JP2002076595A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of a spot formed on a gold plating layer applied to a wiring layer which damages the appearance. SOLUTION: The wiring board has a wiring layer 2 connected with the electrode of an electronic component 3 through solder 5 wherein a nickel-boron plating layer 6, a palladium-boron plating layer 7 and a gold plating layer 8 are formed sequentially on the surface of a region of the wiring layer 2 being connected at least with the electronic component 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board on which electronic components such as a semiconductor element, a capacitor, and a resistor are mounted.

[0002]

2. Description of the Related Art Conventionally, a wiring board on which electronic components such as a semiconductor element, a capacitor element, and a resistor are mounted generally includes an insulating base made of an aluminum oxide sintered body and an upper surface to a lower surface of the insulating base. And a plurality of wiring layers made of a refractory metal material such as tungsten or molybdenum. The electronic component such as a semiconductor element, a capacitor, and a resistor is mounted on the upper surface of the insulating base, Each electrode of the component is electrically connected to a wiring layer via solder.

[0003] Such a wiring board is mounted on the external electric circuit board by connecting a portion of the wiring layer extending to the lower surface of the insulating base to a wiring conductor of the external electric circuit board via solder or the like, and at the same time, is mounted on the wiring board. Each electrode of the mounted electronic component is electrically connected to a predetermined external electric circuit.

The above-mentioned wiring board has a nickel layer at least in an area of the wiring layer where electronic components are connected via solder.
A nickel plating layer made of a phosphorus alloy or a nickel-boron alloy and a gold plating layer are sequentially applied, and the nickel plating layer improves the bonding of solder to a wiring layer made of a high melting point metal material such as tungsten, and The layer prevents the formation of a nickel oxide on the surface of the nickel plating layer to prevent the deterioration of the solder bonding property and the like.

When a gold plating layer is deposited on the surface of the nickel plating layer by an electroless method, nickel is catalytically inactive against deposition and deposition of gold, and deposition of the gold plating layer by an autocatalytic method. Therefore, a displacement plating method, that is, a method in which nickel is oxidized and eluted and gold is reduced and precipitated is usually used.

[0006]

However, in this conventional wiring board, when a nickel plating layer made of a nickel-phosphorus alloy is applied to a region on the wiring layer where electronic components are connected via solder, Since the phosphorus component of the nickel-phosphorus alloy is inactive and the surface of the wiring layer made of a refractory metal material such as tungsten or molybdenum is rough, the nickel made of the nickel-phosphorus alloy is formed on the entire surface of the wiring layer. The plating layer cannot be uniformly deposited, and has many pinholes (small holes) and voids (small voids). As a result, the plating solution easily remains in the pinholes and voids, and If the plating solution remains in the voids, it will seep out onto the gold plating layer due to the heat generated when connecting the electronic component to the wiring layer via solder, causing spot-like spots. Has the disadvantage that the form results in a poor appearance with.

When a nickel plating layer made of a nickel-boron alloy is deposited on the wiring layer, the nickel-boron alloy is easily oxidized and has poor corrosion resistance. Therefore, a gold plating layer is deposited by a displacement plating method. In this case, there is a disadvantage that nickel in an amount more than necessary for the reductive precipitation of gold is oxidized to form an oxide layer, and the gold plating layer cannot be firmly adhered to the surface of the nickel plating layer. Was.

The present invention has been devised in view of the above-mentioned drawbacks, and has as its object to effectively prevent poor appearance due to occurrence of spot-like spots and occurrence of peeling or blistering between a gold plating layer and a nickel plating layer. Another object of the present invention is to provide a wiring board which can securely attach an electronic component to a wiring layer via solder.

[0009]

SUMMARY OF THE INVENTION The present invention provides a wiring board having a wiring layer to which electrodes of an electronic component are connected via solder, wherein at least the electrode of the electronic component of the wiring layer is connected via solder. A nickel-boron plating layer, a palladium-boron plating layer, and a gold plating layer are sequentially deposited on the surface of a region to be connected.

