JP4389664B2 - Manufacturing method of flexible printed wiring board - Google Patents

Description

  The present invention relates to a flexible printed wiring board on which various surface-mount type electronic components are mounted and built in an electronic device, and a method for manufacturing the same.

  In recent years, as electronic devices such as mobile phones and optical disk drives become smaller and lighter, have more functions, and have higher performance, the wiring density of flexible printed wiring boards incorporated therein tends to increase. Usually, as a method of forming the wiring of the flexible printed wiring board with high density, miniaturization of a conductor pattern can be mentioned. However, there is a limit to increasing the wiring density only by miniaturizing the conductor pattern. Therefore, a method is used in which wiring is formed at a high density by laminating a plurality of conductive layers for forming a conductor pattern via an insulating layer. For electrical connection between the conductive layers, a method in which an interlayer connection portion is provided in an insulating layer between the conductive layers and the conductive layers are connected vertically is used. A flexible printed wiring board in which conductive layers are provided on both sides of the insulating layer in this manner is referred to as a double-sided flexible printed wiring board, and a flexible printed wiring board in which three or more conductive layers are provided is referred to as a multilayer flexible printed wiring board. In recent years, it has attracted attention.

  In such a flexible printed wiring board, as a method of forming an interlayer connection for connecting conductive layers, for example, a plated through hole method described in (Patent Document 1) is used. The plating through-hole method is a method in which a through-hole which is a through hole is provided in an insulating layer made of a polyimide film at the raw material stage, and a copper plating film is formed on the wall surface of the through-hole. This plated through-hole method is the most common interlayer connection method, and forms a copper base film by electroless plating on the inner wall of the through-hole formed in the insulating layer, and thick plating of copper by electrolytic plating. It consists of two main steps, and the thermal expansion coefficient of the copper plating film in the through hole and the insulating layer in which the through hole is formed are substantially the same, so it has excellent connection reliability against heat .

  However, when copper thick plating is performed, not only the thickness of the copper plating film on the inner wall of the through hole, but also the thickness of the copper foil forming the conductive layer is increased, and the fineness of the conductive pattern of the conductive layer by the subsequent etching process is increased. There was a problem that it was difficult to convert. Further, the process for forming the interlayer connection portion is multi-step and complicated, and there is a problem that productivity is lacking.

In order to solve these problems, for example, (Patent Document 2) describes a method in which paste solder containing solder particles in a through hole is printed on a predetermined portion, melted, filled into the through hole, and then solidified. Has been. According to this method, since the interlayer connection can be easily formed with less man-hours than the plated through hole method described above, the productivity is high and the interlayer connection is formed after the conductive layer is formed. The problem that the thickness of the foil increases does not occur, and the conductor pattern of the conductive layer can be miniaturized.
JP-A-5-175636 JP-A-7-176847

  However, the above conventional techniques have the following problems.

  (1) The flexible printed wiring board using the plated through-hole method described in (Patent Document 1) is excellent in connection reliability against heat, but it is difficult to miniaturize the conductor pattern and also in productivity. It had the problem of lacking.

  (2) In the flexible printed wiring board using the interlayer connection method described in (Patent Document 2), the conductive pattern of the conductive layer can be miniaturized, but the thermal expansion coefficient of the solder filled in the through hole is an insulating layer. Therefore, when heated, the solder in the through-hole expands more than the insulating layer, and the bonding interface between the conductive layer and the solder on the surface of the insulating layer easily peels off, resulting in a lack of reliability in electrical connection. Had.

  The present invention solves the above-mentioned conventional problems, and since the interlayer connection portion is formed of a composite in which solder is filled in the gap between the compacts formed by press-molding metal particles, the thermal expansion coefficient and insulation of the interlayer connection portion are reduced. Since the thermal expansion coefficient of the layers is almost the same, peeling of the bonding interface due to heating can be prevented, the electrical connection reliability is excellent, and the mechanical strength of the interlayer connection can be increased, so deformation and cracking etc. can occur An object of the present invention is to provide a flexible printed wiring board that is excellent in reliability and electrical connection reliability.

