JP3166573B2 - Ceramic wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic wiring board provided with a conductive circuit on the surface of a ceramic substrate used as an electronic component.

[0002]

2. Description of the Related Art As electronic components have become smaller and lighter, the width and spacing between conductor circuits of a ceramic wiring board have been reduced. Accordingly, ceramic wiring boards are required to have high adhesion of conductor circuits and good migration resistance. The term "migration" refers to a phenomenon in which metal ions generated under high temperature and high humidity are deposited on a cathode side at a high electric field between narrow pitches, extend in a branch shape to an anode side, and short-circuit between conductor circuits.

In order to prevent such migration, resin sealing is generally performed so that the conductor is not exposed to a high humidity environment. However, the sealing resin has a large coefficient of thermal expansion, and depending on the use environment, may generate an excessive stress on a connection portion between the conductor circuit and the ceramic substrate, and may break the conductor circuit. Therefore, a method other than the resin sealing method for improving the migration resistance is required.

Further, as the pitch between conductor circuits of a printed wiring board is reduced and the width of a conductor circuit is reduced, it is becoming difficult to visually inspect printed wiring boards for disconnection, short circuit, and the like. Therefore, recently, it has been increasing that the contrast of the brightness of the surface of the printed wiring board is converted into a binary signal and the circuit inspection is performed by an image recognition device.
In order to perform a circuit inspection with high accuracy by this method, it is necessary that a difference in reflectance between a circuit portion and a non-circuit portion is large when light of an arbitrary wavelength is applied. In the case of a substrate having a surface color other than white, such as a glass base epoxy resin substrate, the difference in the reflectance between the circuit portion and the non-circuit portion is large, so that the circuit inspection can be performed without any trouble by the image recognition device. However, in the case of a ceramic wiring board that uses a ceramic substrate with a white color on the surface, the reflection level between the circuit part and the white substrate surface, which is the non-circuit part, is close, and the brightness contrast can be accurately determined. There is a problem that it is difficult to convert the signal into a binary signal, and thus it is difficult to perform a circuit inspection using an image recognition device.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a first problem to be solved by the present invention is that a conductor circuit has a strong adhesive force, An object of the present invention is to provide a ceramic wiring board having good migration resistance.

Further, a second object of the present invention is to solve the first object, and to perform an accurate circuit inspection by an image recognition device using the principle of binary signal conversion.
An object of the present invention is to provide a ceramic wiring board using a white ceramic substrate.

[0007]

According to a first aspect of the present invention, there is provided a ceramic wiring board wherein a copper metallization layer formed on a surface of a ceramic substrate via a base metal layer is etched to form a conductive circuit. In the plate, the base metal layer has a temperature equal to or higher than a temperature at which a reaction product of the ceramic component of the ceramic substrate and the metal component of the base metal layer is generated,
A heat treatment in an oxidizing atmosphere at a temperature of 100 ° C. or less to generate the reaction product, and then perform a reduction treatment by immersion in a reducing solution; In addition, the reaction product is exposed between the conductor circuits by the etching.

According to a second aspect of the present invention, there is provided the ceramic wiring board according to the first aspect, wherein a heat treatment temperature in an oxidizing atmosphere is 850 to 1100 ° C.

According to a third aspect of the present invention, there is provided the ceramic wiring board according to the first aspect, wherein the base metal layer also contains bismuth and the heat treatment temperature in an oxidizing atmosphere is from 600 to 600. The temperature is 1100 ° C.

A ceramic wiring board according to a fourth aspect of the present invention is the ceramic wiring board according to the third aspect, wherein the base metal layer also contains magnesium.

According to a fifth aspect of the present invention, there is provided a ceramic wiring board according to any one of the first to fourth aspects, wherein the ceramic substrate is a white ceramic substrate.

[0012]

Embodiments of the present invention will be described below.

Examples of the ceramic component constituting the ceramic substrate in the present invention include oxides such as alumina, zirconia and barium titanate, and nitrides such as aluminum nitride and silicon nitride, and are not particularly limited.

