Temporary protective material

Abstract

To provide a temporary protection material that has such water resistance as to protect a component mounting surface in a semiconductor substrate mounting step, and can be easily removed by hot water.SOLUTION: A temporary protection material, which is used as a protection material when a semiconductor is manufactured, contains a polyvinyl alcohol-based resin and a boric acid, wherein a content C (wt.%) of the boric acid in the temporary protection material satisfies the following expressions (1) and (2). In the expressions (1) and (2), A represents a degree of saponification (mol%) of a polyvinyl alcohol-based resin, B represents a weight average molecular weight of a polyvinyl alcohol-based resin, and C represents a content (wt.%) of the boric acid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a temporary protective material.

Background Art

[0002] When processing electronic components such as semiconductors, in order to facilitate handling of the electronic components and prevent them from being damaged, the electronic components are fixed to a support plate through an adhesive composition or an adhesive tape is attached to the electronic components for protection. For example, when a thick film wafer cut out from a high purity silicon single crystal or the like is ground to a predetermined thickness to form a thin film wafer, the thick film wafer is adhered to a support plate through an adhesive composition.

[0003] Thus, for the adhesive composition and adhesive tape used for electronic components, it is required to have a high adhesiveness capable of firmly fixing the electronic components during the processing step and being peeled off without damaging the electronic components after the step is completed (hereinafter, also referred to as "high adhesion and easy peeling"). As a means for realizing high adhesion and easy peeling, for example, in Patent Document 1, an adhesive is applied to the surface of a temporary holding substrate to form a temporary adhesive layer, and the semiconductor wafer is adhesively fixed by embedding the tip of the bump in the temporary adhesive layer, and then the temporary adhesive layer is dissolved with a solvent to detach the chip-type electronic component from the temporary holding substrate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, 3D mounting has been used in the assembly of electronic components to increase the density and improve the yield of integrated circuits. In 3D mounting, peripheral elements such as capacitors and solder balls are mounted on various surfaces of chip-type electronic components, including the top and back surfaces, in addition to the integrated circuit itself. In 3D packaging, due to process constraints, peripheral elements may be placed on the back side before integrated circuits are mounted on the top side. In such cases, when integrated circuits are mounted on the top side, the elements on the back side may come into contact with the stage, potentially causing scratches or damage to the chip-type electronic components. For this reason, protective sheets are used to protect the elements mounted on the back side first, but such protective sheets need to be removed after the integrated circuits are arranged in multiple layers on the front side. When removing them using organic solvents or other chemicals, as in Patent Document 1, there are problems such as increased environmental burden and the generation of protective sheet residue. Therefore, there is a need for a protective sheet that has sufficient water resistance to protect the component mounting surface during the semiconductor substrate mounting process, can be easily removed with hot water in the end, has a low environmental impact, and does not generate much residue.

[0006] The present invention aims to provide a temporary protective material that has water resistance to protect the component mounting surface during the semiconductor substrate mounting process and can be easily removed with hot water. [Means for solving the problem]

[0007] (1) of this disclosure is a temporary protective material used as a protective material during semiconductor manufacturing, which contains a polyvinyl alcohol-based resin and boric acid, and the content C (weight %) of the boric acid in the temporary protective material satisfies the following formulas (1) and (2). Disclosure (2) is the temporary protective material of Disclosure (1), wherein the boric acid content in the temporary protective material is 0.025% by weight or more and 15% by weight or less. Disclosure (3) is a temporary protective material according to Disclosure (1) or (2), wherein the degree of saponification of the polyvinyl alcohol-based resin is 70.0 mol% or more and 100 mol% or less. Disclosure (4) is a temporary protective material in any combination of any of Disclosures (1) to (3), wherein the weight-average molecular weight of the polyvinyl alcohol resin is 8,000 to 150,000. Disclosure (5) is a temporary protective material in any combination with any of Disclosures (1) to (4), wherein the gel fraction after heating is 70% by weight or more when ultrasonic vibration is applied in water at 35°C for 15 minutes. Disclosure (6) is a temporary protective material in any combination with any of Disclosures (1) to (5), wherein the gel fraction after heating is 5% by weight or less when immersed in water at 80°C for 15 minutes. Disclosure (7) is a temporary protective material in any combination with any of Disclosures (1) to (6), wherein the gel fraction is 70% by weight or more when ultrasonic vibration is applied to water at 35 degrees Celsius for 15 minutes after heating, and the gel fraction is 5% by weight or less when immersed in water at 80 degrees Celsius for 15 minutes after heating. The present invention will be described in detail below.

