Wrapping pad

Abstract

The present invention provides a lapping pad that can lap hard and brittle substrates at a high polishing rate, and that allows the lapped substrate to have a low surface roughness. [Solution] A wrapping pad comprising a wrapping layer containing a novolac-type vinyl ester resin, a curing agent, and a curing accelerator.

Description

Technical Field

[0001] The present invention relates to a lapping pad.

Background Art

[0002] In recent years, as next-generation power semiconductor device materials, materials such as silicon carbide (SiC), gallium nitride (GaN), diamond, sapphire (Al2O3), and silicon nitride (Si3N4), which are wide-bandgap semiconductors, have been attracting attention. For example, a silicon nitride wiring board with a wiring circuit pattern formed on its surface and a metal foil or metal plate joined thereto has high thermal conductivity and is also excellent in mechanical strength, fracture toughness, and heat fatigue resistance. Therefore, silicon nitride wiring boards have recently attracted attention as wiring boards used in power semiconductor modules that perform power conversion and control with high efficiency in fields related to motor drive control of electric vehicles and electric railways, as well as renewable energy such as solar power generation. Materials such as the above-mentioned silicon nitride and sapphire have excellent mechanical strength and are difficult to grind. Although grinding wheels and abrasive grains with high hardness such as diamond and CBN (cubic boron nitride) are used for grinding, there is room for improvement in their processing efficiency and processing speed.

[0003] For example, Patent Document 1 discloses a lapping device including a rotatable polishing plate, the polishing plate having a polishing surface against which a substrate is pressed, and at least a portion of the polishing plate facing the polishing surface being formed of iron with a purity of 99.95% or more. In the lapping device, it is described in Patent Document 1 that a substrate formed of a hard material such as SiC or sapphire can be favorably lapped by using an iron surface plate compatible with diamond abrasive grains.

[0004] Furthermore, Patent Document 2 discloses a polishing plate for a polishing machine that performs lapping polishing with abrasive grains, characterized in that the working surface of the polishing plate is a porous body of thermosetting resin having continuous pores with a porosity of 30 to 70 volume%, and fine powder of copper or tin is dispersed and fixed thereon. Patent Document 2 states that with this polishing plate, the plate has excellent affinity for diamond abrasive grains, and the abrasive grains fixed to the plate can polish the workpiece with high shear force, so that the hard and brittle substrate after processing can have a low surface roughness. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2004-082224 [Patent Document 2] Special Publication No. 6-73807 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the inventors investigated and found that in the iron surface plate described in Patent Document 1, a chemical reaction occurs between the diamond abrasive grains and the iron surface plate, causing the cutting edge of the diamond abrasive grains to become dull and reducing the cutting performance, thus lowering the polishing rate.

[0007] Furthermore, in the polishing plate described in Patent Document 2, diamond abrasive grains are fixed to fine powder for polishing, but it was found that the fixed diamond abrasive grains deteriorate over time, reducing the polishing performance. It was also found that in the polishing plate described in Patent Document 2, each time a slurry containing diamond abrasive grains is added, the amount of fixed diamond abrasive grains increases, increasing the number of polishing points, which disperses the polishing stress and reduces the polishing rate.

[0008] The present invention has been made in view of the above-mentioned problems, and aims to provide a lapping pad that can lap hard and brittle substrates at a high polishing rate, and that allows the substrate to have low surface roughness after lapping. [Means for solving the problem]

[0009] The inventors of the present invention diligently studied to solve the above problems and found that the above problems can be solved by using a specific wrapping layer containing a novolac-type vinyl ester resin, thus completing the present invention.

[0010] In other words, the present invention is as follows: [1] A wrapping layer comprising a novolac-type vinyl ester resin, a curing agent, and a curing accelerator, Wrapping pad. [2] In the wrapping layer, the proportion of amorphous components measured by pulsed NMR at 40°C is 2% or less of the total amount of the wrapping layer. [1] Wrapping pad as described above. [3] In the wrapping layer, the proportion of the crystalline phase component measured by pulsed NMR at 40°C is 55% or more and 70% or less of the total amount of the wrapping layer. The wrapping pad described in [1] or [2]. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a lapping pad that can lap hard and brittle substrates at a high polishing rate, and that allows the substrate to have low surface roughness after lapping. [Modes for carrying out the invention]

[0012] The following describes in detail an embodiment of the present invention (hereinafter referred to as "this embodiment"), but the present invention is not limited thereto, and various modifications are possible without departing from its spirit.

[0013] 1. Wrapping pad The wrapping pad of this embodiment (hereinafter also simply referred to as "the pad") comprises a wrapping layer containing a novolac-type vinyl ester resin, a curing agent, and a curing accelerator. The wrapping pad of this embodiment only needs to have the above-mentioned wrapping layer, and may optionally include a base layer, an adhesive layer, and the like.

