JPH0653658A - Multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a highly reliable multilayer printed wiring board by easily and adequately soldering the interior of a through hole connecting multilayer printed wiring circuits and the easily fixing each layer. CONSTITUTION:Diameters of through holes 11, 12 bored on the upper and lower printed wiring boards 30, 40 forming the printed wiring circuits to the front and rear surfaces of the substrates 1, 2 are set so that the diameter of the hole of the upper printed wiring board 30 is smaller than that of the lower printed wiring board 40. Moreover, the printed wiring boards 30, 40 are laminated, allowing provision of a spacer 21 at the interface other than the connecting lands 8, 9 and keeping a little clearance between the connecting lands 8, 9 and are then fixed with a plurality of screws. Moreover, after a plurality of fine leads 20 are inserted into the through holes 11, 12 of the laminated printed wiring board 50, the through holes 11, 12 are filled the solder 13 utilizing the capillary tube phenomenon of the fine lead 20 and the surfaces of the connecting lands 7, 8, 9, 10 are soldered to form a multilayer printed wiring board 50.

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, it is an object of the present invention to provide a multilayer printed wiring board which can solve such 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 multilayer printed wiring board that is electrically connected, the diameter of the through hole that is formed in each of the upper printed wiring board and the lower printed wiring board with printed wiring circuits formed on the front and back surfaces of the upper substrate and lower substrate, respectively. Interposing between the through hole formed by enlarging the lower printed wiring board side with respect to the upper printed wiring board side and the printed 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 spacer, a fixing screw for fixing the upper and lower printed wiring boards, and a screw for the upper and lower printed wiring boards. Was charged with multiple fine line in the hall, filled with solder in the through-hole by the capillary phenomenon of the thin line,
It is characterized in that it comprises a connecting portion for electrically connecting a required circuit between the respective printed wiring boards.

[0008]

According to the 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 and fixed with screws. Since the printed wiring boards are laminated by, 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 above-mentioned soldering method 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 improved in the conventional plating method. Can solve the difficulties of.

[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 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 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 multilayer printed wiring board in which required circuits of each printed wiring circuit are electrically connected through through holes drilled in each printed wiring board, the 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 that are formed each have a through hole formed by enlarging the diameter of the through hole so that the lower printed wiring board side is larger than the upper printed wiring board side. Spacers interposed between printed wiring circuit portions other than connection lands on the boundary surface of the lower printed wiring board, fixing screws for fixing the upper and lower printed wiring boards, and through holes in the upper and lower printed wiring boards. Insert multiple thin wires into the through hole and fill the through holes with solder due to the capillary phenomenon of the thin wires. Multilayer printed wiring board comprising a connection portion for electrically connecting the required circuit between the plates.