JPH0536754A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve the reliability and the economical efficiency of a semiconductor device wherein a semiconductor element is connected directly to a wiring board. CONSTITUTION:At least a palladium layer 11 is formed on a copper electrode 10 on a wiring board 12, and it is connected to a bump 3. Depending on a case, a creamy solder 13 is placed on the palladium layer 11, and the layer is connected to a bump on a semiconductor element 1. Thereby, the copper electrode 10 does not come into direct contact with a solder layer or the copper electrode 10 does not come into direct contact with the solder bump thanks to the palladium layer 11, an alloying action due to the diffusion of tin into copper which has been caused with the passage of time is not caused, and a mounting operation can be executed with extremely high reliability due to the production of pores in the solder. Alternatively, the palladium layer 11 can be formed by an electroless plating operation. This is effective in constituting a material and in simplifying a process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which a semiconductor element is directly connected to a wiring board used for ultra-compact and lightweight equipment.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device in which a semiconductor element is directly connected to a wiring board, a bump 3 is formed on an electrode 2 of a semiconductor element 1, as shown in FIG. Alloy bumps such as solder are used. A wiring electrode 5 is formed on the wiring board 4 and is usually a copper electrode. Also, to prevent copper oxidation on the copper electrode,
In some cases, the solder layer is formed by plating or a leveler to form the wiring electrode 5. The bump 3 and the wiring electrode 5 are connected to each other by screen-printing an appropriate amount of cream solder 6 with a metal mask at a position facing the bump 3 to form the semiconductor element 1.
After positioning and mounting, reflow or thermocompression bonding is performed. Alternatively, when the surface area of the wiring electrode 5 is formed of a solder layer, the cream solder 6 may not be printed, and the solder layer may be melted and connected by reflow or thermocompression bonding. Even when the bumps 3 are solder, the bumps 3 themselves may be melted and connected without printing the cream solder 6.

Further, as shown in FIG.
As the wiring electrode 5, a substrate having a copper electrode 7 plated with nickel 8 and gold 9 may be used.

[0004]

However, in the structure shown in FIG. 3, since the copper electrode, which is the wiring electrode 5, is always directly connected to the solder, the temperature in the atmosphere and the self-heating of the semiconductor element 1 may cause a time delay during use. As a result, alloying of the copper electrode with tin in the solder composition progressed, and there was a defect that tin was diffused into the copper to form a nest in the solder layer in contact with the copper electrode.
Further, since the semiconductor element 1 is directly connected to the wiring board 4, a difference in expansion coefficient between the semiconductor element 1 and the wiring board 4 is directly applied to the connection portion as stress, which causes a problem that connection reliability is significantly deteriorated. Was.

Further, the nickel plating 8 and the gold plating 9 on the copper electrode 7 for suppressing the alloying of tin and copper in the structure of FIG. 4 are effective, but the material cost itself is high,
Moreover, since there are two types of plating, there are problems that the process is complicated and the cost is high.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a semiconductor device having a simple structure with improved reliability and cost reduction.

[0007]

In order to achieve the above object, a semiconductor device of the present invention has a structure in which a palladium layer is formed on a copper electrode of a wiring board, or a solder layer is formed thereafter.

[0008]

With the above structure, the copper electrode of the wiring board and the solder are not in direct contact with each other due to the palladium layer, and the diffusion speeds of palladium, copper and tin are extremely slow. The reliability is improved without the generation of fragile nests due to excess lead.

[0009] Further, palladium can be easily formed by electroless plating, has little surface oxidation by heating, has a good solder leak property, has a lower material cost than the nickel and gold plating surface treatment system, and has a process Is also simple and reduces the cost.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment, and since 1, 2, and 3 are the same as the conventional example of FIG. 3, their explanations are omitted. Reference numeral 10 is a copper electrode, and 11 is a palladium layer formed on the copper electrode 10. That is, the wiring electrode is composed of a metal electrode such as the copper electrode 10 and the palladium layer 11. The solder layer formed by the copper electrode 10 and the cream solder 13 on the wiring substrate 12 by the formation of the palladium layer 11 is the palladium layer 11
Prevents direct alloying due to diffusion of copper and tin.

FIG. 2 shows a second embodiment, and 14 is a solder bump. In the above structure, the solder bumps 14 and the copper electrodes 10 are also not in direct contact with each other due to the palladium layer 11.

The palladium layer 11 may have a thickness of about 0.1 μm and can be formed by electroless plating. In addition, the palladium layer 11 and the cream solder 13
Plays a role if it exists at least in the area in contact with the bump.

[0013]

As described above, according to the present invention, since the wiring electrode has the palladium layer formed on the metal electrode such as copper at least in the region in contact with the bump, the copper electrode and the solder of the wiring board are formed by the palladium layer. Due to the fact that they do not come into direct contact with each other, and because the alloying due to diffusion of palladium and copper and tin respectively is extremely slow, there is no generation of cavities in the solder, and despite the direct connection to the wiring board of the semiconductor element, It is extremely reliable, and palladium itself is difficult to oxidize,
It has good solder leakability, can replace nickel and gold plating, and can be formed by electroless plating.
It is possible to provide a semiconductor device whose cost can be reduced by streamlining the material structure and manufacturing process.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor device using a cream solder according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor device using a solder bump which is a second embodiment of the present invention.

FIG. 3 is a sectional view of a conventional semiconductor device.

FIG. 4 is a cross-sectional view of another example of a wiring board used in the conventional semiconductor device of FIG.

[Explanation of symbols]

1 Semiconductor element 2 electrodes 3 bumps 10 Copper electrode 11 Palladium layer 12 wiring board 13 cream solder 14 Solder bump

Claims (2)

[Claims] 1. A semiconductor device comprising a semiconductor element connected to a wiring electrode on a wiring board via a metal or alloy bump, wherein the wiring electrode is in contact with at least the bump on a metal electrode such as copper. A semiconductor device comprising at least a palladium layer formed in a region. 2. The semiconductor device according to claim 1, wherein a solder layer is formed on at least a region of the palladium layer which is in contact with the bump.