[0014] 1.1. Wrapping layer In this embodiment, the lapping layer is a layer for lapping, and is a layer having a lapping surface that is pressed against the workpiece during lapping. Preferably, the lapping layer has a convex portion on its upper surface and a base portion provided below the convex portion, more preferably the convex portion and base portion of the lapping layer are integrally molded from the same resin, and even more preferably a fibrous material is embedded in the resin of the base portion. In the lapping layer, it is preferable that the recesses formed between the multiple convex portions form grooves. The presence of such grooves makes it easier for slurry to be supplied to the polishing surface when slurry is used, and also tends to make it easier to discharge polishing debris.

[0015] In this embodiment, the lapping layer comprises a novolac-type vinyl ester resin, a curing agent, and a curing accelerator. By having such a lapping layer, the lapping pad of this embodiment can lap hard and brittle substrates at a high polishing rate, and the substrate after lapping can have a low surface roughness. Although the exact reasons are not clear, they are thought to be as follows. That is, because the novolac-type vinyl ester resin has a dense three-dimensional crosslinking structure, the hardness of the lapping layer tends to increase, and as a result, the polishing rate is thought to improve. Also, when using diamond abrasive grains, the novolac-type vinyl ester resin, which has abundant carbon-carbon bonds, has a high affinity for diamond, which is composed only of covalent bonds between carbon atoms, and therefore has a high ability to hold diamond abrasive grains. Therefore, a large number of diamond abrasive grains can be held on the upper surface of the lapping layer, there are many contact points between the abrasive grains and the workpiece during polishing, the load on each abrasive grain is reduced, and the substrate after lapping can have a low surface roughness. However, the factors are not limited to those mentioned above. Examples of materials for the hard and brittle substrate include silicon nitride, silicon carbide, aluminum nitride, gallium nitride, gallium arsenide, and sapphire.

[0016] The D hardness of the lapping layer is preferably between 70° and 100°, more preferably between 75° and 90°, and even more preferably between 80° and 85°. When the D hardness of the lapping layer is within the above range, the polishing rate tends to improve while maintaining a low level of surface roughness. The D hardness can be measured using a D-type hardness tester in accordance with JIS-K-6253 (2012).

[0017] The thickness of the lapping layer is preferably 0.3 mm to 10.0 mm, more preferably 0.5 mm to 5.0 mm, and even more preferably 0.7 mm to 3.0 mm. When the thickness of the lapping layer is within the above range, the polishing rate tends to improve.

[0018] 1.1.1. Novolac-type vinyl ester resin The wrapping layer in this embodiment contains a novolak-type vinyl ester resin. Since the novolak-type vinyl ester resin has a dense three-dimensional crosslinked structure, the hardness of the wrapping layer tends to be high. As a result, it is considered that the polishing rate is improved. Further, when using diamond abrasive grains, the novolak-type vinyl ester resin having abundant carbon-carbon bonds has a high affinity with diamond composed only of covalent bonds of carbon atoms, and thus has a high ability to hold diamond abrasive grains. Therefore, it is possible to suppress the aggregation of diamond abrasive grains and their contact with the workpiece as coarse abrasive grains, and the substrate after lapping can have a low surface roughness.

[0019] The novolak-type vinyl ester resin in this embodiment is a vinyl ester resin having a novolak skeleton, and is, for example, a resin having a repeating unit represented by the following formula (1).

[0020]

Chemical formula

[0021] In the above formula, n is the number of repetitions of the unit, and represents an integer of 1 to 10, preferably 1 to 6. R1 and R2 each independently represent a hydrogen atom or a methyl group.

[0022] The novolak skeleton is a skeleton having a structure in which a large number of phenol molecules are bonded by methylene groups. A resin having a novolak skeleton can be obtained, for example, by reacting phenol and formaldehyde under an acid catalyst and then curing with a curing agent.

[0023] The vinyl ester resin is a resin having a structure in which a vinyl group and an ester group are bonded. The vinyl ester resin can be obtained, for example, by an addition reaction of an epoxy resin and acrylic acid.

[0024] Novolac-type vinyl ester resins can be manufactured using known methods or are commercially available. When the novolac-type vinyl ester resin is a phenol novolac-type vinyl ester resin, examples of its manufacturing methods include the following: First, phenol and formaldehyde are reacted under an acid catalyst, and then cured with a curing agent to obtain a phenol novolac resin. Next, the phenol novolac resin is reacted with epichlorohydrin or the like to introduce epoxy groups and obtain a phenol novolac-type epoxy resin. The phenol novolac-type epoxy resin is then reacted with acrylic acid to obtain a phenol novolac-type vinyl ester resin.

[0025] Examples of novolac-type vinyl ester resins include phenol novolac-type vinyl ester resins and cresol novolac-type vinyl ester resins. Novolac-type vinyl ester resins can be used individually or in combination of two or more types.

[0026] Examples of commercially available novolac-type vinyl ester resins include Lipoxy H-600, Lipoxy H-630, Lipoxy H-610, and Lipoxy H-6008 (all product names) manufactured by Resonaq Corporation, and Neopol 8411L, Neopol 8411H, and Neopol 8450 (all product names) manufactured by Nippon Yupika Co., Ltd.

