JPH0669650A - Manufacture of multilayered printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a method by which soldering can be easily performed in a through hole for connecting multilayered printed circuits to each other and a highly reliable multilayered printed wiring board can be obtained. CONSTITUTION:The outside diameter of the connection land of the innermost printed wiring board of inner- and outer-layer printed wiring boards 30, 40, and 50 is made larger than the diameter of the through hole of the connection land of the outermost printed wiring board and, at the same time, the diameters of through holes 16, 17, and 18 are made larger on the boards 40 and 50 sides against the board 30 side. In addition, a laminated printed wiring board 60 is formed by piling up the boards 30, 40, and 50 and fixing the boards 30, 40, and 50 to each other with a plurality of screws 20. After installing a plurality of thin wires 21 in the holes 16, 17, and 18 of the board 60, the holes 16, 17, and 18 are filled up with solder 22 by utilizing the capillary actions of the wires 21 and the boards 30, 40, and 50 are electrically connected to each other. Thus the title board is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board.

[0002]

2. Description of the Related Art In recent years, with the increase in the density of printed wiring circuits and the miniaturization of printed wiring boards themselves,
In order to meet the demand, a printed wiring board has been developed from a double-sided board to a multilayer board and has been put into practical use.

However, in the manufacture of a multilayer printed wiring board, the inner layer forming step, the laminating step, the through-hole step, the exterior forming step and the subsequent steps shown in FIG.

[0004]

According to the method for manufacturing a multilayer printed wiring board described above, when laminating each layer, a prepreg or an adhesive is used between the layers, and complicated processing such as heating and pressing is performed. Has been given.

Further, as a means for conducting each layer, a connection method via a through hole is adopted, and
Usually, the method of conducting is performed by through-hole plating, that is, electroless copper plating and electrolytic copper plating.

However, in such a method for manufacturing a multilayer printed wiring board, the lamination process is complicated, and in the method using through-hole plating, the plating apparatus itself is large-scaled, so that the equipment cost increases and at the same time the working environment is increased. Unfortunately, there are many strict requirements for the management of the plating solution itself and many environmental problems such as wastewater treatment. Therefore, an object of the present invention is to provide a method for manufacturing a multilayer printed wiring board which can solve the above problems.

[0007]

In order to achieve the above object, the present invention is to stack printed wiring boards, and to provide a required circuit of each printed wiring circuit through a through hole formed in each printed wiring board. In the method of manufacturing a multilayer printed wiring board that is electrically connected, in each of the printed wiring boards, the outer diameter of the connection land of the printed wiring board located in the inner layer is the through diameter of the connection land of the printed wiring board located in the outer layer. While opening a hole larger than the hole diameter, the printed wiring boards are stacked and fixed with a plurality of screws,
Further, after inserting a plurality of thin wires into the through holes of the laminated printed wiring boards, the through holes are filled with solder by the capillary phenomenon of the thin wires to electrically connect required circuits between the printed wiring boards. It is characterized by connecting and manufacturing.

[0008]

According to the method for manufacturing a multilayer printed wiring board of the present invention, the printed wiring board is formed by stacking a plurality of printed wiring boards having printed wiring circuits formed on one surface or the front and back surfaces of the board and fixing them with screws. Since they are laminated, it is easy to fix each layer.

Also, the solder can be filled in the through hole by sucking the solder into the through hole by utilizing the capillary phenomenon of a large number of thin wires inserted in the through hole.

As described above, it is possible to provide a multilayer printed wiring board which has a simple lamination method, solves various drawbacks caused by through-hole plating, and has a low cost and high reliability.

[0011]

1 is a partially enlarged sectional view of a multilayer printed wiring board showing an embodiment of the present invention. The printed wiring circuits 4, 5, 6, and 7 are formed on the front and back surfaces of the inner layer substrate 1 and on one surface of the outer layer substrates 2 and 3 by a normal method.

Further, the inner layer substrate 1 and the outer layer substrates 2, 3 are provided with connection lands 12, 13, 14, 15 for electrically connecting the required wiring circuits to each other. Through holes 16, 17, and 18 are drilled in the central portions of 13, 14, and 15 by a method such as drilling.

Then, the connecting lands 12, 13, 14,
The inner layer printed wiring board 30 and the outer layer printed wiring boards 40 and 50 are formed by applying the solder resists 8, 9, 10, 11 excluding the surface on which the solder is welded at 15. The through holes 16, 17 and 18 have a diameter larger than that of the through hole 16 on the inner layer printed wiring board 30 side.
Through hole 1 on the outer printed wiring boards 40 and 50 side
Increase the diameter of 7,18.

