JP2010109198A - Method of manufacturing wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board of minute wiring excelling in electrical connection reliability between a penetration conductor and a wiring conductor and having high electrical insulation reliability between adjacent wiring conductors. <P>SOLUTION: This method of manufacturing the wiring board includes a process of forming a ring-like barr 1a swelled from a one-side principal surface of an insulation sheet 1 and forming a ring-like projection 2a projecting at a height not smaller than that of the burr 1a on the resin film 2 outside the burr 1a, by energy by irradiating an opening edge on a one-side principal surface side of a through-hole 3 with laser light in a process of boring the through-hole 3 making a resin film 2 and the insulation sheet 1 communicate with each other by irradiating the insulation sheet 1 with the resin film 2 stuck thereto with the laser light through the resin film 2 from the one-side principal surface side, then filling conductive paste 4 in a through-hole 4 up to the height of the projection 2a, and thereafter wiping the conductive paste 4 up to the height of the burr 1a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention pierces through holes by laser processing in an insulating sheet to be an insulating layer of a wiring board, and after filling the through holes with a conductive paste, wiring conductors made of metal foil on the main surface of the insulating sheet, The present invention relates to a method of manufacturing a wiring board including a step of embedding so as to cover an end portion of the conductive paste.

  Conventionally, an insulating sheet impregnated with an uncured thermosetting resin composition in a heat-resistant fiber base material such as glass cloth is used as a wiring board used for mounting electronic components such as semiconductor elements. Insulating layers and wiring conductors made of metal foil such as copper foil are alternately laminated, and conductive conductors filled in through-holes formed in the insulating layer with the wiring conductors positioned above and below the insulating layer sandwiched between them. There is known a wiring board formed by electrically connecting through a through conductor formed by curing a paste.

This wiring board is manufactured as follows, for example.
(A) First, a thickness made of a thermoplastic resin such as polyethylene terephthalate is 10 on both main surfaces of an insulating sheet having a thickness of about 30 to 200 μm in which a heat-resistant fiber base material is impregnated with an uncured thermosetting resin composition. A resin film of about 30 μm is stuck so as to be peelable.
(B) Next, a laser beam having an output of 2 to 3 mJ and a pulse width of 20 to 40 μs is repeatedly irradiated 4 to 8 times per place on the insulating sheet having the resin film adhered thereto through the resin film from one main surface side. By doing so, a through-hole communicating with the upper and lower resin films and the insulating sheet is drilled. Thus, by repeatedly irradiating a laser beam with a low output of 2-3 mJ and a short pulse width of 20-40 μs 4 to 8 times per place, the energy by the laser beam irradiation is an insulating sheet and a resin film around the through hole. To prevent major deformation.
(C) Next, a conductive paste made of a conductive powder such as metal and an uncured thermosetting resin composition is screened from above the resin film on the one main surface side in a through hole communicating with the resin film and the insulating sheet. Fill by printing (press-fit). In this case, the resin film in which the through hole is formed is used as a mask for printing, and after filling the through hole with the conductive paste, the resin film on the main surface side is wiped with a dust-free cloth, The remaining conductive paste is removed and the surface of the filled conductive paste is flattened.
(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 transfer sheet in which a wiring conductor made of a metal foil is separately formed on a support film so as to be peeled into a predetermined pattern, and the wiring conductor is a conductive paste on at least one main surface of the insulating sheet. Then, the wiring conductor is transferred by peeling and removing the support film from the main surface of the insulating sheet.
(F) Next, a plurality of insulating sheets to which the wiring conductors are transferred are stacked, 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, in this conventional method of manufacturing a wiring board, after filling the through hole with the conductive paste, when wiping the resin film on the main surface side with a dust-free cloth, the conductive paste filled in the through hole A part of the conductive paste is scraped off by a dust-free cloth, and accordingly, the height of the conductive paste protruding from the main surface of the insulating sheet after removing the resin film is lowered. When the conductive paste protruding from the main surface of the insulating sheet is low in this way, when the wiring conductor made of metal foil is pressed and embedded in the main surface of the insulating sheet so as to cover the end of the conductive paste In addition, the reliability of electrical connection between the through conductor in which the conductive paste is cured without being sufficiently pressed against the wiring conductor and the wiring conductor connected thereto is deteriorated.

