Centrifugal barrel polishing method

Abstract

The present invention suppresses wear of a functional layer without covering the functional layer with another member.　Provided is a centrifugal barrel polishing method for chamfering a corner part (24) of a ceramic substrate (21) with respect to a plate-form workpiece (20) in a mode in which a conductor pattern (23) different from the ceramic substrate (21) is provided on the surface of the ceramic substrate (21), wherein, by using a centrifugal barrel polisher (10) in which a barrel tank (12) is rotatably attached at an eccentric position relative to a turret (11), polishing is performed such that the relative centrifugal acceleration F = 4π2N2R / G is set within the range of 15 ≤ F ≤ 25 and the rotation / revolution ratio n / N is set to −0.40 ≤ n / N ≤ −0.15, where N is the revolution speed [rps] of the barrel tank (12), n is the rotation speed [rps] of the barrel tank (12), n / N is the rotation / revolution ratio of the barrel tank (12), R is the radius [m] of the revolution orbit (15) of the barrel tank (12), G is the gravitational acceleration, and F is the relative centrifugal acceleration on the revolution orbit (15) during the planetary rotation of the barrel tank (12).

Description

Centrifugal Barrel Polishing Method

[0001] The present invention relates to a centrifugal barrel polishing method.

[0002] In fields such as electric vehicles and industrial equipment, power modules are used to efficiently control and convert large amounts of electricity. As a component of a power module, there is a printed circuit board (Printed Circuit Board) on which electronic components such as Si semiconductors are mounted on a printed wiring board (Printed Wiring Board). The printed wiring board is formed by printing a metal conductor pattern made of aluminum or copper on a ceramic substrate. In such a printed wiring board, chamfering is performed on the corners of the ceramic substrate by barrel polishing in order to suppress the occurrence of cracks and chips at the corners of the ceramic substrate. Patent Document 1 discloses a technique for performing chamfering on a ceramic sintered body (printed wiring board) having a conductor layer (conductor pattern) formed on its surface, in which barrel polishing is performed on the ceramic sintered body with the conductor layer covered with a ceramic member. According to this method, since the conductor layer is protected by the ceramic member, wear of the conductor layer can be suppressed.

[0003] Japanese Patent Application Laid-Open No. 2009-202260

[0004] In the manufacturing method of the ceramic substrate (printed circuit board) described in Patent Document 1, in addition to the barrel polishing step, a step of covering the conductor layer with a ceramic member and a step of peeling the ceramic member from the ceramic sintered body after barrel polishing are required, so there is a problem that the manufacturing cost is high. Furthermore, in the barrel polishing step, there is a risk that the ceramic member may peel off from the ceramic substrate, or the ceramic substrate may be damaged by collision with the ceramic member of another ceramic substrate. Therefore, it is desired to suppress wear of the conductor layer without covering the conductor layer with a ceramic member.

[0005] The present invention has been completed based on the above circumstances, and in a barrel polishing method for chamfering a substrate having a functional layer formed on its surface, an object is to suppress wear of the functional layer without covering the functional layer with a separate member.

[0006] The present invention relates to a centrifugal barrel polishing method for chamfering the corners of a plate-shaped workpiece having a functional layer of a different nature from the substrate on its surface, using a centrifugal barrel polishing machine in which a barrel tank into which polishing stones and the plate-shaped workpiece are fed is mounted rotatably at an eccentric position of a rotating turret, where N is the rotational speed of the barrel tank [rps], n is the rotational speed of the barrel tank [rps], n / N is the rotational ratio of the barrel tank, R is the radius of the orbit traced by the rotation center of the barrel tank [m], G is the acceleration due to gravity, and F = 4π 2 N 2 This centrifugal barrel polishing method defines R / G as the relative centrifugal acceleration on the orbit during the planetary rotation of the barrel tank, sets the relative centrifugal acceleration F in the range of 15 ≤ F ≤ 25, and sets the revolution-orbit ratio n / N in the range of -0.40 ≤ n / N ≤ -0.15.

[0007] The present invention relates to a barrel polishing method for chamfering a substrate on which a functional layer has been formed, and can suppress wear of the functional layer without covering the functional layer with a separate component.