[0008]

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[0009]

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[0010] In formulas (1) and (2), A represents the degree of saponification of the polyvinyl alcohol resin (mol%), B represents the weight-average molecular weight of the polyvinyl alcohol resin, and C represents the boric acid content (weight%).

[0011] The inventors investigated a temporary protective material containing a polyvinyl alcohol-based resin and boric acid. The inventors found that by adjusting the content of boric acid in the temporary protective material to satisfy a predetermined relationship with respect to the degree of saponification and weight-average molecular weight of the polyvinyl alcohol-based resin, a temporary protective material with sufficient water resistance and heat resistance to protect the component mounting surface during the semiconductor substrate mounting process can be obtained. Furthermore, they found that such a temporary protective material can be easily removed with hot water without organic solvents, resulting in an environmentally friendly temporary protective material, thus completing the present invention.

[0012] The temporary protective material of the present invention contains a polyvinyl alcohol-based resin. By containing a polyvinyl alcohol-based resin, it can be made into a temporary protective material that can be easily removed with hot water.

[0013] The degree of saponification of the above polyvinyl alcohol-based resin is preferably 70.0 mol% or more, and preferably 100 mol% or less. By setting the range as described above, water resistance can be sufficiently enhanced. The degree of saponification is more preferably 80.0 mol% or more, even more preferably 85.0 mol% or more, particularly preferably 95.0 mol% or more, more preferably 99.5 mol% or less, and even more preferably 99.0 mol% or less. The degree of saponification described above can be measured, for example, by a method compliant with JIS K6726. The degree of saponification indicates the proportion of vinyl ester units that are actually converted to vinyl alcohol units out of the vinyl ester units that can be converted to vinyl alcohol units by saponification. The degree of saponification can be controlled, for example, by adjusting the saponification conditions, i.e., the hydrolysis conditions.

[0014] The weight-average molecular weight (Mw) of the above polyvinyl alcohol-based resin is preferably 8,000 or more, and preferably 150,000 or less. By setting it within the above range, high water resistance can be exhibited. Also, by appropriately selecting the type of crosslinking agent, easy solubility in warm water can be simultaneously achieved. The above weight-average molecular weight is more preferably 9000 or more, still more preferably 10000 or more, more preferably 100000 or less, still more preferably 50000 or less, and particularly preferably 40000 or less.

[0015] The number-average molecular weight (Mn) of the above polyvinyl alcohol-based resin is preferably 4000 or more, more preferably 4500 or more, still more preferably 5000 or more, preferably 90000 or less, more preferably 60000 or less, and still more preferably 30000 or less.

[0016] The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the above polyvinyl alcohol-based resin is preferably 1.2 or more, more preferably 1.4 or more, still more preferably 1.6 or more, preferably 5.0 or less, more preferably 3.5 or less, and still more preferably 2.0 or less. The above weight-average molecular weight (Mw) and number-average molecular weight (Mn) can be determined, for example, by measuring using the gel permeation chromatography (GPC) method, measuring the polyvinyl ester before saponification by the GPC method, measuring the polyvinyl ester obtained by re-esterifying the polyvinyl alcohol resin by the GPC method, measuring the viscosity of an aqueous solution in accordance with JIS K6726, etc. For example, polystyrene can be used as a standard, and columns such as TSKgel (manufactured by Tosoh Corporation), PLgel (manufactured by AMR Corporation), KF-806, KF-807 (manufactured by Shodex Corporation), etc. can be used.

[0017] The average degree of polymerization of the above polyvinyl alcohol-based resin is preferably 180 or more, more preferably 200 or more, still more preferably 220 or more, preferably 3400 or less, more preferably 2300 or less, still more preferably 1200 or less, and particularly preferably 700 or less. The average degree of polymerization can be determined, for example, by measuring the polyvinyl acetate resin before saponification by gel permeation chromatography (GPC) method or by measuring the viscosity of an aqueous solution in accordance with JIS K6726.

[0018] The above polyvinyl alcohol-based resin may be a modified polyvinyl alcohol-based resin having other constitutional units in addition to vinyl ester units and vinyl alcohol units. Examples of the above modified polyvinyl alcohol-based resin include those modified with a modifying group such as a hydrophilic group such as a sulfonic acid group, a pyrrolidone ring group, an amino group, a carboxyl group, etc. In addition to the above functional groups, these hydrophilic groups also include salts such as sodium salts and potassium salts thereof.

