JPH07176847A - Circuit board and its manufacture - Google Patents

Abstract

PURPOSE:To improve the electrical connectability between a hardened conductive body and wiring pattern by grinding the end face of the hardened conductive body formed to cover at least part of a land section to a flat face. CONSTITUTION:A wiring pattern 2 is formed on at least one surface of an insulating substrate and has a land section 5. In order to increase the contacting area of the land section 5 with a hardened conductive body 4, the width W of the section 5 is made wider under the restriction of other wiring patterns. A pierced hole 3 for through hole 3 is filled with the body 4, with the end of the body 4 being protruded from the section 5 so that the body 4 can cover at least part of the section 5, and the end face A of the body 4 is flattened. When such a constitution is used, the land section 5 can be widely covered with the body 4 without increasing the height of the body 4. Therefore, the reliability of the electrical connection between the body 4 and pattern 2 can be remarkably improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board having a novel structure and a method for manufacturing the same.

[0002]

2. Description of the Related Art Electrical connection between circuit patterns existing on both sides of a circuit board having wiring patterns formed on both sides of an insulating substrate is performed by forming through holes for through holes in the insulating substrate and conducting through the through holes for through holes. It is done by the presence of sexual substances.

Conventionally, the connection between the wiring patterns of the circuit board is performed by filling the through holes for through holes with a curable conductive material.
A method of performing curing is known.

In such a method, the reliability of the electrical connection between the hardened body of the curable conductive material (hereinafter also simply referred to as the conductive hardened body) formed by filling the through holes for through holes and the wiring pattern is improved. A circuit board is proposed in which a land portion is formed around a through hole for a through hole as a wiring pattern, and the hardened body of the curable conductive material covers a part of the land portion. There is.

[0005]

However, in order to maintain the reliability of electrical connection at a high level, the above-mentioned circuit board has the following problems.
Although it is necessary to increase the area of the conductive cured body that covers the land portion, the protrusion height of the conductive cured body becomes a problem accordingly.

That is, in order to protect the wiring pattern on the wiring pattern formed on the circuit board or to form a second circuit pattern on the wiring pattern,
An insulating layer such as a solder resist is generally formed.

The protrusions of the conductive cured body cause non-uniformity of the layers in the formation of the insulating layer, which lowers the insulation reliability due to the layer and causes variations in noise generated between circuits. However, there is a problem in that it is difficult to take measures against noise.

Further, even when the insulating layer is not formed, a problem arises in that it is very difficult to control the amount of solder when printing a solder cream for mounting components.

[0009]

[Means for Solving the Problems] The inventors of the present invention have made extensive studies to solve the above technical problems. As a result, it is possible to obtain a circuit board that solves all the above problems by a simple means of grinding an end surface of a conductive cured body formed so as to cover at least a part of a land portion to form a flat surface. They found out and came to propose the present invention.

FIG. 1 is a sectional view showing a typical embodiment of the circuit board of the present invention.

That is, according to the present invention, the wiring pattern 2 including the land portion 5 is provided on at least one surface of the insulating substrate 1, and the through hole through hole 3 penetrating the insulating substrate 1 is provided in the land portion 5. The through hole 3 for the through hole
In addition, the hardened body 4 of the hardenable conductive material is filled so as to project from the land portion 5 so as to cover at least a part of the land portion 5, and the end surface A of the hardened body 4 is formed as a flat surface. It is a circuit board characterized by.

In the present invention, the insulating substrate 1 is not particularly limited, and one having a known material and structure is used. Typical examples are paper base material-phenolic resin laminated board, paper base material-epoxy resin laminated board, paper base material-polyester resin laminated board, glass base material-epoxy resin laminated board, paper base material-Teflon. Resin laminated substrate, glass substrate-polyimide resin laminated substrate, glass substrate-BT (bismaleimide-triazine) resin resin laminated substrate, composite resin substrate or other synthetic resin substrate, polyimide resin, polyester resin or other flexible substrate, Aluminum, iron,
Examples thereof include a metal-based insulating substrate obtained by insulating a metal such as stainless steel with an epoxy resin or the like, a ceramics substrate, and the like.

In the present invention, the wiring pattern 2 is formed on at least one surface of the insulating substrate and the land portion 5 is formed.
Have. The wiring pattern can be usually obtained by etching a conductive layer such as a copper foil or an aluminum foil attached to an insulating substrate into a predetermined pattern by a known method.

Further, the width W of the land portion 5 is preferably as large as possible under the constraint of other wiring patterns in order to increase the contact area with the conductive cured body 4 described later, but in general, It is preferable to determine in the range of 100 μm or more and 3 times or less of the diameter of the through hole 3 for through hole.