[0027] The number of vinyl ester groups in a novolac-type vinyl ester resin is not particularly limited, but it is preferable to have two or more. In this case, the hardness of the lapping layer tends to be further increased, and the polishing rate tends to improve even further. The novolac-type vinyl ester resin may also be monofunctional, meaning it may have only one vinyl ester group. There is no particular upper limit to the number of vinyl ester groups, but it may be, for example, 10.

[0028] In this embodiment, the weight-average molecular weight of the novolac-type vinyl ester resin is preferably 500 to 5000, more preferably 1000 to 4000, and even more preferably 1500 to 2000. When the weight-average molecular weight of the novolac-type vinyl ester resin falls within the above range, the hardness of the lapping layer tends to increase, and the polishing rate improves. The weight-average molecular weight can be calculated, for example, from the results of molecular weight measurement by gel permeation chromatography (GPC).

[0029] The content of novolac-type vinyl ester resin is preferably 70% to 99% by mass, more preferably 80% to 95% by mass, and even more preferably 85% to 93% by mass, based on 100% by mass of the total lapping layer. When the content of novolac-type vinyl ester resin is within the above range, the polishing rate tends to improve further.

[0030] When forming the wrapping layer, the novolac-type vinyl ester resin may be dissolved in a reactive monomer. In other words, the wrapping layer may be formed using a composition containing a novolac-type vinyl ester resin and a reactive monomer that dissolves it. The reactive monomer is not particularly limited as long as it dissolves the novolac-type vinyl ester resin and can be incorporated into the novolac-type vinyl ester resin as a constituent unit. Examples of reactive monomers include styrene, acrylic acid esters, and methacrylic acid esters.

[0031] The content of reactive monomers in the novolac-type vinyl ester resin is not particularly limited, but is preferably 20% by mass or more and 70% by mass or less, more preferably 25% by mass or more and 60% by mass or less, and even more preferably 30% by mass or more and 50% by mass or less. When the content of reactive monomers is within the above range, it is possible to suppress the decrease in workability due to the increase in viscosity of the composition containing the reactive monomer and the novolac-type vinyl ester resin, and it tends to be easier to obtain a lapins layer with the desired properties.

[0032] 1.1.2. Hardener In this embodiment, the lapping layer contains a curing agent. The inclusion of a curing agent in the lapping layer allows for efficient curing of the novolac-type vinyl ester resin, thereby improving the hardness of the lapping layer and enhancing the polishing rate. The curing agent is not particularly limited and can be any agent that cures the novolac-type vinyl ester resin. Examples of curing agents include organic peroxides. Examples of organic peroxides include dialkyl peroxides such as methyl ethyl ketone peroxide; diacyl peroxides, peroxydicarbonates, and benzoyl peroxides. The curing agent may be used alone or in combination of two or more.

[0033] The curing agent content is preferably 0.1 parts by mass to 5 parts by mass, more preferably 0.3 parts by mass to 3 parts by mass, and even more preferably 0.5 parts by mass to 2 parts by mass, per 100 parts by mass of novolac-type vinyl ester resin. When the curing agent content is within the above range, the polishing rate tends to improve further.

[0034] 1.1.3. Curing Accelerator In this embodiment, the wrapping layer contains a curing accelerator. The inclusion of a curing accelerator in the wrapping layer improves its hardness. The curing accelerator is not particularly limited and examples include metal salts such as cobalt octoate, cobalt naphthenate, and manganese naphthenate. Commercially available curing accelerators may also be used, such as Cobalt N (product name, manufactured by Resonaq Corporation). The curing accelerator may be used alone or in combination of two or more.

[0035] The content of the curing accelerator is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.05 parts by mass or more and 1 part by mass or less, and even more preferably 0.1 parts by mass or more and 0.7 parts by mass or less, per 100 parts by mass of novolac-type vinyl ester resin. When the content of the curing accelerator is within the above range, the polishing rate tends to improve further.

[0036] 1.1.4. Curing accelerators In this embodiment, the wrapping layer may contain a curing accelerator. The inclusion of a curing accelerator in the wrapping layer can improve its hardness. Examples of curing accelerators include amines such as aniline, diethanolaniline, p-toluidine, m-toluidine, N-ethyl-m-toluidine, triethanolamine, diethylenetriamine, pyridine, piperidine, phenylimorpholine, N,N-substituted aniline, N,N-substituted-p-toluidine, and 4-(N,N-substituted amino)benzaldehyde; and β-diketones such as acetylacetone, methyl acetoacetate, ethyl acetoacetate, acetylbutyllactone, and dimethylacetacetamide. Commercially available curing accelerators may also be used, such as accelerator D (product name, manufactured by Resonaq Corporation). The curing accelerator may be used individually or in combination of two or more.

[0037] The content of the curing accelerator is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.05 parts by mass or more and 1 part by mass or less, and even more preferably 0.1 parts by mass or more and 0.7 parts by mass or less, per 100 parts by mass of novolac-type vinyl ester resin. When the content of the curing accelerator is within the above range, the polishing rate tends to improve further.

