JP2008045883A - Inspection method and inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the inside state of the solder more readily. <P>SOLUTION: In an imaging part 86a of a main control part 86, a substrate onto which solder is applied is irradiated with infrared rays having prescribed intensity by an illumination device 2 and a dimming device 3, and the substrate is imaged by an imaging device 4. A detection part 86b detects the section state of the solder, based on an intensity distribution of infrared light reflected by the substrate in image data based on the imaging device 4. As a result, since the inside state of the solder can be detected without the use of X-rays as in conventional cases, cost reduction, device miniaturization or the like becomes possible, and as a result, the inside state of the solder can be detected more readily. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inspection method and an inspection apparatus for inspecting the state of cream solder applied on a substrate.

  Conventionally, in order to stabilize the quality of a substrate on which electronic components are mounted, an inspection apparatus for inspecting the state of applied cream solder has been developed.

  For example, Patent Document 1 discloses a method of inspecting cream solder applied between a semiconductor device and a substrate on a substrate on which the semiconductor device is mounted. In this method, the substrate is irradiated with infrared light, the reflected light reflected by the surface of the cream solder is imaged by a camera, and the image signal data is AD converted to obtain a grayscale image signal. The state of cream solder is detected by measuring the area composed of pixels larger than a preset density value.

  Patent Document 2 discloses a method for inspecting the state of cream solder formed on a substrate based on an X-ray transmission image. In this method, the substrate is irradiated with X-rays, an X-ray transmission image transmitted through the substrate is detected, and the state of the cream solder is detected based on the X-ray transmission image.

JP 9-89536 A JP 2002-280727 A

  However, in the method of Patent Document 1, since the state of the cream solder is detected based on the reflected light from the cream solder surface, the state of the cream solder surface can be inspected, but the state inside the cream solder is inspected. I could not. Moreover, although the method of patent document 2 can test | inspect the state inside cream solder, since X-rays were used, there existed problems, such as the price of an apparatus being high, and the apparatus being large by arrangement | positioning of an X-ray circuit breaker.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide an inspection method and an inspection apparatus that can more easily detect the state of cream solder.

  In order to solve the above-described problems, an inspection method according to the present invention includes a step of irradiating a substrate coated with cream solder with infrared light having a predetermined intensity, and a substrate irradiated with infrared light. And a step of detecting a cross-sectional shape of the cream solder along a surface separated from the substrate based on an image representing an intensity distribution of infrared light reflected from the substrate.

  The inspection method may further include a step of determining the state of the cream solder based on the cross-sectional area of the cream solder.

  Further, the inspection apparatus according to the present invention includes an illumination unit that irradiates infrared light having a predetermined intensity on a substrate coated with cream solder, an imaging unit that images the substrate irradiated with infrared light, and a substrate. And detecting means for detecting a cross-sectional shape of the cream solder along a surface separated from the substrate based on an image representing an intensity distribution of infrared light reflected from the substrate.

  According to the present invention, a substrate coated with cream solder is irradiated with infrared light having a predetermined intensity, the substrate is imaged, and the cross-sectional shape of the cream solder is reflected from the reflected light from the electrode pad in the captured image. By detecting this, it becomes possible to detect the internal state of the cream solder without using X-rays as in the prior art, which makes it possible to reduce costs, reduce the size of the device, etc., and as a result, more easily The internal state of the cream solder can be detected.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Configuration of inspection equipment]
As shown in FIG. 1, the inspection device 1 according to the present embodiment includes an illumination device 2, a light control device 3, an imaging device 4, a drive device 5, a display device 6, an input device 7, and a control. Device 8.

  The illuminating device 2 is composed of an illuminating device that outputs infrared light, such as an infrared LED (Light Emitting Diode), and is driven by a voltage (hereinafter referred to as “supply voltage”) supplied from the dimmer 3. For example, as shown in FIG. 2, the infrared LED 2 a constituting the illumination device 2 is installed above the substrate P so that the optical axis has 10 degrees ± 6 degrees with respect to an axis perpendicular to the main surface of the substrate P. The When a pair of infrared LEDs 2a are provided as shown in FIG. 2, they may be provided symmetrically with respect to the vertical axis. Such an illuminating device 2 can output infrared light having a wavelength of 875 ± 30 nm. In addition, as shown in FIG. 2, you may make it the illuminating device 2 provide visible light LED2b which irradiates not only infrared LED2a but visible light.

  The light control device 3 is a device that supplies a supply voltage to the lighting device 2. Here, the supply voltage is adjusted based on an instruction from the control device 8.

