JP2009186447A - Inspection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection apparatus required for inspecting both portion with solder resist and portion without solder resist in inspection of circuit patterns to obtain circuit pattern of any solder resist-applied portion difficult to be obtained by image processing-based defect inspection because of lower brightness in image data of the solder resist-applied portion, furthermore irradiating light should be intensified for acquiring the circuit pattern of any solder resist-applied portion, however, the portion with no solder resist applied will be skipped to white. <P>SOLUTION: By using this inspection apparatus, any white skipped area is deleted from the image data by irradiation with intense light to conduct defect inspection. Then defect inspection of the deleted white skipped area is conducted by irradiation with light of normal intensity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a circuit pattern inspection apparatus and inspection method for automatically inspecting printed circuit board circuit patterns and LSI circuit pattern defects by image processing.

  In general, a circuit pattern inspection apparatus compares two sets of circuit patterns and detects a mismatched portion as a defect. As the two sets of circuit patterns, there are a method in which two adjacent circuit patterns are imaged, or a method in which one is a predetermined reference pattern and the other is a pattern to be inspected.

  As a circuit pattern defect inspection method, a method of comparing a reference pattern and an inspection object to be inspected and detecting the difference as a defect has been proposed (see Patent Document 1).

  By the way, in the circuit pattern, there is a portion where a solder resist is applied to protect the pattern. Solder resist is used for the purpose of preventing short circuit by soldering and mechanical protection of the wiring pattern except for the part other than the part where the copper foil part in the circuit pattern is planned to prevent oxidation or soldering. It is applied to the part.

  Accordingly, the solder resist is required to have electrical insulation, heat resistance, weather resistance, and the like. Therefore, thermosetting resins such as epoxy resin, phenol resin, polyurethane resin, silicone, and polyimide resin are mainly used. Usually, it is colored green translucent to reduce the visual fatigue of the inspector during visual inspection.

  That is, in the circuit pattern, a green semi-transparent portion and a non-transparent portion may be mixed. The portion to which the solder resist is applied is a portion with low luminance as image data, and the portion to which the solder resist is not applied is a portion with high luminance. The circuit pattern inspection apparatus needs to cope with the defect inspection of the high luminance portion and the low luminance portion.

In response to such a requirement, Patent Document 2 discloses an invention in which two types of illumination for a solder resist coating portion and a portion without a solder resist are prepared in an inspection apparatus. These two types of illuminations have different installation angles. By applying light with different irradiation angles, it is intended to distinguish a portion where the solder resist is applied from a portion where it is not.
Japanese Examined Patent Publication No. 59-024361 JP 2007-139676 A

  As in Patent Document 2, it is not easy to determine the presence or absence of a solder resist simply by changing the angle of light applied to a circuit pattern that is an object to be inspected. In the case of Patent Document 2, since the image processing routine does not change, it is necessary to pass image data that can correspond to an image processing method having a previously assumed gradation to the image processing routine. However, simply changing the angle of the irradiating light cannot cope with conditions such as the type of solder resist and the coating thickness, and the brightness of the image data in the portion with and without the solder resist cannot be made the same.

  Further, when the light is irradiated obliquely, there is a problem that the detection accuracy of the concavo-convex defect on the surface of the lead wire is lowered.

  The present invention has been conceived in view of such problems. That is, it is an object of the present invention to provide an apparatus and a method capable of inspecting a defect where a solder resist is applied and a part where the solder resist is applied with a small number of stages without reducing the detection accuracy of the irregularities on the lead wire surface.

  The present invention irradiates the object to be inspected with high illuminance light, obtains the portion where the solder resist is not applied as overexposed image data, and applies to the portion other than the overexposed region in the image data. By performing defect inspection by image processing, a portion to which a solder resist is applied is inspected.

That is, the inspection apparatus of the present invention is
An apparatus for inspecting a defect of an inspection object from image data of the inspection object,
Illumination means capable of changing the illuminance of light irradiating the inspection object,
Imaging means for acquiring image data of the inspected object in the previous period;
The inspection apparatus includes an image processing unit that performs defect inspection from an area in which the luminance is equal to or lower than a predetermined threshold in the image data.

