HK1231295B - Apparatus for mounting components on a substrate - Google Patents

Description

Device for mounting components on a substrate

Technical Field

The present invention relates to an apparatus for mounting components, usually electronic or optical components, in particular electrical semiconductor chips and flip chips, on a substrate. This mounting is known in the art as a soldering process or a placement process.

Background Art

Devices of this type are used in particular in the semiconductor industry. An example of such a device is a die bonder or pick-and-place machine, with which components in the form of semiconductor chips, micromechanical and microoptical components, etc., are placed and soldered onto substrates such as lead frames, printed circuit boards, ceramics, etc. The component is picked up by a bonding head at a pick-up point, in particular by suction, moved to a substrate point, and placed at a precisely defined position on the substrate. The bonding head is part of a pick-and-place system and is capable of being moved in at least three spatial directions. In order to ensure that the component is placed on the substrate with precise positioning, the precise position of the component gripped by the bonding head relative to the bonding head positioning axis and the precise position of the substrate point must be determined simultaneously.

Such devices are known from EP449481, US5878484, WO2004064472, and EP1916887. Two mirrors are arranged at a 45° angle relative to the vertical, so that the bottom side of the component projects toward the camera, allowing the component's position to be determined relative to the welding head's positioning axis. EP2373145 also discloses devices that use mirrors and a pentagonal prism to project the bottom side of the component toward the camera. In these devices, the optical axis of the camera extends parallel to the welding head's positioning axis. In the device of EP2373145, only the position of the component is determined; the position of the substrate's fixed point cannot be determined.

In recently designed industrial devices, two cameras are typically used: one camera positioned in or below the substrate plane and pointing upward to determine the component position, and another camera positioned above the substrate plane and pointing downward to determine the substrate point position. A disadvantage associated with these devices is that the bonding head must first travel from the pick-up position to the camera positioned in or below the substrate plane, and then further travel to the substrate point, often requiring a circuitous route.

Summary of the Invention

The present invention is based on the development of a device that requires only one camera to determine the position of the component and the fixed position of the substrate, and simplifies the optical structure and requires only a small space.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are incorporated into and constitute a part of this specification and, together with the detailed description, illustrate one or more embodiments of the present invention and serve to illustrate the principles and implementations of the present invention. The accompanying drawings are schematic and not drawn to scale. In the drawings:

Figures 1 and 2 show two snapshots of an apparatus for mounting components according to the invention, and

3 and 4 show alternative embodiments of separate optical deflection systems.

DETAILED DESCRIPTION

Figures 1 and 2 schematically show side views of two snapshots of an apparatus according to the invention for mounting a component 1 on a substrate location 2 of a substrate 3. The component is typically an electronic, micromechanical, or (micro)optical component, in particular a semiconductor chip and flip chip. The apparatus comprises a support 4 for the substrate 3, a pick-and-place system 5 with a soldering head 6, a single camera 7, a first optical deflection system 8, a second optical deflection system 9, a first light source 10, a second light source 11, and a third light source 12. The soldering head 6, the first optical deflection system 8, the camera 7, and the second light source 11 are fastened to a common bracket 13. The second optical deflection system 9 is fixedly arranged on the apparatus. The substrate 3 generally has a plurality of substrate locations. The term "substrate location 2" is generally understood hereinafter to mean a substrate location located in the field of view of the camera 7, wherein the beam path from the substrate location 2 to the camera 7 extends through the first optical deflection system 8 and is deflected at least once therein.

The surface of the support 4 for the substrate 3 defines a substrate plane 14. The pick-and-place system 5 comprises at least three drives for moving the carrier 13 in three spatial directions, namely, two directions extending parallel to the substrate plane 14 and a direction, referred to herein as the Z direction, extending perpendicular to the substrate plane 14. The bonding head 6 comprises a gripping axis 15 extending in the Z direction.

The camera 7 and the first optical deflection system 8 together form a first image detection system for recording an image of the substrate point 2 on which the component 1 is mounted. The camera 7, the first optical deflection system 8 and the second optical deflection system 9 together form a second image detection system for recording an image of the bottom side of the component 1 held by the welding head 6.

