JP5832200B2 - Apparatus and method for acquiring defect analysis image of wiring board using X-ray - Google Patents

Description

  The present invention relates to failure analysis of a wiring board, and more particularly to failure analysis using a probe and an X-ray.

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

  If the printed wiring board is defective as a result of the inspection, the defective portion is corrected if it can be corrected, and discarded if it cannot be corrected. Even if the correction is impossible, the failure is analyzed and fed back to the manufacturing process.

  When a printed wiring board is inspected using a printed wiring board inspection device that conducts an electrical test, if the circuit in the printed wiring board is disconnected, continuity failure (disconnection failure) occurs, and other circuits are short-circuited. If so, the failure content such as insulation failure (short circuit failure) is reported. However, although it is possible to identify which circuit on the printed wiring board has a defect, it is often difficult to identify at which position in the circuit the defect has occurred.

  As a conventional method for inspecting a printed wiring board, for example, a movable probe type inspection device or a device that automates a digital multimeter can be considered.

  When using a digital multimeter, two probes are brought into contact with the measurement object, and the measured value is read. Similarly, the movable probe type inspection apparatus performs measurement by bringing a probe into contact with an inspection point on a printed wiring board to be measured. However, since many inspection points exist on the printed wiring board, it takes a long time to manually measure the inspection points. Therefore, the probe is generally moved to the inspection points automatically.

  The movable probe type inspection apparatus requires a means (such as a motor) for moving the probe, and also requires an inspection program including data describing where the probe is moved.

When measuring using a probe, the resistance value between probes is calculated | required from an electric current and a measurement voltage by passing a constant current between probes and measuring the voltage between probes.
In the case of insulation inspection, the probe is brought into contact with an inspection point on a separate circuit, a constant voltage is applied between the probes, and the leakage current between the probes is measured. A value is determined.

  Such a conventionally known method is effective when it is desired to obtain an accurate resistance value, but there is a problem that it takes time to measure a wiring board having tens of thousands or more inspection points.

  As another inspection method, a dedicated jig method and a universal jig method are known as jig-type inspection apparatuses.

  In the dedicated jig method, a probe (pin) that can contact all the inspection points on the printed wiring board is set up. For example, if there are 2000 inspection points, 2000 pins are set up and contacted with both sides of the printed wiring board. Inspect the wiring board electrically. In the universal jig method, a probe is not set up at each inspection point, but a probe is set up on a lattice. Electrical inspection is performed by bringing pins arranged on these grids into contact with both surfaces of the wiring board. The dedicated jig method needs to manufacture a jig for each type of substrate, while the universal jig method can be applied to many types of substrates by manufacturing a mask sheet. However, there is a disadvantage that a large number of pins of tens of thousands to hundreds of thousands are required. In any of the jig methods, electrical inspection is performed by bringing a probe head having pins like a sword mountain into contact with both sides of a printed wiring board. Although these jig methods have a short inspection time, they are suitable for mass-produced products because they require jig manufacturing costs and jig storage locations. However, these jig methods are disadvantageous in the case of many kinds and small lots. is there. In contrast to the jig type, the movable probe type has a feature that inspection time is required because the number of probes is small.

  In addition, it is conventionally known to use an X-ray inspection as an inspection for a defective portion.

  The X-ray inspection is not an electrical inspection but an inspection method for judging by comparing non-defective image data such as design data with an image captured by a camera. In the case of a wiring board, many are formed from a plurality of layers, and there are also multilayer boards having 50 or more layers. Therefore, it is time disadvantageous to perform the multilayer wiring board by X-ray inspection.

  In order to accurately grasp and analyze the state of the defective part, the state of the defective part is appropriately obtained by rendering (3DCG) an image obtained by photographing the part considered to be defective from various directions into a stereoscopic image. Can be judged.

However, it takes more time to shoot from various directions, and more time is required for rendering processing. For this reason, analysis in which all the circuits are converted into 3D images is not realistic.
As described above, an inspection apparatus using a three-dimensional image is desirable, but there is a problem that it takes time to perform arithmetic processing compared to a two-dimensional image.

