TW201831433A - Ceramic circuit board and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a ceramic circuit board including an aluminum nitride substrate; a bonding layer including a metal oxide of a spinel structure and formed on the aluminum nitride substrate; and a metal layer formed on the bonding layer, wherein at least one of the bonding layer and the metal layer includes glass frit, and a method of manufacturing the same.

Description

Ceramic circuit board and manufacturing method thereof

The present invention relates to a ceramic circuit board and a method of fabricating the same.

Ceramics have excellent heat resistance and mechanical strength, and high insulation resistance, and are used as materials for high-power semiconductor device substrates, and can supply high-voltage to high-power semiconductor device substrates. The ceramic material comprises alumina (Al ₂ O ₃ ), aluminum nitride (AlN), zirconium dioxide (ZrO ₂ ), silicon carbide (SiC), tantalum nitride (silicon) Nitriding; Si3N4), etc., and depending on their flexural strength and thermal conductivity properties, they are used in automobiles, high-speed railways, industrial parts, and the like. Among the materials, aluminum nitride has an excellent thermal conductivity of 150-250 W/Mk and can be used as a substrate on which a semiconductor device is mounted, which emits a large amount of heat during operation.

The method for forming an electrode layer using aluminum nitride as a circuit board includes a direct bonding copper (DBC) method, an active metal bonding (AMB) method, and a metallization method. The method of directly joining copper includes heating aluminum nitride to form an aluminum nitride layer on the surface thereof, and heating and joining a copper metal plate thereon to form an electrode layer. The activated metal joining method includes printing a solder paste containing a TiAgCu metal powder, and heating and joining the copper metal thereon to form an electrode layer. The metallization process involves printing/sintering a metal powder paste such as copper, tungsten, molybdenum to form an electrode layer.

Among the methods, for example, a metallization method, Japanese Laid-open Patent Publication No. Hei 5-320943 discloses that a nitrogen is obtained by a binder containing a specific amount of Al ₂ O ₃ , SiO ₂ , WO, or the like. A method of excellent joint strength and heat resistance between an aluminum substrate and a tungsten metal layer. However, it is not possible to apply this patent to metals other than tungsten and may limit the scope of use.

In addition, Japanese Laid-Open Patent Publication No. Sho 50-75208 discloses a method of forming a metal layer of molybdenum or tungsten on a metallized aluminum nitride substrate, wherein aluminum nitride is heated to form Al ₂ O ₃ on the surface to improve adhesion strength. Thereby, a spinel structure is formed between Al ₂ O ₃ and Mn-Ti in the dope and the joint strength is improved. However, even with expensive cements, this method has a limit in achieving satisfactory joint strength.

Therefore, there is a need to develop a ceramic circuit board that satisfies excellent joint strength and thermal properties between an aluminum nitride substrate and a metal layer.

(Patent Document 1) Japanese Laid-Open Patent Publication No. Hei 5-320943

(Patent Document 2) Japanese Laid-Open Patent Publication No. Sho 50-75208

technical problem

One aspect of the present invention provides a ceramic circuit board having a metal layer and an aluminum nitride substrate having high joint strength and thermal properties for fabricating a ceramic circuit board for mounting a semiconductor device.

Another aspect of the present invention provides a method of manufacturing a ceramic circuit board by which the above effects can be attained and the manufacturing cost can be reduced.

Technical solution

The present invention provides a ceramic circuit board comprising an aluminum nitride substrate; a connection layer of a metal oxide including a spinel structure is formed on the aluminum nitride substrate; and a metal layer is formed on the connection layer, wherein the connection layer and the metal layer are at least One of them includes a glass frit.

Further, the present invention provides a method of manufacturing a ceramic circuit board comprising supplying CuO powder on an aluminum nitride substrate and performing an oxidative heat treatment to form a connection layer of CuAl ₂ O ₄ including a spinel structure; and printing a metal paste ( Metal paste) is sintered on a spinel structure of CuAl ₂ O ₄ to form a metal layer.

