JP2001201317A - Height measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a number of ball heights on a BGA type IC from an image at high speed and with high accuracy. SOLUTION: This height measuring device has an illuminator for applying light from the vertical direction to the surface of a material to be measured, and the direction mirror-symmetrical with the vertical plane, an image pickup CCD camera and a mechanism for relatively moving a material to be measured and an optical system as main components.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for simultaneously measuring a large number of ball heights of a BGA type IC having a large number of solder balls on an IC package in a short time, and the like. And a device for measuring the height displacement of a large number of points in a short time, such as a device for measuring the height of an IC package pin or a surface measuring device. In the case of a BGA type IC, when the IC is mounted on a printed board, the ball must have the same height in order for the ball to be electrically connected to the printed board wiring. The apparatus can measure the relative height of these balls. 2. Description of the Related Art As a non-contact type measuring method, a laser beam is applied to a surface to be measured while scanning the image, the reflected light is imaged by a camera, and the height is sequentially geometrically calculated from the imaged position. There is a way. Alternatively, there is a method of sequentially measuring the height by tracing the surface of the object to be measured with a displacement sensor incorporating a laser light emitting element and a light receiving element. [0003] In the conventional method, when there are a large number of measurement points, there is a problem that the measurement time is required and that if the measurement time is shortened, the measurement accuracy is deteriorated. SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of measuring the heights of a large number of measurement points with high measurement accuracy and in a short time. In order to achieve the above object, the height measuring apparatus of the present invention captures a large number of measuring points at two positions with a CCD camera and obtains high measuring accuracy in a short time. Provide a way. Hereinafter, the ball height measuring device of the BGA type IC will be mainly described. [0005] There is a linear moving mechanism using a motor and a ball screw or the like, which has a base on which a BGA type IC to be measured is mounted. With this mechanism, the imaging optical system described below and the BGA-type IC relatively linearly move. A CCD camera that continuously captures images in synchronization with a rectilinear movement is a linear CCD camera in which pixels are arranged in a direction perpendicular to the direction of the rectilinear movement, and is common to the two linear CCD camera positions described below. The first imaging position of the linear CCD camera is B
The direction perpendicular to the ball surface of the GA type IC is the optical axis, and the illumination direction is parallel to this optical axis. The focus position and illumination position of the camera are at the apex of the ball. The imaging position of the second linear CCD camera is such that a parallel light source and a linear CCD camera are arranged in two oblique directions symmetrical with respect to the optical axis direction. Parallel. The focus position and illumination position of the camera are at the top of the ball. Since the apex of the ball is locally parallel to the plane of the BGA type IC, the light emitted from the direction perpendicular to this plane is imaged at the first linear CCD camera position. Since the reflection angle of the light projected on the plane is equal to the incident angle, the second parallel illumination and the linear CCD camera symmetrical with respect to the plane vertical axis can image the same ball vertex. Since one ball vertex is imaged at two linear CCD camera positions, the ball position can be calculated by geometric calculation from the relative positions of these cameras and the amount of linear movement. The top of the first ball on the BGA type IC is
It is assumed that the image is taken at the center of the image of the linear CCD camera at the first position, and the same ball vertex is located at the linear CC at the second position.
It is assumed that the image is also captured at the center of the image by the D camera. When the optical system and the BGA type IC are relatively moved by the linear movement mechanism,
If the vertex of the second ball is detected at the center of the image by the first linear CCD camera and is detected at the x-movement position at the center of the image of the second linear CCD camera, the vertex of the second ball relative to the vertex of the first ball The height difference is expressed by the following equation. Here BG
The direction in which the A-type IC is close to the second linear CCD camera is defined as x + direction. X = tanA A is the angle formed by the optical axis of the second linear CCD camera with respect to the plane of the BGA type IC. In the above description, the case where the ball vertex is imaged at the center of the image taken by the two linear CCD cameras has been described. Since the timing is synchronized, the screen position can be converted into the amount of linear movement, and the calculation can be performed in the same manner. Further, the calculation can be easily performed for a ball that is perpendicular to the direction of the straight movement. BGA type IC
You can measure the relative heights of all the vertices of the ball above. In the above, the first linear CCD camera and the second linear CCD camera have been described in the case where the first ball vertex is imaged at the same position of the rectilinear moving mechanism at the center of the image. If there is a distance of x1, it can be calculated by replacing x with x-x1 in the following equation. [0013] Similar to the light reflected from the top surface of the ball, the light is also reflected from the flat base surface of the BGA type IC.
