JP2000022029A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wring board where blisters or delamination hardly occurs between a wiring conductor whose main component is copper and a copper plating layer even if heat is applied to them by a method wherein the copper plating layer is deposited on the surface of the wiring conductor without forming gaps between them. SOLUTION: A wiring conductor 2 whose main component is copper is formed on the surface of an insulating base 1 for the formation of a wiring board, wherein a copper plating layer 3 of thickness 2 to 10 μm is formed on the surface of the wiring conductor 2, and the copper plating layer 3 is composed of a sub-layer 3b and a sub-layer 3a which is kept in contact with the wiring conductor 2, as thick as 0.1 μm or above, and as large in crystal grain diameter as 0.1 to 0.3 μm. The sub-layer 3a is made to penetrate well into fine recesses formed on the surface of the wiring conductor 2, whereby the copper plating layer 3 can be brought into close contact with the wiring conductor 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of depositing a wiring conductor containing copper as a main component on the surface of an insulating substrate and a copper plating layer having a thickness of 2 to 10 .mu.m on the surface of the wiring conductor containing copper as a main component. And to a wiring board formed by applying the method.

[0002]

2. Description of the Related Art Conventionally, as a wiring board for mounting electronic parts such as semiconductor elements, for example, a wiring conductor made of a metallized layer containing tungsten as a main component is coated on the surface of an insulating base made of an aluminum oxide sintered body. Wiring boards to be attached have been frequently used.

In such a wiring board, one end of a wiring conductor attached to the surface of an insulating base and an electrode of an electronic component are electrically connected, for example, via solder, and the other end of the wiring conductor is connected to an external electrical terminal. The electrodes of the electronic component are electrically connected to an external electric circuit by connecting the wiring conductors of the circuit board to each other via solder.

However, according to the wiring board in which the wiring conductor made of tungsten metallization is adhered to the surface of the insulating base made of the aluminum oxide sintered body, the electrical resistivity of the tungsten metallization forming the wiring conductor is about 20 μΩ.・ Because of the high cm, there is a problem that a signal cannot efficiently flow through the wiring conductor or a large current cannot flow through the wiring conductor.

In order to solve this problem, there has been proposed a wiring board in which a wiring conductor containing copper as a main component is adhered to the surface of an insulating base made of glass ceramic.

According to the wiring board in which the wiring conductor mainly composed of copper is adhered to the surface of the insulating base made of glass ceramic, the electrical resistivity of the metal mainly composed of copper forming the wiring conductor is low. Since it is as low as about 6 μΩ · cm, a signal can efficiently flow through the wiring conductor and a large current can flow through the wiring conductor.

[0007]

However, according to the wiring board in which the wiring conductor mainly composed of copper is adhered to the surface of the insulating base made of glass ceramic, the wiring conductor mainly composed of copper is removed. In order to firmly adhere to the surface of an insulating substrate made of glass ceramics formed by copper metallization, it is necessary to contain 4 to 8% by weight of a glass component in the copper metallization. When the glass component is contained, a part of the glass component moves to the insulating base side during the copper metallization when firing the copper metallization, and the diameter of the wiring conductor having copper as a main component is 1 to Many small depressions of about 2 μm are formed.

If there are many such fine pits on the surface of the wiring conductor mainly composed of copper, the wiring conductor and the electrode of the electronic component or the wiring conductor and the wiring conductor of the external electric circuit board are soldered. When connecting via a wire, the wettability between the wiring conductor and the solder is reduced, and the electric connection between the wiring conductor mainly composed of copper and the electrode of the electronic component or the wiring conductor of the external electric circuit board should be made firmly. Can not be done.

Therefore, a copper plating layer having a thickness of about 2 to 10 μm and having a smooth surface is applied to a wiring conductor made of copper metallization, and electrodes of electronic parts and wiring conductors of an external electric circuit board are soldered to the copper plating layer. It is contemplated to connect through.

However, the copper plating layer generally has a crystal grain size of about 0.5 to 1.0 μm. Therefore, when a copper plating layer is applied to a wiring conductor containing copper as a main component, the copper plating layer becomes The diameter formed on the surface is 1-2 μm
As a result, many small voids are formed between the copper-based wiring conductor and the copper plating layer as a result of being stuck over the dent without being able to enter the tiny dent well. There was a problem that would.