  The imaging device 4 is composed of a CCD (Charge Coupled Device) camera or the like, and has wavelength sensitivity in the infrared region. The imaging device 4 performs imaging based on an instruction from the control device 8. Such an imaging device 4 may be provided above the substrate P as shown in FIG.

  The drive device 5 includes a motor, an actuator, and the like provided in a transfer device (not shown) for realizing the carry-in and carry-out of the substrate, a moving device (not shown) that moves the imaging device 4 above the substrate, and the like. Is done. Such a driving device 5 is driven based on an instruction from the control device 8.

  The display device 6 includes a known display device such as a CRT (Cathode Ray Tube), an LCD (Liquid Crystal Display), or an FED (Field Emission Display). Such a display device 6 displays various information based on instructions from the control device 8.

  The input device 7 includes a device that detects input of information from the outside, such as a keyboard, a mouse, a pointing device, a button, and a touch panel. Information detected by the input device 7 is input to the control device 8.

  The control device 8 is a device for controlling the overall operation of the inspection apparatus 1, and includes an illumination control unit 81, an image processing unit 82, a drive control unit 83, an I / F unit 84, a storage unit 85, and a main control unit 86. Is provided.

  The illumination control unit 81 is a functional unit that sets the light intensity of infrared light emitted from the illumination device 2 based on an instruction from the main control unit 86. The set intensity is output to the light control device 3. The light control device 3 adjusts the supply voltage according to the intensity set by the illumination control unit 81. Thereby, infrared light of a predetermined intensity is output from the lighting device 2.

  The image processing unit 82 issues an imaging instruction to the imaging device 4 based on an instruction from the main control unit 86, and performs A / D conversion or the like on the captured image captured by the imaging device 4 based on the instruction. A functional unit that performs image processing and outputs image data. Thereby, for example, image data in which the light intensity of the reflected light is expressed in shades as shown in FIG. 3 is generated.

  The drive control unit 83 is a functional unit that generates and outputs a drive signal for driving the drive device 5 based on an instruction from the main control unit 86.

  The I / F unit 84 displays various information on the display device 6 based on instructions from the main control unit 86. Further, various information detected by the input device 7 is sent to the main control unit 86.

  The storage unit 85 is a functional unit that stores various types of information such as image data based on instructions from the main control unit 86.

  The main control unit 86 gives an instruction to the illumination control unit 81, the image processing unit 82, the drive control unit 83, and the I / F unit 84 based on an instruction from the outside such as a user or a host computer. This is a functional unit that realizes an inspection operation for inspecting the state of cream solder printed on the substrate. Such a main control unit 86 is calculated by an imaging unit 86a that images a substrate coated with cream solder, and a detection unit 86b that detects a sectional shape of the cream solder from the image data and calculates a sectional area thereof. And a determination unit 86c for determining the quality of the cream solder from the cross-sectional area of the cream solder.

  Such a control device 8 includes various kinds of arithmetic devices such as a CPU, a memory, a storage device such as an HDD (Hard Disc Drive), a communication line such as the Internet, a LAN (Local Area Network), and a WAN (Wide Area Network). The computer includes an I / F device that transmits and receives information, and a program installed in the computer. That is, the hardware device and software cooperate to control the above hardware resources by a program, and the above-described illumination control unit 81, image processing unit 82, drive control unit 83, I / F unit 84, storage unit. 85, the main control unit 86 is realized. Note that the program may be provided in a state of being recorded on a recording medium such as a flexible disk, a CD-ROM, a DVD-ROM, or a memory card.

[Operating principle]
Next, the operation principle of the inspection apparatus 1 according to the present embodiment will be described.

  Cream solder is composed of solder powder and flux. When infrared light is irradiated onto a substrate coated with such cream solder, the infrared light passes through the flux in the cream solder and cream solder. Infrared light that travels inside and reaches the electrode pad made of a metal layer is reflected by the electrode pad. This reflected light is transmitted again through the flux in the cream solder, and the infrared light emitted to the outside of the cream solder is detected by the imaging device 4.

  In this way, when passing through the cream solder, infrared light is scattered by the solder powder or attenuated by the flux. Therefore, the thicker the cream solder, the more the infrared light passes through the cream solder and the more components that scatter or attenuate, resulting in a weaker light intensity of the reflected light.

  3 (a) to 3 (c) irradiate a substrate having a screen thickness of 50 μm, 70 μm, and 100 μm when the cream solder is printed by screen printing with infrared light set to a predetermined intensity, respectively. This is an image when the substrate is imaged by the imaging device 4. In FIG. 3A to FIG. 3C, the brightness of each pixel represents the light intensity of the infrared light reflected on the substrate surface. The light intensity is whiter as the light intensity is higher and black as the light intensity is lower. It is displayed.

