JP3045151B2 - Ball thickness measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a ball thickness measuring device for measuring the thickness of a ball formed at an end of a wire bonded to an IC chip or the like.

[0002]

2. Description of the Related Art Conventionally, an operator uses a measuring microscope to measure the thickness of a ball formed at an end of a wire bonded to an IC chip or the like. The measuring method is performed according to the following procedure (Japanese Unexamined Patent Publication No.
224267). Attach a high-magnification lens to the microscope and first focus on the surface of the IC chip. The lens height at that time is measured and set as a reference point (zero point). Next, the lens is moved in the Z direction to focus on a plane portion on the ball formed at the time of pressing, and the lens height at that time is measured. The difference between the height of the upper surface of the ball and the height of the chip surface measured earlier is defined as the ball thickness.

[0003]

In recent bonding, the ball diameter tends to be small (around 60 μm), and the flat portion due to the pressing has become small, and some of them are not present. For this reason, there is a problem that it is difficult to focus on a plane portion, it takes a long time for the measurement, and the measured value varies from person to person.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a method for accurately measuring the thickness of a ball in a short time by performing stereo photography using two sets of a CCD camera and coaxial illumination. It is an object of the present invention to provide a ball thickness measuring device which enables the above.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, two sets of a CCD camera and a coaxial illumination are arranged at a horizontal angle of 90 degrees on a normal line of a tapered portion formed on each ball. And the respective coaxial illuminations are turned on to capture images into the respective CCD cameras. The positions in these images, the height of the CCD cameras, the horizontal distance from the intersection of the optical axes of the CCD cameras to the center. The ball thickness is calculated from the height of the tapered portion of the ball and the radius of the wire.

According to a second aspect of the present invention, the position coordinates in the image are X1, Y1, X2, Y2, the height of the CCD camera is Hc, and the horizontal position from the intersection of the optical axis of the CCD camera to the center. If the distance is Dc, the height of the tapered portion of the ball is Ht, and the radius of the wire is Rw, the ball thickness Hb is Hb = Hc−Ht− (Dc−Rw−X1) ta
nA + {Y2 · (Dc−Rw−X1)} / (Dc · co
sA｝ is calculated. Each CC
The position coordinates of the tapered portion of the ball portion are detected from the image captured by the D camera, and the ball thickness can be calculated by substituting these position coordinates into a mathematical expression.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the ball thickness measuring apparatus according to the present invention will be described below with reference to the drawings. 1 to 3, the ball thickness measuring apparatus includes two CCD cameras 1a and 1b for receiving light reflected from a tapered portion 12 of a ball 10 formed on a chip 13. Each of the CCD cameras 1a and 1b is disposed at the same height, and each of the CCD cameras 1a and 1b faces obliquely downward at an angle A with respect to a horizontal plane and has a horizontal angle of 9 with each other.
They are arranged so that the focal points are matched at 0 degrees.

[0008] The coaxial lights 2a and 2b
A parallel light is emitted coaxially with the optical axes of the CD cameras 1a and 1b. The angle A is an angle formed by a normal to the tapered portion 12 and a horizontal plane. As shown in FIG. 3, the angle C formed by the opposing tapered portions 12 is the same as the taper of the tip hole of the pressing jig to be bonded.
Its value is known.

In FIG. 2, the horizontal angles B of the optical axes of the CCD cameras 1a and 1b are equal to the direction of the wire 11 from the side opposite to the direction of the wire 11 protruding from the ball 10 to be measured. The CCD cameras 1a and 1b are installed in the camera. In this state, the coaxial lights 2a and 2b are turned on as shown in FIG. 1, and the images of the ball 10 are captured by the CCD cameras 1a and 1b.

FIG. 4 shows a captured image. FIG. 4A shows an image captured by the CCD camera 1a, and FIG.
(B) is an image captured by the CCD camera 1b. In both images, a part of the slope of the tapered portion 12 is bright and the others are dark. 4A, the position coordinates X1, Y1 of the position P1 of the upper end of the tapered portion 12 from the center of the CCD camera 1a are detected. 4B, the position coordinates X2 and Y2 of the position P2 of the upper end of the tapered portion 12 from the center of the CCD camera 1b can be detected.

These position coordinates X1, Y1, X2, Y2
By substituting the coordinates into the following equation, the ball thickness Hb can be calculated. Hb = Hc-Ht- (Dc-Rw-X1) tanA +
{Y2 · (Dc−Rw−X1)} / (Dc · cosA) where, Hc: height of CCD cameras 1a, 1b Dc: horizontal distance from the intersection of the optical axes of CCD cameras 1a, 1b to the center Ht: Height of tapered portion 12 (determined by pressing jig) Rw: radius of wire 11

[0012]

As described above in detail, while the conventional focus is measured twice by adjusting the focus to the surface of the IC chip and the flat portion on the ball, in the present invention, the taper portion always formed on the ball is used. The measurement can be performed in a short period of time by using the camera and the illumination to perform the measurement, and there is an effect that there is no variation between persons.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of a ball thickness measuring device according to the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is an enlarged view of a ball portion.

FIGS. 4A and 4B are images captured by each CCD camera.

[Explanation of symbols]

 1a, 1b CCD camera 2a, 2b Coaxial illumination 10 Ball section 11 Wire 12 Tapered section

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G06T 1/00 H01L 21/60 321 H01L 21/66

Claims (2)

(57) [Claims] 1. Two sets of a CCD camera and a coaxial illumination are arranged at a horizontal angle of 90 degrees on a normal line of a tapered portion formed on a ball. Capture, location in these images, the CC
Measuring the ball thickness from the height of the D camera, the horizontal distance from the intersection of the optical axis of the CCD camera to the center, the height of the tapered portion of the ball, and the radius of the wire; apparatus. 2. Position coordinates in the image are X1, Y1, X
2, Y2, the height of the CCD camera is Hc, the horizontal distance from the intersection of the optical axis of the CCD camera to the center is Dc, the height of the tapered portion of the ball is Ht, and the radius of the wire is R.
Assuming w, the ball thickness Hb is Hb = Hc−Ht−
(Dc-Rw-X1) tanA + ΔY2 · (Dc-Rw
2. The ball thickness measuring device according to claim 1, wherein the ball thickness is calculated by an equation of -X1) {/ (Dc.cosA)}.