JP4328066B2 - Film thickness inspection apparatus and film thickness inspection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film thickness inspection apparatus and a film thickness inspection method for inspecting the thickness of a film formed on an electronic component, for example.
[0002]
[Prior art]
A chip resistor used in a small electronic device or the like usually has a resistor laminated on a ceramic substrate, and the electrodes are provided with a nickel plating layer at the end of the laminate, and further on the nickel layer. In addition, a solder layer is provided. That is, since the nickel plating layer is covered with the solder layer, the presence or absence of the nickel plating layer and its thickness cannot be inspected depending on the appearance selection.
[0003]
FIG. 15 shows a cross-sectional structure of a square chip resistor 500. FIG. 15A shows a nickel plating layer 502 of a resistor with a very thin portion (plating failure portion) 520 of the plating thickness. (B) shows a state when the chip resistor of (a) is mounted on the printed circuit board 515.
[0004]
As can be seen from FIG. 15A, even if the plated layer of the chip resistor is thin and there is a cut, the solder layer 505 is formed normally. Therefore, as shown in (b), after mounting the chip resistor 500, the solder layer 505 is melted by heating, and the solder disappears from the end face of the resistor at the cut 530 of the nickel layer, causing poor conduction in that portion. Sometimes.
[0005]
Therefore, in order to eliminate such problems, conventionally, suction sorting inspection of defective products using magnets has been performed by utilizing the fact that nickel is a magnetic material. In this method, when a magnet is arranged near the electrode of the chip resistor and the nickel layer of the resistor is formed with a normal thickness, the resistor is attracted to the magnet, but the nickel plating thickness is thin, Alternatively, when there is no plating layer, the basic principle of selection is that the resistor is not attracted to the magnet.
[0006]
As another measurement method, there is a conventional film thickness measurement method using eddy current loss. For example, in Japanese Patent Application Laid-Open No. 62-144002, an eddy current is generated by applying an alternating magnetic field from a self-excited coil to a metal thin film, thereby reducing the Q value of the coil and oscillating it. A film thickness measuring device that is extracted as the magnitude of the amplitude is disclosed.
[0007]
Furthermore, Japanese Patent Laid-Open No. 2001-289606 uses eddy current as a detection principle in view of the problem of the conventional measurement method using eddy current loss, that is, it is easily influenced by the shape of the measurement target. Further, the present invention relates to a method and an apparatus that enable film thickness measurement on a curved surface by providing a film thickness measurement coil and a curvature measurement coil.
[0008]
[Problems to be solved by the invention]
However, the above conventional inspection method (defective product suction selection inspection method using a magnet) has the following problems. That is, (1) even if the nickel plating layer on the electrode end surface (surface facing the magnet) is thin, the upper and lower surfaces of the electrode (one surface connected to the above end surface and the surface direction rotated 90 degrees with respect to the magnet) If the nickel plating layer is thick, the resistor is attracted to the magnet, and a defective product is erroneously determined as a good product. (2) Since the chip size of the chip resistor has been reduced with the miniaturization of the device, the weight of the element itself is very light, and the element to be inspected adheres to the magnet due to static electricity, dirt, etc. instead of magnetic force. This method cannot be used for small and lightweight parts. (3) Since it is only determined whether the magnet is attached or not, it is not possible to determine how much the nickel plating thickness variation is. Therefore, the control range of the nickel plating thickness is reduced in manufacturing the resistor. (4) When the product to be inspected is magnetized (magnetized) from the beginning, an error occurs in the quality determination.
[0009]
In addition, if the thickness of the nickel plating layer is measured by cutting the cross section of a plurality of products, the state of the nickel layer and its variation distribution can be known accurately, Involves destruction of the inspected product. As a result, it takes time and effort, and there is a problem that it is not practical as a sampling inspection method.
[0010]
On the other hand, the above-described method using eddy current loss as a measurement principle has a problem in that nickel and solder cannot be distinguished in an electrode portion of a resistor having a layered structure of nickel and solder.
