JP2003069201A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that peeling occurs between a wiring layer and a copper plated layer, or swelling is produced in the copper plated layer. SOLUTION: This wiring board is formed by adhering a wiring layer 2 in which electrodes of an electronic part 3 are connected to an insulation substrate 1 by means of a low-melting-point soldering material 5. A copper-boron plated layer 6 containing more than 0.3 wt.% boron, a copper plated layer 7, and a gold plated layer 8 are adhered in sequence to the surface of an area where at least the electrodes of the electronic part 3 in the wiring layer 2 are connected by means of the soldering material 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board used for a semiconductor element housing package for housing a semiconductor element, a hybrid integrated circuit board and the like.

[0002]

2. Description of the Related Art Conventionally, a wiring board used for a package for accommodating semiconductor elements, a hybrid integrated circuit board, or the like generally has an insulating base made of an electrically insulating material such as an aluminum oxide sintered body or an aluminum nitride sintered body. A wiring layer made of a metal material such as tungsten, molybdenum, manganese or the like deposited on the surface and inside of the insulating base, and on the surface of the insulating base, an electronic component such as a semiconductor element, a capacitive element, or a resistor. And each electrode of the electronic component is electrically connected to the wiring layer via a low melting point brazing material such as tin-lead solder.

Such a wiring board is mounted on the external electric circuit board by connecting a predetermined portion of the wiring layer to a wiring conductor of the external electric circuit board through a low melting point brazing material such as tin-lead solder, and at the same time, the wiring board. Each electrode of the electronic component mounted on the board is also electrically connected to a predetermined external electric circuit.

In addition, the wiring board usually has a copper plating layer and a gold plating layer sequentially deposited on the exposed surface of the wiring layer, and the copper plating layer lowers the electrical resistance of the wiring layer and lowers the wiring layer. The melting point brazing material is bonded well, and the gold plating layer effectively prevents oxidative corrosion of the wiring layer and the copper plating layer.

[0005]

However, in the above-mentioned conventional wiring board, the average grain size of the crystal grains of copper forming the copper plating layer is generally about 1 μm, and metals such as tungsten, molybdenum and manganese are included. It is larger than the uneven diameter (recess: approximately 1 μm) on the surface of the wiring layer made of a material. Therefore, even if a copper plating layer is deposited on the surface of the wiring layer, the copper plating layer does not sufficiently enter into the concave portion of the surface of the wiring layer, and many voids are formed between the wiring layer surface and the copper plating layer, As a result, the adhesion strength between the copper plating layer and the wiring layer is weakened, and the copper plating layer is easily separated from the wiring layer by the application of an external force, or enters into the void between the wiring layer surface and the copper plating layer. The gas has a drawback in that it greatly expands due to heat or the like when connecting an electrode of an electronic component to a wiring layer via a low melting point brazing material, and blister or the like is generated in the copper plating layer.

The present invention has been devised in view of the above-mentioned conventional drawbacks, and its purpose is to effectively prevent peeling between the wiring layer and the copper plating layer or blistering or the like in the copper plating layer. Then, by providing a copper plating layer and a gold plating layer firmly on the wiring layer, an electrode of an electronic component can be firmly attached and connected to the wiring layer via a low melting point brazing material. It is in.

[0007]

SUMMARY OF THE INVENTION The present invention is a wiring board in which an electrode of an electronic component is adhered and formed on an insulating substrate through a low melting point brazing material. At least 0.3% by weight of boron is contained on the surface of the region where the electrode of the electronic component is connected through the low melting point brazing material.
The above-mentioned copper-boron plating layer, copper plating layer, and gold plating layer are successively deposited.

Further, the present invention is characterized in that the thickness of the copper-boron plating layer is 0.03 μm or more.

Further, the present invention is characterized in that the average grain size of the copper crystal grains forming the copper-boron plating layer is 0.02 μm or less.

