JP2003008188A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of wettability and bondability of solder to a wiring layer or exfoliation, swelling, and the like, of a plating layer at the time of solder jointing. SOLUTION: On the surface of a region in a wiring layer 2 where at least the electrode of an electronic component 3 is connected through a solder ball 5; a nickel-boron plating layer 6, a nickel plating layer 7 containing 99.9 wt.% or more of nickel having mean particle size of 20 nm or above, a plating layer 8 of alloy of at least one kind of platinum, rhodium and ruthenium, and a gold plating layer 9 are formed sequentially by electroless plating.

Description

Description: 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 capacitance element, and a resistor are mounted via solder. The present invention relates to a wiring substrate formed by applying a plating layer to a wiring layer by an electroless method. 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 substrate made of a sintered body of aluminum oxide and an upper surface to a lower surface of the insulating substrate. And a plurality of wiring layers made of a refractory metal material such as tungsten or molybdenum formed over the insulating substrate.
An electronic component such as a resistor is mounted, and each electrode of the electronic 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, the wiring is mounted. Each electrode of the electronic component mounted on the substrate is electrically connected to a predetermined external electric circuit. In such a wiring board, a nickel plating layer and a gold plating layer are sequentially formed on at least a region of the wiring layer where electronic components are connected via solder.
These nickel plating layers improve the solder bonding to the wiring layer made of a refractory metal material such as tungsten, and the gold plating layer prevents nickel oxide from being formed on the nickel plating layer surface and deteriorating solder bonding properties. It is preventing. On the other hand, as a method for forming the nickel plating layer and the gold plating layer by adhesion, it is difficult to form a lead wire for supplying plating power due to the high density of the wiring conductor layer accompanying the miniaturization of the wiring board. Therefore, an electroless method that does not require a lead wire is being used frequently. An electroless nickel plating bath for forming a nickel plating layer on a wiring layer by such an electroless method generally includes a nickel compound such as nickel sulfate and a phosphorus-based reducing agent such as sodium hypophosphite. An electroless nickel-phosphorous plating bath obtained by adding a complexing agent, a pH buffering agent, a stabilizer and the like to an aqueous solution containing as a main component is used, and a nickel plating layer formed by using this is used as a reducing agent. Is a nickel-phosphorus alloy containing 5 to 15% by weight of phosphorus which is a decomposition product of However, when a nickel plating layer made of a nickel-phosphorus alloy is formed on a region of the wiring layer where electronic components are connected via solder, the solder and the nickel plating layer are bonded to each other in the solder. The reaction is carried out by reacting the tin of the nickel with the nickel of the nickel plating layer. However, since the phosphorus in the nickel-phosphorus alloy plating layer does not react with tin or lead in the solder, the solder and the nickel-phosphorus alloy plating layer Phosphorus concentrates at the interface to form an embrittlement layer. as a result,
Due to the stress generated between the wiring board and the electronic component such as a semiconductor element due to the difference in the coefficient of thermal expansion between them, a crack is formed from the embrittlement layer formed at the interface between the solder and the nickel-phosphorus alloy plating layer. As a result, there is a problem that electrical connection cannot be made. Therefore, as a means for solving such a problem, a nickel-boron alloy plating layer has been used instead of a nickel-phosphorus alloy plating layer in order to prevent the formation of an embrittlement layer. In this case, since the nickel plating layer contains 0.3 to 3% by weight of boron, which is a decomposition product of a reducing agent, an embrittlement layer is not formed. It has come to be used for substrates and the like. However, in the case where a nickel plating layer made of a nickel-boron alloy is formed on the wiring layer, the plating layer made of the nickel-boron alloy is coated with an electroless gold plating bath. There is a problem that voids are easily eluted therein, and voids formed between the nickel plating layer and the gold plating layer and voids formed by connecting the voids are likely to be generated. On the other hand, since the thermal expansion coefficient of the nickel-boron alloy is different from that of gold, the electronic component is soldered to the wiring layer on both the nickel plating layer and the gold plating layer made of the nickel-boron alloy. When heat is applied at the time of connection through the nickel plating layer, the nickel plating layer made of nickel-boron alloy and the gold plating layer have a stress generated due to a difference in thermal expansion coefficient between the nickel plating layer and the gold plating layer. Haggling and blisters occur from the void and the void formed by the connection of the voids,