Beneficial effect

The ceramic circuit board of the present invention comprises a connection layer of a metal oxide comprising a spinel structure on the aluminum nitride substrate, on the connection layer with the metal layer, and comprising a glass frit in at least one of the connection layer and the metal layer. Due to the spinel structure of the connection layer and the combination of the glass frit and the dope component of the metal layer, the strong connection strength between the metal layer and the aluminum nitride substrate can be achieved, and the thermal properties can be further improved. In addition, the manufacturing cost of the ceramic circuit board can be reduced while achieving excellent physical properties.

The invention is described in more detail below to facilitate an understanding of the invention.

The words or terms used in the description and the scope of the patent should not be interpreted in the sense defined in the commonly used dictionary. It will be better understood that words or terms should be interpreted as having the meaning that the inventor can appropriately define the terms to best explain the principles of the invention.

Ceramic circuit board

As shown in FIG. 1, a ceramic circuit board 100 according to an embodiment of the present invention includes an aluminum nitride (AlN) substrate 101, a connection layer 102 and a metal layer 103, and a connection layer 102 is formed on the aluminum nitride substrate 101. And a metal oxide containing a spinel structure formed on the connection layer 102.

The aluminum nitride substrate 101 has excellent thermal conductivity and electrical insulating properties, and can be an optimum material for mounting a substrate of a semiconductor device that emits a large amount of heat during operation.

According to an embodiment of the present invention, the connection layer 102 of the metal oxide including the spinel structure may include CuAl ₂ O ₄ , and the thickness of the connection layer 102 may be in the range of 10 to 1,000 nm and in the range of 10 to 400 nm. And in the range of 50 to 200 nm. If the thickness of the connection layer 102 is less than the above range, the formation region of the metal oxide of the spinel structure may be narrow, and the realization of the excellent connection strength in accordance with the object of the present invention may become different. If the thickness is larger than the above range, bubbles may be partially generated after printing.

The spinel structure of CuAl ₂ O ₄ can be formed by supplying CuO powder on the aluminum nitride substrate 101 and performing an oxidative heat treatment.

The metal layer 103 may contain a metal powder containing Cu, Ag, or a mixture thereof, and may have a thickness in the range of 3 to 300 μm, in the range of 5 to 200 μm, and in the range of 10 to 100 μm. .

In the ceramic circuit board according to an embodiment of the present invention, at least one of the connection layer 102 and the metal layer 103 may include a glass frit.

In this case, if the glass frit is included in the tie layer 102, the weight ratio of the metal oxide to the glass frit may be 1:2.53 to 4.18. If the weight ratio of the glass frit deviates from the numerical range, the resistance of the electrode circuit may increase, and current-related problems may occur.

If the glass frit is contained in the metal layer 103, the weight ratio of the metal powder to the glass frit may be 0.05 to 0.1. If the weight ratio of the glass frit deviates from the numerical range, the resistance of the electrode circuit may increase, and current-related problems may occur. In addition, the physical properties of solderability and wire bondability may be significantly degraded, and the mounting of wafers or components may become difficult, causing problems associated with module assembly.

The glass frit may comprise a calcium silicate-based glass frit having an average particle diameter of 1.5 to 10.5 μm. The aluminum nitride substrate generally lacks a glass phase and has a problem of low connection strength with the metal layer 103. The ceramic circuit board of the present invention comprises a connection layer 102 of a metal oxide containing a spinel structure on the aluminum nitride substrate 101, and a metal layer 103 on the connection layer 102, and at least the connection layer 102 and the metal layer 103 One contains glass frit. Due to the spinel structure of the connection layer 102 and the bonding between the dope component of the metal layer 103 and the glass frit, a strong connection strength between the metal layer 103 and the aluminum nitride substrate 101 can be achieved. In addition, due to thermal properties, such as thermal cycle test (TCT) physical properties can be further improved, even after repeated application of current for a long time, the metal layer 103 can be separated from the ceramic circuit board, and can improve reliability .

2. Method for manufacturing ceramic circuit board

The details of the respective elements constituting the ceramic circuit board according to the embodiment of the present invention will be specifically described with reference to the following processes.