According to the wiring board of the present invention, at least the electrode of the electronic component is connected to the surface of the wiring layer through the low melting point brazing material, and the content of boron is 0.3% by weight or more. Even if there are many irregularities on the surface of the wiring layer because the copper-boron plating layer having a small crystal grain size of 0.3 μm or less is deposited, the copper-boron crystals are satisfactorily introduced into the depressions. The wiring layer and the copper-boro plating layer are firmly adhered to each other without forming a void between them, and the copper-boron plating layer has adhesion to both the copper-boron plating layer and the gold plating layer. Since the good copper plating layer is deposited, the copper plating layer and the gold plating layer can be firmly deposited on the wiring layer, and the electrical resistance of the wiring layer is made small by the copper plating layer. And the gold plating layer The electrode of the electronic component to the wiring layer while effectively prevent oxidation corrosion of the wiring layers securely via the low melting point brazing material, it is possible to firmly electrically connected.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an embodiment in which the wiring board of the present invention is applied to a package for accommodating semiconductor elements, 1 is an insulating substrate, and 2 is a wiring layer. The insulating substrate 1 and the wiring layer 2 constitute a wiring board 4 on which the semiconductor element 3 is mounted.

The insulating substrate 1 is made of an aluminum oxide sintered body, a mullite sintered body, an aluminum nitride sintered body,
It is made of an electrically insulating material such as a silicon carbide sintered body or a glass ceramic sintered body, and has a mounting portion for mounting the semiconductor element 3 on its upper surface, and the wiring layer 2 exposed on the surface of the mounting portion is provided with the semiconductor element 3 of the semiconductor element 3. The electrodes are connected via a connecting member 5 made of a low melting point brazing material such as solder.

When the insulating substrate 1 is made of, for example, an aluminum oxide sintered body, an appropriate organic binder and a solvent are added to and mixed with raw material powders of aluminum oxide, silicon oxide, calcium oxide, magnesium oxide and the like. A sheet-shaped ceramic green sheet (ceramic green sheet) is obtained by forming the slurry into a slurry and adopting the sheet-forming technology such as the doctor blade method and the calendar roll method which are well known in the art. Produced by cutting and punching the green sheets to form an appropriate shape, stacking a plurality of these, and finally firing the stacked ceramic green sheets in a reducing atmosphere at a temperature of about 1600 ° C. In addition, the insulating base 1 is formed from the mounting portion on the upper surface to the lower surface. A large number of wiring layers 2 are formed over the wiring member 2. The electrodes of the semiconductor element 3 are connected to the connecting member 5 made of a low melting point brazing material such as tin-lead solder in the exposed portion of the wiring layer 2. The wiring conductor of the external electric circuit board is electrically connected to the portion led out to the lower surface of the insulating substrate 1 through a low melting point brazing material such as solder.

The wiring layer 2 has a semiconductor element 3 mounted thereon.
Functioning to connect the electrodes of the to an external electrical circuit, for example,
It is formed of a metal material containing at least one of tungsten, molybdenum, molybdenum / manganese, tungsten / copper, molybdenum / copper, tungsten / molybdenum / copper, and the like, molybdenum, and manganese.

For the wiring layer 2, a metal paste obtained by adding and mixing an appropriate organic binder or solvent to a metal powder such as tungsten is formed in a predetermined pattern on a ceramic green sheet which becomes the insulating substrate 1 in advance by a conventionally known screen printing method. By printing and coating on, the insulating substrate 1 is adhered and formed at a predetermined position.

As shown in FIG. 2, the wiring layer 2 has a copper-boron plating layer 6, at least in a region where electrodes of the semiconductor element 3 are connected via a connecting member 5 made of a low melting point brazing material.
A copper plating layer 7 and a gold plating layer 8 are sequentially deposited.

The copper-boron plating layer 6 acts as a base metal layer for depositing the copper plating layer 7 and the gold plating layer 8 on the wiring layer 2 with good adhesion.

The copper-boron plating layer 6 is formed, for example, by subjecting the surface of the wiring layer 2 to palladium activation, and then using this wiring layer 2 with a boron-based compound containing a boron-based compound such as dimethylamineborane as a reducing agent. The surface of the wiring layer 2 is adhered to a predetermined thickness by immersing it in an electrolytic copper plating solution for a predetermined time. In this case, the copper-boron plating layer 6 effectively suppresses the growth of copper crystal grains by the action of the boron component contained by eutectoid deposition, and the average grain size of the copper-boron crystal grains is For example, even if there are a large number of recesses on the surface of the wiring layer 2 as a result of a small size of 0.3 μm or less, copper-boron crystals can well enter the recesses and the wiring layer 2 and the copper-boron can be It can be firmly adhered to the plating layer 6 without forming a gap between them.