In the present invention, a copper metallization layer formed on a surface of a ceramic substrate via a base metal layer is etched to form a conductor circuit. The base metal layer may be a metal layer containing copper, and can be formed by, for example, an electroless plating method, a sputtering method, a metal paste method, an organic metal resinate (or a paste thereof) method, or the like. The thickness of the base metal layer is not particularly limited,
It is desirable that the thickness be in the range of 0.05 to 3 μm in order to obtain a conductor circuit having high adhesion.

The base metal layer is heat-treated in an oxidizing atmosphere so that a reaction product between the ceramic component of the ceramic substrate and the metal component of the base metal layer is generated. The heat treatment temperature is equal to or higher than a temperature at which a reaction product of the ceramic component of the ceramic substrate and the metal component of the base metal layer is generated,
It is a temperature of 1100 ° C. or less. The condition that the temperature is higher than the temperature at which the reaction product is generated varies depending on the metal component of the base metal layer.
It is preferable to carry out at a temperature of not less than ° C. If the temperature is lower than these temperatures, the reaction product may not be generated. Further, at a temperature exceeding 1100 ° C., the scattering of the metal component during the heat treatment becomes remarkable, and the amount of the metal component contributing to the improvement of the adhesion of the conductor circuit cannot be secured. Therefore, the adhesion of the conductor circuit becomes insufficient. Heat treatment is performed at a temperature of 1100 ° C. or less.

After the reaction product of the ceramic component and the metal component is generated on the surface of the ceramic substrate in this manner, the underlying metal layer is subjected to a reduction treatment by immersion in a reducing solution. By this reduction treatment, the copper oxide present on the surface of the underlying metal layer is reduced to metallic copper. The reducing solution may be any as long as it can reduce copper oxide, and for example, a borohydride solution, a hypophosphite solution, a dimethylamine borane solution, or the like can be used.

In the present invention, a reduction treatment is performed as described above, and a copper metallized layer is formed on a base metal layer having metallic copper on the surface. Since this reduction treatment is performed using a reducing solution, the adhesion between the underlying metal layer and the copper metallized layer is stronger than when the reduction treatment is performed at a high temperature using a reducing gas. . The method for forming the copper metallized layer is not particularly limited, but may be an electroless plating method, an electrolytic plating method, a sputtering method, or the like.
It is preferable to carry out the method in such a manner that the content of impurities is small and a desired thickness can be easily obtained.

Furthermore, in the present invention, the copper metallized layer is etched to form a conductor circuit, and the etching exposes the reaction product of the ceramic component and the metal component between the conductor circuits. The surface where the reaction product is exposed has poor wettability to water, has an effect of delaying elution of metal ions due to migration, and improves the migration resistance. The surface exposing the reaction product has a unique color,
If the color of the surface of the ceramic substrate is white, the surface of the ceramic substrate will be colored, so it is possible to perform accurate circuit inspection using an image recognition device using the principle of binary signal conversion Ceramic wiring board. Also,
Since the metal component that has not reacted with the ceramic component of the base metal layer is removed by etching, insulation between the conductor circuits is ensured.

In the present invention, the base metal layer preferably contains bismuth together with copper. The reason is that, as described above, a reaction product of the ceramic component and the metal component can be obtained even when the heat treatment temperature is as low as 600 ° C. to 850 ° C. In order to obtain such a favorable effect, when the metal component of the base metal layer is two elements of copper and bismuth, the copper content is 15 to 95% by weight based on the total amount of the metal components in the base metal, Bismuth content is 5-8
When the metal component of the base metal layer is three elements of copper, bismuth and magnesium, the content of copper with respect to the total amount of the metal components in the base metal is preferably 15 to 5% by weight. 95% by weight, bismuth content 4.
It is preferable that the content is 9 to 80% by weight and magnesium is in the range of 0.1 to 5% by weight. It is preferable that magnesium is also contained in the base metal layer containing copper and bismuth, since the adhesion of the conductor circuit is further improved.

The conductor circuit of the ceramic wiring board of the present invention further comprises nickel on the copper metallized layer.
A layer of a metal other than copper such as gold may be formed.

[0021]

The present invention will be described below based on examples and comparative examples.

