1. Field of the Invention
The present invention relates to a polishing pad and a method for making the same, and in particular, to a polishing pad having a fiber substrate and a method for making the same.
2. Description of the Related Art
The conventional polishing pad substantially can be divided into two types: a non-woven polishing pad and a separate foam polishing pad. The conventional non-woven polishing pad includes a plurality of fibers and a resin, and the polishing pad is manufactured by using a composite material of the fibers (such as velvet or suede) and the resin, or impregnating a non-woven fabric formed by the fibers in a thermoplastic polyurethane resin for wet coagulation to form a flexible sheet having high deformability formed. A disadvantage of the polishing pad is that the flexibility thereof may easily lead to poor planarization performance of its grinding surface, and the resin cannot uniformly enclose the fibers, that is, a portion of the fibers are not enclosed by the resin, resulting in that the overall strength is insufficient and the service life is shorter.
The conventional separate foam polishing pad includes a plurality of pores and a resin, and the polishing pad is manufactured by pouring the resin (generally a polymer foam of thermoplastic polyurethane) into a cylindrical mold, cooling the resin for coagulation, and then slicing the resin. The polishing pad has higher rigidity than the first conventional non-woven polishing pad, has separate pore structures, and is usually used for high planarization polishing. However, the major problem of the polishing pad is that since it is difficult to achieve uniform distribution of the concentration of the resin in the cylindrical mold, non-uniform temperature distribution at positions in the cylindrical mold during the molding process may lead to different sizes and non-uniform distribution of the pores, which are not easy to be controlled, and as a result, after the slicing process, the difference between the sizes of the pores on the sliced surface of the polishing pad becomes more significant. Moreover, the pores are not in communication with each other, and polishing slurry may not easily flow therebetween in use, and is apt to scratch a workpiece.
Therefore, it is necessary to provide an innovative and progressive polishing pad and a method for making the same, so as to solve the above problems.
The present invention provides a polishing pad having a grinding layer, the grinding layer including a plurality of fibers and a main body. The fibers cross each other to form a fiber substrate, and the fineness of the fibers is 0.001 den to 6 den. The main body is a foam and encloses the fibers, the main body has a plurality of first pores and a plurality of second pores, the first pores are communicated with each other, the second pores are independent from each other, and the size of the first pores is at least 5 times greater than the size of the second pores, wherein the hardness of the grinding layer is 30 to 90 shore D, and the compression ratio thereof is 1% to 10%.
The present invention further provides a method for making a polishing pad, including the following steps: (a) placing a fiber substrate in a mold, wherein the fiber substrate includes a plurality of fibers, and the fineness of the fibers is 0.001 den to 6 den; (b) injecting a foaming resin in the mold to permeate the fiber substrate and enclose the fibers, wherein the viscosity of the foaming resin is 2000 cps to 5000 cps; and (c) heating to cure the foaming resin, so as to form a grinding layer, the grinding layer including the fiber substrate and a main body, wherein the main body is a foam formed by curing the foaming resin and encloses the fibers, the main body has a plurality of first pores and a plurality of second pores, the first pores are communicated with each other, the second pores are independent from each other, and the size of the first pores is at least 5 times greater than the size of the second pores, wherein the hardness of the grinding layer is 30 to 90 shore D, and the compression ratio thereof is 1% to 10%.
In the present invention, the polishing pad has preferable rigidity and provides high planarization efficiency, which makes it difficult to scratch a polished workpiece, so that the polished workpiece has preferable surface quality, and has a longer service life. Besides, the polishing pad also has preferable stability and reproducibility in the manufacturing process.
The invention will be described according to the appended drawings in which:
The operation mode of the grinding device 1 is as follows. At first, the polishing workpiece 13 is placed on the adsorption sheet 12, and the polishing workpiece 13 is adsorbed by the adsorption sheet 12. Next, the upper base plate 14 and the lower base plate 11 rotate in opposite directions, and the upper base plate 14 is moved downward, so that a grinding surface 223 of the polishing pad 15 contacts a surface of the polishing workpiece 13, and the polishing workpiece 13 can be polished by means of continuous supplement of the grinding slurry 16 and the action of the polishing pad 15.
