JPH0862425A - Light guide device - Google Patents

Abstract

(57) Abstract: A light guide device that can be used to illuminate an object from the side is also provided. SOLUTION: The light guide 6 has an opening 11, and the light of the light guide 6 is guided into this opening so that the object 1 is irradiated from the side surface. The opening 11 has a wall 5 configured as a deflecting mirror, by which the reflected light from the object 1 is extracted from the opening 11 and guided. This allows the side and top surfaces of the object to be observed to be inspected simultaneously. This device is used, for example, in visual inspections carried out in the assembly of semiconductor chips on substrates. Defective chips or assemblies can be identified and excluded. A camera and an image recognition device can perform automatic inspection of assembled semiconductor chips.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide device for illuminating an object from the side, for example.

[0002]

It is already known to use light guides for illuminating objects when it is not possible to place the illuminating device directly for space reasons. When observing an object through a microscope, for example, a light guide is used in which the light from a light source is directed towards the surface of the object. This is because the distance between the object and the microscope objective is generally very small. In the case of microscopic observation, another problem arises in that only the surface facing the objective lens can be optically scanned. When it is desired to observe the side of the object, the object must be correspondingly rotated relative to the objective lens. Especially during chip assembly in semiconductor manufacturing, it is necessary to optically inspect both the cutting edges of the chips and also the soldered or adhesive connections to the substrate. Rotating the individual chip edges is not only very time consuming, but also very difficult due to the significantly small size of one chip, which can easily lead to unwanted damage. Thus, such visual monitoring, for example in quality control, is not only very costly or complicated, but also considerably unreliable because not all inspectors can identify the defects.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is therefore to avoid the abovementioned disadvantages and to provide a light guide, for example for lateral irradiation of an object.

[0004]

According to the invention, the problem is that the light guide has an opening into which the object is illuminated from the side. The light is guided and the opening preferably has four walls, which are configured as deflection mirrors, by means of which the light reflected from the object is extracted from the opening of the light guide. It is solved by being guided and guided.

An advantage of the light guide according to the present invention having the above-mentioned configuration over the prior art is that an object can be illuminated from inside or below the light guide from all side surfaces. It is particularly advantageous if, via a wall configured as a deflecting mirror, the light reflected on the side of the object is extracted from the opening of the light guide, for example, so that it is projected onto the objective lens of the microscope located above the object. Is to be guided. With this advantageous configuration, it is possible to illuminate not only the surface of the object facing the microscope, but also its sides, without having to rotate or tilt the object in any way. This allows the object to be inspected more thoroughly and is not damaged by handling. By showing all critical aspects at the same time, the speed of optical inspection is significantly increased.

According to the constitution described in the dependent claims,
Advantageous embodiments of the light guide device described in 1. are possible. It is particularly advantageous to select the wall tilt angle taking into account the refractive index of the light guide material used. This allows the tilt angle to be chosen such that all light reflected from the side of the object is deflected as much as possible.
Thus, the luminous efficiency can be optimized and the total reflection can be avoided.

In practice, it has been found to be suitable:
The angle of inclination of the wall with respect to the horizon is chosen to be about 45 °. This is because in this way the light reflected almost horizontally from the sides can be vertically deflected upwards and is therefore directly projected onto the objective lens of the microscope.

The sufficient height of the effective light exit surface on one wall allows the entire side surface of the object to be illuminated, so that one complete image can be obtained without tracking adjustments.

At least one reflector is arranged at the outer edge of the light guide for the purpose of enhancing the illumination on the side of the object. A further reflector can be arranged above this at least one reflector, which is oriented towards the upper surface of the object, so that the upper surface of the object is also fully illuminated and at the same time with the side surfaces in one microscope. Can be observed.

It is more preferable to provide the light guide with a light source whose brightness can be adjusted. This allows the brightness to be controlled in the microscope to produce images with as much contrast as possible.

