Patent Application
20180317353
Applicant hereby claims foreign priority under 35 U.S.C. § 119 from Swiss Application No. 00575/17 filed Apr. 28, 2017, the disclosure of which is herein incorporated by reference.
The invention relates to an apparatus and a method for mounting components on a substrate, typically electronic or optical components, in particular semiconductor chips and flip chips, on a substrate. In the field, the mounting is also referred to as bonding process or assembly process.
Apparatuses of this type are particularly used in the semiconductor industry. Examples of such apparatuses are Die Bonders or Pick and Place machines, with which components in the form of semiconductor chips, flip chips, micromechanical, micro-optical and electro-optical components, and the like are deposited on substrates such as leadframes, printed circuit boards, ceramics, etc. and bonded. The components are picked up by a bond head at a removal location, in particular sucked in, moved to a substrate location and deposited at a precisely defined position on the substrate. The bond head is part of a Pick and Place system, which enables movement of the bond head in at least three space directions. In order to enable the component to be positioned accurately on the substrate, both the exact position of the component gripped by the bond head with respect to the positioning axis of the bond head and the exact position of the substrate place must be determined.
Mounting devices available on the market achieve in the best case a positioning accuracy of 2 to 3 micrometers with a standard deviation of 3 sigma.
The object of the invention is to develop an apparatus and a method, which achieve a higher placement accuracy compared to the state of the art.
The apparatus according to the invention comprises a bond head with a component gripper, a first drive system for moving a carrier over relatively long distances, a second drive system attached to the carrier for moving the bond head back and forth between a nominal working position and a stand-by position, a drive attached to the bond head for rotating the component gripper or a rotary drive for rotating the substrate about an axis running perpendicularly to the substrate surface, at least one substrate camera attached to the carrier and at least one component camera. The bond head or the component gripper contains at least one reference mark used by both the at least one component camera and the at least one substrate camera to determine the position of the component relative to the bond head or the position of the bond head relative to the substrate location, respectively. The substrate contains at least one substrate mark and the component contains at least one component mark or a structure suitable to serve as component mark.
The first drive system serves to move the bond head over relatively long distances with relatively low positioning accuracy. The second drive system serves to move the bond head back and forth between the nominal working position and the stand-by position. In the nominal working position, the bond head covers the substrate mark(s) attached to the substrate and is therefore temporarily moved to the stand-by position where the bond head no longer covers the substrate mark(s) so that the substrate camera(s) can take an image of the substrate mark(s). The second drive system preferably serves also to move the bond head over relatively small distances with very high positioning accuracy, i.e. to perform high-precision correction movements of the bond head. Alternatively, a third drive system can be provided to perform high-precision correction movements of the substrate.
The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more embodiments of the present invention and, together with the detailed description, serve to explain the principles and implementations of the invention. The figures are not to scale. In the drawings:
The mounting apparatus includes a bond head 3, a feeding unit 4 for supplying the components 1, a device 5 for feeding and providing the substrates 2, and a first drive system 6 for a carrier 7 and a second drive system 8 for the bond head 3. The second drive system 8 is attached to the carrier 7. The apparatus further includes at least one component camera 9 and at least one substrate camera 10. The substrate camera(s) 10 is/are attached to the carrier 7. The bond head 3 comprises a component gripper 11, which is rotatable about an axis 12. In the following, a component held by the bond head 3 is referred to as component 1a. The component gripper 11 is, for example, a vacuum-operated suction element that sucks in a component 1.
The feeding unit 4 comprises, for example, a wafer table, which provides a plurality of semiconductor chips, and a flip device, which removes one semiconductor chip after the other from the wafer table and provides it as flip chip for transfer to the bond head 3. The feeder unit 4 can also be a feeder unit that provides flip chips or other components one after the other for transfer to the bond head 3.
The bond head 3 or the component gripper 11 contains at least one reference mark 13 (
The first drive system 6 serves to transport the bond head 3 over relatively long distances, namely from a component removal location, where the bond head 3 takes the component 1 to be mounted from the feeder unit 4, to the substrate 2, where the bond head 3 places the component la on a substrate place of the substrate 2. The requirements for the position accuracy of the first drive system 6 are relatively modest, a position accuracy of +/−10 μm is usually sufficient. The first drive system 6 is designed, for example, as a so-called “gantry” with two or more mechanically highly stable axes of motion, of which two axes of motion allow movements of the carrier 7 in two horizontal directions running perpendicular to each other.
