JP2009239141A - Method of boring insulation sheet and method of manufacturing wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of boring an insulation sheet, in which cutting waste sticks neither in a through-hole of the insulation sheet nor on its periphery; and to provide a method of manufacturing a wiring board, in which electric signals are excellently sent to and received from a mounted semiconductor element. <P>SOLUTION: In the method of boring the insulation sheet in which a through-hole is bored in the insulation sheet 3 by sucking and fixing the insulation sheet 1 on a suction table 30 with an air-permeable sheet 20 interposed, and irradiating the insulation sheet 1 with laser light L from its upper surface side, the air-permeable sheet 20 is made of a resin material where a liquid phase is formed during the laser irradiation. In the method of manufacturing the wiring board, conductive paste is charged in the through-hole 3 of the insulation sheet 1 having the through-hole 3 formed by the method, and a wiring conductor made of metal foil is laminated on an upper surface of the insulation sheet 1 charged with the conductive paste to be connected to the conductive paste. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for punching an insulating sheet in which a through hole is drilled in an insulating sheet by laser processing, and a method for manufacturing a wiring board using the punching method.

  Conventionally, an insulating layer formed by thermally curing an insulating sheet impregnated with an uncured thermosetting resin on a heat-resistant fiber base material such as glass cloth as a wiring substrate used for mounting electronic components such as semiconductor elements And wiring conductors made of metal foil such as copper foil are alternately laminated, and the conductive paste filled in the through holes formed in the insulating layer is cured between the wiring conductors located above and below the insulating layer. A wiring board is known which is electrically connected by a through conductor formed as described above.

This wiring board is manufactured as follows, for example.
(A) A resin film having a thickness of about 5 to 15 μm made of polyethylene terephthalate is detachably adhered to both main surfaces of an insulating sheet obtained by impregnating a heat-resistant fiber base material with an uncured thermosetting resin.
(B) Next, the upper and lower resin films are subjected to laser processing from above the resin film in a state where the insulating sheet to which the resin film is closely attached is adsorbed on the adsorption table with a breathable sheet such as paper or cloth in between. And the through-hole which connects an insulating sheet is formed.
(C) Next, a conductive paste made of a conductive powder such as metal and an uncured thermosetting resin is filled into the through-hole communicating with the resin film and the insulating sheet from above the resin film by screen printing (press-fit). To do. In this case, a resin film having a through hole is used as a mask for printing.
(D) Next, the resin film is peeled and removed from both main surfaces of the insulating sheet filled with the conductive paste in the through holes. At this time, the conductive paste filled in the through holes of the insulating sheet is in a state of protruding from the main surface of the insulating sheet corresponding to the thickness of the resin film.
(E) Next, a wiring conductor made of a metal foil previously formed in a predetermined pattern on the transfer film is pressed against at least one main surface of the insulating sheet so as to cover the end of the conductive paste. And laminate.
(F) Next, a plurality of insulating sheets on which wiring conductors are laminated are laminated, and heated and pressed using a hot press at a temperature of 180 to 240 ° C. for several minutes to several hours to cure the insulating sheet and the conductive paste. To obtain a wiring board.

However, as described above, the upper and lower resins are obtained by applying laser processing from above the resin film in a state where the insulating sheet to which the resin film is closely attached is adsorbed on the adsorption table with a breathable sheet made of paper or cloth in between. When a through-hole that communicates the film and the insulating sheet is formed, the paper or cloth constituting the air-permeable sheet is made of fibers, and fiber scraps of a size of about several μm are easily generated as processing scraps by laser irradiation and scattered around. In addition, since there is a gap of about several μm to several tens of μm between the fibers, fiber waste generated by laser processing is scattered in the through hole and adhered to the through hole of the insulating sheet, It adheres around the through-holes on the surface of the resin film through the gaps between the fibers of the breathable sheet. When fiber waste adheres to the inside of the through hole of the insulating sheet or the surface of the resin film, the fiber waste is caught in the conductive paste when filling the through hole with the conductive paste and becomes a foreign substance. Then, when the conductive paste in the through hole is cured to form a through conductor, the fiber waste that is involved as a foreign object in the contact between the metal powders in the through conductor is obstructed, and the electrical resistance of the through conductor is increased. There is a problem in that it becomes impossible to exchange electric signals with a semiconductor element to be mounted.
JP 2003-283129 A JP-A-11-90667

  The subject of this invention is providing the punching method of the insulating sheet in which the laser processing waste does not adhere in the through-hole of an insulating sheet, or a through-hole periphery. Another object of the present invention is that the electrical resistance of the through conductor formed by curing the conductive paste does not increase due to the foreign matter, and the electrical signal can be exchanged with the mounted semiconductor element satisfactorily. An object of the present invention is to provide a wiring board manufacturing method capable of manufacturing a possible wiring board.

