JP2011528800A - Method and means for measuring the position of a contact element of an electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To disclose a method and means for measuring a position of a contact element (2, 3) of an electronic component utilizing magnification in x, y and z dimensions.
The magnification is determined during a calibration procedure that also establishes the camera-to-camera relationship of the system. Calibration involves the second and third cameras (5,5) as part of the process of obtaining the displacement between the first image point and the second image point to determine the height difference between the different contact elements. 6) Map the image points recorded in the first camera (4) for each point of the contact element to the corresponding image points recorded in.
[Selection] Figure 1

Description

      The present invention relates to the field of machine vision inspection and contact element position measurement on electronic components.

      In the prior art, a method and means for measuring the position of a contact element of an electronic component collect first and second images, respectively, for determination of the relative z-position of the contact element with respect to the bottom surface of the electronic device. Utilize two cameras installed on the triangulation angle. The accuracy of the determined position of the contact element is affected by the triangulation angle between the two cameras installed to record the first and second images. However, since the data to be used is derived from two-dimensional information, there is a limit to the accuracy of the calculated triangulation. Furthermore, the accuracy of the calculated triangulation angle can also be affected by lens distortion, and non-uniform illumination can contribute to errors in the derived equation. Therefore, it would be advantageous to provide an alternative scheme that is more robust during calibration and measurement to provide a three-dimensional position of the measured contact element and is not affected by many uncertain factors.

      The present invention is a method for measuring the respective position of a contact element of an electronic component, comprising the steps of providing the contact element in a calibrated space and illuminating the contact element. Recording a first image of the contact element with a first camera having a first image plane extending substantially parallel to the calibration plane; and a second of the contact element with a second camera. Recording the first image and processing the first image to determine a first image point for each contact element on each contact element, each first image A point is a point located on each contact element, and a step of processing the second image to identify a second image point for each contact element on each contact element. Each said contact The second image point and the first image point with respect to a child correspond to the same point on each of the contact elements; and a third image point in the second image by a position mapping algorithm. Determining a displacement between the second image point and the third image point in the second image, wherein the third image point is applied to the calibration plane. The first image point projected orthogonally.

      The invention relates to means for measuring the position of each contact element of an electronic component, an illumination light source for illuminating the contact element pre-positioned in a calibrated space, a first camera and A second camera, the first camera and the second camera prepared for recording the first and second images of the contact element, respectively, and a processing device, the processing device The first camera for retrieving the position of a first image point in the first image for each contact element and a second image point in the second image for each contact element; Each of the first image point and the second image point for each of the contact elements is connected to a second camera to extract a third image point by a position mapping algorithm in the second image position; Contact Corresponding to the same position on the element, the third image point is projected orthogonally from the first image point and determines the displacement between the second image point and the third point. And a processing device characterized by that.

      An additional third camera can be included to correct image points recorded on the first camera that cannot be recorded on the second camera. The inclusion of a third camera also reduces overall inspection time.

      These and other features, aspects and advantages of the present invention will become more apparent when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings. Well understood and there

Fig. 3 schematically illustrates an illumination and camera setup according to the present invention. Fig. 3 schematically illustrates an illumination and camera setup according to the present invention. Examples of first, second and third images of BGA parts as recorded by the first, second and third cameras are shown respectively. Examples of first, second and third images of BGA parts as recorded by the first, second and third cameras are shown respectively. Examples of first, second and third images of BGA parts as recorded by the first, second and third cameras are shown respectively. 1 shows one example of a multi-layer reticle for a calibration means. FIG. 4 shows one example of an image of a reticle for a calibration means, as recorded by a first, second and third camera. FIG. 4 shows one example of an image of a reticle for a calibration means, as recorded by a first, second and third camera. FIG. 4 shows one example of an image of a reticle for a calibration means, as recorded by a first, second and third camera. 6 illustrates an algorithm for mapping coordinates from a first calibration image to a second calibration image. 1 illustrates a measurement principle according to the invention.

