JP3370540B2 - Wiring board - Google Patents

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, or the like in which a semiconductor element is mounted by a flip chip method.

[0002]

2. Description of the Related Art In recent years, soldering has been used as a technique for mounting a semiconductor element on a wiring board used for a semiconductor element housing package for housing a semiconductor element such as an IC chip (semiconductor integrated circuit element) or a hybrid integrated circuit board. The so-called flip-chip type bonding in which the connecting electrodes of the two are directly connected using a conductive bonding material such as silver paste or a brazing material is being widely used.

To bond the input / output terminal electrodes of the semiconductor element and a conductive bonding material such as a solder ball to the semiconductor element mounting surface of the wiring board for flip-chip bonding and the semiconductor element housing package using the same. As the connection electrode pad, a micro pad or the like is formed corresponding to the input / output terminal electrode of the semiconductor element. When forming such a connecting electrode pad, for example, when a ceramic insulating substrate is used, first, a fine ceramic green sheet (ceramic green sheet) for forming a ceramic insulating substrate such as an alumina sintered body is used. After drilling holes to form predetermined through holes, and then embedding metallization ink such as tungsten or molybdenum in these through holes (through holes) by screen printing method, etc., burn at about 1600 ℃, and then through holes A ceramic insulating substrate having a so-called via hole formed of a metallized metal conductor filled in is obtained. Next, after polishing the surface of this ceramic insulating substrate to ensure the flatness of the exposed surface of the via hole, the exposed surface of the via hole is coated with nickel plating or gold plating to improve the wettability with solder. Then, a desired electrode pad for connection is formed.

Here, the reason why the ceramic surface is polished after firing the ceramic insulating substrate is that it is difficult to smoothly fill the exposed surface when the metallized ink is embedded in the fine through holes formed in the ceramic green sheet. This is to prevent the bonding between the exposed surface of the via hole and the solder ball or the like from becoming insufficient, resulting in poor reliability.

In addition, the exposed surface of the metallized metal conductor in the via hole has large irregularities, and in addition, the metallized metal conductor contracts due to firing to form a recessed portion due to the opening of the via hole and the metallized metal conductor. In many cases, the depth of the metallized metal conductor is small and the depth of the metallized metal conductor is large. Alternatively, a metallized ink such as molybdenum is applied and baked to form a flat surface metallized metal layer to cover the exposed surface of the metallized metal conductor and flatten the irregularities.

[0006]

However, according to the method of polishing the surface of the ceramic insulating substrate after firing as described above, the process is complicated and the surface of the substrate is likely to be contaminated. Therefore, the metallization in the via hole is likely to occur. Nickel plating or gold plating to improve the wettability between the connection electrode pad formed on the upper surface of the metal conductor and the solder cannot be applied sufficiently, or the adhesion between the connection electrode pad and these plated metal layers is incomplete. However, there is a problem in that the connection with the solder ball or the like or the connection with the semiconductor element becomes insufficient, and the reliability as an electronic component is significantly deteriorated. In addition, defects such as ceramic chipping are likely to occur during handling in the polishing process, and foreign substances are likely to adhere to the surface of the connecting electrode pad or metal is likely to be oxidized due to handling during polishing, so nickel plating, gold plating, etc. There is also a problem in that the plating chipping and the poor adhesion of the plated metal layer occur.

Further, when the via holes are provided at a narrow pitch in correspondence with the high integration of the semiconductor element, the surface area of the surface metallized metal layer on the upper surface of the via holes cannot be made sufficiently large. Therefore, in the firing process, a phenomenon occurs in which tungsten in one metal layer thermally diffuses into molybdenum in the other metal layer between the surface metallized metal layer and the metallized metal conductor in the via hole, and tungsten diffuses. Traces of tungsten remain as vacancies in the metal layer on the removed side, leaving the mechanical strength of the metal layer to be extremely weak, resulting in mechanical damage between the surface metallized metal layer and the metallized metal conductor in the via hole. There is also a problem that the target strength becomes weak.

The present invention has been made in view of the above circumstances, and an object thereof is a wiring board on which a semiconductor element is mounted by a flip chip method and a semiconductor element mounting package using the wiring board. Even if the via holes are formed at a narrow pitch, the surface metallized metal layer as the connection electrode pad can be firmly formed on the upper surface of the via holes, which makes it possible to plate the insulating substrate surface after firing without polishing. An object of the present invention is to provide a wiring board and a semiconductor element housing package that can secure the throwing power of a metal layer, can be manufactured at low cost, and can be flip-chip bonded with high connection reliability.