The up and down movements of the bond head 3 to remove a component 1 from the feeder unit 4 and to place the component la on the substrate place of the substrate 2 can be done in different ways, for example
The second drive system 8 serves on the one hand to move the bond head 3 into a stand-by position, as described below in more detail, and on the other hand to enable high-precision correction movements of the bond head 3 in two different horizontal directions. The second drive system 8 comprises a first drive for moving the bond head 3 along a first direction designated as u-direction and a second drive for moving the bond head 3 along a second direction designated as v-direction. The directions u and v run in horizontal direction and preferably orthogonally to each other. The bond head 3 comprises, optionally, a drive 14 for the rotation of the component gripper 11 around the axis 12. The device 5 for feeding and providing the substrates 2 may contain a rotary drive 15 in order to rotate the substrate 2 about an axis running orthogonally to its surface in order to alternatively eliminate any angular errors in this manner.
The component camera 9 or the several component cameras 9 serve to detect the position of the component 1a in relation to the position of the reference mark(s) 13. The substrate camera 10 or the substrate cameras 10 serve to detect the position of the substrate place on which the component la is to be placed, in relation to the position of the reference mark(s) 13. Each component camera 9 and each substrate camera 10 comprises an image sensor 17 and an optics 18 (
The component camera(s) 9 is/are, for example, arranged stationary on the apparatus and the bond head 3 is moved on its way from the component removal location to the substrate location above the component camera(s) 9 and is preferably, but not necessarily, stopped for taking one or more images. The component camera(s) 9 can alternatively be attached to the carrier 7. For example, either the component camera(s) 9 or the bond head 3 is/are attached to the carrier 7 by means of a retractable and extendable swivel mechanism. The component camera(s) 9 or the bond head 3, respectively, is then retracted into an image capture position while moving from the component removal location to the substrate location, so that one or more images per component camera 9 can be captured during the move. For the removal of the component 1 from the feeder unit 4 and for recording the images with the substrate camera(s) 10 and for depositing the component la, the component camera(s) 9 is/are extended into a stand-by position and the bond head 3 is extended into its working position.
The range of motion of the second drive system 8 is relatively small and even very small compared to the range of motion of the first drive system 6. The second drive system 8 must be able to move the bond head 3 from a nominal working position to the stand-by position in which the substrate marks 23 are not covered by the bond head 3 on the one hand, and on the other hand enable high-precision correction movements of the bond head 3 in two different horizontal directions. For this purpose, it is sufficient if the range of motion of the second drive system 8 is relatively long in one horizontal direction and very short in the other horizontal direction. The range of motion in one direction is typically a few ten millimeters, for example 20 mm or 30 mm or more, the range of motion in the other direction is typically (only) a few micrometers.
The nominal working position of the bond head 3 is a position that differs only slightly from the final position which the bond head 3 occupies in the last step of the assembly process. The accuracy requirements for the nominal working position are relatively low, as any deviation from the nominal working position is automatically compensated later in the assembly process.
The apparatus is configured, to lower the carrier 7 and/or the bond head 3 and/or the component gripper 11 so far that the underside of the component la is located at an extremely low height of typically only 50-200 μm above the substrate surface, and only then take an image of the substrate mark(s) 23 with the substrate camera(s) 10. In doing so, it is achieved that the only movement after the determination of the actual position of the component 1a with respect to its set position on the substrate place and after the execution of the high-precision correction movements is only the lowering movement of the carrier 7 and/or the bond head 3 and/or the component gripper 11 and that this distance is so short that any displacements in the u-direction and in the v-direction during this lowering movement are in the submicrometer range.
From the moment when the carrier 7 has reached its position in the area of the substrate 2, the position of the substrate camera(s) 10 relative to substrate 2 no longer changes. From this moment on, only the position of the bond head 3 is changed, namely by means of the second drive system 8. The position of the reference mark(s) 13 can therefore be monitored until the component la is placed on the substrate 2 and any new deviation from its set position that might occur during the final lowering phase of the component 1a can be corrected. The components can therefore be mounted with an unprecedented precision in the submicrometer range.
With this apparatus a similarly high positioning accuracy can be achieved, even if during the last phase of the lowering of the component 1a, further correction movements of the substrate 2 that may still be necessary and that are carried out can no longer be checked for correct attainment.
The mounting of a component 1 is now explained in detail. The mounting method according to the invention comprises the following steps A to O. The steps can be in part executed in a different order.
With a mounting apparatus, in which the component camera(s) 9 is/are arranged stationary, step B is carried out by: With the first drive system 6 moving the carrier 7 to the component camera 9 or the component cameras 9. In a mounting apparatus in which the component camera(s) 9 is/are attached to the carrier 7, step B is performed by: Moving the component camera(s) 9 and the bond head 3 relative to each other into an image acquisition position.
The components 1 contain component marks 22 (
In a mounting apparatus in which the component camera(s) 9 is/are attached to the carrier 7, step C is followed by the step: Moving the component camera(s) 9 and the bond head 3 relative to each other so that the bond head 3 is in its normal working position and, if necessary, the component camera(s) 9 is in a stand-by position.
