JPS63275129A - Object shape inspection method - Google Patents

Abstract

PURPOSE:To determine accurately a loop shape, and improve the degree of labor saving and quality reliability, by a method wherein an aggregate of luminous flux in the form of a wedge having a small nose angle and different color tones is formed by an optical system to illuminate a metal thin wire loop, whose image is sensed and subjected to an image processing to judge the loop shape. CONSTITUTION:When a luminous flux 3 in the form of a wedge having neighboring luminous fluxes 1..., 2..., which have the same focus 6 and show red and blue, is radiated on metal thin wires 4 and 6, an image of the metal thin wires is obtained, in which two colors are alternately arranged. That is, the parallel luminous flux of a laser beam 16 is turned into a grating type by a color streaking filter, and extended in one direction by a convex lens 20. When this luminous flux is again converged in one direction by a convex lens 21, a plurality of wedge type luminous fluxes are obtained. By applying a half-mirror 22, the wedge type luminous flux 3 is divided into beams, and these divided fluxes are projected on the whole part of a metal thin wire loop 4a-4e arranged on a pellet 23 surface. The reflected light is sensed by a camera 23, and the obtained image data are subjected to operational processing by a processing equipment 24, to judge the quality. Thereby, automation is enabled, and the reliability of inspection can be improved, because the quantitative assay for reference is enabled.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is for automating the visual inspection process applied to semiconductor devices, and in particular for automating the visual inspection process applied to semiconductor devices. This is used for 100% inspection of loop shapes.

(Conventional technology) As is often the case in the semiconductor industry, there is a wave of automation, and in order to contribute to C and D caused by the recent harsh economic environment, various types of automation are required and development is required. is in progress.

Inspections for the thermocompression bonding process applied to integrated circuit devices can be roughly divided into fine metal wire inspection and ball inspection, but the latter is relatively automated as it can be determined by moving the plane formed in the X and Y directions. In contrast, loop shape inspection of thin metal wires obtained by thermocompression bonding processes is difficult to automate because the object is a three-dimensional shape, and the reality is that the loop shape inspection relies on visual inspection.

Manual visual inspection is extremely difficult to perform accurately because there are individual differences in the judgment criteria and the loop can only be seen from above, and the reliability of the inspection is naturally limited because it involves sampling. However, this visual inspection is greatly hindered by the automation of all semiconductor device assembly and assembly processes.

(Problems to be Solved by the Invention) In such a visual inspection, it is difficult to quantify the criteria for judgment by the operator, and since limit samples are used, there are individual differences in the inspection.

Furthermore, judgment criteria change depending on the worker's physical condition and preconceived notions, and when working for a long time, fatigue may lead to oversights, and furthermore, it is difficult to accurately grasp the loop shape.

As mentioned above, since this inspection is based on sampling, it cannot be said to be sufficiently reliable, and this is a major bottleneck in systematizing the entire assembly process and automating the entire line.

The present invention provides a novel object shape inspection method that eliminates the above-mentioned difficulties.In particular, it aims to save labor and improve quality reliability, and enables manufacturing status management and inspection of bonding equipment by connecting the bonding equipment and a host computer. The purpose is to enable statistical quality control by accumulating result data.

[Structure of the invention]

(Means for solving the problem) After finishing the thermocompression bonding process necessary for the semiconductor element, the lead frame to which the semiconductor element is die-bonded is transported to a predetermined position and then positioned. An optical system is placed to illuminate the attached loop of thin metal wire.

This optical system forms a wedge-shaped collection of light beams with a small cutting edge angle and different tones, and uses this to image the loop of the thin metal wire, and through image processing, the shape of the loop is determined. .

(Function) As described above, the optical system uses a wedge-shaped light beam, and the adjacent light beams have different color tones. Although it is possible to use the brightness and darkness reflected on the thin metal wire, there is an unavoidable problem that if the dark area and the abnormal area match, it will become undetectable.
Adopt different tones of luminous flux.

Moreover, since the difference in color tone projected on the thin metal wire corresponds to the change in the loop height, it is possible to determine the height by processing the image data obtained by imaging this.

Therefore, it is possible to automate the reliance on visual inspection, quantify the pass/fail judgment, and provide highly reliable shape inspection.If a laser beam is used as the light source of this illumination optical system, the diameter will be approximately 2 to 3 diameters. The detection limit is a thin metal wire up to

(Embodiment) An embodiment of the present invention will be described in detail with reference to FIG. 1 and FIG.