[0019] The content of the constitutional unit having a modifying group in the above polyvinyl alcohol-based resin is preferably 1 mol% or more, more preferably 3 mol% or more, particularly preferably 5 mol% or more, preferably 20 mol% or less, more preferably 15 mol% or less, and particularly preferably 12 mol% or less.

[0020] The content of the polyvinyl alcohol-based resin in the temporary protective material of the present invention is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 85% by weight or more. The upper limit of the polyvinyl alcohol-based resin content is not particularly limited, but can be explicitly determined by including other components such as storage stabilizers, mechanical property improvers, thickeners, preservatives, fungicides, dispersion stabilizers, spacers (gap adjusters), and other polymers, depending on the purpose. The upper limit is usually less than 100% by weight, but for example, 99.975% by weight or less is preferred, and 99.9% by weight or less is more preferred.

[0021] The above polyvinyl alcohol-based resin is obtained by polymerizing vinyl esters according to conventionally known methods, and then saponifying, i.e., hydrolyzing, the polymer. Generally, alkalis or acids are used as saponification catalysts.

[0022] Examples of the vinyl esters mentioned above include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, and vinyl benzoate.

[0023] The polymerization method for vinyl esters is not particularly limited, but examples include solution polymerization, bulk polymerization, and suspension polymerization.

[0024] Examples of polymerization catalysts used when polymerizing the above vinyl ester include 2-ethylhexyl peroxydicarbonate (Tianjin McEIT's "TrigonoxEHP"), 2,2'-azobisisobutyronitrile (AIBN), t-butyl peroxyneodecanoate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-n-propyl peroxydicarbonate, di-n-butyl peroxydicarbonate, di-cetyl peroxydicarbonate, and di-s-butyl peroxydicarbonate. Only one of these polymerization catalysts may be used, or two or more may be used in combination.

[0025] The above polyvinyl alcohol-based resin may be a saponified polymer of a vinyl ester and another unsaturated monomer. Other unsaturated monomers include monomers other than the vinyl esters mentioned above that have an unsaturated double bond such as a vinyl group. Specifically, examples include olefins, (meth)acrylic acid and its salts, (meth)acrylic acid esters, unsaturated acids other than (meth)acrylic acid, their salts and esters, (meth)acrylamides, N-vinylamides, vinyl ethers, nitriles, vinyl halides, allyl compounds, vinylsilyl compounds, isopropenyl acetate, sulfonic acid group-containing compounds, amino group-containing compounds, and the like.

[0026] Examples of olefins include ethylene, propylene, 1-butene, and isobutene. Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of unsaturated acids other than (meth)acrylic acid, their salts and esters include maleic acid and its salts, maleic acid esters, itaconic acid and its salts, itaconic acid esters, methylenemalonic acid and its salts, and methylenemalonic acid esters. Examples of (meth)acrylamides include acrylamide, n-methylacrylamide, N-ethylacrylamide, and N,N-dimethylacrylamide. Examples of N-vinylamides include N-vinylpyrrolidone. Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether. Examples of nitriles include (meth)acrylonitrile. Examples of vinyl halides include vinyl chloride and vinylidene chloride. Examples of allyl compounds include allyl acetate and allyl chloride. Examples of vinylsilyl compounds include vinyltrimethoxysilane. Examples of sulfonic acid group-containing compounds include (meth)acrylamide alkanesulfonic acids such as (meth)acrylamidepropanesulfonic acid and their salts, olefin sulfonic acids such as ethylenesulfonic acid, allylsulfonic acid, and metaallylsulfonic acid, and their salts. Examples of amino group-containing compounds include allylamine, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

[0027] The temporary protective material of the present invention contains boric acid. By including the above-mentioned boric acid, a cross-linked structure is formed in the polyvinyl alcohol-based resin upon heating, resulting in a temporary protective material with sufficient water resistance and heat resistance.

[0028] Examples of boric acid include orthoboric acid, metaboric acid, and tetraboric acid. Furthermore, the boric acid mentioned above also includes salts of boric acid. Examples of boric acid salts include borax, alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as calcium salt and magnesium salt, aluminum salt, and organic amine salts such as triethylamine, triethanolamine, morpholine, piperazine, and pyrrolidine. These boric acids may be used individually as a single word or in combination of two or more types.