In the insulating sheet punching method of the present invention, an insulating sheet is sucked and fixed by sandwiching a breathable sheet on a suction table, and a laser is irradiated from the upper surface side of the insulating sheet to form a through hole in the insulating sheet. The sheet perforation method is characterized in that the breathable sheet is made of a resin material that forms a liquid phase upon laser irradiation.
Furthermore, in the method for perforating an insulating sheet of the present invention, the breathable sheet is formed such that nanoporous regions formed by voids having a size of 5 to 20 nm are formed in a stripe pattern in the thickness direction. It is a feature.

  Further, in the method for manufacturing a wiring board according to the present invention, the conductive paste is filled in the through hole of the insulating sheet in which the through hole is formed by the method for punching the insulating sheet of the present invention, and the conductive paste is filled. It includes a step of laminating a wiring conductor made of a metal foil on the surface of the insulating sheet so as to be connected to the conductive paste.

According to the method for perforating an insulating sheet of the present invention, since the breathable sheet is made of a resin material that forms a liquid phase upon laser irradiation, it melts by laser processing, but the melt does not scatter. It does not adhere in the through-hole formed in the insulating sheet.
Further, in the case where the breathable sheet has a nanoporous region formed by voids having a size of 5 to 20 nm in a stripe shape in the thickness direction, even if scraps having a size of about several μm are generated. The debris does not pass through the nanoporous region and adhere to the periphery of the through hole.
In addition, according to the method for manufacturing a wiring board of the present invention, the conductive paste is filled in the through hole of the insulating sheet in which the through hole is formed by the method for punching the insulating sheet of the present invention. Foreign matter is not mixed into the filled conductive paste. Therefore, a wiring board capable of satisfactorily exchanging electrical signals with a mounted semiconductor element without increasing the electrical resistance of a through conductor formed by curing a conductive paste, and manufacturing with good yield. Can do.

  Next, a method for punching an insulating sheet according to an embodiment of the present invention will be described with reference to the accompanying drawings. 1 to 3 are schematic cross-sectional views for each step for explaining a method for punching an insulating sheet according to the present embodiment. In these drawings, 1 is an insulating sheet, 2 is a resin film, 3 is a through-hole, 20 is a breathable sheet and 30 is a suction table.

  First, as shown in FIG. 1, an insulating sheet 1 having a resin film 2 attached to both upper and lower main surfaces, a breathable sheet 20, and a suction table 30 are prepared.

  The insulating sheet 1 is a rectangle having a thickness of about 30 to 200 μm, a width and a length of about 20 to 60 cm, respectively, and a heat-resistant fiber base material obtained by weaving a bundle of heat-resistant fibers vertically and horizontally into a sheet shape, and uncured thermosetting. After impregnating the curable resin, it is in a dry or semi-cured state, and as the heat-resistant fiber, for example, glass fiber, aramid fiber, wholly aromatic ester fiber, etc. are used, and as the thermosetting resin, for example, Epoxy resins, bismaleimide triazine resins, allyl-modified polyphenylene ether resins and the like are used. The resin film 2 has a thickness of about 5 to 15 μm, and a film such as polyethylene terephthalate is used. The resin film 2 is detachably attached to both main surfaces of the insulating sheet 1 through an adhesive material (not shown). Yes.

  The breathable sheet 20 is made of a resin such as polyethylene, polypropylene, polyester, polycarbonate, polyamide, or polyimide, and has a thickness of about 100 to 300 μm. A nanoporous region having a width of about 5 to 10 μm in which minute voids of about 5 to 20 nm are formed from the upper surface to the lower surface is regularly arranged at intervals of 20 to 30 μm. It has air permeability that allows air to pass from the upper surface side to the lower surface side through the quality region. The amount of air passing through the breathable sheet 20 is preferably about 0.1 to 2 cc / min. Such a breathable sheet 20 is formed by bending a resin sheet made of polyester, for example, substantially in parallel with the molecular orientation direction to form a bent portion, and then the direction orthogonal to the bending line in the bent portion. To form a continuous striped nanoporous region substantially parallel to the molecular orientation direction.

