JPH08102580A - Ceramic printed wiring board and its manufacture - Google Patents

Abstract

PURPOSE: To provide a ceramic printed wiring board and a method of manufacturing the same which can prevent the fall of capability for close contactness of a conductive circuit due to diffusion of the tin element of solder without deteriorating die-bonding and wire-bonding capability. CONSTITUTION: In a ceramic printed wiring board 5 where a conductive circuit portion is formed on a ceramic substrate 1 with inclusion of an under layer 2 of copper layer 2c, an intermediate layer 3 of paradium layer 3p and a surface layer 4 of a gold layer 4a, a metal layer 6 including cobalt or nickel is formed in the area between the ceramic substrate 1 and copper layer 2c in the part where parts are soldered with a solder 7. Thickness of metal layer 6 is 0.3 to 1.5μm. A metal layer 6 is formed by coating the ceramic substrate 1 with a paste including cobalt or nickel and then baking the surface at 600 to 950 deg.C under the nitrogen atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic printed wiring board used in electronic equipment such as mobile phones and tape recorders, and a method for manufacturing the same.

[0002]

When a semiconductor chip is mounted on a conductor circuit portion formed on a ceramic substrate by die bonding, a gold silicon eutectic plate is interposed between the semiconductor chip and the conductor circuit portion whose surface is a gold layer. , Heating and joining are performed. Since the gold layer is made into a gold-silicon eutectic alloy by heating, forming the surface of the conductor circuit portion as a gold layer is an effective means for obtaining a strong bonding strength in such bonding. Since such bonding is usually performed under a temperature condition of about 450 ° C., the ceramic wiring board used is required to withstand heating at about 450 ° C.

On the other hand, as a method for forming a fine conductor circuit portion on a ceramic substrate, a thin copper layer as an underlayer is formed on the ceramic substrate by electroless plating, and then a desired pattern is formed by a plating resist, and then a desired pattern is formed. After forming a metal layer on the copper layer not covered by the plating resist by electrolytic plating, the plating resist is peeled off, and the copper layer in the non-conductor circuit part is removed by etching to form a conductor circuit part, so-called A method of forming a conductor circuit portion by a semi-additive method is known.

A ceramic wiring board which is capable of forming a fine conductor circuit portion by a semi-amidative method, and has a conductor circuit portion whose surface is a gold layer. When the gold layer is directly placed on the gold layer, the copper of the underlayer diffuses to the surface of the gold layer by heating at around 450 ° C., so that there is a problem that the semiconductor chip cannot be firmly bonded by die bonding. Therefore, in order to solve this problem, there is known a configuration in which a nickel layer is arranged as an intermediate metal layer between the copper layer and the gold layer. However, in this case, when the gold layer is thin, nickel diffuses to the surface of the gold layer, and when the nickel layer is thin, the nickel layer does not function as a barrier for copper diffusion and copper diffuses to the surface of the gold layer. However, if the gold layer and the nickel layer are both thickened, the diffusion of copper or nickel to the surface of the gold layer is prevented.
Since a new problem that blisters are likely to occur in the conductor circuit section due to heating at around ℃, improvement of these problems has been desired.

[0005]

Therefore, the inventors of the present invention, as shown in FIG. 2, have a ceramic printed wiring board 5 in which the underlayer 20 is a copper layer 20c and the surface layer 40 is a gold layer 40a.
0 which is generated when 0 is heated near 450 ° C.
And the problem that the bondability at the time of die bonding or wire bonding is impaired by the diffusion of the metal of 50 to the surface of the gold layer 40a.
In order to solve the problem of blistering in the conductor circuit portion due to heating at around 0 ° C., the conductor circuit portion can be wire-bonded after die bonding for mounting a semiconductor chip on the conductor circuit portion on the ceramic substrate. As the base layer 20, the copper layer 20 is formed on the ceramic substrate.
Japanese Patent Application No. 6-7382 proposes a ceramic printed wiring board 50 in which the conductor circuit portion is formed of the intermediate layer 30 of the palladium layer 30p and the surface layer 40 of the gold layer 40a. However, when a component is mounted on the conductor circuit portion formed of the three layers by using the solder 70 made of tin and lead, when the operating temperature of the conductor circuit portion after mounting is high, tin and lead are There is a drawback that the adhesive strength is reduced due to the mutual diffusion with the conductor circuit layer and the formation of an intermetallic compound of copper tin having a brittle film strength, resulting in the loss of mounted components.

