JP2007205974A - Method of inspecting plating, and method of inspecting lead frame - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging method suitable for inspecting precisely a defect in a plated lead frame without depending on manual work, and a method of inspecting plating for inspecting automatically the plating defect on a real time with high reliability. <P>SOLUTION: This method of inspecting the plating defect carries out the inspection by imaging a plated surface irradiated by an irradiation means 10, using the irradiation means 10 for irradiating the plating with light beam having 600 nm or more of wavelength, and an imaging means 20 having sensitivity within a wavelength area thereof. The method is provided with: the irradiation means 10 for irradiating the plating with the light beam having the 600 nm or more of wavelength; the imaging means 20 for imaging the plated surface irradiated by the irradiation means 10, and an image processing/defect determining means 30 for determining the presence of the defect on the plating, based on an image data obtained by the imaging means, to perform the inspection. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plating inspection method and apparatus for lead frames used for internal wiring of a semiconductor package, and more particularly to a defect inspection method and apparatus using image data obtained by an imaging means.

  Currently, the size of the semiconductor package using a lead frame is expanding due to expansion of applications, and strict quality assurance is required for the lead frame as a base material. In general, lead frame manufacturing methods include a stamping method in which metal is mechanically punched using an ultra-precise mold and an etching method in which metal is chemically corroded to form a pattern, and as high-density mounting is accelerated, The accuracy of micron units is required.

Conventionally, in many cases, such plating frame inspection in the lead frame manufacturing process is not performed mechanically, but is performed by visual inspection by hand. A lead frame plating inspection method is described in, for example, Japanese Patent Application Laid-Open No. H10-228707.
JP 2000-171402 A

  However, the visual inspection is a manual inspection, and the determination result varies depending on the state of the inspector (such as fatigue) or individual differences, and the certainty of the inspection depends on the visual sense of the inspector.

The present invention has been devised in view of the above-described problems, and provides an imaging method suitable for inspecting defects of plated lead frames with high accuracy without human intervention, and automatically inspecting plating defects. An object of the present invention is to provide a plating inspection apparatus that can be performed in real time and with high reliability.

A plating defect inspection method characterized by imaging the plating surface irradiated by the irradiation means 10 by the irradiation means 10 for irradiating the plating with a light beam having a wavelength of 600 nm or more and the imaging means 20 having sensitivity in the wavelength range; Irradiation means 10 for irradiating the plating surface with a light beam having a wavelength of 600 nm or more, imaging means 20 for imaging the plating surface irradiated by the irradiation means 10, and presence / absence of defects on the plating from the image data obtained by the imaging means The lead frame plating defect inspection apparatus is provided with an image processing / defect determination means 30 for determining the defect. The present invention has the following configuration.

(Claim 1)
Illuminating at least the plated part with illumination, and creating image data obtained by imaging the reflected light by the imaging means,
The method for inspecting silver plating, wherein the irradiation light from the illumination comprises light having a wavelength of 600 nm or more.

(Claim 2)
The plating inspection method according to claim 1, wherein the irradiation is an LED or an optical fiber.

(Claim 3)
The plating inspection method according to claim 1, wherein the illumination has a ring shape or a dome shape.

(Claim 4)
The plating inspection method according to claim 1, wherein an elevation angle formed by the illumination and the imaging unit via a lead frame is in a range of 0 to 60 °.

(Claim 5)
The plating inspection method according to claim 1, wherein the imaging unit is a line sensor or an area sensor.

(Claim 6)
The plating inspection method according to claim 1, wherein the imaging unit is a color camera or a monochrome camera.

(Claim 7)
The plating inspection method according to claim 1, wherein defect extraction is performed on the image data obtained by the imaging unit by simple binarization, simple difference, or pattern matching.

(Claim 8)
The red component or the brightness component is extracted from the color image data obtained by the imaging unit, and defect extraction is performed by simple binarization, simple difference, or pattern matching. Inspection method of plating as described.

(Claim 9)
9. A lead frame inspection method comprising: inspecting a plating applied to a lead frame by the plating inspection method according to claim 1.