  Further, the suction table 30 is a flat plate made of porous ceramic formed by, for example, hardening alumina particles with glass and firing, and the lower surface thereof is connected to a suction device (not shown). Then, the object placed on the upper surface can be sucked and fixed by sucking air from the upper surface side.

  Next, as shown in FIG. 2, the insulating sheet 1 to which the resin film 2 is adhered is placed on the suction table 30 through the breathable sheet 20, and the lower surface of the suction table 30 by a suction device (not shown). The insulating sheet 1 is sucked and fixed onto the suction table 30 by sucking air from the side through the suction table 30 and the breathable sheet 20.

  Next, as shown in FIG. 3, a plurality of through holes 3 penetrating the resin film 2 and the insulating sheet 1 are formed by irradiating the laser L from above the insulating sheet 1 to which the resin film 2 is adhered. At this time, a through hole is also formed in the breathable sheet 20. However, since the air-permeable sheet 20 is made of resin as described above, it melts by forming a liquid phase by irradiation with the laser L, but the melt does not scatter, and thus the penetration formed in the insulating sheet 1. Laser processing debris does not adhere in the hole 3. Further, the air-permeable sheet 20 has a structure in which nano-porous regions having a width of about 5 to 10 μm in which minute voids of about 5 to 20 nm are formed are regularly arranged at intervals of 20 to 30 μm. However, even if a small laser processing scrap of several μm is generated, the scrap does not pass through the breathable sheet and adhere to the periphery of the through hole 3 on the surface of the resin film 2. Thus, according to the method for perforating an insulating sheet of the present invention, it is possible to provide a method for perforating an insulating sheet in which there is no adhesion of laser processing waste in and around the through hole of the insulating sheet.

  Next, the manufacturing method of the wiring board concerning embodiment of this invention is demonstrated. 4 (a) to 6 (h) are schematic cross-sectional views for each step for explaining the method of manufacturing the wiring board according to the present embodiment. In these drawings, 1 is an insulating sheet, 2 is a resin film, 3 is a through hole, 4 is a conductive paste, and 5 is a wiring conductor.

  First, as shown to Fig.4 (a), the insulating sheet 1 in which the through-hole 3 was formed by the method mentioned above is prepared. In addition, the resin film 2 is stuck on both main surfaces of the insulating sheet 1 as described above. Next, as shown in FIG. 4 (b), the conductive paste 4 is filled into the through holes 3 that allow the resin film 2 and the insulating sheet 1 to communicate with each other. In order to fill the through hole 3 with the conductive paste 4, the conductive paste 4 is supplied onto the resin film 2 on the upper surface side, and a squeegee made of hard rubber is slid on the conductive paste 4 while scraping it. A filling method is adopted. At this time, since there is no processing waste associated with laser processing in the through hole 3 of the insulating sheet 1 and the surface of the resin film 2, no foreign matter is mixed into the conductive paste 4 filled in the through hole 3.

  The conductive paste 4 is made of, for example, a metal powder made of an alloy of tin, silver, bismuth and copper and a triazine type such as triallyl cyanurate, triallyl isocyanurate, trisepoxypropyl isocyanurate, tris (2-hydroxyethyl) isocyanurate. Containing thermosetting resin. And it exhibits electroconductivity by contact between the metal powders. In addition, the content of the metal powder is preferably 80 to 95% by weight with respect to the total amount of the conductive paste 4. When the content of the metal powder is less than 80% by weight, the connection between the metal powders is hindered by the triazine-based thermosetting resin, and the conduction resistance tends to increase. When the content exceeds 95% by weight, the metal powder and There is a tendency that the viscosity of the conductive paste containing the triazine-based thermosetting resin is so high that it cannot be satisfactorily filled. Therefore, the content of the metal powder is preferably 80 to 95% by weight.