[0011]
[Means for Solving the Problems]
This invention is made | formed in view of the subject mentioned above, The place made into the objective is providing the film thickness inspection apparatus and film thickness inspection method which measure the film thickness non-destructively about a test object.
[0012]
Another object of the present invention is to provide a film thickness inspection apparatus and a film thickness inspection method for quantitatively measuring the film thickness of an object to be inspected.
[0013]
As a means for achieving this object and solving the above-mentioned problems, for example, the following configuration is provided. That is, Coating that constitutes the electrode of electronic parts Inspect the film thickness of Electrode electrode A film thickness inspection apparatus, Each of which is composed of a finite-length solenoid and is arranged at a predetermined interval, a transmission coil and a reception coil, a high-frequency signal generation circuit for generating an alternating magnetic field between the transmission coil and the reception coil, and induction in the reception coil High-frequency signal amplitude measuring circuit for measuring the amplitude of the voltage to be applied, and a positioning mechanism for arranging the electronic component between the transmitting coil and the receiving coil And The electrode of the electronic component includes a magnetic metal layer made of a magnetic material, and the positioning mechanism causes the central axis of the solenoid constituting the transmitting coil and the receiving coil to be substantially perpendicular to the thickness direction of the magnetic metal layer. The electronic coil is arranged so that a part of the magnetic metal layer to be inspected is located between the transmitting coil and the receiving coil, and the high-frequency signal amplitude Identification of defects in the thickness of the magnetic metal layer from the amplitude of the voltage measured by the measurement circuit It is characterized by doing.
[0015]
For example, A conductive pattern connecting the transmitting coil and the high-frequency signal generating circuit, and a conductive pattern connecting the receiving coil and the high-frequency signal amplitude measuring circuit. Runs parallel to the central axis of the magnetic flux of the alternating magnetic field. So that it is formed on the circuit board It is characterized by that.
[0016]
As another means for solving the above-described problem, for example, the following configuration is provided. That is, Coating that constitutes the electrode of electronic parts Inspect the film thickness of Electrode electrode A film thickness inspection method, The electrode is composed of a magnetic metal layer having magnetism and a nonmagnetic metal layer covering the magnetic metal layer, and the central axis of a finite-length solenoid that constitutes a transmission coil and a reception coil that generate an alternating magnetic field is the above-mentioned The transmitting coil and the receiving coil are arranged at a predetermined interval in a direction substantially perpendicular to the thickness direction of the magnetic metal layer, and a part of the magnetic metal layer to be inspected is arranged between the transmitting coil and the receiving coil. The electronic component is placed so that it is located between the two, and defects in the thickness of the magnetic metal layer are identified from the amplitude of the voltage induced in the receiving coil. It is characterized by doing.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of a film inspection apparatus according to the present embodiment. A film inspection apparatus (hereinafter simply referred to as an inspection apparatus) shown in FIG. 1 passes through a high-frequency signal generation circuit 2 that generates a high-frequency signal for exciting a transmission coil, which will be described later, an inspection head 1, and an inspection object. A high-frequency signal amplitude measurement circuit 3 that measures the amplitude of a high-frequency signal received by a receiving coil described later is provided.
[0018]
The inspection head 1 includes an inspection head pattern A16 for guiding the signal transmitted from the high-frequency signal generation circuit 2 to the transmission coil 12, and an inspection head for transmitting the high-frequency signal received by the reception coil 13 to the high-frequency signal amplitude measurement circuit 3. Positioning mechanisms 15a, 15b, and 15c that keep the relative position of the inspected resistor 11 that is the object to be inspected between the pattern B17 and the transmitting coil 12 and the receiving coil 13 are provided.
[0019]
The transmission coil 12 and the reception coil 13 have a structure in which cores 12a and 13b are arranged at the center. In addition, the resistor 11 to be inspected is a top view thereof, and a portion indicated by reference numeral 18 is an end face electrode on the side where the thickness of the internal nickel plating layer of the resistor is desired to be inspected.
