JP2003031917A - Structure for embedding conductive paste in blind hole of circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for embedding conductive paste in blind hole of circuit board that can improve the embedded reliability of conductive paste at low cost. SOLUTION: A circuit board 1, constituted by respectively forming conductor layers 3a and 3b on both surfaces of a resin substrate 2, is prepared, and a prescribed circuit pattern and an opening 4 are formed in the conductor layer 3a, formed on the blind hole 10 forming-side surface of the substrate 2 through etching. At the same time, a plurality of very small openings 5, having prescribed opened diameters, is made through the conductor layer 3b at the position corresponding to the opening 4 of the conductor layer 3a. In addition, a blind hole 10, having the same diameter as the opening 4 has, is made through the substrate 2. A screen 20 is placed on the board 1 from the conductor layer 3a side and conductive paste 11 is applied from the upside of the screen 20. Then printing is performed by scratching the applied paste 11, in the direction shown by the arrow in the figure by means of a squeegee 12. Since air escapes through the very small openings 5, formed through the conductor layer 3b as the paste 11 enters the blind hole 10, no bubble is generated, and accordingly, hollow section will not be formed in the hole 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention penetrates from one conductive layer of a circuit board having conductive layers on both sides of a printed circuit board, a circuit board used for an inspection device, a semiconductor device or the like to the other conductive layer. However, the present invention relates to a structure in which a conductive paste is embedded in a bottomed hole formed so that the other conductive layer constitutes the bottom of the hole.

[0002]

2. Description of the Related Art Conventionally, in order to establish conduction between conductive layers of a circuit board having a plurality of conductive layers, a through hole formed so as to penetrate each conductive layer for conduction or one of the conductive layers is formed. Without penetrating the other conductive layer while penetrating the layer,
A method is used in which the inner side surface of the bottomed hole formed so that the other conductive layer forms the bottom of the hole is plated with a conductive material such as copper, or a conductive paste is embedded.

For example, in the method of embedding a conductive paste, the conductive paste is mainly embedded by screen printing. FIG. 2 is a partial cross-sectional view for explaining a conductive paste embedding structure by screen printing. As shown in FIG. 1A, first, for example, from the conductive layer 102a side of the circuit board 100 including the conductive layers 102a and 102b on both surfaces of the interlayer insulating layer 101, the conductive layer 1 is formed.
A bottomed hole 104 is formed so as to penetrate through the conductive layer 102a and the interlayer insulating layer 101 so as to reach 02b. Then, the screen 20 in which the opening 201 having a diameter larger than the opening diameter of the formed bottomed hole 104 is formed.
0 is placed on the circuit board 100 from the side of the conductive layer 102a. The screen 2 thus placed on the circuit board 100.
00, the conductive paste 300 is applied from above, and the applied conductive paste 300 is scratched and printed by a squeegee 301 in the direction of the solid line arrow in the figure, the conductive paste 300 is embedded in the bottomed hole 104, and the conductive layer 102a, The continuity between 102b is established.

[0004]

However, for example, in the case of conducting electricity by a plating method, a large-scale new facility (plating processing line) is required, resulting in high cost. On the other hand, of the methods of embedding a conductive paste, when conducting through a through hole, it is technically difficult to adjust and control the amount of projection of the conductive paste from the upper and lower openings of the through hole, and When using a hole for conduction, see Fig. 2 (b).
As shown in FIG.
There is a problem that it is not possible to embed it in 04, and bubbles are included in the bottomed hole 104 to form a hollow portion (void) 105, which may lead to a decrease in embedding reliability. In particular, when the bottomed hole 104 is deep, this problem becomes remarkable.

Therefore, as shown in FIG. 3, a conductive paste is embedded by vacuum screen printing. FIG. 3 is a partial cross-sectional view for explaining a conductive paste embedding structure by vacuum screen printing. As shown in FIG. 3A, the conductive layer 102a of the circuit board 100.
From the side to reach the conductive layer 102b.
02a and the interlayer insulating layer 101 so as to penetrate the bottomed hole 1
04 formed with an opening 201
00 is placed on the circuit board 100 from the conductive layer 102a side. Then, the conductive paste 300 applied on the screen 200 is scraped in the vacuum chamber 302 capable of making the inside of the chamber into a vacuum state with a squeegee 301 in the direction of the solid line arrow in the figure, and the conductive paste 30 is placed in the bottomed hole 104.
Embedding 0 is performed. As a result, as shown in FIG. 7B, no bubbles are generated in the bottomed hole 104 and the void 105 is not formed. Therefore, in vacuum screen printing, high embedding reliability can be ensured.

