JPH0697663A - Multilayer printed wiring board - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a multilayer printed wiring board that can be manufactured without employing a through-hole plating method. [Structure] The inner and outer layer printed wiring boards 1, 4, 6 are aligned and bonded together to form a multilayer printed wiring board 15, and the printed wiring circuits 2, 3, 5, of each printed wiring board 1, 4, 6 are formed. 7 connection lands 8, 9, 10, 11
After inserting and setting the lead 25 composed of the plurality of thin wires 16 of the electronic component 23 into each of the through holes 12, 13, 14 of the electronic component 23, the through hole 12, The printed wiring circuits of the first to fourth layers are formed by filling molten solder 16 in 13 and 14 and solidifying the molten solder 16 to electrically connect the printed wiring circuits 2, 3, 5 and 7 to each other. 2, 3,
A multilayer printed wiring board 15 having inner layers 5 and 7 is formed.

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 Conventionally, a printed wiring board has been developed from a double-sided board to a multi-layer board in order to increase the density of printed wiring circuits in a printed wiring board and to reduce the size of the printed wiring board itself. It has been advanced and put into practical use.

However, regarding the production of the multi-layer PWB,
It is manufactured by the inner layer forming process, the laminating process, the through hole process, the outer layer forming process, and the post process shown in FIG.

[0004]

According to the method for manufacturing a multilayer printed wiring board described above, a connecting method via a through hole is adopted as a means for conducting each layer, and as shown in FIG. Usually, a method of conducting by through-hole plating, that is, electroless copper plating and electrolytic copper plating is carried out.

However, in such a method using through-hole plating, the plating apparatus itself is large and the equipment cost is high, and at the same time, the working environment is poor, and there are many strict requirements for the management of the plating solution itself and many environmental problems such as wastewater treatment. There is the problem of. Therefore, an object of the present invention is to provide a multilayer printed wiring board that can solve the above problems.

[0006]

In the multilayer printed wiring board of the present invention, each layer of the multilayer printed wiring board is formed by each printed wiring board and each printed wiring board is laminated and adhered to each other. In a multilayer printed wiring board configured by electrically connecting a required circuit to each printed wiring board through a through hole formed in the printed wiring board, a plurality of electronic components inserted and set in each through hole of each printed wiring board. And a solder portion for electrically connecting the connection lands of the printed wiring boards filled in the through holes by the capillary phenomenon of the plurality of thin wires of the leads.

[0007]

According to the present invention, the through-hole is conducted by filling the solder by the capillarity through the lead consisting of a plurality of twisted wires of the electronic component loaded in the through-hole, It is possible to solve various drawbacks caused by through-hole plating and provide a highly reliable multilayer printed wiring board at a low price.

[0008]

1 is a partially enlarged sectional view of a multilayer printed wiring board showing an embodiment of the present invention, and FIG. 2 is a front view of an electronic component. In FIG. 1, 1 is the first layer and the second layer on both upper and lower surfaces.
A printed wiring board (hereinafter referred to as an inner layer printed wiring board), which is positioned in the inner layer where the printed wiring circuits 2 and 3 of the layer are formed, is a third layer which is positioned and laminated on the outer layer above the inner layer printed wiring board 1. A printed wiring board on which the printed wiring circuit 5 is formed (hereinafter referred to as a first outer layer printed wiring board), 6 is formed as a fourth layer printed wiring circuit 7 which is positioned and laminated on the outer layer below the inner layer printed wiring board 1. It is a printed wiring board.

Therefore, the printed wiring circuits 2, 3, 5 and 7 of the inner and outer layer printed wiring boards 1, 4 and 6 are electrically connected to the inner and outer layer printed wiring boards 1, 4 and 6, respectively. Connection lands 8, 9, 1 for connection
0 and 11 are set in advance for each printed wiring board circuit 2, 3, 5
And 7 are arranged at corresponding positions in the circuit patterns, and through holes 12, 13 and 14 are drilled in the central portions of the connecting lands 8, 9, 10 and 11 by a method such as drilling. By doing so, the inner and outer layer printed wiring boards 1, 4 and 6 are individually formed.

