Method for calibrating position between die bond camera and die bond head

Abstract

The invention relates to the field of die bonding equipment, and provides a method for calibrating the position between a die bonding camera and a die bonding head, which comprises the following steps: placing a reflector in a die bonding area, moving the suction nozzle center of the die bonding head to the view center of the die bonding camera, and carrying out Mark identification; a die bonding head moves in a coordinate system planned in a die bonding calibration area in a dot matrix mode, the coordinate position # imgabs0 # of the die bonding head and the camera coordinate # imgabs1 # are recorded, the coordinate position # imgabs2 # of the die bonding head and the camera coordinate # imgabs3 # are subjected to affine transformation solving, an affine transformation matrix # imgabs4 # is obtained, the virtual coordinate # imgabs5 # of the die bonding head is obtained, and then an error table GridE of the coordinate position # imgabs6 # and the virtual coordinate # imgabs7 # of the die bonding head is obtained; a target position pixel coordinate PW is guided and given by the die bonding camera, a target virtual coordinate PA is obtained through reflection transformation, an error v is calculated according to bilinear interpolation of an error table GridE, and an actual target position PB of the die bonding head is obtained; according to the invention, the position is calibrated by using the affine transformation and bilinear interpolation mode, and the die bonding precision is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of crystal bonding equipment, and in particular to a position calibration method between a crystal bonding camera and a crystal bonding head. Background Art

[0002] In the die bonding equipment, in order to improve the production efficiency of the equipment, the XY movement of the die bonding head and the Y movement of the camera on the die bonding (the die bonding camera only moves in the Y direction) are independent of each other, so it is often necessary to calibrate the positional relationship of the two coordinate systems in the die bonding area to convert between coordinates. The existing method is to first calibrate the pixels of the camera on the die bonding area, and then align the center of the camera field of view with the center of the die bonding head at three or more positions of the die bonding position, and then transform the reference coordinates of the pixel coordinates of the camera field of view and the XY coordinates of the die bonding head by linear interpolation. Although this method is fast, it does not take into account the mechanical errors of the XY motion platform of the die bonding head and the Y motion platform of the camera on the die bonding and the positional relationship between the two coordinate systems, and cannot be used for high-precision die bonding operations. Summary of the invention

[0003] The problem solved by the present invention is how to provide a method for position calibration which utilizes a crystal bonding head XY to perform matrix point movement in a crystal bonding area, captures the position through a crystal bonding camera, and calibrates the coordinates of the crystal bonding head and the pixel coordinates of the crystal bonding camera through affine transformation and bilinear interpolation, thereby effectively improving the accuracy of crystal bonding.

[0004] In order to solve the above problems, the present invention provides a position calibration method between a die bonding camera and a die bonding head, comprising: placing a reflector in a die bonding area, adjusting the intensity of the camera light source, moving the nozzle center of the die bonding head to the field of view center of the die bonding camera, and performing mark recognition on the nozzle center;

[0005] A coordinate system dot matrix consisting of N rows and M columns is planned in the calibration area of ​​the die bonding. The die bonding head moves in the coordinate system dot matrix and the coordinate position of the die bonding head is recorded for each movement. And the camera coordinates of the Mark at the center of the nozzle captured by the solid crystal camera

[0006] The coordinate position of the die bonding head generated by each movement of the die bonding head and the camera coordinates Solve the affine transformation and find the affine transformation matrix Get the conversion relationship between coordinates;

[0007] According to the camera coordinates of the Mark at the center of the nozzle and the affine transformation matrix Obtain the virtual coordinates of the die bonding head Then find the coordinate position of the die bonding head With virtual coordinates Error table Grid E ;

[0008] A target position pixel coordinate P is given by the solid crystal camera. W , the target virtual coordinates P are obtained through reflection transformation A , and then according to the error table Grid E The bilinear interpolation calculation error v is used to obtain the actual target position P of the die bonding head. B .