JP-A-10-19807

  The present invention solves the above-mentioned problems, and provides an apparatus and a method capable of performing a failure analysis of a wiring board with high accuracy by specifying a defective portion of the wiring board quickly and accurately and properly grasping the state thereof. The purpose is to do.

In order to solve the above problem, according to one feature of the present invention, a defect is detected from a plurality of circuit parts by inspecting a wiring board having a plurality of circuit parts that can be independently inspected using a probe. A defective circuit detecting means for detecting a circuit portion including a location;
X-ray irradiation means for irradiating the circuit portion including the defective portion with X-rays based on the circuit information of the wiring board;
X-ray characterized in that it comprises image acquisition means for specifying the defective portion in the circuit portion through X-ray irradiation by the X-ray irradiation means and acquiring an X-ray image of the defective portion. An apparatus for acquiring an image for wiring board failure analysis is provided.

  In this case, the image acquisition means irradiates X-rays along the circuit portion including the defective portion of the wiring board, specifies the defective portion, and obtains X-ray image data of the defective portion.

  In this case, for example, when a circuit portion including a defective portion is between specific probes, the specific probe is specified based on design information and the like and the circuit portion to be irradiated with X-rays is specified. To do. Then, a starting point for performing X-ray scanning in the specified circuit portion is determined, and X-ray scanning is started along the circuit portion. If a defective part is found during scanning, the scanning is stopped and information is collected. Typically, an image of a defective part is acquired as one used for defect analysis.

  The image can be used both visually and for data analysis.

  Further, it is desirable that the image acquisition means acquires a three-dimensional CT image of the defective portion in order to perform analysis after specifying the defective portion of the wiring board.

Further, according to another feature of the present invention, a circuit portion including a defective portion from the plurality of circuit portions by inspecting a wiring board having a plurality of circuit portions that can be inspected independently using a probe. Detecting the stage,
Irradiating the circuit portion including the defective portion with X-rays based on the circuit information of the wiring board;
Identifying the defective location via X-ray irradiation to the circuit portion including the defective location;
A method for acquiring an image for analyzing a wiring board defect, comprising: acquiring an X-ray image of the defective portion.

  X-ray image data can be obtained by irradiating X-rays along the circuit portion including the defective portion of the wiring board.

  Further, after specifying the defective portion of the wiring board, a three-dimensional CT image of the defective portion may be acquired through X-ray irradiation in order to perform defect analysis.

  ADVANTAGE OF THE INVENTION According to this invention, the defect location of a wiring board can be grasped | ascertained rapidly and correctly, and the condition of the defect of a power distribution board can be analyzed with sufficient precision. As a result, an appropriate response according to the content of the defect, for example, a design change, repair, a processing procedure, or a change of processing work content can be performed.

It is explanatory drawing of the test | inspection of the disconnection in a probe test | inspection apparatus. It is explanatory drawing of the test | inspection of the short circuit in a probe test | inspection apparatus. It is a schematic block diagram of the X-ray inspection apparatus of the printed wiring board by one embodiment of this invention. FIG. 3 is a plan view illustrating a non-defective printed wiring board (FIG. 2A) and a defective printed wiring board (FIG. 2B) according to an embodiment of the present invention. It is a figure explaining the content of the error file of a printed wiring board inspection apparatus. It is a figure which shows a X, Y, Z coordinate axis. It is a flowchart of the defect analysis method of the printed wiring board by one embodiment of this invention. It is an example of the two-dimensional CT image of the location with the possibility of the defective location image | photographed with the X-ray inspection apparatus. It is an example of CT image after the 3D rendering process of the part with the possibility of the defective part image | photographed with the X-ray inspection apparatus. It is an example of CT image after the 3D rendering process of the part with the possibility of the defective part image | photographed with the X-ray inspection apparatus. FIG. 11A is an example of a two-dimensional CT image (FIG. 11A) and an image after three-dimensional rendering processing (FIG. 11B) of a portion having a possibility of a defective portion imaged by an X-ray inspection apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  The invention of the present application is typically executed in the following procedure. In the following examples, the present invention is applied to a printed wiring board.