The present invention has been made in view of the above circumstances. An object of the present invention is to form a base layer with a copper layer, an intermediate layer with a palladium layer, and a surface layer with a gold layer. In a ceramic printed wiring board on which a conductor circuit portion is formed, a ceramic printed wiring board capable of preventing a decrease in adhesion of the conductor circuit portion due to diffusion of tin components of solder without impairing die bonding property and wire bonding property, and It is to provide the manufacturing method.

[0007]

In a ceramic printed wiring board according to a first aspect of the present invention, a base layer 2 is a copper layer 2c, an intermediate layer 3 is a palladium layer 3p, and a surface layer 4 is a gold layer on a ceramic substrate 1. In the ceramic printed wiring board 5 in which the conductor circuit portion is composed of 4a, the metal layer 6 containing cobalt or nickel is formed between the ceramic substrate 1 and the copper layer 2c in the portion where the component is soldered with the solder 7. It is characterized by being done.

In the ceramic printed wiring board according to claim 2 of the present invention, the thickness of the metal layer 6 is 0.3 to 1.5 μm.
It is characterized by being m.

In the method for manufacturing a ceramic printed wiring board according to a third aspect of the present invention, a paste in which the metal layer 6 contains cobalt or nickel is applied to the ceramic substrate 1 and fired at 600 to 950 ° C. in a nitrogen atmosphere. It is characterized by being formed by.

Hereinafter, the present invention will be described in detail. As the ceramic substrate 1 shown in FIG. 1 used in the present invention, an alumina substrate, an aluminum nitride substrate, a silicon carbide substrate,
A glass substrate or the like is used. Although it is possible to directly form the conductor circuit portion on these ceramic substrates 1, it is preferable to use a ceramic substrate 1 having a roughened surface in order to increase the adhesion of the plated conductors. More preferably, the ceramic substrate 1 in which an alumina-based substrate is chemically roughened by phosphoric acid treatment is most suitable. The metal layer 6 in the present invention is formed by using a material composed of conductive fine powder containing cobalt or nickel, a chemically resistant glassy frit and an organic vehicle, for example, by printing by screen printing and then firing. It is a thing.

As shown in FIG. 1, a ceramic printed wiring board according to the present invention has a base layer 2 on a ceramic substrate 1.
Is a ceramic printed wiring board 5 having a conductor circuit portion formed by a copper layer 2c formed by electroless plating, a palladium layer 3p on the intermediate layer 3, and a gold layer 4a on the surface layer 4, and solder 7 A metal layer 6 containing cobalt or nickel is formed between the ceramic printed wiring board 5 of the portion to be attached and the copper layer 2c which is the underlayer 2. The formation of this metal layer 6 is because the formation rate of the intermetallic compound of the tin component in the solder 7 and cobalt or nickel in the solder 7 is extremely slower than the production rate of the intermetallic compound of the tin component and copper. And has an effect of prolonging the time required for the intermetallic compound to reach the interface between the metal layer 6 of cobalt or nickel. As a result, it is possible to significantly delay the deterioration of the adhesive force and significantly improve the aging characteristics.

The thickness of the metal layer 6 is 0.3 to 1.5 μm.
It is preferably m. That is, when the film thickness of the metal layer 6 is less than 0.3 μm, the effect of delaying the diffusion of the tin component cannot be sufficiently exerted, and the film thickness at which the metal layer 6 can be easily formed by screen printing is 1.5 μm. Therefore, 1.
If it exceeds 5 μm, it takes a lot of time and effort to form the metal layer 6.

In the method for manufacturing a ceramic printed wiring board according to the present invention, a paste containing cobalt or nickel is applied to the ceramic substrate 1 by, for example, screen printing, and the paste is baked at 600 to 950 ° C. in a nitrogen atmosphere. The metal layer 6 is formed. That is, when the metal layer 6 is not formed under the firing condition of less than 600 ° C., the film state of the obtained metal layer 6 becomes porous, and it becomes impossible to sufficiently prevent the diffusion of the tin component. If the metal layer 6 is not formed under a firing condition of higher than 0 ° C., cracks are likely to occur in the conductor circuit portion,
The adhesion of the conductor circuit portion tends to decrease. The copper layer 2c, the palladium layer 3p, and the gold layer 4a in the present invention are formed by an ordinary thin film method, and include, for example, an electroless plating method, a vacuum vapor deposition method, a sputtering method, and the like. It is possible to use an electroplating method for the formation of, and there is no particular limitation. Further, these film thicknesses do not need to be limited in the sense that the adhesion strength is prevented from lowering due to the diffusion of the solder component of the present invention.

[0014]

In the ceramic printed wiring board according to the first aspect of the present invention, the metal layer 6 containing cobalt or nickel is provided between the ceramic substrate 1 and the copper layer 2c at the portion where the component is soldered with the solder 7. Since the formation rate of the intermetallic compound of the tin component and cobalt or nickel is extremely slower than that of the intermetallic compound of the tin component and copper, the ceramic substrate 1 and the metal layer 6 of cobalt or nickel are formed. It has an effect of prolonging the time for the intermetallic compound to reach the interface, and has the effect of delaying the diffusion of the tin component, and it is difficult for the tin component to reach the interface with the ceramic substrate 1.

In the ceramic printed wiring board according to claim 2 of the present invention, the film thickness of the metal layer 6 is 0.3 to 1.5.
Since it is μm, it has an effect of delaying the diffusion of the tin component, the tin component hardly reaches the interface with the ceramic substrate 1, and the metal layer 6 can be easily formed by screen printing or the like.

In the method for manufacturing a ceramic printed wiring board according to the third aspect of the present invention, the paste in which the metal layer 6 contains cobalt or nickel is applied to the ceramic substrate 1 and fired at 600 to 950 ° C. in a nitrogen atmosphere. Since the metal layer 6 is formed by such a method, the film state of the obtained metal layer 6 does not become porous, cracks and the like are less likely to occur in the conductor circuit portion, and a decrease in the adhesive force of the conductor circuit portion is prevented.

[0017]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
This will be specifically described.

(Examples 1 to 8) By immersing in phosphoric acid heated to 300 ° C., as shown in FIG.
96% alumina white ceramic substrate with roughened surface 1
(100 mm x 100 mm x 0.635 mm: manufactured by Matsushita Electric Works, Ltd.), and a commercially available conductor paste (Cobalt A-11).
00 or nickel A-3207: manufactured by Engelhard Indowtry Co., Ltd.) was printed by a screen printing method to a desired film thickness and baked for 10 minutes in a nitrogen atmosphere to form a metal layer 6. In Examples 1 to 4, cobalt (A-1100) was used, and in Examples 5 to 8, nickel (A-3207) was used. The film thickness of the metal layer 6 and the firing temperature are shown in Table 1.
After that, the nucleation step (O
PC process AC: manufactured by Okuno Seiyaku Kogyo Co., Ltd., and then electroless copper plating is applied to the entire surface to form 1 μm of the copper layer 2c of the underlayer 2.
A copper film of about m was formed. However, the electroless copper plating bath composition is CuSO ₄ .5H ₂ O; 10 g / liter, E
DTA · 2Na; 30 g / liter, formalin;
3 g / liter, polyethylene glycol (PEG # 1
000: manufactured by Nacalai Tesque, Inc.); 5 ml / liter, pH adjusted to 12 with NaOH.
No. 4 electroless copper plating was performed at a temperature of 60 ° C.