[0020]
An inspection signal (sine wave) of several MHz to several tens of MHz is generated from the high frequency signal generation circuit 2, and the signal is guided to the inspection head pattern A 16 in the inspection head 1 via the coaxial cable 4 and the attenuator 5. It is burned. As a result, the transmission coil 12 is excited by the high frequency inspection signal.
[0021]
The transmitting coil 12 and the receiving coil 13 arranged so as to sandwich the electrode to be inspected of the resistor 11 to be inspected are mutually coupled by magnetic flux. The electromotive force induced by the magnetic flux from the transmission coil 12 that is linked to the reception coil 13 is guided to the high-frequency signal amplitude measurement circuit 3 through the coaxial cable 6 as a reception signal.
[0022]
If there is a magnetic body between the transmission coil 12 and the reception coil 13, the magnetic flux interlinking from the transmission coil 12 to the reception coil 13 increases as compared with the case where there is no magnetic body between the coils. Become. If the exciting current to the transmission coil 12 is constant and the relative position between the end face electrode of the resistor to be inspected and the transmission / reception coil is constant within a range in which non-linearity due to magnetic saturation or the like does not occur in the coil or nickel plating layer, The thickness of the nickel plating layer in the end face electrode and the amplitude of the received high frequency signal are in a substantially proportional relationship.
[0023]
Therefore, if the correlation between the thickness of the nickel plating layer and the received high-frequency signal amplitude is measured in advance using a sample having a known nickel-plated layer thickness, it is determined from the received signal amplitude in the end face electrode of the resistor 11 to be inspected. The thickness of the nickel plating layer can be measured. Also, the quality of the nickel plating thickness can be determined and inspected based on the received high-frequency signal amplitude.
[0024]
Next, a detailed configuration of each part of the inspection apparatus according to the present embodiment will be described.
[0025]
<High-frequency signal generation circuit>
The upper limit of the frequency of the sine wave signal generated by the high-frequency signal generating circuit 2 is in the frequency range where nickel acts as a magnetic material, and is a frequency lower by about 10 times or more than the self-resonant frequency of the receiving coil 12 of the inspection head 1. It is necessary to be. On the other hand, the lower limit of the frequency of the sine wave signal is such that the voltage induced in the receiving coil 12 of the inspection head 1 is equal to or higher than the S / N ratio (signal to noise ratio) required for the high frequency signal amplitude measuring circuit 3 or other measuring equipment. It is a condition for performing the intended measurement that the frequency is higher than or equal to the frequency that can be received.
[0026]
The required S / N ratio is determined by the difference between the detected voltage difference ΔV when the resistor 11 to be inspected is inserted between the transmitting coil 12 and the receiving coil 13 and the thickness of the nickel plating layer. Determined by resolution.
[0027]
For example, if ΔV is 1 percent (1/100) when the thickness of the nickel plating layer is 10 μm and 1 μm is required as the resolution, the fluctuation due to noise is 1/100 × 1/10 = 1/1000 or less. That is, the S / N ratio must be 60 dB or more.
[0028]
When a magnetic material other than nickel plating and nickel is used as the resistor element, the frequency used is selected according to the characteristics of each magnetic material. For example, when the magnetic material has the characteristics shown in FIG. 2, even if the relative magnetic permeability of the magnetic material other than nickel is larger than the relative magnetic permeability of nickel in the low frequency region, the inspection method by the inspection apparatus according to the present invention. Thus, the thickness of the nickel layer can be inspected. In this case, the frequency in the frequency region A in FIG. 2 is used.
[0029]
On the other hand, the upper limit of the amplitude needs to be a range in which the transmission coil 12 and the reception coil 13 of the inspection head 1 and nickel do not cause magnetic saturation, and the lower limit of the amplitude is induced in the reception coil 13 of the inspection head 1. The condition is that the voltage can be received at an S / N ratio or higher required for the high-frequency signal amplitude measuring circuit 3 or other measuring equipment.
[0030]
The above conditions are necessary to maintain a substantially linearity between the thickness of the nickel layer and the received high-frequency signal amplitude after obtaining the necessary resolution.