(Examples 1 to 6) Various ceramic substrates composed of the ceramic components shown in Table 1 were prepared.
After palladium nucleation was performed on the surface of each substrate to make it sensitive, electroless copper plating was performed on the entire surface of the substrate to form a copper layer having a thickness of 0.5 μm. Next, heat treatment was performed in the air at 1000 ° C. for 1 hour. Next, an aqueous solution of sodium borohydride having a pH of 12.5 is heated to about 80 ° C., and the substrate that has been subjected to the above heat treatment is immersed therein, and the copper oxide layer on the substrate surface is reduced to form metallic copper. A ceramic substrate on which a metal layer was formed was obtained. Then, the entire surface of the ceramic substrate with the base metal layer having been subjected to the reduction treatment is again subjected to electroless copper plating (formation of a copper metallized layer) to have a total film thickness of about 10 μm.
m of the copper conductor layer was formed. Next, a circuit for migration test, a circuit for measuring adhesion, and a conductor circuit including a comb pattern for examining the suitability of the image recognition device were formed by a subtractive method, and a ceramic wiring board was obtained.
In this ceramic wiring board, a reaction product of a ceramic component and copper constituting the ceramic substrate is exposed on the surface of the ceramic substrate between the conductor circuits. In Examples 1 to 4 using a white substrate, The space between the conductor circuits was colored brown.

Next, a migration test, a measurement of adhesion and a test for adaptability to an image recognition apparatus were performed by the following methods, and the results are shown in Table 1. Note that this test was not performed on a barium titanate and silicon carbide substrate that is not a white substrate, since there is no problem with the adaptability of the image recognition apparatus.

(Method of Migration Test) As a circuit for migration test, two strip-shaped conductor circuits (electrodes 2 and 2 in FIG. 1) arranged in parallel with a gap of 1 mm are formed. Then, as shown in FIG.
m, two electrodes 2 and 2 facing each other with a gap 1
During this time, a DC voltage of 10 V is applied by the DC power supply 4. Next, distilled water is dropped into the gap 1 to cause a short circuit between the electrodes 2 and 2. An ammeter 3 is connected between the electrodes 2 and 2 in advance, and the time from when the distilled water is dropped until the current value reaches 10 mA is measured to evaluate the migration resistance.

(Measurement Method of Adhesion Force) As a circuit for measuring adhesion force, a conductor is etched to form an adhesion force measurement circuit 12 of 2 mm square. Then, as shown in FIG. 2, a tin-plated copper wire 1 having a diameter of 0.7 mm
After fixing 4 using solder 13, tin-plated copper wire 14 is pulled using a tensile tester, and the adhesion between ceramic substrate 11 and adhesion measurement circuit 12 is measured. In addition, the arrow in FIG. 2 shows the tensile direction of the tensile test.

(Testing Method for Adaptability of Image Recognition Apparatus) Conductor circuit width 100 μm, circuit interval 1 by subtractive method
An image recognition device using the principle of binarization (Dai Nippon Screen Manufacturing Co., Ltd.) The test was performed using an optical appearance inspection system (PI-5400, manufactured by Co., Ltd.), and the adaptability of the image recognition apparatus was examined based on whether or not the test result was a non-defective product. At the same time, the state of coloring between the conductor circuits is tested using a Z-II optical sensor manufactured by Nippon Denshoku Industries Co., Ltd. That is, tristimulus values in the XYZ system were measured, and C
According to the formula of the IE1976 (L ^* a ^* b ^* ) color space specification, L
The display value in the ^* a ^* b ^* color system is calculated, and this L ^* a ^* b
Check the coloring from ^* .

[0027]

[Table 1]

(Comparative Examples 1 to 6) Various ceramic substrates composed of the ceramic components shown in Table 2 were prepared.
After subjecting each substrate to a surface roughening treatment immersed in hot phosphoric acid, the substrate surface was sensitized by palladium nucleation. After sensitization, electroless copper plating was applied to the entire surface of the substrate to form a copper layer having a thickness of about 10 μm. Then, in the same manner as in Example 1, a circuit for migration test, a circuit for adhesion measurement, and a conductor circuit including a comb pattern for examining the applicability of the image recognition device were formed by a subtractive method, and a ceramic wiring board was formed. Obtained. In this ceramic wiring board, on the surface of the ceramic substrate between the conductor circuits,
The reaction product of the ceramic component and copper constituting the ceramic substrate was not present.