[0009]

A wiring board of the present invention is an insulating substrate having a mounting portion on the surface of which a semiconductor element is mounted, and a through hole formed in the insulating substrate, one end of which is the insulating substrate. And a surface metallized metal layer formed corresponding to the terminal electrode of the semiconductor element on the mounting part surface of the insulating substrate and connected to one end of the metallized metal conductor. In the wiring board, the metallized metal conductor and the surface metallized metal layer are made of tungsten and molybdenum, respectively, and a molybdenum content rate with respect to a total content of tungsten and molybdenum is X% by weight in the metallized metal conductor, and the surface metallized layer. When Y% by weight in the metal layer, the following formula is satisfied and the surface metallized gold is Layer, a thickness of 5μm or 30μm or less, and is characterized in that the bonding between around and conductive bonding material per the plated metal layer has good smoothness. X−20 ≦ Y ≦ X + 20, 0 ≦ X ≦ 100, 0 ≦ Y ≦ 100 where (X = 0, Y = 0) and (X = 100, Y = 10
0) is excluded.

Further, in the wiring board of the present invention, in the above structure, the surface metallized metal layer is connected to one end of the metallized metal conductor in an area of 80% or more of an exposed area of the one end of the metallized metal conductor. It is characterized by.

According to the wiring board of the present invention, the surface metallized metal layer connected to one end of the metallized metal conductor is formed on the surface of the insulating substrate on which the semiconductor element is mounted, corresponding to the terminal electrode of the semiconductor element, and the thickness thereof is reduced. Since the thickness is 5 μm or more and 30 μm or less, it is possible to obtain substantially sufficient smoothness as an electrode pad for connection with a semiconductor element without polishing the surface of the substrate after firing the insulating substrate. It is possible to achieve excellent bonding with a conductive bonding material such as, and to secure good throwing power of the plated metal layer.

Further, according to the wiring board of the present invention, the metallized metal conductor and the surface metallized metal layer are made of tungsten (W) and molybdenum (Mo), respectively, and the molybdenum content ratio with respect to the total content of tungsten and molybdenum is the above. When X wt% in the metallized metal conductor and Y wt% in the surface metallized metal layer, X-20 ≦ Y ≦ X + 20, 0 ≦ X ≦ 100, 0 ≦ Y ≦ 100
(However, (X = 0, Y = 0) and (X = 100, Y = 1
(Excluding 00)) is satisfied. Therefore, due to a large difference in tungsten content (molybdenum content) between the surface metallized metal layer and the metallized metal conductor in the firing step, The phenomenon of thermal diffusion of tungsten into molybdenum in the other metal material does not occur, and therefore, traces of tungsten remain as vacancies in the metal material on the side where the tungsten has diffused, leaving the metal material. It is possible to bond the surface metallized metal layer and the metallized metal conductor with high mechanical strength without weakening the mechanical strength of the metallized metal, and to obtain a desired mechanically and electrically good characteristic. The electrode pads for connection can be formed.

Further, according to the wiring board of the present invention, when the surface metallized metal layer is connected to one end of the metallized metal conductor in an area of 80% or more of the exposed area of the one end of the metallized metal conductor, The exposed one end of the metallized metal conductor is sufficiently covered with the surface metallized metal layer, and the throwing power of the plated metal layer to the surface metallized metal layer as the connection electrode pad is sufficiently secured, which is good. Adhesion can be obtained, and at the same time, the generation of voids due to the thermal diffusion of tungsten and the accompanying deterioration can be suppressed more effectively.

