WO1996011377A1

WO1996011377A1 - Illuminator for inspecting appearance of device and automatic apparatus for inspecting appearance of device using the illumination device

Info

Publication number: WO1996011377A1
Application number: PCT/JP1995/002043
Authority: WO
Inventors: Aritomo Kikuchi; Hisao Hayama
Original assignee: Advantest Corporation
Priority date: 1994-10-06
Filing date: 1995-10-05
Publication date: 1996-04-18
Also published as: JPH08105722A; CN1138897A; KR960706627A

Abstract

An illuminator most suitable when the appearance of a small precision device is inspected, and an apparatus for automatically inspecting the appearance of a device using this illuminator. An illuminator including an illumination frame having a large number of light-emitting devices the luminance of which can be regulated and which are disposed around a camera lens, and an illumination control section for regulating the luminance of each light-emitting device, is prepared. An automatic device appearance inspection apparatus comprises this illuminator, a camera such as a CCD camera for converting an image to pixel data and outputting the pixel data, an image processor for converting the pixel data into image data, an arithmetic processor for measuring the size, position, etc, of a specific portion of the appearance of a tested device, and a display for receiving the image data from the image processor and displaying a corresponding image. The illumination control section is operated in accordance with the result of imaging by the camera so as to control the luminance of each light-emitting device, and high precision appearance inspection can be made by optimizing illumination for the specific area of the tested device.

Description

Description Illuminator for device appearance inspection and automatic device appearance inspection device using this illuminator

The present invention relates to an illuminator used for inspecting the appearance of electronic components (hereinafter, referred to as a device) such as a semiconductor device, a filter, and a vibrator, and an automatic device appearance inspection apparatus using the illuminator. The present invention relates to a illuminator useful for inspecting the appearance of Ic, which is a typical example of a semiconductor device, for example, a surface mount LSI (large-scale integrated circuit), and an automatic device appearance inspection apparatus.

It should be noted that this type of illuminator is used not only when a human visually inspects the appearance of a device but also when a visual inspection of the device is performed by an automatic appearance inspection apparatus having an image processing unit. In the following, the case where the IC is used as the light source of an automatic device appearance inspection device is taken as an example, and the case where the IC is illuminated and its appearance is inspected for simplicity is described. It goes without saying that it can be used to illuminate any device, including devices such as filters and vibrators, and inspect their appearance. Background art

For example, testing of ICs including LSIs involves testing at the wafer stage in the manufacturing process and testing on finished products with packages. Finished product testing includes electrical characteristics testing and appearance testing. The appearance test may be performed by human visual inspection or by using an automatic appearance inspection device. In any case, the IC must be illuminated. Conventionally, lighting used for visual inspection of ICs is lighting that illuminates the entire IC under test to a certain brightness, both in visual inspection and when using an automatic visual inspection device. Constant illumination was performed with a light source from obliquely above or from the side. Conventionally, the package is relatively large and the number of input / output lead bins is small, so that the lead pin interval (pitch) is relatively wide and the precision is small. The reason was that the above-mentioned constant lighting was sufficient for both the visual inspection and the automatic inspection because the degree was not severe.

An automatic appearance inspection apparatus generally has an image processing unit similar to an image processing apparatus. FIG. 5 shows an example of processing image data in a conventional image processing apparatus. The camera unit 50 converts the photographed image into digital pixel data of a total of 302,000 pixels, for example, 62 pixels in the horizontal axis and 484 pixels in the vertical axis, and outputs the data. This pixel data is stored directly in the image memory 51, or is stored in the image memory 51 via a filter 52 and a LUT (Look-Up Table) 53.

The LUT 53 is a conversion table for selecting colors to be displayed on a television (TV) monitor 18 or the like. The input data value is used as the address, and the output data corresponding to the input data is output. This is a pre-written memory. The LUT 53 data conversion function is used to perform binarization, pre-processing of gray-scale images, and conversion processing of display images. The filter 52 has a function of emphasizing the edge and preprocessing in cooperation with the data output from the shading memory 58 when, for example, the periphery of the IC to be tested is blurred. I have. The window memory 55 is a memory used for drawing a window on the screen of the TV monitor 18. The graphic memory 56 is a memory used to display the display of the measurement results as a graph or as a work area. The character memory 57 is a memory mainly for displaying characters, and is also used for editing programs and displaying tally results.

The display control unit 54 is a control unit that directly processes pixel data from the camera unit 50 or processes pixel data from the image memory 51 and displays an image on the TV monitor 18. . The display control unit 54 displays an image using the data of the window memory 55, the graphic memory 56, and the character memory 57 depending on an instruction.

When using an automatic appearance inspection device for a device consisting of an image processing device using such a camera, inspection can be performed with a conventional device by automatically adjusting the brightness with the above-mentioned constant illumination. Met.

However, recent market demands have led to miniaturization of equipment and high-density mounting of components, miniaturization of devices, and an increase in surface-mount packages. Especially super L In the case of SI QFP (Quad Flat Package), the vertical and horizontal dimensions are 1 O mm X 1 O mm to 3 O mm x 3 O mm, and lead pins are arranged on four sides of this package, and lead pins on each side The number is very large, from 8 to 76. In addition, the lead pitch width is very narrow, from 0.3 mm to 0.8 mm, and the thickness is about 2 mm to 1 Omm.

Surface mounting packages such as QFP and SOP (Small Outline Package) are soldered directly to the surface of the printed wiring board, so the bottom surface of the tip of the lead pin must be flat and the lead pitch width Must be at regular intervals. For such fine and accurate appearance inspections, the conventional fixed lighting is not enough, and more detailed lighting is required. The reason for this is that even if the difference in the light reflection state of the lead bin is known with the conventional fixed lighting, it is determined whether the bottom surface of the leading end of the lead bin is flat or the lead pitch width is constant. This is because it was not possible to determine whether or not it was. B month

An object of the present invention is to provide a compact device visual inspection illuminator that can illuminate a device evenly and easily illuminate from a specific direction.

It is another object of the present invention to provide a small and high-resolution automatic device appearance inspection apparatus provided with the above-mentioned illuminator, which can automatically and accurately inspect the appearance of a device.

The illuminator for visual inspection of a device according to the present invention comprises: an illumination frame provided with an opening for arranging a camera or an operator's eyes at substantially the center; It is composed of a number of arranged light-emitting elements whose luminance can be controlled, and an illumination control unit that can selectively control the luminance of each light-emitting element. When illuminating the device under test (generally called a DUT), if the overall illumination is uneven, adjust the brightness of each light emitting element to eliminate the unevenness. For some DUTs, illumination from a slightly lower position provides better reflection at the measured (observed) location. In this case, for example, the upper light emitting element is turned off. Then, the brightness is controlled so that only the lower light emitting element is turned on. The opposite lighting method may be used. Thereby, the shading can be sharpened. In this specification, the luminance adjustment or control includes not only increasing or decreasing the brightness of the light emitting element, but also turning on or off the light emitting element. This brightness adjustment may be performed manually or automatically.

If the DUT is horizontal, it should be horizontal, if it is vertical, it should be vertical, and a quadrilateral similar to DUT should be used. This is to spread the lighting over the entire surface of DUT. The central opening may be as large as the line of sight or the lens of the camera. The dimensions of the frame are determined by the size of DUT.

The light emitting element is not limited as long as it is a small light emitter such as an LED (Ught Emitting Diode), a fluorescent tube or a white lamp. The light emitting elements are arranged in a certain range of the lighting frame. When the light emitting elements are arranged regularly in rows and columns, uniformity of illumination can be obtained, and control is easy. In the case of a DUT having a specific property in light reflection, the number of light emitting elements at the top, bottom, or left may be changed. It is desirable that the brightness of each light emitting element can be adjusted by voltage or current.

The lighting control unit that controls the luminance of each light emitting element controls the luminance including turning on and off the individual light emitting elements. Initially, all light-emitting elements are turned on with the same brightness, and if there is uneven brightness on the DUT observation surface, the brightness of the light-emitting elements is controlled in row units, column units, or block units to eliminate unevenness. Here, one block is composed of a plurality of light emitting elements. Finally, brightness control may be performed for each light emitting element. This brightness control can be performed either manually or automatically. In the case of automatic brightness control, it is recommended that the brightness be controlled by a fixed control sequence and the control sequence be stopped at the optimum value. The lighting control unit may be provided adjacent to the lighting frame, or may be provided at a separate location.

