JPH0653657A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a method of manufacturing a multilayer printed wiring board which is highly reliable and is capable of easily and accurately soldering the insides of through holes for connecting between multilayer printed circuits. [Structure] The diameters of the through holes 11 and 12 formed in the upper and lower printed wiring boards 30 and 40 having printed wiring circuits formed on the front and back surfaces of the respective boards 1 and 2 are set to the upper printed wiring board 3
The lower printed wiring board 40 side is made larger than the 0 side, and the spacer 2 is provided on the boundary surface other than the connection land portions 8 and 9.
1 through which the connection land portions 8 and 9 are overlapped with each other while keeping a slight gap therebetween, and the plurality of through holes 11 and 12 of the laminated printed wiring board 50, which are laminated by fixing with a plurality of screws. After inserting multiple thin wires 20 into
The connecting holes 7, 8, 9, 1 are filled with the solder 13 in the through holes 11, 12 by the capillary phenomenon of the thin wires 20.
It is characterized in that the multilayer printed wiring board 50 is manufactured by soldering on the surface of 0.

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 a method of manufacturing a multilayer printed wiring board that is electrically connected, a hole diameter of a through hole formed in each of an upper printed wiring board and a lower printed wiring board, in which printed wiring circuits are formed on the front and back surfaces of the upper substrate and the lower substrate, respectively. And make the lower printed wiring board side larger than the upper printed wiring board side,
By interposing a spacer in the wiring circuit portion other than the connection land portion on the boundary surface between the upper printed wiring board and the lower printed wiring board, a small gap is provided between the connection land portions on the boundary surface so that they are overlapped. Laminated by fixing with screws, and after inserting a plurality of fine wires into the through holes of the upper and lower printed wiring boards,
It is characterized in that the through-hole is filled with solder by the capillary phenomenon of the thin wire, and a required circuit between each printed wiring board is electrically connected to manufacture.

[0008]

According to the method for manufacturing a multilayer printed wiring board of the present invention, the upper printed wiring board and the lower printed wiring board having the printed wiring circuits formed on the front and back surfaces of the upper substrate and the lower substrate are superposed on each other with screws. Since the printed wiring boards are laminated by fixing, the fixing is easy.

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.

Further, since a spacer is interposed at the boundary surface between the upper and lower printed wiring boards to form a slight gap between the connecting lands located between the layers, the molten solder easily flows into the gap. At the same time, since the hole diameter of the through hole is larger on the lower printed wiring board side than on the upper printed wiring board side, the exposed area of the connection land in the through hole is large, and soldering to the surface of the connection land is performed. Will be easier.

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.

[0012]

1 is a partially enlarged sectional view of a multilayer printed wiring board showing an embodiment of the present invention. Printed wiring circuits 3, 4, 5 and 6 are formed on the front and back surfaces of the upper substrate 1 and the lower substrate 2 by a normal method, and required wiring circuits of the upper substrate 1 and the lower substrate 2 are electrically connected to each other. Connection lands 7, 8, 9, 10 for connection to the connection lands are formed, and through holes 11, 12 are drilled in the central portions of the connection lands 7, 8, 9, 10 respectively by a method such as drilling. , The upper substrate 1 and the lower substrate 2 are connected to the front and back surfaces of the connection lands 7 and 8 for welding solder.
Solder resists 14, 15, 1 excluding 9 and 10 surfaces
By applying steps 6 and 17, the upper printed wiring board 30 and the lower printed wiring board 40 are formed.

The diameters of the through holes 11 and 12 are larger than the diameter of the through hole 11 on the lower printed wiring board 40 side as compared with the diameter of the through hole 11 on the upper printed wiring board 30 side.

Then, a thickness of 0.1 to 0.3 is formed on the portion other than the connection lands 8 and 9 located on the boundary surface between the upper printed wiring board 30 and the lower printed wiring board 40 having the above-mentioned structure.
By interposing a spacer 21 having a size of about mm, the connection lands 8 and 9 are overlapped with each other while keeping a gap therebetween,
A multilayer printed wiring board 50 is set by fixing the upper and lower printed wiring boards 30, 40 with a plurality of screws 19 through a plurality of reference holes 18 formed in each of the printed wiring boards 30, 40. The numbers of the plurality of reference holes and the plurality of screws 19 are not limited.