  Next, as shown in FIG. 4C, the resin film 2 is peeled off from both main surfaces of the insulating sheet 1 and removed. At this time, the conductive paste 4 filled in the through holes 3 of the resin film 2 remains in a state of protruding by a height corresponding to the thickness of the resin film 2. At this time, when the thickness of the resin film 2 is less than 5 μm, the conductive paste 4 protruding from the main surface of the insulating sheet 1 has a low height, and as described later, the main surface of the insulating sheet 1 is formed. When the wiring conductor 5 is laminated so as to cover the end portion of the conductive paste 4, there is a high risk that the adhesion between the conductive paste 4 and the wiring conductor 5 becomes weak. When the wiring conductor 5 is laminated on the main surface of the insulating sheet 1 so as to cover the end portion of the conductive paste 4, the conductive paste 4 protrudes from the main surface of the insulating sheet 1. There is a high risk that the portion will be greatly crushed laterally and protrude from the wiring conductor 5. Therefore, the thickness of the resin film 2 is preferably in the range of 5 to 15 μm.

  Next, as shown in FIG. 5D, separately, a wiring made of a metal foil such as a copper foil, which is peelably adhered to one main surface of a transfer film 6 made of a resin film such as polyethylene naphthalate. A conductor 5 is prepared. The wiring conductor 5 on the transfer film 6 has a metal foil such as a copper foil adhered to one main surface of the transfer film 6 via an adhesive material (not shown), and then the metal foil is bonded by photolithography. It is formed by etching into a predetermined pattern. The thickness of the wiring conductor 5 is about 5 to 30 μm.

  Next, as shown in FIG. 5 (e), the wiring conductor 5 on the transfer film 6 is laminated on the insulating sheet 1 so as to cover the end of the conductive paste 4, and then laminated. As shown in 5 (f), the wiring conductor 5 is transferred by removing the transfer film 6.

  Next, as shown in FIG. 6G, the insulating sheet 1 in which the through-hole 3 is filled with the conductive paste 4 and the wiring conductor 5 is laminated on the surface as described above is necessary for manufacturing the wiring board. A plurality of sheets are prepared in such a form (here, a case where there are three insulating sheets 1) is shown.

  Next, as shown in FIG. 6 (h), the plurality of insulating sheets 1 are heated while being pressed in a state where they are stacked one above the other in a predetermined arrangement, and the thermosetting resin and the conductive paste 4 of the insulating sheet 1. By thermally curing the thermosetting resin, insulating layers 11 and wiring conductors 5 in which a plurality of insulating sheets 1 are cured are alternately stacked, and upper and lower wirings are formed by through conductors 14 in which conductive paste 4 is cured. A wiring board 10 to which the conductors 5 are electrically connected is obtained. At this time, since no foreign matter is mixed in the conductive paste 4 filled in the through hole 3, the electrical resistance of the through conductor 14 formed by curing the conductive paste 4 does not increase, and the mounted semiconductor It is possible to provide a wiring board capable of satisfactorily exchanging electrical signals with elements.

These are the schematic sectional drawings for every process for demonstrating the punching method of the insulating sheet of this invention. These are the schematic sectional drawings for every process for demonstrating the punching method of the insulating sheet of this invention. These are the schematic sectional drawings for every process for demonstrating the punching method of the insulating sheet of this invention. (A)-(c) is a schematic sectional drawing for every process for demonstrating the manufacturing method of the wiring board of this invention. (D)-(f) is a schematic sectional drawing for every process for demonstrating the manufacturing method of the wiring board of this invention. (G), (h) is a schematic sectional drawing for every process for demonstrating the manufacturing method of the wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation sheet 2 Resin film 3 Through-hole 4 Conductive paste 5 Wiring conductor 10 Wiring board 20 Breathable sheet 30 Adsorption table

Claims (3)

  A method for perforating an insulating sheet, wherein an insulating sheet is adsorbed and fixed by sandwiching a breathable sheet on an adsorption table, and a through hole is formed in the insulating sheet by irradiating a laser from an upper surface side of the insulating sheet. The insulating sheet is made of a resin material that forms a liquid phase upon laser irradiation.   2. The perforated insulating sheet according to claim 1, wherein the breathable sheet has nanoporous regions formed by voids having a size of 5 to 20 nm arranged in stripes in the thickness direction. Method.   A wiring conductor made of a metal foil on the surface of the insulating sheet filled with the conductive paste while filling the through-hole of the insulating sheet in which the through-hole is formed by the method according to claim 1 or 2 A method for manufacturing a wiring board, comprising: laminating a conductive paste so as to be connected to the conductive paste.

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