KR20110043593A - A method and means for measuring positions of contact elements of an electronic components - Google Patents

Abstract

The present invention relates to a method and means for measuring the position of contact elements (2, 3) of an electronic component using scaling factors in x, y and z dimensions. The scaling factor is determined during the calibration procedure to establish the camera-to-camera relationship of the system. The correction is recorded in the first camera 4 for each point of the contact element as part of the process for obtaining the displacement between the first image point and the second image point to determine the height difference between the different contact elements. The captured image points into corresponding image points recorded in the second and third cameras 5 and 6.

Description

A method and means for measuring the position of each of the contact elements of an electronic component TECHNICAL FIELD

FIELD OF THE INVENTION The present invention relates to the field of machine vision inspection and measurement of contact element positions of electronic components.

In the prior art, a method and means for measuring the position of contact elements of an electronic component are adapted to triangulation angles to capture first and second images respectively for determination of the relative z-position of the contact elements relative to the bottom surface of the electronic device. Use two cameras set up. The accuracy of the determined position of the contact elements is affected by the triangulation angle between the two cameras set up to record the first and second images. However, there is a limit to the accuracy of the captured triangulation because the data used is derived from 2D information. In addition, the accuracy of the calculated triangulation angle can be affected by lens distortion and add errors to the equations in which non-uniform illumination is induced. Thus, it is desirable to provide another method that is more robust and unaffected by many uncertain factors during calibration and measurement to provide three-dimensional positions of measured contact elements.

The present invention relates to a method for measuring the angular position of a contact element of an electronic component, the method comprising positioning the contact element in a calibrated space, 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 a calibration plane, and recording a second image of the contact element with a second camera, respectively Processing a first image to determine a first image point for each contact element on a contact element of the first image processing step, wherein the first image point is a point located on each contact element; Processing the second image to identify a second image point for each contact element on each contact element, wherein the first image for each contact element is obtained. The second point and the second image point correspond to the same point on each contact element, determining a third image point in the second image by a location mapping algorithm, and Determining a displacement between the second image point and the third image point, wherein the third image point is a first image point projected perpendicular to the correction plane.

The invention also relates to means for measuring the respective positions of the contact elements of the electronic component, comprising: an illumination source for illuminating a contact element pre-positioned in a calibrated space, a first camera and a second camera, and a first of the contact elements. And a first camera and a second camera provided for recording the second image, respectively, and a processing device, the processing device being connected to the first camera and the second camera, the first image for each contact element within the first image. Retrieve the position of the first image point and the second image point in the second image for each contact element, retrieve the third image point by a location mapping algorithm at the second image position, and the second image point and the third Determine the displacement between the points, and the first and second image points for each contact element are compared to the same point on each contact element. And, a third image point is a position projected vertically from the first image point.

An additional third camera may be included to compensate for image points recorded in the first camera that cannot be recorded in the second camera. Including a third camera reduces the overall inspection time.

These and other features, aspects, and advantages of the present invention will be best understood from the following detailed description with reference to the accompanying drawings. Like numbers refer to like parts throughout.

1a and 1b schematically show the arrangement of a light and a camera according to the invention;
2A, 2B and 2C show examples of first, second and third images of BGA parts recorded by the first, second and third cameras, respectively.
3 shows an example of a multi-layered reticle for the correction means.
4A, 4B and 4C show examples of images of the reticle for the correction means recorded by the first, second and third cameras.
5 shows a mapping algorithm of coordinates from a first corrected image to a second corrected image.
6 shows a measuring principle according to the invention;

The method according to the invention is the contact of electronic components such as Ball Grid Array (BGA) / Chip Scale Packaging (CSP), flip-chip devices, leaded devices (QFP, TSOP) and leadless devices (MLP, QFN). For automatic calculation of the three-dimensional position of the elements. The present invention can automatically calculate the three-dimensional position of the combination of contact elements found on a single device, such as a combination of a BGA / CSP device 1 and a lead device, for example as shown in FIG.

1 shows an electronic component 1 pre-positioned in a calibrated space in such a way that the contact elements 2 are illuminated by the illumination sources 7 and 8. As shown in FIG. 2A, the first camera 4 is positioned almost perpendicular to the correction plane to record the first image from the bottom of the part. The second camera 5 and the third camera 6 are positioned to record the second and third images of the side perspective view of the electronic component as shown in Figs. 2B and 2C, respectively. In the first embodiment of the present invention, only two cameras are required to determine the three-dimensional position of the contact elements of the electronic component. The third camera is used to record an image of the contact elements of the electronic components when these contact elements are not visible from the second image. Using a third camera can shorten the overall image acquisition time. When a third camera is used, the method and means for measuring the position of the other contact elements recorded in the first and third images of the first and third cameras may differ from the methods and means used by the first and second cameras. same. Thus, the operation of the present invention is described as using the first and second cameras.