In addition, the conductive paste protruding from the main surface of the resin sheet after removing the resin film is not easily held in shape because the side surfaces are not retained, and therefore, the conductive paste tends to spread or spread on the main surface of the insulating sheet around the through hole. If there is such spreading or spreading, when the wiring conductor made of metal foil is transferred to the main surface of the insulating sheet by pressure contact so as to cover the end of the conductive paste, the conductive paste will be wired if it is a thin wiring conductor. As a result, the electrical insulation reliability between the adjacent wiring conductors is lowered, which makes it difficult to miniaturize the wiring conductors.
JP 2003-283129 A

  The problem of the present invention is that when a wiring conductor made of a metal foil is transferred to the main surface of an insulating sheet filled with a conductive paste in a through-hole so as to cover the end of the conductive paste, the wiring conductor and the conductive material are electrically conductive. The paste is well pressed and the conductive paste does not protrude from the wiring conductor. As a result, the electrical connection reliability between the through conductor and the wiring conductor with the cured conductive paste is excellent, and the adjacent wiring conductor It is to provide a wiring substrate of fine wiring with high electrical insulation reliability.

  When the inventor of the present invention perforates a through hole that communicates a resin film and an insulating sheet by irradiating a laser beam through the resin film from one main surface side to an insulating sheet having a resin film attached to both main surfaces. In addition, when the punching is performed by irradiating a laser beam having a high output of 5 to 9 mJ and a pulse width of 60 to 100 μs, the resin film and the insulating sheet around the through hole are softened by the energy of the laser beam irradiation. A ring-shaped burr made of a thermosetting resin composition constituting the insulating sheet stands at a height of 5 to 20 μm from the main surface of the insulating sheet at the opening edge on the side where the laser beam is incident in the through hole. It was found that a ring-shaped projection made of a thermoplastic resin constituting the resin film was formed on the outside of the burrs at a height higher than that. The present invention has been devised based on this.

  In the method for producing a wiring board according to the present invention, the step of adhering a resin film made of a thermoplastic resin to both main surfaces of an insulating sheet containing a thermosetting resin composition is attached, and the resin film is attached. Further, the step of piercing the resin film and the insulating sheet by irradiating the insulating sheet with laser light from one main surface side through the resin film, and the resin film and the insulating sheet are communicated. A step of filling the through hole with a conductive paste from the one main surface side, and a step of peeling and removing the resin film from both main surfaces of the insulating sheet filled with the conductive paste in the through hole. And embedding a wiring conductor made of a metal foil on the main surface of the insulating sheet from which the resin film has been removed so as to cover an end portion of the conductive paste. A method of manufacturing a wiring board comprising: a step of drilling the through-hole, wherein in the step of drilling the through-hole, the insulating sheet of the insulating sheet is energized by irradiation with the laser light at an opening edge on the one main surface side in the through-hole. A ring-shaped burr made of the thermosetting resin composition raised from one main surface is formed, and the burr is melted on the outside of the burr by the energy of the laser light irradiation and is more than the burr on the resin film. In the step of forming the ring-shaped protrusions made of the thermoplastic resin protruding to the height of the conductive paste and filling the conductive paste, the conductive paste is filled up to the height of the protrusions, It is characterized by wiping off.

  According to the method for manufacturing a wiring board of the present invention, an insulating sheet containing a thermosetting resin composition to which a resin film made of a thermoplastic resin is attached is irradiated with laser light from one main surface side through the resin film. Thus, in the step of drilling a through hole that communicates the resin film and the insulating sheet, the opening edge on the one main surface side in the through hole is raised from the one main surface of the insulating sheet by energy by laser light irradiation. Forming a ring-shaped burr made of the thermosetting resin composition, and being melted by the energy of laser light irradiation on the outside of the burr and protruding from the thermoplastic resin above the burr on the resin film Ring-shaped projections are formed, and then the conductive paste is filled from the one main surface side into the through holes communicating with the resin film and the insulating sheet. In the step, after the conductive paste is filled up to the height of the protrusion, the conductive paste is wiped up to the height of the burr, so that the height of the conductive paste protruding from the one main surface of the insulating sheet is the height of the burr. The conductive paste protruding from the one main surface of the insulating sheet is held by the burrs, so that the conductive paste does not spread or spread. Therefore, according to the method for manufacturing a wiring board of the present invention, the wiring conductor made of metal foil is pressed onto the main surface of the insulating sheet filled with the conductive paste in the through holes so as to cover the end of the conductive paste. In this case, the wiring conductor and the conductive paste are pressed against each other well, and the conductive paste does not protrude from the wiring conductor. As a result, the electrical connection reliability between the through-conductor and the wiring conductor, where the conductive paste is cured, is ensured. In addition, it is possible to provide a fine wiring substrate with excellent electrical properties and high electrical insulation reliability between adjacent wiring conductors.