When such minute gaps are present between the wiring conductor mainly composed of copper and the copper plating layer, for example, the electrodes of the electronic components and the external electric circuit board are soldered to the wiring conductor of the wiring board. When heat is applied to the wiring board, for example, when the connection is made via a wire, the plating solution and the like sealed in the voids are vaporized and expanded by the heat, and the heat is applied between the wiring conductor containing copper as a main component and the copper plating layer. This causes a problem that swelling and peeling occur.

The present invention has been devised in view of the above problems, and has as its object to form a copper plating layer on the surface of a wiring conductor containing copper as a main component without forming a gap between the two. An object of the present invention is to provide a wiring board which does not cause swelling or peeling between a wiring conductor containing copper as a main component and a copper plating layer even when heat is applied thereto.

[0013]

A wiring board according to the present invention is obtained by coating a wiring conductor mainly composed of copper on the surface of an insulating base, and a copper plating layer having a thickness of 2 to 10 μm on the surface of the wiring conductor. In the wiring board, the copper plating layer is at least 0.1 mm from the surface in contact with the wiring conductor.
The crystal grain size in the thickness region of μm or more is 0.1 to 0.3 μm
It is characterized by having.

According to the wiring board of the present invention, the copper plating layer having a thickness of 2 to 10 μm, which is applied to the surface of the wiring conductor containing copper as a main component, is at least 0.1 mm from the surface in contact with the wiring conductor.
The crystal grain size in the thickness region of 1 μm or more is 0.1 to 0.3 μm
Therefore, the copper plating layer region having a crystal grain size of 0.1 to 0.3 μm is well penetrated into a minute recess having a diameter of about 1 to 2 μm formed on the surface of the wiring conductor mainly composed of copper. Thus, the copper plating layer can be brought into close contact with the wiring conductor containing copper as a main component without gaps.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a wiring board according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view illustrating an example of an embodiment of a wiring board according to the present invention.
2 is a wiring conductor containing copper as a main component, and 3 is a copper plating layer.

The insulating substrate 1 is made of an electrically insulating material such as glass ceramics, a sintered body of aluminum oxide, a sintered body of aluminum nitride, a sintered body of silicon carbide, a sintered body of silicon nitride, and a sintered body of mullite. It has a mounting portion on which an electronic component 4 such as a semiconductor element is mounted, and the electronic component 4 is mounted on the mounting portion.

When the insulating base 1 is made of, for example, glass ceramic, for example, 18 to 24% by weight of alumina and 8 to 28% of quartz
17% by weight, 13-25% by weight cordierite, the balance consisting of glass ceramics consisting of borosilicate glass, 72-76%
% By weight of silicon oxide. 15 to 17% by weight of boron oxide.
% By weight of alumina, 1.5% by weight or less of magnesium oxide, 1.1 to 1.4% by weight of zirconium oxide and a total amount of 2 to 3
Borosilicate glass powder consisting of lithium oxide, potassium oxide and sodium oxide by weight of 18 to 24% by weight of alumina powder; 8 to 17% by weight of quartz powder; 13 to 25% by weight of cordierite powder and a suitable organic binder・ Slurry by adding and mixing solvent, plasticizer, dispersant, etc.
A green sheet (raw sheet) is obtained by forming the slurry into a sheet using a well-known doctor blade method or calender roll method. Thereafter, an appropriate punching process is performed on the green sheet, and a plurality of sheets are vertically moved. To form a green sheet laminate, and finally firing the green sheet laminate at a temperature of about 900 ° C.

A large number of wiring conductors 2 mainly composed of copper are formed on the insulating base 1 from the mounting portion on the upper surface to the lower surface, and the electronic component 4 is mounted on the mounting portion of the wiring conductor 2. Are electrically connected via the solder 5,
Further, a portion of the lower surface of the insulating base 1 of the wiring conductor 2 is electrically connected to an external electric circuit board (not shown) via the solder 6.