  The probe device of the present invention includes an inspection data input unit that reads inspection data of a printed wiring board. This inspection data is usually prepared in advance at the time of design, and is created from the viewpoint of the inspection work procedure of how to inspect the entire circuit. Furthermore, the apparatus according to the present invention is an error input unit for reading error information data files created based on inspection results obtained using a probe output from a probe inspection apparatus, that is, information on circuit portions including defective portions. It has. The information including the defective portion of the error input section can be matched with the relative position of the read inspection data and the printed wiring board by the position correcting means.

Then, the X-ray inspection apparatus irradiates the printed wiring board with X-rays so that an X-ray image is obtained along the circuit portion including the defective portion output by the probe inspection apparatus from the inspection data of the printed wiring board. While moving, X-ray imaging. The defective position of the printed wiring board is specified by comparing the obtained image data with the design information of the printed wiring board. This operation is usually performed by obtaining a two-dimensional image, but in order to perform a more accurate analysis, a three-dimensional image is created by three-dimensional X-ray CT for the specified defective portion, and the failure analysis is performed.
An example in the case of inspection using the movable probe method and the jig method will be described below.

  The movable probe type inspection device makes a measurement between a pair of probes by bringing a probe into contact with a measurement target (inspection point on a printed wiring board). However, when there are many inspection points on the printed wiring board, it takes time to perform manual measurement, so the inspection probe is automatically moved to the inspection point.

  The movable probe type inspection apparatus requires a moving means such as a motor for moving the probe, and also requires an inspection program having data describing where to move the probe.

In this case, there are generally two types of measurement methods. The first method is resistance measurement using Ohm's law. In the case of a continuity test for inspecting whether a circuit is disconnected, a probe is brought into contact with an inspection point on the circuit, a constant current of about 10 mA is usually passed between the probes, and a voltage between the probes is measured. Thereby, the resistance value between probes can be calculated | required from an electric current and a measurement voltage.
In the case of an insulation test for checking whether the circuit is short-circuited, a probe is brought into contact with a test point on another circuit, a constant voltage of about 100 V is applied between the probes, and a leakage current between the probes is measured. The resistance value between the probes can be obtained from the constant voltage and the measured leakage current.

  The above measurement is effective when it is desired to measure an accurate resistance value, but there is a problem that it takes too much time to measure a large number of inspection points. For this reason, instead of measuring an accurate resistance value, it is possible to determine whether there is a disconnection or a short circuit, and a high-speed inspection is required.

  In high-speed inspection, the resistance value is not specified, and it is common to determine pass / fail by comparing the good product value with the measured value. As a typical high-speed inspection method, there is an inspection method based on capacitance measurement. (See JP-A-53-10863). In the (electrostatic) capacity method, the electrostatic capacity of each circuit constituting the printed wiring board is measured. The capacitance can be expressed by the following formula.

C = ε · S / d where ε: dielectric constant, S: opposing conductor area, d: distance Here, a metallic plate serving as a reference is used outside the substrate to calculate the area of the opposing conductor. Or use the inner layer plane (power supply net or GND net) of the board. From these pieces of information, the capacitance of each circuit (inspection point) can be obtained. In the case of the capacitance method measurement, it is necessary to know the capacitance of a non-defective substrate. By comparing the capacitance of the non-defective substrate with the capacitance (measured value) of the substrate to be inspected, the capacitance The disconnection and short circuit can be found by increasing and decreasing. For example, as shown in FIG. 1B, when the circuit portion is disconnected, the facing area is reduced, so that the measured value is reduced compared to the case where there is no disconnection in FIG.

  Further, when the circuit portion is short-circuited as shown in FIG. 2B, the facing area increases, so that the measured value is increased as compared to the case where there is no short-circuit in FIG.

  However, in the case of this type of measurement method, disconnection and short circuit can be detected in both the resistance value measurement and the capacitance measurement, but the circuit part to be inspected including the defective part can be identified, but the circuit part has a defect. The exact location of the location cannot be specified.

    Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  Referring to FIG. 3, a schematic diagram of an X-ray inspection apparatus for performing defect analysis of a printed wiring board according to an embodiment of the present invention is shown. The printed wiring board X-ray apparatus according to the present embodiment includes, for example, an X-ray source 1, an X-ray fluoroscopic camera 2, and a stage 3.

  An X-ray fluoroscopic camera 2 that captures a projection image of the printed wiring board 4 on the stage that is disposed opposite to the X-ray source 1 is connected to the printed wiring board 4 fixed on the stage from the X-ray source 1. The X-ray cone beam 5 is transmitted so that the X-ray fluoroscopic camera 2 can take an image. In order to detect minute defects on the printed wiring board, it is desirable to use a microfocus X-ray source having a small focal diameter that can obtain a clear image at a high magnification as the X-ray source 1. Further, when the height of the stage 3 (Z-axis direction) is changed, the distance between the X-ray source 1 and the printed wiring board 4 is changed, and the image enlargement ratio of the printed wiring board 4 can be arbitrarily changed. is there.

  Before performing the failure analysis using the X-ray inspection apparatus for the printed wiring board 4, the printed wiring board is inspected electrically using the probe as described above using the probe inspection apparatus.

  As a result of inspection with a printed wiring board inspection apparatus using a probe, if an inspection result is reported that there is a circuit portion including a defective portion on the printed wiring board 4, a defect such as disconnection or short circuit is An error file including the circuit portion including the type and defective portion as information is formed.

  As described above, as a general defect of a printed wiring board, there are a conduction failure (disconnection failure) in which a circuit in the printed wiring board is disconnected, and an insulation failure (short circuit failure) short-circuited with other circuit portions. can give. The error file contains the inspection point number information indicating which inspection points of the circuit were defective in the case of poor conduction as well as the types of poor conduction and insulation failure. Net number information describing which circuit and which circuit has a poor insulation may be included. Although it is possible to specify a circuit portion having a defective portion by the inspection, it is difficult to specify the exact position of the defective portion in the circuit portion. For example, the first circuit portion 6 is disconnected as shown in FIG. 4B with respect to a good printed wiring board as shown in FIG. 4A, and the second circuit portion 7 and the third circuit portion are disconnected. When 8 is short-circuited, there is a disconnection between points 6 a and 6 b in the first circuit portion 6, and there is a short-circuit between the second circuit portion 7 and the third circuit portion 8. Is shown.

  When a specific circuit part includes a defective part, an error file having contents as shown in FIG. 5 is created. In the case of the embodiment, it is shown that there is a disconnection between the point 6a and the point 6b in the first circuit portion 6 and there is a short circuit between the second circuit portion 7 and the third circuit portion 8. ing.

  The printed wiring board 4 including a circuit portion having a defective portion by the probe inspection acquires information for failure analysis using an X-ray apparatus. In this case, first, inspection data including an error file output from the probe inspection apparatus and trace information of the printed wiring board is read into the X-ray apparatus of the printed wiring board. The trace information is a description of the position and thickness of all the circuits on the printed wiring board with coordinates, line width, etc. for each layer. It is used for drawing and comparing with an X-ray image.

  The printed wiring board 4 having a defect is fixed to the stage 3 in the X-ray inspection apparatus. As shown in FIG. 6, the stage 3 has a structure that can be translated in the X, Y, and Z axis directions and can be rotated about the Z axis as a rotation axis. Servo technology or the like can be used to perform parallel movement in the X, Y, and Z axis directions and rotation about the Z axis as a rotation axis.

  First, in order to match the relative position between the inspection data and the printed wiring board, an arbitrary number of alignment recognition marks (alignment marks) set on the printed wiring board are acquired by the camera, and the XY position is obtained. to correct. When the number of alignment marks is one, it is not possible to perform correction when the fixing angle of the printed wiring board 4 changes or the printed wiring board 4 expands and contracts.

