Machining Station and Method For Controlling or Identifying Platelike Workpieces

Abstract

The present disclosure relates to a machining station for machining platelike workpieces (1) by means of at least one tool, in particular a drilling station for machining at least one circuit board, as well as to a method for controlling or identifying a platelike workpiece (1). The machining station has at least one X-ray radiation source (3), at least one detector (4) and a table (2) that can be positioned between the X-ray radiation source (3) and the detector (4), on which the workpiece (1) to be machined can be fastened. The table (2) has a receiving plate (6) made out of a material permeable to X-rays (5), in particular a plastic. The receiving plate (6) has at least one suction port (11) for extracting air and a distribution grid, which is connected in terms of flow with the at least one suction port (11) and consists of several channels (10) unilaterally open in a support surface (9) with beveled and/or rounded edges (13) and/or of inclinedly running through openings (14).

Claims

1. A machining station for machining platelike workpieces (1) by means of at least one tool, in particular a drilling station for machining at least one circuit board, with at least one X-ray radiation source (3), at least one detector (4) and a table (2) that can be positioned between the X-ray radiation source (3) and the detector (4), on which the workpiece (1) to be machined can be fastened, characterized in that the table (2) has a receiving plate (6) made out of a material permeable to X-rays (5), in particular a plastic, and that the receiving plate (6) has at least one suction port (11) for extracting air and a distribution grid, which is connected in terms of flow with the at least one suction port (11) and consists of several channels (10) unilaterally open in a support surface (9) with beveled and/or rounded edges (13) and/or of inclinedly running through openings (14).

2. The machining station according to claim 1, characterized in that the distribution grid defines cuboid support elements (12) with beveled and/or rounded edges (13) between the channels (10).

3. The machining station according to claim 1, characterized in that the channels (10) have a depth of about 3 mm to about 10 mm, in particular of about 5 mm.

4. The machining station according to claim 1, characterized in that the receiving plate (6) has a carrier frame (8), which surrounds the support surface (9) provided with the distribution grid.

5. The machining station according to claim 1, characterized in that the table (2) additionally has a cover plate (7) that can be fastened to the receiving plate (6), wherein the cover plate (7) is provided with a plurality of through openings (14), which are connected in terms of flow with the distribution grid.

6. The machining station according to claim 5, characterized in that the through openings (14) run inclined relative to the cover plate (7) by between 20° and 70°, for example by about 45°.

7. The machining station according to claim 5, characterized in that the receiving plate (6) is sealed relative to the cover plate (7) by means of at least one sealing cord (15).

8. The machining station according to claim 1, characterized in that the table (2) has openings that can be closed by movable bushings.

9. The machining station according to claim 1, which further has an evaluation device that has an image converter and/or an image processing device, and is connected with the detector (4).

10. The machining station according to claim 1, which further has a data processing device for registering a workpiece as a function of signals received by the detector (4).

11. A method for controlling or identifying platelike workpieces (1), such as circuit boards, with the following steps: a) placing a workpiece (1) on a receiving plate (6) or cover plate (7) of a table (2) made out of a material permeable to X-rays (5), wherein the receiving plate (6) has at least one suction port (11) and a distribution grid that is connected in terms of flow with the at least one suction port (11) and consists of several unilaterally open channels (10) in a support surface (9), wherein edges (13) bordering the channels (10) have bevels and/or radii, b) fixing the workpiece (1) on the table (2) by aspirating air out of the suction port (11) and the distribution grid, c) positioning the table (2) with the workpiece (1) between at least one X-ray radiation source (3) and at least one detector (4), d) generating X-rays (5) by the at least one X-ray radiation source (3) and detecting the X-rays (5) that were not absorbed by the table (2) and the workpiece (1) by the detector (4), e) evaluating signals of the detector (4) in a data processing device for controlling or identifying the workpiece (1).

12. The method according to claim 11, characterized in that steps d) and e) take place before machining the workpiece (1) by at least one tool.

13. The method according to claim 11, characterized in that steps d) and e) are repeated after machining the workpiece (1).

14. The method according to claim 11, characterized in that steps d) and e) are taken as the basis for workpiece (1) registration, which is used for identifying the workpiece (1) for machining by at least one tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a side view of a basic representation of the digital X-ray;

[0028] FIG. 2 is a top view of a receiving plate according to an embodiment of the disclosure;

[0029] FIG. 3 is a magnified detail from FIG. 2;

[0030] FIG. 4 is a perspective view of the components of a table according to an embodiment of the disclosure;

[0031] FIG. 5 is a magnified sectional view of the cover plate of the table from FIG. 4; and

[0032] FIG. 6 is a cutout of an X-ray image of the table according to the disclosure.