The main body 22 is a foam and encloses the fibers 21. In this embodiment, the main body 22 is a separate foam, which is a resin composition or copolymer, and the material thereof includes a first component and a second component. The first component is polyuisocyanate, and preferably, the polyuisocyanate is toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI). The second component is a foaming agent, and preferably, the foaming agent is polyol. Preferably, the material of the main body 22 further includes a cross-linking hardener, for accelerating hardening of the main body 22. The cross-linking hardener may be aliphatic amine, alicyclic amine, amide amine or dicyandiamide. The main body 22 has a plurality of first pores 221 and a plurality of second pores 222. The first pores 221 are communicated with each other, the second pores 222 are independent from each other, and the size of the first pores 221 is at least 5 times, preferably at least 10 times, greater than the size of the second pores 222. In this embodiment, the size of the first pores 221 is 1 to 3 mm, and the size of the second pores 222 is 100 to 300 μm. The first pores 221 are physical pores, which are naturally formed in a space located between the fibers 21 after the raw material of the main body 22 encloses the fibers 21, and the fibers 21 are not exposed in the first pores 221. That is, the first pores 221 are not pores formed by foaming or impregnation or other chemical processing means. The second pores 222 are foaming pores, which are formed through a foaming process of the raw material of the main body 22.
The hardness of the grinding layer 2 is 30 to 90 shore D, and preferably is 40 to 70 shore D. The compression ratio of the grinding layer 2 is 1% to 10%, and preferably is 2% to 5%. As shown in
In the present invention, the hardness and the strength (rigidity) of the grinding layer 2 are moderate, and thus the grinding surface 223 has preferable planarization performance, which makes it difficult to scratch the polishing workpiece 13, and has a longer service life.
Next, the fiber substrate 20 is placed in a mold 3. In this embodiment, the mold 3 is box-like, which has a length, a width and a depth.
Then, a foaming resin is provided. In this embodiment, the foaming resin is a resin composition or copolymer, and the material thereof includes a first component and a second component. The first component is polyuisocyanate, and preferably, the polyuisocyanate is toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI). The second component is a foaming agent, and preferably, the foaming agent is polyol. Preferably, the material of the foaming resin further includes a cross-linking hardener, for accelerating hardening of the foaming resin. The cross-linking hardener may be aliphatic amine, alicyclic amine, amide amine or dicyandiamide. In the meantime, raw materials (that is, the first component and the second component) of the foaming resin are mixed and stirred to form the foaming resin with a proper viscosity, and preferably, the viscosity of the foaming resin is 2000 cps to 5000 cps.
Referring to
Referring to
In this embodiment, the heating and curing process includes two stages: the first stage is a pre-aging step, and the second stage is a hardening and aging step. The pre-aging step is directly heating the foaming resin 34 and the fiber substrate 20 in the mold 3 to form the grinding layer 2. Next, the hardening and aging step is taking the grinding layer 2 out from the mold 3 and then placing the grinding layer 2 in an oven or an aging chamber for a long period of time, so as to make the property of the main body 22 (the foaming resin 34) more stable.
Referring to
Preferably, next, an adhesive layer 18 is pasted on the back surface of the grinding layer 2, so as to facilitate adhesion of the grinding layer 2 onto the upper base plate 14 (
Examples are given below to describe the present invention in detail, but it does not mean that the present invention is only limited to content disclosed in the examples.
First, a non-woven fiber substrate having a thickness of 5.0 mm is provided, whose weight is 950 g/m2 and density is 0.19 g/cm3. The material of fibers of the non-woven substrate is 100% of PET, and the fineness thereof is 1.50 den.
Next, the fiber substrate is placed in a mold, and in this embodiment, the length, the width and the depth of the mold are respectively 100 cm, 100 cm and 1 cm.
Then, diisocyanate (TDI component) with 78.00 wt % and an equivalent number of 200-450 and polyol with 22.00 wt % and an equivalent number of 50-250 are fully mixed to form a foaming resin. In the meantime, the foaming resin is mixed and stirred to form a polymer solution with viscosity of 2250 cps.
Next, the polymer solution of the foaming resin is injected into the mold to permeate the fiber substrate to enclose the fibers.