[0031]
<High-frequency signal amplitude measurement circuit>
The condition that the high-frequency signal amplitude measurement circuit 3 should have is that the induced voltage amplitude of the receiving coil 13 can be received at a required S / N ratio or higher. In this embodiment, as will be described later, a digital sampling oscilloscope that can improve the S / N ratio by means of averaging (averaging) is used as the received signal amplitude measuring instrument.
[0032]
<Inspection head>
As described above, the transmission coil 12 and the reception coil 13 constituting the inspection head 1 are premised on that they do not cause self-resonance at the inspection frequency and do not undergo magnetic saturation. Therefore, conditions required for the inspection head 1 such as the positional relationship between the transmission coil 12 and the reception coil 13 and the resistor to be inspected will be described in detail.
[0033]
3 and 4 are diagrams for explaining the positional relationship between the transmission coil and the reception coil and the resistor to be inspected. FIG. 3 schematically shows a case where the coil and the resistor to be inspected have a desirable positional relationship. As shown in the figure, among the magnetic fluxes generated from the transmission coil 32, the magnetic flux 31 that reaches the reception coil 33 directly from the transmission coil 32 passes through the nickel layer 37 inside the end face electrode of the resistor 11 to be tested. The positional relationship in which the ratio of the magnetic fluxes 35 and 36 to be increased is maintained.
[0034]
If the positional relationship shown in FIG. 3 is maintained, the transmission coil 32 can concentrate the magnetic flux in the portion where the electrode of the resistor 11 to be inspected is inserted between the transmission coil 32 and the reception coil 33. Can effectively capture the magnetic flux that has passed through the nickel layer 37 of the end face electrode of the resistor 11 to be inspected.
[0035]
On the other hand, FIG. 4 schematically shows a positional relationship in which the inspection accuracy of the resistor to be inspected is low. As shown in the figure, the positional relationship in which the ratio of the direct magnetic flux between the transmitting coil 42 and the receiving coil 43 is larger than the ratio of the magnetic fluxes 45 and 46 passing through the nickel layer 37 inside the end face electrode of the resistor 11 to be tested. Then, the above-described ΔV becomes small. As a result, the required S / N ratio becomes so large that it cannot be realized in some cases. Further, the proportional relationship between the nickel plating thickness and the detection voltage does not hold.
[0036]
In FIGS. 3 and 4, white arrows attached to the transmission coils 32 and 42 and the reception coils 33 and 43 indicate the magnetic flux passage directions of the coils.
[0037]
FIG. 5 is a cross-sectional view showing in detail the inspection portion of the resistor 11 to be inspected. In the resistor 11 shown in the figure, a resistor 52 is laminated on a ceramic substrate 51, and nickel plating layers 55 and 56 and electrodes made of solder layers 53 and 54 are arranged so as to cover both ends thereof. It has a structure.
[0038]
When inspecting the thickness of the internal nickel plating layers 55 and 56 of the resistor 11, the inspection target portion is the nickel layer 56 b on the end surface of the resistor, and the nickel layers 56 a and 56 c on the upper and lower surfaces of the resistor If not, the magnetic flux for inspection needs to be concentrated on the end face of the resistor. The state at that time will be described with reference to FIGS.
[0039]
FIG. 6 is a perspective view showing the positional relationship between the transmission coil 62 and the reception coil 63 and the resistor 11 to be inspected inserted between these coils. 7 and 8 are cross-sectional views showing the position of the nickel layer with respect to the transmission coil and the reception coil (as viewed from the arrow BB ′ in FIG. 6). 7 and 8, the direction of the magnetic flux by the coil is from the back of the page to the front.
[0040]
In order to concentrate the magnetic flux from the transmission coil 62 on the end face nickel layer of the resistor to be inspected, as shown in FIG. 7, the position of the coil cross section 71 is determined so that the magnetic flux passes through the end face nickel layer 56b to be inspected. do. That is, it is necessary that the coil cross section 71 is applied to the end face nickel layer 56b to be inspected and not on the upper and lower surface nickel layers 56a and 56c (see FIG. 8) which are not desired to be affected by the inspection.