[0009] Furthermore, the row and column spacing of the coordinate system dot matrix consisting of N rows and M columns is 0.5 mm.

[0010] Furthermore, the coordinate position of the bonding head generated by each movement of the bonding head and the camera coordinates Solve the affine transformation and find the affine transformation matrix include:

[0011] XY coordinates of the die bonding head at each point Perform calculations and records to form a grid of the solid crystal head coordinate system B (N*M), the position of the light spot of the die bonding head for each movement Identify and record to form a world coordinate grid guided by a solid crystal camera W (N*M);

[0012] According to the dot grid of the solid crystal head coordinate system B (N*M) and world coordinate grid W (N*M), calculate the affine transformation matrix

[0013] Furthermore, the lattice grid of the solid crystal head coordinate system B (N*M) and world coordinate grid W (N*M), calculate the affine transformation matrix include:

[0014] Grid of the solid crystal head coordinate system B Each set of bonding head coordinate positions in (N*M) And the corresponding world coordinate grid W Camera coordinates in (N*M) Establish the following relationship:

[0015]

[0016] After integration, we get:

[0017]

[0018] The typical thread least squares form is formed, that is, B = Ax; by x = (A T A) -1 A T B, find the Grid B (N*M) and Grid W (N*M) to get the affine transformation matrix in:

[0019]

[0020] Furthermore, the camera coordinates of the Mark at the center of the nozzle and the affine transformation matrix Obtain the virtual coordinates of the die bonding head In the virtual coordinate The expression is:

[0021]

[0022] Furthermore, the coordinate position of the bonding head is obtained With virtual coordinates Error table Grid E In the error table Grid E The expression is:

[0023]

[0024] Furthermore, the solid crystal camera guides a target position pixel coordinate P W , the target virtual coordinates P are obtained through reflection transformation A , and then according to the error table Grid E The bilinear interpolation calculation error v is used to obtain the actual target position P of the die bonding head. B ,include:

[0025] Given the target position pixel coordinates P W =(ξ,η);

[0026] Obtain the target virtual coordinates P through reflection transformation A , the expression is

[0027] According to the error table Grid E The bilinear interpolation error v is calculated, where the error v = (Δx, Δy);

[0028] Get the actual target position P B , the expression is:

[0029] Furthermore, the error table Grid E , get the pixel coordinates of the target position P W The four adjacent points and the corresponding error v are:

[0030]

[0031] According to bilinear interpolation, we get:

[0032]

[0033] in:

[0034]

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The position calibration method of the present invention fully considers the mechanical errors of the verticality and straightness of the crystal bonding head movement and the positional relationship (rotation, scale) between the two coordinate systems. On the basis of establishing the linear transformation of verticality, rotation and scale by using affine transformation, an error table is introduced to perform bilinear interpolation fitting on nonlinear errors such as the straightness of the axis itself, thereby further improving the crystal bonding accuracy of the crystal bonding machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the overall process of an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of the position structure of a die bonding camera and a die bonding head according to an embodiment of the present invention;

[0039] Figure 3 It is a schematic diagram of the principle structure of the dot matrix of the coordinate system of the die bonding head according to an embodiment of the present invention;

[0040] Figure 4 It is a schematic diagram of the principle structure of the world coordinate lattice guided by the die bonding camera according to an embodiment of the present invention;

[0041] Figure 5 It is a linear schematic diagram of the mechanical error between the two axis systems of the die bonding head and the die bonding camera according to an embodiment of the present invention;

[0042] Figure 6 A schematic diagram of a nonlinear mechanical error between a die bonding head and a die bonding camera according to an embodiment of the present invention;

[0043] Figure 7 Schematic diagram of the principle structure of bilinear interpolation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] In the description of this specification, the description with reference to the terms "embodiment", "one embodiment" and "one implementation" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or implementation are included in at least one embodiment or implementation of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or implementation. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or implementations in a suitable manner.