[0038] 1.1.5. Curing retarder In this embodiment, the wrapping layer may contain a curing retarder. The curing retarder is not particularly limited, and examples include free radical-based curing retarders. More specifically, examples of curing retarders include TEMPO derivatives such as 2,2,6,6-tetramethylpiperidine-1-oxyl free radical (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical (TEMPOL), and 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl free radical (TEMPONE). Commercial curing retarders may also be used, such as curing retarder V (product name, manufactured by Resonaq Corporation). The curing retarder may be used alone or in combination of two or more.

[0039] The content of the curing retarder is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.03 parts by mass or more and 1 part by mass or less, and even more preferably 0.05 parts by mass or more and 0.5 parts by mass or less, per 100 parts by mass of novolac-type vinyl ester resin. When the content of the curing retarder is within the above range, the polishing rate tends to improve further.

[0040] 1.1.6. Textile Materials In this embodiment, the wrapping layer may include a fibrous material. Examples of the fibrous material's form include yarn, bundles, cotton, and cloth, with cloth being preferred among these. Examples of cloth-like fibrous materials include nonwoven fabrics, woven fabrics, and knitted fabrics, with woven fabrics and mesh fabrics being preferred from the viewpoint of increasing the strength of the resin, and mesh fabrics being more preferred. Examples of materials for the fibrous material include organic fibers, inorganic fibers, synthetic fibers, semi-synthetic fibers, and regenerated fibers. Examples of organic fibers include, but are not limited to, natural fiber-derived fibers such as cellulose, carbon fiber, pulp, chitin, and chitosan. Examples of inorganic fibers include, but are not limited to, glass fibers, rock fibers, and metal fibers. Examples of synthetic fibers include, but are not limited to, nylon, vinylon, vinylidene, polyester, polyolefin (e.g., polyethylene and polypropylene), polyurethane, acrylic, polyvinyl chloride, and aramid. Examples of semi-synthetic fibers include, but are not limited to, acetate, triacetate, and promix. Examples of regenerated fibers include, but are not limited to, rayon, cupro, polynosic rayon, lyocell, and Tencel. From the viewpoint of availability and ease of processing, polyethylene or polypropylene is preferred as the fiber material in this embodiment.

[0041] The fiber diameter of the fibrous material is preferably between 100 μm and 300 μm, and more preferably between 150 μm and 250 μm. When the fiber diameter of the fibrous material is within the above range, it can function as a skeletal material for the resin and increase the strength of the wrapping layer. Also, if the fiber diameter is 300 μm or less, it is easy for air to enter from the surroundings when incorporating the fibrous material into the resin.

[0042] The mesh size of the fiber material is preferably 10 μm to 700 μm, and more preferably 30 μm to 520 μm. By having a mesh size within the above range, the fiber material is properly incorporated into the wrapping layer, thereby increasing the strength of the wrapping layer. More specifically, if the mesh size is 10 μm or more, the resin adheres more easily to the fiber material, and if the mesh size is 700 μm or less, the fiber material functions more easily as a skeletal material, thereby increasing the strength of the wrapping layer.

[0043] When the fibrous material is in the form of a cloth, its thickness is preferably 100 μm to 500 μm, and more preferably 150 μm to 300 μm. By having the thickness of the fibrous material within the above range, the strength of the lapping layer can be increased without impairing the polishing performance as a lapping pad.

[0044] 1.2. Crystalline phase, intermediate layer, and amorphous phase of the lapping layer In this embodiment, the wrapping layer may be composed of a crystalline phase, an intermediate layer, and an amorphous phase. The relative abundances of these phases can be measured by pulsed NMR spectroscopy.

[0045] 1.2.1. Pulsed NMR Method Pulsed NMR is a type of solid-state NMR method that detects the response signal to a pulse and analyzes the sample. 1 This is a method for determining the H nuclear magnetic relaxation time (an indicator representing molecular mobility).

[0046] Pulsed NMR is an analytical method for evaluating the overall mobility of polymer molecular chains. Polymer mobility can be evaluated by measuring the relaxation time of the resin composition and the signal intensity at that time. Generally, the lower the mobility of the polymer chains, the shorter the relaxation time, so the signal intensity decays more quickly, and the relative signal intensity decreases in a short time when the initial signal intensity is set to 100%. Conversely, the higher the mobility of the polymer chains, the longer the relaxation time, so the signal intensity decays more slowly, and the relative signal intensity decreases gradually over a long period of time when the initial signal intensity is set to 100%.

[0047] For example, when a resin is measured as a sample, the resulting free induction decay (FID) signal is the sum of the FIDs of multiple components with different relaxation times. By separating the waveform of the obtained FID signal using the least squares method and approximating it as a three-component signal, it is possible to classify which component it originates from in the sample: the component with the lowest mobility (crystalline phase), the component with intermediate mobility (intermediate phase), or the component with the highest mobility (amorphous phase), and then determine the proportion of each component.