In the present invention, the through hole 3 for through hole is used.
Is a land portion 5 in the wiring pattern 2 of the circuit board.
Formed within. The through-holes 3 for through-holes can be provided by drilling by a usual method such as drilling or punching. The diameter of the through hole for through hole is not particularly limited. In general,
The hole diameter (diameter) may be such that it can be filled with the curable conductive material, and it can be selected from usually 0.2 mm or more, preferably 0.3 to 2 mm. Also,
A circular shape is preferable because it is easy to process.

The greatest feature of the present invention is that the through hole 3 for through hole is filled with the conductive hardened material 4 so as to project from the land portion 5 so as to cover at least a part of the land portion 5, and The end surface A of the cured body 4 is to be a flat surface.

The flat surface does not mean a surface that is strictly parallel to the substrate surface, but has a certain degree of inclination, generally 30.
It may have an inclination of not more than 10 degrees, preferably not more than 10 degrees.

By adopting such a constitution, it is possible to widely cover the land portion without increasing the height of the conductive hardened body, whereby the electrically conductive hardened body and the wiring pattern are electrically connected. The reliability of can be significantly improved. In addition, when the end surface of the conductive cured body is configured to be a surface parallel to the substrate surface, when an insulating layer is formed on the end surface, a change in the thickness of the insulating layer at that portion is effective. The thickness of the insulating layer can be easily controlled, and the occurrence of insulation failure can be significantly reduced.

It is preferable that the area of the conductive cured body covering the land portion is designed to cover 10% or more of the land portion.

Further, it is preferable that the height h from the highest part of the conductive cured material to the surface of the land is designed to be usually 10 to 100 μm, preferably 10 to 50 μm. That is, when the height of the protrusion exceeds 100 μm,
For example, when the solder resist layer is formed, the thickness of the layer is significantly uneven, and it becomes difficult to control the amount of solder during solder cream printing. On the other hand, when the height of the protruding portion h is less than 10 μm, it becomes difficult to make the conductive cured body uniformly exist on the land portion, the reliability of the electrical connection with the wiring pattern decreases, and the yield of the product decreases. May cause a decrease.

The method of manufacturing the circuit board of the present invention is not particularly limited, but a typical manufacturing method is exemplified. At least one surface of the insulating substrate has a wiring pattern including a land portion, and the land portion has the above-mentioned wiring pattern. A substrate provided with through holes for through holes penetrating the insulator is prepared, and a curable conductive material is provided in the through holes for through holes of the substrate so as to cover at least a part of the land portion and project from the land portion. Filling
After curing, a method of grinding the cured body of the curable conductive material protruding from the land portion into a flat surface parallel to the substrate surface so that a part thereof remains on the land portion is preferable.

FIG. 2 is a process chart showing a typical mode for carrying out the above method.

Referring to FIG. 2, a wiring pattern including a land portion is provided on at least one surface of the insulating substrate,
As a method of manufacturing a substrate in which a through hole for penetrating the insulating substrate is provided in the land portion, the following method may be mentioned.

(A) An insulating substrate 1 having conductive layers 6 formed on both sides is prepared, and (b) a through hole through hole 3 is formed in the insulating substrate 1.

Examples of the conductive layer 6 include metal foils such as copper foil and aluminum foil, and metal plating layers such as copper.
Further, the thickness of the conductive layer is appropriately about 2 to 200 μm.

(C) Next, the conductive layer 6 is etched by a known method to form the wiring pattern 2 having the land portion 5 around the through hole through hole 3.

(D) The through hole 3 for through hole is filled with a curable conductive material so as to protrude from the land portion so as to partially cover the land portion, and then cured. The filling amount is preferably adjusted so that the obtained conductive cured body covers the land portion with the above-described area.

In the present invention, the curable conductive substance constituting the conductive cured product is a mixture of a conductive metal component and a resin component, which has fluidity in filling and is cured by heat or light. Well-known materials may be used without particular limitation as long as the cured product exhibits conductivity. Specific examples thereof include silver paste and copper paste. As a specific composition, a mixture of a conductive material such as gold, silver, copper, nickel, lead or carbon and a crosslinkable thermosetting resin such as an epoxy resin or a phenol resin, if necessary, together with an organic solvent is used. It

The viscosity of the curable conductive material before curing is
Generally, 20 to 20000 poise is suitable.

Although it is possible to use a curable conductive substance having a low viscosity in order to increase the area covering the land portion, the curable conductive substance filled in the through holes for through holes flows out before curing. However, it is difficult to obtain good conductivity.

Further, the method of filling the through hole through hole with the curable conductive material is not particularly limited, but generally, a method such as a screen printing method or a pin insertion method is preferably adopted.

(E) The substrate filled with the conductive cured body 4 forms a plane A parallel to the substrate surface so that a part of the conductive cured body protruding from the land portion remains on the land portion. So that it is ground.

As a method of grinding a part of the above-mentioned electroconductive cured body, a known method is adopted without particular limitation, and specifically, means such as belt grinding and buff grinding are suitable.