      The method according to the present invention can be applied to electronic components such as BGA (ball grid array) / CSP (chip scale packaging), flip chip devices, leaded devices (QFP, TSOP), and leadless devices (MLP, QFN). Designed for automatic calculation of 3D position of contact elements. The present invention automatically determines the three-dimensional position of a combination of contact elements found on a single device, eg, a BGA / CSP device (1) combination with a leaded device as illustrated in FIG. It is possible to calculate.

      FIG. 1 shows that the electronic component (1) is pre-positioned in a calibrated space in such a way that its contact elements (2) and (3) are illuminated by illumination light sources (7) and (8). Is illustrated. A first camera (4) is placed substantially perpendicular to the calibration plane to record a first image from the bottom of the part, as illustrated in FIG. 2A. A second camera (5) and a third camera (6) are installed to record the second and third images of the side perspective view of the electronic component as illustrated in FIGS. 2B and 2C, respectively. Is done. In the first embodiment of the present invention, only two cameras are required to determine the three-dimensional position of the contact element of the electronic component. If these contact elements cannot be observed from the second image, a third camera is used to record an image of the contact elements of the electronic component. The use of a third camera also allows for a shorter overall image acquisition time. Methods and means for measuring the position of other contact elements recorded in the first and third images of the first and third cameras, respectively, when the third camera is used are Same as the method and means used by the second camera. Accordingly, the operation of the present invention will be described using only the first and second cameras.

      Preferably, cameras 1 and 2 are positioned relative to each other such that both cameras are directed towards the electronic components as illustrated in FIGS. 1A and 1B. Furthermore, as long as all contact elements of the entire electronic component can be observed by at least two different cameras, the cameras 1, 2 and 3 can be arranged in different positions. For example, both FIGS. 1A and 1B show that all three cameras are located at different x, y, and z coordinates such that all possible positions of the contact elements are within the field of view of at least two different cameras. This is illustrated together.

      Before the measurement of the position of the contact element can begin, the device for measuring the three-dimensional contact element is calibrated. Calibration establishes a relationship between a position X1 in the first image and a corresponding position X3 in the second image, ie an image point projected orthogonal to the calibration plane. As illustrated in FIG. 3, a calibration reticle means (9) is used for calibration. It comprises a plurality of predetermined markings represented, for example, by squares whose positions are precisely known. The reticle (9) is made of, for example, a substrate arranged at a position prepared for pre-arranging electronic components to be measured. The substrate consists, for example, of multiple layers of glass that are preferably arranged in an array manner on the base glass layer. Squares are printed on each of these glass layers using a very accurate screen printing process. The thickness of all these upper glass layers is accurate, and the correctly printed markings are clearly defined for easy detection by the camera. Although not illustrated, it is possible that the previously described calibration reticle means could be replaced with other calibration reticle means such as a reticle with a vertical structure protruding from the layer at exactly known locations.

      In order to obtain an accurate calibration, the location and dimensions of the squares printed on the calibration reticle means are preferably known to an accuracy of 0.1 microns. The area and volume measured by the calibration reticle means define a space that can be calibrated in the x, y and z directions. Thus, when larger spaces and areas are covered by the calibration reticle means in the x, y and z directions, the larger spaces can be used to make measurements on larger electronic components. When the measurement is performed later, it is not necessary that the plane in which the contacts are located is placed exactly on the calibration surface (11). As long as the plane in which the contacts are located is within an established calibrated space, measurements can be performed.

      4A, 4B, and 4C illustrate first, second, and third images, respectively, of calibration reticle means that are recorded by the first, second, and third cameras, respectively. Since individual markings, such as squares on the calibration reticle means, can be identified, the mapping algorithm allows mapping between both images as illustrated diagrammatically later in FIG. To be determined through a calibration procedure. As shown in FIGS. 4A and 4B, respectively, the first camera (4) and the second camera (5) each record its calibration image of the calibration reticle means. As shown in FIGS. 4A and 4B, the calibration of the first image (FIG. 4A) and the second image (FIG. 4B) as recorded by the first camera (4) and the second camera (5). Includes determination of the location of the same square (10) (11) or similar feature. The position mapping algorithm is derived from the position for each corresponding feature determined in each first and second image. For example, as illustrated in FIG. 5, the coordinates of a point (111) in the first image are mapped to its corresponding point (111 ') in the second image. Therefore, plane (11) is the calibration plane because its surface features are used to map the pixels in the first image plane to the second image.

