JPH11126951A - Printed circuit board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To electrically or mechanically reinforce a conductor pattern formed on a printed wiring board without increasing the plane occupying areas of the pattern by forming conductive reinforcing layers of solder layers or electroless plated layers on the upper surfaces of the narrow parts of the pattern. SOLUTION: A conductor pattern 2 is formed on an insulating substrate 6 clad with copper foil. After a solder resist 5 is applied to pads 3 and the parts of the pattern 2 to be reinforced so that openings 5a may be positioned, cream solder is applied from the openings 5a. Electronic parts are mounted on the pads 3 by applying the cream solder to the pads 3 also and, during the course of the formation of a printed circuit board, the formation of conductive reinforcing layers 4 and the mounting of the electronic parts are performed simultaneously. The circuit board is heated and the reinforcing layers 4 are formed on the surfaces of the parts to be reinforced of the pattern 2. Therefore, the pattern 2 can be reinforced not only electrically against the increase of electric capacity, but also mechanically against shocks, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board having a large component mounting density and an extremely narrow width of a conductor pattern, particularly without increasing the plane occupied area of the conductor pattern. The present invention relates to a device capable of reinforcing mechanical and mechanical strength.

[0002]

2. Description of the Related Art Conventionally, printed circuit boards for mounting electronic components on various electronic devices have been used. Printed circuit boards include single-sided boards (conductor patterns formed only on one side of the insulating board), double-sided boards (conductor patterns formed on both sides of the insulating board), and multilayer boards (only on both sides of the insulating board) However, there is also a conductor pattern formed on the inner layer part), but with the recent miniaturization and high-density mounting of electronic devices, higher density of printed circuit boards is required. Double-sided boards and multilayer boards are often used.

[0003]

However, as the density of printed circuit boards is increased, the component mounting density is increased. As a result, the portion of the conductor pattern having a narrow width is also increased. However, the narrow portion of the conductor pattern has a drawback that the current path is small, so that it is weak against an increase in current capacity, and because the width is narrow, it is weak against impact and the like. It is desirable to reinforce it in terms of quality.

The present invention has been proposed to solve the above-mentioned problem, and a printed circuit board which can be reinforced electrically or mechanically without increasing the plane occupied area of a conductor pattern, and a printed circuit board having the same. And a method of manufacturing such a printed circuit board.

[0005]

According to a first aspect of the present invention, there is provided a printed circuit board, comprising: a conductive pattern formed on the printed circuit board; It is characterized in that it has a structure in which a conductive reinforcing layer is formed by a solder layer or an electroless plating layer.

According to a second aspect of the present invention, a solder resist is formed on an upper surface of a printed circuit board having a conductive pattern formed by a subtractive method, and a cream is formed on a part of the conductive pattern. When solder is applied and electronic components are mounted, a solder resist is formed so that an opening is located in the narrow part of the conductor pattern to be reinforced, cream solder is placed in the opening, and then heated. It is characterized in that a conductive reinforcing layer is formed.

According to a third aspect of the present invention, there is provided a printed circuit board having a conductor pattern formed by an additive method, wherein a solder resist having only a portion of the conductor pattern to be reinforced is opened. After forming
The conductive reinforcement layer is formed by applying electroless plating to the opening. The present invention can be applied to both surface mounting boards and insertion mounting boards.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example of a printed circuit board formed by a subtractive method. In the printed circuit board 1, 2 is a conductor pattern, 3 is a pad for mounting an electronic component (a portion for mounting an electronic component for surface mounting), and 4 is a conductive reinforcement formed by applying cream solder. Layer 5, opening 5a
Is a solder resist, and 6 is an insulating substrate.

FIG. 2 shows a vertical cross-sectional structure of a main part of the printed circuit board 1 prepared by the subtractive method. Reference numeral 5 denotes a solder resist, and 6 denotes an insulating substrate.
In the figure, the same components as those of the printed circuit board shown in FIG. FIG.
1 is a flowchart showing a procedure for forming a conductive reinforcing layer when a printed circuit board is prepared by a subtractive method.

First, a conductor pattern 2 is formed on an insulating substrate 6 to which a copper foil is attached. That is, an etching resist is applied on the surface of the copper foil of the insulating substrate (step 10).
0), the remaining copper foil not subjected to the etching resist is chemically corroded (etched) using a chemical (step 101). Then, since the copper foil is not corroded (etched) in the portion where the etching resist has been applied, the conductor pattern is exposed on the substrate surface when the resist is removed,
It is formed (step 102).

Subsequently, a solder resist 5 is applied so that the opening 5a is located at the portion of the pad 3 and the conductor pattern 2 to be reinforced (step 103), and a cream solder is applied from the opening 5a (step 104). At this time, cream solder is also applied to the pads 3 and electronic components (not shown) are mounted thereon (step 105). At the stage of forming the printed circuit board, the formation of the conductive reinforcing layer 4 and the electronic components are performed. Since mounting (not shown) can be performed at the same time, loss of time is reduced, and it is economical.

