# Patent

## Title
Glass mold polishing method and structure

## Abstract

A glass mold polishing structure and method. The method includes providing a polishing tool comprising mounting plate, a chuck plate over and mechanically attached to the mounting plate, and a pad structure over and mechanically attached to the chuck plate. A retaining structure is attached the chuck plate. A glass mold comprising a plurality of cavities is placed on the pad structure and within a perimeter formed by the retaining structure. A vacuum device is attached to the chuck plate. The vacuum device is activated such that a vacuum is formed and mechanically attaches the glass mold to the pad structure. The polishing tool comprising the glass mold mechanically attached to the pad structure is placed over and in contact with the polishing pad. The polishing tool comprising the glass mold is rotated. The glass mold is polished as a result of the rotation.

## Background
FIELD OF THE INVENTION
The present invention relates to a method and associated structure for polishing a glass mold.
BACKGROUND OF THE INVENTION
Removing unwanted portions of structures typically comprises a complicated and unreliable process. Accordingly, there exists a need in the art to overcome at least one of the deficiencies and limitations described herein above.
SUMMARY OF THE INVENTION
The present invention provides a method comprising:
providing a polishing tool comprising mounting plate, a chuck plate over and mechanically attached to said mounting plate, and a pad structure over and mechanically attached to said chuck plate, wherein the chuck plate comprises a first plurality of thru-holes, wherein the pad structure comprises a second plurality of thru-holes, and wherein each thru-hole of the second plurality of thru-holes is located over an associated thru-hole of the first plurality of thru-holes;
mechanically attaching a retaining structure to the chuck plate;
placing a glass mold comprising a plurality of cavities on the pad structure and within a perimeter formed by the retaining structure, wherein a bottom surface of the glass mold is in contact with the pad structure, and wherein the plurality of cavities are formed within a top surface of the glass mold;
attaching a vacuum device to the chuck plate;
activating the vacuum device such that a vacuum is formed within each thru-hole of the second plurality of thru-holes and each associated thru-hole of the first plurality of thru-holes, wherein the vacuum mechanically attaches the bottom surface of the glass mold to the pad structure;
placing the polishing tool comprising the glass mold mechanically attached to the pad structure over a polishing pad such that the top surface of the glass mold is in contact with the polishing pad;
applying a polishing substance to the polishing pad;
first rotating at a first speed and in a first direction, the polishing tool comprising the glass mold mechanically attached to the pad structure; and
polishing for a specified time period, the glass mold.
The present invention provides a structure comprising:
a polishing tool comprising mounting plate, a chuck plate over and mechanically attached to the mounting plate, and a pad structure over and mechanically attached to the chuck plate, wherein the chuck plate comprises a first plurality of thru-holes, wherein the pad structure comprises a second plurality of thru-holes, and wherein each thru-hole of the second plurality of thru-holes is located over an associated thru-hole of the first plurality of thru-holes;
a retaining structure mechanically attached to the chuck plate;
a glass mold comprising a plurality of cavities placed on the pad structure and within a perimeter formed by the retaining structure, wherein a bottom surface of the glass mold is in contact with the pad structure, and wherein the plurality of cavities are formed within a top surface of the glass mold;
a vacuum device attached to the chuck plate, wherein the vacuum device is configured to form a vacuum within each thru-hole of the second plurality of thru-holes and each associated thru-hole of the first plurality of thru-holes, and wherein the vacuum mechanically attaches the bottom surface of the glass mold to the pad structure; and
a polishing pad in mechanical contact with the top surface of the glass mold, wherein the polishing tool is configured to rotate at a first speed and in a first direction and polish the glass mold for a specified time period.
The present invention advantageously provides a simple method and associated apparatus for removing unwanted portions of structures.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A illustrates a cross sectional view of a mold used for applying solder to an electrical structure, in accordance with embodiments of the present invention.
FIG. 1B illustrates a cross sectional view of a first alternative mold used for applying solder to an electrical structure, in accordance with embodiments of the present invention.
FIG. 1C illustrates a cross sectional view of a second alternative mold used for applying solder to an electrical structure, in accordance with embodiments of the present invention.
FIG. 2 illustrates an exploded view of a system used for removing the sharp corners of FIG. 1A and/or the rounded portions of FIG. 1B, in accordance with embodiments of the present invention.
FIG. 3 illustrates a cross sectional view of a system used for removing sharp corners of FIG. 1A, in accordance with embodiments of the present invention.
FIG. 4 illustrates a cross sectional view of a system used for removing rounded portions of FIG. 1B, in accordance with embodiments of the present invention.
FIG. 5 illustrates a cross sectional view of a system comprising a mold with rounded corners, in accordance with embodiments of the present invention.
FIG. 6 illustrates a flowchart detailing process steps for forming the mold of FIG. 3, in accordance with embodiments of the present invention.