      According to FIG. 5, a bilinear interpolation technique is used to determine the coordinates for all positions between any two markings. For example, the position of the point X1 in the first image is expressed as a ratio of dx and dy, and coordinates (111), (112), (221) and formed by a rectangular matrix on the first image (222) is considered. The point X3 in the second image is a point projected orthogonally from the point X1 in the first image, and the former is represented by the ratio of dx 'and dy'. The position mapping algorithm between the first image point in the first image and the image point in the second image is such that the image point in the second image is orthogonal to the calibration plane from the first image point. Are obtained by determining the relationship with respect to dx and dx ′ and the relationship with respect to dy and dy ′. For example, the position mapping algorithm for X1 in the first image plane and X3 in the second image plane is the relationship for dx and dx 'to the x-coordinate and the relationship for dy and dy' to the y-coordinate. A position mapping algorithm is then used during the measurement to determine a point in the second image plane that is the first image point projected orthogonal to the calibration plane.

      Referring to FIGS. 3, 4A, 4B and 5, the z-magnification is the respective pixel coordinate in the first and second images, respectively, for a feature such as a square (10) on the calibration reticle means. Determined by first determining X1 and X2. X3 is a point projected orthogonally from the point X1 to the calibration plane using the position mapping algorithm. Since the z-distance between X2 and X3 is known accurately, the respective z-magnification in the second image (4B) and the third image (4C) can be determined. For example, assuming that the distance between X2 and X3 is 10 mm and that their corresponding distance on the second image is 25 pixels, the z-magnification is 10 mm / 25 pixels = 0.4 mm / pixel Will.

      After completing the calibration procedure, an xy coordinate position mapping algorithm and z-magnification were obtained to determine the position of the contact element on the part in the first and second images. In addition, the distance between the contact elements X, Y and Z axes can be determined from the respective x, y and z-magnification. Since the position is accurately determined by the calibration reticle means, the position of the contact element can also be accurately determined in microns. The calibration procedure also allows camera-to-camera calibration to be performed and establishes a relationship between the first camera (4) and the second camera (5). The relationship of the third camera to the first camera is also established in the manner described herein.

      Now that the space for measurement has been calibrated and the first and second camera setups have been described, the measurement principle according to the present invention will be described with the help of FIG. A third camera (6) is installed with respect to the first camera (4) in the same manner as the second camera. Assume that the electronic component is brought into a calibrated space and that one of its contact elements is located at point P relative to the calibration plane, p. The first camera records a first image of the contact element and selects the first point P. The position of the first image point X1 relative to the first point P in the first image of the contact element is determined.

      A second camera (5) records a second image of the contact element by point P, and point P is identified as a second image point X2 in the second image. Point P is projected orthogonally to the calibration plane, p, which gives the second point P ', using a position mapping algorithm. In the second image, the third image point X3 is the image point at the position P ′ at that time. If the contact element P will be localized in the calibration plane p, X3 is the expected position. The position of the point X3 in the second image is determined by a position mapping algorithm. The displacement between X2 and X3 is due to the difference in height that the actual contact element is to be measured, usually not exactly on the calibration surface, DELTA. This is due to the fact that z is placed. Following the foregoing, the displacement DELTA. z is determined by the product of the distance between X3 and X2 (ie DELTA.z ') and the z-magnification in the Z-axis of the second image.

      Since the present invention allows the measurement of points within a calibrated space, the present invention can be used to measure the distance between any two points as long as the two points are located within the calibrated space. Utilizing the invention will be apparent to those skilled in the art.

      Thus, this can be used to measure the distance between the contact elements of the component and the distance of the contact elements from the calibration surface in the calibrated space, which can be an integrated circuit on which the contact elements are located. The utility and utility of such systems and methods will be apparent to those skilled in the art. Accordingly, the foregoing description is illustrative and is in no way limiting of the essence of the invention itself, which claims its scope and embodiments as follows.