Preferably, the cameras 1, 2 are arranged relative to each other in such a way that both cameras face the electronic components, as shown in FIGS. 1A and 1B. In addition, the cameras 1, 2, 3 can be arranged in different positions as long as all the contact elements of the entire electronic component can be viewed by at least two different cameras. For example, FIGS. 1A and 1B show that all three cameras are located at different x, y, z coordinates such that all possible positions of the contact elements are within the view of at least two different cameras.

The device for measuring the three-dimensional contact element is calibrated before the measurement of the position of the contact elements can be started. The correction establishes a relationship between the position X1 in the first image and the corresponding position X3 in the second image, that is, the image point projected perpendicular to the correction plane. The correction reticle means 9 shown in FIG. 3 is used for correction. This includes a number of predetermined markings represented by squares, the location of which is exactly known. This reticle 9 consists, for example, of a substrate which is placed in a position provided for prepositioning the electronic component to be measured. The substrate is composed of, for example, a plurality of glass layers arranged in an array manner on the base glass layer. Squares are printed on each of these glass layers using a very sophisticated screen printing process. The thickness of these glass layers is accurate, and the finely printed markings are clearly defined so that they can be easily detected by the camera. Although not shown, the aforementioned correction reticle means may be replaced by other correction reticle means, such as a reticle having a vertical structure that projects from precisely known points.

In order to obtain accurate correction, it is known that the position and size of the rectangle printed on the correction reticle means is preferably a precision of 0.1 micron. The area and volume spanning the correction reticle means define a space that can be corrected in the x, y, z directions. Thus, larger spaces are available for measurement for larger electronic components when larger spaces and areas are covered by corrective reticle means in the x, y, z directions. When the measurement is performed later, the surface on which the contact is located does not need to be exactly positioned on the correction surface 11. The measurement can be performed as long as the surface on which the contact is located is within the established correction space.

4A, 4B and 4C show the first, second and third images of the correction reticle means recorded by the first, second and third cameras, respectively. Since individual markings, such as a rectangle on the correction reticle means, can be identified, the mapping algorithm is determined through a correction procedure that enables mapping between the two images as shown in FIG. 5. As shown in Figs. 4A and 4B, the first camera 4 and the second camera 5 record the corrected images of the correcting reticle means, respectively. As shown in FIGS. 4A and 4B, the correction is performed by the same quadrangle in the first image (FIG. 4A) and the second image (FIG. 4B) as recorded by the first camera 4 and the second camera 5. 10, 11) or similar features. The position mapping algorithm is derived from the positions for each corresponding feature determined in each of the first and second images. For example, as shown in FIG. 5, the coordinates of the point 111 in the first image are mapped to the corresponding point 111 ′ in the second image. Thus, plane 11 is a correction plane since features on its surface are used to map 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 point X1 in the first image is represented by dx and dy, and may be considered for coordinates 111, 112, 221 and 222 formed by an orthogonal matrix on the first image. will be. Point X3 in the second image is a point projected vertically from point X1 in the first image and the former is represented by dx 'and dy'. The position mapping algorithm between the first image point in the first image and the image point in the second image, where the image point in the second image is the orthogonal projection point from the first image point to the correction plane, is equal to dx and dx '. It is obtained by determining the relationship and the relationship between dy and dy '. For example, the position mapping algorithm for X1 in the first image plane and X3 in the second image plane is a relationship to dx and dx 'in the x coordinate and dy and dy' in the y coordinate. The 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 perpendicular to the correction plane.

3, 4A, 4B and 5, the z scaling factor is determined by first determining the respective pixel coordinates (X1, X2) in the first and second images for features such as rectangle 10 on the correction reticle means. do. X3 is a point projected at right angles from the point X1 to the calibration plane using a position mapping algorithm. Since the z distance between X2 and X3 is known exactly, each z scaling factor 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 the corresponding distance on the second image is 25 pixels, the z scaling factor is 10 mm / 25 pixels = 0.4 mm / pixel.

After completing the calibration procedure, an x-y coordinate position mapping algorithm and a z scaling factor are obtained to determine the position of the contact elements with respect to the components 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 scaling factors. Since the position is determined accurately by the correction reticle means, the position of the contact elements can also be determined accurately in microns. The calibration procedure also allows inter-camera calibration to be performed to establish a relationship between the first camera 4 and the second camera 5. The relationship between the first camera and the third camera is also established in the manner described above.

Now that the measurement space has been corrected and the arrangement of the first and second cameras has been described, the measuring principle according to the invention is described with reference to FIG. The third camera 6 is arranged relative to the first camera 4 in a similar manner as the second camera. Assume that the electronic component enters the calibrated space and one of its contact elements is located at point P with respect to the calibration plane p. The first camera records the first image of the contact elements 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.

