KR102030688B1 - Ceramic circuit board and method of manufacturing the same - Google Patents

Abstract

The present invention is an aluminum nitride substrate; A bonding layer comprising a metal oxide having a spinel structure formed on the aluminum nitride substrate; And a metal layer formed on the bonding layer, wherein the bonding layer, the metal layer, or both are related to a ceramic circuit board including glass frit and a method of manufacturing the same.

Description

CERAMIC CIRCUIT BOARD AND METHOD OF MANUFACTURING THE SAME

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

Ceramic has high heat resistance, high mechanical strength and high insulation resistance, so that a high voltage is applied or a high output semiconductor device substrate is used. Such ceramic materials include alumina (Al ₂ O ₃ ), aluminum nitride (AlN), zirconia (ZrO ₂ ), silicon carbide (SiC) and silicon nitride (Si ₃ N ₄ ). Therefore, it is used in automobiles, high-speed rail, industrial parts and the like. Double aluminum nitride is excellent in thermal conductivity of 150-250W / mK it can be useful as a substrate for mounting a semiconductor device that emits a lot of heat during operation.

In order to use aluminum nitride as a circuit board, the electrode layer is formed by heating aluminum nitride to form an alumina film on the surface and heating and bonding copper metal plate thereon, which includes TiAgCu metal powder. There is an AMB (Active Metal Bonding) method of printing a brazing paste and heating and bonding copper metal thereon, and a metallizing method of forming an electrode layer by printing / firing a metal powder paste such as tungsten, molybdenum, copper, or the like.

Among them, as a metallizing method, for example, Japanese Unexamined Patent Application Publication No. Hei 5-320943 includes a specific content of Al ₂ O ₃ , SiO ₂ , WO or the like, thereby excellent bonding of an aluminum nitride substrate and a tungsten metal layer. A method of implementing strength and heat resistance is disclosed. However, the patent is not applicable to metals other than tungsten, there may be a limit to the use range.

Further, Japanese Unexamined Patent Application Publication No. 50-75208 discloses a specific portion so as to form an Al ₂ O ₃ on the surface by heating the aluminum nitride to increase the adhesion strength in forming the tungsten or molybdenum metal layer on metallizing aluminum nitride substrate Al ₂ O ₃ A method of improving the bonding strength while forming a spinel structure with Mn-Ti in a paste is disclosed. However, the method, despite the use of expensive pastes, is limited in achieving satisfactory bond strength.

Therefore, there is a need to develop a ceramic circuit board capable of satisfying the excellent bonding strength and thermal characteristics of the aluminum nitride substrate and the metal layer.

Japanese Patent Laid-Open No. 5-320943 Japanese Laid-Open Patent Publication No. 50-75208

The present invention provides a ceramic circuit board having high bonding strength and thermal characteristics between a metal layer and an aluminum nitride substrate in manufacturing a ceramic circuit board for semiconductor device mounting.

The present invention provides a method of manufacturing a ceramic circuit board which can reduce the manufacturing cost while achieving the above effects.

The present invention is an aluminum nitride substrate; A bonding layer comprising a metal oxide having a spinel structure formed on the aluminum nitride substrate; And a metal layer formed on the bonding layer, wherein the bonding layer, the metal layer, or both, provide a ceramic circuit board including glass powder.

In addition, the present invention is to form a spinel structure CuAl ₂ O ₄ by applying CuO powder on the aluminum nitride substrate and oxidized heat treatment; And printing a metal paste on CuAl ₂ O ₄ of the spinel structure and firing to form a metal layer.

The ceramic circuit board of the present invention comprises a bonding layer comprising a metal oxide having a spinel structure on an aluminum nitride substrate and a metal layer on the bonding layer, wherein the bonding layer and the metal layer comprise glass powder, thereby forming a spinel structure of the bonding layer. Due to the combination of the glass powder and the paste component of the metal layer, strong bonding strength between the metal layer and the aluminum nitride substrate can be realized, and the thermal characteristics can be further improved. In addition, it is possible to reduce the manufacturing cost of the ceramic circuit board while achieving such excellent physical properties.