A method of manufacturing a ceramic circuit board according to an embodiment of the present invention may include supplying CuO powder on an aluminum nitride substrate and performing an oxidative heat treatment to form a connection layer of CuAl ₂ O ₄ containing a spinel structure (step (a)); And printing the metal paste on the spinel structure of CuAl ₂ O ₄ and sintering to form a metal layer (step (b)).

Fig. 2 is a flow chart showing a method of manufacturing a ceramic circuit board according to an embodiment of the present invention.

Referring to FIG. 2 in detail, in the method of manufacturing a ceramic circuit board according to an embodiment of the present invention, the step (a) may be to supply CuO powder on the aluminum nitride substrate (a1) and perform an oxidation heat treatment (a2). A step of forming a connection layer of CuAl ₂ O ₄ containing a spinel structure.

The CuO powder supplied on the aluminum nitride substrate may have an average particle diameter of 1 to 50 μm, 2 to 40 μm, and 3 to 20 μm. The CuO powder can be supplied in an amount of 5 x 10 ^-3 mg to 10 x 10 ^-3 mg per 1 cm ² of the aluminum nitride substrate. If the amount of the CuO powder is less than the above range, the supply amount of the CuO powder is too small, and the amount of formation of CuAl ₂ O ₄ becomes too small. On the other hand, if the amount of the CuO powder is larger than the above range, the problem of partial generation of bubbles may occur.

The oxidative heat treatment can be carried out at a temperature ranging from 1,000 ° C to 1,200 ° C, more particularly from 1,100 ° C to 1,150 ° C for about 10 minutes to 30 minutes. The oxidative heat treatment process can be carried out, for example, in a box furnace. According to an embodiment of the present invention, the optimum joint strength and thermal properties can be achieved within the temperature range of the oxidative heat treatment, particularly in the temperature range of 1,100 ° C to 1,150 ° C.

By the oxidative heat treatment, a spinel structure of CuAl ₂ O ₄ can be formed on the aluminum nitride substrate, and the formation mechanism of CuAl ₂ O ₄ can be as follows in Reaction 1 and Reaction 2.

[Reaction 1]

AlN + O ₂ → Al ₂ O ₃ + NO _x

Where x is 0 or 2.

[Reaction 2]

CuO + Al ₂ O ₃ → CuAl ₂ O ₄

In particular, after the CuO powder is supplied on the aluminum nitride substrate, aluminum nitride on the surface of the aluminum nitride substrate can be oxidized by oxidative heat treatment to form Al ₂ O ₃ (Reaction 1). Further, the thus formed Al ₂ O ₃ can react with the supplied CuO to form a spinel structure of CuAl ₂ O ₄ (Reaction 2).

If the oxidizing heat treatment time is too short, the reaction may not proceed, and if the oxidizing heat treatment time is too long, contact of Al and O may not be allowed during formation of the Al ₂ O ₃ film on the surface of the aluminum nitride, and Al ₂ O ₃ The rate of growth of the membrane may be reduced.

Further, if the temperature of the oxidative heat treatment is less than the above temperature range, the oxidation reaction may not proceed, and if the temperature is greater than the above temperature range, the thickness of the Al ₂ O ₃ film may increase, and contact with the oxide layer may be deteriorated, oxide The layer has a weak affinity for AlN.

In the method of manufacturing a ceramic circuit board according to an embodiment of the present invention, as shown in FIG. 2, the step (b) may be printing a metal paste on a spinel structure of CuAl ₂ O ₄ (b1), and sintering. (b2) a step of forming a metal layer.

The metal paste may comprise from 80 to 90 wt% of metal powder and from 10 to 20 wt% of a mixture of glass frit and a binder, the metal powder comprising Cu, Ag, or a mixture thereof.

The linking agent may comprise a commonly used organic linking agent, and the organic linking agent may comprise, for example, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), ethyl cellulose, acrylic acid. Acryl resin and the like. Further, the glass frit may comprise a calcium silicate-based glass frit having an average particle diameter of 1.5 to 10.5 μm.

