CN115509090A - A Method of Quickly Detecting the State of LDI Equipment - Google Patents

Abstract

The invention discloses a method for rapidly detecting the state of LDI equipment, and belongs to the technical field of PCB exposure. Exposing a detection graph containing M rows by N columns of matrix points by a self-contained tool of software, testing the comparison between the position of the exposure point and the theoretical position by using an alignment camera, automatically analyzing test data, detecting whether equipment has problems, quickly positioning problem points, such as whether a light path has problems, and whether a positioning precision, horizontal straightness, YAW and the like of a workpiece table have problems, and saving the time for stopping inspection; further, by setting the matrix points to be solid circles or circular rings, the detection of the graph correctness and the graph alignment result is respectively realized.

Description

A Method of Quickly Detecting the State of LDI Equipment

technical field

The invention relates to a method for quickly detecting the state of LDI equipment, belonging to the technical field of PCB board exposure.

Background technique

Laser direct writing exposure equipment LDI (laser direct imaging) is a device that can directly transmit the exposure data of the PCB board to a dedicated graphics processing software, and the graphics processing software processes the graphics and then sends them to the LDI exposure software through DMD. An exposure system composed of a digital micromirror array, a laser and an optical path, and then a device that directly transfers graphics on a plate.

LDI equipment is mainly composed of a high-precision motion platform, an exposure system, and an alignment system. The high-precision motion platform includes a carrying platform and control equipment for controlling the precise movement of the carrying platform. The exposure system also includes DMD digital micromirror arrays, multiple light sources and their corresponding optical path systems, etc.; the alignment system includes alignment cameras, etc. The exposure principle is that multiple light sources cooperate with digital micromirror DMD to realize graphic exposure (subsequently referred to as exposure system), so there are multiple light sources to form splicing of light spots, and the exposure system can be moving or fixed. The high-precision motion platform is fixed with a carrying platform (suction cup) for placing products, and the scanning exposure is realized through the movement of the carrying platform, and the exposure can be scanned once or multiple times.

Because the temperature and humidity of the environment where the exposure process of the LDI equipment is unstable, or some sudden problems occur, such as collision with the lens, camera, board jam, etc., will lead to changes in the hardware position or parameters of the equipment, which will directly affect the quality of the product. For example, there are layer deviation problems, splicing problems, etc., and because of the complexity of its own structure, it is difficult to judge where the problem occurs when layer deviation problems or splicing problems occur during the exposure process, especially the layer deviation problem, although often It is caused by the abnormality of the high-precision motion platform, but there are many parameters of the high-precision motion platform, such as YAW, horizontal straightness, positioning accuracy, etc. If there is a problem of layer deviation during production, the equipment needs to be shut down. Use a calibration board or The interferometer is used to measure and troubleshoot the cause and then make adjustments to avoid more defective parts in the future (considering the high price of calibration plates or interferometers, usually not equipped with every exposure equipment), this process takes a long time, Professional personnel are also required, and long downtime will naturally affect output; thus time-consuming and labor-intensive, and severe production reduction will lead to increased costs for manufacturers.

As for the splicing problem, in the existing methods, equipment is usually used to expose, splice and analyze graphics, and then use a line width measuring instrument to measure the splicing data, and the line width measuring instrument also has the problem of high cost. The workpiece table detection is calibrated with an interferometer or a calibration plate, so there are also problems of long detection time and high cost.

Contents of the invention

In order to be able to solve the above problems, the present invention provides a method for quickly detecting the state of an LDI device, the method comprising:

Exposing a preset detection pattern by using an LDI device, the preset detection pattern includes matrix points of M rows*N columns;

Use the alignment camera of the LDI equipment to collect the actual coordinate values of each matrix point on the graph after exposure;

According to the difference between the actual coordinate value of each matrix point and the theoretical value, it is determined whether each component of the LDI equipment is in a normal state.