[0041]
Therefore, as shown in FIG. 8, when the coil cross section 81 passes the magnetic flux through the positions of both the end face nickel layer 56b to be inspected and the upper surface and lower surface nickel layers 56a and 56c that are not desired to affect the inspection, the upper surface and The ratio of the magnetic flux passing through the lower surface nickel layers 56a and 56c increases, and the thickness of the nickel layer only on the end face of the resistor cannot be inspected.
[0042]
In order to accurately inspect the nickel layer on the end face, the radius r of the coil cross section 71 is preferably smaller than the thickness T of the resistance substrate 51 in FIG. Further, by adjusting the distance d from the magnetic flux concentration portion (here, the central axis of the coil) to the end face nickel layer when there is no resistor 11 to be inspected between the transmission coil and the reception coil, the above-described detection voltage difference ΔV is obtained. Inspection is performed under the condition that the influence of the end face nickel layer is maximized.
[0043]
The above condition is also a condition that the positioning mechanisms 15a, 15b, and 15c shown in FIG. 1 should have, and when these conditions are satisfied, the relative position of the resistor 11 to be inspected with respect to the coils 62 and 63 is satisfied. Is kept constant.
[0044]
<Inspection head pattern>
In the inspection performed by the film inspection apparatus according to this embodiment, the thickness of the nickel layer of the resistor is measured using the magnetic flux between the transmission coil and the reception coil as a medium. Therefore, the supply pattern (inspection head pattern A16 in FIG. 1) that is a supply path of the high-frequency current to the transmission coil and the reception signal transmission pattern (inspection head pattern B17 in FIG. 1) on the reception coil side are directly electromagnetic. Coupling or the like causes measurement errors.
[0045]
In particular, when a high frequency is used, the inductance of the transmission coil and the reception coil cannot be increased so much due to the limitation of the self-resonance frequency. Accordingly, the self-inductance of the pattern relative to the coil and the mutual inductance of the pattern between transmission and reception cannot be ignored with respect to the inductance of the transmission coil and the reception coil.
[0046]
[First head pattern example]
FIG. 9 is an example of an inspection head pattern. FIG. 9A is a top view of the inspection head 1, FIG. 9B is a side view, and FIG. 9C is a bottom view. In FIG. 9, alternate long and short dash lines indicate the magnetic flux central axes of the transmission coil and the reception coil mounted at the transmission coil mounting position 111 and the reception coil mounting position 112, respectively. These coils are mounted on transmitting coil mounting pads 103 and 105 and receiving coil mounting pads 104 and 106 provided at mounting positions 111 and 112, respectively.
[0047]
Therefore, the inspection head pattern in the inspection head 1 shown in FIG. 9 has the following configuration when compared with the inspection head pattern A16 shown in FIG. That is, the inspection head pattern A16 includes a front pattern 93 that runs parallel to the magnetic flux center axis described above on the printed circuit board insulating layer 120, a transmission coil that is arranged at the mounting position 111, and a back pattern that runs parallel to the magnetic flux center axis. (Back ground pattern) 95.
[0048]
Note that one end of the front pattern 93 and the back pattern 95 is connected to the SMA connector 91 at the end of the printed circuit board for electrical connection with the above-described coaxial cable or the like. The front pattern 93 and the back pattern 95 are connected to each other through the via hole 101.
[0049]
Similarly, the inspection head pattern B17 includes a front pattern 94 that runs parallel to the magnetic flux center axis, a transmission coil disposed at the mounting position 112, and a back pattern that runs parallel to the magnetic flux center axis on the printed circuit board insulating layer 120. Back ground pattern) 96.
[0050]
In addition, one end of the front pattern 94 and the back pattern 96 is connected to the SMA connector 92 at the end of the printed circuit board for electrical connection with a coaxial cable or the like. The front pattern 94 and the back pattern 96 are connected to each other through the via hole 102.
[0051]
By configuring the inspection head pattern in this manner, the reciprocating patterns are magnetically coupled with each other at a distance as short as possible, and the magnetic flux generated from the patterns and the magnetic coupling between the patterns of the transmission coil 12 and the reception coil are reduced. Yes.