As a result, there is a problem that the electronic component cannot be firmly attached to the wiring layer via solder. On the other hand, recently, as a kind of solder used for bonding an electronic component to a wiring, in addition to a general alloy of tin and lead, an alloy containing tin as a main component, for example, generally a lead-free solder is used. Alloys of the so-called tin-silver type have been used. Since these lead-free solders have a higher melting point than general tin-lead solders, the heat required to connect electronic components to the wiring layer via solder is also reduced by the tin-lead solders. Requires higher temperatures than In such a case, in a wiring board having a nickel-boron plating layer formed on a wiring layer and a gold plating layer formed on the surface thereof, a large amount of nickel atoms easily migrate and diffuse to the surface of the gold plating layer. However, since the nickel oxide layer is formed, there is a problem that the wetting property and the bonding property of the solder to the wiring layer are deteriorated. Further, a void formed on the surface of the nickel plating layer and a void formed by the stress generated between the nickel plating layer made of the nickel-boron alloy and the gold plating layer due to a difference in thermal expansion coefficient between the nickel plating layer and the gold plating layer. There is also a problem that peeling and blistering that occur from the formed void portion as a starting point is further increased as compared with a case where a general tin-lead solder is used. The present invention has been devised to solve the above-mentioned problems, and an object of the present invention is to form a nickel oxide layer by transferring and diffusing underlying nickel to the surface of a gold plating layer during solder bonding. As a result, the wetting property and bonding property of the solder to the wiring layer are deteriorated, and voids or blisters are generated from voids formed between the gold plating layer and the nickel plating layer or voids formed by connecting them. It is an object of the present invention to provide a wiring board capable of effectively preventing the occurrence of such a problem and firmly attaching an electronic component to a wiring layer via solder. A wiring board according to the present invention is a wiring board having a wiring layer to which electrodes of an electronic component are connected via solder, wherein at least the electronic component of the wiring layer is provided. On the surface of the area where the electrodes are connected via solder,
By an electroless method, a nickel-boron plating layer, a nickel plating layer having a nickel content of 99.9% by weight or more and an average particle diameter of nickel particles of 20 nm or more, at least one of platinum, rhodium, ruthenium or a mixture thereof. The present invention is characterized in that an alloy plating layer and a gold plating layer are sequentially applied. According to the wiring board of the present invention, the nickel-boron plating layer and the nickel content are formed on the surface of at least the region of the wiring layer where the electrodes of the electronic components are connected via solder by an electroless method. A nickel plating layer of 99.9% by weight or more and an average particle diameter of nickel particles of 20 nm or more, at least one of platinum, rhodium, ruthenium or an alloy plating layer thereof, and a gold plating layer sequentially formed; Therefore, even when heat is applied, particularly when the electronic component is connected to the wiring board via the solder to the wiring layer,
A nickel plating layer having a nickel content of 99.9% by weight or more and an average particle diameter of nickel particles of 20 nm or more, and a plating layer of at least one of platinum, rhodium, ruthenium or an alloy thereof, transfer nickel. Since it suppresses, solder wetting property and bonding property can be maintained high, and at least one of platinum, rhodium and ruthenium or an alloy plating layer thereof is formed on a nickel plating layer surface in a gold plating bath or a void formed on the nickel plating layer surface. Since the generation of the voids connected to each other is suppressed, it is possible to effectively prevent the occurrence of peeling and blisters starting from these voids and the voids. As a result, the electrodes of the electronic component can be very firmly connected to the wiring layer via the solder. Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of an embodiment in which the wiring board of the present invention is applied to a semiconductor element housing package for housing a semiconductor element.
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 electrically insulating material such as an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, a silicon carbide sintered body, and a glass ceramic sintered body. A mounting portion for mounting the semiconductor element 3 on the wiring layer 2 exposed on the surface of the mounting portion.