[0048] In this embodiment, the relaxation time and abundance of each component of the crystalline phase, interface phase, and amorphous phase in the wrapping layer can be measured using pulsed NMR as follows. First, a glass tube with a diameter of 1 cm is filled with a stack of disc-shaped samples punched to a size of 8 mm in diameter, to a height of 1.0 cm to 1.2 cm. The glass tube containing the samples is placed in a magnetic field, and the relaxation behavior of the macroscopic magnetization after applying a high-frequency pulsed magnetic field is measured to obtain a free induction decay (FID) signal (horizontal axis: time (m seconds), vertical axis: free induction decay signal). The initial value of the obtained FID signal is proportional to the number of protons in the sample, and if the sample has three components, the FID signal appears as the sum of the response signals of the three components. On the other hand, since each component contained in the sample has a different mobility, the rate of decay of the response signal differs among the components, and the spin-spin relaxation time T2 differs. Therefore, it can be separated into three components by the least squares method, and in order from the longest spin-spin relaxation time T2, they become the amorphous phase, intermediate phase, and crystalline phase, respectively. The amorphous phase consists of components with high molecular mobility, the crystalline phase consists of components with low molecular mobility, and the intermediate phase consists of components in between. In this embodiment, the measurement is performed using the solid echo method.

[0049] After obtaining the FID signal, fitting is performed to separate the FID signal into signals for three components with different kinetics (crystalline phase component, interfacial phase component, and amorphous phase component). Using the analysis software "TD-NMR Analyzer" from BRUKER, the obtained relaxation curve is fitted according to the product manual using the following equation (2), and the ratio of each component and the relaxation time are determined from the curve derived from the three components obtained by measurement. In this embodiment, the fitting is performed with the Weibull coefficients set to W(1)=2.0, W(2)=1.0, and W(3)=1.0, starting from the shortest relaxation time T2. In this specification, the abundance ratios of each component of the crystalline phase, intermediate phase, and amorphous phase are shown as the ratio when the total abundance ratio of the three components is set to 100%.

[0050]

number

[0051] In the equation, I(t) represents the fitting strength at time t, T2(n) represents the spin-spin relaxation time of the nth component, A(n) represents the relative abundance of the component with relaxation time T2(n), and W(n) represents the Weibull coefficient of the nth component.

[0052] In this embodiment, the lapping layer preferably has an amorphous phase component content of 2.0% or less, more preferably 1.5% or less, and even more preferably 1.0% or less, as measured by pulsed NMR at 40°C. Such a lapping layer tends to have higher hardness and a further improved polishing rate. Furthermore, when the amorphous phase component content is low, the amount of reactive monomers that remain unreacted during the curing reaction tends to be lower. Therefore, changes in the physical properties of the lapping layer due to the evaporation of reactive monomers when using the pad or due to volatilization of reactive monomers over time can be further suppressed. Note that the amorphous phase component does not necessarily have to be included in the lapping layer, and its content may be 0% (below the detection limit).

[0053] In this embodiment, the lapping layer preferably has a crystalline phase component content of 55% to 70%, more preferably 60% to 69%, and even more preferably 65% ​​to 69%, as measured by pulsed NMR at 40°C. When the proportion of crystalline phase components is within the above range, the hardness of the lapping layer tends to be sufficiently high, and the polishing rate tends to improve further.

[0054] 1.2.2. Amount of residual reactive monomers

[0055] The wrapping layer may contain reactive monomers that remained unreacted during the curing reaction of the novolac-type vinyl ester resin described later (hereinafter, these reactive monomers will also be referred to as "residual monomers"). Since residual monomers are contained in the amorphous phase of the wrapping layer, there is a correlation between the amount of residual monomers and the proportion of amorphous phase components. During the curing reaction, the amount of residual monomers decreases, and the proportion of amorphous phase components also decreases. Therefore, it is considered that as the amount of residual monomers decreases, the amorphous phase components also decrease. Methods to reduce residual monomers include, for example, increasing the heating time or heating temperature in the heating process carried out after demolding the cured wrapping pad from the mold.

[0056] The amount of residual monomer in the lapping layer is preferably 0.01% to 2.0% by mass, more preferably 0.1% to 1.5% by mass, and even more preferably 0.3% to 1.2% by mass, based on 100% by mass of the entire lapping layer. Such a lapping layer tends to have higher hardness and a higher polishing rate. Furthermore, it is possible to further suppress changes in the physical properties of the lapping layer caused by the evaporation of residual monomer when using a pad or by the volatilization of residual monomer over time. The amount of residual monomer can be measured, for example, using a gas chromatograph-mass spectrometer (GC / MS).

[0057] 1.3. Base material layer The wrapping pad of this embodiment may include a base layer for forming a wrapping layer thereon. The material of the base layer is not particularly limited, but examples include thermoplastic resin films such as acrylic resin, vinyl resin, olefin resin, styrene resin, polyester resin, polycarbonate resin, and polyamide resin, as well as nonwoven fabrics.

[0058] 1.4.Adhesive layer The lapping pad of this embodiment may have an adhesive layer on the side of the base layer opposite to the lapping layer. The adhesive layer is provided to adhere the lapping pad, for example, to the polishing platen of a polishing machine.