  The present invention solves the above-described conventional problems, and can produce a flexible printed wiring board with high reliability of electrical connection in a simple and few process, and is excellent in productivity, and after forming a conductive layer, an interlayer connection portion is formed. Therefore, the thickness of the conductive layer is not increased by the formation of the interlayer connection portion, the conductive pattern of the conductive layer can be miniaturized, and a flexible printed wiring board manufacturing method capable of increasing the wiring density is provided. For the purpose.

In order to solve the above problems, a method for manufacturing a flexible printed wiring board according to the present invention includes a step of forming a through hole in a predetermined portion of a double-sided wiring board in which a conductive layer is formed on both sides of an insulating layer, and then the through hole. Filling the metal particles with each other, then pressing the upper and lower surfaces of the double-sided wiring board to press the metal particles, and then applying paste solder onto the upper part of the pressure-formed molded body a step, then, characterized in that the coated solder is melted and a step of Ru to penetrate the gap between the molded body.

  As a result, a flexible printed wiring board with high electrical connection reliability can be manufactured in a simple and few process, and it is excellent in productivity, and after forming the conductive layer, the interlayer connection portion is formed. It is possible to provide a method for manufacturing a flexible printed wiring board in which the conductive pattern of the conductive layer can be miniaturized and the wiring density can be increased without increasing the thickness of the conductive layer.

According to the invention of claim 1 ,
(1) Filling through-holes with metal particles, press-molding as it is, forming solder by applying solder to the upper part, heating and infiltrating the gaps between the press-formed bodies, so electrical connection It is possible to provide a method for producing a flexible printed wiring board excellent in productivity that can produce a highly reliable flexible printed wiring board with simple and few processes.

  (2) Unlike conventional plating through-hole methods, the formation of the interlayer connection does not increase the thickness of the conductive layer, the conductive pattern of the conductive layer can be miniaturized, the wiring density can be increased, and the electronic equipment It is possible to provide a method for manufacturing a flexible printed wiring board that can be reduced in size, weight, functionality, and performance.

  (3) Since the metal particles filled in the through-holes can be pressure-formed by narrowing from above and below, a flexible printed wiring board that can easily and accurately form a press-formed body approximately the same shape as the inside of the through-hole is manufactured. A method can be provided.

In the present invention, a flexible printed wiring board with high reliability of electrical connection can be manufactured in a simple and few process, and is excellent in productivity. After forming a conductive layer, an interlayer connection is formed. The purpose of providing a method for producing a flexible printed wiring board capable of miniaturizing the conductive pattern of the conductive layer without increasing the thickness of the conductive layer and increasing the wiring density is provided on both sides of the insulating layer. A step of forming a through hole in a predetermined portion of the double-sided wiring board on which the conductive layer is formed ; a step of filling the through-hole with metal particles ; and then narrowing an upper surface side and a lower surface side of the double-sided wiring board to step and then of penetration into the gap pressure and a step of applying a solder paste on top of the molded green body, and then the green body to melt was applied solder to press molding metal particles It was achieved by providing a that step.

1st invention made | formed in order to solve the said subject is a manufacturing method of a flexible printed wiring board, Comprising: The process of forming a through hole in the predetermined part of the double-sided wiring board by which the conductive layer was formed in both surfaces of the insulating layer And then filling the through holes with metal particles , then pressing the upper surface side and lower surface side of the double-sided wiring board and press-molding the metal particles, and then on the upper part of the press-formed molded body characterized in that it comprises the steps of applying a solder paste, and then a step of Ru to penetrate the gap between the molded body is melted was coated solder.

  This configuration has the following effects.

  (1) Filling through-holes with metal particles, press-molding them as they are, forming solder joints on the top, melting and infiltrating the gaps between the press-formed bodies, so that electrical connections can be made. A highly reliable flexible printed wiring board can be manufactured with simple and few processes.

  (2) After etching the copper foil to form a conductive layer, a through hole is formed and an interlayer connection is formed in the through hole. Therefore, unlike the conventional plated through hole method, the conductive layer is formed by forming an interlayer connection. Thus, the conductive pattern of the conductive layer can be miniaturized and the wiring density can be increased.

  (3) Since the metal particles filled in the through hole can be pressure-formed by narrowing from above and below, a press-formed body having substantially the same shape as the inside of the through hole can be formed easily and with high dimensional accuracy.