  Next, a method for manufacturing a wiring board according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1A to FIG. 4M are schematic explanatory diagrams for each process for explaining a method of manufacturing a wiring board according to the present embodiment, and FIG. 5 is an enlarged view of a main part in FIG. FIGS. 6 and 6 are enlarged views of essential parts in FIG. 2D, FIG. 7 is an enlarged view of essential parts in FIG. 2E, and FIG. 8 is an enlarged view of essential parts in FIG.

  First, as shown to Fig.1 (a), the insulating sheet 1 used as the insulating layer of a wiring board and the resin film 2 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. The resin composition is impregnated and then dried or semi-cured. As the heat-resistant fiber, for example, glass fiber, aramid fiber, wholly aromatic ester fiber or the like is used, and as the thermosetting resin composition, for example, an epoxy resin, a bismaleimide triazine resin, an allyl-modified polyphenylene ether resin, or the like. Things are used. The resin film 2 has a thickness of about 10 to 30 μm, and a film made of a thermoplastic resin such as polyethylene terephthalate is used.

  Next, as shown in FIG.1 (b), the resin film 2 is stuck on the up-and-down both main surfaces of the insulating sheet 1 so that peeling is possible through the adhesion layer which is not shown in figure. Next, as shown in FIG.1 (c), the several through-hole 3 is formed in the insulating sheet 1 by which the resin film 2 was stuck on the upper and lower surfaces. The through-hole 3 is formed by placing the insulating sheet 1 with the resin film 2 stuck on the top and bottom on a flat suction table (not shown), and having an output of 5 to 9 mJ and a pulse width of 60 to 60 from the upper surface side. This is performed by irradiating the formation position of each through-hole 3 three times each with 100 μs of laser light. At this time, a laser beam having a high output of 5 to 9 mJ and a pulse width of 60 to 100 μs is irradiated, so as shown in the enlarged view of the main part in FIG. The resin film 2 and the insulating sheet 1 around the through hole 3 are softened and melted, and the ring shape is formed of a thermosetting resin composition that forms the insulating sheet 1 at the opening edge of the through hole 3 on which the laser beam is incident. The burr 1a is erected on the upper surface of the insulating sheet 1 at a height of 5 to 20 μm, and the ring-shaped protrusion 2a made of a thermoplastic resin constituting the resin film 2 is formed on the resin film 2 on the outside. It is formed at a height of 1a or more.

  Thus, the ring-shaped burr 1a made of the thermosetting resin composition constituting the insulating sheet 1 is formed at the opening edge of the through-hole 3 on the side where the laser beam is incident. The output is 5 to 9 mJ. A thermosetting resin composition softened and melted around the through-hole 3 by a high-temperature gas that is decomposed by irradiation with a long-pulse laser beam having a high output and a long pulse width of 60 to 100 μs and is ejected upward from the through-hole 3. It is inferred that this is because it is pushed upward by the pressure of the ejection. Moreover, the ring-shaped protrusion 2a made of a thermoplastic resin constituting the resin film 2 is formed on the resin film 2 outside the burr 1a at a height higher than the burr 1a because of the energy of laser light irradiation. It is presumed that the resin film 2 around the through-hole 3 melts and spreads greatly, and the melted and spread edge rises in a ring shape due to the influence of surface tension.