DETAILED DESCRIPTION OF THE INVENTION
FIG. 1A illustrates a cross sectional view of a mold 32a used for forming solder balls and applying the solder balls to an electrical structure, in accordance with embodiments of the present invention. Mold 32a may comprise any material including, inter alia, glass, metal, plastic, etc. Mold 32a may comprise any shape including, inter alia, rectangular, circular, triangular, etc. Mold 32a is used to form solder balls. Additionally, mold 32a may be used to apply the solder balls to any type of electrical structure including, inter alia, a semiconductor device, a semiconductor wafer, a substrate (e.g., a printed circuit board, a chip carrier, etc), etc. Mold 32a comprises cavities 29a (e.g., surface pits) that are used to form and hold injection molded solder for application to an electrical structure. Although mold 32a comprises four cavities 29a, note that mold 32a may comprise any number of cavities (e.g., millions). In the case of a glass mold (i.e., mold 32a), cavities 29a may be formed by: chemically etching the glass through a mask and then removing the mask, a laser process, etc. Cavities 29a comprise very sharp corners 30a formed at a junction between a top surface 39a of mold 32a and side surfaces 37 of mold 32a (i.e., the junction between a top surface 39a of mold 32a and side surfaces 37 of mold 32a form a ninety degree angle). Corners 30a are sharp and therefore they may damage rubbery seals used in an injection molded solder head (e.g., a C4NP injection molded solder head) while solder is injected into cavities 29a. The seals form an interface between the injection molded solder head and mold 32a. The seals hold in a molten, pressurized solder. Additionally, the seals may be used to enclose an area of vacuum which removes air from the cavities before the solder is injected. As the seals are damaged (i.e., by corners 30a), debris (from the rubber seals) may contaminate the solder that is injected into cavities 29a. Systems 2a-2d of FIGS. 2-5 are used to remove sharp edges 30a as described, infra.
FIG. 1B illustrates a cross sectional view of a mold 32b similar to mold 32a of FIG. 1 used for forming solder balls and applying the solder balls to an electrical structure, in accordance with embodiments of the present invention. In contrast with mold 32a of FIG. 1, mold 32 b of FIG. 2 comprises rounded portions 39b of top surface 39a (i.e., extending above top surface 39a) of mold 32b forming a perimeter surrounding cavities 29a. Rounded portions 39b may be formed while using a laser process for forming cavities 29a. Rounded portions 39b may damage rubbery seals used in an injection molded solder head (e.g., a C4NP injection molded solder head) while solder is injected into cavities 29a and therefore systems 2a-2d of FIGS. 2-5 are user to remove rounded portions 39b as described, infra.
FIG. 1C illustrates a cross sectional view of a mold 32c formed from mold 32a of FIG. 1 or mold 32b of FIG. 2, in accordance with embodiments of the present invention. In contrast with mold 32a of FIG. 1, mold 32c of FIG. 3 comprises rounded edges 30b formed a junction between top surface 39a of mold 32c and side surfaces 37 of cavities 29b. In contrast with mold 32b of FIG. 2, mold 32c of FIG. 3 comprises rounded edges 30b formed a junction between top surface 39a of mold 32c and side surfaces 37 of cavities 29b. Additionally, rounded portions 39b have been removed. Removing rounded portions 39b and sharp corners 39a prevents damage to the rubbery seals used in an injection molded solder head during a solder injection process because rounded corners will not damage the rubbery seals. Rounded portions 39b and sharp corners 39a are removed using systems 2a-2d of FIGS. 2-5 and the algorithm of FIG. 6 as described, infra.
FIG. 2 illustrates an exploded view of a system 2a used for removing sharp corners 30a of FIG. 1A and/or rounded portions 39b of FIG. 1B, in accordance with embodiments of the present invention. System 2a comprises a polishing tool 17, retaining rails 18a . . . 18d, mold 32 (representing any of molds 32a . . . 32c), a vacuum device 22, and a polishing pad 34. Polishing tool 17 comprises a mounting plate 6, a chuck plate 14 (comprising interior portion 14a) over and mechanically attached to mounting plate 6, and a pad structure 28 over and mechanically attached to chuck plate 14. Each of mounting plate 6, chuck plate 14, and interior portion 14a of chuck plate may comprise any type of material including, inter alia, metal, plastic, etc. Mounting plate 6 may comprise any shape including, inter alia, rectangular, circular, triangular, etc. Chuck plate may comprise any shape including, inter alia, rectangular, circular, triangular, etc. Interior portion 14a of chuck plate 14 comprises thru-holes 9a. Interior portion 14a may comprise any shape including, inter alia, rectangular, circular, triangular, etc. Pad structure 28 thru-holes 9b. Each of thru-holes 9b is located over an associated thru-hole of thru-holes 9a. Thru-holes 9a and 9b are all connected together via tube 11. Tube 11 is connected to vacuum device 22. Vacuum device 22 forms a vacuum within thru-holes 9a and 9b. The vacuum within thru-holes 9a and 9b mechanically attaches a bottom surface 39c of mold 32 to pad structure 28 thereby attaching pad structure 28 to chuck plate 14. Additionally, an adhesive may be used to attach pad structure 28 to chuck plate 14. Retaining rails 18a . . . 18d may be mechanically attached to chuck plate 14. Retaining rails 18a . . . 18d may be mechanically attached to chuck plate 14 using any attachment device/substance such as, inter alia, screws, rivets, adhesive, welding materials, etc. Retaining rails 18a . . . 18d are used to keep mold 32 from shifting during a polishing process. Retaining rails 18a . . . 18d may comprise any type of material including, inter alia, metal, plastic, etc. Retaining rails 18a . . . 18d are shown for illustration purposes. Note that any type of retaining structure (e.g., a retaining ring, a retaining box, etc) may be substituted for retaining rails 18a . . . 