[0047] like Figure 1 As shown, the present invention provides a position calibration method between a die bonding camera and a die bonding head, comprising: placing a reflector in a die bonding area, adjusting the intensity of the camera light source, moving the nozzle center of the die bonding head to the field of view center of the die bonding camera, and performing mark recognition on the nozzle center;

[0048] A coordinate system dot matrix consisting of N rows and M columns is planned in the calibration area of ​​the die bonding. The die bonding head moves in the coordinate system dot matrix and the coordinate position of the die bonding head is recorded for each movement. And the camera coordinates of the Mark at the center of the nozzle captured by the solid crystal camera

[0049] The coordinate position of the die bonding head generated by each movement of the die bonding head and the camera coordinates Solve the affine transformation and find the affine transformation matrix Get the conversion relationship between coordinates;

[0050] According to the camera coordinates of the Mark at the center of the nozzle and the affine transformation matrix Obtain the virtual coordinates of the die bonding head Then find the coordinate position of the die bonding head With virtual coordinates Error table Grid E ;

[0051] A target position pixel coordinate P is given by the solid crystal camera. W , the target virtual coordinates P are obtained through reflection transformation A , and then according to the error table Grid E The bilinear interpolation calculation error v is used to obtain the actual target position P of the die bonding head. B .

[0052] Specific:

[0053] S1: As attached Figure 2 As shown in the figure, a flat reflective lens is placed in the die bonding area, so that the light emitted by the die bonding camera's light source can be reflected by the reflective lens through the long through hole on the die bonding head that is perpendicular to the reflective mirror surface, forming a circular light spot with clear edges in the field of view of the die bonding camera. Then, by moving the XY coordinates of the die bonding head, the light spot is aligned with the center of the field of view of the die bonding camera, and the light spot is subjected to mark learning and recognition.

[0054] S2: As attached Figure 3 As shown in the figure, the bonding area is planned to consist of N rows and M columns, with a spacing of 0.5mm for the XY motion of the bonding head. Perform calculations and records to form a grid of the solid crystal head coordinate system B (N*M), as attached Figure 4 As shown. The position of the light spot of the die bonding head for each movement Identify and record to form a world coordinate grid guided by a solid crystal camera W (N*M).

[0055] S3: For the mechanical errors of perpendicularity, rotation between axes and scale ratio, see the attached Figure 5 As shown, it can be converted through a linear relationship, that is, we can use affine transformation to express the relationship between the verticality, rotation and scale ratio between the two axis systems. The dot matrix Grid obtained by step S2 B (N*M) and Grid W (N*M), we can calculate the transformation matrix R of the affine transformation.

[0056]

[0057] By Grid B (N*M) and Grid W Each group in (N*M) The following relationships can be established:

[0058]

[0059] Integration and expansion can be obtained:

[0060]

[0061] It becomes the form of the typical thread least squares, B = Ax, which can be expressed by x = (A T A) -1 A T B, find the Grid B (N*M) and Grid W (N*M) to get the affine transformation matrix

[0062] S4: Since the axis itself has mechanical straightness error, and the straightness error is nonlinear, as shown in the attached Figure 6 Therefore, we use the affine transformation matrix Calculated

[0063] The actual movement position of the die bonding head There are errors, such as Figure 6 The straightness error table is Grid E , record each original data and the error v after affine transformation ij ,Right now

[0064]

[0065] S5: Straightness error can be solved by bilinear interpolation method, as shown in the attached Figure 7 As shown, given a target position P W =(ξ,η), find the actual P B =(x,y),

[0066]

[0067] The error v = (Δx, Δy), which is given by the error table Grid E , get 4 adjacent points and the corresponding error v:

[0068]

[0069] Bilinear interpolation gives:

[0070]

[0071] Among them:

[0072]

[0073] Finally, the actual position is obtained.

