JP2004338064A - Abrasive belt, polishing device and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive belt with a long service life capable of performing flat and smooth polishing of a substrate surface while suppressing the formation of level difference on a polished surface and causing no warp. <P>SOLUTION: In this abrasive belt 1 brought into sliding contact with the substrate while rotating and traveling, to polish the surface of the substrate, an abrasive layer 6 for polishing the surface of the substrate is formed by applying paste formed by mixing cork 3, abrasive grains 4 and bonding resin 5, onto a belt base material 2 and drying it. With this abrasive belt 1, the cork 3 serves as a cushion to polish in soft finish without flaw in comparison with polishing with an abrasive belt having an abrasive layer only with abrasive grains. Furthermore, the mixed cork 3 allows the abrasive belt 1 to follow the unevenness on the substrate surface, which permits flat and smooth polishing over the whole substrate surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polishing belt, a polishing apparatus, and a polishing method for flattening a substrate for mounting electronic components, for example. More specifically, the present invention relates to a flattening technique for flattening a substrate using a polishing belt having a polishing layer formed by mixing cork in an adhesive resin containing abrasive grains.
[0002]
[Prior art]
In recent years, electronic devices such as mobile phones and notebook personal computers (notebook personal computers) have been required to be smaller and thinner. Accordingly, a printed wiring board mounted in a housing of an electronic device has been required to have a higher density with a larger number of wiring circuits on a small-sized substrate. To increase the density of the printed wiring board, an insulating layer is formed one layer at a time, a conductor pattern is created on the insulating layer, and the conductor patterns between each layer are connected to each other, so that multiple conductor layers are stacked. Generally, a method using a build-up method is used.
[0003]
When manufacturing a printed wiring board using the build-up method, it is necessary to print an insulating resin over the unevenness of the substrate surface on which the conductor pattern is formed by etching, and to planarize the insulating resin. For example, a mounting board formed by etching a copper foil by a subtractive method (a technique of forming a conductive portion of an electric circuit by masking with a photoresist or the like and partially removing the copper foil by corrosion with a chemical). The surface has irregularities of about 20 to 35 μm corresponding to the thickness of the copper foil. For this reason, an insulating resin is supplied to the surface of the substrate by screen printing or the like, the insulating resin is cured to fill the recesses, and the uneven insulating resin is polished by a polishing device to achieve flattening.
[0004]
As a polishing device, a polishing belt is hung between wheels arranged at predetermined intervals, the polishing belt is rotated, and the polishing belt is fixed on a fixed table with a pad attached to the tip of an air cylinder. There is used a so-called belt sander-type polishing apparatus that polishes by sliding contact with each other (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP 2001-138202 A (Pages 3 and 4; FIG. 1)
[0006]
[Problems to be solved by the invention]
However, in the belt sander method using the above-described polishing apparatus, since a substrate made of two types of substrates (resin and copper) having completely different properties is polished, it is different from polishing a single material such as wood. It is not easy to obtain a flat and smooth polished surface. In particular, since the printed wiring board is warped, the polishing belt does not follow the undulation of the substrate, and only the portion that comes into contact with the polishing belt is shaved, resulting in an uneven polishing surface.
[0007]
The belt sander method uses a pad formed by laminating a resin plate, rubber, or sponge, and covering the surface with a fluororesin sheet that also serves as lubrication. There are a roll method of pressing against a belt and a buff method of attaching a brush to a roll and pressing the brush against the surface of a substrate, for example.
[0008]
In the rubber roll method, a difference in polishing rate depending on the material is generated, and a step of tens of μ occurs at the boundary between the resin portion and the copper portion. In the buff method, although the occurrence of such a step is suppressed, the substrate is likely to be warped, and particularly a thin plate having a thickness of 200 μm or less is significantly warped.
[0009]
Therefore, the present invention has been made in view of such a problem, and it is difficult to generate a step on a polished surface, and there is no warpage, and a polishing method capable of polishing a substrate surface flatly and smoothly. It is an object to provide a belt, a polishing apparatus, and a polishing method.
[0010]
[Means for Solving the Problems]
The polishing belt of the present invention is characterized in that the polishing layer is formed by applying a paste obtained by mixing cork, abrasive grains and an adhesive resin on a belt base material and drying.