The copper-boron plating layer 6 is made of copper-
In order to reduce the average grain size of boron crystal grains to 0.3 μm or less, the content of boron must be 0.3% by weight or more, and the content of boron should be 0.3% by weight or more. As a result, the grain size of the copper-boron crystal grains is 0.
The thickness is 3 μm or less, and even if the surface of the wiring layer 2 has irregularities, the wiring layer 2 enters into the recesses well and adheres firmly to the wiring layer 2.

In the copper-boron plating layer 6, if the average grain size of copper-boron crystal grains is 0.02 μm or less, the wiring layer 2 having the copper-boron plating layer 6 having irregularities on its surface is formed.
This makes it possible to adhere more firmly. Therefore, the copper-boron plating layer 6 preferably has an average grain size of copper-boron crystal grains of 0.02 μm or less, and more preferably 0.01 μm or less.

The average particle size of the copper-boron plating layer 6 is set to 0.02 μm or less by setting the content of boron in the copper-boron plating layer 6 to about 0.5% by weight or more. In consideration of characteristics such as electric conductivity, it is preferable to set it in the range of 0.5% by weight to 4% by weight.

Further, when the thickness of the copper-boron plating layer 6 is less than 0.03 μm, it is difficult to completely cover the entire surface of the wiring layer 2 with the copper-boron plating layer 6, and the copper plating described later is performed. It tends to be difficult to firmly adhere the layer 7 and the gold plating layer 8 to the wiring layer 2. Therefore, the copper-boron plating layer 6 has a thickness of 0.03.
It is preferable that the thickness is at least μm.

Furthermore, on the surface of the copper-boron plating layer 6, the copper-boron plating layer 6 and a gold plating layer 8 described later are formed.
The copper plating layer 7 having excellent adhesiveness is formed on any of the above.

The copper plating layer 7 firmly adheres the gold plating layer 8 to the wiring layer 2 and also firmly adheres the low melting point brazing material such as solder to the wiring layer 2 and the electrical conductivity of the wiring layer 2. It acts to reduce resistance.

The copper plating layer 7 is formed by, for example, immersing the wiring layer 2 on which the copper-boron plating layer 6 is deposited in an electroless copper plating solution using formalin as a reducing agent for a predetermined time. The surface of the boron plating layer 6 is formed to have a predetermined thickness. In this case, when an electroless copper plating solution using formalin as a reducing agent is used, the plating solution has an autocatalytic action, so that the surface of the copper-boron plating layer 6 is not subjected to activation treatment and the copper plating layer 7 is formed. To a predetermined thickness,
In addition, it becomes possible to adhere the copper-boron plating layer 6 with high bonding strength.

Since the copper plating layer 7 is formed of formalin or the like containing no eutectoid component and has a high purity, the bondability of the wiring layer 2 to the low melting point brazing material such as solder is greatly improved. At the same time, the electric resistance becomes a very small value, and it becomes possible to effectively prevent the occurrence of attenuation in the electric signal or the like propagating through the wiring layer 2.

The copper plating layer 7 has a gold plating layer 8 deposited on the surface thereof. The gold plating layer 8 is
It acts to prevent oxidative corrosion of the wiring layer 2, the copper-boron plating layer 6 and the copper plating layer 7 and to improve the bondability of the low melting point brazing material to the wiring layer 2.

The gold plating layer 8 is formed by depositing the copper plating layer 7 in an electroless gold plating solution containing, as a main component, gold gold cyanide as a gold compound and ethylenediaminetetraacetic acid as a complexing agent. By immersing the formed wiring layer 2 for a predetermined time, the surface of the copper plating layer 7 is adhered to a predetermined thickness.

The gold plating layer 8 has a thickness of 0.05.
When the thickness is less than μm, it may be difficult to effectively prevent the oxidative corrosion of the copper-phosphorus plating layer 6 and the copper plating layer 7, and when the thickness exceeds 0.8 μm, the semiconductor element 3 of When the electrode is connected to the wiring layer 2 via the connecting member 5 made of a low melting point brazing material such as solder, a brittle intermetallic compound is generated between tin and gold of the low melting point brazing material 5 and the semiconductor element 3 There is a risk that the reliability of the connection to the wiring layer 2 will be greatly reduced. Therefore, the gold plating layer 8
Preferably has a thickness in the range of 0.05 μm to 0.8 μm.

On the other hand, the insulating base body 1 on which the semiconductor element 3 is mounted has an upper surface to which a lid 9 is bonded via a sealing material made of resin, glass, a brazing material or the like, and insulated from the lid 9. The semiconductor element 3 is hermetically sealed inside by the base 1.

The lid 9 is made of a ceramic material such as an aluminum oxide sintered body, a mullite sintered body, an aluminum nitride sintered body, or a metal material such as an iron-nickel-cobalt alloy or an iron-nickel alloy. For example, in the case of an aluminum oxide sintered body, a raw material powder of aluminum oxide, silicon oxide, magnesium oxide, calcium oxide or the like is formed into a bowl shape by adopting a conventionally known press forming method and It is formed by firing at a temperature of about 1500 ° C.

Thus, according to the semiconductor element housing package to which the above-described wiring board of the present invention is applied, the electrodes of the semiconductor element 3 are soldered to the wiring layer 2 exposed on the surface of the mounting portion on the upper surface of the insulating substrate 1 to form a low melting point solder. Electrically and mechanically via a connecting member 5 made of a material, and thereafter, a lid 9 is joined to the upper surface of the insulating base 1 via a sealing material made of resin, glass, brazing material, etc. A semiconductor device as a final product is completed by hermetically accommodating the semiconductor element 3 inside a container composed of the base 1 and the lid 9.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, the wiring board of the present invention can be used as a semiconductor element. It may be applied to a wiring board for a hybrid integrated circuit on which electronic parts such as a capacitor and a resistor are mounted.

[0034]

According to the wiring board of the present invention, at least the electrode of the electronic component is connected to the surface of the wiring layer through the low melting point brazing material, and the content of boron is 0.3% by weight or more.
Even if there are many irregularities on the surface of the wiring layer because the copper-boron plating layer having a small crystal grain size of boron of 0.3 μm or less is deposited, the copper-boron crystals are well formed in the depressions. The wiring layer and the copper-boron plating layer are tightly adhered to each other without forming a gap between the wiring layer and the copper-boron plating layer, and the copper-boron plating layer is adhered to both the copper-boron plating layer and the gold plating layer. Since the copper plating layer having good properties is deposited, the copper plating layer and the gold plating layer can be firmly deposited on the wiring layer, and the electrical resistance of the wiring layer is reduced by the copper plating layer. In addition, the gold plating layer can effectively prevent oxidative corrosion of the wiring layer, and securely and firmly electrically connect the electrode of the electronic component to the wiring layer via the low melting point brazing material.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment in which a wiring board of the present invention is applied to a semiconductor element housing package.

FIG. 2 is an enlarged view of a main part of the wiring board shown in FIG.

[Explanation of symbols]

1 ... Insulating substrate 2 ... Wiring layer 3. ... Semiconductor elements 4 ... Wiring board 5 ... Connection members 6 ... Copper-boron plating layer 7 ... Copper plating layer 8 ... Gold plating layer 9 ... Lid

Claims (3)

[Claims] 1. A wiring board comprising a wiring layer on which an electrode of an electronic component is connected to an insulating substrate via a low melting point brazing material, wherein at least the electrode of the electronic component is low in the wiring layer. A copper-boron plating layer having a boron content of 0.3 wt% or more, a copper plating layer, and a gold plating layer are sequentially deposited on the surface of the region connected through the melting point brazing material. And a wiring board. 2. The thickness of the copper-boron plating layer is 0.03.
The wiring board according to claim 1, wherein the wiring board has a thickness of at least μm. 3. The wiring board according to claim 1, wherein the average grain size of the crystal grains of copper forming the copper-boron plating layer is 0.02 μm or less.