JP3209936B2 - Circuit board and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for a high heat-generating electronic component or a hybrid integrated circuit in which a high heat-generating electronic component and a control circuit electronic component are mounted, has high heat dissipation, and is excellent in electric reliability. The present invention relates to a circuit board for a hybrid integrated circuit and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a circuit board for a hybrid integrated circuit on which electronic components having high heat generation are mounted, a metal base circuit board using a metal plate having good heat conductivity is known. The metal base circuit board is provided on a metal plate such as aluminum with an insulating agent filled with an inorganic filler in epoxy resin or the like to about tens of μm,
It has a structure in which a circuit made of a conductive foil is provided on the insulating layer. Since this metal-based circuit board has high thermal conductivity, it is preferably used as a circuit board for high-power applications, such as power supply components, on which electronic components generating a large amount of heat are mounted. As the metal-based circuit board, a circuit board having a conductor circuit formed using a copper foil having a thickness of, for example, 300 μm has been developed so that a larger current can flow through the circuit.

[0003]

However, a metal base circuit board for a large current, which is a conductor circuit using this thick copper foil, has low adhesion reliability between the conductive foil and the insulating layer. In particular, the adhesion reliability is poor after heat treatment or after humidification, and there has been a problem that it cannot be used reliably over a long period under actual use conditions.

[0004]

According to the present invention, there is provided a circuit board having a conductor circuit provided on at least one principal surface of a metal plate via an insulating layer, wherein at least the surface of the conductor circuit on the metal plate side is made of copper. A plating layer, a circuit board characterized by being in contact with the insulating layer via a copper oxide film sequentially, preferably, the copper plating layer is at least one of nickel and cobalt is the circuit board, The content of nickel and cobalt is 0.1 to 15% by weight, the thickness of the copper plating layer is 0.5 to 20 μm, and the roughness of the copper plating layer is 0.1 μm or more and 10 μm or less in Rz. The circuit board described above. Also, if the thickness of the conductor circuit is 20
The circuit board having a thickness of 0 to 1000 μm. Further, in the above circuit board, the thickness of the oxide film is not less than 10 nm and not more than 200 nm.

The present invention also relates to a method of manufacturing a circuit board for bonding a metal foil on at least one main surface of a metal plate via an insulating adhesive layer to form a conductor circuit from the metal foil, wherein at least one surface of the circuit board is formed. By forming a copper plating layer and subjecting a copper oxide film layer formed on the surface of the copper plating layer to an acid treatment, the metal foil with the adjusted thickness of the copper oxide film is processed in the order of the copper plating layer and the oxide film.
A method for manufacturing a circuit board, characterized in that the circuit board is used so as to be in contact with an insulating layer , preferably, a copper plating layer is formed by an electroless copper plating method, and an oxide film is formed by a heat treatment. This is a method for manufacturing a circuit board in which the thickness of a film is adjusted by an acid treatment. Further, preferably, the temperature of the heat treatment is 80 to 200 ° C., and the acid treatment is performed using sulfuric acid, particularly sulfuric acid having a concentration of 2 to 15% by weight, and the thickness of the adjusted oxide film is 10 nm or more and 200 nm or less. There is provided a method of manufacturing the circuit board.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows an example of a circuit board according to the present invention. A conductive circuit 3 is mounted on a metal plate 1 via an insulating layer 2, and a copper plating layer 4 and an oxide layer 5 are formed on a side of the conductive circuit 3 that contacts the insulating layer 2. An electronic component 6 such as a semiconductor element is mounted on the upper surface of the conductor circuit 3 via a solder 7, and the electronic component 6 is electrically connected to the conductor circuit 3 by a wire 8 such as gold or aluminum. The present invention is not limited to the circuit board illustrated in FIG. 1, and may be a circuit in which another conductor circuit is laminated on the conductor circuit 3 via another insulating layer, A structure similar to that of the upper surface of FIG. 1 may be provided on the rear surface of the metal plate.

The inventor of the present invention has conducted various studies in order to solve the above-mentioned problems. As a result, the surface of the conductor circuit 3 on the side in contact with the insulating layer 2 has a copper plating layer 4 and the copper plating layer 4 It has been experimentally found that a circuit board having extremely excellent adhesion reliability can be obtained when the oxide film 5 exists on the surface of the present invention, and the present invention has been achieved. The reason for this is not clear, but the copper plating layer 4 has a moderately uneven surface, exhibits a so-called anchor effect, increases the adhesive force between the conductor circuit 3 and the insulating layer 2, and has an oxide film 5 on the surface. It is presumed that the formation of the insulating layer further enhances the affinity with the insulating layer 2 and thus achieves high bonding reliability.

As a method for obtaining a copper plating layer, electrolytic copper plating and electroless copper plating are known. In the present invention, any method may be used, but copper having various shapes and various surface roughness may be used. An electroless copper plating method is preferable because a plating layer can be easily obtained. In particular, the electroless copper plating layer containing either nickel or cobalt has a needle-like surface shape and is excellent in bonding with the insulating layer.
Also, by adding a predetermined amount of a salt of nickel or cobalt to the electrolytic solution, an electroless copper plating layer containing either nickel or cobalt can be easily obtained,
preferable.

Further, the electroless copper plating layer in which the content of nickel and cobalt is 0.1% by weight to 15% by weight,
The surface roughness is in the range of 0.1 μm or more and 10 μm or less in Rz, and is very rich in adhesion to the insulating layer 2 and excellent. That is, if the surface roughness of the surface of the conductor circuit 3 that contacts the insulating layer 2 is less than 0.1 μm, the adhesive force is insufficient and the conductor circuit 3 peels off when mounting electronic components. When the thickness exceeds 10 μm, electric field concentration occurs at the convex portion on the surface, and the electrical reliability of the circuit board may be reduced.

The thickness of the copper plating layer 4 formed on the conductor circuit 3 is preferably 0.5 μm or more and 20 μm or less, and more preferably 1 μm to 15 μm. When the thickness is less than 0.5 μm, the adhesive strength may not be obtained, and when the thickness exceeds 20 μm, the copper plating layer 4 tends to cause cohesive failure, and as a result, the adhesive strength may be reduced.

However, as described above, even if the copper plating layer 4 is provided, the adhesion reliability after heat treatment or humidification of the circuit board may be reduced. The inventor further studied this point and found that the copper plating layer 4 and the insulating layer 2
Are improved when they are brought into contact with each other through the oxide film 5, and the present invention has been achieved. That is, the oxide film 5
Is formed on the copper plating layer 4 by, for example, performing a heat treatment under a condition of maintaining the same at 80 to 200 ° C. for a predetermined time in the air. It has been found that the adhesive strength with the insulating layer 2 does not decrease.

As described above, the oxide film 5 can be obtained, for example, by exposing the copper plating layer 4 to a temperature of 80 to 200 ° C. in the air, and by adjusting the temperature and the holding time thereof. 5 can be formed with a desired thickness. Regarding the heat treatment temperature in the air, it is possible to select a temperature other than the above-mentioned temperature range. Not only takes a long time, but also tends to cause unevenness in the oxide film. If the temperature exceeds 200 ° C., the oxide film grows too quickly to control the thickness. 200 ° C. is selected as a preferred range. The thickness of the oxide film 5 is determined by preparing a cross section with a diamond cutter or the like and performing EDAX analysis on the cross section to check the thickness of a portion where an oxygen component is confirmed.

In the present invention, the thickness of the oxide film 5 is 10 n
It is preferably from m to 200 nm. Oxide film 5 is 10 nm
If it is less than 7, the adhesive strength may be insufficient, causing problems such as peeling of the conductor circuit in a moisture resistance test or the like. If it exceeds 200 nm, cohesive failure of the oxide film 5 may occur, and the bonding reliability may decrease. .

The thickness of the oxide film 5 can be controlled by treating the surface of the metal foil for the conductive circuit 3 with an acid before electroless copper plating and before bonding the insulating film to the insulating layer. The type of acid used in the acid treatment is not particularly limited, and sulfuric acid, phosphoric acid, hydrochloric acid, a mixture thereof, a sulfuric acid-hydrogen peroxide aqueous solution, or the like can be used. Of these, sulfuric acid is preferred because it can remove the oxide film 5 quickly and relatively uniformly, and particularly, 2% by weight or more and 1% or more.
Sulfuric acid at a concentration of 5% by weight or less is preferred. That is, when the sulfuric acid concentration is less than 2% by weight, it takes time to reduce the oxide film to a predetermined thickness and the workability deteriorates, so that it is not suitable for industrial production, and the sulfuric acid concentration exceeds 15% by weight. In such a case, the thickness of the oxide film obtained may be uneven due to the difference in the contact time between the sulfuric acid and the copper plating layer.

Although the material of the conductor circuit 3 is not particularly limited, a material made of at least one of copper, aluminum, iron, molybdenum, nickel, cobalt, and silicon is selected. It does not matter.

The thickness of the conductor circuit 3 is preferably 200 μm or more and 1000 μm or less. The thickness of the conductor circuit 3 is 20
Although there is no problem if it is smaller than 0 μm, there is a case where there is no merit in making a circuit board for a large current application.
On the other hand, when the thickness of the conductor circuit 3 exceeds 1000 μm, when a circuit is manufactured by an etching method, the mounting density is reduced due to the influence of an etching factor, and the circuit may not be practically used as a circuit board.

In the present invention, aluminum and its alloys, copper, iron, stainless steel, clad materials of these metals or alloys, etc. are used for the metal plate 1, but the metal plate 1 is not limited to these. The thickness of the metal plate 1 is not particularly limited, but is generally 0.5 mm or more.
Those having a size of 0 mm or less are used.

For the insulating layer 2, a resin filled with an inorganic filler is mainly used. As the resin, epoxy resin, phenol resin, and
Butyral resin and the like are used, and as the inorganic filler, aluminum oxide, silicon oxide, magnesium oxide, aluminum nitride, silicon nitride, boron nitride and the like are used. In addition, glass fibers, glass cloth, inorganic fibers, and the like may be mixed with the inorganic filler.

The thickness of the insulating layer 2 is 50 μm or more and 200 μm.
The following is preferred. If the thickness of the insulating layer 2 is less than 50 μm, the insulation reliability of the circuit board may be reduced.
If it exceeds 0 μm, insulation reliability is ensured, but thermal conductivity is reduced, and it may be impossible to mount an electronic device or a semiconductor element having a high calorific value.

As a method of obtaining the circuit board of the present invention, a copper plating layer 4 is formed on at least one side of a metal foil to be a conductor circuit 3 and then the copper plating layer 4 is heated by, for example, air. Is formed by oxidizing a part of the metal foil to form an oxide film 5, bonding the metal foil on the metal plate 1 via the insulating layer 2, and further processing the metal foil by a method such as etching to form a circuit. Can be. Further, when the thickness of the oxide film 5 is too large, it can be adjusted to a predetermined thickness by treating with an acid such as sulfuric acid before joining to the metal plate 1.

Hereinafter, the present invention will be described in more detail with reference to examples.

【Example】

Example 1 One side of a copper foil having a thickness of 0.3 mm was plated with electroless copper plating under the following conditions to form a copper plating layer having a thickness of 9.1 μm and a surface roughness Rz of 5 μm. next,
The treatment was performed in the air at 120 ° C. for 30 minutes to form an oxide film with a thickness of 50 nm on the surface of the copper plating layer. Next, an insulating agent is applied on a 3.0 mm-thick aluminum plate so as to have a cured thickness of 80 μm to form an insulating layer, and then the copper having a copper plating layer and an oxide film A foil was laminated on the insulating layer, an insulating agent was cured by a hot press method to prepare a metal base substrate, and further, a circuit was formed by etching the copper foil portion to obtain a metal base circuit board. . The metal base circuit board was subjected to a heat resistance test and a moisture resistance test under the following conditions, and the adhesive strength between the conductor circuit and the insulating layer before and after the test was examined by the following method. The results are shown in Table 1.

[0023]

[Table 1]

<Heat resistance test method> After forming a pattern for measuring the foil adhesion strength on the metal base circuit board,
After being floated on a solder bath at a constant temperature of 60 ° C. for 60 minutes, the metal base circuit board is taken out, and the foil bonding strength is examined.

<Moisture resistance test method> After forming a pattern for measuring the foil adhesion strength on a metal base circuit board,
After leaving in a pressure vessel of × 2.0atm for 100 hours,
The metal base circuit board is taken out and the adhesive strength of the foil is examined.

<Measurement Method of Adhesion Strength between Conductive Circuit and Insulating Layer> The peel strength test method described in 5.7 of JIS C6841 Test Method for Copper-Clad Laminates for Printed Wiring Boards is used.

<Method for Measuring Breakdown Voltage of Circuit Board>
IS C2110 The step breakdown test method described in Section 8.2 of the test method of the dielectric strength of the solid electrical insulating material is used.

[Examples 2 to 12, Comparative Examples 1 and 2] During the preparation of a metal base circuit board, various conditions of electroless copper plating were used to change the copper plating thickness, the copper plating composition, the surface roughness, and the concentration. Except for changing the oxide film thickness by changing the treatment time with 10% by weight sulfuric acid, various metal-based circuit boards obtained through the same operation as in Example 1
The same evaluation as in Example 1 was performed, and Examples 2 to 12 were performed. In addition, a metal-based circuit board using a copper foil with an oxide film on the surface by heat treatment in air without applying electroless copper plating. To make a metal-based circuit board using copper foil,
This is a comparative example. These results are also shown in Table 1. In addition, all the metal-based circuit boards including Example 1 had good dielectric strength of 10 kV or more, which was good.

[0029]

The circuit board of the present invention has excellent adhesion between the conductor circuit and the insulating layer, high adhesive strength, and excellent adhesive reliability.
Adhesion reliability is high even after heat treatment or humidification treatment in a quality control test, and it can be used reliably over a long period under actual use conditions. Further, according to the manufacturing method of the present invention, there is an effect that the circuit board can be stably and reliably obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a circuit board of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal plate 2 Insulating layer 3 Conductor circuit (metal foil) 4 Copper plating layer 5 Oxide film 6 Electronic component 7 Solder 8 Wire

Claims (15)

(57) [Claims] 1. A circuit board having a conductor circuit provided on at least one main surface of a metal plate via an insulating layer, wherein at least the surface of the conductor circuit on the metal plate side comprises a copper plating layer and an oxide film sequentially. A circuit board characterized by being in contact with an insulating layer via an insulating layer. 2. The circuit board according to claim 1, wherein the copper plating layer contains at least one of nickel and cobalt. 3. The circuit board according to claim 2, wherein the content of nickel and cobalt in the copper plating layer is 0.1% by weight or more and 15% by weight or less. 4. The copper plating layer has a thickness of 0.5 μm or more and 20 μm or more.
2. The circuit board according to claim 1, wherein m is equal to or less than m. 5. The circuit board according to claim 1, wherein the roughness of the copper plating layer is 0.1 μm or more and 10 μm or less in Rz. 6. The conductor circuit has a thickness of 200 μm or more and 1000 μm or more.
The circuit board according to claim 1, wherein the thickness is not more than μm. 7. The circuit board according to claim 1, wherein the thickness of the oxide film is not less than 10 nm and not more than 200 nm. 8. A method for manufacturing a circuit board, comprising joining a metal foil on at least one principal surface of a metal plate via an insulating layer to form a conductive circuit from the metal foil, wherein at least one surface of the metal foil is plated with copper. to form a layer, further by forming an oxide film on the copper plating layer surface, before the metal foil was adjusted thickness of the oxide film
In contact with the insulating layer via the copper plating layer and the oxide film in order
A method for producing a circuit board, characterized in that it is used as described above . 9. The method according to claim 8, wherein the copper plating layer is formed by an electroless copper plating method. 10. The method according to claim 8, wherein the oxide film is formed by a heat treatment. 11. The method for manufacturing a circuit board according to claim 10, wherein the heat treatment temperature is 80 ° C. or more and 200 ° C. or less. 12. The method according to claim 8, wherein the thickness of the oxide film is adjusted by performing an acid treatment. 13. The method for producing a circuit board according to claim 12, wherein the acid treatment is performed using sulfuric acid. 14. The method according to claim 11, wherein the concentration of the sulfuric acid is 2% by weight or more and 15% by weight or less. 15. The oxide film after adjustment has a thickness of 10 nm or more.
8. The structure according to claim 8, wherein the thickness is equal to or less than 00 nm.
15. A method for manufacturing a circuit board according to claim 14.