[0029] The boric acid content in the temporary protective material of the present invention is preferably 0.025% by weight or more, and preferably 15% by weight or less. By setting the range as described above, sufficient water resistance and heat resistance can be imparted through heating. The boric acid content is more preferably 0.25% by weight or more, even more preferably 0.4% by weight or more, even more preferably 10% by weight or less, and even more preferably 5% by weight or less.

[0030] The boric acid content in the temporary protective material of the present invention is preferably 0.025 parts by weight or more, more preferably 0.25 parts by weight or more, even more preferably 0.4 parts by weight or more, preferably 17.6 parts by weight or less, more preferably 11.1 parts by weight or less, and even more preferably 5.3 parts by weight or less, per 100 parts by weight of the polyvinyl alcohol-based resin.

[0031] The boric acid content C (weight %) in the temporary protective material of the present invention satisfies the following formulas (1) and (2).

[0032]

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[0033]

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[0034] In formulas (1) and (2), A represents the degree of saponification of the polyvinyl alcohol resin (mol%), B represents the weight-average molecular weight of the polyvinyl alcohol resin, and C represents the boric acid content (weight%).

[0035] By satisfying the above equations (1) and (2), a temporary protective material can be made that has water resistance and heat resistance to protect the component mounting surface in the semiconductor substrate mounting process, and that can be easily removed with hot water.

[0036] The temporary protective material of the present invention may optionally contain other components such as storage stabilizers, mechanical property modifiers, thickeners, preservatives, fungicides, dispersion stabilizers, and spacers (gap adjusters), but it is preferably composed of a polyvinyl alcohol-based resin and boric acid.

[0037] The temporary protective material of the present invention preferably has a gel fraction of 70% by weight or more when ultrasonic vibration is applied to it in water at 35°C for 15 minutes after heating. When the gel fraction is 70% by weight or more, it can adequately perform its function of protecting the component mounting surface during the semiconductor substrate mounting process. The gel fraction described above is preferably 80% by weight or more, more preferably 90% by weight or more, and is usually 100% by weight or less. The heating conditions described above are preferably, for example, heating at 180°C for 30 minutes. Specifically, a method can be used in which the temporary protective material is left to stand in a hot air circulating oven at a temperature of 180°C for 30 minutes. The gel fraction described above can be determined, for example, by heating the temporary protective material of the present invention, which has been formed into a film, then immersing it in 35°C water and stirring it using an ultrasonic cleaner to dissolve it, and then measuring the weight of the undissolved components to calculate the ratio of the weight of the undissolved components to the weight of the temporary protective material before immersion. The frequency of the applied ultrasound is appropriately selected considering the cleaning performance and damage to the object being cleaned. 45kHz is one example. Lower frequencies improve cleaning power but increase the load on the object being cleaned, while higher frequencies slightly decrease cleaning power but reduce the load on the object being cleaned.

[0038] The temporary protective material of the present invention preferably has a gel fraction of 5% by weight or less when immersed in 80°C water for 15 minutes after heating. If the gel fraction is 5% by weight or less, the temporary protective material can be easily removed with warm water without using organic solvents. The gel fraction described above is more preferably 3.5% by weight or less, even more preferably 2% by weight or less, and is usually 0% by weight or more. The heating conditions described above are preferably, for example, heating at 180°C for 30 minutes. Specifically, a method can be used in which the temporary protective material is left to stand in a hot air circulating oven at a temperature of 180°C for 30 minutes. The above gel fraction can be determined, for example, by heating the temporary protective material of the present invention, which has been formed into a film, at 180°C for 30 minutes, then immersing it in water at 80°C for 15 minutes to dissolve it, and then measuring the weight of the undissolved component to calculate the ratio of the weight of the undissolved component to the weight of the temporary protective material before immersion.

[0039] The shape of the temporary protective material of the present invention is not particularly limited and can be in the form of a film, sheet, plate, powder, granules, flakes, pellets, etc.

[0040] The thickness of the temporary protective material of the present invention is not particularly limited, but is preferably 100 μm or more, more preferably 150 μm or more, even more preferably 200 μm or more, particularly preferably 300 μm or more, preferably 1000 μm or less, more preferably 700 μm or less, and even more preferably 500 μm or less. If the temporary protective material in this invention is too thick, the workability during bonding and ease of dissolution in hot water tend to decrease, and if it is too thin, the protrusions of the material to be protected will protrude, reducing the protective performance itself. Therefore, the thickness and shape of the temporary protective material of this invention are determined appropriately, taking into consideration the shape of the material to be protected, the size of the irregularities, etc.

