JP5167612B2 - Entry sheet for drilling - Google Patents

Description

  The present invention relates to an entry sheet for drilling used in drilling processing of a copper-clad laminate, a multilayer board or the like in a manufacturing process of a printed wiring board.

  As a drilling method for copper-clad laminates and multilayer boards used for printed wiring board materials, one or more copper-clad laminates or multilayer boards are stacked, and aluminum foil alone is used as a backing plate on the top. Alternatively, a method is generally employed in which a drilling entry sheet in which a resin composition layer is formed on the surface of an aluminum foil is disposed to perform drilling. In recent years, due to the demand for higher density and improved reliability of printed wiring board materials, high-quality drilling processing such as improved hole position accuracy and reduced hole wall roughness has been required. A drilling method using a sheet made of a water-soluble resin such as glycol (see, for example, Patent Document 1), a drilling lubricant sheet in which a water-soluble resin layer is formed on a metal foil (see, for example, Patent Document 2), thermosetting A punching entry sheet (for example, see Patent Document 3) in which a water-soluble resin layer is formed on an aluminum foil on which a resin thin film is formed has been proposed and put to practical use. In recent years, with the progress of smaller drill bit diameters corresponding to the higher density of printed wiring boards, the influence of winding of the entry sheet resin around the drill bit has increased, causing runout and deterioration of chip discharge, There is an increasing tendency for hole position accuracy to decrease due to resin dropping and drill bit breakage. For this reason, there is a strong demand for an entry sheet for drilling with excellent hole position accuracy with little entry sheet resin winding around the drill bit.

JP-A-4-92488 JP-A-5-169400 JP 2003-136485 A

  An object of the present invention is to solve the above-mentioned problems in the prior art when drilling a copper-clad laminate or multilayer board, that is, an entry sheet to a drill bit that causes a decrease in hole position accuracy or drill breakage. The present invention provides an entry sheet for drilling with excellent hole position accuracy with reduced resin wrapping.

  As a result of intensive research on the measures for reducing the wrapping of the resin around the drill bit, the inventors have found that the wrapping phenomenon is caused by the resin on the surface of the entry sheet at the root of the drill bit that has become hot due to frictional heat during drilling. The composition softens and adheres, and then cools and hardens. Covering the surface of this resin composition layer with a specific hardened resin layer that is difficult to soften reduces the winding of the resin around the drill bit. And found the present invention. That is, in the present invention, a water-soluble resin (a) -containing resin composition layer is formed on at least one surface of a metal foil, and a photocured resin cured product layer is formed on the surface of the resin composition layer. Entry sheet for drilling, preferably a drilling entry sheet having a thickness of the cured product layer of the photocurable resin of 0.5 to 20 μm, more preferably a cured product layer of the photocurable resin The ratio of the thickness of the resin composition layer to the thickness of the resin composition layer (photocured resin cured product layer thickness / resin composition layer thickness) is in the range of 0.01 to 0.5.

  By using the entry sheet for drilling according to the present invention, the wrapping of the entry sheet resin around the drill bit during drilling is reduced. As a result, even in drilling processing using a drill bit having a small diameter or less, it is possible to perform drilling processing with high quality and excellent productivity, which can prevent deterioration in hole position accuracy and drill breakage.

  In the present invention, a water-soluble resin (a) -containing resin composition layer is formed on at least one side of a metal foil, and a photocured resin cured product layer is formed on the surface of the resin composition layer. This is an entry sheet for drilling. The water-soluble resin (a) -containing resin composition layer formed on the metal foil is usually one layer, but may be a composite layer of two or more layers. In the case of a composite layer, the resin composition layer The surface means the surface of the composite layer.

  The water-soluble resin (a) used in the resin composition layer of the drilling entry sheet of the present invention is particularly a polymer compound that dissolves 1 g or more in 100 g of water at room temperature and normal pressure. It is not limited. Preferable examples include polyethylene oxide, polypropylene oxide, polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyvinyl pyrrolidone, carboxymethyl cellulose, polytetramethylene glycol, polyether ester, and polyvinyl alcohol. It is also possible to mix them as appropriate. The amount of the water-soluble resin (a) in the resin composition is preferably 10 to 90% by weight, more preferably 20 to 80% by weight. In order to enhance the lubricating effect during drilling, it is preferable to use a water-soluble lubricant (b) described later in combination with these water-soluble resins (a) as the resin composition.