Next, in the same manner as in Example 1, a migration test, a measurement of adhesion and a test for adaptability to an image recognition apparatus were performed, and the results are shown in Table 2. Note that this test was not performed on a barium titanate and silicon carbide substrate that is not a white substrate, since there is no problem with the adaptability of the image recognition apparatus.

The results of Comparative Examples 1 to 6 show that a ceramic wiring board manufactured by a method of roughening a ceramic substrate has excellent adhesion of a conductor circuit, but uses migration resistance and a white substrate. In this case, it was confirmed that the adaptability of the image recognition apparatus was poor.

[0031]

[Table 2]

(Examples 7 to 12) Various ceramic substrates composed of the ceramic components shown in Table 3 were prepared, palladium nuclei were applied to the surfaces of the substrates, and sensitization was performed. Copper plating was performed to form a copper layer having a thickness of 0.5 μm. Then, bismuth resinate paste (manufactured by NE Chemcat, H95C-
1, a bismuth content of 15% by weight) is applied to the entire surface of the substrate on which electroless copper plating is performed by a screen printing method.
After drying at 25 ° C for 10 minutes, 850 ° C for 1 hour,
Heat treatment was performed in the air. Next, an aqueous solution of sodium borohydride having a pH of 12.5 is heated to about 80 ° C., and the substrate that has been subjected to the above heat treatment is immersed therein, and the copper oxide layer on the substrate surface is reduced to form metallic copper. A ceramic substrate on which a metal layer was formed was obtained. Then, a copper metallized layer was formed on the entire surface of the ceramic substrate with the base metal layer after the reduction treatment by an electrolytic copper plating method. The thickness of the copper metallization layer was formed such that the total thickness including the thickness of the underlying metal layer was about 10 μm. Next, in the same manner as in Example 1, a circuit for migration test was obtained by a subtractive method,
A ceramic circuit board was obtained by forming a circuit for measuring the adhesion and a conductor circuit including a comb pattern for examining the adaptability of the image recognition apparatus.

Next, in the same manner as in Example 1, a migration test, a measurement of adhesion, and a test for adaptability to an image recognition apparatus were performed. The results are shown in Table 3. Note that this test was not performed on a barium titanate and silicon carbide substrate that is not a white substrate, since there is no problem with the adaptability of the image recognition apparatus.

[0034]

[Table 3]

(Examples 13 to 15) Various ceramic substrates composed of the ceramic components shown in Table 4 were prepared, palladium nuclei were applied to the surfaces of the respective substrates, and sensitization was performed. Copper plating was performed to form a copper layer having a thickness of 0.5 μm. Then, bismuth resinate paste (manufactured by NE Chemcat, H95C-
1.3 parts by weight of 1, bismuth content 15% by weight) and 0.5 part by weight of magnesium resinate paste (Z95C-3, manufactured by NE Chemcat Corporation, magnesium content 1.3% by weight) were mixed. The bismuth-magnesium mixed resinate paste prepared in the above was applied to the entire surface of the substrate on which electroless copper plating was performed by screen printing, and
After drying at 25 ° C for 10 minutes, 850 ° C for 1 hour,
Heat treatment was performed in the air. Next, an aqueous solution of sodium borohydride having a pH of 12.5 is heated to about 80 ° C., and the substrate that has been subjected to the above heat treatment is immersed therein, and the copper oxide layer on the substrate surface is reduced to form metallic copper. A ceramic substrate on which a metal layer was formed was obtained. Then, a copper metallized layer was formed on the entire surface of the ceramic substrate provided with the base metal layer after the reduction treatment by a sputtering method. The thickness of the copper metallization layer was formed such that the total thickness including the thickness of the underlying metal layer was about 10 μm. Then, in the same manner as in Example 1,
A circuit for migration test, a circuit for measuring adhesion, and a conductor circuit including a comb pattern for examining the applicability of the image recognition device were formed by a subtractive method to obtain a ceramic wiring board.

Next, in the same manner as in Example 1, a migration test, a measurement of adhesion, and a test for adaptability to an image recognition device were performed. The results are shown in Table 4.