  Here, the laminated wiring board may be a double-sided wiring board in which conductive layers are formed on both sides of one insulating layer, and three or more conductive layers are laminated via two or more insulating layers. There may be. In addition, as a double-sided wiring board, you may use what adhered the opposite surface of each conductive layer of the 2 single-sided wiring board by which the conductive layer was formed in the single side | surface of an insulating layer through the adhesive material. Alternatively, a laminated wiring board in which two or more single-sided wiring boards are stacked and one or more conductive layers are provided in the inner layer may be used. In this way, double-sided flexible printed wiring boards and multilayer flexible printed wiring boards with high-density wiring can be obtained by laminating single-sided wiring boards capable of miniaturizing the conductive pattern of the conductive layer into a laminated wiring board. Obtainable.

  In the through hole penetration process, a punching die, an NC drill machine, a laser processing machine, or the like is used.

  In the press-contact molding process, a predetermined amount of metal particles is filled into the interior from the upper opening of the through hole using a screen printing method, a dispenser method, or the like. In addition, as a method for press-forming metal particles, a pair of pressure plates, pressurized air, or the like that narrows the metal particles filled in the through holes from the upper and lower opening sides of the through holes is used.

In the solder application step, paste solder is applied to the upper part of the molded body inside the through-hole using a screen printing method, a dispenser method, or the like.

  In the solder infiltration step, the wiring board coated with the paste solder is heated to a temperature equal to or higher than the melting point of the paste solder and melted. In addition, after the solder penetration filling step, a step of appropriately cooling and solidifying the penetrated solder is provided.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 is a side cross-sectional view of a main part of a flexible printed wiring board according to Embodiment 1 of the present invention.

In FIG. 1, 1 is a flexible printed wiring board according to the first embodiment, 2 is an insulating layer made of a polyimide film, and 3 is a copper foil attached to the upper surface of the insulating layer 2 to form a predetermined conductor pattern. The upper conductive layer 4 is a lower conductive layer formed by etching a copper foil attached to the lower surface of the insulating layer 2 to form a predetermined conductor pattern, and 5 is an upper conductive layer 3, an insulating layer 2, and a lower conductive layer 4. A through hole provided in the through hole 5, an interlayer connection portion disposed inside the through hole 5, a compact formed by pressing the metal particles 7 a into a cylindrical shape substantially the same shape as the through hole 5, and 7 a copper , Nickel, gold, silver, or metal particles made of an alloy or a composite thereof, 8 is a solder that penetrates and fills the gaps of the molded body 7, and 8 a is an upper surface conductive layer 3 and a lower surface conductive layer 4 around the through hole 5. Solder coated on the surface of It is a membrane.

  The manufacturing method of flexible printed wiring board 1 according to the first embodiment configured as described above will be described below with reference to the drawings.

  FIG. 2 (a) is a side sectional view of a main part of a double-sided copper-clad laminate used for manufacturing the flexible printed wiring board in Embodiment 1 of the present invention, and FIG. 2 (b) is a double-sided surface on which a conductive layer is formed. FIG. 2C is a side cross-sectional view of the main part of the wiring board, FIG. 2C is a side cross-sectional view of the main part showing the through hole penetration process, and FIG. 2D is a side cross-sectional view of the main part showing the press-forming process. FIG. 2E is a side sectional view of the main part showing the solder application process, and FIG. 2F is a side sectional view of the main part showing the solder penetration filling process.

  In FIG. 2, 9 is a double-sided copper clad laminate, 10 is a copper foil, 11 is a double-sided wiring board in which the copper foil 10 is etched to form a top conductive layer 3 and a bottom conductive layer 4 having a predetermined conductor pattern, A punching die, 13 is a pressure plate, and 14 is paste solder.

  First, as shown in FIG. 2A, a double-sided copper-clad laminate 9 in which a copper foil 10 is bonded to both sides of an insulating layer 2 is prepared. As the copper foil 10, electrolytic copper foil, rolled copper foil, or the like can be used. In the first embodiment, the double-sided copper-clad laminate 9 in which the copper foil 10 is bonded to the insulating layer 2 without using the adhesive 3 is used. However, the present invention is not limited to this. It can also adhere | attach via the adhesive material which consists of synthetic resins, such as an acryl type.