Optionally, determining whether each component of the LDI device is in a normal state according to the difference between the actual coordinate value of each matrix point and the theoretical value includes:

Obtain the abscissa difference Δx and ordinate difference Δy between the actual coordinate value and the theoretical value of each matrix point respectively;

If the abscissa difference Δx ≥ 5 μm of the matrix points in the same row, it is judged that the positional relationship of each DMD in the LDI device is in an abnormal state;

If the abscissa difference Δx of the matrix points in the same column is ≥ 10 μm, it is judged that the Y-axis horizontal straightness of the high-precision motion platform in the LDI equipment is in an abnormal state;

If the ordinate difference Δy of the matrix points in the same column is ≥ 15 μm, it is judged that the positioning accuracy of the Y-axis of the high-precision motion platform in the LDI equipment is in an abnormal state;

If the ordinate difference Δy of the matrix points in the same row is ≥ 5 μm, it is judged that the splicing debugging state in the LDI device is in an abnormal state.

Optionally, the method also includes:

The state of the platform YAW is judged by detecting the curve difference of the vertical coordinates Y1~Yn of the multi-row matrix points on the graph.

Optionally, the method includes:

If the difference between the curves of the vertical coordinates Y1-Yn of the multi-row matrix points on the detection graph exceeds 10 μm, it is judged that the state of the platform YAW is abnormal.

Optionally, the matrix points are solid circles or circular rings.

Optionally, when the method is used to check the correctness of the exposure pattern, solid circles are used for the matrix points.

Optionally, when the method is used to detect the alignment result of the exposure pattern, the matrix points use circles.

The beneficial effects of the present invention are:

Use the software's own tool to expose a detection pattern containing matrix points of M rows*N columns, use the alignment camera to test the position of the exposure point and compare it with the theoretical position, and automatically analyze the test data to detect whether there is a problem with the equipment , to quickly locate problem points, such as whether there is a problem with the optical path, whether there is a problem with the positioning accuracy of the workpiece table, whether there is a problem with horizontal straightness, YAW, etc., to save the time for shutdown inspection; further, by setting the matrix points as solid circles or rings, respectively Realize the detection of the correctness of the graphics and the results of the graphics alignment.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

Fig. 1 is a schematic diagram of a detection pattern adopted in an embodiment of the present invention;

Fig. 2 is the schematic diagram of the ring in the detection figure that adopts in one embodiment of the present invention;

Fig. 3A is a schematic diagram showing a large difference in the curves of the multi-row matrix point ordinates Y1-Yn on the detection pattern disclosed in one embodiment of the present invention;

Fig. 3B is a schematic diagram showing a small difference in the curves of the multi-row matrix point ordinates Y1-Yn on the detection pattern disclosed in one embodiment of the present invention;

Fig. 4A is a schematic diagram of the state of the graphics cast by the DMD before the splicing and debugging of the LDI device disclosed in one embodiment of the present invention;

Fig. 4B is a schematic diagram of the state of the graphics cast by the DMD after the splicing and debugging of the LDI device disclosed in one embodiment of the present invention;

Fig. 5A is a schematic diagram of the graph exposed if the Y-axis normally moves along a straight line in the motion mode of the LDI device disclosed in one embodiment of the present invention;

Fig. 5B is a schematic diagram of the graph exposed if the Y-axis does not move along a straight line in the motion mode of the LDI device disclosed in one embodiment of the present invention;

Figure 6 is a schematic diagram of the graphic exposed by the unqualified splicing and debugging of the LDI equipment;

Fig. 7A is a schematic diagram of the normal exposure of the YAW value in the motion mode of the LDI device;

FIG. 7B is a schematic diagram of the graph exposed when the YAW value is abnormal in the motion mode of the LDI device.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

In order to facilitate the understanding of the technical solution of this application, some technical terms involved in this application are explained as follows:

Calibration board, that is, a flat plate with a fixed-pitch pattern array; in order to correct the lens distortion, it is necessary to determine the conversion relationship between the physical size and the pixel; and determine the three-dimensional geometric position of a point on the surface of the space object and its corresponding point in the image. The interrelationship among them, the geometric model of the camera can be obtained by shooting the calibration plate with the camera and calculating the calibration algorithm, so as to obtain high-precision measurement and reconstruction results.

Stitching: Refers to the connections between adjacent strips during scanning.

Splicing dislocation: In this application, it refers specifically to the gap in the Y direction at the connection between different scanning strips during DMD scanning.