Moreover, the inspection method of the present invention includes:
A method for inspecting a defect of an inspection object from image data of the inspection object,
Irradiating the object with light,
Obtaining image data of the inspection object;
The inspection method includes a step of performing image processing for performing defect inspection from an area in which luminance is not more than a predetermined threshold in the image data.

  Since the present invention determines the presence or absence of a portion coated with a solder resist by changing the amount of light to be irradiated, the illumination angle of illumination does not change. Therefore, there is an effect that the detection sensitivity to the irregularities on the surface of the lead wire does not decrease. Further, the inspection stage may be a set of stages using transmitted light and reflected light, and has an effect that the installation place of the apparatus may be narrow.

  Before describing the inspection apparatus of the present invention, the concept of the inspection apparatus of the present invention will be briefly described. In the inspection apparatus of the present invention, first, sufficiently bright light is irradiated onto the circuit pattern formed on the resin. In the present specification, this “sufficiently bright light” is referred to as high illuminance light.

  The image data of the lower circuit pattern can be obtained through the solder resist layer with sufficiently bright light. However, at that time, the portion where the solder resist is not applied becomes overexposed. Note that “out-of-white” refers to a phenomenon in which a subject with a certain level of brightness is painted white. In this specification, the term “out-of-white” is used not only when the pixel value in the image data becomes the maximum value but also when the pixel value exceeds a predetermined threshold.

  Thus, the defect inspection is performed by removing the overexposed portion from the image processing area. Then, the circuit pattern is irradiated with light having a brightness that is normal enough to recognize the circuit pattern of the part where the solder resist is not applied, and the defect inspection is performed on the part that has been blown out. The inspection apparatus of the present invention discriminates the area where the solder resist is applied by using the whiteout of the image data obtained by changing the brightness in this way. In the present specification, the part that is overexposed is called a bright region. In addition, “light having normal brightness enough to recognize a circuit pattern” is referred to as low illuminance light.

Next, details of the inspection apparatus of the present invention will be described.
FIG. 1 shows the configuration of an inspection apparatus 1 according to the present invention. The inspection apparatus of the present invention includes an imaging unit 10, a control unit 20, a light 11, a light amount adjustment unit 12, a driving unit 30, a storage unit 40, and a defect analysis unit 50.

  The imaging means 10 images the inspection object 90 and acquires the image data Vd. Accordingly, it includes a light conversion element for converting light into electronic data and a lens system for focusing on the light conversion element. As the light conversion element, a line memory, a CCD, or the like can be suitably used. Although the lens system is not particularly limited, the focal length, the angle of view, the F number, and the like of the lens system can be appropriately designed based on the pixel size required for the inspection apparatus 1. The pixel size required in the inspection apparatus 1 can be obtained from the size of the defect to be detected.

  The light 11 irradiates the inspection object 90 with light to increase the SNR (Signal to Noise Ratio) of image data captured by the imaging unit 10. Here, the light 11 is shown installed on the same side as the imaging unit 10 with respect to the inspection object 90, but may be installed on the opposite side of the imaging unit 10 with respect to the inspection object 90. When a light is installed on the opposite side, image data based on the transmitted light of the inspection object 90 can be obtained.

  The light 11 is not particularly limited, but a halogen light, a fluorescent lamp, an LED, or the like can be suitably used. The wavelength of light emitted from the light 11 is not particularly limited, but white light composed of light in a continuous wavelength band, white light obtained by mixing a plurality of colors, and the like can be suitably used.

  The light adjustment unit 12 supplies power Lpw to the light 11 according to the instruction Cld from the control unit 20. In particular, the power Lpw can change in magnitude continuously or stepwise. Therefore, a variable power supply can be suitably used.

  The light amount adjusting means 12 is not limited to this, for example, changing the wavelength of light to be irradiated, or inserting a colored translucent filter between the light 11 and the inspection object 90. May be. Moreover, the light 11 and the light quantity adjusting means 12 need to be able to irradiate high illuminance light and low illuminance light.