[0011]
According to the polishing belt of the present invention, since the polishing layer contains cork rich in elasticity, the cork serves as a cushion and is polished with a polishing belt having a polishing layer made of only abrasive grains. As a result, the surface is polished to a soft finish with less scratches.
[0012]
Further, according to the polishing belt of the present invention, since cork is mixed in the polishing layer, it is possible to follow the unevenness of the substrate surface to be polished and to polish the entire surface of the substrate. Furthermore, according to the polishing belt of the present invention, since the polishing layer is formed by applying and drying a paste in which cork is mixed in polishing abrasive grains, the proportion of cork exposed on the polishing layer surface is reduced. Therefore, the life of the polishing belt itself is extended.
[0013]
The polishing apparatus of the present invention is a polishing apparatus of a belt sander type having a driving mechanism for rotating and driving the polishing belt and pressing means for pressing the polishing belt against the substrate surface. As the polishing belt, a belt having a polishing layer formed by applying and drying a paste obtained by mixing cork, polishing abrasive grains, and an adhesive resin on a belt base material is used.
[0014]
According to the polishing apparatus of the present invention, when the substrate surface is polished with a polishing belt having a polishing layer in which cork is mixed, the polishing belt can follow irregularities on the substrate surface due to the elasticity of the cork, and the entire surface of the substrate surface can be polished. Polishing can be performed.
[0015]
In the polishing method of the present invention, when the surface of the substrate is polished and flattened by being brought into sliding contact with the substrate while pressing the rotating polishing belt against the substrate, cork, polishing abrasive grains, and an adhesive resin are mixed. The surface of the substrate is polished with a polishing belt having a polishing layer formed by applying and drying a paste on a belt substrate.
[0016]
According to the polishing method of the present invention, when a rotating polishing belt is pressed against a substrate and brought into sliding contact with the substrate to polish the substrate, a paste obtained by mixing cork in an adhesive resin containing abrasive grains is used as a belt base. Since the substrate surface is polished by the polishing layer formed by coating and drying on the material, cork serves as a cushion, and the substrate surface is polished to a soft finish without being damaged.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. In the present embodiment, the present invention is applied to a belt sander type polishing apparatus, a polishing belt used in the polishing apparatus, and a polishing method for polishing using the polishing belt.
[0018]
The present inventors have found that in polishing by a belt sander method, a polishing belt provided with a polishing layer formed by mixing elastic cork excellent in shock absorption performance and compression recovery performance together with polishing abrasive grains in an adhesive resin. It has been found that the use of the polishing belt allows the polishing belt to follow irregularities on the surface of the substrate to be polished, thereby achieving overall polishing, a soft finish without scratches, and improvement in the wear resistance of the polishing belt.
[0019]
[Polishing belt]
First, a polishing belt to which the present invention is applied will be described. As shown in FIG. 1, the polishing belt 1 of the present embodiment applies a paste obtained by mixing a cork 3, polishing abrasive grains 4, and an adhesive resin 5 on a belt base material 2 serving as a base and dry the paste. This is a structure in which the polishing layer 6 is formed.
[0020]
As the belt base material 2, for example, a cloth such as a campus ground is used. This belt base material 2 is formed as an elongated belt shape, and is an endless belt in which both ends in the longitudinal direction are joined.
[0021]
The polishing layer 6 is formed by applying a paste obtained by mixing the cork 3, the polishing abrasive grains 4, and the adhesive resin 5 on the belt base material 2 and then drying the paste for a predetermined time. It is preferable to use a cork 3 having a particle size of, for example, 250 μm or less. If the particle size of the cork 3 exceeds 250 μm, the proportion of the cork 3 exposed on the surface of the polishing layer 6 increases, and the wear resistance deteriorates. The lower limit of the particle size of the cork 3 is desirably, for example, 40 μm in consideration of the ability to follow irregularities on the substrate surface and the wear resistance. If the particle size of the cork 3 is less than 40 μm, the cork 3 becomes too fine, and the elastic action inherent in the cork is impaired, so that the polishing belt cannot follow irregularities on the substrate surface to be polished.
[0022]
The abrasive grains 4 vary depending on the base material to be polished. For example, when polishing resin and copper, it is preferable to use abrasive grains such as silicon carbide (SiC) and alumina. It is desirable that the particle size of the abrasive grains 4 is, for example, 40 to 20 μm (the roughness is # 400 to # 800). When the particle size of the abrasive grains 4 exceeds 40 μm, the rich elasticity of the cork 3 cannot be utilized, and polishing flaws increase, possibly leading to circuit cutting. If it is less than 20 μm, the wear of the cork 3 is accelerated, and the wear resistance is deteriorated.
