Printed wiring board and method for manufacturing the same

Abstract

To provide a printed wiring board with through-hole conductors and a method for manufacturing the same, which can reduce the number of manufacturing steps while achieving sufficient connection reliability.SOLUTION: A printed wiring board according to the present invention comprises a substrate, a through-hole formed through the substrate, a conductive paste filled within the through-hole, and a plating film formed at both ends of the conductive paste, the conductive paste is directly filled into the through-hole, and indentations are formed at both ends of the conductive paste, with a plating film formed within these indentations.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a printed wiring board having through-hole conductors containing a conductive paste, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, various shapes of printed wiring boards having through-hole conductors containing conductive paste have been known (for example, Patent Document 1). Fig. 3 is a diagram for explaining one embodiment of the printed wiring board disclosed in Patent Document 1.

[0003] In Figure 3, printed wiring board 51 has substrate 52 with through-hole 53 formed therein. A cylindrical copper-plated film 54 is formed on the inner wall of through-hole 53. Conductive paste 55 is filled inside cylindrical copper-plated film 54. Both ends of conductive paste 55 are flat, and copper-plated film 56 made of electroless copper plating and electrolytic copper plating is formed on both ends. Reference numeral 57 denotes a seed layer formed between copper-plated film 56 and substrate 52. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-251190 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technique disclosed in Patent Document 1, as shown in Fig. 3, a copper plating film 54 is formed on the inner wall of a through hole 53. This increases the number of steps in the manufacturing process. Also, as shown in Fig. 3, because both ends of conductive paste 55 are flat, the connection reliability between copper plating film 56 formed thereon and conductive paste 55 may not be sufficient. [Means for solving the problem]

[0006] The printed wiring board of the present invention includes a substrate, a through hole formed through the substrate, a conductive paste filled in the through hole, and a plating film formed on both ends of the conductive paste, wherein the conductive paste is filled directly into the through hole, and recesses are formed on both ends of the conductive paste, and the plating film is formed in the recesses.

[0007] The method for manufacturing a printed wiring board according to the present invention includes forming through holes in a copper-clad laminate, placing the copper-clad laminate with the through holes formed on a rubber support film, moving a squeegee while pressing it against the copper-clad laminate placed on the rubber support film, thereby filling the through holes with a conductive paste while the rubber support film is inserted into the through holes, filling the through holes with a conductive paste having recesses on both ends, removing the rubber support film, and forming a plating film on the copper foil of the copper-clad laminate and in the recesses of the conductive paste. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are diagrams illustrating an embodiment of a printed wiring board according to the present invention. [Figure 2A] 1A to 1C are diagrams illustrating an embodiment of a method for manufacturing a printed wiring board according to the present invention. [Figure 2B] 1A to 1C are diagrams illustrating an embodiment of a method for manufacturing a printed wiring board according to the present invention. [Figure 2C] 1A to 1C are diagrams illustrating an embodiment of a method for manufacturing a printed wiring board according to the present invention. [Figure 2D] 1A to 1C are diagrams illustrating an embodiment of a method for manufacturing a printed wiring board according to the present invention. [Figure 2E] 1A to 1C are diagrams illustrating an embodiment of a method for manufacturing a printed wiring board according to the present invention. [Figure 2F]1A to 1C are diagrams illustrating an embodiment of a method for manufacturing a printed wiring board according to the present invention. [Figure 3] 1A and 1B are diagrams illustrating an embodiment of a conventional printed wiring board. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Printed wiring board according to the present invention> An embodiment of a printed wiring board according to the present invention will be described with reference to the drawings. In the example shown in Fig. 1, the dimensions of each component, particularly the height dimension, are shown as different from the actual dimensions in order to better understand the features of the present invention.

[0010] Fig. 1 is a diagram illustrating one embodiment of a wiring conductor in a printed wiring board according to the present invention. In the example shown in Fig. 1, a printed wiring board 1 of the present invention has a substrate 2 formed with a through-hole 3 that penetrates the substrate 2. A conductive paste 4 is filled in the through-hole 3. A plating film 5 made of electroless plating and electroplating is formed on both ends of the conductive paste 4. Reference numeral 6 denotes a seed layer formed between the plating film 5 and the substrate 2.