[0074] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for calibrating the position between a die bonding camera and a die bonding head, characterized in that: include: Place the reflector in the die bonding area, adjust the intensity of the camera light source, move the nozzle center of the die bonding head to the center of the field of view of the die bonding camera, and perform mark recognition on the nozzle center; A coordinate system dot matrix consisting of N rows and M columns is planned in the calibration area of ​​the die bonding. The die bonding head moves in the coordinate system dot matrix and the coordinate position of the die bonding head is recorded for each movement. And the camera coordinates of the Mark at the center of the nozzle captured by the solid crystal camera The coordinate position of the die bonding head generated by each movement of the die bonding head and the camera coordinates Solve the affine transformation and find the affine transformation matrix Get the conversion relationship between coordinates; According to the camera coordinates of the Mark at the center of the nozzle and the affine transformation matrix Obtain the virtual coordinates of the die bonding head Then find the coordinate position of the solid crystal head With virtual coordinates Error table Grid E ; A target position pixel coordinate P is given by the solid crystal camera W , the target virtual coordinates P are obtained through reflection transformation A , and then according to the error table Grid E The bilinear interpolation calculation error v is used to obtain the actual target position P of the die bonding head. B .

2. The position calibration method between the die bonding camera and the die bonding head according to claim 1, characterized in that: The row and column spacing of the coordinate system dot matrix consisting of N rows and M columns is 0.5 mm.

3. The position calibration method between the die bonding camera and the die bonding head according to claim 1, characterized in that: The coordinate position of the bonding head generated by each movement of the bonding head and the camera coordinates Solve the affine transformation and find the affine transformation matrix include: The coordinate position of the die bonding head at each point Perform calculations and records to form a grid of the solid crystal head coordinate system B (N*M), the position of the light spot of the die bonding head for each movement Identify and record to form a world coordinate grid guided by the solid crystal camera W (N*M); According to the dot grid of the solid crystal head coordinate system B (N*M) and world coordinate grid W (N*M), calculate the affine transformation matrix 4. The position calibration method between the die bonding camera and the die bonding head according to claim 3, characterized in that: According to the solid crystal head coordinate system grid B (N*M) and world coordinate grid W (N*M), calculate the affine transformation matrix include: Grid of the solid crystal head coordinate system B Each set of bonding head coordinate positions in (N*M) And the corresponding world coordinate grid W Camera coordinates in (N*M) Establish the following relationship: After integration, we get: The typical thread least squares form is formed, that is, B = Ax; by x = (A T A) -1 A T B, find the Grid B (N*M) and Grid W (N*M) to get the affine transformation matrix in:

5. The position calibration method between the die bonding camera and the die bonding head according to claim 1, characterized in that: The camera coordinates of the Mark at the center of the nozzle and the affine transformation matrix Obtain the virtual coordinates of the die bonding head In the virtual coordinate The expression is:

6. The position calibration method between the die bonding camera and the die bonding head according to claim 5, characterized in that: Then the coordinate position of the solid crystal head is obtained With virtual coordinates Error table Grid E In the error table Grid E The expression is:

7. The position calibration method between the die bonding camera and the die bonding head according to claim 6, characterized in that: The solid crystal camera guides a target position pixel coordinate P W , the target virtual coordinates P are obtained through reflection transformation A , and then according to the error table Grid E The bilinear interpolation calculation error v is used to obtain the actual target position P of the die bonding head. B ,include: Given the target position pixel coordinates P W =(ξ,η); Obtain the target virtual coordinates P through reflection transformation A , the expression is According to the error table Grid E The bilinear interpolation error v is calculated, where the error v = (Δx, Δy); Get the actual target position P B , the expression is:

8. The method for calibrating the position between the die bonding camera and the die bonding head according to claim 7, characterized in that: According to the error table Grid E The bilinear interpolation calculation error v includes: From the error table Grid E , get the pixel coordinates of the target position P W The coordinates of the four adjacent points and the corresponding error v, namely: According to bilinear interpolation, we get: in:

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