[0023]
As the adhesive resin 5, a urethane resin or an epoxy resin is used. The abrasive layer 6 is formed by applying a paste made by mixing the cork 3 and the abrasive grains 4 to the adhesive resin 5 so as to have a predetermined thickness on the belt base material 2 and drying. .
[0024]
The volume ratio in which the adhesive resin 5, the cork 3, and the abrasive grains 4 are mixed is preferably, for example, 1: 3: 1. If the volume ratio is 1: 10: 1, the proportion of the cork 3 contained in the polishing layer 6 will increase, and the wear resistance will deteriorate, and only a part of the polishing abrasive grains 4 will be used for polishing. The abrasive grains 4 are not used and are wasted.
[0025]
The thickness of the polishing layer 6 is desirably, for example, about 0.4 to 0.6 mm. If the thickness of the polishing layer 6 exceeds 0.6 mm, the belt itself becomes hard and poorly copes with unevenness of the substrate. On the other hand, if the thickness of the polishing layer 6 is less than 0.4 mm, the durability of the belt becomes short.
[0026]
In order to manufacture the polishing belt 1 described above, for example, a mixed paste is prepared by mixing silicon carbide abrasive grains, cork grains having a particle size of 250 μm or less, and an adhesive resin. Then, the mixed paste is applied to one surface of a substrate cloth to be the belt substrate 2. Next, after the paste applied on the base cloth is dried, the paste is cut to a predetermined length when it is hardened. Then, the polishing layer 6 joins the ends of the belt base material 2 formed on the base cloth to form a belt shape.
[0027]
The polishing belt 1 has a width of 100 mm, a length of 2000 mm, and a thickness of 0.8 to 1.0 mm, for example. The size and thickness of the polishing belt 1 are merely examples, and the size and thickness are determined according to the size of the object to be polished.
[0028]
By the way, as described above, the paste obtained by mixing the cork 3 into the adhesive resin 5 containing the abrasive grains 4 is not used as the polishing layer 6, but as shown in FIG. After fixing with an adhesive 7 on the belt base material 2, an adhesive 8 is applied on the cork 3, and abrasive grains 9 are sprinkled thereon to use a polishing belt 10 formed to cover the surface of the cork 3. In this case, the wear resistance of the polishing belt 10 is significantly reduced for the following reasons.
[0029]
The abrasive belt 10 has a cork 3 having a particle diameter of about 1000 μm to 2000 μm (2 μm) as compared with, for example, abrasive silicon carbide (SiC) having a particle diameter of 40 μm to 20 μm (roughness is # 400 to # 800). Rin to Rin), which is several tens of times larger. In such a polishing belt 10, the polishing is performed by the abrasive abrasive grains 9 applied on the cork particles having a large particle diameter, and the cork 3 serves as a cushion so that the cork 3 is more scratched than the polishing belt using the abrasive alone. And a soft finish, and the entire surface of the substrate can be polished by following irregularities on the surface of the substrate, which is the material to be polished.
[0030]
However, since the cork 3 is a brittle material, it is chipped during polishing of the substrate 11 or its tip wears off, and as shown at 12a, 12b and 12c in FIG. The effect of the abrasive contributing to the contact with No. 11 is sharply reduced, and the cutting abrasive force is reduced. For this reason, in order to improve the polishing effect, when the polishing pressure is raised to 1.5 to 2 times the pad pressure of 40 to 70 gf / cm ² and the polishing belt 10 is pressed strongly against the substrate 11, the pad and the polishing belt 10 Due to the increase in friction, the fluororesin sheet on the pad is worn and easily broken. Further, in this polishing belt 10, since only a few% of the total abrasive is used for polishing, the efficiency is low and the life is short.
[0031]
As described above, in the polishing belt 10, the cork 3 having a small mechanical strength has a large particle size of about 0.5 × 1.5 mm on average, and a large one of about 3 mm. For this reason, in such a polishing belt 10, since the abrasive abrasive grains 9 on a part of the large cork surface protruding to the surface contribute to polishing because the sizes are not uniform, if the part is damaged or worn, it is resistant to polishing. Abrasion is reduced. Therefore, in the present embodiment, as described above, the cork 3 having a particle size of 250 μm or less is used while making the cork 3 having a large area difficult to appear on the surface and making use of the cushioning property and good followability of the cork 3. Was mixed in abrasive grains to achieve a long life.