[0011] A conventional conductive paste 4 can be used, preferably consisting of metal particles, a thermosetting resin, and a curing agent, or consisting of metal particles and a thermoplastic resin, with a solvent optionally added. If such a conductive paste contains metal particles, the metal particles are exposed by polishing the surface, and the exposed metal particles bond with the plating film 5 formed thereon, making it less likely to peel at the interface with the plating film 5 on both ends, even under harsh high-temperature, high-humidity conditions such as those in a PCT (Pressure Cooker Test).

[0012] The printed wiring board 1 according to the present invention having the above-described configuration is characterized, first, in that the conductive paste 4 is directly filled into the through-holes 3 without the need for a copper plating film as in the conventional method. This eliminates the need for a step of forming a copper plating film in the through-holes 3 during the manufacturing process, thereby reducing the number of steps. Another characteristic is that recesses 4a are formed on both ends of the conductive paste 4, and the plating film 5 is formed in these recesses 4a. This allows for a longer contact distance between the plating film 5 and the conductive paste 4 than in the conventional method, thereby improving the reliability of the connection between the plating film 5 and the conductive paste 4.

[0013] In a preferred embodiment of the printed wiring board according to the present invention, the plating film 5 is formed from electroless copper plating and electrolytic copper plating thereon. Usually, the conductive paste 4 forming the through-hole conductors and the plating film 5 forming the conductor pads on both sides are often formed from copper, which allows the performance of the printed wiring board 1 according to the present invention to be better exhibited.

[0014] <Regarding the manufacturing method of the printed wiring board according to the present invention> An embodiment of a method for manufacturing a printed wiring board according to the present invention will be described with reference to the drawings. In the example shown in Figures 2A to 2F, the dimensions of each component, particularly the height dimension, are shown as dimensions different from the actual dimensions in order to better understand the features of the present invention.

[0015] First, as shown in FIG. 2A, through-holes 14 are formed in a copper-clad laminate 13, which is formed by forming copper foil 12 (seed layer) on both sides of a substrate 11. Next, as shown in FIG. 2B, the copper-clad laminate 13 with the through-holes 14 formed therein is placed on a rubber support film 15. Next, as shown in FIG. 2C, a squeegee 16 is pressed against the copper-clad laminate 13 placed on the rubber support film 15 while being moved, thereby filling the through-holes 14 with conductive paste 17 while the rubber support film 15 is inserted into the through-holes 14. Therefore, as shown in FIG. 2D, conductive paste 17 having depressions 18 on both ends can be formed in the through-holes 14. Next, as shown in FIG. 2E, the rubber support film 15 is removed. Finally, as shown in FIG. 2F, a plating film 19 is formed on the copper foil 12 of the copper-clad laminate 13 and in the depressions 18 of the conductive paste 17 by electroless copper plating and then electrolytic copper plating, thereby completing the printed wiring board according to the present invention.

[0016] Any conventionally known method may be used to form through-hole 14. Similarly, any conventionally known method may be used to fill conductive paste 17 using squeegee 16, or to form plating film 19 by electroless copper plating and subsequent electrolytic copper plating. [Explanation of symbols]

[0017] 1. Printed wiring board 2 boards 3 through holes 4. Conductive paste 4a Depression 5. Plating film 6 Seed layer 11 Circuit Board 12 Copper foil 13 Copper-clad laminate 14 through holes 15 Rubber support film 16 Squeegee 17 Conductive paste 18 dent 19 Plating film

Claims

1. A printed wiring board, A substrate; a through hole formed through the substrate; a conductive paste filled in the through-hole; and plating films formed on both ends of the conductive paste, The conductive paste is directly filled into the through-holes, and recesses are formed on both ends of the conductive paste, and the plating film is formed in these recesses.

2. 2. The printed wiring board according to claim 1, wherein the plating film is formed by electroless copper plating and electrolytic copper plating thereon.

3. A method for manufacturing a printed wiring board, forming through holes in a copper clad laminate; placing the copper clad laminate with the through holes formed on a rubber support film; a squeegee is moved while being pressed against the copper-clad laminate placed on the rubber support film, thereby filling the through-holes with the conductive paste while the rubber support film is inserted into the through-holes, and filling the through-holes with the conductive paste having recesses on both ends; removing the rubber support film; forming a plating film on the copper foil of the copper-clad laminate and in the recesses of the conductive paste.

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