JPH0968405A - Bonding wire connection state inspecting instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable measurement and judgment three-dimensionally on whether the height of an IC chip and a bonding wire and a distance therebetween are within a prescribed value. SOLUTION: In structure, a bonding wire 28 welded on the top surface of an IC chip 26 extends upward and is curved gently down to the surface of a lead frame 27. A mirror 24 which projects the bonding wire 28 and the IC chip 26 onto the surface of a mirror 24 is arranged on the side of the bonding wire 28 to tell how the bonding wire 28 is curved and integrated with a camera 22 above the bonding wire 28 to take in an image thereof. Moreover, a measurement is made possible along the shape of the bonding wire 28 projected on the mirror 24 and an arithmetic means is provided to calculate a distance between the IC chip 26 and the bonding wire 28 from a measured value obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for inspecting a connection state between an IC chip and a bonding wire for guaranteeing the quality of an IC.

[0002]

2. Description of the Related Art Conventionally, for example, as shown in FIG.
The lead frame 7 connecting the IC chip 6 adhered onto the lead frame 7 with the adhesive 9 and the outside of the electrode as shown in FIG.
There is so-called wire bonding, which connects to and. This is because at the time of trial production before starting production, the wire bonding device (not shown) for production is used to actually connect the bonding wires 8 many times, and the bonding state is changed by using a magnifying glass or a microscope. It is a visual inspection.

The size of the ball 8a, which is the fusion-bonded portion of the bonding wire 8 thus manufactured, and the crescent 8
In addition to confirming the appropriateness of the shape of b, the presence / absence of defects such as height and deformation of the bonding wire 8 is visually judged, and when it is in a state where the bonding wire 8 can be properly manufactured, it is common to start production. There is.

[0004]

However, the method of visually inspecting the bonding state after connecting the bonding wire 8 is mainly to see it in a flat plane, and the bonding wire 8 is checked in three dimensions to determine whether the bonding wire 8 is excessively high or low. It is difficult to perform visual inspection in units of 10 μm. The main cause of the defect is that the bonded bonding wire 8 jumps out of the resin encapsulation portion or is deformed and entangled to cause a short circuit or contact with the IC chip 6 during resin encapsulation.

When a defect is found in the operation test of the final process, it is often necessary to re-inspect the process corresponding to the defect and pursue the cause.

Therefore, an object of the present invention is to provide a bonding wire connection state inspection device capable of three-dimensionally measuring and determining whether or not the height or distance of the bonding wire from the IC chip is within a standard value. I have to.

[0007]

In order to achieve this object, the invention as set forth in claim 1 is such that the bonding wire welded to the upper surface of the IC chip extends upward and curves to form a ridged lead frame surface. A bonding wire connection state inspection device for measuring a distance from a calculated virtual plane of the IC chip to the bonding wire in a structure descending to a bonding surface on a mirror surface so that a bending state of the bonding wire can be known. And a mirror for projecting the IC chip is arranged on the side of the bonding wire, provided integrally with a camera for capturing an image above the bonding wire, and the measurement can be performed along the shape of the bonding wire projected on the mirror. From the virtual plane to the bonding wire It is characterized in that digit.

According to the first aspect of the present invention, the virtual plane of the IC chip and the three-dimensional shape of the bonding wire can be taken from the camera along the shape of the bonding wire as they are, and the virtual processing is carried out. The height and distance of the bonding wire from the plane can be calculated.

In the bonding wire connection state inspection device according to a second aspect of the present invention, the arithmetic means projects the upper corner line of one end face of the IC chip on a mirror, and the measurement points (a and b) at both ends of the corner line. Based on the measured values between these three points (a, b, c) from the coordinate position between the upper corner line of the opposite end face and the substantially central measurement point (c) of the corner line reflected on the mirror. The virtual plane of the IC chip is calculated, and the height of the measurement point that moves along the shape of the bonding wire projected on the mirror and the distance from the angle line of the virtual plane of the IC chip are measured to bond with the virtual plane of the IC chip. The feature is that the shortest distance to the wire is calculated.

According to the second aspect of the present invention, the measurement reference plane can be accurately determined by calculating the virtual plane of each IC chip. If the distance (L) at which the bonding wire is closest to the IC chip can be found based on this reference surface, and this calculated value does not satisfy the standard value,
It can be sorted and deleted as defective products.