The inner and outer layer printed wiring boards 1 and 4 are also provided.
In forming the connection lands 8, 9, 10 and 11 and the through holes 12, 13 and 14 of 6 and 6, the printed wirings of the first and second layers of the inner printed wiring board 1 as shown in FIG. The outer diameters of the connection lands 8 and 9 of the circuits 2 and 3 are set to the through holes 13 of the connection lands 10 and 11 of the first and second outer layer printed wiring boards 4 and 6, respectively.
The diameter of each of the through holes 13 and 14 of the connecting lands 10 and 11 of the first and second outer layer printed wiring boards 4 and 6 is set to be larger than that of the connecting lands 8 and 9 of the inner layer printed wiring board 1. It is formed by making the diameter larger than the diameter of the through hole 12 (at least 0.2 mm or more larger than the diameter of the through hole 12).

Therefore, according to the above-mentioned construction conditions, the inner and outer layer printed wiring boards 1, 4 and 6 are manufactured by a conventionally known method. Using the laminated laminate, the copper foils on both sides are etched to form the printed wiring circuits 2 and 3 of the first and second layers having the connection lands 10 and 11 and to be drilled. The first and second outer layer printed wiring boards 4 and 6 are formed by punching through holes 12 and similarly the third and fourth layers having connecting lands 10 and 11 are formed by using a single-sided copper clad laminate. The printed wiring circuits 5 and 7 of the layer are formed and the through holes 13 and 14 are formed by processing and punching, respectively.

Thereafter, the inner and outer layer printed wiring boards 1, 4 and 6 are laminated and bonded as shown in FIG.

That is, as shown in FIG. 1, the first outer layer printed wiring board 4 is laminated on the upper side of the inner layer printed wiring board 1, and the second outer layer printed wiring board 6 is laminated on the lower side thereof.
Connection lands 8, 9, 1 of each printed wiring circuit 2, 3, 5 and 7 of each inner / outer layer printed wiring board 1, 4 and 6
0 and 11 and their through holes 12, 13 and 14
A mass lamination method using a prepreg can be mentioned as a joining method for laminating the inner and outer layer printed wiring boards 1, 4 and 6 while arranging the center of each of them, and bonding the inner and outer layer printed wiring boards 1, 4 and 6.

That is, this method relates to the alignment of the inner and outer layer printed wiring boards 1, 4 and 6,
After a prepreg (not shown) is interposed between the inner and outer layer printed wiring boards 1, 4 and 6, they are laminated under heating and pressure. It should be noted that it is also possible to implement using other bonding methods.

After the inner and outer layer printed wiring boards 1, 4 and 6 have been laminated and adhered to each other as described above, as shown in FIG.
To fourth layer printed wiring board circuits 2, 3, 5 and 7
The four-layer printed wiring board 15 can be manufactured by electrically connecting each circuit through the connection lands 8, 9, 10 and 11.

Thus, the connection lands 8, 9, 10
The electrical connection of Nos. 11 and 11 is carried out by adopting the soldering method instead of the conventional plating method.

That is, as shown in FIG. 1, the through holes 12, 1 of each of the connection lands 8, 9, 10 and 11 are connected.
3 and 14 a plurality of conductive wires 1 of the electronic component 23
After the lead 25 composed of the stranded wire 6 is inserted and set, the molten solder 17 is filled into the through holes 12, 13 and 14 by utilizing the capillary phenomenon of the plurality of fine wires 16 of the lead 25. At the same time, by solidifying the solder 17, the connection lands 8, 9, 10 and 11 can be electrically connected.

Further, as a method of filling the through holes 12, 13 and 14 with the molten solder 17 into the through holes 12, 13 and 14 by utilizing the capillary phenomenon of the lead 25 composed of the plurality of fine wires 16 of the electronic component 23, after the bonding, the through holes are formed. Solder tanks (not shown) filled with molten solder in each of the inner and outer layer printed wiring boards 1, 4 and 6 in which the leads 25 made of the twisted wires of the plurality of fine wires 16 of the electronic component 23 are set in 12, 13, and 14 respectively. As an example thereof, a method of carrying out dipping in water can be mentioned.