[0008] Schematic diagram of the centrifugal barrel polishing machine of Example 1 Perspective view of the polishing stone Perspective view of a polishing stone different from the polishing stone in Figure 2 Perspective view of a polishing stone different from Figures 2 and 3 Plan view of the plate-shaped workpiece Front view of the plate-shaped workpiece Schematic plan view showing the plate-shaped workpiece in a well-polished state Front view showing the plate-shaped workpiece in a well-polished state Schematic plan view showing the conductor pattern with little wear Front view showing the conductor pattern with little wear Plan view showing the conductor pattern with moderate wear Front view showing the conductor pattern with moderate wear Plan view showing the conductor pattern with severe wear Front view showing the conductor pattern with severe wear

[0009] First, embodiments of the present disclosure will be listed and described. Any combination of the following embodiments, without causing contradiction, is also included as a form for carrying out the invention. The centrifugal barrel polishing method of the present disclosure is: (1) a centrifugal barrel polishing method for chamfering the corners of a plate-shaped workpiece having a functional layer of a different nature from the substrate on its surface, using a centrifugal barrel polishing machine in which a barrel tank into which polishing stones and the plate-shaped workpiece are fed is rotatably mounted at an eccentric position of a rotating turret. N is the rotational speed of the barrel tank [rps], n is the rotational speed of the barrel tank [rps], n / N is the rotational ratio of the barrel tank, R is the radius of the orbit traced by the rotation center of the barrel tank [m], G is the acceleration due to gravity, F = 4π 2 N 2 R / G is defined as the relative centrifugal acceleration on the orbit during the planetary rotation of the barrel tank. The relative centrifugal acceleration F is set to the range of 15 ≤ F ≤ 25, and the rotation-orbit ratio n / N is set to the range of -0.40 ≤ n / N ≤ -0.15 for polishing.

[0010] This disclosure describes how, in order to suppress surface undulation of the flow in a planetary rotating barrel, the relative centrifugal acceleration F on the orbit of the barrel is set to a range of 15 ≤ F ≤ 25, which is greater than the value when polishing a metal workpiece, and the rotation-orbit ratio n / N of the barrel is set to a range of -0.40 ≤ n / N ≤ -0.15, which is lower than the ratio of n when polishing a metal workpiece. When polishing a plate-shaped workpiece using a centrifugal barrel polishing machine in which the rotation and orbit of the barrel are oriented in opposite directions, reducing surface undulation of the flow of the mass consisting of polishing stones and plate-shaped workpieces in the barrel allows the plate-shaped workpieces in the flow to move in a relatively stable position along the surface of the substrate, rather than in a turbulent movement that randomly changes direction. This movement allows the corners on the leading edge side of the substrate in the direction of movement to be effectively polished by the polishing stones. The polishing stones do not collide head-on with the surface of the substrate but rather make contact by rubbing, thus reducing wear on the functional layer by the polishing stones. Therefore, according to the centrifugal barrel polishing method of this disclosure, wear of the functional layer can be suppressed without covering the functional layer with another component.

[0011] (2) In (1), the plate-shaped workpiece is a printed circuit board in which the substrate is made of ceramics and the functional layer is made of a conductive pattern.

[0012] (3) In (1) or (2), it is preferable to set the relative centrifugal acceleration F in the range of 20 ≤ F ≤ 25. With this configuration, the undulation on the surface of the flow of the mass consisting of abrasive stones and plate-shaped workpieces in the barrel tank is reduced, and thus the wear of the functional layer by the abrasive stones can be further reduced.

[0013] (4) In (1) or (2), it is preferable to set the rotation-orbit ratio n / N to the range of -0.40 ≤ n / N ≤ -0.20. With this configuration, the undulation on the surface of the flow of the mass consisting of abrasive stones and plate-shaped workpieces in the barrel tank is reduced, and thus the wear of the functional layer by the abrasive stones can be further reduced.

[0014] (5) In (1) or (2), it is preferable to use spherical abrasive stones with a diameter of 2 mm or more and 4 mm or less as the abrasive stones to be placed in the barrel tank. With this configuration, good polishing can be performed.

[0015] (6) In (5), it is preferable that the abrasive stone be made of ceramics. This configuration makes it possible to suppress wear of the abrasive stone.