[0037]

[Table 4]

(Example 16, Comparative Example 7, Comparative Example 8) 96
% Ceramic substrate was obtained in the same manner as in Example 2 except that a heat treatment in the atmosphere was performed at the temperature shown in Table 5 using a% alumina substrate and a migration test, adhesion measurement, and image recognition device adaptation. Table 5
It was shown to. Table 5 also shows the results of Example 2. In Comparative Example 7, since the heat treatment temperature in the air was 600 ° C., no reaction product was generated between the ceramic component and the metal component of the base metal layer, and the obtained evaluation result was not good. In Comparative Example 8, the heat treatment temperature in the atmosphere was 120
The temperature was as high as 0 ° C., and the scattering of metal components during the heat treatment became remarkable, and the amount of metal components contributing to the improvement of the adhesion of the conductor circuit could not be secured. Therefore, the adhesion of the conductor circuit was insufficient.

[0039]

[Table 5]

(Examples 17, 18 and Comparative Examples 9 and 10) The same procedures as those of Example 8 were carried out except that a 96% alumina substrate was used and the heat treatment in the air was performed at the temperature shown in Table 5. Similarly, a ceramic wiring board was obtained, and a migration test, a measurement of adhesion, and a test for adaptability to an image recognition device were performed. The results are shown in Table 6. Table 6 also shows the results of Example 8. In Comparative Example 9, since the heat treatment temperature in the air was 400 ° C., no reaction product was generated between the ceramic component and the metal component of the base metal layer, and the obtained evaluation result was not good. Further, in Comparative Example 10, the heat treatment temperature in the atmosphere was as high as 1200 ° C., and the scattering of the metal component during the heat treatment became remarkable, and the amount of the metal component contributing to the improvement of the adhesion of the conductor circuit could not be secured. The power was insufficient.

[0041]

[Table 6]

[0042]

According to the ceramic wiring board of the present invention, the base metal layer has a temperature not lower than a temperature at which a reaction product of the ceramic component of the ceramic substrate and the metal component of the base metal layer is generated. A heat treatment in an oxidizing atmosphere at a temperature of not more than 0 ° C. to generate the reaction product, and then perform a reduction treatment by immersion in a reducing solution, a copper-containing base metal layer, In addition, since the reaction product is exposed between the conductor circuits by etching, the ceramic circuit board has a favorable performance that the adhesion of the conductor circuits is strong and the migration resistance is good.

The ceramic wiring board according to the fifth aspect of the present invention achieves the above-mentioned effects, and can accurately perform a circuit inspection by an image recognition device using the principle of binary signal conversion. And a ceramic wiring board using a white ceramic substrate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a measurement method of a migration test.

FIG. 2 is a cross-sectional view showing a method for measuring the adhesion between a ceramic substrate and a conductor circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gap 2 Electrode 3 Ammeter 4 DC power supply 11 Ceramic substrate 12 Adhesion measurement circuit 13 Solder 14 Tin-plated copper wire

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-150091 (JP, A) JP-A-3-136293 (JP, A) JP-A-5-54713 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H05K 1/09 H05K 3/38 H05K 3/06

Claims (5)

(57) [Claims] 1. A ceramic wiring board in which a conductor circuit is formed by etching a copper metallized layer formed on a surface of a ceramic substrate via a base metal layer, wherein the base metal layer comprises a ceramic component of the ceramic substrate and a base. Above the temperature at which the reaction product of the metal layer with the metal component is generated, 110
A heat treatment in an oxidizing atmosphere at a temperature of 0 ° C. or less to generate the reaction product, and then perform a reduction treatment by immersion in a reducing solution; The ceramic wiring board, wherein the reaction product is exposed between the conductor circuits by the etching. 2. The heat treatment temperature in an oxidizing atmosphere is 850.
The ceramic wiring board according to claim 1, wherein the temperature is from 1 to 1100C. 3. The base metal layer also contains bismuth, and the heat treatment temperature in an oxidizing atmosphere is 600 to 1
The ceramic wiring board according to claim 1, wherein the temperature is 100 ° C. 4. The ceramic wiring board according to claim 3, wherein the base metal layer also contains magnesium. 5. The ceramic wiring board according to claim 1, wherein the ceramic substrate is a white ceramic substrate.