According to a third aspect of the present invention, there is provided a bonding wire connection state inspection device characterized in that the mirrors of the mirror unit are provided in right and left pairs so as to be rotatable.

According to the third aspect of the invention, since the shape of the bonding wire projected on the mirror is projected on the left and right sides, it is easy to find a deviation of the set position of the mirror from the deviation of the left and right images.

[0013]

1 to 3 show an apparatus and method for inspecting a connection state between an IC chip and a bonding wire according to an embodiment of the present invention.

First, the structure will be described. Reference numeral 21 in FIG. 1A is a bonding wire connection state inspection device,
Reference numeral 22 is a CCD camera, 22a is a close-up lens, 22b is a half mirror, 23 is an epi-illumination device, 24 is a mirror, and 25 is a computing device. An IC chip 26 is installed below the mirror 24 on a carrying jig (not shown). , 27 is a lead frame, and the connection between these two is the bonding wire 2.
8 The welded portion of the bonding wire 28 and the IC chip 26 is called a ball 28a, and the welded portion of the lead frame 27 is called a crescent 28b.

FIG. 1 is an enlarged view of this bonding state A portion.
This is shown in FIG.

The CCD camera 22 and the mirror 24 are also provided.
Is integrally mounted on an X, Y stage (not shown), and the mirror 24 is rotatably provided.

Then, the image projected on the mirror 24 of the bonding wire 28 irradiated by the epi-illumination device 23 through the half mirror 22b is taken in from the CCD camera 22 through the close-up lens 22a and transferred to the arithmetic unit 25, It has a function of calculating the distance between the IC chip 26 and the bonding wire 28.

The mirror 24 may have a pair of left and right structures (shown by broken lines in the figure). Mirror 24
The function is exactly the same as the case of one sheet.

When the IC chip 26 and the lead frame 27 are connected by the bonding wire 28, the IC chip 26 and the lead frame 27 are sequentially moved by the carrying jig below the mirror unit 24 so that the bonding wire inspection can be continuously performed.

2A and 2B show a method of measuring and calculating a virtual plane.

First, as shown in FIG. 2A, the IC chip 26 adhered to the lead frame 27 is projected on the mirror 24. The front view of this figure shows a state in which the upper left corner line 26b is reflected on the mirror 24 toward the drawing, and in the same plan view, points a and b near the terminal of the same upper corner line 26b are a'on the mirror 24. , B'point.

That is, the upper corner line 26b of the IC chip 26
The points a'and b'of the mirror 24 show that the height rises from point b to point a and the heights are different. Then, from the image shown in this plan view, the height dimensions A / 2 and B
We get / 2.

Next, in FIG. 2B, the lead frame 27
It shows a state in which the IC chip 26 adhered to is transferred by the width of the IC chip 26 by a carrying jig.

The front view shows a state in which the upper corner line 26c of the other end of the IC chip 26 is projected on the mirror 24. From the image of the plan view of the same figure, the dimension C / 2 of the point c provided at the substantially center of the right-angled line 26c at the other end and the point c'projected on the mirror 24 can be obtained.

The image in which these three points a, b, and c are projected on the mirror 24 as points a ', b', and c'is taken into the CCD camera 22 and the IC chip is calculated by the arithmetic unit 25. 26 the virtual plane of the upper surface is calculated,
The distance to each bonding wire 28 is measured and calculated based on this virtual plane.

FIG. 3 shows a state in which the height, which is an element of measurement, is constantly measured in the measurement of the distance from the upper surface of the IC chip 26 to the bonding wire 28, using one bonding wire 28 as a target example. There is.

That is, in the front view of FIG.
6. An image line is connected to the center of one bottom surface of the ball 28a, which is a fusion portion of the bonding wire 28 and the top surface of the bonding wire 28, to form an intersection point, and the intersection point and the intersection point at the position of the radius (J) of the bonding wire 28 Measure the difference.

Further, in the plan view of the figure, the side surface of the bonding wire 28 is projected on the mirror 24, and the projection line is three-dimensionally moved from the upper surface of the IC chip 26 to the highest position of the bonding wire 28. It is projected.

This image is taken in from the CCD camera 22 and the height of the bonding wire 28 is calculated by the arithmetic unit 25 (see calculation formula (1)).