[0016] [Details of Embodiments of the Present Disclosure] [Example 1] Hereinafter, Example 1, which embodies the present invention, will be described with reference to Figures 1 to 14. The centrifugal barrel polishing method of Example 1 is performed by using a centrifugal barrel polishing machine 10. As shown in Figure 1, the centrifugal barrel polishing machine 10 is configured to include one turret 11 and four barrel tanks 12. The turret 11 is circular in shape and is driven to rotate at a predetermined speed in one direction (counterclockwise in Figure 1) around a horizontal orbital axis 13 (center of revolution) by an orbital motor (not shown).

[0017] Each barrel tank 12 has a hexagonal shape with six sides when viewed parallel to its axis of rotation 14 (center of rotation). The four barrel tanks 12 are arranged at equal 90° intervals in the circumferential direction, at positions eccentric to the axis of revolution 13 on the turret 11 (i.e., on the circumference concentric with the axis of revolution 13). Each barrel tank 12 rotates relative to the turret 11 at a predetermined speed around its axis of rotation 14, which is parallel to the axis of revolution 13. The rotational force of the axis of revolution 13 is transmitted to the four barrel tanks 12 via a well-known rotational force transmission mechanism (not shown), and the four barrel tanks 12 are rotationally driven using an orbital motor as the drive source. The barrel tanks 12 may also be rotationally driven using a rotational motor (not shown) provided separately from the orbital motor as the drive source. The rotation direction (direction of rotation) of these four barrel tanks 12 is the opposite of the rotation direction (direction of revolution) of the turret 11, and is clockwise in Figure 1.

[0018] When the orbital motor (or rotational motor) is driven, the turret 11 and the four barrel tanks 12 revolve together around the orbital axis 13, and each barrel tank 12 rotates in the opposite direction to the orbital direction around the rotational axis 14 relative to the turret 11, so that the four barrel tanks 12 rotate in a planetary pattern. The trajectory traced by the rotational axis 14 when the four barrel tanks 12 revolve becomes the orbital trajectory 15. The centrifugal barrel polishing machine 10 is a device that polishes plate-shaped workpieces 20 by loading masses 16 (plate-shaped workpieces 20 and polishing stones 31, 32, 33) into the four planetarily rotating barrel tanks 12 and rotating the barrel tanks 12 in a planetary pattern. Note that only one type of polishing stone 31, 32, or 33 may be loaded into one barrel tank 12, or two or three types of polishing stones 31, 32, or 33 may be loaded.

[0019] As shown in Figures 5 and 6, the plate-shaped workpiece 20 is a printed wiring board (Printed Wiring Board) in which a conductive pattern 23 made of metal such as aluminum or copper is printed onto the mounting surface 22 (surface) of a ceramic substrate 21. The conductive pattern 23 is a functional layer of a different nature, differing in material and function from the ceramic substrate 21. Figures 5 and 6 are schematic diagrams illustrating the structure of the plate-shaped workpiece 20. In Figure 6 (front view), the thickness of the ceramic substrate 21 and the thickness of the conductive pattern 23 are exaggerated. In Figure 5 (top view), the shape of the conductive pattern 23 is simplified. In Figures 7 to 14, which show the state of the plate-shaped workpiece 20 after polishing under the polishing conditions B-0 to B-6 and F-1 to F-5 described later, the same exaggeration and simplification as in Figures 5 and 6 is applied. By mounting electronic components such as Si semiconductors (not shown) on the mounting surface 22 of the printed wiring board, a printed circuit board (not shown) is constructed.

[0020] The plate-shaped workpiece 20 is barrel polished using the centrifugal barrel polishing method and centrifugal barrel polishing machine 10 of this embodiment 1. Barrel polishing of the plate-shaped workpiece 20 gives the corners 24 of the ceramic substrate 21 a curved chamfer. The corners 24 that are to be chamfered include a ridge portion 25 where two surfaces of the outer surface of the ceramic substrate 21 meet at a right angle, and a vertex portion 26 where three surfaces meet at a right angle. Through the chamfering process, the ridge portion 25 is polished into a quarter-circle shape, and the vertex portion 26 is polished into a spherical shape. In the chamfering process (barrel polishing process), the conductor pattern 23 is not covered or masked by other materials, and the conductor pattern 23 remains exposed on the mounting surface 22 of the ceramic substrate 21.