As shown in FIG. 4A, when the thin metal wire 4.5 is irradiated with a wedge-shaped light beam -β- having the same focus 6 and adjacent light beams 1..., 2... showing red and blue, An image of thin metal wires in which two colors are alternately arranged is obtained. (Figure 4 mouth) In this image, the relative positional relationship shows the change in the height of the metal thin wire loop. In other words, the high position of the metal thin wire loop crosses the wide part of the wedge-shaped light beam, so it emits light. The portion 7 to which the light is irradiated is long, and since the central portion of the thin metal wire 4 is at a low position and crosses the narrow portion of the wedge-shaped light beam, the portion 7 to be irradiated with light is short.

In addition, in order to reliably irradiate the thin metal wires 4 and 5 with the wedge-shaped light beam A, they are made to have a sufficient thickness in the direction perpendicular to the plane of the paper. This wedge-shaped beam diamond is obtained by the optical system shown in FIG.

As shown in the figure, a laser beam 1 is emitted from a laser light source 15.
6 is spread in a fan shape by a polygon mirror 17, first, a plate-shaped parallel light beam is created by a convex lens 18, the light beam is made into a lattice shape by a color stripe filter 19, and the lattice-shaped light beam is unified by a convex lens 2o. Expand in the direction. By focusing the light beam in one direction again using the convex lens 21, a plurality of wedge-shaped light beams can be obtained.By installing the color stripe filter 19, the convex lens 20.
The color tones obtained are shown below.

FIG. 3 shows an inspection system using this wedge-shaped light beam. A half mirror 22 is used to split the wedge-shaped light beam into beams, and the divided light beams are wired into a thin metal wire loop 4a on the surface of the pellet 23. 4e is irradiated and the reflected light is imaged by the camera 23.

In this case, since the half mirror 22 is applied, the image is taken by the camera 23 from the same direction as the main irradiation direction of the wedge-shaped light beam, so accurate observation is possible. Image data is processed by processing device 2
In step 4, arithmetic processing is performed to determine whether the loop shape is good or bad.

In the image processing device 24, this camera image is converted into a binary image by a binarization circuit (not shown), and the height of the loop is determined by the following calculation based on the converted image.

The cross-sectional boundary line of the main wedge-shaped light beam is expressed by the following equation based on the parameters of the optical system such as the focal length.

zn = an height Z,
]0's left end point parent coordinate value X1, then Z1=a, X□
By performing similar calculations for other fish, the height of each point can be determined.

In this case, it is necessary to pay attention to the order of the line segments from the start when deciding which - next formula to use.In this explanation, we used two colors, but if you increase the number to 3 or 4 colors, you may get the wrong number. The danger is /J1 less.

Incidentally, although the breaks 12 and 13 in the thin metal wire can be detected more easily than in the composite image 11, the height of the parts cannot be accurately determined.

As an example of this optical system, we have shown an example in which a polygon mirror or the like is placed in a direction that intersects the laser beam, but instead of using an expensive polygon mirror in the direction along the laser beam, a wedge-shaped light beam is generated using only a lens. Write down what you can get.

〔Effect of the invention〕

According to this method, automation is possible, and the criteria can be quantified, so the reliability of the inspection is improved, and the reliability can be increased by converting the sampling inspection to a 100% inspection.

-7-・ In addition, it is now possible to go online and provide early feedback to the bonding process, and furthermore, it is possible to manage statistical inspection data by connecting to a host computer.
The effect on mass production is extremely large.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the calculation direction of the thin metal wire loop, Figure 2
The figure shows the structure of the optical system that generates a wedge-shaped light beam.
The figure is a block diagram of an apparatus to which this method is applied, and FIG. 4A-9 is a diagram illustrating the principle of applying this method to a thin metal wire loop.

Claims (1)

[Claims] means for thermocompression bonding a thin metal wire to an electrode provided on a semiconductor element; means for thermocompression bonding the thin metal wire to another connection point; means for arranging an optical system for irradiating the loop of the thin metal wire;
This optical system includes a means for forming a collection of wedge-shaped light beams with a small cutting edge angle and different tones, a means for imaging the loop of the thin metal wire with the wedge-like light beams having different tones, and a means for imaging the loop of the thin metal wire by processing this image. 1. A method for inspecting the shape of an object, comprising means for determining the shape of a thin wire loop.