  If the output of the irradiated laser beam is less than 5 mJ or the pulse width of the irradiated laser beam is less than 60 μs, it is difficult to form a burr 1a having a height of 5 to 20 μm, and the irradiation is performed. When the output of the laser beam exceeds 9 mJ or the pulse width of the irradiated laser beam exceeds 100 μs, the thermosetting resin composition of the insulating sheet 1 is thermally deteriorated and the adhesiveness to the wiring conductor is reduced. Therefore, there is a risk that the wiring conductor may be peeled off in a transfer step described later. Therefore, it is preferable that the irradiated laser beam has an output of 5 to 9 mJ and a pulse width of 60 to 100 μs. Further, if the height of the burr 1a from the top surface of the insulating sheet 1 is less than 5 μm, the height of the conductive paste 4 protruding from the top surface of the insulating sheet 1 is sufficiently high with the side surfaces held by the burr 1a. In the transfer process of the wiring conductor 5 described later, the wiring conductor 5 and the conductive paste 4 are not sufficiently pressed together and the through conductor 14 is cured and the wiring conductor 5 connected thereto. The reliability of the electrical connection between the power source and the laser is reduced, and when it exceeds 20 μm, a high-energy laser having an output exceeding 9 mJ and a pulse width exceeding 100 μs in order to form a burr 1a having such a height. Light must be irradiated, and the damage to the insulating sheet 1 and the suction table on which the insulating sheet 1 is placed becomes large due to the irradiation of such high-energy laser light. Therefore, the height of the burr 1a from the upper surface of the insulating sheet 1 is preferably in the range of 5 to 20 μm.

  Next, as shown in FIG. 2 (d), the conductive paste 4 is filled into the through-hole 3 that communicates the resin film 2 and the insulating sheet 1. 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 scratching the conductive paste 4. A filling method is adopted. At this time, the conductive paste 4 filled in the through hole 3 is filled to the height of the protrusion 2a as shown in the enlarged view of the main part in FIG. The conductive paste 4 is made of, for example, a metal powder made of an alloy of tin, silver, bismuth and copper, triallyl cyanurate, triallyl isocyanurate, trisepoxypropyl isocyanurate, tris (2-hydroxyethyl) isocyanurate, etc. A triazine-based 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. Thereafter, as shown in FIG. 2 (e), the surface of the resin film 2 on the upper surface side is wiped with a dust-free cloth A to wipe away the conductive paste 4 remaining on the resin film 2 and the conductive paste filled in the through holes 3. The surface of 4 is flattened. At this time, as shown in the enlarged view of the main part in FIG. 7, the metal powder contained in the conductive paste 4 filled in the through-hole 3 is preferentially wiped off and the height of the conductive paste 4 is increased. However, a lot of small metal powder remains in the vicinity of the opening on the upper surface side of the through hole 3. Thus, if the height of the conductive paste 4 is set to a sufficient height corresponding to the height of the burr 1a and a large amount of small metal powder is left in the vicinity of the opening of the through-hole 3 of the conductive paste 4, insulation will be performed as described later. When the wiring conductor 5 made of a metal foil is transferred to the upper surface of the sheet 1, the conductive paste 4 and the wiring conductor 5 can be brought into good pressure contact with each other, and the number of contact points between them increases. As a result, the conductive paste 4 And the electrical connection reliability between the wiring conductor 5 and the wiring conductor 5 can be made extremely high.

  Next, as shown in FIG. 2 (f), the resin film 2 is peeled off from both main surfaces of the insulating sheet 1 and removed. At this time, as shown in the enlarged view of the main part in FIG. 8, the side surface of the conductive paste 4 protruding from the upper surface of the insulating sheet 1 is held by the burr 1a, so that it spreads or spreads on the upper surface of the insulating sheet 1. There is nothing. Therefore, as will be described later, when the wiring conductor 5 made of metal foil is transferred to the upper surface of the insulating sheet 1, the conductive paste 4 does not protrude from the wiring conductor 5, and as a result, the electrical connection between the adjacent wiring conductors 5 is prevented. The insulation reliability can be made high.

  Next, as shown in FIG. 3G, a wiring conductor 5 made of a metal foil such as a copper foil is detachably pasted on one main surface of a support film 6 made of a resin film such as polyethylene naphthalate. The attached transfer sheet 7 is prepared. The wiring conductor 5 on the support film 6 has a metal foil such as a copper foil attached to one main surface of the support film 6 via an adhesive material (not shown), and then the metal foil is predetermined by a photolithography technique. It is formed by etching the pattern. The thickness of the wiring conductor 5 is about 5 to 30 μm.