[0021] The barrel polishing method of this embodiment 1 solves the problem of achieving good chamfering on the ceramic substrate 21 while suppressing wear of the exposed conductor pattern 23. The inventors of this application have gained knowledge on how to solve the above problem by trying multiple barrel polishing methods with different polishing conditions. The details of the polishing experiments tried are described below.

[0022] The common conditions for all polishing experiments are described below. In the barrel tank 12, 50 vol% of mass 16 (plate-shaped workpieces 20 and polishing stones 31, 32, 33) were placed relative to the space volume of the barrel tank 12. Of the 50 vol% mass 16, there were 30 plate-shaped workpieces 20, and the rest were occupied by polishing stones 31, 32, 33. The planar shape of the plate-shaped workpieces 20 (ceramic substrate 21) is rectangular. The plate-shaped workpieces 20 to be polished under these polishing conditions have a long side length of 3.2 mm, a short side length of 2.5 mm, and a ceramic substrate 21 thickness of 1 mm. The planar size of the plate-shaped workpieces 20 used under these polishing conditions is preferably a combination of the long and short sides within the range of 1 mm square to 5 mm square. The thickness of the ceramic substrate 21 can be selected as appropriate.

[0023] Each polishing experiment used only one type of polishing stone 31, 32, or 33 from among several types of polishing stones 31, 32, and 33. Furthermore, water was added to the barrel tank 12 containing the mass 16 to nearly fill the space of the barrel tank 12. The reason for adding water was to minimize damage to the plate-shaped workpiece 20. In barrel polishing for metal workpieces, 1 to 2 vol% of compound is added relative to the water volume to prevent rust on the workpiece and clogging of the polishing stones. However, since the object being polished in this experiment was a ceramic substrate 21 that was not susceptible to rust, no compound was used.

[0024] The conditions and results of each polishing experiment are described below. In Table 1, the centrifugal barrel polishing machine 10 used in polishing condition B-0 is a device in which the radius R of the orbit 15 traced by the rotation center (rotation axis 14) of the barrel tank 12 is 0.178 m, the rotational speed N of the barrel tank 12 is 3.33 rpm, the rotational speed n is -3.33 rpm, and the revolution-orbit ratio n / N is -1.00. G is defined as the acceleration due to gravity, and the relative centrifugal acceleration F on the orbit 15 during the planetary rotation of the barrel tank 12 is given by F = 4π 2 N 2 When defined as R / G, the relative centrifugal acceleration F under polishing condition B-0 is 7.95.

[0025]

[0026] Under polishing condition B-0, a ceramic, spherical polishing stone 31 was used for micro-cutting. The diameter 31D of the polishing stone 31 was 2 mm. "For micro-cutting" means that it is used to polish the surface of the workpiece smoothly while also providing a glossy finish. In barrel polishing under polishing condition B-0, the plate-shaped workpiece 20 in the barrel tank 12 was exposed to the vigorous flow of the mass 16, causing the plate-shaped workpiece 20 and the polishing stone 31 to jump out of the fluidized layer 16a that formed on the surface of the flow in the mass 16. After 240 minutes of barrel polishing, the corners 24 of the plate-shaped workpiece 20 were chamfered with a radius of 100 μm, but the wear of the conductive pattern 23 had progressed to a moderate degree, so the polishing result was evaluated as "poor".

[0027] Figures 11 and 12 schematically show the state of the plate-shaped workpiece 20 after polishing under polishing condition B-0. In Figures 11 and 12, the chamfering of the corners 24 and the degree of wear of the conductor pattern 23 are depicted in an exaggerated and simplified manner. In Figures 7 to 10, 13, and 14, which show the state of the plate-shaped workpiece 20 after polishing under polishing conditions B-1 to B-6 and F-1 to F-5 described later, the chamfering of the corners 24 and the degree of wear of the conductor pattern 23 are also depicted in an exaggerated and simplified manner.