Are connected via the 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 a raw material powder of aluminum oxide, silicon oxide, calcium oxide, magnesium oxide or the like, and the mixture is mixed to form a slurry. A ceramic green sheet (ceramic green sheet) is obtained by 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 formed by cutting or 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. . 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, and each electrode of the semiconductor element 3 is soldered to a portion exposed on the mounting portion of the wiring layer 2. The wiring is electrically connected via the ball 5, and 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 function of connecting each electrode of the semiconductor element 3 to be mounted to an external electric circuit. For example, the wiring layer 2 is made of a high melting point metal powder such as tungsten, molybdenum, manganese, etc. A metal paste obtained by adding and mixing an appropriate organic binder and a solvent to the metal powder is applied to a ceramic green sheet serving as the insulating substrate 1 in a predetermined pattern by a known screen printing method in advance. It is formed from the mounting portion to the lower surface. As shown in the cross-sectional view of FIG. 2, the wiring layer 2 has a nickel-boron plating layer 6 at least in a region where the electrodes of the semiconductor element 3 are connected via the solder balls 5 by an electroless method. A nickel plating layer 7 having a nickel content of 99.9% by weight or more and an average particle diameter of nickel particles of 20 nm or more, at least one of platinum, rhodium, ruthenium or an alloy plating layer 8 thereof, and a gold plating layer 9 Are sequentially formed. The electroless method using a reducing agent as a source of electrons for reducing and precipitating metal ions in a plating bath has a larger shape than the electrolytic method in which electrons must be supplied from an external power supply. Therefore, the plating layer can be formed with a uniform thickness. Further, since there is no need for a lead wire for supplying plating power to the portion to be plated, the wiring layer 2 can be formed at a high density, and the size of the wiring board 4 can be easily reduced. The nickel-boron plating layer 6 is
A nickel plating layer 7, at least one of platinum, rhodium, ruthenium or an alloy plating layer 8 thereof, and a gold plating layer 9 serve as a base metal layer for adhesion with good adhesion. The nickel-boron plating layer 6 is formed by an electroless method 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 formed on the surface of the wiring layer 2. In this case, since the nickel-boron plating layer 6 contains boron having a strong catalytic activity therein, the wiring layer 2 is formed of a sintered body of a high melting point metal powder, so that the surface unevenness becomes large. However, no pinholes or voids are formed in the nickel-boron plating layer 6, and at the same time, the surface of the nickel-boron plating 6 can be made extremely smooth and uniform in thickness and firmly adhered. The nickel-boron plating layer 6 has a boron content of 0.1 from the viewpoint of increasing the corrosion resistance.
It is desirably 3% by weight or more, and desirably 3% by weight or less in order to avoid an increase in electric resistance. Therefore,
The nickel-boron plating layer 6 preferably has a boron content in the range of 0.3% by weight to 3% by weight. On the other hand, the thickness of the nickel-boron plating layer 6 is preferably 1 μm or more from the viewpoint of smoothing the surface of the wiring layer 2 having large irregularities and forming a uniform thickness. From the viewpoint of reducing the stress, the thickness is preferably 8 μm or less. 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 nickel plating layer 7 having a nickel content of 99.9% by weight or more and an average particle diameter of nickel particles of 20 nm or more is deposited to a predetermined thickness. Is formed. The nickel plating layer 7 firmly adheres and bonds at least one of platinum, rhodium, ruthenium or an alloy plating layer 8 thereof and a gold plating layer 9 to the nickel-boron plating layer 6, and attaches an electronic component to the wiring layer 2. This has an effect of making it difficult for nickel to move and diffuse due to heat at the time of connection through the solder ball 5 or the like. The nickel plating layer 7 is mainly composed of, for example, a nickel compound such as nickel acetate / nickel chloride and a reducing agent such as hydrazine / formalin which does not contain eutectoid in the nickel plating layer. Nickel is produced by an electroless method using an electroless nickel plating bath containing a complexing agent such as ethylenediaminetetraacetic acid (EDTA) or a sodium / potassium salt thereof, a pH buffer such as boric acid, and a stabilizer such as saccharin. -Boron plating layer 6
It is formed on the top. In this case, the nickel-boron plating layer 6 as an underlayer has an extremely smooth surface, and the nickel plating layer 7 has good adhesion to the nickel-boron plating layer 6. 6 It can be firmly adhered to a uniform thickness without forming pinholes or voids on the surface. When the nickel content of the nickel plating layer 7 is less than 99.9% by weight, the particle size of the nickel particles forming the nickel plating layer 7 is less than 20 nm due to the effect of the eutectoid component. And the crystal grain boundary sharply increases, so that nickel atoms tend to move and diffuse along the crystal grain boundary, and when connecting the electrode of the semiconductor element 3 to the wiring layer 2 via the solder ball 5, for example. When heat is applied, a nickel oxide layer is formed on the surface of the gold plating layer 9, making it difficult to firmly connect the electronic component to the wiring layer 2 via the solder balls 5. Therefore, the nickel plating layer 7 has a nickel content of 99.9% by weight.