[0041] The temporary protective material of the present invention preferably has a 90° peel force of 100 N / m or more, more preferably 200 N / m or more, and even more preferably 350 N / m or more, after being attached to a SUS plate and heated at 100°C for 30 minutes. The above 90° peeling force can be measured, for example, by the following method. First, the surface of a 25mm wide temporary protective material is lightly moistened with water, and then, under conditions of 23°C room temperature and 50% relative humidity, it is attached to a SUS plate at a speed of 10mm / sec using a 2kg pressure rubber roller. Next, a single heat treatment is performed at 100°C for 30 minutes. Here, the heat treatment at 100°C for 30 minutes refers to placing the sample to be measured in an oven below 100°C and leaving it undisturbed for 30 minutes. After cooling, the temporary protective material is peeled off at a speed of 5mm / min in accordance with JIS Z0237, and the peel force in the 90° direction is measured.

[0042] The method for manufacturing the temporary protective material of the present invention is not particularly limited, and examples include the following methods. First, an aqueous solution of polyvinyl alcohol-based resin and an aqueous solution of boric acid are prepared, and these are mixed so that the boric acid concentration is within a predetermined range to create a temporary protective material aqueous solution. Next, the temporary protective material aqueous solution is applied to the substrate and dried to produce the temporary protective material.

[0043] The materials constituting the above-mentioned base material are not particularly limited, but it is preferable that they be heat-resistant materials. Examples of heat-resistant materials include polyethylene terephthalate, polyethylene naphthalate, polyacetal, polyamide, polycarbonate, polyphenylene ether, polybutylene terephthalate, ultra-high molecular weight polyethylene, syndiotactic polystyrene, polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluororesin, and liquid crystal polymer. Since it is necessary to peel off the temporary protective material of the present invention after drying, it is preferable to apply a weak release treatment to the surface of the base material as needed.

[0044] Examples of the above coating methods include the casting method, roll coating method, lip coating method, spin coating method, screen coating method, fountain coating method, dipping method, and spray method.

[0045] Examples of the drying methods mentioned above include natural drying and heating and drying at a temperature at which no bubbles are generated due to solvent foaming, etc.

[0046] The thickness of the above-mentioned substrate is not particularly limited, but a preferred lower limit is 20 μm, and a more preferred lower limit is 25 μm. If the substrate is too thin, it will deform during heat drying, making it difficult to obtain a temporary protective material of a consistent thickness.

[0047] The applications of the temporary protective material of the present invention are not particularly limited, but it is preferable to use it in the manufacturing process of electronic components such as semiconductor devices and display devices. The temporary protective material of the present invention is less prone to peeling even at high temperatures during the semiconductor substrate mounting process, can be easily removed with hot water at the end of the mounting process, and prevents contamination of electronic components.

[0048] The temporary protective material of the present invention can protect the component mounting surface by being attached to it during the semiconductor substrate mounting process. Furthermore, the temporary protective material of the present invention can be improved in terms of water resistance by promoting crosslinking and then heating it after being attached to the component mounting surface during the semiconductor substrate mounting process. Regarding the above heating conditions, the heat treatment temperature is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 160°C or higher, preferably 190°C or lower, more preferably 185°C or lower, and even more preferably 180°C or lower. The heat treatment time is preferably 5 minutes or more, more preferably 15 minutes or more, preferably 60 minutes or less, more preferably 45 minutes or less, even more preferably 40 minutes or less, and particularly preferably 30 minutes or less. However, it is preferable to lengthen the heat treatment time when the processing temperature is low, and to shorten the heat treatment time when the processing temperature is high. The heat treatment temperature and heat treatment time can be appropriately set considering the shape, heat capacity, heat resistance, and required water resistance, heat resistance, and ease of solubility of the object to be protected. [Effects of the Invention]

[0049] According to the present invention, it is possible to provide a temporary protective material that has water resistance capable of protecting the component mounting surface in the semiconductor substrate mounting process, and that can be easily removed with hot water. [Modes for carrying out the invention]