18d. A motor 24a (e.g., electric, gas, etc) may be attached to mounting plate 6. Motor 24a is used to rotate in any direction (e.g., clockwise, counter clockwise, etc), polishing tool 17 (i.e., with mold 32 attached) over (and in contact with) polishing pad 34 in order to remove sharp corners 30a of FIG. 1A and/or rounded portions 39b of FIG. 1B. Polishing pad 34 may comprise an abrasive surface that removes corners 30a of FIG. 1A and/or rounded portions 39b of FIG. 1B as the rotating mold 32 contacts polishing pad 34. Polishing pad 34 may comprise any type of polishing pad including, inter alia, a Rohm-Haas Embossed Polytex pad (i.e., soft and compliant). A polishing liquid (e.g., a slurry comprising abrasive particles) may be continuously applied (e.g., using a dispensing apparatus) to polishing pad 34 to aid polishing pad 34 in removing corners 30a of FIG. 1A and/or rounded portions 39b of FIG. 1B. For example, colloidal silica slurry with a 30-N-50, 50 nm particle size and a 30% solid in an Ammonium Hydroxide chemistry with a pH of 10 may be used. Polishing tool 17 (i.e., with mold 32 attached) may be rotated at any speed (e.g., 1-1000 RPMs) and for any time period (e.g., 10 seconds to 4 minutes) over (and in contact with) polishing pad 34 in order to remove sharp corners 30a of FIG. 1A and/or rounded portions 39b of FIG. 1B. Additionally, a specified amount of pressure (e.g., 2-30 PSI) may be applied to polishing tool 17 during the rotation process.
FIG. 3 illustrates a cross sectional view of a system 2b (similar to system 2a of FIG. 2) used for removing sharp corners 30a of mold 32a, in accordance with embodiments of the present invention. In addition to system 2a of FIG. 2, system 2b of FIG. 3 comprises an additional motor 24b (e.g., electric, gas, etc) for rotating polishing pad 34. Motor 24b is used to rotate in any direction (e.g., clockwise, counter clockwise, etc), polishing pad 34 in order to remove sharp corners 30a. For example, motor 24b could be rotated in a same direction as motor 24a. Alternatively, motor 24b could be rotated in a different direction (e.g., an opposite direction) from motor 24a. Motor 24b could be rotated at a same speed or different speed from motor 24a. Motor 24b could be rotated for a same amount of time or for a different amount of time as motor 24a. Additionally, a process could be performed wherein motor 24b could be rotated in a first direction, at a first speed, for a first specified amount of time, while motor 24a is rotated in a second direction, at a second speed, for a second specified amount of time. Then both motors could be stopped (i.e., rotation stopped) and motor 24b could be rotated in the second direction, at a third speed, for a third specified amount of time, while motor 24a is rotated in a first direction, at a fourth speed, for a fourth specified amount of time.
FIG. 4 illustrates a cross sectional view of a system 2c (similar to system 2b of FIG. 3) used for removing sharp corners 30a and/or rounded portions 39b of mold 32b, in accordance with embodiments of the present invention. In contrast with system 2b of FIG. 3, system 2c of FIG. 4 comprises mold 32b comprising rounded portions 39b. 
FIG. 5 illustrates a cross sectional view of a system 2d similar to system 2c of FIG. 4, in accordance with embodiments of the present invention. In contrast with system 2b of FIG. 3 and system 2c of FIG. 4, system 2d of FIG. 5 comprises a mold 32c comprising rounded edges 30b formed a junction between top surface 39a of mold 32c and side surfaces 37 of cavities 29b. Rounded edges 30b are formed as a result of the polishing process performed and described with reference to FIGS. 1-4.
FIG. 6 illustrates a flowchart detailing process steps for forming mold 32c of FIG. 3, in accordance with embodiments of the present invention. Mold 32c is formed from mold 32a of FIG. 1 and/or mold 32b of FIG. 2. In step 40, a polishing tool (e.g., polishing tool 17 of FIG. 2) provided. The polishing tool comprises a mounting plate (e.g., mounting plate 6 of FIG. 2), a chuck plate (e.g., chuck plate 14 of FIG. 2) over and mechanically attached to the mounting plate, and a pad structure (e.g., pad structure 28 of FIG. 2) over and mechanically attached to the chuck plate. In step 42, retaining rails or a retaining structure (e.g., retaining rails 18a . . . 18d of FIG. 2) are mechanically attached to the chuck plate using any attachment device/substance such as, inter alia, screws, rivets, adhesive, welding materials, etc. The retaining rails are used to keep a mold (e.g., mold 32 of FIG. 2) from shifting during a polishing process. In step 44, the mold (i.e., comprising a plurality of cavities 29a of FIG. 1A, sharp corners 30a of FIG. 1A, and/or rounded portions 39b of FIG. 1B is placed on the pad structure and within a perimeter formed the retaining rails. A bottom surface of the glass mold is in contact with the pad structure. In step 46 a vacuum device (e.g., vacuum device 22 of FIG. 2) is attached to the chuck plate. In step 48, the vacuum device is activated such that a vacuum is formed within each of thru-hole 9a and 9b of FIG. of FIG. 2. The vacuum mechanically attaches the bottom surface of the mold to the pad structure (and the polishing tool). In step 50, the polishing tool comprising the mold mechanically attached is placed over the polishing pad such that the top surface (and sharp corners 30a of FIG. 1A, and/or rounded portions 39b of FIG. 1B) of the glass mold is in contact with the polishing pad. Step 50 may be performed after step 48. In step 52, a polishing substance/liquid (e.g., a slurry comprising abrasive particles) is optionally applied to the polishing pad. Step 52 may be performed after or before step 50. In step 54, the polishing tool is rotated by a motor (e.g., at a first speed and in a first direction). Step 54 may be performed before or after step 52. In step 56, the polishing pad is rotated by a motor (e.g., at a second speed and in a second direction). In step 58, sharp corners 30a of FIG. 1A, and/or rounded portions 39b of FIG. 1B are removed as a result of steps 54 and/or 56.
While embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention.