  The driving unit 30 installs the inspection object 90 at a predetermined position below the imaging unit 10. A drive means is not specifically limited, A belt, a roller, etc. can be utilized. When the inspection object 90 is in a tape shape, it may be a take-up reel or a take-up reel. Further, when a plurality of imaging means 10 are provided, the inspection object may be moved between the imaging means. The operation of the drive unit 30 is controlled by a drive instruction Cdv from the control unit 20.

  The control unit 20 controls the operation of the inspection apparatus 1. Specifically, a drive instruction Cdv is sent to the drive means 30, the inspection object 90 is placed at a predetermined position, an illumination instruction Cld is sent to the light amount adjustment means 12, and light is applied to the inspection object 90 to take an image. Control for obtaining the image data Vd from the means 10 is included.

  For the acquired image data Vd, the control means 20 itself performs predetermined data processing and records it in the storage means 40 as inspection data Fv. The inspection data Fv may include image data of the inspection object 90 and data by the control unit 20 or a result of data processing, or both. For example, identification data of the inspection object 90 may be added, or defect candidates included in the image data may be extracted.

  The defect candidate extraction process may be a process in which the defect candidate is compared with the image data Vd of the inspection object 90 and a master pattern as a model. Therefore, the control unit 20 may have master pattern data or may be loaded from another memory (not shown).

  The defect analysis means 50 can access the storage means 40. The defect analysis means 50 sends a request instruction Rq to the storage means 40, and acquires partial image data (hereinafter referred to as “partial image data”) Pv of a portion considered to be a defect from the stored inspection data Fv. The defect analysis means 50 analyzes the partial image data Pv and outputs a result Rt indicating the presence or absence of a defect.

  As the storage means 40, a semiconductor memory, an HDD (Hard Disc Drive), a DVD, a CD, or the like can be specifically used, but an HDD that can perform recording and reproduction and has a high data transfer speed is preferably used.

  The control means 20 and the defect analysis means 50 can be realized by an MPU (Micro Processor Unit) and a processing program. These may be realized by one MPU or may be realized by different MPUs. Moreover, you may implement | achieve by hardware instead of MPU and a program.

  Next, FIG. 2 shows a processing flow of the control means 20, and the operation of the control means 20 will be described. When the process starts (step S100), the control means 20 determines whether or not the process is completed (step S110). The end of the process may be determined based on whether a predetermined signal has been received or whether a predetermined number of inspections have been completed. In the case of termination (Y branch of step S110), the process is terminated (step S111).

  When the process is continued (N branch in step S110), the inspection object 90 is set at a predetermined position (step S120). This is realized by sending a drive instruction Cdv to the drive means 30. When the inspection object 90 is set at a predetermined position, the next sufficiently bright light (high illuminance light) is irradiated (step S130). Sufficiently bright light is realized by transmitting a light amount instruction Cld to the light amount adjusting means 12, and the light amount adjusting means 12 supplies a large electric power Lpw to the light 11.

  In addition, the high illuminance light means that the image data of the lower circuit pattern is obtained through the solder resist applied on the circuit pattern, and the brightness is so high that the reflected light from the portion where the solder resist is not applied is blown out. It will be higher.

  Note that here, “out-of-white” means not only that the image data is completely white, but also over-out if the image data is higher than a predetermined threshold Thwo.

  If high illumination light is irradiated, image data Swo is acquired (step S140). The image data Swo includes whiteout in the data. Further, data processing is performed on the acquired image data Swo to extract defect candidates and include them in the inspection data Fv.

  FIG. 3 shows a more detailed flow of step S140. After obtaining the image data Swo (step S202), a region A having a luminance equal to or lower than a predetermined threshold value Thwo is obtained in the image data Swo (step S203). As an example of this process, the following process can be considered. First, the pixel value in the image data Swo is sequentially compared with the threshold value Thwo. Each pixel in the image data Swo has a quantized luminance value such as 8 bits or 10 bits, and the luminance value is compared with a threshold Thwo. Then, all the values of the pixels whose luminance is higher than the threshold Thwo are replaced with the maximum luminance value Imax.