[0050] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0051] (Synthesis Example 1) [PVA1 (Saponification degree 98.4 mol%, weight-average molecular weight 15000)] In a reactor equipped with a thermometer, stirrer, and condenser, 2000 parts by weight of vinyl acetate monomer and 200 parts by weight of methanol were added. Nitrogen gas was blown in for 30 minutes to purge the reactor with nitrogen, and then the reactor was heated to 60°C for 30 minutes. Next, 456.5 parts by weight of 2,2'-azobisisobutyronitrile, a polymerization initiator, was added, and the reaction was carried out at 60°C for 4 hours. After the reaction time was complete, the reaction mixture was cooled. After cooling... 1 The polymerization rate was measured by 1H-NMR and found to be 99%. Next, under reduced pressure, the remaining vinyl acetate monomer was removed along with methanol, with methanol being added as needed, to obtain a methanol solution containing 50% by weight of polyvinyl acetate. To this methanol solution, a methanol solution of sodium hydroxide was added to a concentration of 0.07 mol% sodium hydroxide relative to vinyl acetate, and saponification was carried out at 40°C. The resulting solid was pulverized, washed with methanol, and dried to obtain PVA1. The degree of saponification of the obtained PVA1 was measured according to the method in accordance with JIS K6726. The weight-average molecular weight of the polyvinyl alcohol-based resin was determined by gel permeation chromatography using LF-804 (SHOKO Co., Ltd.) as the column, and the weight-average molecular weight was measured in polystyrene equivalent. The results showed that the degree of saponification and weight-average molecular weight were 98.4 mol% and 15000, respectively.

[0052] (Synthesis Example 2) [PVA2 (saponification degree 88.0 mol%, weight-average molecular weight 30000)] PVA2 was obtained by performing the same procedure as in Synthesis Example 1, except that the amount of 2,2'-azobisisobutyronitrile added was changed to 4.2 parts by weight, and the amount of methanol solution of sodium hydroxide added was changed to 0.02 mol% of sodium hydroxide relative to vinyl acetate, resulting in a degree of saponification of 88.0 mol% and a weight-average molecular weight of 30,000, respectively.

[0053] (Synthesis Example 3) [PVA3 (Saponification degree 98.4 mol%, weight-average molecular weight 22000)] PVA3 was obtained by performing the same procedure as in Synthesis Example 1, except that the amount of 2,2'-azobisisobutyronitrile added was changed to 22.9 parts by weight, and the amount of methanol solution of sodium hydroxide added was changed to 0.07 mol% of the sodium hydroxide relative to vinyl acetate. The result was a PVA3 with a degree of saponification of 98.4 mol% and a weight-average molecular weight of 22000, respectively.

[0054] (Example 1) A 20% by weight aqueous solution of polyvinyl alcohol-based resin was prepared by dissolving the resin in hot water at 90°C or higher and then cooling it to room temperature. PVA1 was used as the polyvinyl alcohol-based resin. Furthermore, boric acid (B(OH)3) was dissolved in water to obtain a 3% by weight boric acid aqueous solution. A temporary protective aqueous solution was obtained by mixing an aqueous solution of polyvinyl alcohol resin with an aqueous solution of boric acid in an amount of 0.412 parts by weight per 100 parts by weight of polyvinyl alcohol resin, and then degassing the mixture.

[0055] The obtained temporary protective material aqueous solution was applied to the non-release surface of a polyethylene terephthalate film, which had been treated with a release agent on one side, using a baker-type applicator to achieve a thickness of 70 μm after drying. The solution was then dried in a hot air circulating oven at 80°C to remove moisture and obtain a film-like temporary protective material.

[0056] The obtained temporary protective material was peeled off the polyethylene terephthalate film, placed on a Teflon® sheet, and subjected to heat treatment by being left to stand in a hot air circulating oven at a temperature of 180°C for 30 minutes.

[0057] (Examples 2-10, Comparative Examples 1-4) Using the polyvinyl alcohol-based resins shown in Table 1, an aqueous solution of the polyvinyl alcohol-based resin and an aqueous solution of boric acid were mixed in the proportions shown in Table 1, and the mixture was degassed to obtain an aqueous solution of a temporary protective material. A film-like temporary protective material was obtained in the same manner as in Example 1, except that the obtained temporary protective material aqueous solution was used. The obtained temporary protective material was subjected to heat treatment under the conditions shown in Table 1.

[0058] (evaluation) The temporary protective materials obtained in the examples and comparative examples were evaluated as follows. The results are shown in Table 1.