It is necessary that the average particle diameter of the nickel particles be 20 nm or more. The thickness of the nickel plating layer 7 is desirably 0.5 μm or more from the viewpoint of completely covering the nickel-boron plating layer 6, and when the thickness exceeds 5 μm, the internal stress increases. From the viewpoint of the adhesion strength to the boron plating layer 6, the thickness is 5 μm.
It is desirable to make the following. Therefore, it is more preferable that the nickel plating layer 7 has a thickness in the range of 0.5 μm to 5 μm. Further, the nickel-boron plating layer 6 and the nickel plating layer 7
Strength between the wiring layer 2 and the wiring layer 2 and the wiring layer 2 and the insulating base 1
In order to keep the adhesion strength between the nickel-boron plating layer 6 and the wiring layer 2 high and maintain the adhesion strength between them, the total thickness thereof is preferably set to 10 μm or less. Further, on the nickel plating layer 7,
At least one of platinum, rhodium and ruthenium or an alloy plating layer 8 thereof is formed to a predetermined thickness. At least one of platinum, rhodium, and ruthenium or an alloy plating layer 8 thereof is formed to firmly adhere and bond the nickel-boron plating layer 6 and the nickel plating layer 7 to the gold plating layer 9. It acts to suppress the generation of voids and voids formed by connecting the voids on the surface. At least one of platinum, rhodium and ruthenium or its alloy plating layer 8 is, for example, in the case of platinum or its alloy, a platinum ammine complex salt such as dinitrodiammineplatinum and hydrazine, sodium borohydride or the like. A reducing agent as a main component, ethylenediamine,
Nickel is obtained by an electroless method using an electroless platinum plating bath to which a complexing agent such as ammonia, a stabilizer such as hydroxylamine salts, and ammonia (acting as a complexing agent, a stabilizer, and a pH adjuster) are added. It is formed on the plating layer 7. Note that ruthenium and rhodium can also be formed by an electroless plating bath mainly containing an ammine complex salt and a reducing agent such as hydrazine as in the case of platinum. In this case, in the electroless plating bath of platinum, rhodium and ruthenium, platinum, rhodium and ruthenium are autocatalytically precipitated by the catalytic activity of the underlying nickel, so that the underlying nickel is not dissolved in the plating bath. Therefore, it is possible to form a uniform thickness and strongly adhere without forming pinholes or voids on the surface of the nickel plating layer 7. Further, at least one of platinum, rhodium and ruthenium or an alloy plating layer 8 thereof is extremely excellent in corrosion resistance. Therefore, when a gold plating layer 9 to be formed in the next step is formed in an electroless gold plating bath. This has the effect of preventing the nickel-boron plating layer 6 and the nickel plating layer 7 from being oxidized and corroded to generate voids and voids formed by connecting the voids. The thickness of at least one of platinum, rhodium and ruthenium or an alloy plating layer 8 of the nickel-boron plating layer 6 and the nickel plating layer 7 is oxidized and corroded in an electroless gold plating bath to be the next step. From the viewpoint of effectively preventing
The thickness is desirably 5 μm or more, and the thickness is desirably 2 μm or less from the viewpoint of the bonding strength of the solder ball 5 to the wiring layer 2. Therefore, it is preferable that the thickness of at least one of platinum, rhodium and ruthenium or its alloy plating layer 8 be in the range of 0.005 μm to 2 μm. The plating layer 8 of at least one of platinum, rhodium and ruthenium or an alloy plating layer thereof may be any plating layer of at least one of platinum, rhodium and ruthenium or an alloy plating layer thereof as long as it is an electroless method. Depending on the type of reducing agent in the electroless plating bath used in forming the electroless plating bath, for example, when a reducing agent that does not contain an eutectoid such as hydrazine is used, platinum having a purity of 99.9% by weight or more is used. , Rhodium and ruthenium plating layers are obtained. A gold plating layer 9 having a predetermined thickness is formed on the surface of at least one of platinum, rhodium and ruthenium or an alloy plating layer 8 of the alloy, and the gold plating layer 9 is formed of a nickel-boron plating layer 6. The nickel plating layer 7 and at least one of platinum, rhodium and ruthenium or an alloy plating layer 8 thereof can be effectively prevented from being oxidized and corroded, and the gold plating layer 9 has extremely good solder wettability. It functions to firmly join the wiring layer 2. The gold plating layer 9 is formed, for example, using a substitution-type electroless gold plating bath containing a conventionally known gold compound such as potassium potassium cyanide and a complexing agent such as ethylenediaminetetraacetic acid (sodium salt). Platinum, rhodium,