1 is a conceptual diagram showing a cross section of a ceramic circuit board according to an embodiment of the present invention.
2 is a process flowchart illustrating a method of manufacturing a ceramic circuit board according to an embodiment of the present invention.
3 is a view showing a bonding strength test of the ceramic circuit board of the present invention.

Hereinafter, the present invention will be described in more detail to aid in understanding the present invention.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

1. Ceramic Circuit Board

As shown in FIG. 1, a ceramic circuit board (AlN) 100 according to an embodiment of the present invention is formed on an aluminum nitride substrate 101 and the aluminum nitride substrate 101 and includes a spinel structured metal oxide. The bonding layer 102 and the metal layer 103 formed on the bonding layer 102, the bonding layer 102, the metal layer 103 or both may include a glass powder (glass frit) have.

The aluminum nitride substrate 101 has excellent thermal conductivity and good electrical insulation, and may be an optimal material for mounting a semiconductor device emitting a large amount of heat during operation.

According to an embodiment of the present invention, the bonding layer 102 including the spinel structured metal oxide may include CuAl ₂ O ₄ , and the bonding layer 102 may have a thickness in the range of 10 to 1,000 nm. And may range from 10 to 400 nm, and may range from 50 to 200 nm. If the thickness of the bonding layer is less than the above range, the formation area of the metal oxide of the spinel structure is narrow, so that it may be difficult to implement the desired excellent bonding strength of the present invention, and if it exceeds the above range, it is partially bubbled after printing May be generated.

CuAl ₂ O ₄ of the spinel structure can be formed by applying a CuO powder onto the aluminum nitride substrate and heat-treated oxidation.

In addition, the metal layer 103 may include a metal powder including Cu, Ag, or a mixture thereof, the thickness may be in the range of 3 to 300 ㎛, may be in the range of 5 to 200 ㎛, 10 to 100 May be in the μm range.

In the ceramic circuit board according to an embodiment of the present invention, the bonding layer, the metal layer or both may include a glass powder.

In general, in the case of an aluminum nitride substrate, there is a problem in that the glass phase is insufficient and the bonding strength with the metal layer is low. The ceramic circuit board of the present invention comprises a bonding layer comprising a metal oxide having a spinel structure on an aluminum nitride substrate and a metal layer on the bonding layer, wherein the bonding layer and the metal layer comprise glass powder, thereby forming a spinel structure of the bonding layer. Due to the bonding between the glass powder and the paste component of the metal layer, strong bonding strength between the metal layer and the aluminum nitride substrate can be realized. In addition, since the thermal characteristics such as TCT (Thermal Cycle Test) physical properties can be further improved, the metal layer is not separated from the ceramic circuit board even after repeated application by applying a current for a long time, thereby improving reliability.

2. Manufacturing Method of Ceramic Circuit Board

A detailed description of each of the elements constituting the ceramic circuit board according to an embodiment of the present invention will be described below with reference to the following manufacturing process.

Method of manufacturing a ceramic circuit board according to an embodiment of the present invention is to form a CuAl ₂ O ₄ of the spinel structure by applying CuO powder on the aluminum nitride substrate and oxidized heat treatment (step (a)); And printing a metal paste on CuAl ₂ O ₄ of the spinel structure and baking to form a metal layer (step (b)).

2 is a process flowchart illustrating a method of manufacturing a ceramic circuit board according to an embodiment of the present invention.

Referring to Figure 2 in detail, in the method of manufacturing a ceramic circuit board according to an embodiment of the present invention, the step (a) is coated with a CuO powder on an aluminum nitride substrate (a1), by oxidizing heat treatment (a2) ) May be a step of forming CuAl ₂ O ₄ having a spinel structure.