  Next, the boundary line of the portion where the pixel value is the maximum value and not is extracted. Here, the portion where the pixel value is not the maximum value is a pixel whose pixel value is smaller than the threshold Thwo. Therefore, a region surrounded by the obtained boundary line is a region A. For example, the area A may be obtained as the coordinates of the start point and end point of the boundary line. Region A is a portion where a solder resist is applied. Here, the area A is called a dark area. On the other hand, an area other than the area A is called a bright area. The bright region is a region where the pixel value is larger than the threshold value Thwo, and is also a region that is “out-of-white”. In some cases, a foreign object may appear somewhat dark in the bright area, but black spots in the bright area are not included in the dark area.

  Next, the brightness of the dark area is adjusted (step A204). Although the portion to which the solder resist is applied is irradiated with strong illumination, there may be image data with low contrast. Thus, the dark region is processed so that the contrast is obtained by adjusting the luminance. Since luminance is synonymous with a pixel value (pixel value), luminance adjustment is also referred to as pixel value adjustment.

・・・・・・・・・・・・・・（１） As an example of specific processing, the following processing can be given. The maximum pixel value in the dark region is Amax, and the minimum pixel value in the dark region is Amin. At this time, the value Ax of an arbitrary pixel in the dark region can be obtained as the adjusted pixel value Va by the equation (1).

.... (1)

  Here, Imax is the maximum pixel value. The third term on the right side corresponds to the magnification for converting the value of the image data in the dark region into the maximum value of the pixel value. The parenthesis in the second term on the right side is the difference between the intermediate value of the pixel values in the dark region and the pixel value Ax. Therefore, the second term and the third term on the right side can be obtained as the distance from the average value Imax / 2 when the maximum pixel value is Imax.

  Since the first term on the right side is half of the maximum value Imax of the pixel, Va on the left side is a conversion in which the maximum value of the pixel value is Imax. In other words, the image data having the minimum value Amin to the maximum value Amax is converted from the zero to the image data having the minimum value Imax. Note that this brightness adjustment is an example and is not limited to this conversion.

  Then, defect candidates in the dark area are included in Fv (step S205). In the defect candidate extraction, the dark area image data is compared with the master pattern, and different portions are extracted as defect candidates. Image data including defect candidates is referred to as partial image data Pv. Therefore, it can be said that the process of step S205 is to include the partial image data Pv in the inspection data Fv. Thereafter, the process returns to step S150 (step S206).

  In step S203, when determining a portion to which the solder resist is not applied (a white portion), a portion that is not white in the white region may be found. This is considered to be a pin hole of the solder resist formed at the time of applying the solder resist. Such a portion may be processed separately, and that fact may be included in the inspection data Fv.

  An example of the dark area 61 is shown in FIG. The entire circuit pattern is an area represented by reference numeral 60, and reference numeral 62 is a whiteout area. A portion to which the solder resist is applied is represented by reference numeral 61, and image data of the circuit pattern 63 under the solder resist can be obtained by strong light.

  Returning to FIG. 2, next, the illumination is lowered to normal illuminance (step S150). The normal illuminance is such illuminance that it is possible to acquire image data of a portion where no solder resist is applied. This is low illumination light.

  Further, image data Sno is acquired (step S160). Then, defect candidates are extracted from the area (bright area) excluding the area where the solder resist is applied and included in the inspection data Fv.

  FIG. 4 shows a more detailed flow of step S160. After obtaining the image data Sno (step S302), a region other than the dark region in the image data Sno is set as a bright region (step S303). In other words, a portion that has been whitened in the image data Swo is set as a bright area. The entire area of the image data Swo and the image data Sno does not change. Therefore, the bright area can be determined by applying the pixel coordinates of the dark area in the image data Swo to the image data Sno.

  Next, the brightness of the bright area is adjusted (step S304). However, this step may be skipped. This is because the bright region is a portion where the solder resist is not applied, and the illuminance of the irradiated light is set so that the image data of this portion can be processed.

  Then, defect candidates in the bright area are extracted and included in the inspection data Fv (step S305). Thereafter, the process returns to step S170. The image data including the defect candidate is called partial image data Pv as in the case of the image data Swo.