  The polyether ester which is one type of the water-soluble resin (a) used in the present invention is not particularly limited as long as it is an esterified product of polyalkylene oxide. Typical examples include polyethylene glycol, polyethylene oxide, polypropylene glycol, polytetramethylene glycol, glycols exemplified by polypropylene oxide and copolymers thereof, or polymers of ethylene oxide, and phthalic acid, isophthalic acid. Terephthalic acid, sebacic acid, and the like, and dimethyl esters, diethyl esters and the like, polymellitic carboxylic acids exemplified by pyromellitic acid anhydride, the anhydrides, or resins obtained by reacting the esters, etc. It is also possible to use one kind or a mixture of two or more kinds as appropriate.

  Specific examples of the water-soluble lubricant (b) suitably used in the water-soluble resin (a) used in the resin composition layer of the drill hole entry sheet of the present invention include polyethylene glycol, polypropylene glycol; Polyoxyethylene monoethers exemplified by polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether and the like; Polyoxyethylene monostearate, polyoxyethylene sorbitan monostearate; polyglycerol monostearates exemplified by hexaglycerol monostearate, decahexaglycerol monostearate, etc .; Shi ethylene propylene copolymer and the like, may be used by appropriately blending one or two or more. The blending amount of the water-soluble lubricant (b) in the resin composition is preferably 10 to 90% by weight, more preferably 20 to 80% by weight. If the water-soluble lubricant (b) is less than 10% by weight, the lubricating effect at the time of drilling tends to be insufficient, and if it exceeds 90% by weight, the resin composition layer may become brittle.

  The thickness of the water-soluble resin (a) -containing resin composition layer in the drill hole entry sheet of the present invention is the diameter of the drill bit used in drilling, the structure of the copper-clad laminate or multilayer board to be processed, etc. In general, the range of 5 to 250 μm is preferable, and the range of 10 to 200 μm is more preferable. If the thickness of the water-soluble resin (a) -containing resin composition layer is less than 5 μm, it is difficult to obtain a sufficient lubricating effect, and if it exceeds 250 μm, the winding of the entry sheet resin around the drill bit increases. Various additives can also be used in the water-soluble resin (a) -containing resin composition. For example, organic or inorganic fillers, dyes, color pigments and the like are used in accordance with the purpose.

  The metal foil used in the entry sheet for drilling according to the present invention is preferably an aluminum foil having a thickness of 50 to 300 μm. If the thickness of the aluminum foil is less than 50 μm, burrs are likely to occur in the copper-clad laminate or multilayer board during drilling, and if it exceeds 300 μm, it becomes difficult to discharge the chips generated during drilling. As the material of the aluminum foil, aluminum having a purity of 95% or more is more preferable. Specific examples include 5052, 3004, 3003, 1N30, 1050, 1070, and 1085 as defined in JIS H4160. By using high-purity aluminum foil for metal foil, the impact and biting of the drill bit are reduced, and the drill bit lubrication effect by the resin composition layer improves the accuracy of the hole position of the processed hole. . In addition, the use of an aluminum foil in which an adhesive film having a thickness of 0.1 to 10 μm is previously formed on these aluminum foils is more preferable from the viewpoint of adhesion to the resin composition. Examples of the adhesive used for the adhesive film include urethane-based, vinyl acetate-based, vinyl chloride-based, polyester-based and copolymers thereof, and epoxy-based and cyanate-based adhesives. As a method for forming the water-soluble resin (a) -containing resin composition layer on at least one side of the metal foil, a sheet of the water-soluble resin (a) -containing resin composition is prepared in advance, and then bonded to the metal foil and the metal foil A method of making a composite resin composition sheet, or applying a solution or solution of a water-soluble resin (a) -containing resin composition directly on at least one side of a metal foil by a coating method, etc., and drying as necessary The method etc. which are set as a composite resin composition sheet are illustrated.

  The photocurable resin formed and cured on the surface of the water-soluble resin (a) -containing resin composition layer of the drill hole entry sheet of the present invention is not particularly limited as long as it is a compound that is cured by the action of light energy. . Photocurable resins include radical polymerization resins and radical addition resins. Typical examples of radical polymerization resins include unsaturated polyester resins, polyester acrylate resins, polyether acrylate resins, and acrylated epoxy resin resins. Examples of the radical addition type resin include an acrylic polyurethane type and an acrylic resin type, and examples of the radical addition type resin include a cationic polymerization type resin such as an epoxy resin type.

  An appropriate amount of a photopolymerization initiator for initiating the reaction is blended with the photocurable resin used in the present invention. A photopolymerization initiator is a substance that activates by absorbing light and causes a reaction such as a cleavage reaction, hydrogen abstraction, or electron transfer to generate a substance that initiates a reaction such as a radical molecule or hydrogen ion. Examples include benzophenone series, Michler ketones, benzyls, benzoin and benzoin ethers, benzylmethyl ketals, thioxanthones, and the like. Examples of light energy used for curing a resin composition obtained by adding a photopolymerization initiator to a photocurable resin include ultraviolet rays. To cure a photocurable resin, ultraviolet light having an output wavelength in the range of 200 to 450 nm is used. It is common to use an irradiation device.