However, in vacuum screen printing,
The printing machine is more expensive than a normal printing machine for screen printing, and there is a problem that productivity is not so good because some time is required to prepare the vacuum chamber 302 to be in a vacuum state. .

The present invention has been made to solve the above problems, and provides a conductive paste burying structure in a bottomed hole of a circuit board which is inexpensive and can improve burying reliability. The purpose is to

[0008]

A structure for embedding a conductive paste in a bottomed hole of a circuit board according to the present invention is provided with first and second conductive layers on both sides, and the first and second conductive layers are provided. The second conductive layer, which penetrates the first conductive layer and the interlayer insulating layer from the first conductive layer side to the second conductive layer side of a circuit board including an interlayer insulating layer for insulating conductive layers. Is a structure for embedding a conductive paste in a bottomed hole formed so as to form the bottom of the hole to establish conduction between the first and second conductive layers, the bottomed hole At least one opening having a predetermined opening diameter is formed in the second conductive layer located at the bottom of the first conductive layer, and the conductive paste is embedded in the bottomed hole by screen printing from the first conductive layer side. It is characterized by having done.

According to the present invention, the opening is formed at the bottom of the bottomed hole formed in the circuit board, and the conductive paste is embedded in the bottomed hole by the usual screen printing. Since air bubbles do not enter to form a hollow portion and it is not necessary to perform vacuum screen printing, it is possible to realize an inexpensive conductive paste embedding structure with high reliability. As a result, it is possible to manufacture a circuit board having conductive layers on both surfaces, which is low in cost and high in productivity.

The opening is 10 μm to 100 μm.
It has an opening diameter of m and is preferably formed by an etching method or a laser irradiation method.
The reason why the opening diameter is 10 μm to 100 μm is that the optimum opening diameter varies depending on the viscosity of the conductive paste.
The reason why the etching method or the laser irradiation method is adopted is that the opening can be formed easily and inexpensively. In addition,
As an etching method, a plasma etching method or the like can be considered.

The first and second conductive layers are preferably made of copper, but other conductive materials may be used.

Similarly, the interlayer insulating layer is preferably made of polyimide resin, but other insulating resin may be used.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a process view showing a part in section for explaining a conductive paste embedding structure according to an embodiment of the present invention.

First, as shown in FIG. 1A, conductor layers 3a made of a conductive material such as copper foil are formed on both surfaces of a resin substrate 2 as an interlayer insulating layer made of an insulating resin such as polyimide.
A circuit board 1 formed with 3b is prepared.

After the circuit board 1 is prepared, as shown in FIG. 2B, a predetermined circuit pattern or a bottomed pattern is formed on the conductor layer 3a on the side where the bottomed hole 10 (see FIG. 1C) is to be formed. The opening 4 having the opening diameter of the hole 10 is formed by an etching method or the like, and the opening diameter of the bottomed hole 10 is formed in the conductor layer 3b at a position corresponding to the opening 4 on the side which becomes the bottom of the bottomed hole 10. A predetermined opening diameter, for example, 10 μm to 100 μ
A plurality of m minute openings 5 are also formed by a method such as an etching method.

After the opening 4 and the minute opening 5 of the bottomed hole 10 are formed in this way, as shown in FIG. 3C, for example, laser light of a predetermined intensity is emitted from the irradiation tip of a laser irradiation device (not shown). Irradiation is performed in accordance with the opening 4, and a bottomed hole 10 having a hole diameter similar to the opening diameter of the opening 4 is formed in the resin substrate 2. In this case, the bottomed hole 10 and the minute opening 5 formed in the conductor layer 3b communicate with each other. The opening 4
It is preferable that the opening diameter of and the hole diameter of the bottomed hole 10 be about 0.3 mm. The reason is that if the hole diameter is larger than this, the degree of freedom in circuit design is lowered, so it is preferable that the hole diameter is as small as possible, but if the hole diameter is smaller than this, the embedding property becomes extremely poor.