The pick and place system 5 is configured to pick up the corresponding component 1 at a pick-up location with the aid of a welding head 6 and to place it on a substrate location 2. For high-precision positioning, a camera 7 records images of the underside of the component 1 on the one hand and of the substrate location 2 on which the component 1 is mounted on the other hand.

The first optical deflection system 8 serves to transform the optical axis 16 of the camera 7 closer to the optical axis 17 of the gripping axis 15 of the welding head 6, which extends in the Z direction in a manner laterally offset relative to the gripping axis 15 of the welding head 6. Due to the first optical deflection system 8, the object-side optical axis 17 of the first image detection system extends from the gripping axis 15 of the welding head 6 by a distance D that is significantly smaller than the distance between the gripping axis 15 of the welding head 6 and the optical axis 16 of the camera 7.

As soon as the welding head 6 is located in a predetermined working area above the second optical deflection system 9 , the second optical deflection system 9 and the first optical deflection system 8 cooperate and bring the bottom side of the component 1 held by the welding head 6 into the field of view of the camera 7 .

In order for camera 7 to record a clear image of the bottom side of component 1 and substrate point 2 on which component 1 is placed, the optical paths of the beam paths of the first and second image detection systems must be of the same length to the greatest extent possible. The length of the beam path is adjusted by moving the carriage 13 of the pick and place system 5 in the Z direction. Therefore, the system is programmed so that, to record an image of component 1, carriage 13 is moved in the Z direction above second optical deflection system 9 to a predetermined height H ₁ above substrate plane 14, so that at least during the travel of component 1 above second optical deflection system 9, the bottom side of component 1 is in the focal plane of camera 7. This allows camera 7 to record a clear image of the bottom side of component 1 during movement of component 1. Furthermore, to record an image of substrate point 2, carriage 13 is raised to a predetermined height H ₂ above substrate plane 14, so that substrate point 2 is in the focal plane of camera 7, allowing camera 7 to record a clear image of substrate point 2. The two heights _H1 and _H2 are dimensioned so that the optical length of the beam path between the bottom side of the component 1 and the camera 7 and the optical length of the beam path between the substrate point 2 and the camera 7 are equally large, so that either the bottom side of the component 1 or the substrate point 2 is located in the focal plane of the camera 7. This applies when _H2 > _H1 , as shown in Figures 1 and 2.

The device is programmed so that first an image of each substrate point 2 of the substrate 3 is recorded and then components 1 are mounted one after another on the substrate points 2 of the substrate 3. However, the device can also be programmed so that during each mounting process an image of the bottom side of the component 1 is recorded and then an image of the associated substrate point 2 is recorded.

1 shows the apparatus in a state in which the carriage 13 is located at a predetermined height H ₂ , in a position such that a predetermined substrate point 2 is within the field of view of the camera 7 , so that the camera 7 can record a sufficiently clear image of said substrate point 2 .

2 shows the device in a state in which the bracket 13 is located at a predetermined height H ₁ and in the working area of the second optical deflection system 9 so that the bottom side of the component 1 is located in the field of view of the camera 7 , so that the camera 7 can record a sufficiently clear image of the bottom side of the component 1 .

According to the first embodiment, the first optical deflection system 8 includes a deflection prism 18 and a reflection mirror 19. The deflection prism 18 is an object with a triangular cross-section, and reflects a light beam 20 originating from the substrate plane in the Z direction on two surfaces 21 and 22. The bottom surface 22 of the triangular deflection prism 18 extends parallel to the substrate plane 14, and the light beam 20 undergoes a second reflection on this bottom surface 22. The second surface 21 is a mirror surface and forms a predetermined angle α with the bottom surface 22, and the light beam 20 undergoes a first reflection on this second surface 21. This angle α is determined so that the light beam 20 is totally reflected on the bottom surface 22. To ensure total reflection, the angle α must satisfy Snell's refraction law:

α＜90°-arcsin(n(air)/n(deflecting prism 18)),

Here, n(air) represents the refractive index of air, and n(deflecting prism 18) represents the refractive index of the material constituting the deflecting prism 18 .