At least one kind of ruthenium or its alloy plating layer 8
Formed on the surface. In order to effectively prevent oxidation of the nickel-boron plating layer 6, the nickel plating layer 7, and at least one of platinum, rhodium and ruthenium, or an alloy plating layer 8 thereof, the thickness of the gold plating layer 9 must be 0.05
When the thickness is more than 0.8 μm, a brittle intermetallic compound such as gold-tin is formed between the semiconductor element 3 and the solder ball 5 connecting the electrode to the wiring layer 2.
The long-term reliability of the connection tends to be low. Therefore, it is preferable that the thickness of the gold plating layer 9 be in the range of 0.05 μm to 0.8 μm. On the other hand, the insulating body 1 on which the semiconductor element 3 is mounted has a lid 10 bonded to the upper surface thereof via a sealing material made of resin, glass, brazing material, or the like. Thus, the semiconductor element 3 is hermetically sealed. The lid 10 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 well-known press forming method, and is formed into a bowl shape. It is formed by firing at a temperature of 1500 ° C. Thus, according to the wiring substrate 4 of the present invention, the electrodes of the semiconductor element 3 are electrically and mechanically connected to the wiring layer 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 10 made of metal or ceramics is joined 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 10. The semiconductor device as a product is completed by housing 3 in an airtight manner. The wiring board of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention. For example,
In the example of the above-described embodiment, the wiring board of the present invention is applied to a semiconductor element housing package for housing a semiconductor element, but may be applied to other uses such as a hybrid integrated circuit board. According to the wiring board of the present invention, a nickel-boron plating layer is formed by electroless method on at least the surface of the region of the wiring layer where the electrodes of the electronic components are connected via solder. A nickel plating layer having a nickel content of 99.9% by weight or more and an average particle diameter of nickel particles of 20 nm or more, at least one of platinum, rhodium, ruthenium or an alloy plating layer thereof, and a gold plating layer are sequentially covered. In particular, even when heat is applied when the electronic component is connected to the wiring board via the solder via the solder, the solder wetting property and the bonding property can be kept high, and Since the occurrence of blisters and blisters can be effectively prevented, the electrodes of the electronic component can be extremely firmly connected to the wiring layer via solder. Further, since a nickel-boron plating layer containing boron having a strong catalytic activity is directly formed on the surface of the wiring layer, the nickel-boron plating layer can be formed on the wiring layer without forming pinholes or voids. The surface can be made extremely smooth to form a uniform thickness and firmly adhere. Also, the nickel content on the nickel-boron plating layer, which has good adhesion to the nickel-boron plating layer, is 99.9% by weight or more, and the average particle size of the nickel particles is 20 nm or more. Since the nickel plating layer is formed by adhesion, at least one of platinum, rhodium and ruthenium or an alloy plating layer thereof and a gold plating layer can be firmly formed on the wiring layer. Further, since a nickel plating layer having a nickel content of 99.9% by weight or more and an average particle diameter of nickel particles of 20 nm or more was formed thereon, a path for moving and diffusing nickel atoms was formed. Therefore, it is possible to effectively suppress the transfer and diffusion of nickel to the surface of the gold plating layer due to heat when the electronic component is connected to the wiring layer via the solder balls. The nickel content is 99.9% by weight.