[0034]

As can be understood from the above description, the circuit board of the present invention has extremely high reliability between the wiring patterns electrically connected by filling the through holes for through holes with the conductive hardened material. It is high and has a high yield for the conduction on both sides of the circuit board.

Further, when solder resist printing or solder paste printing is performed in the subsequent process, highly accurate printing is possible, and a circuit board can be manufactured extremely advantageously.

[0036]

EXAMPLES In order to describe the present invention more specifically, examples will be given below, but the present invention is not limited to these examples.

Example 1 A circuit board was manufactured according to the following steps. That is, (a) using a laminated laminate made of a paper base phenol resin base insulating layer 1 having a thickness of 1.6 mm and having a conductive layer 6 made of a copper foil having a thickness of 18 μm on both sides, (b) Through holes for through holes having a diameter of 0.8 mm were made by drilling. Then, the surfaces of the conductive layer 6 and the through holes for through holes are buffed, ultrasonically cleaned,
The washing was performed in the order of high pressure washing.

(C) Next, a dry film ("Aquamer CF" 1.5 mil manufactured by Hercules Co., Ltd.) was laminated as an etching resist on the surface of the copper electrode layer, and exposed and developed to form a resist pattern. Then, etching was performed with a cupric chloride etching solution, and the etching resist was peeled off to form a wiring pattern 2 having a land portion 5 with a width of 600 μm around the through hole 3 for through hole.

(D) A commercially available thermosetting silver paste having a viscosity of 200 poise (PS-652 manufactured by Tokuri Kaken Co., Ltd.) is filled in the through hole 3 for through hole as a curable conductive material by a screen printing method. did. At this time, the silver paste was formed so as to cover 50% of the area of the land portion and project from the surface of the land portion at a height of about 300 μm.

The silver paste was dried and cured in a hot air drying oven under the conditions of 80 ° C. for 4 hours and 150 hours for 2 hours.

(E) Next, using a buff of No. 600 a plurality of times, the cured silver paste is formed so as to project from the land portion on the substrate surface, and the height h from the land portion surface is 40 μm. The surface A parallel to the substrate surface was formed by grinding so as to leave the surface A.

On the surface of the circuit board obtained as described above, "thermosetting solder resist SR-31-SE" manufactured by Tamura Manufacturing Co., Ltd. was formed as a solder resist by a screen printing method, and was cured at 120 ° C. for 10 minutes. .

The formed solder resist had a small thickness variation of 40 μm at the maximum, and had a good appearance.

The resistance value of the formed through hole is obtained by measuring the resistance between the wiring patterns connected on both sides of the through hole. The measurement of 64 holes is performed, and the average value is 9.7 mΩ, standard deviation. Was 2.30 mΩ.

Furthermore, the average rate of change of the through-hole resistance value after performing a repeated impact test at 20 ° C. for 15 seconds and 260 ° C. for 5 seconds 100 times was 5%, and there was almost no change.

Comparative Example 1 A circuit board was obtained in the same manner as in Example 1 except that (e) was not ground. As a result, the state of the formed solder resist has a large variation in thickness and the maximum is 320 μm.
As a result of forming the solder resist layer in the same manner as above, a portion where no resist was formed was found in the vicinity of adjacent through holes.

Comparative Example 2 A circuit board was obtained in the same manner as in Example 1, except that all of the hardened silver paste particles protruding from the land surface of the substrate were ground without leaving them during the grinding of (e). It was As a result, the resistance value of the formed through holes was measured at 64 holes and the average was 17.2 mΩ, and the standard deviation was 4.81 m.
It was Ω.

The average change rate of the through-hole resistance value after 80 times of the repeated impact test at 20 ° C. for 15 seconds and 260 ° C. for 5 seconds was 80%, which was a large change.

[Brief description of drawings]

FIG. 1 is a sectional view showing a typical embodiment of a circuit board of the present invention.

FIG. 2 is a process drawing showing a typical aspect of the method for manufacturing a circuit board of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Wiring pattern 3 Through hole for through hole 4 Cured body of curable conductive material 5 Land portion 6 Conductive layer

Claims (2)

[Claims] 1. A through-hole through hole having a wiring pattern including a land portion on at least one surface of an insulating substrate, the through-hole penetrating the insulating substrate being provided in the land portion. In the circuit, a cured body of a curable conductive material is filled so as to project from the land portion so as to cover at least a part of the land portion, and the end surface of the cured body is formed as a flat surface. substrate. 2. A substrate having a wiring pattern including a land portion on at least one surface of an insulating substrate and having through holes for through holes penetrating the insulator in the land portion is prepared. After the curable conductive material is filled in the through hole for through holes so as to cover at least a part of the land portion and protrude from the land portion and cured, and then the cured body of the curable conductive material protruding from the land portion is formed. A method of manufacturing a circuit board, which comprises grinding a surface so that a part of the land remains on the land.