JPH05315762A - Multilayer printed circuit board - Google Patents

Abstract

PURPOSE:To provide a multilayer printed circuit board which can be manufactured without employing a through hole plating method. CONSTITUTION:A multilayer printed circuit board 15 is formed by laminating inner and outer layer printed circuit boards 1, 4, 6 while aligning them, and leads 25 of a plurality of small-gage wires 16 of an electronic component 23 are charged in through holes 12, 13, 14 of connecting lands 8, 9, 10, 11 of printed circuits 2, 3, 5, 7 of the boards 1, 4, 6. Melted solders 16 are filled in the holes 12, 13, 14 by utilizing capillarity of the leads 25 of the plurality of the wires 16 of the component 23, and the solders are solidified to electrically connect the circuits 2, 3, 5, 7, thereby constituting the multilayer printed circuit 15 in which the circuits 2, 3, 5, 7 from the first to fourth layers are formed as inner layers.

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 a printed wiring circuit 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, the method of conducting is performed by through-hole plating, that is, electroless copper plating and electrolytic copper plating.

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 which can solve such problems.

[0006]

A multilayer printed wiring board according to the present invention has a structure in which each layer of the multilayer printed wiring board is formed by each printed wiring board and the printed wiring boards are laminated and bonded 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, a printed wiring board positioned in an inner layer among the printed wiring boards forming each layer. The outer diameter of the connecting land is larger than the through hole diameter of the connecting land of the printed wiring board located in the outer layer, and the through hole diameter of the connecting land of the printed wiring board located in the outer layer is located in the inner layer. Providing a connecting land with a diameter larger than the through-hole diameter of the connecting land of the printed wiring board, and perforating each of the printed wiring boards. In each of the through holes, a lead consisting of a plurality of fine wires of the electronic component is inserted, and the solder is filled in the through hole by the capillary phenomenon of the plurality of fine wires of the lead, and in the lead and the through hole of the electronic component. It is characterized in that a required circuit between each printed wiring board is electrically connected with the filled solder.

[0007]

According to the present invention, the conduction of the through holes is achieved by filling the solder by the capillarity phenomenon through the leads consisting of a plurality of fine wires of the electronic parts loaded in the through holes, and thereby conducting the through holes. It is possible to provide a multilayer printed wiring board that solves various drawbacks of the above and has high reliability 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. In FIG. 1, reference numeral 1 is a printed wiring circuit 2 on the first and second layers on the upper and lower surfaces.
A printed wiring board on which the inner layer 3 is formed (hereinafter referred to as an inner layer printed wiring board), 4 is a print on which a third layer printed wiring circuit 5 formed by being placed on the outer layer above the inner layer printed wiring board 1 is formed Wiring board (hereinafter referred to as first outer layer printed wiring board), 6 is inner layer printed wiring board 1
4 is a printed wiring board on which a printed wiring circuit 7 of a fourth layer which is positioned and laminated on the lower outer layer is formed.

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 pattern, and through holes 12, 13 and 14 are drilled in the central portions of the connection 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, as shown in FIG. 1, the printed wirings of the first and second layers of the inner layer printed wiring board 1 are formed. The outer diameters of the connecting lands 8 and 9 of the circuits 2 and 3 are set to the through holes 13 of the connecting lands 10 and 11 of the first and second outer layer printed wiring boards 4 and 6, respectively.
The diameters 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 are set to be larger than the diameter of 14 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 manufacturing 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 through holes 12 are formed by punching, and similarly, the first and second outer layer printed wiring boards 4 and 6 are the third layer and the fourth layer having the connection lands 10 and 11 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 processed and punched, 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 and 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 layers of the printed wiring boards 1, 4 and 6 while arranging the centers of the laying together.

That is, this method relates to the alignment of the inner and outer layer printed wiring boards 1, 4 and 6 and
After a prepreg (not shown) is interposed between the inner and outer layer printed wiring boards 1, 4 and 6, the layers are laminated in a laminated state by heating and pressing. 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 are 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
A 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 performed 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.
A plurality of conductive wires 1 of the electronic component 23 in 3 and 14
After inserting the lead 25 consisting of 6 and setting it,
The molten solder 17 is applied to the through holes 12, 13 and 14 by utilizing the capillary phenomenon of the thin wires 16 of the lead 25.
By filling the inside and 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. Each of the inner and outer layer printed wiring boards 1, 4 in which the leads 25 formed of the plurality of fine wires 16 of the electronic component 23 are loaded and set in the 12, 13, and 14
As an example thereof, a method of carrying out by dipping Nos. 6 and 6 in a solder bath (not shown) filled with molten solder can be mentioned.