Splice coincidence: refers to the abnormality in the X direction at the splice, where the two strips overlap together.

Splicing tear: refers to the abnormality in the X direction of the splicing, and there is a distance between the two strips.

Inner layer alignment: After laminating the film on the diazo film, use the mark to mark the target point on the A side and expose the pattern. When exposing the B side, grab the 2 alignment targets lit by the Smark on the B side and expose it. At this time The deviation of the images on both sides is the inner layer alignment.

Outer layer alignment: During exposure, the two layers of the printed circuit board use the same alignment target hole, generally 4-point alignment. At this time, the deviation value of the exposure image of the two layers is the outer layer alignment.

High-precision motion platform Stage: In this system, it generally refers to an electronically controlled translation stage, which is used for moving and exposing the substrate. It is usually square, with two axes, which can realize X-axis forward and backward, and Y-axis forward and backward;

Orthogonality: the orthogonality of the X&Y axis of the workpiece table;

YAW: The yaw angle of the Y-axis of the workpiece table during the linear motion.

Positioning accuracy: From the reference point (end point), the positioning is carried out sequentially in one direction at a certain interval, and the measured value of each positioning point (the actual position moved from the reference point) and the command value (after the command is issued) are measured within the movement range of the workbench. The difference between the positions that should actually move) and the maximum difference is taken as the cumulative error (positioning accuracy).

Horizontal straightness: Positioning in one direction from the reference position, measure the difference between the vertical and horizontal offsets and the reference position, and connect the starting point and end point of the measured value to get a straight line. The maximum difference in offset from the straight line was regarded as the straightness. Straightness has a vertical component and a horizontal component. Take the maximum value of each component as the straightness of the platform.

Embodiment one:

This embodiment provides a method for quickly detecting the state of an LDI device. The method controls the exposure system through the exposure software to expose a detection pattern on a PCB with a dry film. The detection pattern includes M rows* as shown in Figure 1 N-column matrix points; the matrix points use solid circles or rings, which are used to detect different items. For example, when testing the correctness of exposure graphics, the matrix points use solid circles to compare the actual exposure graphics with the original image. The smaller the difference, the better the correctness of the graph; when detecting the alignment result of the exposure graph, the matrix point uses a ring, the solid circle is used as the upper layer, and the ring is used as the exposure layer to detect the gap between the solid circle and the ring. The deviation value of the center of the circle to confirm the alignment effect. The schematic diagram of the ring is shown in Figure 2.

The size of the graphics and the number of matrix points can be configured according to actual needs, and the exposure layers and alignment types can be controlled. After the parameters are configured, the software tool automatically generates graphics in GDS format, and performs exposure according to the configured exposure conditions.

Use the alignment camera of the LDI equipment to collect the actual coordinates of the matrix points on the map, and use the coordinate comparison method to compare with the coordinates in the original image in GDS format, and analyze the row and column of the obtained data to determine the current equipment status is normal.

According to actual needs, the size of the detection pattern and the number of matrix points can be configured using the small tools included in the exposure software, which can configure various parameters, and can control the exposure system, graphic data database, etc. to achieve graphic generation and exposure, and control the alignment of the camera for data Collect, process and analyze data.

The coordinate comparison method refers to that when the GDS graphics are generated, the coordinates of each matrix point are known (i.e. X theoretical value, Y theoretical value), and after the exposure is completed, the color of the exposed place of the dry film becomes darker, and the same as The surrounding unexposed areas form obvious chromatic aberration, and the contrast is very high. The actual position (X actual value, Y actual value) is calculated by aligning the camera and the existing published image recognition algorithm. The software automatically calculates the difference between the two coordinate positions, and automatically outputs the calculated difference data.

According to the difference between the actual value and the theoretical value after exposure of each matrix point on the detection graph, determine whether each hardware of the LDI device is faulty:

1. Judging the state of the DMD positional relationship by detecting the coordinate difference of the abscissa X1~Xn of each row of matrix points on the graph;

2. Judging the Y-axis horizontal straightness state of the high-precision motion platform by detecting the coordinate difference of the abscissa X1~Xm of each column matrix point on the graph;

3. Judging the positioning accuracy status of the Y-axis of the high-precision motion platform by detecting the coordinate difference of the vertical coordinates Y1~Ym of each column matrix point on the graph;

4. Judging the debugging status of splicing by detecting the coordinate difference of Y1~Yn coordinates of each row of matrix points on the graph;

5. Judging the state of the platform YAW by detecting the difference between the curves of the multi-row matrix point ordinates Y1~Yn on the graph.