As described above, according to the present invention, when inspecting the lead frame for plating defects, it can be automatically performed, so that variation in determination results due to individual differences as seen in visual inspection is suppressed, and the burden on the inspector is reduced. Can be reduced. Also, paying attention to the fact that a lot of defect information is included in the imaging signal, inspection processing is performed from the signal extracted from this information, so it is possible to accurately determine the presence or absence of defects and realize highly accurate inspection it can. Furthermore, by imaging with predetermined processing, it is possible to perform various commonly known image processing such as simple comparison processing with adjacent pixels, mathematical form processing, etc. it can.

Embodiments of a lead frame plating inspection apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration schematic diagram showing an embodiment of a plating inspection apparatus of the present invention.
The plating inspection apparatus of the present invention includes an irradiating means 10 for irradiating a light beam having a wavelength of 600 nm or more to plating, a CCD (charge-coupled device) camera 21 for imaging the plated surface irradiated by the irradiating means, and an optical system 22. The imaging unit 20 and image processing / defect determination unit 30 that determines the presence or absence of defects on the plating from the image data obtained by the imaging unit 20 are configured. The plating inspection apparatus of the present invention irradiates the plating with a light beam having a wavelength of 600 nm or more by the irradiating means 10 and images the plating by the imaging means having sensitivity in the wavelength range, thereby providing a high-definition plating image. Therefore, it is possible to easily determine the presence or absence of plating defects, and labor saving of inspection and efficiency of inspection work can be greatly improved. A light beam having a wavelength of 600 nm or more is a light beam that does not include or hardly includes a wavelength less than 600 nm. Alternatively, a light beam having a wavelength of 600 nm or more is a light beam composed of only light having a wavelength of 600 nm or more, or consisting only of light having a wavelength of approximately 600 nm or more. For example, the light source irradiated through the filter which uses a well-known red LED, a white light source, etc. and cuts the wavelength of 600 nm or less can be illustrated.

A CCD camera 21 is disposed above the lead frame 40. The CCD camera 21 images the upper side of the lead frame 40 fixed to the base 50 and outputs an imaging signal. The image processing / defect determination means 30 is connected to the CCD camera 21 and receives an imaging signal generated by the CCD camera 21 and executes a defect detection process. The display device 60 is connected to the image processing / defect determination means 30 and displays the result of the defect detection processing.

Next, details of the lead frame are shown in FIG. FIG. 2 (b) shows a lead frame (raw material) 41 that has been subjected to silver plating after being manufactured by an etching method or the like. A lead frame (raw material) 41 manufactured by an etching method or the like has a die pad 42, an inner lead 43, an outer lead 44, a dam bar 45, and a frame portion 46. After that, the inner lead 43 has a connection resistance between a semiconductor element and a bonding portion. Silver plating is applied to reduce the temperature. In general, a lead frame is not manufactured alone, but a single strip-shaped lead frame is manufactured from a large number of identical patterns. For this reason, when performing a lead frame plating defect inspection, there are a large number of plating portions 47 to be inspected in the lead frame, not in one place.

FIG. 3 shows the spectral reflectance of pure silver. The reflectance of silver is 95% or more for light having a wavelength of 600 nm or more than the spectral reflectance, and the reflectance is substantially constant for light having a wavelength of 600 nm or more. Therefore, when light having a wavelength of 600 nm or more is incident, large and stable reflected light can be obtained.

Silver plating defects include the presence or absence of plating and changes in the shape of plating typified by foreign matter and wrinkles. In either case, silver itself has a high reflectivity for light with a wavelength of 600 nm or more. Therefore, it is easy to obtain contrast for defect detection.

Next, an example of the irradiation means 10 will be described with reference to FIGS. Although it is assumed that the LED or optical fiber can irradiate light having a wavelength of 600 nm or more, the LED is not limited to these if the irradiation in the wavelength range is satisfied. In the case of an optical fiber, the wavelength range may be limited by a band pass filter or the like. The shape of the irradiation means 10 is shown in FIGS. 4 shows a ring shape as an example of the shape of the irradiation means 10, and FIG. 5 shows a dome shape as an example of the shape of the irradiation means 10. 4 and 5, as long as a high amount of light can be applied to the plating portion 47, another shape such as a line-shaped illumination may be used, but ideally, the target plating portion 47 has a 360 ° circumference from the upper surface. A ring shape or dome shape capable of irradiation is suitable. The ring shape or dome shape has an advantage that the amount of light can be secured, and when the inner lead 43 is manufactured by an etching method, the pattern cross-sectional shape (vertical direction) of the inner lead 43 is not a square shape (step difference) Even if it has a hexagonal shape including a step), it is also suitable from the viewpoint of having little effect on imaging including the step of the plated portion 47.