The CuO powder applied on the aluminum nitride substrate may have an average particle diameter of 10 to 400 μm, specifically, an average particle diameter of 1 to 50 μm, 3 to 40 μm, and 5 to 20 μm. . The CuO powder per aluminum nitride substrate 1㎠ 5X10 ^{- 3} mg to 10X10 ^- may be applied in an amount of ³ mg. If the amount of CuO powder is less than the above range, the amount of CuO powder to be applied is too small, the amount of CuAl ₂ O ₄ formed may be too small, on the contrary, if the amount of CuO powder exceeds the above range partially bubble after printing There may be a problem that occurs.

The oxidative heat treatment may be performed for about 10 to 30 minutes in the temperature range of 1000 ℃ to 1200 ℃, more specifically in the temperature range of 1100 ℃ to 1150 ℃. The oxidation heat treatment process can be carried out, for example, in a box furnace. According to one embodiment of the present invention, the optimum bonding strength and thermal characteristics can be realized within the oxidation heat treatment temperature range, particularly within the temperature range of 1100 ° C to 1150 ° C.

By the oxidizing heat treatment, a CuAl ₂ O ₄ having a spinel structure can be formed on the aluminum nitride substrate, and the formation mechanism of CuAl ₂ O ₄ is shown in Schemes 1 and 2 below.

Scheme 1

AlN + O ₂ Al ₂ O ₃ + NO _x

Wherein x is 0-2.

Scheme 2

CuO + Al ₂ O ₃ CuAl ₂ O ₄

Specifically, after the CuO powder is applied on the aluminum nitride substrate, by the oxidizing heat treatment process, aluminum nitride may be oxidized on the surface of the aluminum nitride substrate to form Al ₂ O ₃ (Scheme 1). In addition, the formed Al ₂ O ₃ may react with the coated CuO to form a CuAl ₂ O ₄ having a spinel structure (Scheme 2).

If the oxidizing heat treatment time is too short, the reaction may not be performed. If the oxidizing heat treatment time is too long, when Al ₂ O ₃ film is formed on the aluminum nitride surface, Al and O may not be contacted to grow the Al ₂ O ₃ film. The speed can be lowered.

In addition, when the oxidation heat treatment temperature is less than the temperature range, the oxidation reaction may not be performed, and when the oxidation heat treatment temperature is exceeded, the Al ₂ O ₃ film may be thickened to decrease adhesion to the oxide layer having a weak affinity with AlN.

In the method of manufacturing a ceramic circuit board according to an embodiment of the present invention, step (b) is performed by printing a metal paste on CuAl ₂ O _{4 having} the spinel structure (b1) and baking the same as shown in FIG. 2. (b2) forming the metal layer.

The metal paste may include 80 to 90 wt% of a metal powder including Cu, Ag or a mixture thereof, and 10 to 20 wt% of a mixture of a glass powder and a binder.

The binder may be an organic binder that is commonly used. Examples of the binder may include polyvinyl alcohol (PVA), polyvinyl butyral (PVB), ethyl cellulose, and acrylic resin. In addition, the glass powder may include a calcium silicate-based glass powder having an average particle diameter of 1.5 to 10.5 ㎛. The metal paste including the metal powder, the binder, and the glass powder can be used by purchasing a commercially available product from Heraeus, Tanaka, and others.

The metal paste printing method may be printed by, for example, screen printing or jet injection (b1), and after printing, for example, about 1 minute to 30 minutes at 100 to 150 ° C. May dry.

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

According to one embodiment of the present invention, the CuAl ₂ O ₄ of the spinel structure by the firing can be strongly bonded to the metal powder and glass powder contained in the metal paste. Further, the glass powder can penetrate into the structure of CuAl ₂ O ₄ spinel structure, and may be formed of a strong bond by this penetration.

Accordingly, the bonding layer including CuAl ₂ O ₄ having a spinel structure on the ceramic circuit board may also include glass powder. According to an embodiment of the present invention, the weight ratio of CuAl ₂ O ₄ to glass powder of the spinel structure may be 1: 2.53 to 4.18.

In addition, after the strong bonding by the firing, the weight ratio of the metal powder to the glass powder included in the metal layer may be 1: 0.05 to 0.1.