Next, a dry film (Liston 462)
0: DuPont Japan Limited) is laminated, a resist pattern is formed using a mask through which the non-conductor circuit part transmits light, and the conductor circuit part is commercially available electroplating bath (Paradex Strike: EEJA company). ), And a secondary electroplating bath (Paradex 110: manufactured by EEJA)
To form a palladium layer 3p, which is an intermediate layer 3, and then a commercially available electro-gold plating bath (Orobond TN: EEJ).
Company A) and secondary electroplating bath (Templex 40)
The gold layer 4a of the surface layer 4 was formed by electroplating (1: manufactured by EEJA). After that, the resist is stripped by immersing it in an aqueous solution of 3% sodium hydroxide, and then the copper-plated portion is treated with sodium persulfate and sulfuric acid (12
Etching was performed with an aqueous solution of 5 g, 40 ml / liter) to remove copper in the non-conductor circuit portion, followed by washing with water and drying to obtain a ceramic printed wiring board 5. Solder 7 to this ceramic printed wiring board 5
The adhesive strength of each layer by pulling 2 mm
The L-shaped peel strength before and after aging in a pattern of × 2 mm was measured, and these values are shown in Table 1. Aging was performed under the conditions of 150 ° C. and 250 hours. A peel strength of 1 kgf / 4 mm ² or more was regarded as acceptable.

[0020]

[Table 1]

Comparative Examples 1 to 5 In the same manner as in Example 1, a ceramic printed wiring board 5 was obtained with the film thickness of the metal layer 6 and the firing temperature shown in Table 1. However, Comparative Example 1 was performed by a conventional method in which the metal layer 6 was not formed, Comparative Example 2 and Comparative Example 3 used cobalt (A-1100), and Comparative Example 4 and Comparative Example 5 used nickel ( A-320
The values of L-shaped peel strength before and after aging are shown in Table 1 in the same manner as in Example 1 using 7).

From the results shown in Table 1, it was confirmed that the examples had a larger adhesion to the conductor circuit portion than the comparative examples.

[0023]

Since the ceramic printed wiring board according to the first and second aspects of the present invention is configured as described above, the ceramic printed wiring board according to the first and second aspects of the present invention is used. With this, it is possible to prevent the adhesion force of the conductor circuit portion from being lowered due to the diffusion of the tin component of the solder.

Since the method for manufacturing a ceramic printed wiring board according to claim 3 of the present invention is configured as described above, according to the method for manufacturing a ceramic printed wiring board according to claim 3 of the present invention, solder It is possible to obtain a ceramic printed wiring board in which a decrease in the adhesion of the conductor circuit portion due to the diffusion of tin components is prevented.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a method for manufacturing a ceramic printed wiring board according to an example of the present invention.

FIG. 2 is an explanatory cross-sectional view of a method for manufacturing a ceramic printed wiring board according to a conventional example.

[Explanation of symbols]

 1 Ceramic Substrate 2 Underlayer 2c Copper Layer 3 Intermediate Layer 3p Palladium Layer 4 Surface Layer 4a Gold Layer 5 Ceramic Printed Wiring Board 6 Metal Layer 7 Solder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Daisuke Kanaya 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (3)

[Claims] 1. An underlayer (2) on a ceramic substrate (1).
Is the copper layer (2c), the intermediate layer (3) is the palladium layer (3
p), in the ceramic printed wiring board (5) in which the surface layer (4) is composed of the conductor layer by the gold layer (4a), the metal layer (6) containing cobalt or nickel causes the component to be soldered (7). A ceramic printed wiring board, which is formed between a ceramic substrate (1) and a copper layer (2c) in a portion to be soldered. 2. The metal layer (6) has a thickness of 0.3 to
The ceramic printed wiring board according to claim 1, wherein the thickness is 1.5 μm. 3. The metal layer (6) is formed by applying a paste containing cobalt or nickel to the ceramic substrate (1) and firing the paste at 600 to 950 ° C. in a nitrogen atmosphere. A method for manufacturing a ceramic printed wiring board according to claim 1 or 2.