By combining this light guide with a microscope or a camera device, it is possible to inspect both the surface and the side of the object at the same time. For example, in an optical inspection of a semiconductor chip adhered or soldered to a substrate or a lead frame, its cut surface or interface portion can be inspected without rotating or tilting.

If a camera equipped with an automatic image recognition device is used as an optical inspection device, the visual inspection can be automated by comparing the stored reference image with the actual image. Defective chips can be characterized by suitable marking devices and filtered out.

Next, an embodiment of the present invention will be described with reference to the drawings.

[0014]

1 is a sectional view of one embodiment of a light guide 6. The light guide 6 has a substantially hopper shape and has an opening in the center thereof, and the object 1 to be irradiated is placed in the opening. The object 1 can be, for example, a semiconductor chip arranged on the substrate 19. For example, in the case of manufacturing semiconductors, one or more semiconductor chips 1 whose quality is to be optically inspected one after another on one lead frame configured as a substrate.
Can be arranged.

The light guide 6 preferably has four walls 5 arranged at right angles to each other, which are configured as inclined surfaces at the lower part of the light guide 6 and which are perpendicular to the semiconductor chip. The light reflected from the wall is deflected upward. In addition, a reflector 4 is provided in the lower region at the outer edge of the light guide 6, which strongly deflects the light of the light guide towards the opening 11. An opening for a light source 12 is provided at one or more suitable locations on the periphery of the light guide 6, the light of this light source being deflected through the light guide to the opening 11. These light sources are connected to the adjustable power supply unit 18, so that the brightness of the light guide 6 can be set and adjusted. An optical inspection device 7 is provided through the light guide 6.
However, it is arranged so that the beam deflected by the wall 5 is projected onto the lens system of this inspection device. The optical inspection device 7 may be a microscope that inspects the surface and side surfaces of the object 1. Furthermore, a camera 16 can be connected to the inspection device for recording the captured surface of the object.

In a further embodiment of the invention, the camera is arranged to be connected to an image recognition device 17, which device concerns a good object 1 and / or a defective object 1. The pattern is stored. By comparing the stored photograph image with the image currently recorded by the camera 16, an automatic assessment of the object can be made. If a defective object 1 is found, it can be marked at the appropriate place on the object, for example with colored points.

The light guide 6, together with its opening 11, is constructed so that there is no risk of damaging the object 1 both during adjustment and during observation. In particular, in the case of a movably arranged light guide 6, this light guide is designed, for example, so that it does not damage adjacent objects. Further, the hopper shape of the light guide 6 is aligned with the optical inspection device 7 so that the focus adjustment and the change of the magnification are not disturbed.

FIG. 2 shows an enlarged plan view of the light guide 6. An opening 11 is shown in the center of the light guide 6, which is preferably of square design and has a larger predetermined size for the object 1. The walls 5 surround the openings 11, so that the objects 1 can be illuminated simultaneously from all sides through these walls 5. At a suitable location, the light guide 6 is provided with an opening to accommodate the light source 12.
These light sources can also be arranged at the corners of the light guide 6.

In FIG. 3, the light guide 6 is shown here in cross section. In particular, the inclination angle α of the wall 5 with respect to the horizontal is shown here. In this case, the angle α is chosen such that as much light as possible is coupled out of the light guide and directed to the side 9 of the object 1. On the other hand, the reflected light from the wall 5 should be deflected upwards in order to be projected onto the optical inspection device 7. The angle α can be chosen depending on the material, taking into account the refractive index, for example n = 1.5, and is set so that as much light as possible is coupled out of the light guide 6. In this case, an angle of about 45 ° has proven suitable. At this time, the wall 5 is formed at a height such that its effective surface reflects the image of the entire side surface 9.