[0032]
[Polishing device and polishing method]
Next, a polishing apparatus and a polishing method using the polishing belt 1 of the present embodiment will be described. FIG. 4 is a front view illustrating a schematic configuration of the polishing apparatus according to the present embodiment. This polishing apparatus is a polishing apparatus of a belt sander type, and includes a polishing belt 1, a driving mechanism for rotating and driving the polishing belt 1, and pressing means for pressing the polishing belt 1 against the surface of a substrate 11 to be polished. And fixing means for fixing the substrate 11.
[0033]
The drive mechanism has two holes 12 and 13 arranged at a predetermined interval, and a drive motor (not shown) which is a drive unit for driving one of the holes 12. An endless polishing belt 1 is hung between these two holes 12 and 13. The polishing belt 1 is rotatable in a direction indicated by an arrow A in FIG.
[0034]
The pressing means is arranged inside the polishing belt 1 hung in a ring shape, and a pad 14 that comes into contact with the back surface of the polishing belt 1 (the back surface 1 a opposite to the polishing layer 6), and the pad 14 is fixed to a predetermined position. An air cylinder 15 is pressed against the substrate 11 by pressure.
[0035]
The pad 14 has a structure in which a resin plate, rubber, sponge, or the like is laminated, and a fluororesin sheet is formed on the surface thereof, which also serves as lubrication to improve sliding with the substrate 11. The pad 14 is movable in the left-right direction along the polishing belt 1 as indicated by an arrow B in FIG.
[0036]
The pad 14 is fixed to the tip of the cylinder shaft 16 of the air cylinder 15. The air cylinder 15 pushes the pad 14 from the back surface 1 a of the polishing belt 1 against the substrate 11 at a predetermined pressure by advancing a cylinder shaft 16.
[0037]
The fixing means includes a table 17 for fixing the substrate 11 to the surface, and holding means (not shown) for positioning and holding the substrate 11 on the table 17. The table 17 is made of a base having a sufficient area for mounting the substrate 11, and has a certain period in the front-rear direction substantially perpendicular to the running direction of the polishing belt 1 so that a wide area can be polished. It is movable.
[0038]
The holding means comprises, for example, a vacuum chuck or the like, and countless small holes are formed on the table 17, and air is suctioned from the small holes by a vacuum device provided on the back surface of the table 17, so that the substrate 11 is placed on the table 17. Position and fix. Of course, other holding means can be used as the holding means instead of the vacuum chuck method.
[0039]
Next, a polishing method for polishing the surface of the substrate 11 using the above-described polishing apparatus will be described. Here, the surface (copper and insulating resin) of a printed wiring board obtained by printing an insulating resin over an electric circuit formed by etching copper is polished.
[0040]
First, the substrate 11 is fixed on the table 17 by a vacuum chuck. Then, the polishing belt 1 is caused to run by driving the drive motor to rotate the holes 12 and 13. Next, the air cylinder 15 is operated to project the cylinder shaft 16, and the pad 14 fixed to the tip of the cylinder shaft 16 is pressed from the back surface 1 a side of the polishing belt 1 to press the polishing belt 1 against the substrate 11.
[0041]
Then, the pad 14 is moved along the running direction of the polishing belt 1. Further, in order to polish the entire surface of the substrate 11 by the polishing belt 1, the table 17 is moved in the front-back direction substantially perpendicular to the running direction of the polishing belt 1.
[0042]
In this manner, the polishing belt 1 having the polishing layer 6 formed by applying and drying the paste obtained by mixing the cork 3, the polishing abrasive grains 4, and the adhesive resin 5 on the belt substrate 2, By polishing, the cork 3 serves as a cushion to provide a soft finish on the substrate surface, and the polishing belt 1 follows the unevenness of the substrate surface and is polished over the entire surface of the substrate. As a result, the obtained substrate 11 has a flat and smooth polished surface without unevenness over the entire surface.
[0043]
Further, in the present embodiment, since the polishing belt 1 follows irregularities on the surface of the substrate, it is not necessary to strongly press the pad 14 against the polishing belt 1, so that the life of the pad 14 can be greatly extended. Further, according to the present embodiment, since no extra force is applied to the polishing belt 1, the polishing operation can be performed stably.