The second camera 5 records a second image of the contact element with the point P and the point P is identified as the second image point X2 in the second image. The point P is projected vertically on the correction plane p using a position mapping algorithm to provide a second point P '. In the second image, the third image point X3 is the image point at position P '. X3 has a contact element P disposed on the correction surface p. The position of the point X3 in the second image is determined by the position mapping algorithm. The displacement between X2 and X3 is due to the fact that the actual contact element is not located exactly on the correction plane but at the height difference Δz measured. According to the foregoing, the displacement Δz is determined by the product of the distance between X3 and X2 (ie Δz) and the z scaling factor in the z axis of the second image.

Since the present invention enables measurements of points in the calibrated space, it will be apparent to those skilled in the art to measure the distance between two points using the present invention as long as the two points are located in the calibrated space.

Thus, the practicality and usefulness of the system and method for measuring the distance between the contact elements of a part and the distance of the contact elements from the calibration plane in the calibration space, which may be the integrated circuit in which the contact elements are located, is apparent to those skilled in the art. Accordingly, the above description is exemplary and does not limit the invention itself claimed in the claims.

Claims (12)

In the method for measuring the position of each of the contact elements (2, 3) of the electronic component,
Positioning the contact elements 2, 3 in a calibrated space,
Illuminating said contact elements (2, 3),
Recording a first image of the contact element (2,3) with a first camera having a first image plane extending substantially parallel to a 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 of the contact elements 2, 3 on each of the contact elements 2, 3, wherein the first image point is the respective image; The first image processing step, which is a point located on the contact element (2, 3),
Processing said second image to identify a second image point for each said contact element on each said contact element (2,3), wherein said first for each said contact element (2,3) The second image processing step, wherein the first image point and the second image point correspond to the same point on each of the contact elements 2, 3;
Determining a third image point within the second image by a location mapping algorithm;
Determining a displacement between the second image point and the third image point in the second image,
The third image point is the first image point projected perpendicular to the correction plane.
Way.
The method of claim 1,
The displacement determining step is performed by multiplying a z-scaling factor with a coordinate difference between the second image point and the third image point.
Way.
The method of claim 1,
Deriving the position mapping algorithm for a particular relative position between the first camera and the second camera 5
Way.
The method of claim 1,
Deriving a z scaling factor for determining displacement of the second image point and the vertically projected image point
Way.
The method of claim 1,
Determining a displacement between any two points in the corrected space
Way.
Means for measuring the respective positions of the contact elements 2, 3 of the electronic component,
An illumination source 7, 8 for illuminating said contact elements 2, 3 pre-positioned in a calibrated space,
The first camera 4 and the second camera 5,
The first camera 4 and the second camera 5 provided for recording the first and second images of the contact elements 2, 3, respectively;
A processing unit,
The processing device is connected to the first camera 4 and the second camera 5, so that the first image point and the respective contact element in the first image for each contact element 2, 3 respectively. Retrieve a location of a second image point in the second image relative to (2,3), retrieve a third image point by a location mapping algorithm at the second image location, and the second image point and the third Determine the displacement between points,
The first image point and the second image point for each of the contact elements 2, 3 correspond to the same point on each of the contact elements 2, 3,
The third image point is a position projected vertically from the first image point
Means for measuring the position of each of the contact elements (2, 3) of the electronic component.
The method according to claim 6,
The processing device determines the displacement by multiplying a z-scaling factor with a coordinate difference between the second image point and the third image point.
Means for measuring the position of each of the contact elements (2, 3) of the electronic component.
The method according to claim 6,
Further comprising correction reticle means (9) for recording the images by said first and second cameras (4, 5),
The processing device derives the position mapping algorithm for a particular relative position between the first and second cameras 4, 5 from the image of the correction reticle means.
Means for measuring the position of each of the contact elements (2, 3) of the electronic component.
The method of claim 8,
The correction reticle means 9 comprises a base layer on which the features are arranged and a plurality of layers having the features thereon, the plurality of layers having a precisely known thickness and precisely positioning the features on the base layer. felled
Means for measuring the position of each of the contact elements (2, 3) of the electronic component.
The method of claim 8,
The processing device derives a z scaling factor that determines the displacement of the second image point and the third image point.
Means for measuring the position of each of the contact elements (2, 3) of the electronic component.
The method of claim 7, wherein
The processing device determines the displacement between any two points in the calibrated space.
Means for measuring the position of each of the contact elements (2, 3) of the electronic component.
The method according to claim 6,
A third camera 6 connected to said processing device for recording a third image of said contact element,
The third image has a fourth image point and a fifth image point,
The fifth image point is a point projected vertically from the first image point and is not recorded in the second image,
The processing device determines the displacement between the fourth image point and the fifth image point.
Means for measuring the position of each of the contact elements (2, 3) of the electronic component.

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