A more specific method of this method will be described below. As described above, the printed wiring boards 1 and 4 for the inner and outer layers
1 and 6 (hereinafter, each printed wiring board after lamination is simply referred to as a multilayer board) through holes 12, 13 and 14 are provided with leads 25 formed of twisted wires of a plurality of fine wires 16 of an electronic component 23 as shown in FIG. Is charged and set. And
A conductive material such as copper is used for the thin wire 16 of the lead 25. For example, when the diameter of the through hole 12 is 0.8 mm, the diameter of the thin wire 16 is about 50 to 100 μmφ.
Lead 2 formed by twisting about 0 to 30 thin wires 16
5 is inserted into the through hole 12. In this case, it is preferable that the surface of each of the thin wires 16 is flux-treated. In addition, as each thin wire 16, the product name "Winking Wire CP-1515" (manufactured by Taiyo Denki Sangyo Co., Ltd.)
Manufactured) can be used. Such through hole 12
A small gap is formed between the thin wires 16 of the lead 25 inserted therein, and the gap forms a capillary state between the thin wires 16.

After loading the lead 25 composed of the twisted wires of the plurality of thin wires 16 as described above, the multilayer board is immersed in a solder bath (not shown). The solder bath is filled with the molten solder kept at around 260 ° C., and the molten solder enters the through holes 12, 13 and 14 by being immersed in the solder bath. At the time of this intrusion, the molten solder is smoothly absorbed in the through holes 12, 13 and 14 due to the capillary phenomenon between the thin wires. As a result, the inside of each of the through holes 12, 13 and 14 has a lead 25 formed by twisting a plurality of thin wires 16.
Further, it is filled with molten solder, and is filled in a state of being raised above both connection lands 10 and 11 as shown in FIG. The immersion of the multilayer board in the solder bath is performed by immersing the surface opposite to the set surface of the electronic component 23,
About 5 seconds is preferable because thermal damage to each printed wiring board 1, 4 and 6 is prevented, and even in such a short time immersion, the molten solder is smoothly filled by the capillary phenomenon between the thin wires 16. Therefore, the molten solder can be filled in the through holes 12, 13 and 14.

The through holes 12, 13 and 14 of the multi-layer board pulled up from the solder bath are filled with the leads 25 and the solder 17 each consisting of a stranded wire of a plurality of thin wires 16, and the solder 17 is the surface of the connection lands 10, 11. It is in good contact with the connection lands 8 and 9 in a raised state. As a result, the connection lands 8, 9, 10 and 11 are electrically connected to each other via the solder 17 and the leads 25, and reliable conduction is achieved.

In this embodiment, the through hole 1
Inserting the lead 25 of the electronic component 23 into the 2, 13, and 14 → connecting lands 8, 9, 10 only by immersing in the solder bath
And 11 can be made conductive. Therefore, without complicated processing such as plating, printing, and soldering,
Conduction between lands is possible, which enables rapid and large-scale processing. Further, since the solder is absorbed in the through hole by the capillary phenomenon, a sufficient amount of solder can be filled into the through hole with certainty, which allows connection with improved reliability of the conduction resistance.

The electronic component 23 is to be mounted on the multilayer printed wiring board 15, and as shown in FIG. 2, a package body 24 accommodating ICs, LSIs and other chips.
And a plurality of thin wires 16 drawn from the package body 24.
And a plurality of leads 25 each composed of a twisted wire
5 (one lead 25 in the figure) is the multilayer printed wiring board 1
5 through holes 12, 13 and 14 are mounted and mounted. Further, the plurality of thin wires 16 forming the leads 25 are arranged with a pitch such that the capillary phenomenon is exhibited, and the capillary phenomenon absorbs the solder into the through holes. As a result, the solder is filled into the through hole and the lead 25 is fixed, so that there is an advantage that the electronic component 23 can be mounted and the connection lands 8, 9, 10, and 11 can be simultaneously connected. is there.

As described above, the multilayer (4
Layer) The printed board 15 can be manufactured. In the above description, after the individual forming steps of the printed wiring boards 1, 4 and 6, the mutual alignment and laminating processing steps of the respective printed wiring boards 1, 4 and 6 are performed, and then the connection lands 8, The method of performing the connection processing steps of 9, 19 and 11 has been described. Prior to this connection processing step, the first and second outer layer printed wiring boards 4 and 6 are provided.
The portions other than the connecting lands 10 and 11 of the printed wiring circuits 5 and 7 required for the connection processing step are covered with the solder resists 26 and 27, and necessary marking (not shown) printing or the like is performed.