  As shown in FIGS. 3A to 3C, the silicon constituting the substrate is displayed in black because almost no reflected light is generated because infrared light is transmitted. The electrode pad made of a metal layer formed on the substrate is displayed in white because it reflects infrared light.

  When the cream solder applied on the electrode pad is thick (70 μm, 100 μm) as shown in FIGS. 3B and 3C, the light intensity of the reflected light is weakened. Displayed in black. On the other hand, when the cream solder is thin as shown in FIG. 3A (50 μm), it is displayed in white because the light intensity of the reflected light is strong, and is hardly distinguishable from the electrode pad.

  As described above, since the light intensity of the reflected light from the substrate changes depending on the thickness of the cream solder, the cross-sectional shape of the cream solder can be detected based on the intensity distribution of the reflected light, in other words, the brightness of the image. That is, it can be said that the portions of pixels having the same brightness have the same cream solder thickness because infrared light is considered to have passed through the cream solder by the same distance. Moreover, the area | region below fixed brightness can be said to be the area | region where the cream solder was apply | coated with thickness more than fixed.

  For this reason, when the cream solder applied to the substrate P has cross sections (directions perpendicular to the substrate surface) as shown in FIGS. 4A to 4C, for example, these substrates P When the substrate P is imaged by irradiating infrared light with a predetermined intensity to each, the images are as shown in FIGS. 5 (a) to 5 (c).

  Specifically, as shown in FIG. 4A, when the cream solder a is thick and widely applied, the infrared light has a longer distance to pass through the cream solder in a wide planar area of the cream solder. . For this reason, as shown to Fig.5 (a), an image with a large area of a dark part (code | symbol e) is obtained. The shape of the dark part e can be said to be a cross-sectional shape of the cream solder a at a predetermined thickness.

  On the other hand, as shown in FIG. 4B, when the cream solder b is applied thinner and narrower than the cream solder a, the planar area passing through the cream solder becomes narrower, and the distance passing through the cream solder. Is also shortened. For this reason, as shown in FIG.5 (b), the image with a small area of a dark part (code | symbol f) is obtained. The shape of the dark part f can be said to be a cross-sectional shape of the cream solder b at a predetermined thickness.

  Moreover, as shown in FIG.4 (c), when the bubble d exists in the inside of the cream solder c, the distance which the infrared light which permeate | transmits the location corresponding to the bubble d passes the cream solder inside becomes short. . For this reason, as shown in FIG.5 (c), the image of the dark part (code | symbol g) of the donut shape where the part of the bubble d is bright is obtained. The shape of the dark part g can be said to be a cross-sectional shape of the cream solder c at a predetermined thickness.

  As described above, according to the present embodiment, the substrate coated with cream solder is irradiated with infrared light whose combined direction is perpendicular to the substrate, and the substrate is imaged from vertically above, Since the cross-sectional shape of the surface parallel to the cream solder substrate can be detected based on the image showing the intensity distribution of the reflected light from the substrate, the inside of the cream solder can be detected without using X-rays as in the prior art. Bubbles, the area of cream solder at a predetermined height, and the like can be detected.

  Note that the intensity of the reflected light is proportional to the intensity of the irradiated infrared light. For example, as shown in FIG. 6, as the intensity of infrared light is increased, the intensity of reflected light is increased, and the brightness of pixels corresponding to cream solder becomes brighter. Specifically, the brightness of the cream solder l on the electrode pad k becomes brighter as the intensity of infrared light increases from the image h to the image j. Therefore, it can be said that even if the image of the cream solder having the same brightness is used, if the intensity of the irradiated infrared light is high, the cream solder in that portion is thick.

[Operation of inspection equipment]
Next, with reference to FIG. 7, the inspection operation by the inspection apparatus 1 according to the present embodiment will be described.

  First, when the imaging unit 86a of the main control unit 86 receives an instruction to perform an inspection operation from the input device 7 or the host computer, the drive control unit 83 applies a predetermined solder paste to the substrate on which the cream solder is applied. Then, the illumination controller 81 causes the illumination device 2 to irradiate the substrate with infrared light having a predetermined intensity (step S1). Here, the intensity | strength of infrared light is freely set suitably according to the thickness etc. of the cream solder apply | coated to the board | substrate. The intensity of the infrared light may be stored in the storage unit 85 in advance. Information about the thickness of the cream solder can be acquired from the input device 7 or the host computer, or can be acquired from the information stored in the storage unit 85.