[0059] The adhesive layer material is not particularly limited and can include various thermoplastic adhesives such as acrylic adhesives, nitrile adhesives, nitrile rubber adhesives, polyamide adhesives, polyurethane adhesives, polyester adhesives, and silicone adhesives. The adhesive layer may also be in the form of, for example, double-sided tape.

[0060] 2. Method for manufacturing wrapping pads The wrapping pad of this embodiment can be manufactured, for example, as follows: First, a novolac-type vinyl ester resin, a curing agent, and a curing accelerator are mixed to obtain a resin composition. At this time, a curing accelerator or curing retarder may also be mixed in.

[0061] Next, the obtained resin composition is molded. Specifically, the resin composition is first poured into an intaglio plate on which a relief pattern has been formed. Before the resin composition hardens, a sheet-like fibrous material is embedded in the resin composition, and then the resin composition is hardened. The hardened resin is then peeled off the intaglio plate to obtain a lapping layer. The obtained lapping layer has a relief pattern transferred from the intaglio plate, and the raised surfaces of the relief pattern become the lapping surface for lapping the workpiece.

[0062] Examples of intaglio plates for forming the wrapping layer include molds having an uneven pattern, intaglio plates made of photosensitive resin, intaglio plates made of rubber-based materials such as silicone rubber, and intaglio plates made of plastic materials. They are not particularly limited as long as a wrapping layer with protrusions formed on its upper surface can be obtained.

[0063] The process may include a step of applying a release agent to the intaglio plate before pouring the resin composition into the plate. The release agent is not particularly limited as long as it can peel off the hardened resin from the intaglio plate, and examples include silicone-based release agents and fluorine-based release agents, with fluorine-based release agents being preferred. The method of applying the release agent is not particularly limited as long as it can peel off the hardened resin from the intaglio plate, and examples include spraying and electrostatic coating, with spraying being preferred.

[0064] The method for pouring the resin composition into the intaglio plate is not particularly limited as long as the resin composition is filled (poured) into the recesses of the intaglio plate. Examples include gravity casting, in which the resin composition is poured into the recesses by its own weight at room temperature and pressure, and vacuum casting, in which the intaglio plate and the resin composition are placed in a vacuum container, the pressure is reduced, and the resin composition is poured into the recesses at atmospheric pressure.

[0065] When the wrapping layer comprises a convex portion and a base portion, it is preferable to pour the resin composition not only into the concave portion of the intaglio plate, but also to pour it to an extent that exceeds the height of the convex portion of the intaglio plate, thereby forming the base portion.

[0066] The method for embedding a sheet-like fibrous material into a resin composition before the resin composition hardens is not particularly limited as long as the fibrous material can be embedded into the resin composition. For example, one method involves placing the fibrous material on the base side and embedding it by applying its own weight or pressure.

[0067] The positional relationship between the fiber material and the intaglio plate can be adjusted as needed, such as so that the fiber material is in contact with the intaglio plate's relief pattern, and the fiber material can be positioned as desired.

[0068] The step of embedding the fiber material in the resin composition may be provided during or after the process of pouring the resin composition into the intaglio plate. This embedding step may be appropriately selected depending on the resin composition used, the fiber material, and the positional relationship between the fiber material and the intaglio plate. For example, if the fiber material has an open mesh like a mesh fabric, the fiber material may be placed in the intaglio plate first, and then the resin composition may be poured into the intaglio plate.

[0069] Furthermore, after embedding the fiber material in the resin composition, and before curing the resin composition, the process may further include a step of bonding a base layer to the side of the resin composition opposite to the side in contact with the intaglio plate. By using a base layer, the resin composition can be cured while sandwiched between the base layer and the intaglio plate. As a result, the uniformity of the thickness of the resulting molded body tends to improve, as does the flatness of the back surface of the molded body (the side opposite to the side in contact with the intaglio plate).

[0070] The method for curing the resin composition is not particularly limited as long as it is suitable for each resin composition, but examples include leaving it at room temperature or a heat curing method. After peeling the cured resin composition from the intaglio plate, the molded body may be heated in a dryer.

[0071] When heating the molded body removed from the intaglio plate, the heating temperature is preferably 70°C to 100°C, more preferably 75°C to 95°C, and even more preferably 80°C to 90°C. The heating time is preferably 1 hour to 14 hours, more preferably 4 hours to 12 hours, and even more preferably 7 hours to 11 hours. When the heating temperature and heating time for heating the lapping layer are within the above ranges, the proportion of amorphous components can be reduced more sufficiently, and the occurrence of warping of the lapping layer tends to be further suppressed.

[0072] After molding, if necessary, a base layer is bonded to the back surface of the wrapping layer (the surface opposite to the surface that was in contact with the intaglio plate), and then double-sided tape is applied to one side of the base layer to form an adhesive layer. The wrapping pad of this embodiment can then be obtained by cutting it into a predetermined shape, preferably a disc shape. [Examples]

[0073] The present invention will be described more specifically below with reference to examples and comparative examples. The present invention is not limited in any way by the following examples.