As a method of interposing the spacer 21, a film-like one is used in consideration of the insulation of the wiring circuits 4 and 5 located on the boundary surface when the upper and lower printed wiring boards 30 and 40 are superposed. , The connection lands 8 and 9 located at the through holes 11 and 12 can also be inserted.

Then, a plurality of thin wires 20 made of a conductive material such as copper are inserted into the through holes 11 and 12 of the multilayer printed wiring board 50 laminated as described above, and the multilayer printed wiring board 50 is melted with solder. Solder tank filled (not shown)
The solder 13 is sucked into the through holes 11 and 12 by the phenomenon of a capillary tube formed by the plurality of thin wires 20 by immersing in the through holes 11 and 12.

The thin wire 20 has through holes 11 and 12.
The diameter of the fine wire 20 is 50 to 100 μ if the diameter of the through hole 11 is 0.8 mm.
It is about mΦ, and it is preferable that the surface is fluxed, but about 10 to 30 wires are used as the through hole 1.
Insert inside 1,12. As the thin wire 20, a trade name “Wicking Wire CP-1515” (manufactured by Taiyo Sangyo Co., Ltd.) can be used.

The molten solder in the solder bath is about 260
The temperature is maintained at ° C, and soldering is performed by immersing the multilayer printed wiring board 50 for about 5 seconds (immersion time within a range that prevents thermal damage).

When the multilayer printed wiring board 50 is pulled up from the solder bath, the soldering to the respective lands via the through holes 11 and 12 is completed, as shown in FIG. Due to the capillarity phenomenon, the solder 13 is sufficiently spread inside the through holes 11 and 12, and is welded to the surfaces of the connection lands 8 and 9, and the connection lands 7 and 1
On the surface of 0, the solder 13 has a raised shape and is welded and solidified so that the required wiring circuits of the printed wiring boards 30 and 40 are electrically connected to each other through the through holes 11 and 12. The multilayer printed wiring board 50 can be manufactured.

The diameters of the through holes 11 and 12 are made larger on the lower printed wiring board 40 side than on the upper printed wiring board 30 side.
By increasing the exposed area of the connection lands 8 and 9 between layers internally, 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). This facilitates soldering to the surfaces of the connection lands 8 and 9.

According to this embodiment, the multilayer printed wiring board 5
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 11, 12 can be easily filled with the solder 13, and the through holes 11,
Since the soldering is easily performed on the surfaces of the connection lands 8 and 9 located inside 12, the soldering is surely performed,
The reliability of conduction can be improved.

Furthermore, by using the soldering method of the present invention as a method for electrically connecting through a through hole, the facility cost can be reduced, the working environment and management can be improved, and environmental hygiene can be achieved by the conventional plating method. Can solve the above difficulties.

[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 shows 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 Upper Substrate 2 Lower Substrate 3, 4, 5, 6 Printed Wiring Circuit 7, 8, 9, 10 Connection Land 11, 12 Through Hole 13 Solder 14, 15, 16, 17 Solder Resist 18 Jig Hole 19 Screw 20 Fine Wire 21 Spacer

Claims (1)

[Claims] 1. Laminating each printed wiring board,
In a method for manufacturing a multilayer printed wiring board in which required circuits of each printed wiring circuit are electrically connected through through holes punched in each printed wiring board, printed wiring circuits are provided on the front and back surfaces of the upper substrate and the lower substrate, respectively. The upper printed wiring board and the lower printed wiring board are formed with through holes each having a hole diameter larger on the lower printed wiring board side than on the upper printed wiring board side, and the upper printed wiring board and the lower printed wiring board are formed. By interposing a spacer in the wiring circuit portion other than the connection land portion on the boundary surface of the above, a small gap is provided between the connection land portions on the boundary surface, and they are stacked and fixed by a plurality of screws. In addition, after inserting a plurality of fine wires into the through holes of the upper and lower printed wiring boards, Filling the solder into the through-hole by a pipe phenomenon, a method for manufacturing a multilayer printed circuit board, characterized in that to produce electrically connecting the required circuit of the printed circuit plates.