An image is formed on the camera, but since it is known that the vertex position of the ball exists in a predetermined range in advance, the image other than the ball vertex image can be removed by image processing. FIG. 1 shows an example of measuring the relative height of a ball of a BGA type IC as an object to be measured. Reference numeral 20 denotes a BGA type IC, and reference numerals 17, 18, and 19 denote balls on the IC. The BGA type IC is horizontally fixed on a slider 21 of a linear guide 22 which can be moved by a motor. The moving direction of the slider is indicated by an arrow 24. The CCD camera 1 is installed parallel to the surface vertical line of the BGA type IC.
Reference numeral 2 denotes a CCD element inside the camera. The pixels 2 are arranged in the CCD element in a direction perpendicular to the moving direction 24. The light source 5 irradiates a parallel light beam by a condensing mirror, and irradiates a BGA type IC with light through a blue filter 6 in parallel with the optical axis of the CCD camera 1 by a half mirror. The camera 1 is also provided with a color filter 4 so that only blue light enters the CCD element. An imaging lens 3 is attached to the CCD camera 1. The light source 16 irradiates the BGA type IC surface at an angle A with the optical axis 8 of the CCD camera 1. This light source is also provided with a condenser mirror, and can irradiate a parallel light beam. A red filter 15 is attached. A CCD camera 9 and a lens 11 are attached to the optical axis of the CCD camera 1 as targets. The red filter 2 is provided on the lens 11 of the CCD camera 9.
5 is attached. While moving the BGA type IC by the motor 23, the CCD camera 1 and the CC
An image is taken by the D camera 9. The position of an image captured at a certain moving position is clear. Light is reflected on the surface of the object to be measured, and the reflected light forms an image on the CCD camera 1 through the lens 3 of the CCD camera 1. Since this image is reflected from a plane perpendicular to the light, it is reflected at the base of the measured object and the apex of the ball. It is assumed that the top of the first ball 17 is formed on the CCD camera 1 at the center of the image at the position shown in the figure, and the image of the same ball is formed on the center of the image of the CCD camera 9 by the light of the light source 16. And The second ball 18 forms an image at the center of the image at the position of the CCD camera 1 with the first light source 5 and then moves with the second light source 16 at the position moved in the direction of the second CCD camera by the distance x. If the image is formed, the height of the second ball is larger than the height of the first ball by a dimension represented by the following expression. By the above method, the relative height of each ball can be measured. In the above embodiment, red and blue optical filters are used to avoid light interference between the two sets of light sources and the CCD camera. By shifting the imaging positions of the two sets of light sources and lenses, interference of light can be avoided and the present invention can be implemented without using a color filter. In the embodiment of FIG. 1, two sets of light sources, a CCD camera and a lens are used, but if a mechanism for moving from the position of the first optical system to the position of the second optical system is used, one set of optical systems is used. The present invention can be practiced in a system. Since the general arrangement of the balls of the BGA type IC is known in advance, the speed of the moving mechanism can be increased and the measurement time can be shortened in a portion other than the position where the apex can be imaged. In the description so far, the optical system such as the first CCD camera is disposed perpendicular to the surface of the BGA type IC. However, the optical system such as the first CCD camera is also symmetrical with the vertical line of the BGA type IC surface. It is clear that similar results can be obtained by arranging the optical system such as a two CCD camera at an angle different from that of the optical system. In the above description, the measurement is performed based on the direction perpendicular to the BGA type IC. However, the vertical line of the BGA type IC has a certain angle, and the first optical system such as a CCD camera and the second It is clear that if an optical system such as a CCD camera is