[0052]
[Second head pattern example]
10A and 10B show another example of the inspection head pattern. FIG. 10A is a top view of the inspection head 1 and FIG. 10B is a side view. What is characteristic of the inspection head 1 shown in FIG. 10 is that a supply pattern, which is a supply path of a high-frequency current, and a reception signal transmission pattern are formed only on the upper surface side of the printed board insulating layer 260.
[0053]
In FIG. 10, the alternate long and short dash lines are the magnetic flux central axes of the transmission coil and the reception coil that are respectively mounted at the transmission coil mounting position 211 and the reception coil mounting position 212. These coils are mounted on transmitting coil mounting pads 203 and 205 and receiving coil mounting pads 204 and 206 provided at mounting positions 211 and 212, respectively.
[0054]
In the inspection head shown in FIG. 10, the pattern corresponding to the inspection head pattern A16 in FIG. 1 includes a central signal pattern 231 that runs parallel to the magnetic flux central axis (indicated by a one-dot chain line) on the printed board insulating layer 260, and a mounting position. 211, and a surrounding ground pattern 235 that runs around the central signal pattern 231 in parallel with the magnetic flux central axis.
[0055]
Two resistors (same resistors) 221 and 222 are inserted into the surrounding ground pattern 235 in order to allow a return current to flow evenly. The resistance values of these resistors should be sufficiently larger than the impedance at the inspection frequency due to the self-inductance of the ground pattern. Specifically, since the impedance at the inspection frequency due to the self-inductance of the pattern is about several Ω or less at several tens of MHz, the necessary resistance value in this case is about several Ω to several tens of Ω.
[0056]
Similarly, the pattern corresponding to the inspection head pattern B17 of FIG. 1 includes a central signal pattern 232 that runs parallel to the magnetic flux center axis on the printed board insulating layer 260, a transmission coil disposed at the mounting position 212, and a magnetic flux center. A peripheral ground pattern 236 that runs so as to surround the central signal pattern 232 in parallel to the axis. Two resistors (same resistors) 223 and 224 are inserted in the surrounding ground pattern 236 in order to allow a return current to flow evenly.
[0057]
【Example】
Examples of the present invention will be described in detail below. Here, as a resistor to be inspected, a rectangular chip resistor having a size of 1.6 mm × 0.8 mm is to be inspected, and for the inspection, a transmission coil and a reception coil of the inspection head have an inductance of 100 nH to 1 μH, The one using a prismatic core having a size of about 2 mm × 1.25 mm and a permeability of 4 to 10 was employed.
[0058]
The interval between the transmission coil and the reception coil was 1.0 mm, and a signal having a frequency of 10 MHz and an amplitude of 10 dBm (measured value at the transmission end before the 10 dB attenuator) was used as the high-frequency current. Thus, by using a coil smaller than the resistor to be inspected as the transmission coil, the inspection accuracy can be increased by further improving ΔV.
[0059]
On the other hand, a digital sampling oscilloscope capable of improving the S / N ratio by averaging was used as a reception signal amplitude measuring device for the inspection head, and an S / N ratio of about 80 dB was obtained. As described above, when the thickness of the nickel plating layer is 10 μm and ΔV is 1 percent (1/100) and 1 μm is required as the resolution, the S / N ratio must be 60 dB or more. Therefore, in this inspection head, the ΔV is about 1 percent, and therefore the resolution is 0.1 μm when the S / N ratio is 80 dB.
[0060]
12-14 is a graph which shows the test result based on an Example. Among these, FIG. 12 shows the correlation between the electrode part nickel plating thickness of the resistor to be inspected (square chip resistor) obtained from the measurement data and the detected voltage. As is apparent from this graph, the magnetic field strength and the nickel plating thickness have a correlation.
[0061]
That is, for a plating thickness of 10 μm or less, the detection voltage and the plating thickness are approximately proportional as shown in FIG. 12, but when the plating thickness is larger than 10 μm, it is not shown in FIG. The plating thickness tends to increase exponentially as compared to. As described above, although the tendency varies depending on the range of the plating thickness, the thickness of the plating to be measured in the present invention is mainly about 2 μm or 3 μm. If the correlation becomes clear, the plating thickness can be measured sufficiently.