As shown in FIG. 7, in the present invention, only the circuit portion including the defective portion on the printed wiring board is inspected by using the X-ray inspection apparatus using the error file output from the probe inspection apparatus. In this case, first, as described above, the X-ray inspection apparatus 1 reads the error file information obtained by the inspection by the probe inspection apparatus (step 1). X-ray while moving the stage 3 in the XY direction toward another inspection point so that an image can be acquired by the X-ray fluoroscopic camera 2 along the trace information of the printed wiring board from an inspection point having a circuit portion including a defective portion. An image is acquired (step 2). Next, an image comparison between the X-ray image and the printed wiring board pattern data is performed (step 3). While repeating the above steps, the defective position of the circuit on the printed wiring board is determined (step 4). For example, if it is determined that the defect portion shown in FIG. 3B is included, acquisition of an X-ray image is started from the point 6 a of the first circuit portion 6, and the point 6 a along the circuit of the first circuit portion 6 is started. The image is taken from point 6b toward point 6b (step 5).
In addition, by taking an image, it is possible to determine a defective portion based on evaluation of an acquired image or comparison with a reference image, but it is also possible to directly determine by visual observation of a display image.

  In this case, the X-ray inspection apparatus first obtains images as shown in FIGS. 8A, 8B, and 8C. As a result of comparing the X-ray image and the non-defective image data obtained from the wiring information of the printed wiring board, if it is determined that there is a possibility of failure, the movement of the stage 3 is stopped and the three-dimensional X-ray CT is performed. I do. In order to perform three-dimensional X-ray CT, the stage 3 is moved XY so that the defective part becomes the center of the rotation axis, the stage 3 is rotated at a minute angle interval, and the X-ray fluoroscopic camera 2 captures each angular step. The recorded image is recorded on a recording medium such as an HDD, and the recorded image image is reconstructed by an analysis device to obtain a three-dimensional image. FIG. 8, FIG. 10 (A), FIG. 10 (B) and FIG. 11 show examples of high-accuracy three-dimensional X-ray images obtained in this way. Note that the image shown in FIG. 11A is a two-dimensional image, and the image shown in FIG. 10B is an image subjected to 3D rendering.

  The present invention can be used for failure analysis with high accuracy of a wiring board.

1 ... X-ray source 1
2. X-ray fluoroscope 3 ... Stage 4 ... Printed wiring board 5 ... X-ray cone beam 6 ... First circuit portion 7 ... Second circuit portion 8 ... Third circuit portion

Claims (6)

A defective circuit detection means for detecting a circuit part including a defective part from the plurality of circuit parts by inspecting a wiring board having a plurality of circuit parts that can be independently inspected using a probe;
X-ray irradiation means for irradiating the circuit portion including the defective portion with X-rays based on the circuit information of the wiring board;
Through the X-ray irradiation by the X-ray irradiating means, the defective portion is identified using error information indicating the position of the defective portion in the circuit portion including the defective portion , and an X-ray image of the defective portion is acquired. An image acquisition device for analyzing a wiring board failure using X-rays, characterized by comprising: an image acquisition means.   The image acquisition means irradiates X-rays along a circuit portion including the defective portion of the wiring board, specifies the defective portion, and obtains X-ray image data of the defective portion. The apparatus according to claim 1, wherein the apparatus is characterized.   The said image acquisition means acquires the three-dimensional CT image of this defect location, in order to analyze after specifying the said failure location of the said wiring board, The said 1st aspect is characterized by the above-mentioned. Equipment. Detecting a circuit part including a defective portion from the plurality of circuit parts by inspecting a wiring board having a plurality of circuit parts that can be independently inspected using a probe; and
Irradiating a circuit portion including the defective portion with X-rays based on circuit information of the wiring board; and error information indicating a position of the defective portion through irradiation with X-rays to the circuit portion including the defective portion. Using to identify the defective portion ;
A method for obtaining an image for analyzing a wiring board defect, comprising: obtaining an X-ray image of the defective portion.   5. The method for obtaining an image for defect analysis of a wiring board according to claim 4, wherein X-ray image data is obtained by irradiating X-rays along a circuit portion including a defective portion of the wiring board.   6. The wiring board according to claim 5, wherein after identifying the defective portion of the wiring board, a three-dimensional CT image of the defective portion is acquired through X-ray irradiation in order to perform defect analysis. A method for acquiring an image for defect analysis.