As a result of the above, in the wiring board on which the semiconductor element is mounted by the flip chip method and the package for storing the semiconductor element using the same, even if the via hole is provided on the semiconductor element mounting surface at a narrow pitch, the via hole is formed. A surface metallized metal layer as a connecting electrode pad can be firmly formed on the upper surface, which makes it possible to secure the throwing power of the plated metal layer without the need to polish the surface of the insulating substrate after firing, and it can be manufactured at low cost. Thus, it is possible to provide a wiring board and a semiconductor element accommodating package capable of flip chip bonding with high connection reliability.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a partial sectional view showing an example of an embodiment of a wiring board of the present invention. 1 in the figure is a wiring board,
Reference numeral 7 denotes a semiconductor element such as a semiconductor integrated circuit element, and in the figure, a partial cross-sectional view of a mounting portion of the wiring board 1 is shown. In this wiring board 1, 2 is an insulating substrate made of a ceramic insulating material or the like, 3 is a metallized metal conductor which is filled in a through hole formed in the insulating substrate 1 and whose one end is led out to the mounting portion surface of the insulating substrate 1, Reference numeral 4 denotes a surface metallized metal layer which is formed on the surface of the mounting portion of the insulating substrate 1 corresponding to the input / output terminal electrodes 8 arranged on the surface of the semiconductor element 7, and which is connected to one end of the metallized metal conductor 3. . Reference numeral 5 denotes Ni-Au deposited on the surface of the surface metallized metal layer 4.
The surface metallized wiring layer 4 and the plated metal layer 5 are plated metal layers made of plating or the like, and the connection electrode pads 6 are formed. Then, the semiconductor element 7 is mounted on the mounting portion of the wiring board 1, and the connecting electrode pad 6 of the wiring board 1 and the terminal electrode 8 of the semiconductor element 7 are electrically conductively joined by solder balls, silver paste, brazing material, or the like. The material 9 is joined and electrically connected.

In the wiring board of the present invention, the metallized metal conductor 3 and the surface metallized metal layer 4 are made of tungsten and molybdenum, respectively, and the molybdenum content relative to the total content of tungsten and molybdenum, that is, {molybdenum content / ( Molybdenum content + tungsten content)} × 100 (wt%), where X wt% in the metallized metal conductor 3 and Y wt% in the surface metallized metal layer 4, X-20 ≦ Y ≦ X + 2
0, 0 ≦ X ≦ 100, 0 ≦ Y ≦ 100 (where (X = 0, Y
= 0) and (excluding X = 100, Y = 100)) are satisfied. The relationship between the two X and Y is shown diagrammatically in FIG.

In the diagram of FIG. 2, the horizontal axis represents X% by weight, the vertical axis represents Y% by weight, and the hatched area A represents the range satisfying the above formula. This range A is (0,0) and (20,0), (100, when expressed by the coordinates of (X, Y).
80), (100,100), (80,100), inside the area connected by (0,20), including the line connecting each coordinate, (0,0) and (100,100) 2 points are excluded.

Further, X wt% and Y wt% are X-10.
≦ Y ≦ X + 10, 0 ≦ X ≦ 100, 0 ≦ Y ≦ 100 (however,
When (X = 0, Y = 0) and (X = 100, Y = 100) are satisfied, the generation of holes due to the thermal diffusion of tungsten and the accompanying deterioration of mechanical strength are caused. It can be suppressed more effectively, which is more preferable.

The insulating substrate 2 is made of an electrically insulating material such as an aluminum oxide sintered body, a mullite sintered body, an aluminum nitride sintered body, a silicon oxide sintered body, or a glass ceramic sintered body. If it is made of high quality sintered material, suitable organic binder for raw material powder of aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, etc.
A solvent, a plasticizer, a dispersant, etc. are added and mixed to form a sludge, and this sludge is formed into a sheet-shaped ceramic green sheet by adopting a conventionally known sheet forming method such as a doctor blade method. It is manufactured by subjecting the ceramic green sheet of No. 1 to an appropriate punching process, laminating a plurality of these, and firing at a temperature of about 1600 ° C.

The insulating substrate 2 has a mounting portion on the upper surface of which the semiconductor element 7 is mounted, and the terminal electrode 8 of the semiconductor element 7 is connected to this mounting portion via a conductive bonding material 9. While being connected to the pad 6, a resin or the like is injected into a gap between the semiconductor element 7 and the insulating substrate 2 to form a so-called underfill, which is adhesively fixed.

The metallized metal conductor 3 is composed of refractory metal powders of tungsten and molybdenum, and a metal paste obtained by adding and mixing an appropriate organic binder, solvent, plasticizer, etc. to a mixture of these powders having the above composition. (Metalized ink) is applied by printing onto the ceramic green sheet to be the insulating substrate 2 in a through hole provided in a predetermined pattern and filled, and is baked at the same time as the ceramic green sheet. While being connected to the wiring conductor layer adhered to the bottom and side surfaces,
One end thereof is formed in a predetermined pattern at a predetermined position on the surface of the mounting portion of the insulating substrate 2.