Platinum, rhodium, ruthenium or at least one of the above, and which suppresses the elution of nickel into the electroless gold plating bath with excellent corrosion resistance on the nickel plating layer having an average particle diameter of nickel particles of 20 nm or more. Since the alloy plating layer is formed, the occurrence of peeling or blistering between the gold plating layer and the nickel plating layer can be effectively prevented. Furthermore, since it becomes a barrier layer of nickel atoms which is moved and diffused by heat when the electronic component is connected to the wiring layer via a solder ball, it is possible to effectively prevent a nickel oxide layer from being formed on the surface of the gold plating layer. be able to. Further, since a gold plating layer having excellent corrosion resistance and excellent wettability with solder is formed on at least one of platinum, rhodium and ruthenium or an alloy plating layer thereof, a nickel-boron plating layer and nickel Effective prevention of oxidation corrosion of a nickel plating layer having a content of 99.9% by weight or more and an average particle diameter of nickel particles of 20 nm or more, and at least one of platinum, rhodium, ruthenium or an alloy plating layer thereof. And solder can be firmly joined. According to the wiring board of the present invention, the nickel content of the nickel plating layer is 99.9% by weight or more, the average particle size of the nickel particles is 20 nm or more, and the nickel plating layer and the gold plating layer Since at least one of platinum, rhodium and ruthenium or an alloy plating layer thereof is formed during the plating, the amount of nickel that migrates and diffuses to the surface of the gold plating layer can be extremely reduced.
For example, even if the thickness of the gold plating layer is reduced to 0.05 μm to 0.8 μm in order to prevent the formation of a large amount of a brittle intermetallic compound composed of gold and solder (such as tin), nickel is not gold. There is no problem that the oxide layer is formed by moving and diffusing to the surface of the plating layer to deteriorate the solder wetting property. Further, tin-tin which is generally called lead-free solder is used.
By using a silver-based solder, even if the heat load when connecting the electronic component to the wiring layer via the solder increases, the electronic component can be extremely easily and reliably connected to the wiring layer via the solder. The long-term reliability of the solder connection can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an example of an 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. [Description of Signs] 1 ... Insulating base 2 ... Wiring layer 3 ... Semiconductor element 4 ... Wiring board 5 ... Solder ball 6 ... Nickel-boron plating layer 7: Nickel plating layer 8: At least one of platinum, rhodium, ruthenium or its alloy plating layer 9: Gold plating layer 10: Lid

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 4E351 AA07 BB01 BB23 BB24 BB33                       BB38 CC07 DD06 DD19 DD20                       DD52 DD58 GG13 GG15                 4K022 AA04 AA42 BA03 BA04 BA14                       BA18 BA32 BA36 DA01                 5E319 AA03 AA06 AB01 AB05 AC04                       AC18 BB02 CC22 GG03                 5E343 AA23 BB09 BB17 BB23 BB24                       BB44 BB47 BB49 BB52 BB61                       BB71 DD33 GG18

Claims (1)

1. A wiring board having a wiring layer to which electrodes of an electronic component are connected via solder, wherein at least electrodes of the electronic component in the wiring layer are connected via solder. A nickel-boron plating layer, a nickel plating layer having a nickel content of 99.9% by weight or more and an average particle diameter of nickel particles of 20 nm or more, platinum, rhodium, A wiring substrate, wherein at least one of ruthenium or an alloy plating layer thereof and a gold plating layer are sequentially applied.