Then, a pre-aging step is performed, in which the foaming resin and the fiber substrate in the mold are directly heated to 70□, which is maintained for 60 minutes, so as to form the grinding layer. Next, a hardening and aging step is performed, in which the grinding layer is taken out from the mold and then placed in an aging chamber for 12 hours, wherein the temperature of the aging chamber is 70□. The hardness of the grinding layer in the example is 40 shore D, and the compression ratio thereof is 5.33%.
Next, a slicing step is performed, so as to expose a portion of fibers, and the grinding layer is cut into a plurality of portions of a desired size. Afterwards, an adhesive layer is pasted onto the back surface of the grinding layer.
First, a non-woven fiber substrate having a thickness of 4.5 mm is provided, whose weight is 675 g/m2 and density is 0.19 g/cm3. The material of fibers of the non-woven substrate is 60% of PET and 40% of Nylon, and the fineness thereof is 3.0 den.
Next, the fiber substrate is placed in a mold, and in this example, the length, the width and the depth of the mold are respectively 90 cm, 170 cm and 5 cm.
Then, diisocyanate (TDI component) with 74.20 wt % and an equivalent number of 200-450, a cross-linking hardener with 20.81 wt % and an equivalent number of 50-250 and polyol with 4.99 wt % and an equivalent number of 50-150 are fully mixed to form a foaming resin. In the meantime, the foaming resin is mixed and stirred to form a polymer solution with viscosity of 3600 cps.
Next, the polymer solution of the foaming resin is injected into the mold to permeate the fiber substrate to enclose the fibers.
Then, a pre-aging step is performed, in which the foaming resin and the fiber substrate in the mold are directly heated to 80□, which is maintained for 75 minutes, so as to form the grinding layer. Next, a hardening and aging step is performed, in which the grinding layer is taken out from the mold and then placed in an aging chamber for 14 hours, wherein the temperature of the aging chamber is 80□. The hardness of the grinding layer in the example is 45 shore D, and the compression ratio thereof is 2.42%.
Next, a slicing step is performed, so as to expose a portion of fibers, and the grinding layer is cut into a plurality of portions of a desired size. Afterwards, an adhesive layer is pasted onto the back surface of the grinding layer.
First, a non-woven fiber substrate having a thickness of 3.0 mm is provided, whose weight is 390 g/m2 and density is 0.13 g/cm3. The material of fibers of the non-woven substrate is 50% of PET and 50% of PP, and the fineness thereof is 2.5 den.
Next, the fiber substrate is placed in a mold, and in this embodiment, the length, the width and the depth of the mold are respectively 110 cm, 110 cm and 5 cm.
Then, diisocyanate (TDI component) with 68.90 wt % and an equivalent number of 200-450, aliphatic amine with 28.57 wt % and an equivalent number of 50-250 and polyol with 2.53 wt % and an equivalent number of 50-150 are fully mixed to form a foaming resin. In the meantime, the foaming resin is mixed and stirred to form a polymer solution with viscosity of 4400 cps.
Next, the polymer solution of the foaming resin is injected into the mold to permeate the fiber substrate to enclose the fibers.
Then, a pre-aging step is performed, in which the foaming resin and the fiber substrate in the mold are directly heated to 70□, which is maintained for 80 minutes, so as to form the grinding layer. Next, a hardening and aging step is performed, in which the grinding layer is taken out from the mold and then placed in an aging chamber for 16 hours, wherein the temperature of the aging chamber is 70□. The hardness of the grinding layer in the example is 50 shore D, and the compression ratio thereof is 1.36%.
Next, a slicing step is performed, so as to expose a portion of fibers, and the grinding layer is cut into a plurality of portions of a desired size. Afterwards, an adhesive layer is pasted onto the back surface of the grinding layer.
The above embodiments only describe the principle and the efficacies of the present invention, and are not used to limit the present invention. Therefore, modifications and variations of the embodiments made by persons skilled in the art do not depart from the spirit of the invention. The scope of the present invention should fall within the scope as defined in the appended claims.
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Number | Date | Country | |
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20150099439 A1 | Apr 2015 | US |