[0028] In Table 1, the centrifugal barrel polishing machine 10 used for polishing conditions B-1 to B-6 is a device with an orbital radius R of 0.260 m. As shown in Table 1, in polishing condition B-1, the same polishing stone 31 as in polishing condition B-0 was used, the orbital rotation speed N was set to 3.80 rpm, the rotational rotation speed n was set to -1.67 rpm, the rotation-to-orbit ratio n / N was set to -0.44, and the relative centrifugal acceleration F was set to 15.09, and barrel polishing was performed for 120 minutes. In polishing condition B-1, the polishing time was half that of B-0, but the corners 24 were chamfered to a radius of 104 μm, similar to that in polishing condition B-0. However, the wear of the conductor pattern 23 was more severe than in polishing condition B-0, so the polishing result was evaluated as "poor". Figures 13 and 14 show the state of the plate-shaped workpiece 20 after polishing under polishing condition B-1.

[0029] In polishing condition B-2, the orbital speed N, the revolution-orbit ratio n / N, the relative centrifugal acceleration F, and the polishing time were the same as in polishing condition B-1. The polishing stone 32 used was made of ceramic and was designed for micro-cutting. As shown in Figure 3, the polishing stone 32 has a specific cross-sectional shape, which is roughly a star shape with an equilateral triangle. The length of one side 32S of the bottom surface of the polishing stone 32 is 4 mm, and the length 32L is 4 mm. This star-shaped polishing stone 32 is effective for polishing recesses and corners of the workpiece, but it does not produce as much surface gloss as the spherical micro-cutting polishing stone 31 used in polishing condition B-1. In polishing condition B-2, a good chamfer with a radius of 132 μm was achieved on the corners 24, but the wear of the conductor pattern 23 was severe, similar to polishing condition B-1, so the polishing result was evaluated as "poor". Figures 13 and 14 show the state of the plate-shaped workpiece 20 after polishing under polishing condition B-2.

[0030] In polishing condition B-3, the orbital speed N, relative centrifugal acceleration F, polishing time, and the polishing stone 32 used were the same as in polishing condition B-2, and the rotation-to-orbit ratio n / N was set to -0.33. In polishing condition B-3, the chamfering of the corners 24 was about the same as in polishing conditions B-0 and B-1, and the wear of the conductor pattern 23 was less than in polishing conditions B-0 and B-1. It is presumed that the flow became gentler and the wear of the conductor pattern 23 was reduced because the absolute value of the rotation-to-orbit ratio n / N was set lower than in polishing condition B-1 to -0.33. However, since wear had progressed, the polishing result was evaluated as "poor". Figures 9 and 10 show the state of the plate-shaped workpiece 20 after polishing under polishing condition B-3.

[0031] In polishing condition B-4, the orbital rotation speed N, relative centrifugal acceleration F, and revolution-orbit ratio n / N were set to the same conditions as in polishing condition B-3, and the polishing time was shortened to 90 minutes. Unlike polishing condition B-3, the polishing stone 33 used was made of resin and was intended for smooth finishing. The polishing stone 33 for smooth finishing has higher polishing power than the polishing stone 31 for micro-cutting, but because it is made of resin, the surface of the workpiece is less likely to become rough. The polishing stone 33 has a conical shape with a circular base. The diameter 33D of the base of the polishing stone 33 is 4 mm, and the height 33H of the polishing stone 33 is 4 mm. In polishing condition B-4, the wear of the conductive pattern 23 was about the same as in polishing condition B-3, but because the radius of the chamfered part of the corner 24 was 70 μm, the polishing result was evaluated as "poor". Figures 9 and 10 show the state of the plate-shaped workpiece 20 after polishing under polishing condition B-4.

[0032] Under polishing condition B-5, the revolution speed N was set to 4.36 rpm, higher than under polishing condition B-4, the revolution-autonomy ratio n / N was set to -0.15, the relative centrifugal acceleration F was set to 20, and barrel polishing was performed for 90 minutes, the same polishing time as under polishing condition B-4. The polishing stone 31 was the same as that used under polishing condition B-1. Under polishing condition B-5, the relative centrifugal acceleration F was set higher than under polishing condition B-4, and the absolute value of the revolution-autonomy ratio was set lower than under polishing condition B-4, with the aim of making the flow of the mass 16 gentler and reducing wear on the conductor pattern 23. Although there was almost no wear on the conductor pattern 23, the radius of the chamfered portion of the corner 24 became considerably smaller at 50 μm, so the polishing result was evaluated as "poor".