An illuminator configured in this way can illuminate the DUT uniformly, or illuminate a specific location with strong illumination, for example, with a large number of lead pins and a very large lead pitch. Even with a narrow IC, the IC can be illuminated so that the flatness of the tip of the lead pin and the lead pitch can be accurately measured. On the other hand, an automatic device appearance inspection apparatus according to the present invention includes: A camera that converts and outputs pixel data of the device under test, an image processing unit that processes pixel data input from this camera and converts it into image data, and an external view of the device under test according to preset inspection items And a display device for displaying an image corresponding to the image data input from the image processing unit.

The above-mentioned force film is preferably a CD (Charge Coupled Device) force film. This is because analog-to-digital (AZD) conversion is easy, but it can be used with ordinary cameras. The AZD conversion is preferably performed in the camera. High sensitivity is desired. This is because we want to capture light and dark of light reflection clearly. The lens of this camera is placed in the opening at the center of the lighting frame of the illuminator, facing the DUT.

The pixel data obtained by the camera is sent to the image processing unit and converted into image data. The image processing section may have the same configuration as the conventional image processing apparatus, but it is desirable to install the above-mentioned illumination control section inside. This is because the lighting control is performed using the image data processed by the image processing unit and the calculation data by the calculation processing unit. The arithmetic processing unit performs various arithmetic processes based on the image data and outputs the results. The image data and, if necessary, the results of the calculation processing are sent to the display device (TV monitor), and the display device displays the corresponding DUT image.

The processing unit performs various measurements according to the preset inspection (measurement) items, outputs the measurement results from the measurement result output terminal, and displays and prints them. The inspection items vary depending on the DUT. For example, in the above-described LSI of QFP, there are the number of lead pins, the lead pitch width, the flatness of the lead pins, and the like. ¾ί f ^ na ^ sun moon

FIG. 1 is a schematic perspective view showing one embodiment of a device appearance inspection illuminator according to the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of an automatic device appearance inspection apparatus according to the present invention provided with the device appearance inspection illuminator of FIG. 1 together with an IC under test.

Fig. 3 shows the illumination state of one lead pin of the IC imaged using the device appearance inspection illuminator of Fig. 1, (A) is a side view showing a good lead pin, and (B) is (A). ) Is a perspective view from the left side, (C) is a side view showing a defective lead pin, and (D) is a perspective view from (C) as seen from the left side.

FIG. 4 is a flowchart for explaining an example of an inspection method using the automatic device appearance inspection apparatus according to the present invention.

FIG. 5 is a schematic configuration diagram for explaining a flow of image data of an example of a conventional image processing apparatus. Of applying the invention

INDUSTRIAL APPLICABILITY The illuminator for device appearance inspection and the automatic device appearance inspection apparatus according to the present invention can be used to illuminate not only semiconductor devices but also all devices including devices such as filter elements and to inspect their appearance. In the following, an embodiment used for illuminating an IC, which is a typical example of a semiconductor device, and inspecting its appearance, particularly the appearance of lead pins, will be described.

FIG. 1 is a schematic perspective view showing one embodiment of a device appearance inspection illuminator according to the present invention. The illuminator for device appearance inspection according to the present invention comprises: an illumination frame 10 provided with an opening for arranging a camera or an operator's eyes substantially at the center; It is composed of a number of light-emitting elements 19 that can be controlled in luminance arranged in the periphery and an illumination control unit 11 that can selectively control the luminance of each light-emitting element 19.

Since the illuminator of the present embodiment is configured to illuminate an IC such as the above-described QFP super LSI, the illumination frame 10 is horizontally elongated as shown in FIG. It is formed in a horizontally long rectangular quadrilateral similar to. In this embodiment, the lens of the camera 9 is arranged in an opening formed in the center of the rectangular frame 10, and a number of light emitting elements 19 are arranged around the opening around the opening. Are arranged.

LED light-emitting elements are used as light-emitting elements 19, and these light-emitting elements 19 are regularly arranged in rows and columns, but the upper part of the opening is thinned out to about half the number compared to the lower side and both sides. State (almost every other). The reason for the regular arrangement is that it is easier to control the brightness. The reason why the number of the light emitting elements on the upper side is reduced is that, in this embodiment, the main purpose is to measure the appearance of the lead pins of the IC, so that it is easier to inspect the IC by irradiating the IC with strong light from a little below. As described above, it is preferable that the arrangement of the light-emitting elements 19 be arranged so as to be in an optimal illumination state in consideration of the DUT appearance inspection items. Of course, the luminance may be controlled by arranging the light emitting elements without thinning.

