Method and device for casting a ring-shaped plastic frame in a recess of a rotor disk of a double-sided machining machine

Abstract

A method for casting a ring-shaped plastic frame comprises providing two mold parts, wherein at least one of the two molds parts includes at least one ring-shaped seat. Positioning a rotor disk between the two mold parts where the rotor disk comprises at least one annular recess. Engaging a mold core with at least a portion of each of the two mold parts. The mold core comprises at least one casting channel configured to attach at one end to a supply of plastified plastic. Inserting at least one mold insert into the at least one ring-shaped seat. A mold volume is defined by the at least one mold insert, the mold core and an edge of the at least one annular recess, wherein the mold volume is configured to fluidly connect with the at least one casting channel to receive plastified plastic to form a plastic frame.

Claims

1. A method for casting a ring-shaped plastic frame into at least one circular recess in a rotor disk adapted to accommodate wafers for machining in a double-sided machining machine, the method comprising: providing a first mold part comprising at least one annular pocket; providing a second mold part comprising at least one annular pocket; positioning a rotor disk at least partially between the first mold part and the second mold part; positioning a first releasable mold insert within the at least one annular pocket of the first mold part; positioning a second releasable mold insert within the at least one annular pocket of the second mold part; and engaging a mold core with the first mold pant and the second mold part, Wherein the mold core comprises at least one casting channel configured to connect at one end to a supply of casting material, wherein a mold volume is defined by the first releasable mold insert, the second releasable mold insert, the rotor disk, and the mold core, and wherein the mold volume is fluidly connected to the at least one casting channel.

2. The method according to claim 1, herein the at least one annular pocket of at least one of the first mold part and the second mold part is configured to accommodate a plurality of differently dimensioned releasable mold inserts.

3. The method according to claim 1, wherein the mold volume extends beyond the circular recess of the rotor disk in an axial direction.

4. The method according to claim 1, wherein the mold volume includes one or more additional cavities configured for feeders.

5. The method according to claim 1, wherein the at least one casting channel is heated.

6. A method for casting a ring-shaped plastic frame, the method comprising: providing two mold parts, wherein at least one of the two molds parts includes at least one ring-shaped seat; positioning a rotor disk between the two mold pans, the rotor disk comprising at least one annular recess; engaging a mold core with at least a portion of each of the two mold parts, the mold core comprising at least one casting channel configured to attach at one end to a supply of plastified p plastic; and inserting at least one mold insert into the at least one ring-shaped seat, wherein a mold volume is defined by the at least one mold insert, the mold core and an edge of the at least one annular recess, wherein the mold volume is configured to fluidly connect with an opposite end of the at least one casting channel, and wherein the mold volume is configured to receive plastified plastic from the at least one casting channel to form a plastic frame.

7. The method according to claim 6, wherein at least one mold insert is releasably inserted in at least one ring-shaped seat of each of the mold parts such that the at least one mold insert together with the mold core and the edge of the at least one annular recess delimit the mold volume provided for the plastic frame.

8. The method according to claim 6, wherein the at least one ring-shaped seat is configured to accommodate differently dimensioned mold inserts for casting differently dimensioned plastic frames.

9. The method according to claim 6, wherein the mold volume is at least partially defined by a portion of the rotor disk, and wherein the mold volume extends beyond the at least one annular recess of the rotor disk in an axial direction.

10. The method according to claim 6, wherein one or more feeders is formed on the plastic frame.

11. The method according to claim 6, wherein the at least one casting channel is heated.

12. The method according to claim 6, wherein the mold volume includes one or more additional cavities configured for feeders.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the invention is explained in more detail with reference to the figures. Schematically,

(2) FIG. 1 shows a sectional view of an embodiment of the casting device,

(3) FIG. 2 shows a sectional enlargement of a region of an embodiment of the casting device in a first operating state schematically portrayed at A in FIG. 1,

(4) FIG. 3 shows the casting device of FIG. 2 in second operating state,

(5) FIG. 4 shows the casting device of FIG. 2 in a third operating state,

(6) FIG. 5 shows the perspective view from FIG. 4 according to another exemplary embodiment,

(7) FIG. 6 shows excerpts of sectional views of rotor disks with different plastic frames produced by the method according to the invention, and

(8) FIG. 7 shows an example of a plastic frame produced using the method according to the invention, or respectively the device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) If not otherwise specified, the same reference numbers indicate the same objects in the figures. The device shown in FIG. 1 has a first mold part 10, in particular a first mold half, and a second mold part 12, in particular a second mold half A rotor disk 14 of a double-sided machining machine, in particular a double-sided polishing machine, is clamped between the mold parts 10, 12 and accordingly held. The rotor disk 14 possesses a plurality of for example circular recesses 16 of which one can be seen in FIG. 1. During operation, e.g. circular semiconductor wafers such as silicon wafers are held floating in the recesses 16 to be machined in a double-sided machining machine. The device shown in FIG. 1 furthermore has a mold core 18 which is inserted in the recess 16 and fills it up to a mold cavity 20. In one embodiment, the mold cavity 20 is ring-shaped. Reference signs 22, 24 schematically indicate casting channels formed in the mold core 18 in FIG. 1. At its top end in FIG. 1, the central casting channel 22 is connected to a supply (not shown) for molten plastic such as an extruder. The casting channels 24 connected to the central casting channel 22 terminate in the mold cavity 20. During operation, the molten plastic is conducted from the supply through the casting channels 22, 24 into the mold cavity 20 as indicated by the arrows in FIG. 1.