According to another embodiment of the present invention, when the metal powder included in the metal paste is Ag, that is, when the Ag paste is used, Ag is replaced by Cu sites in CuAl ₂ O ₄ formed in the bonding layer by firing. While forming the structure of AgAl ₂ O ₄ , strong bonding with the Ag paste can be made. Therefore, according to an embodiment of the present invention, the bonding layer may include not only glass powder included in the metal paste, but also metal powder.

The bonding strength test method of the ceramic circuit board manufactured by the above method may use a pull test method as illustrated in FIG. 3.

In the bonding strength test method, as shown in FIG. 3, a solder is melted at 300 ° C. on a ceramic specimen 200 in which an aluminum nitride substrate 201, a bonding layer 202, and a metal layer 203 are combined. It is a method of measuring the bonding strength by melting and attaching a Cu wire (metal foil, 204) matched with a Cu plating pattern and pulling it with the UTM equipment in the direction of the arrow shown in FIG. 3.

Furthermore, the thermal cycle test (TCT) performance of the ceramic circuit board obtained according to the embodiment of the present invention can be measured, and the TCT is specifically, for example, at a temperature of -55 ° C to 150 ° C. It can be obtained by checking how many cycles delamination appears by continuously rotating the cycle in units of 100, 300, 500, 1000, 1500 and 2000 cycles. The peeling phenomenon can be confirmed, for example, by scanning acoustic microscopy.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are only for illustrating the present invention, and the present invention is not limited by these examples.

Example

Example  One

It was applied in an amount of ³ mg, and the oxidation heat treatment for about 45 minutes in a box furnace (furnace) of about 1000 ℃ ^- a CuO powder having an average particle diameter of 5㎛ on the aluminum nitride (AlN) substrate per 7.5X10 aluminum nitride substrate 1㎠ A spinel structure CuAl ₂ O ₄ was formed on an aluminum nitride (AlN) substrate.

A copper paste (Tanaka Co., Ltd.) containing about 85 wt% of Cu powder, and about 15 wt% of glass powder and ethyl cellulose was screen printed on the CuAl ₂ O _{4 having} the spinel structure. After the printing and dried for about 10 minutes at about 100 to 150 ℃, and then fired for about 30 minutes at about 900 to 1000 ℃ under a nitrogen atmosphere, it was repeatedly laminated three times to form a metal layer to prepare a specimen.

Example  2

A specimen was prepared in the same manner as in Example 1, except that the oxidation heat treatment temperature was performed at 1100 ° C.

Example  3

A specimen was prepared in the same manner as in Example 1 except that the oxidation heat treatment temperature was performed at 1150 ° C.

Example  4

A specimen was prepared in the same manner as in Example 1, except that the oxidation heat treatment temperature was performed at 1200 ° C.

Example  5

The specimen was prepared in the same manner as in Example 1 except that the oxidation heat treatment temperature was performed at 1000 ° C. and Ag powder was used instead of the Cu powder.

Example  6

The specimen was prepared in the same manner as in Example 1, except that the oxidation heat treatment temperature was performed at 1100 ° C., and Ag powder was used instead of the Cu powder.

Example  7

The specimen was prepared in the same manner as in Example 1, except that the oxidation heat treatment temperature was performed at 1150 ° C., and Ag powder was used instead of the Cu powder.

Example  8

The specimen was prepared in the same manner as in Example 1 except that the oxidation heat treatment temperature was performed at 1200 ° C., and Ag powder was used instead of the Cu powder.

Comparative example  One

A metal paste containing 85% by weight of Cu powder and 15% by weight of ethyl cellulose as a glass powder and a binder was screen printed onto an aluminum nitride (AlN) substrate. After the printing and dried for about 10 minutes at about 100 to 150 ℃, and then fired for about 30 minutes at about 900 to 1000 ℃ under a nitrogen atmosphere, it was repeatedly laminated three times to form a metal layer to prepare a specimen.

Comparative example  2

A specimen was prepared in the same manner as in Comparative Example 1, except that Ag powder was used instead of the Cu powder.