FIG. 6 shows an example of the pattern cross-sectional shape of the inner lead 43 manufactured by the etching method. FIG. 6A shows an example of a linear step shape, FIG. 6B shows an example of a curved step shape, and both of FIG. 6A and FIG. When manufacturing by an etching method, the pattern cross-sectional shape of the inner lead 43 is a shape as shown in (a) or (b). When the pattern cross-sectional shape of the inner lead 43 is as shown in FIG. 6A or 6B, if the incident light is from one direction such as a line-shaped illumination, it is difficult to capture the stepped portion 70. Therefore, the shape of the irradiating means 10 is suitably a ring shape or a dome shape capable of irradiating around 360 degrees.

Next, the elevation angle of the irradiation means 10 according to claim 5 will be described with reference to FIG. FIG. 7 shows the arrangement of the imaging means 20, the lead frame 40, and the light emitting part 12 of the irradiation means 10. The imaging means 20 is arranged so as to be perpendicular to the surface of the lead frame 40, and the elevation angle is the intersection P0 orthogonal to the imaging direction (optical axis) L0 of the imaging means 20 and the surface of the lead frame 40 and the light emission of the irradiation means. This is an angle formed with the part 12. The elevation angle [theta] is 0 [deg.] To 60 [deg.], More preferably 40 [deg.] To 60 [deg.]. The light component close to the imaging direction (optical axis) L0 of the imaging means 20 of 60 ° or more is close to the regular reflection light, and a large amount of light can be incident on the CCD camera 21, but the lead frame 40 can ensure flatness. Since it is difficult and minute irregularities exist on the surface of the lead frame 40, it is difficult to detect defects. Further, in the vicinity of 0 °, the amount of light incident on the CCD camera 21 tends to decrease, and the defect can be detected. However, since it is difficult to obtain a contrast with the defect, it is ideally 40 ° to 60 °. Is suitable.

Next, the imaging means 20 according to claims 6 and 7 will be described. On the premise that the CCD camera 21 has sensitivity at a wavelength of 600 nm or more, the image sensor may be either a line sensor or an area sensor, and image capturing may be either color or monochrome, and this is not particular.

Next, schematic configuration schematic views showing an embodiment of the plating inspection apparatus of the present invention according to claim 4 are shown in FIGS. 8 shows an embodiment in which a ring shape is applied as an example of the shape of the irradiation means 10 shown in FIG. 4, and FIG. 9 shows an embodiment in which a dome shape is applied as an example of the shape of the irradiation means 10 shown in FIG. It is.

Next, the overall operation of the image processing / defect determination means 30 will be described with reference to the flowchart of FIG. When the lead frame 40 to be inspected is fixed to the base 50 and irradiated with light from the light emitting unit 12 of the irradiation means via the power supply 11 of the irradiation means, the lead frame 40 is imaged (step S1). . The CCD camera 21 sequentially images a large number of plating parts 47. The imaging of the plated portion 47 is performed by scanning the entire plated portion 47 instead of scanning only the center of the plated portion 47 in the case of a line sensor, for example, in the case of a line sensor. Is done. The imaging signal generated by the CCD camera 21 is sent to the image processing / defect determination means 30. The image processing / defect determination means 30 extracts the information (plating information) of the plating part 47 from this imaging signal (step S2). Further, the image processing / defect determination means 30 executes defect detection / determination processing using the extracted plating information (step S3). This defect detection / determination process is executed for all the plated portions 47 formed on the lead frame 40, and thereafter the entire operation is completed (step S4, YES).

Next, the defect detection / determination process (step S4) according to claim 8 will be described. FIG. 11A shows a plated portion 47, a non-plated portion 48, and a defective portion 49 (for example, a surface discoloration defect) of the inner lead 43. FIG. 11B is a diagram in FIG. The profile on line L1 is shown. As shown in FIG. 11B, contrast exists between the plated portion 47, the non-plated portion 48, and the defect portion 49. Accordingly, defect detection can be performed by performing image processing such as simple binarization, simple difference, or pattern matching on the obtained image data.

Next, the defect detection / determination process (step S4) according to claim 9 will be described. When the image is captured in color, it is possible to extract information such as red, blue, green, hue, saturation, brightness, etc., but for light with a wavelength of 600 nm or more, it shows a red component or simple brightness. Extraction of the brightness component can obtain more contrast. Defect detection can be performed by performing image processing such as simple binarization, simple difference, or pattern matching on image data after information extraction.

Example 1
Next, Example 1 in the embodiment will be described. FIG. 12 shows the same position as in FIG. 11A when the irradiation means 10 in the embodiment is a dome-shaped LED (red, peak wavelength 660 nm), and the CCD camera 21 of the imaging means 20 is a monochrome camera of a line sensor. , Shows the profile on line L1.

(Example 2)
Next, Example 2 in the embodiment will be described. In FIG. 13, the irradiation means 10 in the embodiment is a ring-shaped LED (red, peak wavelength 660 nm), the elevation angle θ of the light emitting section 12 is 50 °, and the CCD camera 21 of the imaging means 20 is a monochrome camera of a line sensor. In this case, the profile on the line L1 at the same position as in FIG.

(Example 3)
Next, Example 3 in the embodiment will be described. In FIG. 14, the irradiation means 10 in the embodiment is a dome-shaped LED (red, peak wavelength 660 nm), the elevation angle θ of the light emitting section 12 is 0 ° to 60 °, and the CCD camera 21 of the imaging means 20 is an area sensor. In the case of a color camera, the profile on the line L1 is shown at the same position as in FIG.

(Comparative Example 1)
Next, Comparative Example 1 will be described. FIG. 15 shows that the irradiation means 10 in the embodiment is red (wavelength 600 nm or more) through a line-shaped optical fiber, a bandpass filter that passes only a specific wavelength band between the illumination irradiation means 10 and the lead frame 40, The CCD camera 21 of the imaging means 20 is irradiated with green (wavelength 500 to 600 nm) and blue (wavelength 300 to 500 nm), and the elevation angle θ of the light emitting section 12 is 10 °, 30 °, 40 °, 60 °, 70 °. Is the result of dividing the average value of the gradation values of the plated portion 47 and the defective portion 49 based on the profile on the line L1 at the same position as in FIG. It is. The result of dividing the average value of the gradation values represents the contrast ratio between the plated portion 47 and the defect portion 49, and was used to relatively determine the measurement result due to the difference in sensitivity of the CCD camera 21 in different wavelength regions.

Examining the results of FIG. 15, in any wavelength region, when the elevation angle θ of the light emitting section 12 is 70 °, an extreme decrease in contrast ratio is seen, and when the elevation angle θ is 0 ° to 60 °, high contrast is observed. The ratio of can be obtained. For each wavelength range, a high contrast ratio is obtained in the order of red, green, and blue at any elevation angle θ.

(Comparative Example 2)
Next, Comparative Example 2 will be described. FIG. 16A shows a case where the irradiation means 10 in the embodiment is a dome-shaped LED (red, peak wavelength 660 nm), and the CCD camera 21 of the imaging means 20 is an area sensor color camera. The illuminating means 10 is green (peak wavelength 525 nm) and blue (peak wavelength 470 nm) of the dome-shaped LED, and the CCD camera 21 of the imaging means 20 is an area sensor. In the case of a color camera, the profile on the line L1 is shown at the same position as in FIG. FIG. 16B shows the result of dividing the average value of the gradation values of the plated portion 47 and the defective portion 49 of FIG. 16A based on the profile on the line L1 at the same position as FIG. , Green and blue wavelength ranges.