  Next, as shown in FIG. 3 (h), the wiring conductor 5 on the support film 6 is overlaid on the upper surface of the insulating sheet 1 so as to cover the end portion of the conductive paste 4, and is pressed and embedded by pressing, As shown in FIG. 3 (i), the wiring conductor 5 is transferred by removing the support film 6. At this time, the conductive paste 4 protruding from the upper surface of the insulating sheet 1 has a sufficient height in a state where the side surface is held by the burr 1a, and does not spread or spread on the upper surface of the insulating sheet 1. . Therefore, the wiring conductor 5 and the conductive paste 4 are in good pressure contact, and the conductive paste 4 does not protrude from the wiring conductor 5.

  Next, as shown in FIG. 4 (j), the insulating sheet 1 in which the through-hole 3 is filled with the conductive paste 4 and the wiring conductor 5 is embedded on the surface as described above is used for the manufacture of the wiring board. A plurality of sheets are prepared in a necessary form (here, the case where there are three insulating sheets 1 is shown), and as shown in FIG. 4 (k), the insulating sheets 1 are stacked vertically in a predetermined arrangement. The insulating layer 11 and the wiring conductor 5 in which the plurality of insulating sheets 1 are cured by heating and thermosetting the thermosetting resin composition of the insulating sheet 1 and the thermosetting resin composition of the conductive paste 4. And the wiring board 10 in which the upper and lower wiring conductors 5 are electrically connected by the through conductors 14 in which the conductive paste 4 is cured are obtained. At this time, as described above, since the wiring conductor 5 and the conductive paste 4 are in good pressure contact and the conductive paste 4 does not protrude from the wiring conductor 5, the through conductor 14 and the wiring conductor 5 in which the conductive paste 4 is hardened. It is possible to provide a fine wiring substrate 10 having excellent electrical connection reliability between them and high electrical insulation reliability between adjacent wiring conductors 5.

(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)-(i) is a schematic sectional drawing for every process for demonstrating the manufacturing method of the wiring board of this invention. (J), (k) is a schematic sectional drawing for every process for demonstrating the manufacturing method of the wiring board of this invention. These are the principal part enlarged views in FIG.1 (c). These are the principal part enlarged views in FIG.2 (d). These are the principal part enlarged views in FIG.2 (e). These are the principal part enlarged views in FIG.2 (f).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation sheet 1a Burr 2 Resin film 2a Protrusion 3 Through-hole 4 Conductive paste 5 Wiring conductor 10 Wiring board

Claims (3)

  A step of adhering a resin film made of a thermoplastic resin to both main surfaces of an insulating sheet containing a thermosetting resin composition in a peelable manner, and one main surface side of the insulating sheet on which the resin film is bonded Irradiating a laser beam through the resin film to form a through hole that communicates the resin film and the insulating sheet, and the one main surface in the through hole that communicates the resin film and the insulating sheet. Filling the conductive paste from the side, peeling the resin film from both main surfaces of the insulating sheet filled with the conductive paste in the through-holes, and removing the resin film Embedding a wiring conductor made of a metal foil on the main surface of the insulating sheet so as to cover an end of the conductive paste. In the step of drilling the through-hole, the thermosetting raised from the one main surface of the insulating sheet by energy by irradiation of the laser light at the opening edge on the one main surface side in the through-hole Forming a ring-shaped burr made of an adhesive resin composition, and being melted by the energy by irradiation of the laser beam on the outside of the burr, and protruding from the thermoplastic resin above the burr on the resin film In the step of forming the ring-shaped protrusion and filling the conductive paste, the conductive paste is filled up to the height of the protrusion, and then the conductive paste is wiped up to the height of the burr. Method.   The method of manufacturing a wiring board according to claim 1, wherein a height of the burr from the main surface of the insulating sheet is 5 to 20 μm. 3. The method of manufacturing a wiring board according to claim 1, wherein in the step of forming the through hole, the output of the laser beam is 5 to 9 mJ and the pulse width is 60 to 100 μs.

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