Further, the distance (L) between the IC chip 26 and the bonding wire 28 is measured by the above-mentioned height (I),
The distance (S) from the IC chip 26 can be measured and calculated from the side image projected on the mirror 24 (see the calculation formula (2)).

[0031]

[Embodiment] Further, by adopting the following inspection method, the defect rate can be greatly reduced.

That is, when an image is captured on the mirror with the bonding wire at an incident angle of 45 °, the upper angle of the mirror is 2
If the angle is 2.5 °, video analysis can be performed as parallel line input, and the wire height (I) is

[0033]

[Formula 1] Can be calculated as

By calculating the height by the formula and simultaneously measuring the horizontal distance (S) from the IC chip,

[0035]

[Formula 2] The shortest distance (L) from the IC chip can be calculated by the following two equations.

As a standard value, L ≦ bonding wire diameter (2J) × 2 I ≦ 500 μm. If this standard value is interrupted, NG is judged and "removal" operation can be performed as a defective product. It became so.

[0037]

According to the bonding wire connection state inspection device of the first aspect of the present invention, since it is possible to measure along the shape of the bonding wire reflected on the mirror, it is possible to grasp the distance three-dimensionally. Since the defective product can be removed immediately after wire bonding, sealing work is not required. Therefore, the sealing material can be saved, and the number of work steps and inspection steps can be reduced.

According to the bonding wire connection state inspection device of the second aspect of the present invention, the shortest distance between the virtual plane of the IC chip and the bonding wire is three-dimensionally projected for the first time by using the mirror. , The image can be captured and calculated by the CCD camera, the short-circuit defect with the IC chip can be reduced, and the process can be improved. According to the bonding wire connection state inspection device of the third aspect of the present invention, since the images are simultaneously captured from the left and right, it is easy to follow the image shape. Therefore, it is accurate. In addition, by placing the left and right images at the target positions when assembling the mirror, the mirror angle and the center can be easily set, and the assembly and the adjustment can be easily performed.

[Brief description of drawings]

FIG. 1 (a) is a schematic view of a bonding wire connection state inspection device according to an embodiment of the present invention, and FIG. 1 (b) is (a).
It is an A section enlarged view of a figure.

2A and 2B are explanatory views showing a measurement state of a virtual plane of an IC chip showing the same embodiment.

FIG. 3 is an explanatory diagram showing a state of measuring the height of the bonding wire according to the embodiment.

FIG. 4 is a plan view showing a connection state example of an IC chip and a bonding wire of a conventional technique.

[Explanation of symbols]

21 ... Bonding wire connection state inspection device 22 ... CCD camera 24 ... Mirror 25 ... Arithmetic device 26 ... IC chip 26a ... Virtual plane, 26b ... Upper corner line, 26c ... Other end upper corner line 27 ... Lead frame 28 ... Bonding wire

Claims (3)

[Claims] 1. In a structure in which a bonding wire welded to the upper surface of an IC chip extends upward and curves to form a ridge down to the lead frame surface, from a calculated virtual plane of the IC chip to the bonding wire. A bonding wire connection state inspecting apparatus for measuring a distance between the bonding wire and a mirror for projecting an IC chip on a mirror surface so that the bending state of the bonding wire can be seen, and the bonding wire is placed above the bonding wire. It is provided integrally with a camera for capturing an image, enables measurement along the shape of the bonding wire reflected on the mirror, and is provided with an arithmetic means for calculating the distance between the virtual plane and the bonding wire from the measured value. Bonding wire connection state inspection device. 2. The calculation means projects an upper corner line of one end surface of the IC chip on a mirror, and displays measurement points (a and b) at both ends of the corner line and an upper corner line of the other end surface. The virtual plane of the IC chip is calculated based on the measured values between the three points (a, b, c) from the coordinate position of the angle line projected on the mirror and the substantially central measurement point (c), and the mirror The shortest distance between the virtual plane of the IC chip and the bonding wire is calculated by measuring the height of the measurement point that moves along the shape of the bonding wire projected on the screen and the distance from the angle line of the virtual plane of the IC chip. The bonding wire connection state inspection device according to claim 1. 3. The mirror of the mirror unit is provided in a pair of left and right to be rotatable.
Or the bonding wire connection state inspection device according to item 2.