[0074] (Example 1) A resin composition was obtained by mixing 100 parts by mass of Lipoxy H630 (a novolac-type vinyl ester resin dissolved in styrene, with a styrene content of 40% by mass, a product name of Resonaq Corporation), 1.5 parts by mass of methyl ethyl ketone peroxide as a curing agent, 0.5 parts by mass of cobalt N (a product name of Resonaq Corporation, cobalt naphthenate solution) as a curing accelerator, 0.5 parts by mass of accelerator D (a product name of Resonaq Corporation, N,N-dimethylaniline-styrene solution) as a curing co-accelerator, and 1 part by mass of pigment in a container with a glass rod. The mixture was then poured into a polypropylene resin intaglio plate with a depth of 1 mm, in which square truncated pyramidal recesses were arranged at equal intervals when viewed from above. The dimensions of the recesses were 5.0 mm x 5.0 mm at the opening and 1 mm deep, with a spacing of 2 mm between adjacent recesses in the vertical and horizontal directions. Before curing, a mesh fabric made of polyethylene with a fiber diameter of 150 μm, a mesh opening of 30 μm, and a thickness of 300 μm was embedded in the resin composition from above, so that the fiber material would penetrate the base portion. The resin composition was cured at room temperature (25°C) for 30 minutes to obtain a molded body. After removing the molded body from the intaglio plate, it was heated in a dryer at 80°C for 9 hours. The heated molded body was cut into a circle with a diameter of 380 mm to obtain a wrapping layer with a thickness of 1.56 mm. A 1 mm thick acrylic resin, which served as the base layer, was bonded to the opposite side of the uneven surface of the wrapping layer via double-sided tape as the adhesive layer. Then, double-sided tape for attaching to a surface plate was bonded to the side of the base layer that did not have the wrapping layer bonded to it, to obtain a wrapping pad.

[0075] (Example 2) A lapping pad was obtained in the same manner as in Example 1, except that the heating temperature of the molded body removed from the intaglio plate was changed from 80°C to 90°C.

[0076] (Comparative Example 1) A lapping pad was obtained in the same manner as in Example 1, except that the molded body removed from the intaglio plate was not heated.

[0077] (Comparative Example 2) A prepolymer with an isocyanate group equivalent of 460 was synthesized by mixing polytetramethylene ether glycol, which has a number-average molecular weight of approximately 1000, with 2,4-tolylene diisocyanate. Separately, crude 3,3'-dichloro-4,4'-diaminodiphenylmethane (crude MOCA) was dissolved in polypropylene glycol at room temperature in a mass ratio of 1:1 to obtain a crude MOCA solution. Next, the prepolymer and the crude MOCA solution were thoroughly mixed in a mass ratio of prepolymer to crude MOCA of prepolymer:crude MOCA = 36:13 to obtain a mixture. The obtained mixture was poured into a mold (size: 1200mm × 1200mm × 20mm) with a rectangular internal space and an open top, and allowed to cure. The formed thermosetting polyurethane molded body was removed from the mold and sliced ​​to a thickness of 2.00mm. Next, the thermosetting polyurethane molded body after slicing was cut into a circular planar shape with a diameter of 960 mm. Then, using a cutting tool, grooves with a width of 1 mm, a depth of 1 mm, and a pitch of 1 mm were formed on the surface of the cut thermosetting polyurethane molded body, with a planar shape that was spiral and a cross-sectional shape that was V-shaped, thereby obtaining a lapping pad.

[0078] [Amount of residual monomers] Using pyrolysis GC / MS, the styrene content, which is a residual monomer, in the samples prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was analyzed and quantified under the following conditions.

[0079] First, 0.5 g of the sample, obtained by shredding and grinding the wrapping layer, was added to 5 mL of ethanol and allowed to stand for 3 days to obtain a dispersion. Next, the dispersion was heated in a bead bath using aluminum beads at 40°C for 5 hours, with occasional shaking, and the supernatant was filtered through a PTFE membrane filter to obtain an extract. 1 μL of the extract was measured using a microsyringe and added to a pyrolysis GC / MS for analysis. The measurement conditions were set as follows. The results are shown in Table 1. (Measurement conditions) Pyrolysis unit: EGA / PY-3030D (product name manufactured by Frontier Lab Co., Ltd.) Measurement device: GCMS-QP2020NX (product name manufactured by Shimadzu Corporation) Thermal desorption conditions: 180℃ Column: Ultra ALLOY-5 (product name manufactured by Shimadzu GLC Co., Ltd., size: 30m x 0.25mm x 0.25μm) Column temperature: 40°C (5 min hold) → (10°C / min) → 150°C (5 min hold) Carrier gas: He 36.7 (cm / s) MS detector: Ionization method; EI (70 eV), 200°C, scan range (m / z); 29-500 Split ratio: 100 Quantitative standard: Styrene

[0080] [Proportion of crystalline, amorphous, and intermediate phases] The lapping pads from Example 1 and Comparative Examples 1 and 2 were punched out with a circular punch to a diameter of 8 mm to prepare disc-shaped samples. These disc-shaped samples were stacked to a height of 1.0 cm to 1.2 cm in a 10 mmφ pulsed NMR sample tube and kept in a constant temperature and humidity chamber at 25°C and 50% relative humidity for 48 hours to obtain pulsed NMR measurement samples.