According to the first embodiment, the second optical deflection system 9 includes a symmetrical deflection prism 24 for reflecting a light beam 25 originating from the bottom side of the component 1 in the direction of the gripping axis 15 three times until it exits the deflection prism 24 again parallel to the gripping axis 15 and is incident on the first optical deflection system 8. The light source 10 is arranged on one side of the deflection prism 24, below it. The deflection prism 24 has an isosceles triangle in cross section and has three surfaces 26, 27, and 28, the angle β between which is selected so that the light beam 25 is totally reflected at the upper surface 26. The angle β must therefore satisfy the condition:

β＜90°-arcsin(n(air)/n(deflecting prism 24)).

Due to total internal reflection, the upper surface 26 does not need to be silvered, so that light reflected on the component 1 can enter the deflection prism 24, be internally reflected on all three surfaces 26, 27, 28, can leave the deflection prism 24 again, and can then be guided to the camera 7 by means of the first optical deflection system 8.

Surface 27 is advantageously silver-plated. If light source 10 is present, held by welding head 6, for bottom-side illumination of component 1, surface 28 is unexposed, but additional triangles 29 and a portion of deflection prism 24 form a beam splitter. Beam splitting occurs on surface 28, typically via frustrated total internal reflection. Surface 28, acting as a beam splitter layer, can also be formed as a polka dot pattern. Polka dots are a pattern of reflective dots arranged in a matrix.

According to a second embodiment, as shown in Figures 3 and 4, the first optical deflection system 8 includes a mirror 23, which replaces the deflection prism 18 and is angled relative to the vertical. This embodiment requires more space than the first embodiment, resulting in a greater distance D between the gripping axis 15 of the welding head 6 and the optical axis 17 than in the first embodiment, as the required material thickness of the mirror 22 increases this distance D. The mirrors 19 and 23 can be tilted 45° relative to the vertical, but can also be tilted at angles greater or less than 45°. However, this results in a greater space requirement for the mirror 19 in the downward direction of the substrate plane 14 and for the mirror 23 in the direction of the welding head 6.

As shown in Figures 3 and 4, the second optical deflection system 9 according to the second embodiment further comprises a beam splitter cube 30, a penta-prism 31, and an optional light-transmitting body 32, which is preferably arranged seamlessly between the beam splitter cube 30 and the penta-prism 31. The light beam 25 originating from the bottom side of the component 1 is deflected by 90° in the beam splitter cube 30, reflected on two surfaces in the penta-prism 31, and thereby deflected by a total of another 90°, so that the light beam emitted from the penta-prism 31 extends parallel to the gripping axis 15 of the welding head 6 and parallel to the optical axis 16 of the camera 7. When the light-transmitting body 32 is seamlessly inserted between these two elements and consists of the same material, it reduces the optical path and prevents reflections of the light beam 25 during passage from the beam splitter cube 30 and during entry into the penta-prism 31.

The optical components of the two deflection systems 8 and 9 consist of a light-transmitting material, preferably glass or a transparent plastic with a relatively high refractive index.

Light sources 10 and 12 serve to illuminate the bottom side of component 1. Light source 10 is preferably arranged below beam splitter cube 30. Beam splitter cube 30 therefore serves to inject the light emitted by light source 10 and to decouple the light reflected on the bottom side of component 1. Light source 10 illuminates the bottom side of component 1 coaxially with optical axis 16, so that the smooth, reflective bottom side of component 1 is optimally illuminated exclusively, while light source 12 is designed as a lateral light source, so that the rough, diffusely reflective bottom side of component 1 is optimally illuminated.

The light source 11 is used to illuminate the substrate point 2. The light source 11 preferably comprises an illumination device, which is preferably arranged on all sides around the optical axis 17 of the first image detection system and which illuminates the substrate point to be illuminated in the form of lateral light. It may also include coaxial illumination.

During travel of the welding head 6 over the second optical deflection system 9 the camera 7 can record images of the underside of the component 1 , ie without stopping, or the device can stop the welding head 6 over the second optical deflection system 9 so that images are recorded.