  Next, as shown in FIG. 2B, an etching resist (not shown) having a predetermined shape is formed on the upper and lower surfaces of the copper foil 10, and etching is performed using a ferric chloride solution, a cupric chloride solution, or the like. Etching is performed using a liquid, and the etching resist is removed to obtain the double-sided wiring board 11 on which the upper conductive layer 3 and the lower conductive layer 4 having a predetermined conductor pattern are formed.

  Next, as shown in FIG. 2 (c), a through hole 5 is provided at a position where the upper surface conductive layer 3 and the lower surface conductive layer 4 of the double-sided wiring board 11 are electrically connected using a punching mold 12. (Through hole penetration process).

  Next, as shown in FIG. 2 (d), the metal particles 7 a are filled into the through holes 5 using a screen printing method or the like, and then the upper surface side of the double-sided wiring board 11 and the pair of pressure plates 13. The metal particles 7a filled with a narrow pressure on the lower surface side are pressed to form a cylindrical molded body 7 having the same shape as the through-hole 5 (pressure welding process).

  Next, as shown in FIG. 2E, a predetermined amount of paste-like solder 14 is applied to the upper portion of the molded body 7 inside the through hole 5 using a dispenser method or the like (solder application step).

  Next, as shown in FIG. 2 (f), the double-sided wiring board 11 coated with the paste-like solder 14 is heated to a temperature equal to or higher than the melting point of the paste-like solder 14 to melt the paste-like solder 14. It penetrates into the gap and the gap between the molded body 7 and the through hole 5 (solder penetration filling step). The molten paste solder 14 covers the surfaces of the upper conductive layer 3 and the lower conductive layer 4 to form a solder coating 8a. The infiltrated solder 8 is appropriately cooled and solidified to form the interlayer connection 6.

  In the first embodiment, metal particles 7a made only of metal such as copper are used, but instead of this, metal-coated particles in which the surfaces of particles made of synthetic resin are coated with metal, or metal particles and A mixture of metal-coated particles can also be used. As a result, the Young's modulus of the interlayer connection 6 can be reduced as compared with the case where particles made of only metal are used, and the stress caused by the difference in thermal expansion coefficient between the interlayer connection 6 and the insulating layer 2 is reduced. 6 can prevent the occurrence of peeling of the bonding interface and the like, and is excellent in the reliability of electrical connection.

  Moreover, the surface of the metal particle 7a can be previously coated with an antioxidant coating such as a gold plating coating, a solder plating coating, a rust prevention coating with a synthetic resin, or the like. Thereby, since the solder wettability on the surface of the metal particles can be improved, the molded body 7 and the solder 8 can be firmly bonded to increase the mechanical strength of the interlayer connection portion 6. Further, by applying a flux treatment for improving the solder wettability to the surface of the metal particles 7a, the bonding strength between the metal particles 7a by pressure welding is improved, the shape of the molded body 7 is stably held, and the molded body 7 It becomes easy for molten solder to penetrate into the gaps.

  As described above, the flexible printed wiring board 1 and the manufacturing method thereof according to the first embodiment are configured and thus have the following operations.

  (1) The through hole 5 is filled with a predetermined amount of metal particles 7a and directly pressed by pressure plate 13 from above and below, and paste solder 14 is applied to the upper portion and heated to form gaps in the formed body 7 Since the interlayer connection portion 6 can be formed simply by permeating, the flexible printed wiring board 1 with high electrical connection reliability can be manufactured with simple and few processes.

  (2) Since the copper foil 10 is etched to form the upper surface conductive layer 3 and the lower surface conductive layer 4, the through hole 5 is penetrated and the interlayer connection portion 6 is formed in the through hole 5. Unlike the method, the formation of the interlayer connection portion 6 does not increase the thickness of the conductive layers 3 and 4, the conductor pattern of the conductive layers 3 and 4 can be miniaturized, and the wiring density can be increased.

  (3) Since the interlayer connection portion 6 formed in the through hole 5 is formed of a composite in which the gap between the molded body 7 formed by press-molding the metal particles 7a is filled with the solder 8, the coefficient of thermal expansion of the interlayer connection portion 6 Since the thermal expansion coefficient of the insulating layer 2 is substantially the same, peeling of the bonding interface due to heating can be prevented, and the reliability of electrical connection is excellent.