(10) In FIG. 2, it can be seen that in the device according to the invention, the mold parts 10, 12 each have a ring-shaped pocket, such as a circular ring-shaped seat, wherein a ring-shaped component, such as a circular ring-shaped mold insert 26, 28 is releasably inserted into the ring-shaped seat. The mold inserts 26, 28 can for example be screwed to the mold parts 10, 12. As can be seen in FIG. 2, the mold cavity 20, which is also ring-shaped, e.g. circular ring shaped, is delimited by the mold core 18, the inner edge of the rotor disk 14 forming the recess 16 and the insides of the annular ring-shaped mold inserts 26, 28. This mold cavity 20 forms the mold volume provided for the plastic frame to be cast in the rotor disk 14.

(11) FIG. 3 depicts the operating state shortly after casting still meltable plastic 30 through the mold channels 22, 24 in the mold cavity 20. It can clearly be seen in FIGS. 2 and 3 that the mold cavity 20 provided for the plastic frame possesses a longer extension than the rotor disk 14 in the axial direction of the recess 16, i.e., from bottom to top in FIGS. 2 and 3. Correspondingly, the still flowable plastic material projects slightly above the top and bottom of the rotor disk 14 in FIG. 3. By means of this embodiment, the shrinkage is compensated that occurs while the plastic material cools and dries. FIG. 4 shows the hardened state of the plastic material 30 forming the plastic frame. As can be easily discerned in FIG. 4, the plastic material 30 is flush with the top side and bottom side of the rotor disk 14 in this hardened state. Merely for the sake of completeness, it is noted that the gap which can for example be discerned in FIG. 3 between the top side, or respectively the bottom side of the rotor disk 14 and associated surfaces of the mold inserts 26, 28 is small enough so that the plastified plastic 30 cannot penetrate into this gap due to its viscosity.

(12) The embodiment in FIG. 5 differs from the embodiment shown in FIGS. 2 to 4 such that the ring-shaped mold insert 26′ inserted into the top mold part 10 is thicker than the ring-shaped insert 26′ shown in FIGS. 2 to 4. FIG. 5 shows the cooled and hardened state of the plastic material 30. In FIG. 5, it can be seen that, due to the greater thickness of the mold insert 26′, the hardened plastic 30 does not extend completely up to the top side of the rotor disk 14.

(13) With the device according to the invention, or respectively the method according to the invention, precise desired dimensions of the plastic frame formed by the plastic material 30 can be flexibly produced by appropriately selecting the respective cast inserts. Different frame geometries that are possible by means of the invention are shown as an example in FIG. 6.

(14) FIG. 7 shows a plastic frame 32 without the rotor disk for reasons of illustration that is produced by means of the method according to the invention, or respectively the device according to the invention. It can be seen that the plastic frame 32 has a dovetailed shape 34 at its outer perimeter which corresponds to a an equivalent dovetailed shape on the inner surface of the recess 16 in the rotor disk 14. At reference signs 36, 38, feeders, or respectively risers can also be seen distributed at regular intervals across the inside of the plastic frame 32 which were generated during the plastic injection molding process. These feeders are removed during the finishing of the plastic frame 32. These are in particular to prevent the formation of cavities during the plastic injection molding process and enable lower injection and holding pressures. This in turn produces more homogeneous crystallization of the plastic material 30 and hence improved shape retention of the plastic frame 32.

(15) By means of the invention, precisely centered plastic frames can be produced in the axial direction of the recesses of the rotor disks. A deviation in thickness in this axial direction can be limited for example to ±5 μm, preferably ±2 μm, and more preferably ±1 μm. This holds true in particular for each location of the plastic frame that is at least 0.5 mm and at most 1 mm distant from an inner edge of the plastic frame. The deviation in thickness of the plastic frame can for example lie within a bandwidth of 10 μm, preferably 4 μm, more preferably 2 μm around a target value, for example for at least 90% of its lateral extension within an area of 0.5 mm to 1 mm from an inner edge.

(16) All of the indicated values are with reference to room temperature and dry rotor disks with plastic frames that have only experienced absorption of water only from normal ambient air.