  When the infrared light is irradiated, the imaging unit 86a causes the image processing unit 82 to cause the imaging device 4 to image the substrate irradiated with the infrared light (step S2).

  When an image is captured by the imaging device 4, the imaging unit 86a causes the image processing unit 82 to perform image processing on the captured image and generate image data (step S3). The generated image data may be stored in the storage unit 85.

  When the image data is generated, the area calculation unit 86b of the main control unit 86 calculates the area of the cross section of the cream solder from the image data (step S4). For example, based on the intensity distribution of the reflected light from the substrate, particularly the electrode pad, that is, the brightness of the pixel corresponding to the cream solder, the cross-sectional shape of the cream solder from the direction parallel to the substrate is detected, and the cream solder cross-section is detected. The area of the cross section of the cream solder is calculated by measuring the number of corresponding pixels.

  When the cross-sectional area of the cream solder is calculated, the determination unit 86c of the main control unit 86 determines whether or not the area of the cream solder is greater than or equal to a predetermined value (step S5). This determination can be performed, for example, by comparing the area of the cream solder calculated by the area calculation unit 86b with a preset threshold value. For example, when the amount of applied cream solder is small or there are bubbles inside and the cross-sectional area is smaller than a threshold value, the determination unit 86c determines that the area of the cream solder is not equal to or greater than a predetermined value. judge. By doing so, it is possible to detect an excessive amount of cream solder or the presence of bubbles. The threshold value may be stored in the storage unit 85 in advance.

  When the area of the cream solder is equal to or larger than the predetermined value (step S5: YES), the determination unit 86c carries out the board (step S6). On the other hand, when the area of the cream solder is not equal to or larger than the predetermined value (step S5: NO), the determination unit 86c determines that the cream solder is defective and performs a warning operation (step S7). As this warning operation, for example, a display indicating that there is a defect in cream solder may be displayed on the display device 6 or the like, or a lamp indicating a signal tower warning may be turned on. Thereby, it can prevent carrying out the board | substrate with which the defect cream solder was apply | coated.

  As described above, according to the present embodiment, infrared light having a predetermined intensity is irradiated onto a substrate coated with cream solder, the substrate is imaged, and infrared light reflected from the substrate is reflected. By detecting the cross-sectional shape of the cream solder based on the image representing the intensity distribution, it becomes possible to detect the internal state of the cream solder without using X-rays as in the prior art. The size can be reduced, and as a result, the state inside the cream solder can be detected more easily.

  The present invention can be applied to an inspection method and inspection apparatus for a substrate coated with cream solder.

It is a block diagram which shows the structure of the test | inspection apparatus of this invention. It is a figure which shows the structure of the illuminating device 2 typically. (A) is 50 μm, (b) is 70 μm, and (c) is an image of reflected light when infrared light of the same intensity is irradiated onto a substrate coated with cream solder on a 100 μm thick screen. FIG. It is a figure which shows typically the vertical cross section of (a)-(c) cream solder. (A)-(c) is a figure which shows typically the image of reflected light when irradiating the infrared light of the same intensity | strength to Fig.5 (a)-(c), respectively. It is a figure which shows the image of reflected light when changing the intensity | strength of infrared light. It is a flowchart which shows test | inspection operation | movement.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inspection apparatus, 2 ... Illuminating device, 2a ... Infrared LED, 2b ... Visible light LED, 3 ... Dimming device, 4 ... Imaging device, 5 ... Driving device, 6 ... Display device, 7 ... Input device, 8 ... Control Device: 81 Illumination control unit 82 ... Image processing unit 83 ... Drive control unit 84 ... I / F unit 85 ... Storage unit 86 ... Main control unit 86a ... Imaging unit 86b ... Detection unit 86c ... Judgment part.

Claims (3)

Irradiating a substrate coated with cream solder with infrared light having a predetermined intensity;
Imaging the substrate irradiated with the infrared light;
Detecting a cross-sectional shape of the cream solder along a surface spaced from the substrate based on an image representing an intensity distribution of infrared light reflected from the substrate. The inspection method according to claim 1, further comprising: determining a state of the cream solder based on a cross-sectional area of the cream solder. Illumination means for irradiating infrared light of a predetermined intensity to a substrate coated with cream solder;
Imaging means for imaging the substrate irradiated with the infrared light;
An inspection apparatus comprising: a detecting unit configured to detect a cross-sectional shape of the cream solder along a surface separated from the substrate based on an image representing an intensity distribution of infrared light reflected from the substrate.

Images