  (4) Since most of the interlayer connection portion 6 is formed of the molded body 7 in which the metal particles 7a are pressed, the mechanical strength of the interlayer connection portion 6 can be increased and the occurrence of deformation or cracks can be prevented. Excellent electrical connection reliability.

  (5) Since the solder 8 is infiltrated into the gap between the molded bodies 7, the solidified solder 8 can further increase the mechanical strength of the interlayer connection portion 6, and the molded body 7 and the inner wall of the through hole 5 Since the solder 8 is also filled in the gap, the electrical connection between the conductive layers 3 and 4 can be ensured.

  (6) Since the solder coating 8a is formed on the surfaces of the upper surface conductive layer 3 and the lower surface conductive layer 4 around the through hole 5, the bonding area can be increased and the mechanical strength can be increased.

(Embodiment 2)
FIG. 3A is a side cross-sectional view of a main part of a single-sided copper-clad laminate with an adhesive used for manufacturing a flexible printed wiring board according to Embodiment 2 of the present invention, and FIG. FIG. 3 (c) is a side sectional view of a principal part showing a through hole penetration process, and FIG. 3 (d) is a side sectional view of a principal part showing a sticking process. 3 (e) is a side cross-sectional view of the main part showing the press-forming process, FIG. 4 (a) is a side cross-sectional view of the main part showing the solder application process, and FIG. 4 (b) is solder penetration. It is principal part side surface sectional drawing which shows a filling process.

  3 and 4, 15 is a single-sided copper-clad laminate with a copper foil 10 bonded to the upper surface, 16 is an adhesive layer formed on the lower surface of the single-sided copper-clad laminate 15, and 17 is an etched copper foil 10. A single-sided wiring board on which a conductive layer 3 having a predetermined conductor pattern is formed, 18 is another single-sided wiring board having a conductive layer 4 attached to the lower surface of the single-sided wiring board 17, and 19 is a single-sided wiring board 17 and another single-sided board. A laminated wiring board 20 formed by laminating the wiring board 18, a blind via hole 20 formed by closing the bottom of the through hole 5 penetrating the single-sided wiring board 17 with another single-sided wiring board 18, 21 It is the flexible printed wiring board obtained with the manufacturing method in this Embodiment 2. FIG. In addition, the thing similar to what was demonstrated in Embodiment 1 attaches | subjects the same code | symbol, and abbreviate | omits description.

  First, as shown in FIG. 3 (a), a single-sided copper clad laminate 15 having a copper foil 10 adhered to the upper surface of the insulating layer 2 and an adhesive layer 16 formed on the lower surface is prepared. As shown, the single-sided wiring board 17 having the conductive layer 3 having a predetermined conductor pattern is obtained by etching the copper foil 10 on the upper surface. Here, in general, the conductive pattern of the conductive layer 3 of the single-sided wiring board 17 can be made finer than the conductive pattern of the conductive layer of the double-sided wiring board. Usually, in the formation of the conductive pattern of the double-sided wiring board, the copper foil on both sides of the double-sided copper-clad laminate is simultaneously etched, so that the etching solution is uniformly applied from the vertical direction of the double-sided copper-clad laminate. Although it is necessary, when the etching solution is sprayed from above and below the double-sided copper-clad laminate, the etching solution after spraying on the upper surface forms a pool on the upper surface, and etching uniformity cannot be maintained. Because. Therefore, the etching conditions are unstable in the double-sided wiring board, and it is difficult to form a fine conductor pattern. On the other hand, in the formation of the conductor pattern of the single-sided wiring board, only the spraying from the lower side is required, so that the etching liquid cannot be accumulated, the etching conditions can be optimized, and the conductor pattern can be miniaturized.

  Next, as shown in FIG. 3C, a through hole 5 is provided at a position where a conductive layer 3 of a single-sided wiring board 17 and a conductive layer 4 described later are electrically connected by using a punching die 12. (Through hole penetration process).

  Next, as shown in FIG. 3 (d), another conductive layer 4 is formed on the upper surface of the insulating layer 2 'via the adhesive layer 16 on the lower surface of the single-sided wiring board 17 having the through holes 5 formed therethrough. The single-sided wiring board 18 is stuck (sticking process). As a result, the laminated wiring board 19 having the conductive layer 3 on the surface layer on the upper surface and the conductive layer 4 on the inner layer, and the blind via hole 20 in which the bottom of the through hole 5 is closed by the other single-sided wiring board 18 is formed. obtain.