After that, necessary outer shape processing and surface treatment after flux application, and other necessary processing and treatment are performed to complete the formation processing of the multilayer board. Then, after that, the above-mentioned connection processing is performed on this multilayer board.

From the above description, the multi-layer (4
Layer) The printed wiring board 15 can be manufactured. However, in the manufacturing method, the structure and the forming method of the inner and outer layer printed wiring boards 1, 4 and 6 are not limited to this, and the structure and the forming according to the design of the pattern or the like required for each layer can be appropriately performed. It can be carried out by a method. As a matter of course, the structure of the four-layered multilayer printed wiring board 15 and the manufacturing method itself are not limited to those in the above-described embodiment, and the same operational effects are obtained in the manufacture of a multilayer printed wiring board other than four layers. In the above-described embodiment, the through holes 12, 13 and 14 associated with the individual formation steps of the printed wiring boards 1, 4 and 6 of the inner and outer layers are individually formed. Instead of the punching process, the punching process can be performed by a drill or the like even after the laminating process by laminating the printed wiring boards 1, 4 and 6 together.

For example, with respect to the inner layer printed wiring board 1, after forming the printed wiring circuits 2 and 3 with a required pattern, the through hole 12 is punched after the step of laminating with the other printed wiring boards 4 and 6. In addition, the first and second outer layer printed wiring boards 4 and 6 can be processed before and after bonding, and the same applies to the formation of the printed wiring circuits 5 and 7. Similarly, other multilayer printed wiring boards can be manufactured while changing the design of various processing steps.

As is apparent from the above-mentioned embodiment, the electrical connection between the printed wiring circuits 2, 3, 5 and 7 of each layer can be achieved by the soldering method, not by the plating method. In addition to reducing the equipment cost, improving the working environment and management, and solving the problems in environmental hygiene, the connection lands 8, 9, 10 and 11 are connected by soldering. The outer diameters of the connecting lands 8 and 9 are the connecting lands 10 and 11.
The diameter of the through holes 13 and 14 is larger than the diameter of the through holes 12 of the connecting lands 8 and 9,
By increasing the diameters of the through holes 13 and 14 of the connection lands 10 and 11, conventionally, the connection area is limited by the thickness of the copper foil of each circuit (in the case of connection by through hole plating). Through hole 1 compared to
The surface area of the connection lands 8 and 9 exposed in the openings of the holes 3 and 14 is the contact area of the solder 17 added to the thickness of the copper foil, and the reliability of the continuity due to the soldering in the same portion is improved. It can be improved. In particular,
When forming the solder part that connects the connection lands of the printed wiring board that forms each layer, the lead of the electronic component that exerts a capillary action in the through hole consists of multiple twisted wires, and It can be expected that the solder is filled without variation.

[0029]

According to the multilayer printed wiring board of the present invention, the manufacturing of such a printed wiring board can be simplified, the cost can be reduced, and the reliability of the quality can be improved.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of a multilayer printed wiring board according to the present invention.

FIG. 2 is a front view of an electronic component used in the multilayer printed wiring board of the present invention.

FIG. 3 is an explanatory view showing a conventional method for manufacturing a multilayer printed wiring board.

[Explanation of symbols]

 1 Inner Layer Printed Wiring Board 2,3 First and Second Layer Printed Wiring Circuits 4,6 First and Second Outer Layer Printed Wiring Boards 5,7 Third and Fourth Layer Printed Wiring Circuits 8,9,10 , 11 Connection land 12, 13, 14 Through hole 15 Multi-layer printed wiring board 16 Fine wire 17 Solder 23 Electronic component 24 Package body 25 Lead 26, 27 Solder resist

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 3/32 R 9154-4E

Claims (1)

[Claims] 1. A connection in which each layer of a multilayer printed wiring board is formed by each printed wiring board, each printed wiring board is laminated and laminated, and required circuits of each printed wiring board are arranged on each printed wiring board. In a multi-layer printed wiring board configured by electrically connecting a land for through through a through hole, a lead formed by twisting a plurality of thin wires of an electronic component loaded and set in each through hole of each printed wiring board. And a solder portion for electrically connecting the respective connection lands of the respective printed wiring boards filled in the through holes by the capillary phenomenon of a plurality of thin wires of the lead.