The wiring conductor 2 containing copper as a main component is prepared by, for example, adding 72 to 76% by weight of silicon oxide, 15 to 17% by weight of boron oxide, 2 to 4% by weight of alumina, and 1.5% by weight or less of oxidized copper powder. Copper paste obtained by adding and mixing borosilicate glass powder consisting of magnesium, 1.1 to 1.4% by weight of zirconium oxide and lithium oxide, potassium oxide, and sodium oxide in a total amount of 2 to 3% by weight, and an appropriate organic binder and solvent. Is applied onto a green sheet serving as the insulating base 1 and baked together with the green sheet serving as the insulating base 1, whereby the insulating base 1 is applied from the upper surface to the lower surface of the mounting portion.

Further, the wiring conductor 2 mainly composed of copper is
On its surface, a copper plating layer 3 having a thickness of 2 to 10 μm is applied.

The copper plating layer 3 fills minute recesses having a diameter of 1 to 2 μm formed on the surface of the wiring conductor 2 containing copper as a main component, and each electrode of the wiring conductor 2 and the electronic component 3 and an external electric circuit. It has the effect of improving the connection with the wiring conductor of the substrate via solder, and as shown in FIG. 2 in an enlarged sectional view of the main part of FIG. Copper plating layer region 3a having a crystal grain size of 0.1 to 0.3 μm and a copper plating layer having a crystal grain size of 0.5 to 1.0 μm deposited on copper plating layer region 3a having a crystal grain size of 0.1 to 0.3 μm. Area 3b
It is composed of

The copper plating layer region 3a having a crystal grain size of 0.1 to 0.3 μm on the side in contact with the wiring conductor 2 containing copper as a main component is
The copper plating layer 3 has an action of closely contacting the wiring conductor 2 containing copper as a main component without any gap, and has a crystal grain size of 0.1 to 0.3 μm.
, It penetrates satisfactorily into the minute dent formed on the surface of the wiring conductor 2 containing copper as a main component and having a diameter of about 1 to 2 μm, and closely adheres to the wiring conductor 2 containing copper as a main component. can do. Therefore, a large amount of minute voids are not formed between the wiring conductor 2 mainly composed of copper and the copper plating layer 3, and even if heat is applied to the wiring board of the present invention, the copper mainly contains copper. No swelling or peeling occurs between the wiring conductor 2 and the copper plating layer 3.

The copper plating layer region 3a on the side in contact with the wiring conductor 2 mainly composed of copper has a crystal grain size of 0.1 μm.
It is practically difficult to reduce the diameter to less than 0.3 μm. On the other hand, if the crystal grain size exceeds 0.3 μm, the diameter formed on the surface of the wiring conductor 2 containing copper as a main component is as small as about 1 to 2 μm. There is a tendency that it is difficult to get into the recess and adhere closely without any gap. Therefore, the wiring conductor 2 mainly composed of copper
The copper plating layer region 3a on the side in contact with
It is specified in the range of 0.1 to 0.3 μm.

The copper plating layer region 3 having a crystal grain size of 0.1 to 0.3 μm on the side in contact with the wiring conductor 2 containing copper as a main component.
If a is less than 0.1 μm, the copper plating layer 3 having a thickness of 2 to 10 μm cannot be firmly adhered to the surface of the wiring conductor 2 containing copper as a main component without gaps. Therefore,
The crystal grain size on the side contacting the wiring conductor 2 mainly composed of copper is
The thickness of the copper plating layer region 3a of 0.1 to 0.3 μm is 0.
It is specified to be 1 μm or more.

In order to deposit the copper plating layer 3 having a crystal grain size of 0.1 to 0.3 μm on the surface of the wiring conductor 2 mainly composed of copper, the wiring conductor 2 mainly composed of copper is coated on the surface. The attached insulating substrate 1 contains a small amount of sulfur in a conventionally well-known high-temperature electroless copper plating solution containing, for example, copper sulfate, EDTA-2Na, formaldehyde, bipyridyl, polyethylene glycol, and the like. It may be immersed for several hours.

However, the electroless copper plating solution containing a small amount of sulfur has a very low deposition rate of the copper plating layer as compared with the electroless copper plating solution containing no sulfur, and the wiring conductor containing copper as a main component. If the copper plating layer region 3a having a crystal grain size of 0.1 to 0.3 .mu.m is deposited on the surface of No. 2 to a thickness of 0.5 .mu.m or more, it takes a long time for the deposition and the productivity of the wiring board becomes extremely poor. . Therefore, the copper plating layer region 3a having a crystal grain size of 0.1 to 0.3 μm, that is, the thickness region 3a at least 0.1 μm or more from the surface in contact with the wiring conductor 2 to be adhered to the wiring conductor 2 mainly containing copper is 0.5 thickness
It is preferable that the thickness be less than μm.