  Next, as shown in FIG. 3 (e), the metal particles 7a are filled into the blind via hole 20 by using a screen printing method or the like, and then the upper surface side of the laminated wiring board 19 by the pair of pressure plates 13 The metal particles 7a filled with the lower surface side being narrowed are pressed to form a cylindrical molded body 7 having the same shape as the blind via hole 20 (pressure welding process).

  Next, as shown in FIG. 4A, a predetermined amount of paste solder 14 is applied to the upper portion of the molded body 7 inside the blind via hole 20 by using a dispenser method or the like (solder application step).

Next, as shown in FIG. 4B, the laminated wiring board 19 to which the paste-like solder 14 is applied is heated to a temperature equal to or higher than the melting point of the paste-like solder 14 to melt the paste-like solder 14. It penetrates into the gap and the gap between the molded body 7 and the blind via hole 20 (solder penetration filling step). The melted paste solder 14 covers the surface of the conductive layer 3 to form a solder film 8a. The permeated solder 8 is appropriately cooled and solidified to form the interlayer connection portion 6, and the surface conductive layer 3
A flexible printed wiring board 21 is obtained in which the conductive layer 4 and the inner conductive layer 4 are electrically connected by the interlayer connection portion 6.

  As described above, the flexible printed wiring board 21 and the manufacturing method thereof according to the second embodiment are configured, and thus have the following actions in addition to the actions of the first embodiment.

  (1) After penetrating the through-hole 5 in the single-sided wiring board 17, the blind via is simply bonded to the opposite side of the conductive layer 3 of the single-sided wiring board 17 via the adhesive 16. Holes 20 can be formed.

  (2) Since the bonding area between the inner conductive layer 4 and the interlayer connection portion 6 is increased as compared with the conventional plated through hole method, the bonding strength can be increased and the reliability of electrical connection is excellent.

  (3) The flexible printed wiring board 21 in which the wiring is formed at a high density is obtained by laminating the single-sided wiring boards 17 and 18 capable of miniaturizing the conductive patterns of the conductive layers 3 and 4 to form the laminated wiring board 19. It can be obtained easily and with less man-hours.

(Embodiment 3)
FIG. 5A is a side cross-sectional view of a main part of a single-sided copper-clad laminate used for manufacturing a flexible printed wiring board according to Embodiment 3 of the present invention, and FIG. 5B is a single side on which a conductive layer is formed. FIG. 5C is a side cross-sectional view of the main part of the wiring board, FIG. 5C is a cross-sectional side view of the main part showing the through hole penetration process, and FIG. 5D is a side cross-sectional view of the main part showing the press-forming process. 5E is a side sectional view of the main part showing the solder application process, FIG. 5F is a side sectional view of the main part showing the solder penetration filling process, and FIG. 6A is a lamination process and bonding. FIG. 6B is a side sectional view of a main part showing a multilayer flexible printed wiring board manufactured by the method for manufacturing a flexible printed wiring board in Embodiment 3 of the present invention. .

  5 and 6, 22 is a single-sided copper-clad laminate having a copper foil 10 bonded to the upper surface, 23 is a single-sided wiring board in which the conductive layer 3 having a predetermined conductor pattern is formed by etching the copper foil 10, 24. 24a, 24b, 24c, and 24d are single-sided wiring boards on which interlayer connection portions are formed, 25 is an adhesive layer, and 26 is formed by bonding the single-sided wiring board 24 and the single-sided wiring board 24a via the adhesive layer 25. A double-sided flexible printed wiring board 27 is a multilayer flexible printed wiring board formed by laminating single-sided wiring boards 24, 24 b, 24 c and 24 d with an adhesive layer 25. In addition, the thing similar to what was demonstrated in Embodiment 1 attaches | subjects the same code | symbol, and abbreviate | omits description.

  First, as shown in FIG. 5 (a), a single-sided copper-clad laminate 22 having a copper foil 10 adhered to one side of the insulating layer 2 is prepared. As shown in FIG. The single-sided wiring board 23 in which the conductive layer 3 having a predetermined conductor pattern is formed by etching the surface is obtained.