The metal paste can be printed (b1) by, for example, a screen printing method or a jetting method, and can be dried after printing, for example, at 100 to 150 ° C for about 1 minute to 30 minutes.

Then, sintering may be performed in a temperature range of about 800 ° C to 1,000 ° C under a nitrogen atmosphere for about 30 minutes to 180 minutes (b2), and a metal layer may be formed by laminating the process by lamination. .

According to an embodiment of the present invention, the spinel-structured CuAl ₂ O ₄ can be strongly bonded to the metal powder and the glass frit contained in the metal paste by sintering. Further, the glass frit can be infiltrated into the CuAl ₂ O ₄ of the spinel structure, and a strong connection can be achieved by the penetration.

Accordingly, the connection layer of CuAl ₂ O ₄ containing a spinel structure on the ceramic circuit board may also contain a glass frit. According to an embodiment of the present invention, the weight ratio of the spinel structure of CuAl ₂ O ₄ to the glass frit may be 1:2.53 to 4.18.

Further, the weight ratio of the metal powder contained in the metal layer to the glass frit may be 1:0.05 to 0.1 after the strong connection by sintering.

According to another embodiment of the present invention, if the metal powder contained in the metal paste is Ag, that is, if Ag paste is used, the Cu position of CuAl ₂ O ₄ formed in the connection layer may be replaced by Ag by sintering. In order to form a structure of AgAl ₂ O ₄ , a strong bond is formed with the Ag paste. Accordingly, according to an embodiment of the present invention, the metal powder and the glass frit contained in the metal paste may be contained in the connection layer.

Hereinafter, the present invention will be explained in detail with reference to the following exemplary embodiments. However, the following exemplary embodiments are merely illustrative, and the invention is not limited to the illustrative embodiments.

Example 1

CuO powder having an average particle diameter of 5 μm was supplied on an aluminum nitride (AlN) substrate, and the CuO powder was supplied in an amount of 7.5 x 10 ^-3 mg per 1 cm ² of the aluminum nitride substrate, and was about 1,000 ° C. An oxidative heat treatment was carried out in a box furnace for about 45 minutes to form a spinel structure of CuAl ₂ O ₄ on an aluminum nitride (AlN) substrate.

A copper paste (Tanaka Co., Ltd.) containing about 85 wt% of Cu powder and about 15 wt% of a mixture of glass frit and ethyl cellulose (linker) was printed on a spinel structure of CuAl ₂ O ₄ . After printing, drying is carried out at about 100 to 150 ° C for about 10 minutes, and then sintering is performed at about 900 to 1,000 ° C for about 30 minutes under a nitrogen atmosphere. This procedure was repeated three times to laminate to form a metal layer and to fabricate a sample.

Example 2

The sample was produced by the same method as in Example 1, except that the oxidative heat treatment was carried out at a temperature of 1,100 °C.

Example 3

The sample was produced by the same method as in Example 1, except that the oxidative heat treatment was carried out at a temperature of 1,150 °C.

Example 4

The sample was produced by the same method as in Example 1, except that the oxidative heat treatment was carried out at a temperature of 1,200 °C.

Example 5

The sample was produced by the same method as in Example 1, except that the oxidative heat treatment was carried out at a temperature of 1,000 ° C, and Ag powder was used instead of the Cu powder in the metal paste.

Example 6

The sample was produced by the same method as in Example 1, except that the oxidative heat treatment was carried out at a temperature of 1,100 ° C, and Ag powder was used instead of the Cu powder in the metal paste.

Example 7

The sample was produced by the same method as in Example 1, except that the oxidative heat treatment was carried out at a temperature of 1,150 ° C, and Ag powder was used instead of the Cu powder in the metal paste.

Example 8

The sample was produced by the same method as in Example 1, except that the oxidative heat treatment was carried out at a temperature of 1,200 ° C, and Ag powder was used instead of the Cu powder in the metal paste.