  The thickness of the cured product layer of the photocurable resin formed on the surface of the water-soluble resin (a) -containing resin composition layer of the drill hole entry sheet of the present invention is preferably in the range of 0.5 to 20 μm, and 2 to 15 μm. A range is more preferred. If the thickness of the cured product layer of the photocurable resin is less than 0.5 μm, the effect of reducing the winding of the entry sheet resin around the drill bit during drilling is insufficient, and the thickness of the cured product layer of the photocurable resin is 20 μm. If it exceeds, the lubricating effect of the water-soluble resin (a) -containing resin composition layer may be hindered, and the hole position accuracy may be lowered. The ratio of the thickness of the cured product layer of the photocurable resin to the thickness of the resin composition layer (the thickness of the cured product layer of the photocurable resin / the thickness of the resin composition layer) is preferably in the range of 0.01 to 0.5. .

  In the drill hole entry sheet of the present invention, the method for forming a cured layer of a photocurable resin on the surface of the water-soluble resin (a) -containing resin composition layer includes a water-soluble resin (a) -containing resin composition For example, a method of applying a photocurable resin to one side of the sheet or the resin composition layer surface of the metal foil composite resin composition sheet by a coating method using a bar coater, etc., and then curing by ultraviolet irradiation, spraying, etc. There is a method of applying a photo-curing resin by using UV and then curing by ultraviolet irradiation in the same manner. However, in order to obtain the thickness uniformity of the cured product layer of the photo-curing resin, a coating method is desirable. A small irradiation device is used for the ultraviolet irradiation method, and a continuous irradiation device using a conveyor is used for mass production. When a cured layer of a photocurable resin is formed on one side of a sheet of the water-soluble resin (a) -containing resin composition, a metal foil is then bonded to the surface on which the cured layer is not formed, When the cured product layer of the photocurable resin is formed on the resin composition layer surface of the composite resin composition sheet, it becomes the drill hole entry sheet of the present invention as it is.

  The drill hole entry sheet of the present invention is a printed wiring board material, specifically, one or more copper clad laminates or multilayer boards when drilling a copper clad laminate or multilayer board. Is placed on at least the uppermost surface so that it is in contact with the copper-clad laminate or multilayer board, and drilling is performed from the cured layer side of the photocurable resin of the drilling entry sheet. . Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

(Example 1)
Using a kneader, heat 50 parts by weight of polyethylene oxide (Alcox R-150, Meisei Chemical Industries) with a number average molecular weight of 150,000 and 50 parts by weight of polyethylene glycol (PEG 20000, Sanyo Chemical Industries) with a number average molecular weight of 20,000. After kneading under a nitrogen gas seal at 130 ° C., it was passed through a heating roll at 100 ° C. to obtain a resin composition sheet having a thickness of 50 μm. This resin composition sheet was bonded to an aluminum foil having a thickness of 100 μm (manufactured by Mitsubishi Aluminum, material 3004) through a laminator to obtain a metal foil composite resin composition sheet A. Next, in a dark room, on the surface of the resin composition layer of the metal foil composite resin composition sheet A, unsaturated polyester resin (Goserac G223, manufactured by Nippon Synthetic Chemical) and photopolymerization initiator benzyldimethyl ketal (Irgacure 651, Ciba Geigy) After coating with a bar coater, the coating composition blended with the ratio of GOSELAC G223: Irgacure 651 = 100: 3 was irradiated for 60 seconds with a hand-held ultraviolet irradiation device (wavelength 365 nm), and the metal foil composite resin composition sheet A An entry sheet B for drilling was obtained in which a cured product layer of a photocurable resin having a thickness of 10 μm was formed on the surface of the resin composition layer. This drilling entry sheet B is made by stacking 6 sheets of 0.4mm thick copper clad laminate (CCL-HL832, copper foil on both sides 12μm, manufactured by Mitsubishi Gas Chemical), and then a cured layer of photo-curing resin. Is placed on top of the stacked copper-clad laminate, and a batting plate (bake plate) is placed on the underside of the laminated copper-clad laminate, with a drill bit of 0.3 mmφ, a rotational speed of 120,000 rpm, and a feed rate of 20 μm / rev. Table 1 shows the results of evaluating the degree of resin wrapping around the drill bit and the accuracy of the hole position by drilling 20 drill holes at 4,000 hits per drill bit.