In the present invention, the thickness of the palladium-boron plating layer is 0.05 μm to 2 μm.

Further, the present invention is characterized in that the nickel-boron plating layer has a boron content of 0.05% by weight to 3% by weight.

Further, the present invention is characterized in that the palladium-boron plating layer has a boron content of 2% by weight or less.

According to the wiring board of the present invention, the nickel-boron plating layer and the palladium plating layer are formed on at least the surface of the region of the wiring layer where the electrodes of the electronic components are connected via solder.
A boron-plated layer and a gold-plated layer were sequentially deposited, and a nickel-boron-plated layer containing boron having strong catalytic activity was directly deposited on the surface of the wiring layer. The surface is extremely smooth without any holes or voids, and can be adhered to the nickel-boron plating layer with both the nickel-boron plating layer and the gold plating layer. Since the palladium-boron plating layer having good properties is adhered, the gold plating layer can be firmly adhered on the nickel-boron plating layer, and further, the palladium-boron plating layer has excellent corrosion resistance, The nickel-boron plating layer and the palladium-boron plating layer are oxidized and corroded because the gold plating layer having excellent wettability with solder is applied. It is possible to effectively prevent the solder and to firmly join the solder, and as a result, it is possible to effectively prevent spot-like spots and blisters from being generated on the wiring layer of the wiring board, and to prevent the wiring layer from being damaged. The electrodes of the component can be connected very firmly via solder.

[Detailed Description of the Invention] Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment in which the wiring board of the present invention is applied to a semiconductor element housing package for housing a semiconductor element, wherein 1 is an insulating base and 2 is a wiring layer. The insulating substrate 1 and the wiring layer 2 form a wiring board 4 on which the semiconductor element 3 is mounted.

The insulating substrate 1 is made of an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite 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 the upper surface thereof. The electrodes are connected via solder balls 5.

When the insulating substrate 1 is made of, for example, an aluminum oxide sintered body, a suitable 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 ceramic green sheet (green ceramic sheet) is obtained by forming the slurry into a slurry and forming the ceramic slurry into a sheet by employing a sheet forming technique such as a doctor blade method or a calender roll method which is well known in the art. The ceramic green sheet is manufactured by cutting and punching into an appropriate shape, laminating a plurality of the sheets, and finally firing the laminated ceramic green sheet at a temperature of about 1600 ° C. in a reducing atmosphere. You.

The insulating substrate 1 has a large number of wiring layers 2 formed thereon from the mounting portion on the upper surface to the lower surface thereof. Each electrode of the semiconductor element 3 is exposed at the portion exposed on the mounting portion of the wiring layer 2. Are electrically connected via the solder balls 5,
Further, a wiring conductor of an external electric circuit board is electrically connected to a portion led out to the lower surface of the insulating base 1 via solder or the like.

The wiring layer 2 has a semiconductor element 3 mounted thereon.
A function of connecting each electrode to an external electric circuit, for example, made of a refractory metal powder such as tungsten, molybdenum, and manganese, and obtained by adding a suitable organic binder or solvent to the refractory metal powder such as tungsten and mixing. The metal paste is applied in a predetermined pattern to a ceramic green sheet serving as the insulating base 1 in advance by a conventionally known screen printing method, so that the paste is applied from the mounting portion of the insulating base 1 to the lower surface.

As shown in FIG. 2, the wiring layer 2 has a nickel-boron plating layer 6, a palladium-boron plating layer 7, and a gold plating at least in a region where electrodes of the semiconductor element 3 are connected via solder balls 5. Layers 8 are applied sequentially.

The nickel-boron plating layer 6 functions as a base metal layer that adheres the palladium-boron plating layer 7 and the gold plating layer 8 to the wiring layer 2 with good adhesion.

The nickel-boron plating layer 6 is formed by electroless plating using an electroless nickel plating bath containing a nickel compound such as nickel sulfate and a boron-based reducing agent such as sodium borohydride and dimethylamine borane. A predetermined thickness is applied to the surface of the layer 2. in this case,
Since the nickel-boron plating layer 6 contains boron having strong catalytic activity therein, pinholes and voids are formed in the nickel-boron plating layer 6 even if the surface of the wiring layer 2 is rough. However, at the same time, the surface can be made extremely smooth and a uniform thickness can be firmly applied.