When the result of FIG. 16B is examined, a high contrast ratio is obtained in the order of red, green, and blue as in FIG. Further, as for the contrast ratio for each wavelength region, the difference between red, green, and blue is significant compared to FIG.

It is a schematic structure schematic diagram showing the structure of a plating inspection apparatus according to an embodiment of the present invention. (A) is explanatory drawing which shows the shape of a lead frame (raw material). (B) is explanatory drawing which shows the state which gave silver plating after (a). It is explanatory drawing which shows the relationship between the wavelength of light and a reflectance of pure silver. It is a figure which shows an example of the shape of an irradiation means in the said embodiment. It is a figure which shows an example of the shape of an irradiation means in the said embodiment. (A) is explanatory drawing which shows an example of the shape of the inner lead manufactured by the etching method. (B) is explanatory drawing which shows an example of the shape of the inner lead manufactured by the etching method. It is explanatory drawing which shows the relationship between the imaging means with respect to a lead frame, and the light emission part of an irradiation means. It is a figure which shows the Example at the time of applying a ring-shaped illumination shape in the said embodiment. It is a figure which shows the Example at the time of applying the dome-shaped illumination shape in the said embodiment. It is a flowchart which shows the whole operation | movement of the defect inspection apparatus in the said embodiment. (A) is explanatory drawing for showing the principle for detecting a defect from a captured image. (B) is explanatory drawing which shows the line profile on the line L1 of (a). It is explanatory drawing which shows the line profile at the time of applying the monochrome camera of a dome shape illumination shape, LED (red), and a line sensor in the said embodiment. It is explanatory drawing which shows a line profile at the time of applying the monochromatic camera of a ring-shaped illumination shape, LED (red), an elevation angle of 50 degrees, and a line sensor in the said embodiment. It is explanatory drawing which shows the line profile at the time of applying the color camera of a dome shape illumination shape, LED (red), an elevation angle of 0 degree-60 degrees, and an area sensor in the said embodiment. From the line profile in the case of applying the line-shaped optical fiber, the elevation angle of 10 °, 30 °, 40 °, 60 °, 70 °, and the color camera of the area sensor in the embodiment according to the comparative example 1, It is explanatory drawing which shows the calculation result of the contrast ratio of a defect part. (A) is explanatory drawing which shows the line profile at the time of applying the color camera of the dome-shaped illumination shape which concerns on the comparative example 2, LED, and an area sensor. (B) is explanatory drawing which shows the calculation result of the contrast ratio of the plating part and defect part of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Irradiation means 11 ... Irradiation means power supply 12 ... Light emission part 20 of irradiation means ... Imaging means 21 ... CCD camera 22 ... Optical system 30 ... Image processing / defect determination means 40 ... Lead frame 41 …… Lead frame (raw material)
42 …… Die pad 43 …… Inner lead 44 …… Outer lead 45 …… Dam bar 46 …… Frame portion 47 …… Plated portion 48 …… Non-plated portion 49 …… Defect portion 50 …… Base 60 …… Display device 70 ...... Step part

Claims (9)

Illuminating at least the plated part with illumination, and creating image data obtained by imaging the reflected light by the imaging means,
The method for inspecting silver plating, wherein the irradiation light from the illumination comprises light having a wavelength of 600 nm or more.   The plating inspection method according to claim 1, wherein the irradiation is an LED or an optical fiber.   The plating inspection method according to claim 1, wherein the illumination has a ring shape or a dome shape.   The plating inspection method according to claim 1, wherein an elevation angle formed by the illumination and the imaging unit via a lead frame is in a range of 0 to 60 °.   The plating inspection method according to claim 1, wherein the imaging unit is a line sensor or an area sensor.   The plating inspection method according to claim 1, wherein the imaging unit is a color camera or a monochrome camera.   The plating inspection method according to claim 1, wherein defect extraction is performed on the image data obtained by the imaging unit by simple binarization, simple difference, or pattern matching.   The red component or the brightness component is extracted from the color image data obtained by the imaging unit, and defect extraction is performed by simple binarization, simple difference, or pattern matching. Inspection method of plating as described.   9. A lead frame inspection method comprising: inspecting a plating applied to a lead frame by the plating inspection method according to claim 1.

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