Since the brightness of one LED is about 200 O mcd (milli-candela), the number of LEDs depends on the size of the DUT, the distance to the DUT, test items, test accuracy, and the like. It is better to decide. Usually, it is sufficient to use 40 to 60 LEDs. Further, the LED emission color is preferably a color that increases the sensitivity of the camera.

The lighting control unit 11 is provided adjacent to the frame 10 and performs initial setting of lighting and correction of lighting based on measurement results. In other words, in the initial setting, the calibration target is placed at a measurement position at a certain distance in front of the illuminator, and the target is illuminated. If the image is good, the value is set to the optimum value, and if the image is bad, the value is set to a predetermined fixed sequence. The brightness of each light emitting element is turned off and turned on, and the control is performed to stop at the optimum value. In addition, it is configured so that when a failure occurs in the measurement result of each DUT, it can be readjusted so that it can be measured in the optimum state each time.

FIG. 2 is a schematic configuration diagram showing an embodiment of an automatic device appearance inspection apparatus according to the present invention provided with the device appearance inspection illuminator of FIG. 1 together with an IC under test. The IC under test 20 is mounted and fixed on a rotating stage 21 rotatably arranged on the measuring table 22. In this embodiment, the IC 20 is a QFP LSI, and since the lead pins are on the four sides of the package, it is necessary to measure all four sides.Each time the external appearance of the rotary stage 21 is measured, Turn 90 degrees and measure the appearance of the lead pins on the next side. Then, the appearance inspection is completed by measuring the appearance of the four lead pins.

The camera 9 and the illuminator are opposed to the IC 20 under test and are set at a fixed distance. The illuminator illuminates the IC 20 appropriately in the manner described above, and the camera 9 converts the captured screen into pixel data and sends it to the image processing unit 12. The camera 9 is a CCD camera, which immediately converts the imaging screen into an AZD, and in this embodiment, 4 8 4 X 6 4 points Is converted to pixel data. The distance resolution can be increased by appropriately selecting the distance between the camera 9 and the IC 20 and the magnification of the lens. For example, if 100 mm pixels are imaged at an interval of 10 mm of IC 20, a high resolution of 0.1 mmZ pixels can be obtained. In this embodiment, 8-bit image data is used. ^! ! It is possible to obtain a high resolution (experience value), that is, a high resolution of about 0.02 mm.

The image processing unit 12 receives the pixel data sent from the camera 9 through the pixel data input terminal 13a, and performs processing to increase the density of the image. This process facilitates the measurement position determination. An example will be described with reference to FIG. In FIG. 3, only one lead pin of the IC under test IC 20 is shown for simplicity. FIG. 3 (A) is a side view when the lead pin of the IC under test 20 is a good lead pin 25. It can be seen that the bottom surface of the tip of the lead pin 25 is flat. FIG. 3 (B) is a front view of FIG. 3 (A), showing a case where the light is strongly irradiated from slightly below IC 20. Due to this illumination, strong reflected light enters the camera 9 from the tip (end face) of the lead pin 25, which is displayed in black in FIG. The number of pixels in the white (bright) portion determines the width of the lead bin 25, and also determines the position of the center point. Further, although not shown in FIG. 3, the interval between adjacent lead focuses, that is, the lead pitch width can also be obtained.

Fig. 3 (C) is a side view showing an example in which the lead pin of the IC under test 20 is a defective lead pin 26, and the tip of the lead pin 26 is bent slightly upward. The bottom surface is not flat. Fig. 3 (D) is a front view of (C), which also shows a case where the illumination is strongly applied from slightly below IC20. In the case of the defective lead pin 26, the reflected light from the tip (end face) is not incident on the camera 9, and is displayed black (dark) on the TV monitor 18. Therefore, neither the width nor the position of the lead pin 26 can be determined. Therefore, it is determined that the product is defective, but there are still cases where it is desired to know the position of the lead pin 26. In this case, the illumination control section 11 is operated to slightly increase the illumination from above. As a result, strong reflected light from the tip of the defective lead pin 26 is incident on the force camera 9, and the tip position of the defective lead pin 26 is also adjusted in the image processing unit 12. It is confirmed. The flatness (step) with the position of the good lead pin 25 can also be determined.