When the cream solder is applied, in a place where the pads 3 are dense or where a part where the conductor pattern 2 is to be reinforced is close to the pad 3,
In some cases, the cream solder is applied between the pads or between the portion of the conductor pattern 2 to be reinforced and the pad 3. In such a case, the opening corresponding to the portion to which the cream solder is to be applied is provided. It is preferable to use a metal mask on which is formed.

Finally, when the circuit board is heated, the conductive reinforcing layer 4 is formed on the surface of the portion of the conductor pattern 2 to be reinforced (step 106). FIG. 4 shows another example of the present invention applied to the printed circuit board 1 formed by the additive method. FIG. 5 is a view showing a longitudinal sectional structure of a main part thereof, and 7 is a plating resist.

In the figure, the same components as those of the printed circuit board shown in FIG. 1 are denoted by the same reference numerals as in the previous example, and description thereof is omitted. In this example, the conductor pattern 2 formed on the upper surface of the insulating substrate 6 has a land 8 having a through hole 8a formed at the tip thereof, and the entire conductor pattern 2 is entirely formed by the solder resist 5. And the conductive reinforcing layer 4 formed by the electroless plating layer is exposed from the opening 5 a of the solder resist 5.

When the conductive reinforcing layer 4 is formed on the printed circuit board 1 formed by such an additive method, as shown in FIG. 5, the conductive reinforcing layer formed by the electroless plating layer is used. 4 is a solder resist 5
Since they are formed flush with each other and do not protrude, the appearance is good and the reinforcing effect is high. Further, according to this method, the conductor pattern 2 formed by the electroless plating layer
Since the same electroless plating is performed on the upper surface of the conductive layer to form the conductive reinforcing layer 4, the current density becomes uniform and the physical bonding strength can be further increased.

FIG. 6 is a flowchart showing a procedure for forming a conductive reinforcing layer when a printed circuit board is formed by the additive method. First, a conductor pattern is formed on an insulating substrate. That is, a plating resist is applied on the surface of an insulating substrate on which a conductor pattern is to be formed (step 200), and electroless plating is applied from above (step 201).

Then, the portion not subjected to the plating resist is plated to form a conductor pattern. Since the remaining plating resist is an electrically insulating film, it does not need to be peeled off and is left. Subsequently, solder resist printing is performed so that an opening is located at a portion of the pad and the conductor pattern to be reinforced (step 202).

After that, if electroless plating is applied to the opening, an electroless plating layer is formed in the opening, and a conductive reinforcing layer can be formed (step 203).

[0019]

As can be understood from the above description, according to the printed circuit board of the first aspect, the conductive pattern is strengthened by the solder layer or the electroless plating layer on the upper surface of the narrow portion of the conductive pattern. Since the layer is formed, the current path can be enlarged without increasing the plane occupied area of the conductor pattern, and it can be electrically reinforced against an increase in current capacity. Can be reinforced.

According to the method of manufacturing a printed circuit board of the present invention, when mounting an electronic component, a solder resist is formed so that an opening is located in a narrow portion to be reinforced, and then the solder resist is formed. By applying cream solder to the opening and heating, the formation of the conductive reinforcing layer and the mounting of the electronic component can be performed at the same time, so that the manufacturing process can be simplified and the cost can be reduced.

According to the method of manufacturing a printed circuit board according to the third aspect, since the conductive reinforcing layer is formed by electroless plating as in the case of the conductor pattern, the current density becomes uniform and the joining strength is improved. Since it is strong, the mechanical strength can be further increased.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a printed circuit board formed by a subtractive method.

FIG. 2 is a diagram illustrating a vertical cross-sectional structure of a main part of a printed circuit board created by a subtractive method.

FIG. 3 is a flowchart showing a procedure for forming a conductive reinforcing layer when a printed circuit board is produced by a subtractive method.

FIG. 4 is a perspective view showing an example of a printed circuit board formed by an additive method.

FIG. 5 is a diagram showing a vertical cross-sectional structure of a main part of a printed circuit board prepared by an additive method.

FIG. 6 is a flowchart showing a procedure for forming a conductive reinforcing layer when a printed circuit board is produced by an additive method.

[Explanation of symbols]

 Reference Signs List 1 printed circuit board 2 conductive pattern 4 conductive reinforcing layer 5 solder resist

Claims (3)

[Claims] 1. A printed circuit board having a structure in which a conductive reinforcing layer of a solder layer or an electroless plating layer is formed on an upper surface of a narrow portion of a conductor pattern formed on the printed circuit board. 2. A method according to claim 1, wherein a solder resist is formed on an upper surface of a printed circuit board having a conductor pattern formed by a subtractive method, and a cream solder is applied to a part of the conductor pattern to mount an electronic component. A printed circuit board, wherein a solder resist is formed so that an opening is located in a narrow portion of a pattern to be reinforced, a cream solder is applied to the opening, and then heating is performed to form a conductive reinforcing layer. Manufacturing method. 3. A printed circuit board having a conductor pattern formed by an additive method, wherein a solder resist having an opening only in a portion of the conductor pattern to be reinforced is formed, and then the opening is subjected to electroless plating. And a method of manufacturing a printed circuit board, comprising forming a conductive reinforcing layer.