The metallized ink for forming the metallized metal conductor 3 contains various glass components such as tungsten and molybdenum within the scope of the present invention and various glass components for the purpose of matching the coefficient of thermal expansion with the insulating substrate 2. A ceramic component or the like may be added.

The metallized metal conductor 3 generally has a circular cross-section, but other shapes such as an ellipse, a triangle and a quadrangle may be used.

The surface metallized metal layer 4 is made of the same metallized ink as the metallized metal conductor 3 in which refractory metal powders of tungsten and molybdenum are mixed in the above composition, and the ceramic green sheet to be the mounting portion of the insulating substrate 2 is formed. Is connected to the surface of the through-hole filled with the metallized ink to be the metallized metal conductor 3 corresponding to the terminal electrode 8 of the semiconductor element 7 and with an area of 80% or more of the exposed area of one end of the metallized metal conductor 3. As described above, it is formed by being applied by printing. As a result, it is possible to obtain substantially sufficient smoothness as the electrode pad 6 for connection with the semiconductor element 7 without polishing the surface of the insulating substrate 2 after firing the insulating substrate 2, and solder, silver paste, brazing material, etc. It is possible to form the connection electrode pad 6 that is excellent in terms of joining with the conductive joining material 9 that is made of It is possible to secure the sex.

The shape of the surface metallized metal layer 4 is also generally circular, but it is connected to the exposed surface at one end of the metallized metal conductor 2 with an area of 80% or more, and adjacent connection electrode pads 6 are connected to each other. As long as it does not short-circuit, it may be an elliptical shape, a triangle, a quadrangle, or an irregular shape.

The surface metallized metal layer 4 preferably has a thickness of 5 μm or more, and the thickness is 5 μm.
If less than the above, the surface of the surface metallized metal layer 4 also exhibits an uneven shape due to the influence of the unevenness of the exposed surface at one end of the metallized metal conductor 3, and the throwing power of the plated metal layer 5 is improved. It tends to be difficult to obtain a sufficiently flat surface metallized metal layer 4.

On the other hand, the surface metallized metal layer 4 has a thickness of 30.
The thickness is preferably not more than 30 μm, and when the thickness is more than 30 μm, the surface metallized metal layer 4 tends to be easily peeled off due to thermal stress during firing.

There is no particular upper limit on the ratio of the area of the surface metallized metal layer 4 to the exposed area of one end of the metallized metal conductor 3, but if this ratio exceeds 4 times (400%), the high integration of the semiconductor element 7 is achieved. In the case where the terminal electrodes 8 are arranged at a high density due to the increase in the number of the electrodes and the connection electrode pads 6 are arranged at a high density accordingly, a short circuit easily occurs between the adjacent connection electrode pads 6. In order to increase the risk, it is preferable that the area of the surface metallized metal layer 4 is 4 times (400%) or less than the exposed area of one end of the metallized metal conductor 3.

On the surface of the surface metallized metal layer 4, in order to prevent the exposed surface from being oxidized and corroded and to easily and firmly bond with the conductive bonding material 9, the metallized metal layer 4 has a corrosion resistance and a conductive bonding material 9. Plated metal layer 5 made of metal with excellent bonding properties
Is preferably deposited so as to cover the surface metallized metal layer 4.

Such a plated metal layer 5 includes, for example, a laminate of a nickel (Ni) plated layer and a gold (Au) plated layer, a Ni-Au plated layer, a copper (Cu) plated layer,
A laminate of a Ni plating layer and a Cu plating layer, a laminate of a tin (Sn) plating layer or a Sn-lead (Pb) plating layer, and the like are used, and these plating layers are conventionally known to be deposited. The electroless plating method and the electrolytic plating method are adopted.

The conductive bonding material 9 mechanically bonds the terminal electrode 8 of the semiconductor element 7 mounted on the mounting portion of the wiring board 1 and the connection electrode pad 6 arranged on the surface of the wiring board 1. Solder balls made of eutectic solder of Sn and Pb or a solder material such as so-called high temperature solder containing Pb as a main component and Sn or silver (Ag) added. Alternatively, a ball-shaped one made of a low melting point brazing material such as Au—Sn is used.

The attachment to the connecting electrode pad 6 or the joining to the connecting electrode pad 6 and the terminal electrode 8 is carried out, for example, by so-called reflow heating by a belt type continuous furnace or heating by a heater block or heater chip. It is performed by a so-called flip chip bonder using the method.