The nickel-boron plating layer 6
When the content of boron is less than 0.05% by weight, the corrosion resistance of the nickel-boron plating layer 6 tends to deteriorate and it tends to be oxidized, and when it exceeds 3% by weight, the electric resistance increases. However, the characteristics as a wiring substrate tend to deteriorate. Therefore, the nickel-boron plating layer 6 preferably has a boron content in the range of 0.05% by weight to 3% by weight.

The nickel-boron plating layer 6 is
If the thickness is as thin as less than 1 μm, it becomes difficult to apply the nickel-boron plating layer 6 to the rough wiring layer 2 with a very smooth surface and to apply a uniform thickness. If it exceeds, the internal stress increases, and it becomes difficult to firmly apply the nickel-boron plating layer 6 to the wiring layer 2. Therefore, it is preferable that the nickel-boron plating layer 6 has a thickness in the range of 1 μm to 8 μm.

Further, on the nickel-boron plating layer 6, a palladium-boron plating layer 7 is adhered to a predetermined thickness, and the palladium-boron plating layer 7 is formed on the nickel-boron plating layer 6 by a gold plating layer 8. Has a function to firmly adhere and bond.

The palladium-boron plating layer 7 comprises a palladium compound such as palladium chloride and a boron-based reducing agent,
For example, it is deposited on the nickel-boron plating layer 6 by an electroless plating method using an electroless palladium plating bath containing dimethylamine borane, trimethylamine borane, or the like. In this case, the underlying nickel-boron plating layer 6 has an extremely smooth surface, and the palladium-boron plating layer 7 has a nickel-boron plating layer formed by an autocatalytic reaction in which a palladium compound in the plating solution is reduced and precipitated with a reducing agent. Since the nickel-boron plating layer 7 is not oxidized on the nickel-boron plating layer 6, the palladium-boron plating layer 7 has a uniform thickness without forming pinholes or voids on the surface of the nickel-boron plating layer 6. , And can be firmly adhered.

The palladium-boron plating layer 7
When the boron content exceeds 2% by weight, the amount of boron component having poor adhesion to gold increases, and the adhesion of a gold plating layer described later tends to deteriorate. Therefore, it is preferable that the palladium-boron plating layer 7 has a boron content of 2% by weight or less.

The palladium-boron plating layer 7
When the thickness is as thin as less than 0.05 μm, the nickel-boron plating layer 6 cannot be completely covered, and the adhesion strength of the gold plating layer 8 tends to be weak, If it exceeds 2 μm, the internal stress tends to increase, and the adhesion strength to the nickel-boron plating layer 6 tends to be low. Therefore, the palladium-phosphorus plating layer 7 has a thickness of 0.05 μm to 2 μm.
Is preferably set in the range.

Further, on the surface of the palladium-boron plating layer 7, a gold plating layer 8 is applied to a predetermined thickness, and the gold plating layer 8 is formed by oxidizing the nickel-boron plating layer 6 and the palladium-boron plating layer 7. Corrosion can be effectively prevented, and has the effect of firmly joining the solder to the wiring layer 2.

For the gold plating layer 8, for example, a substitution type electroless gold plating solution containing a conventionally known gold compound such as potassium potassium cyanide and a complexing agent such as ethylenediaminetetraacetic acid (sodium salt) is used. It is formed on the surface of the palladium-phosphorous plating layer 7 by an electroless plating method.

In this case, since the palladium-boron plating layer 7 has excellent corrosion resistance, the palladium-boron plating layer 7 is not oxidized more than the amount necessary for reducing gold, and the gold plating layer 8 is not oxidized. Can be firmly formed on the palladium-boron plating layer 7.