DESCRIPTION OF SYMBOLS 1 Electronic component 2, 3 Contact element 4 1st camera 5 2nd camera 6 3rd camera 7, 8 Illumination light source 9 Calibration reticle means 10, 11 Square 11 Calibration surface 111 Point 111 '1st in 1st image Its corresponding points 111, 112, 221, 222 in the image of 2

Claims (12)

A method for measuring the respective position of a contact element (2, 3) of an electronic component comprising the following steps:
Providing the contact elements (2, 3) in a calibrated space;
Illuminating the contact element (2, 3);
Recording a first image of the contact element (2, 3) with a first camera (4) having a first image plane extending substantially parallel to the calibration plane;
Recording a second image of the contact element with a second camera (5);
Processing the first image to determine a first image point for each contact element (2, 3) on each contact element (2, 3), each of the first elements; A step in which the image point is located on each of the contact elements (2, 3);
Processing said second image to identify a second image point for each said contact element (2, 3) on each said contact element (2, 3), each said contact element The second image point and the first image point for (2, 3) correspond to the same point on each contact element (2, 3);
Determining a third image point by a position mapping algorithm in the second image;
Determining a displacement between the second image point and the third image point in the second image, wherein the third image point is projected orthogonally to the calibration plane. And the step of being the first image point.       The method of claim 1, wherein the step of determining a displacement is by multiplying z-magnification and coordinate differences of the second image point and the third image point. how to.       The method according to claim 1, further comprising deriving the position mapping algorithm for a specific relative position between the first and second cameras (5).       2. The method of claim 1, further comprising deriving a z-magnification for determining the displacement of the image point projected orthogonally to the second image point.       The method of claim 1, further comprising determining a displacement between any two points within the calibrated space. Means for measuring the position of each contact element (2, 3) of the electronic component,
An illumination light source (7, 8) for illuminating the contact elements (2, 3) pre-positioned in a calibrated space;
A first camera (4) and a second camera (5), the first camera (1) prepared for recording the first and second images of the contact elements (2, 3), respectively; 4) and the second camera (5);
A processing device, said processing device for each said contact element (2,3) said first image point in said first image and said first for each said contact element (2,3). Connected to the first camera (4) and the second camera (5) for extracting the position of the second image point in the second image, the first to the contact elements (2, 3). And the second image point correspond to the same position on each contact element (2, 3) from which a third image point is extracted by a position mapping algorithm within the second image position, A process in which a third image point is projected orthogonally from the first image point and determines a displacement between the second image point and the third point. A device.       7. Means for measuring the position of each contact element (2, 3) of an electronic component according to claim 6, wherein the processing device comprises z of the second image point and the third image point. Means for determining said displacement by multiplying by magnification and coordinate difference;       7. A means for measuring the position of each contact element (2, 3) of an electronic component as claimed in claim 6, wherein the image is recorded by the first and second cameras (4, 5). Calibration reticle means (9), and the processing device from the image of the calibration reticle means relative to a specific relative position between the first camera and the second camera (4, 5) A means for deriving a location mapping algorithm.       9. A means for measuring the position of each contact element (2, 3) of an electronic component according to claim 8, wherein the calibration reticle means (9) has a base layer with the characteristics disposed therein and Means comprising: a plurality of layers having features, wherein the plurality of layers have precisely known thicknesses and are accurately positioned relative to the features in the base layer.       9. A means for measuring the position of each of the contact elements (2, 3) of the electronic component according to claim 8, wherein the processing device comprises the second image point and the third image point. Means for deriving a z-magnification for determining the displacement.       8. A means for measuring the position of each contact element (2, 3) of an electronic component according to claim 7, wherein the processing device is adapted to displace any two points in the calibrated space. Means for determining.       7. A means for measuring the position of each of the contact elements (2, 3) of the electronic component according to claim 6, further connected to the processing device for recording a third image of the contact elements. A third camera (6), wherein the third image has a fourth image point and a fifth image point, and the fifth image point is orthogonal to the first image point. Projected points that are not recorded in the second image and the processing device determines a displacement between the fourth image point and the fifth image point. Means characterized by.

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