is a floating space 48 between the unbonded portion 41C and the surface of the substrate 30. Therefore, the unbonded portion 41C has a second distance characteristic, that is, the existence of a region in the unbonded portion 41C where the distance from the coil inside the coil-embedded detector 1 is shorter than that of the normal bonded portion 41A corresponds to the amount of the floating space 48.

[0084] The eddy current detection result obtained in the coil-embedded detector 1 exhibits the property that the closer the distance from the ultrasonic joint 41 to the built-in coil within the coil-embedded detector 1, the larger the eddy current detection result becomes. Therefore, when the eddy current measuring device 3 obtains a detection signal that is positively correlated with the eddy current detection result, it is speculated that the signal value of the detection signal increases in the order of fracture 41B, normal joint 41A, and unjoined joint 41C.

[0085] Therefore, based on the first and second distance characteristics between the normal joint portion 41A, the fracture portion 41B, and the unjoined portion 41C, the first to third determinations can be made as described above.

[0086] In addition, the calculation formula used by the eddy current measuring device 3 can also result in a detection signal that is negatively correlated with the eddy current detection result.

[0087] In this case, it is speculated that the signal value of the detection signal has the property of decreasing in the order of fracture portion 41B, normal joint portion 41A and unjoined portion 41C. Therefore, based on the first and second distance characteristics described above, a determination equivalent to the first to third determinations described above can be made.

[0088] That is, multiple ultrasonic joints 41 can be used as multiple joints, so that the first to third determinations described above can be extended as follows.

[0089] First determination... In the case where there is a first detection signal among multiple detection signals that has a significant difference from the reference level in one of the positive and negative directions, the joint corresponding to the first detection signal among the multiple joints is determined to be an unjoined joint 41C in an unjoined state.

[0090] The second determination... In the case where there is a second detection signal among multiple detection signals that is significantly different from the reference level in another direction, either the positive or negative direction, the joint corresponding to the second detection signal among the multiple joints is determined to be a fractured joint 41B in a fractured state.

[0091] The third determination... In the case where there is a third detection signal among the multiple detection signals that does not belong to either the first or the second type of detection signal, the joint that corresponds to the third detection signal among the multiple joints is determined to be a normal joint 41A in a normal joint state.

[0092] Figure 3 This is an explanatory diagram showing the output waveform LV displayed on the PC 9 monitor for voltage detection. The output waveform LV shows the relationship with... Figure 1 The corresponding inspection results for electrode lead 40 shown.

[0093] In order to obtain Figure 3 The output waveform LV shown is an alternating current applied to the built-in coil of the coil-embedded detector 1, using both a first and a second alternating current. The first alternating current has a frequency set to 600 kHz and a phase set to 65.0 degrees. The second alternating current has a frequency set to 600 kHz and a phase set to 225.0 degrees.

[0094] Furthermore, by applying a first alternating current to the built-in coil within the coil-built-in detector 1, a first eddy current detection result is obtained in the coil-built-in detector 1; by applying a second alternating current to the built-in coil, a second eddy current detection result is obtained in the coil-built-in detector 1.

[0095] The eddy current measuring device 3 performs prescribed calculations based on the first and second eddy current detection results to obtain a detection signal.

[0096] The detection signal obtained in the eddy current measuring device 3 is transmitted to the oscilloscope 7 via the connection detector 5. The oscilloscope 7 converts the received detection signal into a display detection signal that can be displayed on the detection voltage display PC 9. This display detection signal is output to the detection voltage display PC 9 via the connection cable 8 and displayed on the display of the detection voltage display PC 9. Figure 3 The output waveform LV is shown.

[0097] like Figure 1 As shown, the electrode lead 40 has four ultrasonic joints 41, and the leftmost ultrasonic joint 41 is selected as the calibration reference 41S.

[0098] As described above, the time interval over which the front end of the coil-embedded detector 1 passes above each of the four ultrasonic joints 41 can be derived based on the position and size of each ultrasonic joint 41 and the scanning speed of the coil-embedded detector 1. Hereinafter, for ease of explanation, the four ultrasonic joints 41 will be referred to as the first, second, third, and fourth joints from left to right.