(Comparative Example 1)
In Example 1, instead of the drilling entry sheet B, the metal foil composite resin composition sheet A is used as it is as an entry sheet for drilling by placing the resin composition layer on the copper-clad laminate. Except that, drilling was performed in the same manner as in Example 1, and the results of evaluating the degree of resin wrapping around the drill bit and the accuracy of the hole position are shown in Table 1.

(Example 2)
Polyethylene glycol dimethyl terephthalate polycondensate (Paogen PP-15, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 50 parts by weight, polyoxyethylene monostearate (Nonion S-40, manufactured by NOF Corporation) using a kneader, After kneading in a nitrogen atmosphere at a temperature of 140 ° C., a sheet having a thickness of 100 μm was prepared with an extruder. This sheet is laminated on one side of an adhesive film-formed aluminum foil in which 2 μm of a polyester adhesive (R820, manufactured by Cemedine) is previously applied as an adhesive film to an aluminum foil with a thickness of 100 μm (manufactured in Japan, material 1N30). The metal foil composite resin composition sheet C was obtained by bonding with a heating roll at 100 ° C. Next, in the dark room, acrylate resin (Kayarad R604, manufactured by Nippon Kayaku) and benzyldimethyl ketal (Irgacure 651) are applied to the surface of the resin composition layer of the metal foil composite resin composition sheet C. Kayrad R604: Irgacure 651 = 100 : After coating the paint mixed at a ratio of 3 with a bar coater, irradiate it with a handy ultraviolet irradiation device (wavelength 365 nm) for 90 seconds to form a cured product layer of a photocurable resin with a thickness of 15 μm on the resin composition surface. The formed drill hole entry sheet D was obtained. This drilling entry sheet D is made by stacking four 0.1mm thick copper clad laminates (CCL-HL832HS, copper foil both sides 12μm, manufactured by Mitsubishi Gas Chemical Co., Ltd.), and a cured product layer of photo-curing resin. Is placed on top of the laminated copper-clad laminate, and a batting plate (bake plate) is placed underneath the drill bit: 0.15 mmφ, rotation speed: 160,000 rpm, feed rate: 15 μm / rev. Table 1 shows the results of evaluating the degree of resin wrapping around the drill bit and the accuracy of the hole position by drilling 20 drill holes at 4,000 hits per drill bit.

(Comparative Example 2)
In Example 2, instead of the drilling entry sheet D, the metal foil composite resin composition sheet C is used as it is as an entry sheet for drilling by placing it on a copper clad laminate with the resin composition layer facing up. Except that, drilling was performed in the same manner as in Example 2, and the results of evaluating the degree of resin wrapping around the drill bit and the accuracy of the hole position are shown in Table 1.

(Table 1)
Examples Comparative Examples Examples Comparative Examples
Item 1 1 2 2
Resin wrapping degree (book)
Minor 18/20 3/20 17/20 2/20
Less 2/20 5/20 3/20 8/20
Many 0/20 12/20 0/20 10/20
Hole position accuracy (μm)
Average value of (Average + 3σ) 23 28 13 17
Average of maximum values 40 45 37 42

<Evaluation method>
1) Degree of resin wrapping: 20 drill bits after 4,000-hit processing are observed with a microscope with a magnification of 25 times, and the maximum diameter of the resin wrapping with respect to the drill bit diameter is obtained. Less than double: micro, 1.5 to 5 times: less, more than 5 times: many), and the corresponding number / 20 (book).
2) Hole position accuracy: Measure the gap between the specified position and the 4,000-hit hole position on the back of the bottom plate of the laminated copper clad laminate with a hole analyzer (manufactured by Hitachi Via Mechanics). Calculated and expressed the average value for 20 drilling operations.

Claims (2)

A water-soluble resin (a) -containing resin composition layer is formed on at least one surface of the metal foil, and an unsaturated polyester, polyester acrylate, polyether acrylate, or acrylated epoxy is formed on the surface of the resin composition layer. One or more photocurable resins selected from the group consisting of resin-based, acrylated polyurethane-based, acrylic resin-based, and epoxy resin-based materials and a photopolymerization initiator are cured by ultraviolet irradiation at a wavelength of 200 to 450 nm. An entry sheet for drilling, in which a cured product layer having a thickness of ˜20 μm is formed. The ratio of the thickness of the cured product layer of the photocurable resin to the thickness of the resin composition layer (the thickness of the cured product layer of the photocurable resin / the thickness of the resin composition layer) is 0.01 to 0.5. range at which claim 1 Symbol mounting drill drilling for entry sheet.