The inner layer printed wiring board 3 having the above structure
0 and the outer printed wiring boards 40 and 50 are superposed, and the printed wiring boards 30 of the inner and outer layers are fixed by a plurality of screws 20 through a plurality of reference holes 19 formed in each of the printed wiring boards 30, 40 and 50. , 40, 50 are fixed to form a multilayer printed wiring board 60. The numbers of the plurality of reference holes 19 and the plurality of screws 20 are not limited.

Then, a plurality of thin wires 21 made of a conductive material such as copper are placed inside the through holes 16, 17, 18 of the multilayer printed wiring board 60 laminated as described above and filled with molten solder. By immersing the multilayer printed wiring board 60 in (not shown), the solder 22 is formed into a through hole 16 due to the phenomenon of a capillary tube formed by a plurality of thin wires 21.
It is sucked into the inside of 17,18.

The thin wires 21 are through holes 16 and 1.
If the diameter of the through hole 16 is 0.8 mm, the diameter of the fine wire 21 is 50 to 50 mm.
It is about 100 μmΦ, and the surface thereof is preferably flux-treated, but about 10 to 30 pieces are inserted into the through holes 16, 17, and 18. This thin line 2
The product name is “Wicking Wire CP-15”.
15 "(manufactured by Taiyo Sangyo Co., Ltd.) can be used.

The molten solder in the solder bath is about 260
The temperature is kept at ° C, and soldering is performed by immersing the multilayer printed wiring board 60 for about 5 seconds (immersion time within a range that prevents thermal damage).

When the multilayer printed wiring board 60 is pulled up from the solder bath, the situation in which soldering is completed for each land through the through holes 16, 17, 18 is as follows.
As shown in FIG. 1, due to the capillary phenomenon of the thin wire 21, the solder 22 is sufficiently spread inside the through holes 16, 17, 18 and is welded to the surfaces of the connection lands 12, 13 and the connection lands 14, 15 When the solder 13 forms the raised shapes 23 and 24 on the surface and is welded and solidified, the required wiring circuits of the printed wiring boards 30, 40 and 50 are electrically connected to each other through the through holes 16, 17 and 18. It is possible to manufacture the multilayer printed wiring board 60 connected to the.

The diameters of the through holes 16, 17, 18 on the outer layer printed wiring board 40, 50 side are larger than those on the inner layer printed wiring board 30 side. By internally increasing the exposed area of the connection lands 12 and 13 between layers, the connection area is conventionally limited by the thickness of the copper foil of each circuit (in the case of connection by through hole plating). Compared with this, soldering to the surfaces of the connection lands 12 and 13 is facilitated.

According to this embodiment, the multilayer printed wiring board 6
In the laminating method of 0, since no prepreg or adhesive is used as in the conventional case, laminating can be performed by a simple fixing method without performing heating and pressure processing with a hot plate.

Further, the inside of the through holes 16, 17 and 18 can be easily filled with the solder 13, and the soldering to the surfaces of the connecting lands 12 and 13 located on the through hole 16 can be facilitated. As a result, the soldering is surely performed, and the reliability of conduction can be improved.

Further, by using the soldering method of the present invention as a method for electrically connecting through the through holes 16, 17, 18, the equipment cost is reduced and the work environment and management are reduced when the conventional plating method is used. It is possible to solve the problems of environmental improvement and environmental hygiene.

The configuration and number of each printed wiring board forming the multilayer printed wiring board are not limited to those in the above-mentioned embodiment.

[0024]

According to the method for manufacturing a multilayer printed wiring board of the present invention, it is possible to simplify the manufacturing of this type of printed wiring board, reduce the cost, and improve the reliability of the product.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a multilayer printed wiring board according to a manufacturing method of the present invention.

FIG. 2 is an explanatory view showing a conventional method for manufacturing a multilayer printed wiring board.

[Explanation of symbols]

 1 Inner layer board 2, 3 Outer layer board 4, 5, 6, 7 Printed wiring circuit 8, 9, 10, 11 Solder resist 12, 13, 14, 15 Connection land 16, 17, 18 Through hole 19 Jig hole 20 Screw 21 thin wire 22 solder 23, 24 raised shape

Claims (1)

[Claims] 1. Laminating each printed wiring board,
In a method of manufacturing a multilayer printed wiring board, wherein required circuits of each printed wiring circuit are electrically connected through through holes punched in each printed wiring board, the printed wiring located in an inner layer of each printed wiring board. The outer diameter of the connection land of the board is larger than the through hole diameter of the connection land of the printed wiring board located in the outer layer, and the printed wiring boards are superposed and fixed with a plurality of screws, and further, After inserting a plurality of thin wires into the through holes of the laminated printed wiring boards, the through holes are filled with solder by the capillary phenomenon of the thin wires to electrically connect required circuits between the printed wiring boards. A method for manufacturing a multilayer printed wiring board, comprising: