JP2000049427A - Joined body and circuit board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable silicon nitride circuit board and to mass- produce it. SOLUTION: This joined body is formed by joining a silicon nitride substrate provided with a division groove for which the thickness of the silicon nitride substrate at a division groove bottom part is 0.2-0.5 mm and a metal plate. Also, this circuit board is manufactured by using the joined body. In this case, it is desirable that the silicon nitride substrate is composed of the sintered compact of a green molding to which the division groove is executed and also, it is desirable that the silicon nitride substrate is the one to which the division groove is mode by laser working to a silicon nitride sintered compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength and high-reliability circuit board comprising a silicon nitride substrate on which a metal circuit or a metal circuit and a metal radiator plate are formed, and a joined body suitable for manufacturing the same. And for mass production of circuit boards. The circuit board of the present invention is suitable for assembling a power module or the like of electronic components.

[0002]

2. Description of the Related Art Due to the miniaturization, multifunctionality, and diversification of electronic devices, the application range of power modules and the like has been widened.
Usage in harsh conditions is also increasing. Along with this,
High reliability has been required for high thermal conductive insulating circuit boards for power modules. In order to respond to this, a circuit board including a silicon nitride substrate having high strength and high thermal conductivity as a component has been developed and put into practical use.

A circuit board having a silicon nitride substrate as a component is formed by bonding a metal plate to a silicon nitride substrate by an active metal brazing method, a direct bonding method, or the like, and etching the metal plate to form a metal circuit having a predetermined pattern. It is manufactured by. There is also a structure in which a metal radiator plate is formed on the opposite surface on which a metal circuit is formed.

[0004]

As a result, it has become possible to manufacture a silicon nitride circuit board having a predetermined pattern of metal circuits. However, since the above method is manufactured by bonding and etching a metal plate for each silicon nitride substrate, there is a problem in mass production. Therefore, a copper-alumina circuit board, such as a multi-piece method, which is in practical use, that is, a copper plate is bonded to an alumina substrate having a dividing groove, and a copper circuit having a predetermined pattern is formed by etching the copper plate.
Next, even if the technology of dividing along the dividing groove is adopted as it is, the silicon nitride substrate has higher strength and toughness than the alumina substrate, so there is a part that is displaced from the dividing groove and can be mass-produced. It was difficult.

[0005] The present invention has been made in view of the above, and an object of the present invention is to mass-produce silicon nitride circuit boards, which conventionally could only be manufactured individually.

[0006]

That is, the present invention provides the following. (1) A bonded body comprising: a silicon nitride substrate having a dividing groove having a thickness of 0.2 to 0.5 mm at the bottom of the dividing groove; and a metal plate. (2) The silicon nitride substrate is made of a sintered body of a green compact having a dividing groove.
The conjugate of the above. (Claim 3) The joined body according to claim 1, wherein the silicon nitride substrate is obtained by subjecting a silicon nitride sintered body to division grooves by laser processing. (4) The joined body according to (1), (2) or (3), wherein a solder resist pattern is formed on a surface of the metal plate or a plated surface of the plated metal plate. (5) A circuit board according to the above (1), (2) or (3), wherein the metal plate of the joined body is formed of a metal circuit having a predetermined pattern and is divided along a dividing groove. (6) A circuit board according to the above (4), wherein the metal plate of the joined body is made of a metal circuit having a predetermined pattern and is divided along a dividing groove.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail. The silicon nitride substrate used in the present invention has a three-point bending strength of 500 MPa or more in order to meet the reliability for higher mechanical strength. And the IF method (JIS R
It is preferable that the material has a toughness having a fracture toughness value of 5.5 MPam ^1/2 or more according to 1607) and a thermal conductivity of 6 MPa or more.
It is preferable to have high thermal conductivity of 0 W / mK or more. The thickness of the silicon nitride substrate is generally about 0.5 to 1.0 mm.

Such a silicon nitride substrate is formed by molding a mixture containing silicon nitride powder, a sintering aid such as alumina, magnesia, and yttria and a binder into a green molded body, followed by degreasing and sintering. It can be manufactured by forming a sintered body and processing it. The surface properties of the silicon nitride substrate are important, and fine defects and dents have a large effect on the contact area when joining with the metal plate, so it is desirable that the surface be smooth, and it should be polished by honing or machining. It is desirable that processing has been performed.

In the present invention, in order to obtain a silicon nitride substrate provided with a dividing groove, a dividing groove having a predetermined size is formed in a green compact in consideration of shrinkage during sintering, and then degreased and sintered. A method is employed in which a dividing groove having a predetermined size is directly formed on a silicon nitride sintered body by laser processing or high water pressure processing. According to the former, the process is simplified and further mass production is possible.Also, according to the latter, there is an advantage that division with more precise dimensional accuracy is possible. Selected.

The shape of the dividing groove formed on the silicon nitride substrate is arbitrary, but usually the surface width is about 100 μm and the sectional shape is V-shaped or concave. In the present invention, the thickness of the silicon nitride substrate at the bottom of the dividing groove is important,
0.2 to 0.5 mm. Thereby, it becomes possible to divide without any trouble along the division groove. That is,
If the thickness of the bottom of the division groove is larger than 0.5 mm, the division may be performed with the division groove deviated, resulting in a defective product that cannot be incorporated into a predetermined module. If the thickness of the bottom of the dividing groove is less than 0.2 mm, the method of forming the dividing groove in the green compact may crack the silicon nitride substrate during degreasing and sintering. In the method of forming grooves directly, cracks may be generated from the dividing grooves during the operation, or when the brazing material is applied to the entire front and back surfaces of the silicon nitride substrate, It becomes difficult to remove the brazing material component that has entered.

In the present invention, the dividing groove may be formed on one surface of the silicon nitride substrate, or may be formed on both front and back surfaces. When the dividing groove is formed only on one surface of the silicon nitride substrate, either a metal circuit or a heat-dissipating metal plate is formed on that surface, but it is desirable to form a metal circuit.

The metal plate used in the present invention includes copper,
At least one kind of metal plate selected from metals such as nickel, aluminum and molybdenum, a laminated plate made of two or more kinds of the above metals, or an alloy plate made of two or more kinds of the above metals, which are bonded to a silicon nitride substrate. In this case, the structure usually takes a laminated structure or an alloy structure. The thickness of the metal circuit is preferably about 0.3 to 0.5 mm, and the thickness of the metal on the heat dissipation side is preferably about 0.1 to 0.3 mm.

[0013] The joined body of the present invention has the above-mentioned divided groove.
Brazing filler metal on a silicon nitride substrate and / or on the metal plate
After applying the strike on the entire surface or in a predetermined pattern,
The metal plate is made of silicon nitride based
It can be manufactured by placing it on a plate and heat treating it.
Wear. In the joined body of the present invention, the metal plate is made of silicon nitride.
Even if the structure is bonded only to one side of the substrate
Good, and at least a structure joined to both sides
You may. The heat treatment for bonding is 1 × 10 vacuum ^-Five~ 1 ×
10^-6Torr high vacuum, temperature around 800-840 ° C
Done in

The metal component of the brazing material paste used here is mainly composed of an Ag component and a Cu component, and an active metal is a secondary component in order to ensure wettability with the silicon nitride substrate during melting. The active metal component reacts with the silicon nitride substrate to form oxides and nitrides, and these products strengthen the bond between the brazing material and the silicon nitride substrate. Specific examples of the active metal include Ti, Zr, Hf, Nb,
Ta, V and these compounds. The weight ratio of these was 1 to 80 parts of Ag and 20 to 5 parts of Cu.
1 to 7 parts of active metal per 00 parts.

The brazing material paste can be prepared by adding an organic solvent and, if necessary, an organic binder to the metal component of the brazing material, and mixing the resulting mixture with a roll, a kneader, a universal mixer, a grinder, or the like. . Examples of the organic solvent include methylcellosolve, terpineol, isophorone, and toluene, and examples of the organic binder include ethylcellulose, methylcellulose, and polymethacrylate.

In a structure in which an etching resist of a predetermined metal circuit pattern is applied on the metal plate of the joined body thus obtained, and a heat-dissipating metal plate is formed on the opposite surface of the metal circuit, An etching resist having a predetermined heat radiation metal plate pattern is also applied on the metal plate on the opposite surface. Thereafter, the metal is dissolved with an etching solution such as a ferric chloride solution or a cupric chloride solution, and by removing the metal portion on the dividing groove, further, hydrochloric acid, sulfuric acid, hydrogen peroxide, a halogenated fluorine compound, etc. By removing the unnecessary bonding layer that causes a short circuit with the brazing material removal liquid,
A substrate having a plurality of circuit boards partitioned by the dividing grooves is manufactured. When a small external force such as bending is applied to this board, a single circuit board is cut along the dividing groove, and a plurality of circuit boards are manufactured.

In the present invention, the metal circuit and / or the metal radiator plate of the substrate before being cut into a single circuit substrate can be plated with nickel, gold, or the like. Further, a pattern of a solder resist is printed on the surface of the metal circuit and / or the metal heat radiating plate on which the plating is applied or not, and the solder resist is cured by ultraviolet light, heating, or the like, and a predetermined solder resist pattern is formed. Can also be formed. With these measures, the number of process steps is reduced, and further mass production becomes possible.

In particular, by forming a solder resist pattern on a substrate before division, the strength characteristics are remarkably improved as compared with a conventional method in which a slit is provided in a metal circuit to prevent a solder flow. In addition, since the formation of the solder resist pattern requires a lot of labor, the labor can be significantly reduced as compared with a case where the solder resist pattern is formed on a single circuit board.

The solder resist has an effect of preventing the flow of solder to a position other than a predetermined position when soldering a semiconductor chip, an electrode terminal, and the like, and a displacement of a mounting position of the semiconductor chip and the like due to the flow. Therefore, it is desirable that the solder resist used in the present invention is applied so as to surround the periphery of the chip mounting position with a thickness of about 1.0 mm according to the shape and size of the semiconductor chip and the like.

[0020]

The present invention will be described more specifically with reference to examples and comparative examples.

Example 1 Magnesia and yttria as sintering aids were respectively added to silicon nitride powder at 3% and 5%, respectively, and methyl cellulose and water were added as binders to prepare a slurry. After forming this into a sheet, it is cut into a predetermined size to form a green molded body, degreased in air at 500 ° C., and then sintered at 1850 ° C. for 4 hours in a nitrogen atmosphere to obtain 60 × 30 × 0.635 mm silicon nitride sintered body (thermal conductivity 68 W / m · K, three-point bending strength 650 M
Pa or more, fracture toughness by IF method 5.7 MPa
m ^1/2 ). On one side of this silicon nitride sintered body,
Four division grooves having a V-shaped cross section, a surface width of 95 μm, and a silicon nitride substrate thickness of 0.4 mm at the bottom of the division grooves were applied by a YAG laser.

On the surface of the silicon nitride substrate on which the dividing grooves have been formed, a brazing material paste (metal component: Ag 80%, Cu 15%, Ti 5%) is applied in a pattern avoiding the dividing grooves, and divided into sections. For the part, make the pattern rate 20%,
A copper plate having a thickness of 0.3 mm is arranged, and a brazing material paste is applied to the entire back surface on which no dividing grooves are formed, and then a solid copper plate having a thickness of 0.15 mm is arranged.
They were joined by heat treatment at ℃.

Next, in order to form a heat-dissipating copper plate by etching the solid copper plate on the back surface, an etching resist is applied at a distance of 1 mm from a virtual dividing line on the back surface corresponding to the dividing groove, and an etching solution comprising a ferric chloride solution is applied. Etching was performed with a brazing filler metal removal solution composed of a mixed solution of aqueous hydrogen peroxide and ammonium fluoride to remove unnecessary copper plate portions and unnecessary brazing filler metal (joining layer) portions. By this operation,
Four circuit boards were divided by the dividing grooves, and a copper circuit having a pattern ratio of 20% was formed in each of the divided portions, and a substrate having a heat-dissipating copper plate on the opposite surface was manufactured.

Next, N is applied to each copper circuit and heat dissipation copper plate.
After the i-plating, a force was manually applied along the dividing groove, and the division was performed along the dividing groove, and four circuit boards were manufactured. The obtained circuit board was good without cracks or the like.

Example 2 The thickness of the silicon nitride substrate at the bottom of the dividing groove was 0.3 mm.
When a circuit board was manufactured in the same manner as in Example 1 except that the above conditions were adopted, good results almost equivalent to those in Example 1 were obtained.

Example 3 A split groove was formed in a green molded body using a cutter provided in a mold, and a silicon nitride substrate obtained by degreasing and sintering the green molded body was used. A circuit board was manufactured in the same manner as in Example 2. As a result, almost the same good results as in Example 1 were obtained.

Example 4 A circuit board was manufactured in the same manner as in Example 2 except that the brazing material paste was applied to the silicon nitride substrate without avoiding the dividing grooves. As a result, it was possible to manufacture a circuit board from which unnecessary brazing material components that entered the division grooves were easily removed by the etching process. In addition, the division performance of the substrate, cracking of the circuit substrate after the division, and the like were almost the same as those in Example 1.

Example 5 The thickness of the silicon nitride substrate at the bottom of the dividing groove was 0.4 mm,
In addition, a circuit board was manufactured in the same manner as in Example 4 except that a solder resist was applied in a predetermined pattern on a Ni-plated copper circuit before being divided, and then cured with ultraviolet light to form a solder resist pattern. did. As a result, the removability of the unnecessary brazing material that had entered the dividing groove, the dividing property of the board, the cracking of the circuit board, and the like were almost as good as those of Example 4.

Example 6 A circuit board was manufactured in the same manner as in Example 4 except that a silicon nitride substrate having a thickness of 1.0 mm was used and the thickness of the silicon nitride substrate at the bottom of the dividing groove was set to 0.4 mm. As a result, the removability of the unnecessary brazing material that had entered the dividing groove, the dividing property of the board, the cracking of the circuit board, and the like were almost as good as those of Example 4.

Comparative Example 1 The thickness of the silicon nitride substrate at the bottom of the dividing groove was 0.6 mm.
A circuit board was manufactured in the same manner as in Example 1, except that As a result, there was a portion that was deviated from the dividing groove.

Comparative Example 2 The thickness of the silicon nitride substrate at the bottom of the division groove was 0.1 mm.
A circuit board was manufactured in the same manner as in Example 3 except that the above conditions were satisfied. As a result, the silicon nitride substrate cracked from the dividing groove during degreasing.

Comparative Example 3 The thickness of the silicon nitride substrate at the bottom of the division groove was 0.1 mm.
A circuit board was manufactured in the same manner as in Example 4 except for the above. As a result, after the etching, the brazing filler metal remained in the divided grooves, and the etching process was required again.

Comparative Example 4 A circuit board was manufactured in the same manner as in Example 4 except that a silicon nitride substrate having a thickness of 1.5 mm was used and the thickness of the silicon nitride substrate at the bottom of the dividing groove was set to 0.6 mm. As a result, it was broken off from the dividing groove at the time of dividing.

[0034]

According to the present invention, mass production of a highly reliable silicon nitride circuit board has become possible.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshihiko Tsujimura, Inventor 1 Shinkaicho, Omuta-shi, Fukuoka Denki Kagaku Kogyo Co., Ltd. Inside the Omuta Plant F-term in Omuta Factory (reference) 4G026 AA06 AB08 AC01 AD05 AF01 AG01 5E338 AA01 AA18 BB19 BB28 BB47 BB63 BB71 BB75 CC01 CC04 CD11 EE02 EE32 EE33

Claims (6)

[Claims] 1. A joined body comprising a silicon nitride substrate having a dividing groove having a thickness of 0.2 to 0.5 mm at the bottom of the dividing groove and a metal plate. 2. The joined body according to claim 1, wherein the silicon nitride substrate is formed of a green compact sintered body having a divided groove. 3. The joined body according to claim 1, wherein the silicon nitride substrate is formed by dividing a silicon nitride sintered body by laser processing. 4. The joined body according to claim 1, wherein a solder resist pattern is formed on a surface of the metal plate or a plated surface of the plated metal plate. 5. The circuit board according to claim 1, wherein the metal plate of the joined body is formed of a metal circuit having a predetermined pattern and is divided along a dividing groove. 6. The circuit board according to claim 4, wherein the metal plate of the joined body is made of a metal circuit having a predetermined pattern and is divided along a dividing groove.