The first correction vector comprises three components Δx1, Δy1 and Δφ1, wherein Δx1 designates the displacement of a reference point of the component 1a in a first direction designated as x1-direction and Δy1 the displacement of the reference point of the component 1a in a second direction designated as y1-direction and Δy1 designates the rotation of the component 1a around the reference point of the component 1a with respect to the reference mark(s) 13. The components Δx1 and Δy1 are given in pixel coordinates of the component camera(s) 9, the component Δφ1 is an angle. The first correction vector is a null vector, if the the actual position of the component 1a already corresponds to its set position.
The first correction movement comprises three correction values Δu1, Δv1 and Δθ1. The correction values Δu1 and Δv1 are calculated from the components Δxi, Δy1 and Δθ1. The correction value Δθ1 is calculated from the angular error Δφ1. The correction values Δu1, Δv1 and Δθ1 are all given in machine coordinates of the corresponding drives. The correction values Δu1 and Δv1 indicate the distances by which the second drive system 8 must move the bond head 3 (in the apparatus shown in
The distance D is typically about 50-200 micrometers, but is not limited to these values. However, the distance D is so small that when the component la is subsequently lowered to the substrate place, usually no displacements of the component la occur in the directions u and v that lead to a significant position error.
Steps F, G and H can be executed one after the other or simultaneously, i.e. in parallel. The carrier 7 and thus also the substrate camera(s) 10 attached to the carrier 7 are no longer moved during the following, remaining steps.
During steps A to G, the bond head 3 is usually in its nominal working position. The substrate camera(s) 10 does not see the substrate marks 23 because the bond head 3 covers them. The position of the stand-by position is selected such that the bond head 3 does not cover the substrate mark(s) 23.
The second correction vector comprises three components Δx2, Δy2 and Δφ2, wherein Δx2 designates the displacement of the reference mark(s) 13 in a first direction designated as x2-direction and Δy2 the displacement of the reference mark(s) 13 in a second direction designated as y2-direction and Δφ2 designates the rotation of the reference mark(s) 13 with respect to the substrate place. The components Δx2 and Δy2 are given in pixel coordinates of the substrate camera(s) 10, the component Δφ2 is an angle.
The second correction movement comprises three correction values Δu2, Δv2 and Δθ2. The correction values Δu2 and Δv2 are calculated from the components Δx2, Δy2 and Δφ2. The correction value Δθ2 is calculated from the angular error Δφ2. The correction values Δu2, Δv2 and Δθ2 are all given in machine coordinates of the corresponding drives. The correction values Δu2 and Δv2 indicate the distances by which the second drive system 8 must move the bond head 3 (in the apparatus shown in
The displacements by the correction values Δu1, Δv1, Δu2 and Δv2 are carried out by the second drive system 8 for the apparatus according to
If the mounting process is carried out with an apparatus according to
The first correction movement calculated in step E and executed in step N for the bond head 3 and the component gripper 11 also shifts the position of the reference mark(s) 13. This shift of the reference mark(s) 13 is deducted in step R, because the first correction movement has nothing to do with the orientation with respect to the substrate position.
The further correction movement for the bond head 3 and the component gripper 11 comprises components Δuw, Δvw, which are given in machine coordinates of the second drive system 8, and a component Δθw, which is an angular change in machine coordinates of the drive 14 or the rotary drive 15.
The optional steps P to U serve to check whether the bond head 3 has actually reached a position within the required accuracy after executing the correction movements in step N, and if this is not the case, iteratively perform further correction steps until this is the case. The detected deviation must for each component be within the required accuracy.
Step O of the method according to the invention can—especially in the case of an apparatus according to
The substrate camera or substrate cameras 10 (including image evaluation) and the second drive system 8, if necessary together with the drive 14 or the rotary drive 15, form a closed loop axis of motion.
The placement of the substrate marks 23 on the substrates 2 is left to the users of the mounting apparatus of the invention. A mounting apparatus with a single substrate camera 10 requires a different arrangement of the reference mark(s) 13 on the bond head 3 or component gripper 11 and the substrate mark(s) 23 on the substrate 2. Since the components 1 are usually rectangular, the component mark(s) 22, the reference mark(s) 13 and the substrate mark(s) 23 are often arranged in two diagonally opposite corners of the rectangle or in two adjacent corners of the rectangle, as this achieves the highest accuracy.
In the embodiment shown in
The term “component camera” is to be understood functionally, i.e. an optical deflection system can form a component camera together with the substrate camera, as described in the published patent application US 20170092613 (A), which is incorporated by reference into this application. In such a case, a (single) camera and a first optical deflection system form together a first image detection system which makes it possible to take an image of the substrate location on which the component is to be mounted, and the camera, the first optical deflection system and a second optical deflection system form together a second image detection system which makes it possible to take an image of the underside of the component held by the bond head. The first image detection system corresponds to the substrate camera and the second image detection system corresponds to the component camera. The first optical deflection system may under certain circumstances also be omitted.
While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0575/17 | Apr 2017 | CH | national |
