JPH0669657A - Multilayered printed wiring board - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a multilayer printed wiring board which is easily and accurately soldered inside through holes for connecting between multilayer printed circuits and has high reliability. A structure in which the outer diameter of the connecting land of the printed wiring board located in the inner layer of the inner and outer layer printed wiring boards 30, 40, 50 is made larger than the through hole diameter of the connecting land of the printed wiring board located in the outer layer, and the through hole is formed. Hall 16,
The hole diameters of 17 and 18 are made larger on the outer layer printed wiring boards 40, 50 side than on the inner layer printed wiring board 30 side, and the inner and outer layer printed wiring boards 30, 40, 50 are overlapped with a plurality of fixing screws 20. The through holes 16, 17, 18 of the printed wiring board 60 which are laminated by fixing and are laminated
After inserting a plurality of fine wires 21, the solder 22 is filled in the through holes 16, 17, 18 by the capillary phenomenon of the fine wires 21, and the printed wiring boards 30, 40, 50 are electrically connected to each other. It is characterized in that it is configured.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to 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, a multilayer printed wiring board according to the present invention is provided with a plurality of printed wiring boards provided with a printed wiring circuit having a required pattern on one side or both sides of the board and the plurality of printed wiring boards. A plurality of fixing screws for laminating and fixing the printed wiring boards through fixing holes provided at corresponding positions between the printed wiring boards and a plurality of through holes for electrically connecting the printed wiring circuits of the printed wiring boards to each other are provided. A thin wire is inserted and a connecting portion is formed by filling the through hole with molten solder by utilizing the capillary phenomenon of the thin wire.

[0008]

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

Further, the capillarity of a large number of thin wires inserted in the through hole is utilized to fill the through hole with solder to form a connecting portion.

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 layer printed wiring boards 40 and 50 are overlapped, and a plurality of fixing screws 20 are provided to fix the inner and outer layers through a plurality of fixing holes 19 formed at the relative positions of the respective printed wiring boards 30, 40 and 50. Printed wiring boards 30, 40, 50
Is fixed to form a multilayer printed wiring board 60. The plurality of fixing holes 19 and the plurality of fixing screws 20
The number of is 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 at the same time, the connection lands 14, 15 The connection portion 25 is formed by forming the shapes 23 and 24 in which the solder 13 is raised on the surface and solidifying by welding, and the required wiring circuit of the printed wiring boards 30, 40 and 50 is passed by the connection portion 25. It is possible to manufacture the multilayer printed wiring board 60 electrically connected to each other through the holes 16, 17, and 18.

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.

In the above embodiment, the multilayer printed wiring board 6 is composed of the inner and outer layer printed wiring boards 30, 40 and 50.
However, the present invention is not limited to this example.

[0024]

According to the multilayer printed wiring board of the present invention,
It is possible to simplify the production 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 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 Fixing hole 20 Fixing screw 21 thin wire 22 solder 23, 24 raised shape 25 connection part

Claims (1)

[Claims] 1. A plurality of printed wiring boards having printed wiring circuits having a required pattern provided on one or both sides of a substrate and fixing holes provided at corresponding positions between the plurality of printed wiring boards. A plurality of thin wires are inserted into the through holes for electrically connecting the printed wiring circuits of the respective printed wiring boards to each other and the fixing screws for stacking and fixing the boards to each other, and the capillary phenomenon of these thin wires is used to insert the thin wires into the through holes. A multilayer printed wiring board comprising a connecting portion formed by filling molten solder.