[0099] like Figure 3 As shown, the output waveform LV in the time period T1 to T4 becomes the first to fourth detection signals corresponding to the first to fourth junctions. Here, the positive direction threshold representing the significant difference in the positive direction is set to "+0.3V", and the negative direction threshold representing the significant difference in the negative direction is set to "-0.2V".

[0100] Since the first junction is the calibration reference 41S, the signal value of the output waveform LV in the time period T1 shows 0V. Therefore, the first detection signal becomes a third detection signal that does not belong to either the first or the second type of detection signal mentioned above, and thus the first junction is determined to be the normal junction 41A in a normal state.

[0101] The minimum signal value of the output waveform LV during time period T2 is below -0.2V. Therefore, the second detection signal becomes the second type of detection signal described above, and thus the second joint is determined to be the fractured part 41B in a fractured state.

[0102] The maximum signal value of the output waveform LV in time period T3 exceeds +0.3V. Therefore, the third detection signal becomes the first detection signal mentioned above, and thus the third joint is determined to be an unjoined joint 41C in an unjoined state.

[0103] The signal value of the output waveform LV in time period T4 is around 0.1V, but the minimum signal value exceeds -0.2V and the maximum signal value is below +0.3V. Therefore, the fourth detection signal becomes a third detection signal that does not belong to either the first or the second type of detection signal mentioned above, and thus the fourth junction is determined to be a normal junction 41A in a normal state.

[0104] In step S4 of the eddy current testing method of this embodiment, the coil-embedded detector 1 scans along the formation direction of the electrode lead 40 without contacting the electrode lead 40, thereby obtaining a detection signal from the eddy current measuring device 3.

[0105] Therefore, the eddy current inspection method of this embodiment can determine the bonding state of the electrode lead 40 and the surface of the substrate 30 without contacting the electrode lead 40 which is the object to be inspected during the execution of step S5.

[0106] The eddy current inspection method of this embodiment performs first to third determinations during the execution of step S5, thereby enabling the determination of the state of the multiple ultrasonic joints 41 in the unjoined state, broken state, and normal state without contacting the electrode lead 40.

[0107] Figure 4 It means Figure 2 The flowchart below shows the processing sequence of the selection process for the calibration reference unit 41S, as shown in step S2. Hereinafter, refer to... Figure 4 The selection of the calibration reference section 41S in step S2 will be explained.

[0108] First, in step S21, a pre-substrate is prepared. Unbonded pre-electrodes are disposed on the surface of the pre-substrate.

[0109] The pre-substrate and pre-electrode are components prepared separately from the substrate 30 and the electrode lead 40. The pre-substrate is the substrate corresponding to the substrate 30, and the pre-electrode is the electrode corresponding to the electrode lead 40. Therefore, the pre-substrate is preferably made of the same material and the same size as the substrate 30, and the pre-electrode is preferably made of the same material and the same size as the electrode lead 40.

[0110] Next, in step S22, a pressing process is performed on the preparatory electrode. That is, at least the preparatory reference area of ​​the preparatory electrode is pressed from above using a roller or the like. Furthermore, the preparatory reference area is a portion of the preparatory electrode, preferably located at the same level as the ultrasonic bonding position 41.

[0111] As a result, the preparation reference area of ​​the preparation electrode is completed, and the preparation reference area is in close contact with the surface of the preparation substrate. In addition, in order to improve the adhesion between the preparation reference area and the surface of the preparation substrate, it is preferable to perform a pressing process on the entire area of ​​the preparation electrode.

[0112] Next, a preliminary reference signal is obtained in step S23. That is, the coil-in-the-loop detector 1 is positioned above the surface of the preliminary reference area with its front end not in contact with the preliminary electrode. The predetermined distance is set to approximately 1 mm.

[0113] Therefore, during the execution of step S23, eddy currents are generated on the surface of the pre-reference region in the pre-electrode, and the eddy current detection result is obtained in the coil-embedded detector 1. Furthermore, through the computational processing of the eddy current measuring device 3, a pre-reference signal based on the eddy current detection result is obtained.

[0114] It is speculated that the signal value of the pre-reference signal is the same as or approximately the signal value of the detection signal of the normal joint 41A. This is because, through step S22, the pre-reference area is set to be in close contact with the surface of the pre-substrate.

[0115] After step S23 is executed, in step S24, the calibration button on the eddy current measuring device 3 is pressed to perform calibration processing so that the signal value of the preparatory reference signal becomes "0".

[0116] After the above correction process, the detection signal obtained from the eddy current measuring device 3 has the following properties: When the detection signal value is positive, it means that the signal value is higher than that of the preliminary reference signal; when the detection signal value is negative, it means that the signal value is lower than that of the preliminary reference signal.

[0117] Next, in step S25, the electrode leads 40 on the substrate 30 are used as the object of inspection, and an eddy current pre-inspection is performed to obtain multiple pre-detection signals.

[0118] Figure 5 This is a schematic diagram illustrating the inspection items required for eddy current pre-inspection. In Figure 5 The XYZ orthogonal coordinate system is marked in the text. However, the eddy current measuring device 10 is not an object belonging to the XYZ orthogonal coordinate system. Furthermore, in... Figure 5 The illustration of substrate 30 is omitted.

[0119] As shown in the figure, for the plurality of ultrasonic joints 41 of the electrode lead 40 that are the object of inspection, scanning is performed by transversely cutting above each of the plurality of ultrasonic joints 41 along the Y direction, which is perpendicular to the forming direction (X direction) of the electrode lead 40. Figure 5 In the example shown, three ultrasonic joints 41 are shown, and therefore the three ultrasonic joints 41 are scanned three times SC11 to SC13.

[0120] Thus, in step S25, by sequentially performing scans SC11 to SC13, the coil-embedded detector 1 with applied alternating current is sequentially positioned above each of the plurality of ultrasonic joints 41. During scans SC11 to SC13, the lower front end of the coil-embedded detector 1 is positioned at a height of approximately 1 mm above the plurality of ultrasonic joints 41. Therefore, during the execution of scans SC11 to SC13, eddy currents are generated on the surface of each of the plurality of ultrasonic joints 41.

[0121] Subsequently, in the coil-embedded detector 1, eddy current detection results are obtained by scanning SC11 to SC13. For ease of explanation, the eddy current detection results obtained by scanning SC11 to SC13 are referred to as the first to third eddy current detection results.

[0122] Furthermore, through the calculation and processing of the eddy current measuring device 3, first to third preliminary detection signals based on the first to third eddy current detection results are obtained. The first to third preliminary detection signals become multiple preliminary detection signals.

[0123] Finally, in step S26, a calibration reference 41S is determined from the plurality of ultrasonic joints 41. That is, the preliminary detection signal with the signal value closest to the "0" after correction in step S24 among the signal values ​​of the plurality of preliminary detection signals obtained in step S25 is determined as the determined preliminary detection signal.

[0124] Next, the ultrasonic joint 41 that corresponds to the aforementioned determination of the pre-detection signal is selected as the calibration reference 41S. This calibration reference 41S becomes the reference joint. Thus, by performing step S2, which includes steps S21 to S26, a calibration reference 41S can be selected from the plurality of ultrasonic joints 41.

[0125] In addition, Figure 5 In the example shown, the signal value closest to "0" among the first to third preliminary detection signals obtained by scanning SC11 to SC13 is selected as the preliminary detection signal.

[0126] The eddy current testing method of this embodiment, by performing step S2 including steps S21 to S26, can select a correction reference part 41S as a reference part from a plurality of ultrasonic joints 41 without contacting the electrode lead 40 that is the object to be tested.

[0127] As a result, the eddy current inspection method of this embodiment can obtain the reference level with high accuracy by selecting the calibration reference part 41S with high reliability, and can determine the bonding state of each of the multiple ultrasonic joints 41 to the surface of the substrate 30 with high accuracy.

[0128] The electrode leads 40 are bonded to the surface of the substrate 30 through a plurality of ultrasonic bonding portions 41 by ultrasonic bonding process. That is, the plurality of ultrasonic bonding portions 41 each become a bonding area with the surface of the substrate 30.

[0129] Regarding the eddy current inspection method of this embodiment, it has been confirmed that as long as the thickness of each of the plurality of ultrasonic joints 41 is 0.01 mm or more, the bonding state of each of the plurality of ultrasonic joints 41 to the substrate 30 can be determined with high precision.

[0130] Therefore, according to the eddy current inspection method of this embodiment, for example, for each of the multiple ultrasonic joints 41 having a relatively thin film thickness of about 0.11 mm, it is also possible to determine the bonding state of the joints with the surface of the substrate 30.

[0131] Regarding the eddy current inspection method of this embodiment, it has been confirmed that as long as each of the multiple ultrasonic joints 41 has a planar shape with a length of 1 mm on one side when viewed from above, the bonding state of each substrate 30 of the multiple ultrasonic joints 41 can be determined with high precision.

[0132] Therefore, according to the eddy current inspection method of this embodiment, for example, for a plurality of ultrasonic joints 41 with a square or approximately 1 mm long side, the bonding state of the joint with the substrate 30 can also be determined.

[0133] In the eddy current inspection method of this embodiment, the scanning speed of the coil-embedded detector 1 during the eddy current inspection performed in step S4 is set to 1 m / s or more.

[0134] Therefore, according to the eddy current inspection method of this embodiment, the scanning speed of the coil-embedded detector 1 executed in step S4 is 1 m / s or more, so the execution time of step S4 can be suppressed to a relatively short time, thereby shortening the inspection time.

[0135] That is, even for electrode leads 40 with relatively long forming lengths, the inspection time of the eddy current inspection method of this embodiment will not be prolonged.

[0136] Furthermore, in the eddy current detection method of this embodiment, first and second alternating currents with the same frequency but different phases are used as the alternating current applied in step S1, thereby enabling the acquisition of a detection signal with higher accuracy in step S4.

[0137] As a result, the eddy current inspection method of this embodiment can accurately determine the bonding state of the electrode lead 40 to the surface of the substrate 30.

[0138] <Other>

[0139] Furthermore, in the above-described embodiment, the alternating current applied to the coil-embedded detector 1 is a first and a second alternating current with the same frequency but different phases. However, the same effect can be expected as long as at least one of the frequencies and phases of the first and second alternating currents is different.

[0140] Furthermore, the eddy current measuring device 3 can independently obtain a first detection signal based on the first eddy current detection result and a second detection signal based on the second eddy current detection result. The first detection signal corresponds to the first alternating current, and the second detection signal corresponds to the second alternating current.

[0141] In this case, since two output waveforms LV are obtained, therefore, as Figure 1 As shown, it is preferable to use two independent detectors 5a and 5b as the connection detector 5.

[0142] Furthermore, even using a single alternating current as the alternating current applied in step S1, it is expected to be effective in determining the bonding state of the surface bond between the electrode lead 40 and the substrate 30. This is because, generally speaking, the eddy current detector 3 can obtain a detection signal based on the eddy current detection result even when using a single alternating current.

[0143] That is, even if a single alternating current is used, the alternating current applied in step S1 can be used to make the same determination as the first to third determinations described above, based on the first and second distance characteristics between the normal joint 41A, the broken part 41B and the unjoined part 41C.

[0144] In addition, as Figure 2 The selection process of the calibration reference section 41S in step S2 shown can also be replaced by... Figure 4 The process shown uses the following manual selection process: manually lift the area near each of the multiple ultrasonic joints 41, and select the ultrasonic joint 41 with a stable joint state as the correction reference 41S.

[0145] However, when using manual selection, contact with electrode lead 40 is required. Furthermore, since the aforementioned manual selection is based on subjective human intervention, it cannot be said that the selection accuracy of the calibration reference unit 41S is also high. Therefore, as... Figure 2 The selection process of the calibration reference section 41S shown is preferably performed. Figure 4 The processing shown.

[0146] While this application has been described in detail, the foregoing description is illustrative in all respects and the application is not limited thereto. It should be understood that numerous variations not illustrated can be conceived without departing from the scope of this application.

