JPS623578B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to automation of position measurement of wire bonding in the assembly process of semiconductor integrated circuits such as ICs and LSIs.

Conventionally, in the pellet die bonding process in the assembly process of semiconductor products such as ICs and LSIs, the pellets are quite large in size.
When thermocompression bonding pellets onto a jig called a lead frame, the positioning accuracy is ±100μ or more, so the amount of positional deviation is measured visually by the operator, but this visual inspection process requires that the patterns are extremely concentrated. This caused mental pain to the workers. In addition, in such precision work, a small measurement error can lead to a decrease in product yield, so a highly reliable automatic position measuring device has been required.

For such automatic position detection, Japanese Patent Application Laid-open No. 49-
There was a method as shown in Publication No. 11165. This method takes into account that patterns in parts other than the original pattern to be detected may match the standard pattern due to dirt, chips, etc. Standard patterns are also set, the positions of each standard pattern are determined, and it is determined whether the pattern to be detected has been detected based on whether the distance and direction between the determined positions are predetermined. This allows position detection to be performed with high accuracy without detecting erroneous patterns.

However, in such a method, after detecting the positions of the pattern, processing such as determining the distance between these positions is required, making it impossible to speed up the processing.

An object of the present invention is to provide a position detection device that accurately detects the position of an object using a plurality of standard patterns and performs position detection processing at high speed.

In order to achieve such objectives, the present invention has the following features:
To cut out a plurality of partial patterns while shifting their positions from an object while keeping the distance and direction between them constant. By comparing a plurality of partial patterns obtained in this way with a standard pattern, the detection of a match between the standard patterns and the determination of the distance and direction between the patterns in which a match has been detected are performed substantially simultaneously.

That is, a converting means for converting an image of an object whose position is to be detected into a two-dimensional pattern signal, and a converting means for converting an image of an object whose position is to be detected into a two-dimensional pattern signal, each of which corresponds to a pattern of a plurality of regions at predetermined positions on the object having a positional relationship of a predetermined distance and direction from each other. means for storing a plurality of standard patterns; and means for sequentially cutting out a plurality of partial patterns having a positional relationship in the predetermined distance and direction from the two-dimensional pattern signal obtained by the converting means while shifting their positions; a comparing means for sequentially comparing a plurality of partial patterns sequentially cut out by the cutting means from a plurality of standard patterns stored in the storage means, corresponding patterns; and a cutting means when the comparing means detects a match. and detecting means for detecting the position of the object based on the position of the cut out partial pattern.

FIG. 1 shows a semiconductor component, such as an LSI pellet, before wire bonding. In the figure, 1 is an LSI pellet (hereinafter abbreviated as pellet), 2 is a pedestal part of the pellet called a tab, 3-0, 3-1,... (some parts are not shown)
4-0, 4-1, etc. are external electrodes that are part of the lead frame.
0, 3-1 is shown in the figure as 3-0, 3-1 for simplicity.
Although only two are described, external electrodes 4-0, 4
-1, in fact, about 20 to 40 pads are provided, and the corresponding pads and external electrodes are connected to each other by wire bonding with gold wires or aluminum wires.

The problem here is the variation in the pellet position, ie, the coordinates (X, Y) expressed in rectangular coordinates, and the pellet direction, ie, the angle (θ). In this case, the magnitude of the dispersion, that is, ΔX
and ΔY is ±100 to 150μ, Δθ is about 30′, and in order to perform wire bonding automatically,
It is necessary to detect the position of each pad within ±10μ.

In the present invention, for example, as shown in FIG. is a “specific pattern recognition method” that has already been filed by the same applicant as the present invention.
(Patent Application No. 51-14031). Although a plurality of visual field images are required in order to detect the rotational deviation Δθ of the pellet, in order to simplify the explanation, the number of visual field images is set to two for convenience. The size of the visual field image is approximately 600 μ so as to cover the pellet positional deviations ΔX, ΔY, rotational deviation Δθ, etc. In addition, the position of the visual field image is variable,
In order to perform pad detection on pellets of various sizes, the apparatus of the present invention allows the position of each visual field image to be specified arbitrarily.

FIG. 3 shows the basic configuration of a position detection device according to the present invention. In the figure, reference numeral 6 denotes a metal plate called a lead frame, and as shown in FIG. 1, the pellets 1 are crimped onto the tabs 2 at a constant pitch. Reference numeral 7 denotes a frame feeding mechanism that intermittently feeds the lead frame 6 in the direction of the dashed arrow shown in the figure, and feeds the pellets 1 one by one directly below the optical system. Further, 8 is a light source for illuminating the pellet, 9 is a semitransparent mirror, 10 is an objective lens for obtaining an enlarged image of the pellet 1, and 1
Reference numeral 1 denotes a reflecting mirror for image division, which divides the enlarged image from the pellet 1 into at least two partial images. The figure shows the case of dividing into two partial images, whereby an enlarged real image of a part of the pellet 1 is obtained at the positions 12-0 and 12-1 shown in the figure.

13-0, 13-1 are relay lenses, 14-
0, 14-1 is a photoelectric conversion device for scanning an optical image and converting it into a temporal analog video signal, and for example, a TV camera such as a vidicon is used.
Reference numerals 15-0 and 15-1 are mounting stands for moving the TV camera, and pellets 1 are moved by moving the photoelectric conversion devices within a plane parallel to the light receiving surfaces of the photoelectric conversion devices 14-0 and 14-1. This is to adjust the position of the field of view depending on the pellet when changing the type of pellet.