[0044]
Further, in the present embodiment, since the particle size of the cork 3 is 250 μm or less, a large-area cork surface appearing on the surface of the polishing layer 6 can be reduced, and the life of the polishing belt 1 can be greatly extended. . In addition, in the polishing belt 1 of the present embodiment, the polishing is performed not with a part of the polishing agent but with the abrasive grains having a large area on the belt surface, so that the polishing life can be further extended. Become.
[0045]
Actually, the substrate 11 was polished under the following conditions. A polishing belt 1 formed by mixing # 400 SiC abrasive grains and a cork having a particle diameter of 180 μm as an adhesive is used. The polishing belt 1 is rotated at a peripheral speed of 360 m / min, and the polishing belt 1 using a pad 14 is rotated. Was set to 3 kgf, and a 200 μm thick double-sided epoxy substrate was polished.
[0046]
As a result, the epoxy double-sided board had no problem in any of the warpage, the step, and the polishing property, and the average roughness (Ra) was good at 0.2 μm.
[0047]
As described above, the specific embodiments to which the present invention is applied have been described. However, the present invention is not limited to the above-described embodiments, and can be variously modified.
[0048]
【The invention's effect】
According to the polishing belt of the present invention, since a polishing layer formed by applying and drying a paste obtained by mixing abrasive grains and cork with an adhesive resin on a belt base material, cork rich in elasticity acts as a cushion. In addition to making the polished surface a soft finish, the polished surface can be polished following the unevenness of the substrate surface, and a flat polished surface without unevenness can be formed.
[0049]
Further, according to the polishing belt of the present invention, since the cork is mixed evenly without exposing a large area cork surface on the surface of the polishing layer, it is possible to polish the entire polishing abrasive grains contained in the polishing layer, The polishing life can be greatly extended, and an improvement in wear resistance can be realized.
[0050]
According to the polishing apparatus of the present invention, a polishing belt having a polishing layer formed by applying a paste in which polishing abrasive grains and cork are mixed with an adhesive resin on a belt base material and drying is used, and the polishing belt is rotated. If the substrate is polished by running, the polishing belt follows the unevenness of the substrate surface due to the elasticity of the cork, so that the entire surface of the substrate can be polished smoothly without unevenness.
[0051]
According to the polishing method of the present invention, when the substrate is polished by sliding the polishing belt against the substrate while being pressed against the substrate, a paste in which polishing abrasive grains and cork are mixed with an adhesive resin is applied onto the belt substrate and dried. Since the surface of the substrate is polished by the formed polishing layer, the surface of the substrate can be made soft by the cushioning effect of cork, which is rich in elasticity.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view of a main part of a polishing belt to which the present invention is applied.
FIG. 2 is an enlarged cross-sectional view of a main part of a polishing belt formed by applying an adhesive onto a pulverized cork and sprinkling abrasive grains thereon.
FIG. 3 is an enlarged sectional view of a main part showing a state when a substrate is polished by the polishing belt of FIG. 2;
FIG. 4 is a front view showing a schematic configuration of a polishing apparatus to which the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Polishing belt 2 ... Belt base material 3 ... Cork 4 ... Polishing abrasive grains 5 ... Adhesive resin 6 ... Polishing layer 11 ... Substrate 14 ... Pad 15 ... Air cylinder 17 ... Table

Claims (4)

In a polishing belt that makes a rotating polishing belt slidably contact a substrate to polish and flatten the surface of the substrate,
A polishing belt, comprising: a polishing layer formed by applying and drying a paste obtained by mixing cork, polishing abrasive grains, and an adhesive resin on a belt base material. The polishing belt according to claim 1,
A polishing belt wherein the cork has a particle size of 250 μm or less. A polishing belt having a polishing layer formed by applying and drying a paste obtained by mixing a cork, abrasive grains and an adhesive resin on a belt base material,
A driving mechanism for rotating and driving the polishing belt,
A polishing device comprising: pressing means for pressing the polishing belt against a surface of a substrate to be polished. At the time of polishing and flattening the surface of the substrate by bringing the rotating polishing belt into sliding contact while pressing against the substrate,
A polishing method comprising polishing a surface of the substrate with a polishing belt having a polishing layer formed by applying and drying a paste obtained by mixing cork, polishing abrasive grains, and an adhesive resin on a belt substrate. .

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