Specifically, the abscissa difference Δx and the ordinate difference Δy between the actual coordinate value and the theoretical value of each matrix point are obtained respectively;

If the abscissa difference Δx ≥ 5 μm of the matrix points in the same row, it is judged that the positional relationship of each DMD in the LDI device is in an abnormal state;

If the abscissa difference Δx of the matrix points in the same column is ≥ 10 μm, it is judged that the Y-axis horizontal straightness of the high-precision motion platform in the LDI equipment is in an abnormal state;

If the ordinate difference Δy of the matrix points in the same column is ≥ 15 μm, it is judged that the positioning accuracy of the Y-axis of the high-precision motion platform in the LDI equipment is in an abnormal state;

If the ordinate difference Δy of the matrix points in the same row is ≥ 5 μm, it is judged that the splicing debugging state in the LDI device is in an abnormal state.

Further, the state of the platform YAW is judged by detecting the curve difference of multi-row matrix point ordinate Y1～Yn on the graph; the curve refers to the X&Y orthogonal curve at different positions on the Y axis, if the multi-row matrix point ordinate Y1～Yn If the curve difference exceeds 10 μm, it is judged that the state of the platform YAW is abnormal. Figure 3A and Figure 3B respectively show the situations where the curve difference exceeds 10 μm and does not exceed 10 μm.

The judgment principles are introduced as follows:

1. The exposure system is composed of multiple DMDs and imaging light paths. The light spots of multiple light paths are spliced to form an exposure light path. Whether it is a single scan or multiple scans, there is splicing between the light paths. Figure 4A shows the state of the DMD before splicing and debugging. There is misalignment in the Y direction or tearing and overlapping in the X direction. Figure 4B shows the adjusted splicing state. The overlapping and tearing in the X direction and the misalignment in the Y direction are all controlled within a certain range. within range. Splicing needs to be kept in this qualified state during continuous production. If there is a misalignment in the X and Y directions, it will cause product quality problems.

By exposing dense matrix points, each light source can expose n (n≥1) points to represent the position of the light source. After adjusting the splicing, the distance between the points that can be exposed by adjacent light sources is fixed. Therefore, the exposure system software obtains the coordinates of n points that can be exposed by each light source and compares them with the theoretical values to confirm whether the current DMD position relationship is normal. If the difference between the actual position and the theoretical position exceeds the set threshold, the exposure The system software will give a prompt to check the splicing status.

2. The movement mode of the LDI device during exposure is shown in Figure 5A and Figure 5B. The suction cup on which the PCB board is placed moves along the Y-axis direction, perpendicular to the direction of the light path (fixed or moving) of the exposure, and aligned with the alignment where the camera is located. The axis is also perpendicular to the Y axis. Because the sucker moves linearly along the Y axis during exposure, the X coordinate of the exposed figure should be kept within a certain range, that is, the exposed figure is a rectangle. If the suction cup does not move in a straight line, the exposed figure will be a parallelogram, which is too different from the original picture, which will lead to quality problems such as alignment layer deviation and graphic size mismatch. Therefore, the movement of the platform can be judged from the coordinate difference of the matrix points. If the X1~Xm coordinate difference does not exceed the set threshold, it is considered that the horizontal straightness of the Y axis is in a normal state. If it exceeds the threshold, the software will give a prompt to the professional. Check the status of the platform.

3. The positioning accuracy of the workpiece table is an important guarantee to ensure the correct exposure pattern. Its accuracy is determined by the grating scale of the workpiece table. The temperature and humidity of the working environment will affect the grating scale, resulting in inaccurate positioning accuracy. After exposing the matrix points, you can determine whether the positioning accuracy has changed from the Y coordinates Y1~Ym of each column. If the difference between the actual exposure position and the theoretical position is within the set threshold range, the Y-axis positioning accuracy of the platform is considered normal. If it exceeds Threshold, the exposure system software will give a prompt to check the positioning accuracy of the platform and make compensation according to the test data.