  FIG. 6B shows a state where image data of a bright area is obtained. Since the illumination is in a normal state (low illuminance light), the portion 61 to which the solder resist is applied is almost blacked out. Since this area is identified as a dark area, it is deleted from the entire inspection area 60 in this case, and defect candidates are detected for other parts. In addition, although the code | symbol 64 is a thick lead | read | reed part, it is a part which was overwhelmed in step S140 by high illumination intensity light.

  Returning to FIG. 2, the identification code of the circuit pattern last inspected is attached, and the inspection data Fv is completed and output (step S170).

  Returning to FIG. 1, according to the flow described above, the control unit 20 creates the inspection data Fv and records it in the storage unit 40. The defect analysis means 50 transmits an instruction Rq for requesting the partial image data Pv to the storage means 40 to obtain the partial image data Pv. The partial image data Pv is an image including defect candidates.

  The data processing performed on the image data acquired by the control unit 20 is also referred to as image processing including processing to be recorded in the storage unit 40. In the present invention, the control means 20 performs image processing twice when irradiated with high illuminance light and when irradiated with low illuminance light. These may be called first image processing and second image processing, respectively. This is because the object to be handled is image data. Although the control unit 20 switches the illumination here, it may be switched by a signal from the driving unit or the imaging unit based on the movement of the inspection object or the transmission of the image data.

  The defect analysis means 50 analyzes the presence / absence of a defect with respect to the partial image data Pv by processing such as continuity of the lead portion and expansion / contraction of the image data. The analysis result is output as a result Rt including the presence or absence of a defect.

The present invention can be suitably used for a circuit pattern inspection apparatus.

It is a figure which shows the structure of the test | inspection apparatus of this invention. It is a figure which shows the flow of a control means. It is a flowchart which shows the process of the image containing a whiteout. It is a flowchart which shows the process of an image without whiteout. It is a figure which illustrates the image data when not making it be overexposure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inspection apparatus 10 Imaging means 11 Light 12 Light quantity adjustment means 20 Control means 30 Drive means 40 Storage means 50 Defect analysis part

Claims (10)

An apparatus for inspecting a defect of an inspection object from image data of the inspection object,
Illumination means capable of changing the illuminance of light irradiating the inspection object,
An imaging means for acquiring image data of the inspection object;
When the illumination light of the illumination unit is a high illuminance light, the pixel value of the image data acquired from the imaging unit is set as a bright region, a portion other than the bright region as a dark region,
Data processing is performed on the dark area with the illumination light of the illumination means as high illuminance light,
The inspection apparatus which has a control part which performs a data process with respect to the said bright area | region as the illumination light of the said illumination means as low illumination light. The inspection apparatus according to claim 1, wherein the data processing includes processing for adding identification data of the inspection object. 3. The inspection apparatus according to claim 1, wherein the data processing further includes processing for extracting defect candidates. The inspection apparatus according to any one of claims 1 to 3, wherein the data processing further includes processing for recording the defect candidate in a recording unit. The inspection apparatus according to any one of claims 1 to 4, further comprising defect analysis means for performing defect inspection of the data-processed dark region or bright region. An inspection method for inspecting a defect of an inspection object from image data of the inspection object,
A high illuminance light irradiation step of irradiating the inspected object with high illuminance light; and
An imaging step of acquiring image data of the inspection object;
A first image processing step of performing image processing on the dark region, with a region having a pixel value of the image data equal to or greater than a predetermined threshold as a bright region, and a region other than the bright region as a dark region;
A low illuminance light irradiation step of irradiating the inspection object with low illuminance light; and
An imaging step of acquiring image data of the inspection object;
An inspection method including a second image processing step of performing image processing on the bright region. The inspection method according to claim 6, wherein the first and second image processing steps include a step of adding at least an identification number of the inspection object. The inspection method according to claim 6, wherein the first and second image processing steps include a step of extracting defect candidates. The inspection method according to any one of claims 6 to 8, wherein the first and second image processing steps further include a recording step of recording the defect candidates in a recording unit. The inspection method according to any one of claims 6 to 9, further comprising a defect inspection step of performing a defect inspection on the defect candidate.

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