Experimental Example  1: joint strength evaluation

Bond strength was evaluated by the pull test method.

Specifically, as shown in Figure 3, after using the solder on the specimens (5x5 mm SQ size) obtained in Examples 1 to 8, and Comparative Examples 1 and 2, the metal foil was attached to the direction of the arrow shown in Figure 3 UTM equipment The bond strength was measured by pulling.

Experimental Example  2: TCT  evaluation

Thermal Cycle Test (TCT) evaluation is performed on a thermal shock test in 500 units of 100, 300, 500, 1000, 1500 and 2000 cycles at temperatures ranging from -55 ° C to 150 ° C. The number of cycles (degrees of occurrence) of delamination of the metal was confirmed by scanning acoustic microscopy.

Tables 1 and 2 below are evaluation results for Experimental Examples 1 and 2, and Examples 1 to 4 and Comparative Example 1, which were screen printed using Cu paste, are screen printed using Ag paste in Table 1 below. 5 to 8 and Comparative Example 2 are shown in Table 2 below.

Property evaluation Example 1 Example 2 Example 3 Example 4 Comparative Example 1 CuO Powder
Application O O O O X Oxidation Heat Treatment Temperature (℃) 1000 1100 1150 1200 X join
burglar
(N / mm) 1 time 5.1 9.6 12.7 3.8 2.3 Episode 2 6.5 10.5 10.0 4.6 1.2 3rd time 5.6 10.8 9.5 4.4 1.6 4 times 5.2 11.9 12.0 3.3 2.1 5th 5.9 9.8 10.8 3.7 1.9 TCT
(Number of peelings occurred) 1,000 cycle 2,000 cycle 2,000 cycle 1,000 cycle 300 cycle

As can be seen in Table 1, after the CuO powder coated and oxidized heat treatment on the aluminum nitride substrate to form CuAl ₂ O ₄ of the spinel structure on the aluminum nitride substrate, Example 1 to the present invention of printing Cu paste 4 shows that the bonding strength and the TCT results are remarkably superior to those of Comparative Example 1 in which the Cu paste is printed on the aluminum nitride substrate without performing coating and oxidizing heat treatment.

Specifically, in Examples 1 to 4 in Table 1, the bonding strength was improved by 1.5 to 5 times in the first full test compared to Comparative Example 1, and Examples 1 to 4 in the full test 5 times were compared to Comparative Example 1. It can be seen that it is improved by about 2 to 5 times.

In addition, in the case of TCT, Comparative Example 1 showed a peeling phenomenon in the 300th cycle, but in Examples 1 to 4, it can be seen that the peeling phenomenon occurred in the 1000th or 2000th cycle. Accordingly, it can be seen that Examples 1 to 4 have improved thermal characteristics by up to 6 times or more compared to Comparative Example 1.

On the other hand, it can be seen that the results of the full test and TCT are significantly different depending on the oxidation heat treatment temperature.

Specifically, Examples 2 and 3 in which the oxidative heat treatment was performed at 1100 ° C. and 1150 ° C. after the application of CuO powder were bonded in the full test compared to Examples 1 and 4 where the oxidative heat treatment was performed at 1000 ° C. and 1200 ° C. It can be seen that the strength is improved by about 2 to 3 times, and when TCT is measured, the peeling phenomenon occurs more than 2 times slowly.

Therefore, it can be seen that, after the CuO powder coating, the oxidative heat treatment is performed at 1100 ° C. and 1150 ° C., optimum bonding strength and thermal properties can be achieved.