  Next, as shown in FIG. 5C, through-holes 5 are penetrated at predetermined positions penetrating the conductive layer 3 and the insulating layer 2 of the single-sided wiring board 23 using the punching mold 12 (through-holes). Penetration process).

  Next, as shown in FIG. 5 (d), the metal particles 7 a are filled into the through holes 5 using a screen printing method or the like, and then the upper surface side of the single-sided wiring board 23 and the pair of pressure plates 13. The metal particles 7a filled by narrowing the lower surface are pressed to form a cylindrical molded body 7 having the same shape as the through-hole 5 (pressure welding process). At this time, a recess (not shown) is formed in the lower pressure plate 13 so that the lower end portion of the molded body 7 protrudes from the lower surface of the insulating layer 2 by the length of the thickness of the adhesive layer 25 described later. May be.

  Next, as shown in FIG. 5E, a predetermined amount of paste-like solder 14 is applied to the upper portion of the molded body 7 inside the through hole 5 by using a dispenser method or the like (solder application step).

  Next, as shown in FIG. 5 (f), the single-sided wiring board 23 coated with the paste-like solder 14 is heated to a temperature equal to or higher than the melting point of the paste-like solder 14 to melt the paste-like solder 14. It penetrates into the gap and the gap between the molded body 7 and the through hole 5 (solder penetration filling step). Further, the permeated solder is appropriately cooled and solidified to obtain the single-sided wiring board 24 in which the interlayer connection portion 6 is formed.

  Next, as shown in FIG. 6A, two single-sided wiring boards 24 and 24a prepared as described above are prepared, and the interlayer connection portions 6 of the single-sided wiring boards 24 and 24a are connected to each other. Alignment is performed, and the opposite surfaces of each conductive layer 3 are bonded to each other through the adhesive layer 25 (lamination process). Further, the double-sided flexible printed wiring board 26 is reheated to a temperature equal to or higher than the melting point of the solder 8, the solder 8 is melted, and the respective interlayer connection portions 6 are joined (joining step). After the joining step, the double-sided flexible printed wiring board 26 having the interlayer connection portion 6 ′ in which the surface conductive layers are electrically connected is obtained by appropriately cooling and solidifying the solder 8.

  As shown in FIG. 6B, single-sided wiring boards 24, 24b, 24c, and 24d on which interlayer connection portions 6 are formed are prepared, aligned so that each interlayer connection portion 6 is connected, and an adhesive layer After laminating and pasting via 25 (lamination step), reheating is performed to melt the solder 8 to join the respective interlayer connection parts 6 (joining step). As a result, a multilayer flexible printed wiring board 27 having an interlayer connection portion 6 'in which a plurality of conductive layers on the surface layer and the inner layer are electrically connected is obtained.

  As described above, the flexible printed wiring boards 26 and 27 and the manufacturing method thereof according to the third embodiment are configured, and thus have the following operations in addition to the operations of the first embodiment.

  (1) A plurality of single-sided wiring boards 24, 24a, 24b, 24c, and 24d, each having an interlayer connection 6 formed thereon, are bonded so that each interlayer connection 6 is connected, thereby having conductive layers on the front and back surfaces. The double-sided flexible printed wiring board 26 or the multilayer flexible printed wiring board 27 having a conductive layer on the surface and the inner layer can be obtained.

  (2) Since the single-sided wiring boards 24, 24a, 24b, 24c, and 24d capable of miniaturizing the conductive pattern of the conductive layer are bonded together, a flexible printed wiring board in which wirings are formed at a high density can be easily and reduced in man-hours. Can be obtained at

  (3) Since the single-sided wiring boards 24, 24a, 24b, 24c, and 24d are bonded together, it is possible to form the interlayer connection 6 'by simply melting the solder of each interlayer connection 6 to form the interlayer connection 6'. The interlayer connection portion 6 ′ in which the surface layer and the inner conductive layer are electrically connected can be formed by only a simple process.