[0081] The obtained sample was used for structural analysis by pulsed NMR under the following measurement conditions. (Measurement conditions) Pulsed NMR spectrometer: Minispec mq20 (Bruker brand name) Measurement method: Solid echo method Total number of times: 128 Cumulative measurement interval: 0.5s Repeat time: 4.0s Measurement temperature: 40℃

[0082] Using Bruker's analysis software (product name: TD-NMR Analyzer), the relaxation curves obtained were fitted according to the product manual and equation (2) above to determine the relative abundances of crystalline, intermediate, and amorphous phases in the lapping layer. In this embodiment, the fitting was performed with the Weibull coefficients set to W(1)=2.0, W(2)=1.0, and W(3)=1.0, starting from the shortest relaxation time. The results are shown in Table 1.

[0083] [Measurement of contraction rate] Samples were prepared by cutting the molded bodies removed from the intaglio plate during the manufacturing process of Example 1 and Comparative Example 1 into 500 mm squares. These samples were heated in the same manner as in Example 1 and Comparative Example 1 using a drying oven. After heating, the lengths of the four sides were measured, and the average of the four side lengths was divided by 500 mm to obtain the shrinkage rate (%). The results are shown in Table 1.

[0084] [D hardness measurement] Samples were prepared by cutting the lapping layers of molded Examples 1 and 2 and Comparative Examples 1 and 2 into 500 mm squares. The D hardness of each sample was measured using a Type D durometer hardness tester in accordance with the Japanese Industrial Standard (JIS-K-6253). The results are shown in Table 1.

[0085] [Polishing test] Polishing tests were performed on the lapping pads of Example 1 and Comparative Example 2 under the following polishing conditions, and the surface roughness and polishing rate after the test were measured. (polishing conditions) Testing machine: HT15 single-sided polishing machine (product name manufactured by High Technos Co., Ltd.) Dresser: #270 Metal Bond Diamond Dresser Grinding load: 600g / cm 2 Rotation speed: 60 rpm Slurry: PD1126L (product name manufactured by Kyoeisha Chemical Co., Ltd.) with 0.7% by mass of diamond abrasive particles (particle size 18 μm) added. Chiller: 25℃ Workpiece to be ground: Silicon nitride substrate (40mm x 40mm)

[0086] The amount of polishing was determined from the mass reduction of the silicon nitride substrate before and after polishing. The thickness removed by polishing was calculated from the polished area and specific gravity of the silicon nitride substrate, and the polishing rate was determined by dividing this by the polishing time. Furthermore, the surface roughness of the silicon nitride substrate after polishing was measured using a Zygo NewView 5010 optical interferometer (Canon product name). The results are shown in Table 2.

[0087] [Table 1]

[0088] In Comparative Example 1, where no heat treatment was performed after removal from the intaglio plate, there was no shrinkage associated with the heat treatment, but the proportion of amorphous phase components was high at approximately 11%, and a large amount of residual monomer, styrene, remained. In Examples 1 and 2, where heat treatment was performed, the proportion of amorphous phase components decreased, and the proportion of crystalline phase components increased. The amount of styrene was less than 2%, which is thought to be due to the decrease in styrene caused by volatilization and reactions associated with the heat treatment. Shrinkage due to the heat treatment was kept to less than 1%.

[0089] [Table 2]

[0090] In a polishing test of a silicon nitride substrate, the polishing rate when using the hard polyurethane pad in Comparative Example 2 was 0.4 μm / min, while the polishing rate when using the lapping pad in Example 1 was 4 μm / min. Despite the surface roughness being similar in both examples, the polishing rate in Example 1 was approximately 10 times higher than that of Comparative Example 2. It is believed that the novolac-type vinyl ester resin, which has a high carbon-carbon bond content, improved the retention of diamond abrasive grains, resulting in a higher polishing rate compared to the polyurethane pad. [Industrial applicability]

[0091] The lapping pad of the present invention has industrial applicability as a lapping pad suitable for lapping optical materials, semiconductor devices, glass substrates for hard disks, and difficult-to-machine materials such as sapphire substrates.

Claims

1. The wrapping layer comprises a novolac-type vinyl ester resin, a curing agent, and a curing accelerator. Wrapping pad.

2. In the aforementioned wrapping layer, the proportion of amorphous phase components, as measured by pulsed NMR at 40°C, is 2% or less of the total amount of the wrapping layer. The wrapping pad according to claim 1.

3. In the aforementioned wrapping layer, the proportion of the crystalline phase component, as measured by pulsed NMR at 40°C, is 55% to 70% of the total amount of the wrapping layer. The wrapping pad according to claim 1 or 2.

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