Property evaluation Example 5 Example 6 Example 7 Example 8 Comparative Example 2 CuO Powder
Application O O O O X Oxidation Heat Treatment Temperature (℃) 1000 1100 1150 1200 X join
burglar
(N / mm) 1 time 5.96 8.9 12.10 4.58 2.34 Episode 2 6.29 11.7 11.70 4.17 2.45 3rd time 6.15 12.2 13.82 3.45 1.76 4 times 7.21 13.1 12.34 3.89 3.56 5th 6.22 9.1 13.38 3.07 3.73 TCT
(Number of peelings occurred) 1,000 cycle 2,000 cycle 2,000 cycle 1,000 cycle 300 cycle

Even when a metal paste was used instead of Cu powder, Examples 5 to 8 of the present invention were bonded to Comparative Example 2 in which the Ag paste was printed on the aluminum nitride substrate without performing the coating and oxidizing heat treatment of the CuO powder. The strength and TCT results are remarkably excellent.

Specifically, in Examples 2 to 8 in Table 2, the bonding strength was improved by about 2 to 5 times in the first full test compared to Comparative Example 2, and Examples 5 to 8 in the full test 5 times were compared to Comparative Example 2. It is similar to or improved by about 4 times.

In addition, in the case of TCT, Comparative Example 2 showed a peeling phenomenon at 300 cycles, but in Examples 5 to 8, peeling phenomenon occurred at 1000 or 2000 cycles. Therefore, Examples 5 to 8 it can be seen that the thermal properties improved up to 6 times or more compared to Comparative Example 2.

In addition, it can be seen that the results of the full test and TCT are significantly different depending on the oxidation heat treatment temperature.

Specifically, Examples 6 and 7 in which the oxidative heat treatment was performed at 1100 ° C. and 1150 ° C. after the application of CuO powder were bonded in the full test compared to Examples 5 and 8 in which the oxidative heat treatment was performed at 1000 ° C. and 1200 ° C. It can be seen that the strength is improved by about 2 times, and when the TCT measurement, the peeling phenomenon occurs more than twice as slowly.

Therefore, even when the Ag paste is used, it can be seen that the optimum bonding strength and thermal properties can be achieved when the oxidative heat treatment is performed at 1100 ° C. and 1150 ° C. after the application of the CuO powder. That is, when the Ag paste is applied, it can be seen that Ag is substituted at the Cu site of CuAl ₂ O ₄ included in the bonding layer to form an AgAl ₂ O ₄ structure, and thus strong bonding is performed with the Ag paste.

100: ceramic circuit board
101, 201: Aluminum nitride substrate (AlN)
102, 202: bonding layer
103,203: metal layer
200: ceramic specimen
204: metal foil

Claims (10)

Aluminum nitride substrates;
A bonding layer comprising CuAl ₂ O ₄ having a spinel structure formed by applying CuO powder on the aluminum nitride substrate and subjecting it to oxidative heat treatment at 1,000 to 1,200 ° C .; And
A metal layer formed on the bonding layer;
At least one of the bonding layer and the metal layer is a ceramic circuit board (glass frit) is included.
delete The method according to claim 1,
The weight ratio of CuAl ₂ O ₄ to the glass powder of the spinel structure is 1: 2.53 to 4.18 ceramic circuit board.
The method according to claim 1,
Wherein said metal layer comprises a metal powder comprising Cu or Ag and a glass powder, wherein the weight ratio of said metal powder to glass powder is from 1: 0.05 to 0.1.
The method according to claim 1,
The thickness of the bonding layer is in the range of 10 to 1000 nm, the thickness of the metal layer is in the range of 3 to 300 ㎛ ceramic circuit board.
Coating CuO powder on an aluminum nitride substrate and oxidizing heat treatment at 1,000 to 1,200 ° C. to form CuAl ₂ O ₄ having a spinel structure; And
And forming a metal layer by printing and firing a metal paste on the CuAl ₂ O _{4 having} the spinel structure.
The method according to claim 6,
The metal paste is 80 to 90% by weight of the metal powder, and 10 to 20% by weight of the mixture of the glass powder and the binder.
The method according to claim 6,
The CuO powder is a method of manufacturing a ceramic circuit board having an average particle diameter of 1 to 50 ㎛.
The method according to claim 6,
The coating amount of the CuO powder per 5X10 1㎠ ^{- 3} mg to 10X10 ^{- 3} mg The method of manufacturing a ceramic circuit board to.
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