[0033] In polishing condition B-6, the rotational speed N, polishing time, and relative centrifugal acceleration F were the same as in polishing condition B-5, the rotation-orbit ratio n / N was set to -0.29, and the polishing stone 32 was the same as in polishing condition B-3. In polishing condition B-6, the flow of the mass 16 was rougher than in polishing condition B-5, and the radius of the chamfer of the corner 24 was a good 102 μm, but the wear of the conductor pattern 23 was about the same as in polishing conditions B-3 and B-4, so the polishing result was evaluated as "poor". Figures 9 and 10 show the state of the plate-shaped workpiece 20 after polishing under polishing condition B-6.

[0034]

[0035] The centrifugal barrel polishing machine 10 used for polishing conditions F-1 to F-5 in Table 2 is the same machine as the centrifugal barrel polishing machine 10 used for polishing conditions B-1 to B-6 in Table 1. The polishing stones 31 used for polishing conditions F-1 to F-5 are made of ceramic, the same material as those used for polishing conditions B-0, B-1, and B-5, and are spherical with a diameter of 2 mm, intended for micro-cutting.

[0036] Under polishing condition F-1, all conditions except for the polishing stone 31 were the same as those under polishing condition B-6. Under polishing condition F-1, the radius of the chamfered portion of the corner 24 was 91 μm, which was slightly smaller than that under polishing condition B-6, but there was no wear on the conductor pattern 23. Therefore, the polishing result under polishing condition F-1 was evaluated as "good". Figures 7 and 8 show the state of the plate-shaped workpiece 20 after polishing under polishing condition F-1.

[0037] Under polishing condition F-2, the rotational speed n was set slightly higher than under polishing condition F-1, resulting in a rotation-to-orbit ratio n / N of -0.32, while other conditions were kept the same as under polishing condition F-1. Under polishing condition F-2, the radius of the chamfered portion of the corner 24 was 100 μm, which was larger than under polishing condition F-1, and there was no wear on the conductor pattern 23. Therefore, the polishing result under polishing condition F-2 was evaluated as "good". Figures 7 and 8 show the state of the plate-shaped workpiece 20 after polishing under polishing condition F-2.

[0038] In polishing condition F-3, the rotational speed n was increased compared to polishing condition F-2, resulting in a rotation-to-orbit ratio n / N of -0.38, while other conditions were kept the same as in polishing condition F-2. In polishing condition F-3, the radius of the chamfered portion of the corner 24 was 122 μm, which was larger than in polishing condition F-2, and there was almost no wear on the conductor pattern 23. Therefore, the polishing result for polishing condition F-3 was evaluated as "good". Furthermore, from the results of polishing conditions F-1 to F-3, it was found that the wear on the conductor pattern 23 progressed, albeit slightly, as the absolute value of the rotation-to-orbit ratio n / N increased. Therefore, it was determined that the rotation-to-orbit ratio n / N of -0.38 in polishing condition F-3 was the limit of the acceptable range of wear on the conductor pattern 23. Figures 7 and 8 show the state of the plate-shaped workpiece 20 after polishing under polishing condition F-3.

[0039] Under the polishing condition F-4, the revolution speed N was set to 4.60 rps, the rotation speed n was decreased to -1.25 rps, the same as in the polishing condition F-1, the relative centrifugal acceleration F was increased to 22, and the rotation ratio n / N was set to = -0.27. Under the polishing condition F-4, the radius of the chamfer of the corner 24 was 97 μm, slightly larger than that in the polishing condition F-1, and there was no wear of the conductor pattern 23. Therefore, the polishing result of the polishing condition F-4 was evaluated as "good". FIGS. 7 and 8 show the state of the plate-like workpiece 20 after polishing under the polishing condition F-4.

[0040] Under the polishing condition F-5, the revolution speed N was set to 4.70 rps, higher than that in the polishing condition F-4, the rotation speed n was set to the same value as in the polishing condition F-4, and the relative centrifugal acceleration F was set to 23. The rotation ratio n / N was -0.27. Under the polishing condition F-5, the radius of the chamfer of the corner 24 was 100 μm, slightly larger than that in the polishing condition F-4, and there was no wear of the conductor pattern 23. Therefore, the polishing result of the polishing condition F-5 was evaluated as "good". FIGS. 7 and 8 show the state of the plate-like workpiece 20 after polishing under the polishing condition F-5.