[0062]
FIG. 13 shows data of a plurality of samples, and it can be seen from this result that there is a significant difference in the detection voltage due to the plating thickness for “normal product”, “plated thin product”, and “defective product”. Therefore, it is possible to easily identify a non-defective product and a defective product based on the “good / bad boundary line” shown in FIG. The “plated thin product” includes defective products.
[0063]
FIG. 14 is a graph showing the variation (standard deviation) of the sample inspection results. According to the figure, it can be seen that there is a significant difference between “normal product”, “plated thin product”, and “defective product” in the detected voltage in the range of ± 3σ with respect to the average value (av).
[0064]
As described above, according to the present embodiment, it is not determined whether the nickel-plated thick portion in the electrode portion of the resistor is attracted to the magnet as in the prior art, but the magnetic flux from the transmitting coil is It can be grasped by a continuous numerical value of the received high-frequency signal amplitude passed through the inspection object and captured by the receiving coil. For this reason, by measuring the amplitude of the received signal, a magnetic layer placed in a very narrow area covered with nonmagnetic metal, such as a nickel plating layer under the solder layer of the end electrode of a chip resistor or the like. Nondestructive and highly accurate inspection of body layer thickness.
[0065]
Further, since the obtained data is a continuous amount, it is possible to know the distribution of nickel plating thickness in the lot for a plurality of samples in the same lot, and it is possible to manage the plating thickness in lot units.
[0066]
Further, by using an alternating magnetic field for measuring the nickel thickness, even if the product to be inspected is magnetized, the inspection can be performed without error.
[0067]
Furthermore, since only the resistors to be inspected are inserted between the transmitting coil and the receiving coil at the time of inspection, 100% inspection can be performed in a short time. Even so, the inspected product can be provided to the customer as it is.
[0068]
In addition, since the correlation between magnetic field strength and plating thickness is strong, the reliability of the measurement results is high, and based on such results, the thickness of the nickel layer of the end electrode of the resistor is guaranteed in the product specifications. Can do.
[0069]
<Modification>
The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit of the invention.
[0070]
In the embodiment described above, the transmission coil and the reception coil are provided independently, but these may be a single coil using a common core. For example, as shown in FIG. 11, in the common core 301 having a gap (gap) 310, a coil is wound around one end facing the gap 310 to form the transmission coil 302, and similarly, at the other end facing the gap 310. By forming a receiving coil 303 by winding the coil, a transmission / reception integrated coil is obtained.
[0071]
At the time of measurement, the resistor 350 to be inspected is inserted into the gap 310, and a closed magnetic circuit is formed through the nickel layer of the resistor 350 and the common core 301. Note that the positional relationship between the resistor 350 and the cross section of the coil at the time of measuring the nickel layer of the resistor 350 is the same as those in the above-described embodiment.
[0072]
As described above, a common core having a certain gap is adopted as the transmission / reception coil, and the formation of the closed magnetic path improves the transmission efficiency of the magnetic flux from the transmission coil to the reception coil. Therefore, ΔV can be increased. At the same time, it is possible to improve the S / N ratio against electromagnetic noise around the inspection head.
[0073]
【The invention's effect】
As described above, according to the present invention, the thickness of the magnetic layer on the resistor end face can be inspected nondestructively and with high accuracy.
[0074]
In addition, according to the present invention, all the products can be inspected in a short time, and there is no product damage accompanying the measurement, so that the inspected product can be provided to the customer as it is.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a film inspection apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing characteristics of a magnetic material.
FIG. 3 is a diagram for explaining a desirable positional relationship between a transmission coil and a reception coil and a resistor to be inspected.
FIG. 4 is a diagram for explaining a positional relationship in which inspection accuracy is lowered in a transmission coil, a reception coil, and a resistor to be inspected.
FIG. 5 is a cross-sectional view showing in detail an inspection portion of a resistor to be inspected.