In all embodiments, the mirror 19 can be omitted and the camera 7 can be arranged (in a twisted manner) such that its optical axis 16 coincides with the direction of the light beam 20 after reflection at the deflection prism 18 or the mirror 23 .

The present invention provides at least the following beneficial effects:

- Only a single camera is required to determine the exact position of the component gripped by the bonding head and the exact position of the substrate point.

- A first optical deflection system moves the optical axis of the camera closer to the gripping axis of the welding head and thus increases the working range of the machine.

The first optical deflection system results in a reduction of the optical path length from the underside of the component to the camera and thus reduces the difference between the heights _H1 and _H2 required for adjusting the focal plane of the camera.

The second optical deflection system allows recording the underside of the component during travel without having to stop the welding head. This is because the image of the underside of the component still appears stationary as long as the component is located in the predetermined working area of the second optical deflection system.

The first optical deflection system is rigidly connected to the welding head and the second optical deflection system is fixedly arranged on the machine. Thus, no movement of one or the other deflection system or parts thereof is necessary during the welding process.

The heights H ₁ and H ₂ can be adjusted to the specific needs of the installation via the choice of the geometry and material of the element 24 or of the elements 30 , 31 and 32 .

Although the embodiments and applications of the present invention are shown and described, it is apparent that those skilled in the art, having benefit of this disclosure, can make more modifications than those described above without departing from the concept of the present invention. Therefore, the present invention is not limited except in the spirit of the claims and their equivalents.

Claims (5)

1. An apparatus for mounting a component (1) on a substrate (3), comprising: A support portion (4) for the substrate (3), wherein the surface of the support portion (4) defines a substrate plane (14). A pick-up and placement system (5) having a welding head (6), wherein the pick-up and placement system (5) is configured to pick up a component (1) at a pick-up point using the welding head (6) and place the component on a substrate point (2). A camera (7) is used to detect the position of the component (1) held by the welding head (6) and to detect the position of the substrate anchor point (2) to which the component (1) is to be mounted. The first optical deflection system (8), and Second optical deflection system (9), in The camera (7) has an optical axis (16), The pickup and placement system (5) includes a replaceable bracket (13) on which the first optical deflection system (8), the camera (7), and the welding head (6) are secured. The second optical deflection system (9) is fixedly arranged on the device. The first optical deflection system (8) and the camera (7) constitute a first image detection system for recording images of the substrate fixed point (2). The object-side optical axis (17) of the first image detection system is parallel to the gripping axis (15) of the welding head (6) and extends a distance (D) from the gripping axis (15) of the welding head (6). This distance (D) is less than the distance between the gripping axis (15) of the welding head (6) and the optical axis (16) of the camera (7). The first optical deflection system (8), the second optical deflection system (9), and the camera (7) constitute a second image detection system for recording images of the bottom side of the component (1), and The device is programmed to move the bracket (13) above the second optical deflection system (9) at a predetermined height _H1 above the substrate plane (14) during the transfer of the component (1) from the pickup point to the substrate point (2) in order to record an image of the component (1), such that during the travel above the second optical deflection system (9), the bottom side of the component (1) is located at the focal plane of the camera (7), and In order to record the image of the substrate fixed point (2), the bracket (13) is raised to a predetermined height _H2 above the substrate plane (14), so that the substrate fixed point (2) is located at the focal plane of the camera (7). The dimensions of the two heights _H1 and _H2 are determined such that the optical length of the beam path between the bottom side of the component (1) and the camera (7) is equal to the optical length of the beam path between the substrate fixed point (2) and the camera (7). 2. The apparatus of claim 1, wherein the first optical deflection system (8) comprises a deflection prism (18) and a reflector (19). 3. The apparatus of claim 1, wherein the first optical deflection system (8) comprises two mirrors (19, 23). 4. The apparatus according to any one of claims 1 to 3, wherein the second optical deflection system (9) comprises a symmetrical deflection prism (24). 5. The apparatus according to any one of claims 1 to 3, wherein the second optical deflection system (9) comprises a beam splitter cube (30), a pentagonal prism (31), and a light-transmitting body (29) seamlessly disposed between the beam splitter cube (30) and the pentagonal prism (31).