## Claims

1. A method comprising:
providing a polishing tool comprising mounting plate, a chuck plate over and mechanically attached to said mounting plate, and a pad structure over and mechanically attached to said chuck plate, wherein said chuck plate comprises a first plurality of thru-holes, wherein said pad structure comprises a second plurality of thru-holes, and wherein each thru-hole of said second plurality of thru-holes is located over an associated thru-hole of said first plurality of thru-holes;
mechanically attaching a retaining structure to said chuck plate;
placing a glass mold comprising a plurality of cavities on said pad structure and within a perimeter formed by said retaining structure, wherein a bottom surface of said glass mold is in contact with said pad structure, and wherein said plurality of cavities are formed within a top surface of said glass mold;
attaching a vacuum device to said chuck plate;
activating said vacuum device such that a vacuum is formed within each said thru-hole of said second plurality of thru-holes and each said associated thru-hole of said first plurality of thru-holes, wherein said vacuum mechanically attaches said bottom surface of said glass mold to said pad structure;
placing said polishing tool comprising said glass mold mechanically attached to said pad structure over a polishing pad such that said top surface of said glass mold is in contact with said polishing pad;
applying a polishing substance to said polishing pad;
first rotating at a first speed and in a first direction, said polishing tool comprising said glass mold mechanically attached to said pad structure; and
polishing for a specified time period, said glass mold.