FIG. 6 is a perspective view showing a positional relationship between a transmitting coil, a receiving coil, and a resistor to be inspected inserted between these coils.
FIG. 7 is a cross-sectional view showing an appropriate position of a nickel layer with respect to a transmission coil and a reception coil.
FIG. 8 is a cross-sectional view showing a position where a measurement error occurs in a nickel layer for a transmission coil and a reception coil.
FIG. 9 is a diagram illustrating an example of an inspection head pattern.
FIG. 10 is a diagram showing another example of an inspection head pattern.
FIG. 11 is a diagram showing a structure example of a single coil using a common core.
FIG. 12 is a diagram showing the correlation between the electrode part nickel plating thickness of the resistor to be inspected and the detection voltage obtained from the measurement data according to the example.
FIG. 13 is a diagram showing data of a plurality of samples.
FIG. 14 is a graph showing the variation in the inspection result of the sample.
FIG. 15 is a diagram showing a square chip resistor and a cross-sectional structure when mounted.
[Explanation of symbols]
1 Inspection head
2 High-frequency signal generation circuit
3 High frequency signal amplitude measurement circuit
4 Coaxial cable
5 Attenuator
11 Resistor to be tested
12, 32, 42, 62 Transmitting coil
12a, 13b core
13, 33, 43, 63 Receiver coil
15a, 15b, 15c Positioning mechanism
16 Inspection head pattern A
17 Inspection head pattern B
18 End face electrode
37 Nickel layer
51 Ceramic substrate
52 resistors
53, 54 Solder layer
55,56 Nickel plating layer
103,105 Transmitting coil mounting pad
104,106 Receiver coil mounting pad
111,112 mounting position
120 Printed circuit board insulation layer

Claims (3)

An electronic part electrode film thickness inspection apparatus for inspecting the film thickness of a coating film constituting an electrode of an electronic part ,
A transmitting coil and a receiving coil, each of which is composed of a finite-length solenoid and spaced apart by a predetermined distance;
A high-frequency signal generating circuit for generating an alternating magnetic field between the transmitting coil and the receiving coil;
A high-frequency signal amplitude measuring circuit for measuring an amplitude of a voltage induced in the receiving coil;
A positioning mechanism for placing the electronic component between the transmission coil and the reception coil ;
The electrode of the electronic component includes a magnetic metal layer made of a magnetic material,
By the positioning mechanism, the transmitting coil and the receiving coil are arranged in a direction in which the central axis of the solenoid constituting the transmitting coil and the receiving coil is substantially perpendicular to the thickness direction of the magnetic metal layer. Arranging the electronic component so that a part of the magnetic metal layer to be inspected is located between the coil and the coil,
An electrode film thickness inspection apparatus for an electronic component, wherein a defect in the film thickness of the magnetic metal layer is identified from the amplitude of the voltage measured by the high frequency signal amplitude measurement circuit . Wherein the transmitting coil and the conductive pattern connecting said high-frequency signal generating circuit, and a conductive pattern connecting said and the receiving coil RF signal amplitude measurement circuit, the circuit board so runs parallel to the central axis of the magnetic flux of the alternating magnetic field The electrode thickness inspection apparatus for an electronic component according to claim 1, wherein the device is formed on the electrode . An electronic component electrode film thickness inspection method for inspecting a film thickness of a coating film constituting an electrode of an electronic component ,
The electrode is composed of a magnetic metal layer having magnetism and a nonmagnetic metal layer covering the magnetic metal layer,
The transmission coil and the reception coil are arranged at a predetermined distance from each other in a direction in which the central axis of the finite-length solenoid constituting the transmission coil and the reception coil that generates the alternating magnetic field is substantially perpendicular to the thickness direction of the magnetic metal layer. The electronic component is arranged so that a part of the magnetic metal layer to be inspected is located between the transmitting coil and the receiving coil,
An electrode thickness inspection method for an electronic component, wherein a defect in the thickness of the magnetic metal layer is identified from an amplitude of a voltage induced in the receiving coil .

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