DETAILED DESCRIPTION

[0033] FIG. 1 schematically depicts the basic principle underlying nondestructive material testing via digital X-rays. To this end, a workpiece 1 is positioned on a table 2 between an X-ray radiation source 3 and a detector 4, so that the X-rays 5 can penetrate through the workpiece 1 and the table 2. The X-rays 5 are partially absorbed both by the workpiece 1 and the table 2. Differences within the workpiece 1, for example various materials or cavities, result in a varying absorption of X-rays 5, and can thus be discerned by means of the detector as brighter or darker structures.

[0034] As evident from the illustration on FIG. 1, the table 2 should allow for as uniform an absorption of X-rays 5 as possible to precisely inspect the workpiece 1. Strong differences in the density and/or thickness of the material of the table 2 would manifest themselves on the X-ray image as dark to bright structures, which would be superposed with correspondingly brighter or darker structures based on the absorption within the workpiece 1.

[0035] In an embodiment of the disclosure, the table 2 has a two-part structure, specifically having a receiving plate 6 and a cover plate 7, which can be joined together tightly as denoted on FIG. 4. FIG. 2 shows a top view of the receiving plate 6. The receiving plate 6 here has an essentially closed outer frame 8 as well as a support surface 9, which is enclosed by the frame 8. The support surface 9 has a plurality of channels 10, which are arranged parallel and perpendicular to each other in a vacuum distribution grid. The channels 10 are connected in terms of flow with suction ports 11, so that air can be aspirated via the channels 10 and suction ports 11.

[0036] As evident from the magnified illustration on FIG. 3, the channels 10 are designed as grooved depressions, which are unilaterally open toward the support surface 9. The material thickness of the receiving plate 6 is thus reduced by the channels 10, wherein cuboid elements 12 (cubes) are formed between the channels 10 in the embodiment shown. However, the edges 13 of these cuboid elements 12 are not rectangular, but rather beveled or rounded or broken. The cuboid elements 12 hence have no sharp edges, but a bevel, so that no transition visible in the X-ray image is generated at the edges 13. For example, the channels 10 around the cuboid elements 12 are about 5 mm deep, so that even though contrasts are generated in the image converter by the differences in material thickness, they are not sharply imaged due to the bevel at the respective edge 13, and image processing is not disrupted. This enables an error-free edge detection of the workpiece 1.

[0037] Cutouts of the cover plate 7 are shown on FIG. 5 in cross section. As evident from this view, the cover plate 7 has a plurality of through openings 14, which connect the channels 10 of the receiving plate 6 with the environment (top of FIG. 5). The cross section of the through openings 14 is here distinctly smaller than the width of the channels 10, so that the through openings 14 serve as small nozzles or vacuum bores, which aspirate air in the channels 10. For sealing purposes, sealing cords 15 can be provided between the receiving plate 6 and the cover plate 7.

[0038] In the embodiment shown, the special feature of the cover plate 7 involves the alignment of vacuum bores. These through openings 14 of the cover plate are not perpendicular, but fabricated at 45°. A perpendicular bore or opening produces a difference in material thickness, which in turn generates a contrast in the image converter in the shape of a circle. For example, this would be disruptive given a circle detection, which for the analysis of a circuit board frequently also takes place based on circular fiduciary markers. By contrast, the inclined openings 14 reduce the difference in material thickness, and change the contrast shape that arises in the image converter.

[0039] The resultant X-ray image is not shaped like a circle, but rather like a brighter oblong hole 16 on FIG. 6. The oblong hole-shaped X-ray image of the vacuum bore does not disrupt image processing. As also evident on FIG. 6, the transition 17 between a channel 10 and a cuboid element 12 does not stand out sharply in the X-ray image owing to the beveled edges 13.

[0040] As a consequence, the table 2 designed according to the disclosure as exemplarily shown makes it possible to nondestructively inspect a workpiece 1, for example a circuit board by means of X-rays 5, and precisely detect copper pads or cavities in the process. At the same time, the configuration of the table 2 allows the workpiece 1 to be quickly and securely fixed on the table 2 by means of a vacuum. This fixation is so strong that the workpiece 1 can also be machined while fastened to the table 2 by means of vacuum, for example by introducing bores.

[0041] The workpiece 1 can here be inspected by means of X-rays 5 not just to control the workpiece 1 before and/or after machining, but can also be used to identify and register a workpiece 1. Based on previously known information about the inner composition of a workpiece 1, for example the number and position of cavities or material differences, a workpiece can in this way be identified and registered for subsequent machining steps through inspection by means of X-rays 5.

[0042] Deviating from the illustration on FIG. 1, in which a workpiece 1 to be machined is arranged directly on the table 2, a so-called backup element can be provided between the table 2 and the workpiece 1, into which a drill can penetrate while machining the workpiece 1 without damaging the table 2. It has here proven to be especially advantageous for the backup element to be permeable to air, e.g., as a diffuse layer of pressed wood, so that exposing the table 2 to vacuum suction fixes the backup element, and the latter the workpiece, on the table.