[0033]

EXAMPLES Next, the wiring board of the present invention will be described based on experimental examples.

An aluminum oxide sintered body was used as the insulating substrate 2, one end of which was led to the mounting portion of the semiconductor element 7, and a metallized metal conductor 3 having a circular cross section with the diameter and metal material composition shown in Table 1 was used. , Its metallized metal conductor 3
To form a connection electrode pad 6 which is formed so as to cover one end of the semiconductor element 7 and which is formed corresponding to the terminal electrode 8 of the semiconductor element 7 and which includes the surface metallized metal layer 4 having the diameter and the metal material composition shown in Table 1. did.

At this time, the ratio of the area of the surface metallized metal layer 4 to the area of the cross section of the metallized metal conductor 3 was defined as the connection area (%).

Next, each surface metallized metal layer 4
Ni plating of 3 to 6 μm and 0.03 to 0.10 μm on the surface of
Au plating was performed to obtain wiring board samples of sample numbers 1 to 50 shown in Tables 1 and 2.

Next, a solder ball having a diameter of 180 μm made of eutectic solder of Sn: Pb = 63: 37 was used as the conductive bonding material 9 on each of 100 connection electrode pads 6 of each wiring board sample. Using a solder-plated copper plate with a thickness of 1 mm at approximately 200 ° C, attach a tensile test jig to the wiring board and copper plate with epoxy resin, and apply an external force in the vertical direction to each wiring board sample. The fracture strength and fracture mode of the joint between the connection electrode pad 6 and the conductive joint material 9 were observed.

The breaking strength is obtained by dividing the actual value of the tensile test by the number of pads (100) and the average strength per pad (g /
Pad).

The fracture mode is good if the fractured solder balls are fractured inside the solder balls,
Those broken at other portions (such as inside the surface metallized metal layer 4 and at the interface of the plated metal layer 5) were counted as defects and calculated as the defect rate (%). Then, the evaluation standard was that a sample in which even one pad broke other than solder was regarded as defective. The results are shown in Tables 1 and 2. In Tables 1 and 2, the sample numbers marked with * are outside the scope of the present invention.

[0040]

[Table 1]

[0041]

[Table 2]

Sample No. 2 in the results of Table 1 and Table 2
As can be seen from ~ 5, 7-16, 33-50, the breaking strength is 130.1 g / by setting the composition range of the metallized metal conductor 3 made of tungsten and molybdenum and the surface metallized metal layer 4 within the above range. Greater than a pad,
Since the failure rate in the break mode was 0%, it was confirmed that the wiring board of the present invention improved the joint reliability of the connection electrode pad 6.

As can be seen from the sample numbers 34, 39, 44 and 48, the connection area between one end of the metallized metal conductor 3 and the surface metallized metal layer 4 is 80% or more of the exposed area of one end of the metallized metal conductor 3. If so, breaking strength is 140.2
Since it was more than g / pad and the failure rate was 0% in the fracture mode, it was confirmed that the bonding reliability of the connection electrode pad 6 was further improved.

On the other hand, as in sample numbers 18 to 32, X-20≤Y
When it is out of the range of ≦ X + 20, the breaking strength is 120.2 g / pad or less, and the failure rate is 5% or more in the breaking mode.
It can be seen that the wiring board of the present invention is inferior in connection reliability of the connecting electrode pad.

Regarding Sample Nos. 1, 6 and 17, there was no problem in breaking strength and breaking mode, but poor adhesion of the plated metal layer to the surface metallized metal layer was observed.
The tendency was not practical.

Further, sample No. 42 is an example in which the area of the surface metallized metal layer 4 exceeds four times the exposed area of the metallized metal conductor 3. In this case, there was no problem with the breaking strength and the breaking mode, but the flip For the purpose of chip bonding, a short circuit is likely to occur between the adjacent connection electrode pads 6.

Although the examples of Tables 1 and 2 show the case where the cross-sectional shape of the metallized metal conductor 3 and the shape of the surface metallized metal layer 4 are circular, these shapes are different shapes as described above. However, similar results were obtained.

The present invention is not limited to the above examples, and changes and improvements may be added without departing from the gist of the present invention. For example, in order to further improve the bondability between the metallized metal and the ceramic of the insulating substrate, a small amount of so-called active metal such as manganese (Mn), niobium (Nb), titanium (Ti), tantalum (Ta) is contained in the metallized metal. You may add.

[0049]

According to the wiring board of the present invention, the surface metallized metal layer connected to one end of the metallized metal conductor is formed on the surface of the mounting portion of the insulating substrate so as to correspond to the terminal electrode of the semiconductor element, and its thickness is reduced. Since the thickness is 5 μm or more and 30 μm or less, it is possible to obtain substantially sufficient smoothness as a connecting electrode pad without polishing the substrate surface after firing the insulating substrate, and it is possible to bond the conductive bonding material very well. In addition to the above, it was possible to ensure good throwing power of the plated metal layer.

According to the wiring board of the present invention, the molybdenum content of the metallized metal conductor and the surface metallized metal layer, which are made of tungsten and molybdenum, respectively, is X wt% in the metallized metal conductor with respect to the total content of tungsten and molybdenum. , Y-20% by weight in the surface metallized metal layer, X-20 ≦
Y ≦ X + 20, 0 ≦ X ≦ 100, 0 ≦ Y ≦ 100 (however, (X
= 0, Y = 0) and (X = 100, Y = 100) are not satisfied, the tungsten content ratio (molybdenum content) between the surface metallized metal layer and the metallized metal conductor in the firing step is satisfied. The phenomenon of thermal diffusion of tungsten in one metal material into molybdenum in the other metal material due to the large difference in The traces of tungsten no longer remain as voids and weaken the mechanical strength of the metal material,
The surface metallized metal layer and the metallized metal conductor could be joined with high mechanical strength, and a desired connecting electrode pad having good mechanical and electrical characteristics could be formed.

According to the wiring board of the present invention, in the case where the surface metallized metal layer is connected to one end of the metallized metal conductor in an area of 80% or more of the exposed area of the one end of the metallized metal conductor, The exposed one end of the metallized metal conductor is sufficiently covered with the surface metallized metal layer, and the throwing power of the plated metal layer to the surface metallized metal layer as the connection electrode pad is sufficiently secured, which is good. Adhesion was obtained, and the generation of voids due to the thermal diffusion of tungsten and the accompanying deterioration could be suppressed more effectively.

As a result, in the wiring board on which the semiconductor elements are mounted by the flip chip method and the semiconductor element housing package using the same, even if the via holes are provided on the semiconductor element mounting surface at a narrow pitch, the via holes are formed. A surface metallized metal layer as a connecting electrode pad can be firmly formed on the upper surface, which makes it possible to secure the throwing power of the plated metal layer without the need to polish the surface of the insulating substrate after firing, and it can be manufactured at low cost. Thus, it is possible to provide a wiring board and a package for accommodating semiconductor elements, which enables flip chip bonding with high connection reliability.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an example of an embodiment of a wiring board of the present invention.

FIG. 2 is a diagram showing the relationship of molybdenum content between the metallized metal conductor and the surface metallized metal layer in the wiring board of the present invention.

[Explanation of symbols]

1 ... Wiring board 2 ... Insulating substrate 3 ... Metallized metal conductor 4 ... Surface metallized metal layer 7 ... Semiconductor element 8: Terminal electrode 9 ... Conductive bonding material

Claims (2)

(57) [Claims] 1. An insulating substrate having a mounting portion on which a semiconductor element is mounted, and a metallized metal conductor which is filled in a through hole formed in the insulating substrate and whose one end is led to the surface of the mounting portion of the insulating substrate. And a surface metallized metal layer formed on the surface of the mounting portion of the insulating substrate corresponding to the terminal electrode of the semiconductor element and connected to one end of the metallized metal conductor. made surface metallized metal layer is tungsten and Mo Ribuden respectively, and, X wt% molybdenum content to the total content of tungsten and molybdenum in the metallized metal conductor in a Y weight% by the surface metallized metal layer Satisfies the following formula
In addition, the surface metallized metal layer has a thickness of 5 μm.
30 μm or less, and the throwing power of the plated metal layer
And a wiring board having good smoothness in bonding with a conductive bonding material . X-20 ≦ Y ≦ X + 20, 0 ≦ X ≦ 100, 0 ≦ Y ≦ 100 However, (X = 0, Y = 0) and (X = 100, Y =
100) is excluded. 2. The wiring according to claim 1, wherein the surface metallized metal layer is connected to one end of the metallized metal conductor in an area of 80% or more of an exposed area of the one end of the metallized metal conductor. substrate.