[0059] (1) Boric acid content The boric acid content in the obtained temporary protective material was evaluated according to the following criteria, after confirming the relationship between formulas (1) and (2) below.

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[0062] <Formula (1)> ○: Satisfies equation (1). ×: Does not satisfy equation (1). <Formula (2)> ○: Satisfies equation (2). ×: Does not satisfy equation (2). <Equations (1) and (2)> ◎: Satisfies both equation (1) and equation (2). ×: Does not satisfy at least one of equations (1) or (2).

[0063] (2) Measurement of gel fraction (45kHz ultrasonic dissolution test) After heating, the temporary protective material was cut into 5cm x 5cm pieces to prepare test specimens, and their initial weight was measured. 200 ml of pure water was placed in a 500 ml beaker, and the test specimens were immersed in it. After that, the beaker was placed in an ultrasonic cleaner. The water in the beaker was set to 35°C and subjected to ultrasonic cleaning at 45kHz for 15 minutes. After that, it was filtered through a 200-mesh stainless steel mesh and dried in an 80°C oven while still in the mesh. The weight of undissolved components was calculated from the difference between the weight of the wire mesh before filtration and the weight of the wire mesh after filtration and drying. The gel fraction (weight %) was determined by calculating the ratio of the weight of undissolved components to the initial weight of the test specimen, and was evaluated according to the following criteria. A high gel fraction measured by 45kHz ultrasonic testing indicates excellent water resistance. ○: The gel fraction was 70% by weight or more. ×: The gel fraction was less than 70% by weight.

[0064] (3) Measurement of gel fraction (80°C hot water dissolution test) After heating, the temporary protective material was cut into 5cm x 5cm pieces to prepare test specimens, and their initial weight was measured. After adding 200 ml of distilled water and a stirring bar to a 300 ml beaker, it was placed in a water bath equipped with a stirrer. The water in the beaker, placed in a water bath, was heated to 80°C. Once the water temperature stabilized at 80°C, the test specimen was added. Fifteen minutes after the test specimens were added, the beaker was removed from the water bath, filtered through a 200-mesh stainless steel mesh, and dried in an 80°C oven while still in the mesh. The weight of undissolved components was calculated from the difference between the weight of the wire mesh before filtration and the weight of the wire mesh after filtration and drying. The gel fraction (weight %) was determined by calculating the ratio of the weight of undissolved components to the initial weight of the test specimen, and evaluated according to the following criteria. A low gel fraction in an 80°C hot water dissolution test indicates high removal efficiency with hot water. ○: The gel fraction was 5% by weight or less. ×: The gel fraction exceeded 5% by weight.

[0065] [Table 1] [Industrial applicability]

[0066] According to the present invention, a temporary protective material is provided that has water resistance capable of protecting the component mounting surface in the semiconductor substrate mounting process, and that can be easily removed with hot water.

Claims

1. A temporary protective material used as a protective material during semiconductor manufacturing, It contains polyvinyl alcohol-based resin and boric acid, A temporary protective material wherein the content C (by weight) of boric acid in the temporary protective material satisfies the following formulas (1) and (2). 【Number 1】 [Math 2] In formulas (1) and (2), A represents the degree of saponification of the polyvinyl alcohol resin (mol%), B represents the weight-average molecular weight of the polyvinyl alcohol resin, and C represents the boric acid content (weight%).

2. The temporary protective material according to claim 1, wherein the boric acid content in the temporary protective material is 0.025% by weight or more and 15% by weight or less.

3. The temporary protective material according to claim 1 or 2, wherein the degree of saponification of the polyvinyl alcohol-based resin is 70.0 mol% or more and 100 mol% or less.

4. The temporary protective material according to claim 1 or 2, wherein the weight-average molecular weight of the polyvinyl alcohol-based resin is 8,000 to 150,000.

5. The temporary protective material according to claim 1 or 2, wherein the gel fraction after heating is 70% by weight or more when ultrasonic vibration is applied in 35°C water for 15 minutes.

6. The temporary protective material according to claim 1 or 2, wherein the gel fraction after heating is 5% by weight or less when immersed in 80°C water for 15 minutes.

7. The temporary protective material according to claim 1 or 2, wherein the gel fraction when ultrasonic vibration is applied to the material in 35°C water for 15 minutes after heating is 70% by weight or more, and the gel fraction when the material is immersed in 80°C water for 15 minutes after heating is 5% by weight or less.

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