16-0, 16-1 are photoelectric conversion devices 15-0,
15-1 is an analog video signal, 17 is a video processing device, analog video signals 16-0, 16-1
Performs binarization, pad detection processing, etc. Reference numeral 21 denotes a control device such as a computer, which controls the data processing and video processing circuit necessary for pad detection processing by sending signals 18,
20 and interface 19. 22 is a frame feeding mechanism 7 and a stage 15-
Drive circuits 0 and 15-1, 23 are circuits for controlling the drive circuit 22, and are connected to the computer via a signal 24, an interface 19, and a signal 20.

25 is an automatic wire bonder, and an image processing device 17
Based on the positions of the pads determined in step 1, a computer 21 determines the positions of all pads, and an automatic wire bonder 25 automatically connects each pad to an external electrode using a metal wire. In this case, if the speed at which the pad position is detected and the speed at which automatic wire bonding is performed do not match, a buffer such as a cassette tape is added to the automatic wire bonder 25 to temporarily store the input signal, and the detection station 26 and the automatic wire bonder 25 A system that combines these offline is also conceivable.

Also, if the pad position detection speed is sufficiently faster than the frame feed speed, as shown in Figure 4,
A plurality of detection stations 26 can be controlled with one video processing device and computer. The present invention provides a system in which one video processing device and computer can serve at least four detection stations.

Next, an overview of video processing according to the present invention will be described. In FIG. 5, 30 is in the optical system of the present invention.
An analog video of a partially enlarged pellet image obtained from a photoelectric converter such as a TV camera is shown. In the figure, a square portion 31 is an aluminum pad, 32 is an extension of the above-mentioned 31 and is a lead-out portion to the internal wiring, and 33 is a scar from an inspection blower in the previous process.

There are pellets of various sizes depending on the variety, but the size of the square portion 31 of the pad is common to all pellets, and is approximately 120 μ□. in this case,
Depending on the type of LSI and the position of the field of view within the pellet, the pull-out portion 32 may extend to either the top, bottom, left or right. Further, although the size of the blower scar 33 is approximately constant, the position within the pad is indeterminate. The peripheral part 34 of the pad 31 is a silicon oxide coating part, 35 is a silicon part at the edge of the pellet, and 36 is a gold-silicon eutectic part outside the pellet.

In the case of epi-illumination as shown in FIG. 3, the aluminum part like the pad is the brightest, followed by the silicon part 35 and the silicon oxide part 34 which become darker in that order. Since the gold-silicon eutectic region 36 is inclined in the optical axis direction of the optical system, it is darkest near the pellet as shown in the figure and gradually becomes brighter as it moves away from the pellet. Further, the prober scar 33 is dark because it is depressed.

FIG. 6 is a binarized image obtained by converting the analog image 30 of FIG. 5 into a binarized image using the intermediate brightness between the brightness of the aluminum part and the brightness of the silicon oxide part as a threshold value. As shown, the pad 41, the pull-out portion 42, the silicon portion 45, and the portions 46-1 of the gold-silicon eutectic portion 46 that are far from the pellet are white, and the prober scar 43, the silicon oxide portion 44, and the gold-eutectic portion 46 are white. Portion 46 of portion 46 near the pellet 46-
0 is black (hatched part). in this way,
If an analog video signal can be binarized, a relatively simple video processing device can be realized, so in the present invention, the processing target is a binarized video.

Further, in the present invention, in order to further facilitate the electrical processing of the image, the binarized image is sampled into 320 pixels in the X direction and 240 pixels in the Y direction, for example, as shown in FIG. In the same figure, there are 64 pixels in the X direction and 20 pixels in the Y direction.
The picture element part is the return line section, and the X direction 32 in it
The picture element, a band-shaped part of 12 picture elements in the Y direction, is the part where the pulse of the external synchronization signal of the TV camera is output. In addition,
Hereinafter, the video will be sampled every 1 pixel, every 2 pixel, etc. in both the X and Y directions of each divided grid point shown in the figure, and will be referred to as "mode 1", "mode 2", etc. I'll call you. In Figure 7,
The mark is mode 1 sampling, ○†g

Claims (1)

[Claims] 1. Conversion means for converting an image of an object whose position is to be detected into a two-dimensional pattern signal; a means for storing a plurality of standard patterns that respectively match the pattern, and a plurality of partial patterns having a positional relationship in the predetermined distance and direction from the two-dimensional pattern signal obtained by the converting means, and maintaining the positional relationship. means for sequentially cutting out the plurality of standard patterns while shifting their positions; a comparison means for comparing the plurality of standard patterns stored in the storage means with the plurality of partial patterns sequentially cut out by the cutting means; and the comparison means 1. A position detecting device comprising: detecting means for detecting the position of the object based on the position of a partial pattern for which a match has been detected. 2. The position detection device according to claim 1, wherein a part of the standard pattern is a mask pattern. 3. The detecting means is a means for determining that a position of a specific shaped part within the object has been detected when a predetermined number or more of the plurality of cut out partial patterns among the plurality of standard patterns match. A position detection device according to claim 1 or 2, characterized in that: 4. The cutting means also cuts out the plurality of partial patterns that are shifted in position by the predetermined distance and direction from the image pattern obtained by the converting means, and the detecting means cuts out the plurality of partial patterns that are shifted in position by the predetermined distance and direction, and the detection means Compare the pattern with the standard pattern above,
The position according to claim 1, wherein the detection means detects the position of the specific shaped part in the object from the position of the cut out partial pattern when the comparison result satisfies a predetermined matching relationship. Detection device.