A reflector 4 is provided on the outer peripheral lower edge of the light guide 6, and the light of the light guide 6 is guided toward the opening 11 by these reflectors. Due to the predetermined angle α of the wall 5 at n = 1.5, these reflectors are preferably tilted at an angle α ₁ of about 30 ° with respect to the horizontal, so that, as far as possible based on the law of refraction, Much light will pass through the wall 5. And these reflectors are preferably specular, so there is no loss of light. Another reflector 10 is provided above the reflector 4 and these reflectors project a part of the light of the light guide 6 onto the upper surface 13 of the object 1. As a result, the upper surface 13 of the object 1 can be inspected by the optical inspection device 7 at the same time as the side surface 9.

The light beams A, B, C and D in the light guide 6 are written for the purpose of better understanding. These light beams are deflected by the reflector 4 towards the opening 11 and thus illuminate the side surface 9 of the object 1. The flanks 9 reflect these beams so that they are at the wall 5 a beam A ′,
It is deflected in the direction of the optical inspection device 7 as B ', C', D '. As a result, the optical inspection device 7 can simultaneously identify the side surface 9 and the surface 13 of the object 1.

An advantageous use of the light guide 6 in combination with the optical inspection device 7 is visual inspection in the manufacture of electronic components. It can be expected as a general usage also in the field of material inspection and animal and plant fields.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment combined with an optical inspection device.

FIG. 2 is a plan view of the above embodiment.

FIG. 3 is a cross-sectional view of the above embodiment.

[Explanation of symbols]

 1 Object 4 Reflector 5 Wall 6 Light Guide 7 Optical Inspection Device 12 Light Source 17 Image Recognition Device 18 Power Supply Unit 19 Board

Claims (13)

[Claims] 1. A light guide device for illuminating an object, wherein the light guide (6) has an opening (11) into which the object (1) is laterally illuminated. The light from the light guide (6) is guided to the opening (1
1) has a wall (5), which is configured as a deflection mirror, by means of which the light reflected from the object (1) emerges from the opening (11) of the light guide (6). A light guide device characterized by being taken out and guided. 2. A light guide device according to claim 1, wherein the inclination angle (α) of the wall (5) is selectable depending on the refractive index of the material of the light guide (6). 3. The inclination angle (α) of the wall (5) is about 45.
The light guide device according to claim 1 or 2, wherein 4. Light guide device according to claim 3, wherein the effective light exit surface of the wall (5) has at least the height of the object (1). 5. At least one reflector (4) is provided on the outer edge of the light guide (6), by means of which the light of the light guide (6) is opened (11). ) The light guide device according to any one of claims 1 to 4, which is deflected toward. 6. A further reflector (10) is arranged above the reflector (4), whereby a part of the light of the light guide (6) is directed to the object (1) by the further reflector (10). Light guide device according to claim 5, which is deflected to the upper surface (13) of the. 7. The light guide (6) is at least one.
7. Light guide device according to any one of the preceding claims, comprising one light source (12), the brightness of at least one light source (12) being controllable. 8. The light guide (6) is connected to an optical inspection device (7), and the objective lens of the optical inspection device (7) mainly receives reflected light from the wall (5). So that the opening (1) of the light guide (6)
The light guide device according to any one of claims 1 to 7, which is arranged above 1). 9. The light guide device according to claim 8, wherein the optical inspection device (7) is an optical microscope and / or a camera device. 10. The optical inspection device (7) comprises an object (1).
10. The light guide device according to claim 8, which can be used, for example, for optical material inspection of semiconductor chips. 11. The optical inspection device (7) is connected to an automatic image recognition device (17), the optical inspection device (7) moving the object (1) relative to the light guide (6). 11. Light guide device according to claim 10, which is configured for automatic positioning and / or for defect detection of the object (1). 12. The light guide device according to claim 11, wherein the optical inspection device (7) is arranged to mark the object (1) when a defect is detected. 13. A method of using the light guide device according to claim 8, wherein the light guide (6) together with the optical inspection device (7) is used for visual inspection, for example, when manufacturing electronic components. A method of using a light guide device, which is characterized in that it is used.