[0041] According to the above polishing experiments, under the polishing conditions F-1 to F-5 where the rotation ratio n / N was set in the range of -0.4 ≤ n / N ≤ -0.2, the plate-like workpiece 20 in the barrel tank 12 was slowly moved while being pressed against the inner wall of the barrel tank 12 together with the abrasive 31 by the gentle flow layer 16a generated on the surface of the flow of the mass 16. For this reason, the conductor pattern 23 on the mounting surface 22 of the plate-like workpiece 20 was hardly polished, the corners 24 (ridge line part 25 and apex part 26) were preferentially polished, and good chamfers were provided at the corners 24.

[0042] The centrifugal barrel polishing method of the first embodiment is a method for chamfering the corners 24 of the substrate without wearing the functional layer, for a plate-like workpiece 20 in a form in which a functional layer different from the substrate is provided on the surface (mounting surface 22) of the substrate by using the centrifugal barrel polishing machine 10. The plate-like workpiece 20 is a ceramic substrate 21 made of ceramics, and the functional layer is a printed wiring board made of a conductor pattern 23.

[0043] The centrifugal barrel polishing machine 10 is configured such that a barrel tank 12 into which polishing stones 31, 32, 33 and a plate-shaped workpiece 20 are loaded is rotatably attached to an eccentric position of a rotating turret 11. In the first embodiment, let N be the revolution speed [rps] of the barrel tank 12, n be the rotation speed [rps] of the barrel tank 12, n / N be the rotation-revolution ratio of the barrel tank 12, R be the radius [m] of the revolution orbit 15 described by the rotation center of the barrel tank 12, G be the gravitational acceleration, and F = 4π 2 N 2 Define R / G as the relative centrifugal acceleration on the revolution orbit 15 during the planetary rotation of the barrel tank 12. In the barrel polishing method of the first embodiment, the relative centrifugal acceleration F was set in the range of 15 ≤ F ≤ 25, and the rotation-revolution ratio n / N of the barrel tank 12 was set in the range of -0.40 ≤ n / N ≤ -0.15 for polishing.

[0044] In the barrel polishing method of the first embodiment, in order to suppress the undulation of the surface (flow layer 16a) of the flow in the planetary-rotating barrel tank 12, the relative centrifugal acceleration F on the revolution orbit 15 of the barrel tank 12 was set in the range of 15 ≤ F ≤ 25, which is larger than the value when a metal workpiece is the polishing target. Further, the rotation-revolution ratio n / N of the barrel tank 12 was set in the range of -0.40 ≤ n / N ≤ -0.15, in which the ratio of n is reduced compared to the case where a metal workpiece is the polishing target. When polishing the plate-shaped workpiece 20 using the centrifugal barrel polishing machine 10 with the revolution direction and the rotation direction of the barrel tank 12 being opposite, if the undulation in the surface (flow layer 16a) of the mass 16 composed of the polishing stones 31, 32, 33 and the plate-shaped workpiece 20 in the barrel tank 12 is reduced, the plate-shaped workpiece 20 in the flow moves not in a violent motion that randomly changes its orientation but in a relatively stable posture in the direction along the plate surface of the substrate.

[0045] By making such a motion, the corner 24 on the tip side in the moving direction of the ceramic substrate 21 is effectively polished by the polishing stones 31, 32, 33. Since the polishing stones 31, 32, 33 do not collide with the surface of the substrate from the front but contact it in a rubbing manner, the wear of the conductor pattern 23 by the polishing stones 31, 32, 33 is reduced. Therefore, according to the centrifugal barrel polishing method of the first embodiment, the wear of the conductor pattern 23 can be suppressed without covering the conductor pattern 23 with a separate member.