After forming the bottomed hole 10, an opening 21 having a diameter larger than the opening diameter of the opening 4 (hole diameter of the bottomed hole 10) was formed as shown in FIG. The screen 20 is placed on the circuit board 1 from the side of the conductive layer 3a, and the conductive paste 11 is applied from above the screen 20.
Then, apply the conductive paste 11 to the squeegee 12
Print by scraping in the direction of the solid line arrow in the figure.

By printing the conductive paste 11 on the screen 20 with a squeegee 12 to print, the conductive paste 11 is filled so as to fill the openings 21 and the bottomed holes 10 as shown in FIG. It will be embedded in the bottom hole 10. Then, as the conductive paste 11 enters the bottomed hole 10, air escapes from the minute openings 5 formed in the conductor layer 3b, so that no bubbles are generated in the bottomed hole 10. The possibility that a hollow portion will be formed is reduced.

When the conductive paste 11 is completely embedded in the bottomed hole 10 in this manner, all the air in the bottomed hole 10 becomes a small opening 5 as shown in FIG. It escapes from the inside, and the inside of the bottomed hole 10 is filled with the conductive paste 11. Since the conductive paste 11 has a predetermined viscosity, it is considered that it is unlikely that the conductive paste 11 leaks to the outside from the minute openings 5 of the conductive paste 11 reaching the bottom of the bottomed hole 10 due to surface tension.

As described above, according to this embedding structure, since the minute opening 5 is provided in the bottom of the bottomed hole 10 to serve as an air escape hole, expensive vacuum screen printing is not required. Also, it is possible to embed the conductive paste 11 that does not contain bubbles and has high reliability in the bottomed hole 10.

The minute openings 5 may be formed by laser irradiation. In this case, the direction of laser irradiation may be from the conductor layer 3b side before the bottomed hole 10 is formed and from the bottomed hole 10 side after the bottomed hole 10 is formed.

[0022]

As described above, according to the present invention,
After the opening is formed at the bottom of the bottomed hole formed on the circuit board, the conductive paste is embedded in the bottomed hole by normal screen printing.Therefore, bubbles enter the bottomed hole to form a hollow part. Since there is no need to perform vacuum screen printing, it is possible to realize a highly reliable conductive paste embedding structure at a low cost. As a result, there is an effect that it is possible to manufacture a circuit board having conductive layers on both surfaces, which has low cost and high productivity.

[Brief description of drawings]

FIG. 1 is a process drawing showing a part in cross section for explaining an embedded structure of a conductive paste according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view for explaining a conductive paste embedding structure by screen printing.

FIG. 3 is a partial cross-sectional view for explaining an embedded structure of a conductive paste by vacuum screen printing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Circuit board, 2 ... Resin board, 3 ... Conductive layer, 4 ... Opening part, 5 ... Small opening part, 10 ... Bottom hole, 11 ... Conductive paste, 12 ... Squeegee.

Claims (5)

[Claims] 1. A circuit board comprising first and second conductive layers on both sides thereof, and an interlayer insulating layer for insulating the first and second conductive layers from the first conductive layer side to the second conductive layer side. To the conductive layer side of the first and second bottomed holes formed so that the second conductive layer forms the bottom of the hole while penetrating the first conductive layer and the interlayer insulating layer. A conductive paste embedding structure for electrical connection between the conductive layers, wherein at least one opening having a predetermined opening diameter is formed in the second conductive layer located at the bottom of the bottomed hole. A conductive paste embedding structure in a bottomed hole of a circuit board, wherein the conductive paste is embedded in the bottomed hole by screen printing from the first conductive layer side. 2. The embedded structure according to claim 1, wherein the opening has an opening diameter of 10 μm to 100 μm. 3. The embedded structure according to claim 1, wherein the opening is formed by an etching method or a laser irradiation method. 4. The embedded structure according to claim 1, wherein the first and second conductive layers are made of copper. 5. The embedded structure according to claim 1, wherein the interlayer insulating layer is made of a polyimide resin.