4. There are two directions of X and Y for splicing between multiple optical paths. During exposure, the Y-axis movement direction of the workpiece table is perpendicular to the axis where the exposure optical path is located, and scanning exposure is performed. In order to ensure that the exposed figure is a rectangle, it is necessary to pay attention to the debugging of the stitching Y direction. It is necessary to ensure that the Y coordinates Y1~Yn of each line are not much different, that is, the scanned line is a straight line perpendicular to the Y axis, not an oblique line. If there is an inclination, the exposed graphics will be deformed, as shown in Figure 6. If the difference between the test coordinates Y1～Yn is too large and exceeds the threshold, the exposure system software will give a prompt to check the splicing and re-adjust.

5. YAW is the left and right deflection of the platform during the motion process. This deflection will lead to graphic deformation. The conventional method is to use a laser interferometer or a calibration plate plus a camera to test the YAW situation, but the laser interferometer is very expensive and requires Professional personnel set up and test, can not quickly get the results, and the solution of calibration plate plus camera needs to add a camera and moving axis to the exposure system, the cost is relatively high. Because this yaw will cause the orthogonality of the Y-axis and the X-axis to change, as shown in Figure 7A and Figure 7B, so this feature can be used to reversely determine the state of the YAW through the exposure pattern. If YAW is in a qualified state, there is little difference between the Y coordinates of each row, and if the YAW value exceeds the standard, there is a large difference between the Y coordinates of each row. You can extract the Y coordinate of each row by testing the point coordinates of the full-page matrix, and compare whether the difference between the Y coordinates of each row exceeds the threshold. If it exceeds the set threshold, the exposure system software will give a prompt to determine whether the YAW value of the workpiece table is abnormal , further confirmation or debugging is required.

Part of the steps in the embodiments of the present invention can be realized by software, and the corresponding software program can be stored in a readable storage medium, such as an optical disk or a hard disk.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (7)

1. a method for fast detection of LDI equipment state, is characterized in that, described method comprises: Exposing a preset detection pattern by using an LDI device, the preset detection pattern includes matrix points of M rows*N columns; Use the alignment camera of the LDI equipment to collect the actual coordinate values of each matrix point on the graph after exposure; According to the difference between the actual coordinate value of each matrix point and the theoretical value, it is determined whether each component of the LDI equipment is in a normal state. 2. The method according to claim 1, wherein said determining whether each part of the LDI device is in a normal state according to the difference between the actual coordinate value of each matrix point and the theoretical value comprises: Obtain the abscissa difference Δx and ordinate difference Δy between the actual coordinate value and the theoretical value of each matrix point respectively; If the abscissa difference Δx ≥ 5 μm of the matrix points in the same row, it is judged that the positional relationship of each DMD in the LDI device is in an abnormal state; If the abscissa difference Δx of the matrix points in the same column is ≥ 10 μm, it is judged that the Y-axis horizontal straightness of the high-precision motion platform in the LDI equipment is in an abnormal state; If the ordinate difference Δy of the matrix points in the same column is ≥ 15 μm, it is judged that the positioning accuracy of the Y-axis of the high-precision motion platform in the LDI equipment is in an abnormal state; If the ordinate difference Δy of the matrix points in the same row is ≥ 5 μm, it is judged that the splicing debugging state in the LDI device is in an abnormal state. 3. The method according to claim 2, wherein the method further comprises: The state of the platform YAW is judged by detecting the curve difference of the vertical coordinates Y1~Yn of the multi-row matrix points on the graph. 4. The method according to claim 3, characterized in that the method comprises: If the difference between the curves of the vertical coordinates Y1-Yn of the multi-row matrix points on the detection graph exceeds 10 μm, it is judged that the state of the platform YAW is abnormal. 5. The method according to claim 1, wherein the matrix points are solid circles or rings. 6. The method according to claim 5, characterized in that when the method is used to detect the correctness of the exposure pattern, the matrix points are filled circles. 7. The method according to claim 5, wherein when the method is used to detect the alignment result of the exposure pattern, the matrix points adopt circular rings.

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