[0147] Explanation of reference numerals in the attached figures

[0148] 1. Coil-embedded detector

[0149] 3 Eddy Current Measuring Instrument

[0150] 9. PC for voltage detection and display

[0151] 10 Eddy Current Measuring Device

[0152] 30 substrate

[0153] 40 electrode leads

[0154] 41 Ultrasonic joint

[0155] 41A Normal Joint

[0156] 41B Fracture section

[0157] 41C Unjoined portion

[0158] 41S Calibration Reference Section

Claims

1. An eddy current inspection method, comprising an eddy current inspection method using an eddy current measuring device, wherein the eddy current measuring device induces eddy currents in the object under inspection and obtains a detection signal representing the state of the eddy currents, the eddy current measuring device having a detector with a built-in coil, and the object under inspection being an electrode disposed on a substrate, the eddy current inspection method comprising: (a) the step of applying an alternating current to the coil within the detector to achieve an alternating current applied state; and (b) The step of scanning along the forming direction of the electrode with the detector in the applied alternating current state, wherein during the execution of step (b), the detector is not in contact with the electrode, but is positioned above the surface of the electrode at a predetermined distance, and eddy currents are generated on the surface of the electrode during the execution of step (b), and the detection signal is continuously obtained by the eddy current measuring device. The eddy current testing method also has the following features: (c) The step of determining the bonding state of the electrode and the substrate based on the comparison results of the continuously obtained detection signals and the reference level. The electrode has a plurality of discretely spaced joints, which are assigned as engagement regions with the surface of the substrate. The eddy current testing method also has the following features: (d) The step of selecting one joint from the plurality of joints as the reference joint, performed after step (a) and before step (b). The reference level is the signal value of the detection signal when the detector is disposed above the reference joint. During the execution of step (b), multiple detection signals are obtained corresponding to the multiple joints. In step (c), (c-1) If, among the plurality of detection signals, there exists a first detection signal that differs significantly from the reference level in either the positive or negative direction, the joint corresponding to the first detection signal among the plurality of joints is determined to be in an unjoined state. (c-2) If, among the plurality of detection signals, there exists a second detection signal that differs significantly from the reference level in one of the positive or negative directions, the joint corresponding to the second detection signal among the plurality of joints is determined to be in a fracture state. (c-3) If there is a third detection signal among the plurality of detection signals that does not belong to either the first detection signal or the second detection signal, the joint that corresponds to the third detection signal among the plurality of joints is determined to be in a normal state.

2. The eddy current testing method as described in claim 1, Step (d) includes: (d-1) Step of preparing a pre-substrate on which pre-electrodes in an unbonded state are disposed on the surface; (d-2) Pressing the pre-reference area in the pre-electrode from above to make the pre-reference area adhere tightly to the surface of the pre-substrate; as well as (d-3) The step of placing the detector in the applied alternating current state above the pre-reference region of the pre-electrode, wherein eddy currents are generated on the surface of the pre-reference region during the execution of step (d-3), and a pre-reference signal is obtained by the eddy current measuring device. The eddy current testing method also includes... (d-4) The step of sequentially positioning the detector in the alternating current applied state above the plurality of joints involves generating eddy currents on the surfaces of the plurality of joints during the execution of step (d-4), and obtaining a plurality of preliminary detection signals corresponding to the plurality of joints through the eddy current measuring device. The eddy current testing method also includes... (d-5) The step of determining the signal with the closest signal value to the pre-reference signal among the plurality of pre-detection signals as the pre-detection signal and determining the joint corresponding to the pre-detection signal among the plurality of joints as the reference joint.

3. The eddy current testing method as described in claim 1 or 2, The plurality of joints are joint areas that are joined to the surface of the substrate using ultrasonic bonding. The thickness of each of the plurality of joints is 0.01 mm or more.

4. The eddy current testing method as described in claim 1 or 2, The plurality of joints each have a planar shape, including a square with one side having a length of 1 mm, when viewed from above.

5. The eddy current testing method as described in claim 1 or 2, The scanning speed of the detector performed in step (b) is 1 m / s or more.

6. The eddy current testing method as described in claim 1 or 2, The alternating current includes a first alternating current and a second alternating current, wherein at least one of the frequencies and phases of the first alternating current and the second alternating current is different.

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