The image processing unit 12 processes the pixel data from the camera 9 as described above and converts it into an image data to emphasize the shading or to arbitrarily measure an arbitrary measurement portion of the IC under test through the LUT 53. Change the color display, display the window, or display the characters, and display the image on the TV monitor 18. The output signal of the image processing unit 12 is supplied to the TV monitor 18 through the TV image output terminal 17.

The arithmetic processing unit 14 determines the quality of the lead pin based on the image data of the image processing unit 12, and measures the lead pin width, the lead pitch width, and the flatness (step). The calculation result can be displayed on the TV monitor 18 and can be output from the measurement result output terminal 16 to the outside. The measurement items and the procedure of the processing method are input from the setting input terminal 15 to the arithmetic processing unit 14. The arithmetic processing unit 14 also controls the entire system. The control data from the arithmetic processing unit 14 is output to the illuminator via the illuminator control data output terminal 13b. A setting button or numeric key may be provided in the arithmetic processing unit 14 itself, and the measurement item or the procedure of the processing method may be input from the button or key. It is more convenient to provide the lighting control unit 11 in the arithmetic processing unit 14. FIG. 4 is a flowchart showing an example of an operation when a defective appearance IC is detected in the measurement procedure. The IC under test 20 is fixed on the rotating stage 21 and the measurement of the reflected light starts with the signal of the measurement start (step 30). In the next step 31, it is determined whether or not the measurement points set in advance have been measured, that is, whether or not all the lead pins have been measured. If the result of the judgment in step 31 is YES, the measurement result of the IC is output in step 32, and the visual inspection ends (step 33). If the result of the determination in step 31 is NO, in step 34 the lighting control unit 11 is driven to control the brightness of the light emitting element 19. For example, change the lighting position of the LED. Subsequently, in step 35, re-measurement of the lead pin which cannot be measured is executed, and it is determined in step 36 whether or not the measurement was successful. If the result of the determination in step 36 is YES, the measurement result of the IC is output in step 32, and the visual inspection ends (step 33). If the result of the determination in step 36 is N〇, return to step 34 again, change the LED lighting position, and stop measurement in step 35. Perform re-measurement of available lead pins. This re-measurement is limited to, for example, three times, and the number of re-measurements is counted in steps 37 and 38.If the number of re-measurements exceeds three times, the process proceeds to step 39. Yes (Step 40).

As is apparent from the above description, according to the present invention, it is possible to easily perform an appearance inspection of a device that has recently become very small, highly accurate, and miniaturized. The illuminator for device visual inspection according to the present invention can control the brightness of each light emitting element according to the observation result by arranging a large number of light emitting elements which can observe the DUT, for example, a camera and can adjust the brightness. Therefore, illumination unevenness can be eliminated, and irradiation from a specific direction can be easily performed, so that irradiation and observation of a specific part of the DUT can be performed correctly. Therefore, an illuminator that is indispensable for observing minute parts can be provided.

Since the device appearance automatic inspection device using this illuminator has an irradiator that can irradiate the measurement part of the DUT from any direction, it is possible to sharpen the density of the measurement part of the DUT captured by the camera, Automatic measurement has become easier. Also, by increasing the number of pixels in the image data, the distance resolution can be reduced to 0.1 mmZ pixels or less, enabling ultra-precision measurement.

As described above, the present invention is optimal for miniaturized appearance inspection of devices such as semiconductor devices, filters, and vibrators, and has a great technical effect.

Claims

The scope of the claims

1. An illumination frame with an opening for placing a camera or an operator's eye at approximately the center,

A number of light-emitting elements that can be controlled in brightness arranged around the opening of the lighting frame;

A lighting control unit capable of selectively controlling the brightness of each of the light emitting elements.

2. The illuminator for device appearance inspection according to claim 1, wherein the light emitting element is an LED light emitting element.

3. An illumination frame in which an opening for placing a camera or an operator's eyes is formed substantially in the center, and a number of light sources with brightness controllable arranged around the opening of the illumination frame. An illuminator for device appearance inspection, comprising: an element; and an illumination control unit that can selectively control the luminance of each of the light emitting elements.

A camera that images the device under test, converts the imaged screen into a large number of pixel data, and outputs the data.

An image processing unit that processes pixel data input from the camera and converts the pixel data into image data;

An arithmetic processing unit for measuring the appearance of the device under test in accordance with a preset inspection item;

A display device for displaying an image corresponding to the image data input from the image processing unit.