A more specific method of this method will be described below. As described above, the inner and outer layer printed wiring boards 1 and 4
1 and 6 (hereinafter, each printed wiring board after lamination is simply referred to as a multilayer board) through holes 12, 13, and 14, a lead 25 including a plurality of fine wires 16 of an electronic component 23 is inserted as shown in FIG. Is set. The thin wire 16 of the lead 25 is made of a conductive material such as copper. For example, when the diameter of the through hole 12 is 0.8 mm, the thin wire 1 is
The diameter of 6 is about 50 to 100 μmφ, and the leads 25 formed by about 10 to about 30 thin wires 16 are inserted into the through hole 12. In this case, it is preferable that the surface of each of the fine wires 16 is flux-treated. Further, as each thin wire 16, a product name “Winking Wire CP-1515” (manufactured by Taiyo Denki Sangyo Co., Ltd.) can be used. A small gap is formed between the thin wires 16 of the lead 25 inserted in the through hole 12, and the gap forms a capillary state between the thin wires 16.

After the lead 25 including the plurality of thin wires 16 is loaded, the multilayer board is immersed in a solder bath (not shown). The solder bath is filled with molten solder maintained at around 260 ° C., and the through hole 1 is immersed in the solder bath.
Molten solder penetrates into 2, 13 and 14. And
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. This allows the through holes 12, 13 and 14
The inside of is filled with leads 25 composed of a plurality of thin wires 16 and molten solder, and is filled in a state of being raised above both connection lands 10 and 11 as shown in FIG. It should be noted that the multi-layer board is immersed in the solder bath for about 5 seconds because the surface opposite to the set surface of the electronic component 23 is immersed and thermal damage to the printed wiring boards 1, 4 and 6 is prevented. Is good, and the molten solder can be smoothly filled by the capillary phenomenon between the fine wires 16 even in such a short time immersion, so that the molten solder can be filled with the through holes 12, 1.
3 and 14 can be filled.

The through holes 12, 13 and 14 of the multilayer board pulled up from the solder bath are filled with leads 25 consisting of a plurality of fine wires 16 and solder 17, and the solder 17 rises up on the surfaces of the connection lands 10 and 11. In this state, it is in good contact with the connection lands 8 and 9. As a result, the connecting lands 8, 9, 10 and 11 are electrically connected to each other through the leads 25 formed of the solder 17 and the plurality of thin wires 16 made of a conductive material, and reliable conduction is achieved.

In this embodiment, the through hole 1
Inserting leads 25 consisting of a plurality of thin wires 16 into 2, 13 and 14 → connecting lands 8 only by dipping in a solder bath,
It is possible to make 9, 10, and 11 conductive. For this reason, conduction between lands can be performed without performing complicated processing such as plating, printing, and soldering, and a large amount of processing can be performed quickly. Further, since the solder is absorbed in the through hole by the capillary phenomenon, a sufficient amount of solder can be surely filled in the through hole, which enables connection with improved reliability of conduction resistance.

The electronic component 23 is to be mounted on the multilayer printed wiring board 15, and is composed of a package body 24 accommodating ICs, LSIs and other chips, and a plurality of thin wires 16 drawn from the package body 24. A plurality of leads 25, each lead 25 (one lead 25 in the figure) is a through hole 12 of the multilayer printed wiring board 15.
It is loaded and mounted in 13 and 14. Further, the plurality of thin wires 16 forming the leads 25 are arranged with a pitch that causes a capillary phenomenon, and the capillary phenomenon absorbs the solder into the through holes. As a result, the through holes are filled with the solder and the leads 25 are 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 respective printed wiring boards 1, 4 and 6, the mutual positioning 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 connection 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 and the like are performed.

After that, necessary outer shape processing and surface treatment after flux application, and other necessary processing and treatment are further performed to complete the formation processing of the multilayer board. Then, thereafter, 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 are appropriately used. It can be carried out by a method. As a matter of course, the structure and the manufacturing method of the four-layered multilayer printed wiring board 15 are not limited to those in the above-described embodiments, and the same operation and effect can be applied to the manufacture of a multilayered 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 stacking 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 or 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 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 conductivity at the same portion due to the soldering is improved. It can be improved.

[0029]

According to the multilayer printed wiring board of the present invention, it is possible to simplify the production of such a printed wiring board, reduce the cost, and improve the reliability of quality.

[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 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

Claims (1)

[Claims] 1. A through hole in which each layer of a multilayer printed wiring board is formed by each printed wiring board, the printed wiring boards are laminated and adhered, and a required circuit of each printed wiring board is punched in each printed wiring board. In a multilayer printed wiring board configured by electrically connecting via, a printed wiring board forming each of the layers, the outer diameter of the connection land of the printed wiring board located in the inner layer is located in the outer layer The diameter is larger than the through hole diameter of the connection land of the wiring board, and the through hole diameter of the connection land of the printed wiring board located in the outer layer is larger than the through hole diameter of the connection land of the printed wiring board located in the inner layer. A large-diameter connecting land is provided and a plurality of thin wires of electronic parts are inserted in each through hole drilled in each printed wiring board. The lead is inserted into the through hole by capillarity of a plurality of thin wires of the lead, and the solder between the lead and the through hole of the electronic component is used to connect the printed wiring boards. A multilayer printed wiring board characterized by being configured by electrically connecting the circuits of.