arranged, it is possible to measure a certain part at a certain angle with the BGA type IC surface. In the description so far, a linear CCD camera is used as an imaging camera, and a mechanism for relatively moving the BGA type IC and the optical system is used. The same measurement can be performed with a structure without a moving mechanism. In this embodiment, the measurement of the ball height of a BGA type IC has been described. However, the measurement of the height of the lead portion of an IC package other than the BGA can be easily measured. Similarly, the height of the lead of the surface mount component mounted on the printed circuit board can be measured. When operating at 5120 pixels and 40 MHz as a CCD element used in a linear CCD camera, 1
The line scanning time is about 130 microseconds,
Scanning 35 mm at a pitch of 2 microns can take an image in about 1.2 seconds, and this speed is very fast in practical use. However, the imaging range is set to half of 35 mm, and the moving time is ignored in the range where no imaging is performed. The measurement accuracy at this time is 2 microns or more, and a large practical effect is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view of a ball height measuring device of a BGA type IC. [Description of Signs] 1 First-position linear CCD camera 2 First-position linear CCD camera pixel 3 First-position linear CCD camera lens 4 First-position linear CCD camera color filter 5 First-position light source 6 First-position light source Color filter 7 first position parallel light irradiator 8 first position optical system optical axis 9 second position linear CCD camera 10 second position linear CCD camera pixel 11 second position linear CCD camera lens 12 second position linear CCD Camera optical axis 13 Second position light source optical axis 14 Second position parallel light irradiator 15 Second position parallel light irradiator color filter 16 Second position light source 17 BGA type IC ball 1 18 BGA type IC ball 2 19 BGA type IC ball 3 20 BGA type IC 21 BGA type IC fixing slider 22 BGA type IC moving linear guide 23 linear guide Motor 24 BGA type IC moving direction 25 second position light source color filter 26 first position optical system support 27 second position light source support 28 second position CCD camera support 29 base

Claims (1)

Claims: 1. A linear CCD camera in which pixels are arranged in a direction perpendicular to the moving direction with parallel illumination from a direction perpendicular to the surface of the object while relatively moving the object to be measured. The surface of the object measured and imaged by a linear CCD camera in which the vertex position in the surface of the object to be measured and the vertical axis of the object to be measured and the mirror target angle each have an optical axis and pixels are arranged at right angles to the moving direction. A device that geometrically calculates and measures the height of the vertex in the plane of the object to be measured from the same vertex position in the inside. 2. The apparatus according to claim 1, wherein the light is irradiated and imaged from a direction perpendicular to the surface of the object to be measured, and the light is irradiated and imaged from a direction having an optical axis at an angle perpendicular to the surface of the object to be measured and a mirror target angle. A device with a structure in which the same wavelength can be simultaneously imaged by linear CCD cameras having different light wavelengths and color filters corresponding to the respective light sources. 3. The apparatus according to claim 1, wherein the irradiation / irradiation is performed from a direction perpendicular to the surface of the object to be measured.
An apparatus having a structure for moving a light source / CCD camera for imaging from a direction having an optical axis to an object surface and a mirror target angle from a direction having an optical axis to a position for irradiation / imaging. 4. A mechanism for moving a linear CCD camera and a light source relative to an object to be measured by the apparatus according to the above-mentioned [1], [2] and [3]. A device with a structure that moves selectively and finely only in parts and moves at high speed in other parts. 5. The apparatus according to claim 1, 2 or 3, wherein there is no mechanism for relatively moving the object to be measured, the light source, and the CCD camera. A device using an area CCD camera.