Comparative example 1

A metal paste containing 85 wt% of Cu powder and 15 wt% of a mixture of glass frit and ethylcellulose was printed on an aluminum nitride (AlN) substrate. After printing, drying is carried out at about 100 to 150 ° C for about 10 minutes, and then sintering is performed at about 900 to 1,000 ° C for about 30 minutes under a nitrogen atmosphere. This procedure was repeated three times to laminate to form a metal layer and to fabricate a sample.

Comparative example 2

The sample was produced by the same method as in Comparative Example 1, except that Ag powder was used instead of Cu powder in the metal paste.

Test Example 1: Evaluation of joint strength

The joint strength was evaluated by a pull test method.

In particular, as shown in FIG. 3, in each of the samples (5 x 5 mm SQ size) obtained in Examples 1 to 8 and Comparative Example 1 and Comparative Example 2, the solder melted at 300 ° C was melted to adhere. Cu line (metal film, 204) corresponding to the Cu plating pattern. Then, the Cu wire was stretched in the direction of the arrow in Fig. 3 using a UTM apparatus to measure the joint strength.

Test Example 2: Evaluation of TCT

The thermal cycle test (TCT) is carried out by performing a thermal impact test at a temperature of -55 ° C to 150 ° C and 100, 300, 500, 1,000, 1,500, and 2,000 cycles were performed, and the cycle (the number of occurrences) at which delamination of the aluminum nitride substrate and the metal was generated was examined by scanning acoustic microscopy.

Tables 1 and 2 below are the evaluation results of Test Example 1 and Test Example 2, and the evaluation results of Examples 1 to 4 and Comparative Example 1 in which screen printing was performed using Cu dope are shown in Table 1 below. The evaluation results of Examples 5 to 8 and Comparative Example 2 in which screen printing was performed using Ag paste are shown in Table 2 below.

[Table 1]

As shown in Table 1 above, when compared with Comparative Example 1 in which Cu paste was printed on an aluminum nitride substrate without supplying CuO powder and subjected to oxidation heat treatment, the CuO powder of the present invention was supplied to an aluminum nitride substrate. The examples 1 to ₄ in which the oxidative heat treatment was performed to form the spinel structure of CuAl ₂ O ₄ on the aluminum nitride substrate, and then the Cu paste was printed, showed very excellent joint strength and TCT results.

In particular, in Table 1, when compared with Comparative Example 1, the connection strength of Examples 1 to 4 in the first tensile test was increased by 1.5 to 5 times, and when compared with Comparative Example 1, The joint strength of Examples 1 to 4 in the fifth tensile test was increased by 2 to 5 times.

Further, in the case of TCT, it was found that Comparative Example 1 produced delamination at the 300th cycle, and Examples 1 to 4 produced delamination at the 1,000th or 2,000th cycle. Accordingly, when compared with Comparative Example 1, Examples 1 to 4 showed an improvement in thermal properties of 6 times or more.

At the same time, it was found that the tensile test and the TCT result were significantly changed according to the temperature of the oxidation heat treatment.

In particular, it was found that when compared with Example 1 and Example 4 in which the oxidative heat treatment was carried out at 1,000 ° C and 1,200 ° C, the oxidative heat treatment was carried out at 1,100 to 1,150 ° C after supplying CuO powder. 2 and Example 3 When the tensile test was performed, the joint strength was increased by about 2 to 3 times, and when TCT was measured, two or more times of delamination occurred.

Accordingly, it was found that if the oxidative heat treatment is carried out at 1,100 to 1,150 ° C after supplying the CuO powder, optimum joint strength and thermal properties can be achieved.

[Table 2]

In the case where Ag powder was used in place of the Cu powder in the metal paste, it was found that when compared with Comparative Example 2 in which the Ag paste was printed on the aluminum nitride substrate without supplying the CuO powder and performing the oxidation heat treatment, Inventive Examples 5 through 8 show significantly better joint strength and TCT results.