Further, the crystal is deposited on the outer region of the thickness region 3a of at least 0.1 μm or more from the surface in contact with the wiring conductor 2, that is, on the copper plating layer region 3a having a crystal grain size of 0.1 to 0.3 μm. The copper plating layer region 3b having a particle size of 0.5 to 1.0 μm covers the copper plating layer region 3a and covers the copper plating layer 3a.
It is for making the surface of the surface smooth, for example,
The crystal grain size of the wiring conductor 2 mainly composed of copper is 0.1 to 0.3 μm.
After the copper plating layer region 3a having a thickness of m is deposited, the copper plating layer region 3a is put in a conventionally well-known electroless copper plating solution containing, for example, copper sulfate, EDTA-2Na, formaldehyde, bipyridyl, polyethylene glycol, etc. and containing no sulfur. It is applied by sufficiently immersing. In this case, the sulfur-free electroless copper plating solution has an extremely high deposition rate of the copper plating layer as compared with the above-described sulfur-containing electroless copper plating solution, and therefore, the wiring conductor mainly containing copper is used. The copper plating layer 3 having a thickness of 2 to 10 μm can be efficiently applied to the surface of the substrate 2 in a short time.

Thus, according to the wiring board of the present invention, the copper plating layer 3 having a thickness of 2 to 10 μm is firmly adhered to the surface of the wiring conductor 2 containing copper as a main component without forming a gap between them. Even if heat is applied to the wiring board when the wiring conductor 2 is connected to the electrodes of the electronic component 4 or the external electric circuit board via the solders 5 and 6, etc., the wiring mainly composed of copper is used. It is possible to provide a wiring board in which swelling and peeling do not occur between the conductor 2 and the copper plating layer 3.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in one example of the above-described embodiment, a copper paste to be a wiring conductor 2 is printed on a green sheet to be an insulating substrate 1 and is printed on the insulating substrate 1.
The wiring conductor 2 containing copper as a main component is applied to the surface of the insulating base 1 by firing together with the green sheet to be used. A paste in which the wiring conductor 2 mainly composed of copper is adhered to the surface of the insulating base 1 by printing and applying a paste and baking the paste may be used.

Further, in one example of the above-described embodiment, the copper plating layer 3 applied to the surface of the wiring conductor 2 containing copper as a main component has the crystal grain size formed on the surface contacting the wiring conductor 2. But
Thickness area 3 of at least 0.1 μm of 0.1-0.3 μm
a (copper plating layer region 3a) and an outer region 3b of the thickness region 3a, that is, a copper plating layer region 3b having a crystal grain size of 0.5 to 1.0 μm deposited on the copper plating layer region 3a. However, the copper plating layer 3 has a crystal grain size of 0.1
It may be composed of only a copper plating layer having a thickness of 2 μm to 10 μm.

Further, a thickness region 3 a (copper plating layer region 3
The outer region of a) may be formed by laminating a plurality of copper plating layer regions.

[0032]

[Example] 20% by weight of alumina, 12% by weight of quartz, 18% by weight of cordierite, the balance being 10 mm in width made of borosilicate glass
× 10 mm long × 1 mm thick glass ceramic substrate surface, 75 wt% silicon oxide, 16 wt% boron oxide, 3.5 wt% alumina, 1.3 wt% magnesium oxide, 1.2 wt% zirconium oxide and lithium oxide / potassium oxide A copper metallization containing 5% by weight of borosilicate glass having a total of 3% by weight of sodium oxide is 0.5 mm wide and 5 m long.
It was applied in a pattern of mx 20 μm thickness.

Then, on the copper metallization pattern of this glass ceramic substrate, the thickness region (copper plating layer region 3a) on the surface side in contact with the wiring conductor having the crystal grain size and thickness shown in Table 1 and the outer region (copper plating region) Plating layer area 3b)
Were sequentially applied to form copper plating layers, thereby preparing five samples each.