The gold plating layer 8 has a thickness of 0.05
When the thickness is less than μm, it is difficult to prevent oxidation of the palladium-boron plating layer 7 and the nickel-boron plating layer 6, and when the thickness exceeds 0.8 μm, the electrodes of the semiconductor element 3 are attached to the wiring layer 2. A brittle intermetallic compound such as gold-tin may be formed between the solder ball 5 and the solder ball 5 to be connected, and the long-term reliability of the connection may be reduced. Therefore, it is preferable that the thickness of the gold plating layer 8 be in the range of 0.05 μm to 0.3 μm.

On the other hand, the insulating substrate 1 on which the semiconductor element 3 is mounted has a lid 9 joined to the upper surface thereof via a sealing material made of resin, glass, brazing material or the like. The semiconductor element 3 is hermetically sealed by the base 1.

The lid 9 is made of a ceramic material such as an aluminum oxide sintered body, a mullite sintered body, or 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 a sintered body made of aluminum oxide, a raw material powder such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide is formed into a bowl shape by employing a conventionally known press molding method, and then formed into a bowl shape. It is formed by firing at a temperature of about 1500 ° C.

Thus, according to the wiring board 4 of the present invention, the electrodes of the semiconductor element 3 are electrically and mechanically connected to the wiring layers 2 exposed on the surface of the mounting portion on the upper surface of the insulating base 1 via the solder balls 5. Thereafter, a lid 9 made of metal or ceramics is bonded to the upper surface of the insulating base 1 via a sealing material such as glass, resin, brazing material or the like, and a semiconductor element is placed inside the container formed of the insulating base 1 and the lid 9. The semiconductor device as a product is completed by housing 3 in an airtight manner.

It should be noted that the wiring board of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. Although the wiring board of the present invention is applied to a semiconductor element housing package for housing a semiconductor element, it may be applied to other uses such as a hybrid integrated circuit board.

The “solder” in the present invention is not limited to a general alloy of tin (Sn) and lead (Pb) but is a low-melting alloy containing tin (Sn) as a component, for example, “lead-free solder” And tin-silver based alloys.

[0037]

According to the wiring board of the present invention, the nickel-boron plating layer, the palladium-boron plating layer, and the gold plating are formed on at least the surface of the region of the wiring layer where the electrodes of the electronic components are connected via solder. The layers are sequentially deposited, and the nickel-boron plating layer containing boron having a strong catalytic activity is directly deposited on the surface of the wiring layer, so that the nickel-boron plating layer causes pinholes and voids in the wiring layer. Palladium which can be adhered to a nickel-boron plating layer with good adhesion to both the nickel-boron plating layer and the gold plating layer. -Since the boron plating layer is deposited, the gold plating layer can be firmly deposited on the nickel-boron plating layer. The gold-plated layer, which has excellent corrosion resistance and solder wettability, is deposited on the plating layer, so that the nickel-boron plating layer and the palladium-boron plating layer are effectively prevented from being oxidized and corroded. And the solder can be firmly joined. As a result, spots and blisters can be effectively prevented from being generated on the wiring layer of the wiring board, and the electrodes of the electronic component can be soldered to the wiring layer. The connection can be very firmly connected.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a wiring board of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating base 2 ... Wiring layer 3 ... Semiconductor element 4 ... Wiring board 5 ... Solder bump 6 ... Nickel-boron plating layer 7 ... Palladium-boron plating layer 8 Gold plating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 23/12 P

Claims (4)

[Claims] 1. A wiring board having a wiring layer to which electrodes of an electronic component are connected via solder, wherein at least a surface of a region of the wiring layer where electrodes of the electronic component are connected via solder, A wiring board comprising a nickel-boron plating layer, a palladium-boron plating layer, and a gold plating layer sequentially deposited thereon. 2. The palladium-boron plating layer has a thickness of 0.05 μm to 2 μm.
The wiring board according to claim 1. 3. The wiring board according to claim 1, wherein the nickel-boron plating layer has a boron content of 0.05% by weight to 3% by weight. 4. The palladium-boron plating layer has a boron content of 2% by weight or less.
The wiring board according to claim 1.