2. The method of claim 1, wherein each portion of a plurality of portions of said top surface of said glass mold is raised above all other portions of said top surface of said glass mold and forms a perimeter around an associated cavity of said plurality of cavities, and wherein said polishing said glass mold comprises removing said plurality of portions of said top surface of said glass mold.

3. The method of claim 1, wherein said polishing said glass mold comprises removing portions of sharp corners formed at a junction between said top surface of said glass mold and side surfaces of said cavities resulting in rounded corners formed between said top surface of said glass mold and said side surfaces of said cavities.

4. The method of claim 3, wherein each sharp corner of said sharp corners forms an angle of ninety degrees.

5. The method of claim 1, further comprising:
disabling said first rotating; and
second rotating, at said first speed and in a second direction opposite to said first direction, said polishing tool comprising said glass mold mechanically attached to said pad structure, wherein said second rotating is performed after said disabling.

6. The method of claim 1, further comprising:
disabling said first rotating; and
second rotating, at a second speed and in a second direction opposite to said first direction, said polishing tool comprising said glass mold mechanically attached to said pad structure, wherein said second rotating is performed after said disabling, and wherein said second speed differs from said first speed.

7. The method of claim 1, rotating said polishing pad at said first speed and in said first direction.

8. The method of claim 1, rotating said polishing pad at a second speed and in said first direction, wherein said second speed differs from said first speed.

9. The method of claim 1, rotating said polishing pad at said first speed and in a second direction opposite to said first direction.

10. The method of claim 1, rotating said polishing pad at a second speed and in a second direction opposite to said first direction.

11. The method of claim 1, applying a specified amount of pressure to said polishing tool during said first rotating.

12. The method of claim 1, wherein said first rotating is performed by a motor.

13. The method of claim 1, wherein said mechanically attaching said retaining structure to said chuck plate comprises using of screws to perform said mechanically attaching.

14. The method of claim 1, further comprising using said glass mold is used for applying injection molded solder structures to an electrical structure.

15. The method of claim 1, wherein said polishing substance comprises a slurry comprising abrasive particles.

16. A structure comprising:
a polishing tool comprising a mounting plate, a chuck plate over and mechanically attached to said mounting plate, and a pad structure over and mechanically attached to said chuck plate, wherein said chuck plate comprises a first plurality of thru-holes, wherein said pad structure comprises a second plurality of thru-holes, and wherein each thru-hole of said second plurality of thru-holes is located over an associated thru-hole of said first plurality of thru-holes;
a retaining structure mechanically attached to said chuck plate;
a glass mold comprising a plurality of cavities placed on said pad structure and within a perimeter formed by said retaining structure, wherein a bottom surface of said glass mold is in contact with said pad structure, and wherein said plurality of cavities are formed within a top surface of said glass mold;
a vacuum device attached to said chuck plate, wherein said vacuum device is configured to form a vacuum within each said thru-hole of said second plurality of thru-holes and each said associated thru-hole of said first plurality of thru-holes, and wherein said vacuum mechanically attaches said bottom surface of said glass mold to said pad structure; and
a polishing pad in mechanical contact with said top surface of said glass mold, wherein said polishing tool is configured to rotate at a first speed and in a first direction and polish said glass mold for a specified time period;
a first motor assembly directly attached to said polishing pad, wherein said first motor assembly is configured to rotate said polishing pad; and
a second motor assembly attached to said mounting plate, wherein said second motor assembly is configured to rotate said polishing tool at said first speed and in said first direction and polish said glass mold for said specified time period.

17. The structure of claim 16, wherein said chuck plate comprises a rectangular shape.

18. The structure of claim 16, wherein said pad structure comprises a rectangular shape.

19. The structure of claim 16, wherein said glass mold comprises a rectangular shape.

20. The structure of claim 16, wherein said glass mold comprises a plurality structures formed from portions of said top surface, wherein each structure of said plurality of structures is raised above all other portions of said top surface of said glass mold and forms a perimeter around an associated cavity of said plurality of cavities, and wherein said polishing tool is configured to remove said plurality of structures.

21. The structure of claim 16, wherein said glass mold comprises sharp corners formed at a junction between said top surface of said glass mold and side surfaces of said cavities, and wherein said polishing tool is configured to remove said sharp corners resulting in rounded corners formed between said top surface of said glass mold and said side surfaces of said cavities.

22. The structure of claim 16, wherein said retaining structure comprises a plurality of retaining rails, and wherein each retaining rail of said plurality of retaining rails is mechanically attached to said chuck plate.

23. The structure of claim 16, wherein said first motor assembly is configured to rotate said polishing pad a second speed differing from said first speed and in a second direction differing from said first direction.