  The present invention relates to a flexible printed wiring board in which various surface-mount type electronic components are mounted and embedded in an electronic device, and in particular, according to the present invention, an interlayer connection portion is soldered into a gap of a molded body formed by press-forming metal particles. Since the thermal expansion coefficient of the interlayer connection portion and the thermal expansion coefficient of the insulating layer are substantially the same, it is possible to prevent peeling of the bonding interface due to heating, etc., and excellent electrical connection reliability, and In addition, since the mechanical strength of the interlayer connection portion can be increased, it is possible to provide a flexible printed wiring board that prevents the occurrence of deformation, cracks, and the like and that is excellent in electrical connection reliability.

  The present invention also relates to a method for manufacturing a flexible printed wiring board in which various surface-mount type electronic components are mounted and embedded in an electronic device. In particular, according to the present invention, flexible printed wiring with high electrical connection reliability is provided. The plate can be manufactured in a simple and few process and has excellent productivity, and after forming the conductive layer, the interlayer connection portion is formed. Therefore, the formation of the interlayer connection portion does not increase the thickness of the conductive layer. The manufacturing method of the flexible printed wiring board which can achieve refinement | miniaturization of a conductor pattern and can increase the density of wiring can be provided.

Side surface sectional drawing of the principal part of the flexible printed wiring board in Embodiment 1 of this invention (A) Main part side surface sectional drawing of the double-sided copper clad laminated board used for manufacture of the flexible printed wiring board in Embodiment 1 of this invention, (b) Main part side surface sectional drawing of the double-sided wiring board in which the conductive layer was formed , (C) Side cross-sectional view of the main part showing the through hole penetration process, (d) Side cross-sectional view of the main part showing the pressure welding forming process, (e) Side cross-sectional view of the main part showing the solder application process, (f) Solder penetration Side sectional view of the main part showing the filling process (A) Main part side surface sectional drawing of the single-sided copper clad laminated board with an adhesive used for manufacture of the flexible printed wiring board in Embodiment 2 of this invention, (b) The principal part of the single-sided wiring board in which the conductive layer was formed Side cross-sectional view, (c) Main part side cross-sectional view showing through-hole penetration process, (d) Main part side cross-sectional view showing sticking process, (e) Main part side cross-sectional view showing pressure welding molding process (A) Main part side sectional view showing a solder application process, (b) Main part side sectional view showing a solder penetration filling process (A) principal part side surface sectional drawing of the single-sided copper clad laminated board used for manufacture of the flexible printed wiring board in Embodiment 3 of this invention, (b) principal part side surface sectional view of the single-sided wiring board in which the conductive layer was formed. , (C) Side cross-sectional view of the main part showing the through hole penetration process, (d) Side cross-sectional view of the main part showing the pressure welding forming process, (e) Side cross-sectional view of the main part showing the solder application process, (f) Solder penetration Side sectional view of the main part showing the filling process (A) Main part side sectional view showing a lamination process and a joining process, (b) Main part side sectional view showing a multilayer flexible printed wiring board manufactured by the method for manufacturing a flexible printed wiring board in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flexible printed wiring board 2 Insulating layer 3 Conductive layer (upper surface conductive layer)
4 Conductive layer (lower conductive layer)
DESCRIPTION OF SYMBOLS 5 Through hole 6 Interlayer connection part 7 Molded object 7a Metal particle 8 Solder 8a Solder coating 9 Double-sided copper clad laminated board 10 Copper foil 11 Double-sided wiring board 12 Punching die 13 Pressure plate 14 Paste-like solder 15 Single-sided copper clad laminated board 16 Adhesive layer 17 Single-sided wiring board 18 Other single-sided wiring board 19 Laminated wiring board 20 Blind via hole 21 Flexible printed wiring board 22 Single-sided copper-clad laminated board 23 Single-sided wiring boards 24, 24a, 24b, 24c, 24d Single-sided wiring board 25 Adhesive layer 26 Double-sided flexible printed wiring board 27 Multilayer flexible printed wiring board

Claims (1)

Forming a through hole in a predetermined portion of a double-sided wiring board in which a conductive layer is formed on both sides of the insulating layer ;
Next, filling the through holes with metal particles ;
Then, the step of press-molding the metal particles by narrowing the upper surface side and the lower surface side of the double-sided wiring board ,
Next, a paste solder is applied to the upper part of the press-molded molded body ,
Method of manufacturing a flexible printed wiring board characterized that you and a step of Ru to penetrate the gap between the molded body is melted was coated solder then.

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