In particular, in the above Table 2, it was found that the connection strength of Examples 5 to 8 in the first tensile test was improved by 2 to 5 times when compared with Comparative Example 2, and when compared with Comparative Example 2 When compared, the joint strength of Examples 5 to 8 in the fifth tensile test was similar or increased by about 4 times.

Further, in the case of TCT, it was found that Comparative Example 2 produced delamination at the 300th cycle, and Examples 5 to 8 produced delamination at the 1,000th or 2,000th cycle. Accordingly, when compared with Comparative Example 2, Examples 5 to 8 showed an improvement in thermal properties of 6 times or more.

In addition, tensile tests and TCT results were found to vary significantly depending on the temperature of the oxidative heat treatment.

In particular, it was found that when compared with Example 5 and Example 8 in which the oxidative heat treatment was carried out at 1,000 ° C to 1,200 ° C, wherein the oxidative heat treatment was carried out at 1,100 to 1,150 ° C after supplying CuO powder 6 and Example 7 When the tensile test was performed, the joint strength was increased by about 2 times, and when TCT was measured, two or more times of delamination occurred.

Accordingly, it was found that although Ag paste was used, if the oxidative heat treatment was carried out at 1,100 to 1,150 ° C after supplying CuO powder, optimum joint strength and thermal properties were achieved. That is, if the Ag paste is supplied, the Cu position of CuAl ₂ O ₄ contained in the connection layer is replaced by Ag to form an AgAl ₂ O ₄ structure to form a strong connection with the Ag paste.

100‧‧‧ceramic circuit board

101‧‧‧Aluminum nitride substrate

102‧‧‧Connection layer

103‧‧‧metal layer

204‧‧‧Metal film

A1, a2, b1, b2‧‧‧ steps

Fig. 1 is a conceptual diagram showing a cross-sectional view of a ceramic circuit board according to an embodiment of the present invention. Fig. 2 is a flow chart showing a method of manufacturing a ceramic circuit board according to an embodiment of the present invention. Fig. 3 is a view showing the connection strength test of the ceramic circuit board of the present invention.

Claims (10)

A ceramic circuit board comprising: an aluminum nitride substrate; a connection layer formed on the aluminum nitride substrate, the connection layer comprising a metal oxide having a spinel structure; and a metal layer formed on the connection layer Wherein at least one of the connection layer and the metal layer comprises a glass frit. The ceramic circuit board of claim 1, wherein the metal oxide of the spinel structure comprises CuAl ₂ O ₄ . The scope of the patent application to item 1 of the ceramic circuit board, wherein the connecting layer comprises the spinel structure and the glass frit CuAl ₂ O _4, and CuAl ₂ O ₄ weight ratio of the glass frit-based 1: 2.53 to 4.18. The ceramic circuit board of claim 1, wherein the metal layer comprises a metal powder having Cu, Ag, or a mixture thereof and the glass frit, and the weight ratio of the metal powder to the glass frit is 1:0.05 to 0.1. The ceramic circuit board of claim 1, wherein the connection layer has a thickness in the range of 10 to 1,000 nm, and the metal layer has a thickness in the range of 3 to 300 μm. A method of manufacturing a ceramic circuit board, comprising: supplying a CuO powder on an aluminum nitride substrate, and performing an oxidative heat treatment to form a connection layer of CuAl ₂ O ₄ including a spinel structure; and printing a metal paste (metal Paste) is sintered on the spinel structure of CuAl ₂ O ₄ to form a metal layer. The method of producing a ceramic circuit board according to claim 6, wherein the metal paste comprises 80 to 90 wt% of metal powder, and 10 to 20 wt% of a mixture of glass frit and a binder. The method of producing a ceramic circuit board according to claim 6, wherein the CuO powder has an average particle diameter of 1 to 50 μm. The method of producing a ceramic circuit board according to claim 6, wherein the CuO powder is supplied in an amount of 5 x 10 ^-3 mg to 10 x 10 ^-3 mg per 1 cm ² . The method of producing a ceramic circuit board according to claim 6, wherein the temperature of the oxidative heat treatment is from 1,000 ° C to 1,200 ° C.