The copper plating solution for depositing the copper plating layer region 3a is copper sulfate 10 g / liter · ED.
TA-2Na 30g / liter formaldehyde (37%
Solution) A plating solution containing 3 cc / liter of biviridyl and polyethylene glycol in a small amount and 0.01 to 0.1% of thiodiacetic acid as a sulfur compound is used. The plating solution for depositing the copper plating layer region 3b is as follows. A plating solution excluding a sulfur compound was used.

Then, these samples were heated at a temperature of 350 ° C. for 1 hour.
After the exposure, whether or not swelling or peeling occurred between the copper metallization and the copper plating layer was observed with a metallographic microscope. Table 1 shows the results. Sample numbers 1 and 2 marked with * in Table 1 are comparative examples outside the scope of the present invention, and the crystal grain size of the copper plating layer region on the surface side in contact with the wiring conductor containing copper as a main component was determined. A comparative example in which the thickness of the copper plating layer region on the side in contact with the wiring conductor containing copper as a main component is less than 0.1 μm.

[0036]

[Table 1]

As shown in Table 1, in Samples 3 to 7 within the scope of the present invention, no peeling occurred between the wiring conductor mainly containing copper and the copper plating layer. In addition, although the sample 7 showed good results without peeling, it took a long time to adhere.

On the other hand, in Comparative Example Sample 1 having a crystal grain size of more than 0.3 μm in the copper plating layer region on the surface contacting with the wiring conductor containing copper as a main component and Comparative Example Sample 2 having a thickness of less than 0.1 μm, Peeling occurred between the wiring conductor containing copper as a main component and the copper plating layer in all cases.

As is clear from the above, according to the wiring board of the present invention, even if heat is applied during soldering or the like, swelling or peeling occurs between the wiring conductor mainly composed of copper and the copper plating layer. It was confirmed that no problem occurred.

[0040]

As described above, according to the present invention, a wiring conductor mainly composed of copper is applied to the surface of an insulating substrate, and a copper plating having a thickness of 2 to 10 μm is formed on the surface of the wiring conductor. In the wiring board formed by applying the layer, since the crystal grain size in the region of at least 0.1 μm or more from the surface in contact with the wiring conductor of the copper plating layer is 0.1 to 0.3 μm, the wiring containing copper as a main component A copper plating layer is applied to the surface of the conductor without forming a gap between them, and even if heat is applied to these, swelling may occur between the copper-based wiring conductor and the copper plating layer. It was possible to provide a wiring board free from peeling.

Further, according to the present invention, when the crystal grain size in the region outside the thickness region on the side of the copper plating layer in contact with the wiring conductor is 0.5 to 1.0 μm,
The surface of the copper plating layer can be made smooth, and the outer region can be formed by an electroless copper plating solution that does not contain sulfur and has a very high deposition rate. A copper plating layer having a thickness of 2 to 10 μm can be efficiently adhered on the surface in a short time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an embodiment of a wiring board of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the wiring board shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Insulating base 2 ... Wiring conductor mainly composed of copper 3 ... Copper plating layer 3a having a thickness of 2 to 10m 3a ... At least 0.1m from the surface in contact with wiring conductor 2
The above thickness region (a copper plating layer region having a crystal grain size of 0.1 to 0.3 μm) 3b..A region outside the thickness region 3a (a crystal grain size of 0.5 to 1.
0 μm copper plating layer area)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Koichi Motomura 1-1, Yamashita-cho, Kokubu-shi, Kagoshima F-term in the Kokubu Plant of Kyocera Corporation (reference) 4E351 AA07 AA09 AA11 BB31 BB33 BB35 CC06 CC12 DD04 GG02 5E343 AA02 AA24 BB24 BB72 BB75 BB76 CC78 DD43 ER33 GG01

Claims (2)

[Claims] 1. A wiring board comprising a wiring conductor mainly composed of copper adhered to the surface of an insulating substrate and a copper plating layer having a thickness of 2 to 10 μm adhered to the surface of the wiring conductor. A wiring board, wherein the plating layer has a crystal grain size of 0.1 to 0.3 μm in a thickness region of at least 0.1 μm or more from a surface in contact with the wiring conductor. 2. The wiring board according to claim 1, wherein a crystal grain size in a region outside the thickness region of the copper plating layer is 0.5 to 1.0 μm.