[0046] For polishing conditions F-1 to F-5, the relative centrifugal acceleration F was set to the range of 20 ≤ F ≤ 25. Under this condition, the undulation on the surface of the flow in the mass 16 consisting of polishing stones 31 and plate-shaped workpieces 20 in the barrel tank 12 (fluidized bed 16a) was reduced, thus further reducing the wear of the conductor pattern 23 by the polishing stones 31. For polishing conditions F-1 to F-5, the rotation-orbit ratio n / N of the barrel tank 12 was set to the range of -0.40 ≤ n / N ≤ -0.20. Under this configuration, the undulation on the surface of the flow in the mass 16 consisting of polishing stones 31 and plate-shaped workpieces 20 in the barrel tank 12 (fluidized bed 16a) was reduced, thus further reducing the wear of the conductor pattern 23 by the polishing stones 31.

[0047] In polishing conditions F-1 to F-5, spherical abrasive stones 31 with a diameter 31D of 2 mm or more and 4 mm or less were used as the abrasive stones 31 placed in the barrel tank 12. With this configuration, good polishing was achieved. In polishing conditions F-1 to F-5, the abrasive stones 31 were made of ceramic. With this configuration, wear of the abrasive stones 31 can be suppressed.

[0048] [Other Embodiments] The present invention is not limited to the embodiments described above and in the drawings, and the following embodiments, for example, are also included in the technical scope of the present invention. The present invention can also be applied when the plate-shaped workpiece is an electronic component other than a printed circuit board, or a component other than an electronic component. The present invention can also be applied when the ceramic substrate is, for example, an LTCC substrate (Low Temperature Co-fired Ceramics). The relative centrifugal acceleration F on the orbit of the barrel bath may be set in the range of 15 ≤ F < 20. In this case as well, the chamfering of the corners of the substrate can be performed well while suppressing wear of the functional layer. The rotation-orbit ratio n / N of the barrel bath may be set in the range of -0.20 < n / N ≤ -0.15. As abrasive stones, spheres with a diameter of less than 2 mm may be used, or spheres with a diameter of more than 4 mm may be used. The abrasive stones are not limited to ceramic, but may also be made of synthetic resin. The number of barrel baths constituting the barrel polishing machine may be three or less, or five or more. The substrate material constituting the plate-shaped workpiece is not limited to ceramic; it may also be aluminum nitride, silicon nitride, alumina, or the like.

[0049] 10...Centrifugal barrel polishing machine 11...Turret 12...Barrel tank 14...Rotation axis (center of rotation) 15...Orbit 20...Plate-shaped workpiece 21...Ceramic substrate (substrate) 22...Mounting surface (surface) 23...Conductor pattern (functional layer) 24...Corner 31, 32, 33...Polishing stone

Claims

1. A centrifugal barrel polishing method for chamfering the corners of a plate-shaped workpiece having a functional layer of a different nature from the substrate on its surface, wherein a centrifugal barrel polishing machine is used in which a barrel tank into which polishing stones and the plate-shaped workpiece are fed is mounted rotatably at an eccentric position of a rotating turret, where N is the rotational speed of the barrel tank [rps], n is the rotational speed of the barrel tank [rps], n / N is the rotational ratio of the barrel tank, R is the radius of the orbit traced by the rotation center of the barrel tank [m], G is the acceleration due to gravity, and F = 4π 2 N 2 A centrifugal barrel polishing method in which R / G is defined as the relative centrifugal acceleration on the orbit during the planetary rotation of the barrel tank, the relative centrifugal acceleration F is set in the range of 15 ≤ F ≤ 25, and the rotation-orbit ratio n / N is set in the range of -0.40 ≤ n / N ≤ -0.

15.

2. The centrifugal barrel polishing method according to claim 1, wherein the plate-shaped workpiece is a printed circuit board in which the substrate is made of ceramics and the functional layer is made of a conductive pattern.

3. The centrifugal barrel polishing method according to claim 1 or claim 2, wherein the relative centrifugal acceleration F is set to a range of 20 ≤ F ≤ 25.

4. The centrifugal barrel polishing method according to claim 1 or claim 2, wherein the rotation-orbit ratio n / N is set to the range of -0.40 ≤ n / N ≤ -0.

20.

5. The centrifugal barrel polishing method according to claim 1 or claim 2, wherein the abrasive stones to be placed in the barrel tank are spherical in shape with a diameter of 2 mm or more and 4 mm or less.

6. The centrifugal barrel polishing method according to claim 5, wherein the polishing stone is made of ceramics.

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