JPS6249731B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and more particularly to a semiconductor device in which an electrode on a semiconductor element and a Fe--Ni alloy lead are electrically connected to each other by an aluminum wire.

In conventional semiconductor devices such as ICs and LSIs, connections between electrodes and leads on semiconductor elements are made using Au or Al.
(alloy) wire bonding. In the case of Au wire bonding, an Au plating film is provided on the surface of the lead, while in the case of Al (alloy) wire bonding, a chemically plated Ni plating film is provided on the surface of the lead. . Although the conductive connection between the Au wire and the Au-plated film is extremely superior in terms of performance, it has the disadvantage of being expensive because it uses Au. on the other hand,
Connecting Al wires to leads coated with chemically Ni-plated film is difficult because (1) the plating speed of the Ni film on the lead is slow and it takes a long time, resulting in high costs; and (2) the cost is high. Because the surface of the bonded film is relatively rough, it is difficult to bond with the Al wire during bonding.
(3) Furthermore, even if they are bonded, they tend to peel off, making it impossible to obtain a good and reliable connection. Furthermore, thin Al wires with a diameter of 30 .mu.m are commonly used, and this causes problems such as wire breakage on the lead side and peeling of the bonded portion when plastic packaging is performed after bonding.

Therefore, an object of the present invention is to provide a highly reliable semiconductor device in which the strength of the joint between the Al wire and the lead can be increased, and a suitable connection can be easily realized.

The feature of the present invention is that when connecting the electrode on the semiconductor element and the Fe-Ni alloy lead using Al wire,
An electrical Ni plating film is provided on the surface of the lead, and the thickness thereof is 0.2 μm or more.
Furthermore, the semiconductor element and the leads are directly bonded by solder.

The present invention was made based on the confirmation of the following novel phenomenon.

(1) It is possible to form a Ni film on the surface of Fe-Ni alloy leads using an electrical method. In this case
The time required to form a Ni film is reduced to one-fifth compared to chemical methods. This makes it possible to increase lead manufacturing efficiency.

(2) The bonding strength of an Al wire to a lead having an electrical Ni plating film on its surface is related to the thickness of the Ni plating film, and sufficient bonding strength can be obtained when the thickness is 0.2 μm or more.

Hereinafter, the present invention will be explained in detail based on the drawings.

Fig. 1 shows an embodiment of the present invention, in which 1 is an Al wire and 2 is a Ni plate provided by electroplating on the surface of a lead cut from a Fe-Ni alloy lead frame. 3 is a silicon pellet, 4 is a mold resin, 5 is an electrode film provided on the silicon pellet 3, and 6 is a solder for bonding the silicon pellet 3 and the lead 7.

The Ni plating film 2 has a thickness of 0.2 μm or more, and the reason why it is 0.2 μm or more will be explained below.

Figure 2 shows the results of measuring the shear strength of the joint after bonding an Al wire 1 with a diameter of 30 μm to the lead 7 of the Ni plating film 2 with different thicknesses with the same collapse width (50 to 55 μm). It is. As a result, it is known that when the thickness of the Ni-plated film 2 is 0.2 μm or less, the shear strength is low, but when the thickness is 0.2 μm or more, the shear strength shows a nearly constant value of 23 g.

From the measurement results shown in FIG. 2, it was confirmed that a thickness of 0.2 μm or more for the Ni plating film 2 is suitable for obtaining strong bonding strength with the Ni plating film 2 in Al wire bonding.

FIG. 3 shows the relationship between the thickness of the Ni plating film 2 and the bonding rate of the Al wire 1 to the plating film during Al wire bonding. Bonding here refers to a state in which the Al wire 1 after bonding is not peeled off with almost zero force. From this measurement result, it is found that the Ni plating film 2 has a thickness of 0.2 μm or less, for example, 0.1 μm.
It was confirmed that the bonding rate to the plating film 2 was as low as 40%, but when the thickness of the Ni plating film 2 became 0.2 μm or more, the bonding rate reached 100%.

As shown in Figures 2 and 3, the bonding strength and bonding rate with respect to the thickness of the Al wire 1 and Ni plating film 2 are 100% if the plating film is 0.2 μm or more.
It can be bonded to provide sufficient strength. This is because the Ni plating film 2 with a thickness of 0.2 μm can sufficiently cover the lead 7 which is the base, and the base does not appear at the joint with the Al wire 1. (As shown in Fig. 3, when the thickness of the Ni plating film 2 is zero, the Al wire 1 does not bond to the base.) However, when the thickness of the Ni plating film 2 becomes 0.2 μm or less, It is not possible to sufficiently cover the base, and some of the base is exposed, resulting in a decrease in bonding strength.

On the other hand, the surface of the lead 7 is covered with silicon pellets 3.
When brazing with solder 6, it is heated in the air at 150 to 250°C for several minutes, so it is oxidized. Therefore, the shear strength of the bonded portion was investigated when the Al wire 1 was bonded to the oxidized Ni plating film 2.

Figure 4 shows the lead 7 having Ni-plated films 2 of different thicknesses after being heated in the atmosphere at 250°C for 1 hour.
This is the result of bonding Al wire 1 to the surface and determining the shear strength of the joint. From this result, when the thickness of the Ni-plated film 2 is 0.2 μm or less, the shear strength shows a low value of about 3 g, but when the thickness is 0.2 μm or more, it shows a shear strength of 23 g, which is the same value as before heating. It was known that As a result, it was confirmed that even a thermally oxidized Ni plating film 2 can be firmly bonded in wire bonding if the thickness of the Ni plating film 2 is 0.2 μm or more. this is,
If the thickness of the Ni plating film is 0.2 μm or more, it can sufficiently cover the base (Ni plating film is difficult to oxidize), and this is to prevent oxidation of the base.

Next, the semiconductor device is heated for a long time to a temperature higher than room temperature during operation as a product, and the bonded portion with the Al wire deteriorates and becomes easily peeled off. Therefore, we used Ni-plated films with thicknesses of 0.1, 0.2, and 4 μm to prevent aging of the joint.
The results of the study at a test temperature of 200℃ are shown in the fifth section.
As shown in the figure.

In the figure, the squares, white circles, and black circles indicate the thickness of the Ni plating film 2 is 0.1 μm, 0.2 μm, respectively.
The measured values are shown when the thickness is 4 μm. As shown by curve A in Figure 5, the thickness of the Ni plating film 2 is 0.1μ.
In the case of m, the shear strength decreases to about 4 g (5 g before the test) in 500 hours, and further decreases with the passage of time, and the shear strength shows 2 g in 2000 hours. On the other hand, as shown by the white circle in curve B, the deterioration of Ni-plated film 2 with a thickness of 0.2 μm remains the same as before the test even after 1000 hours, similar to the black circle with a thickness of 4 μm.
It exhibited a shear strength of 23g, and was confirmed to be resistant to deterioration. From the above results, it was confirmed that even with regard to aging deterioration of the bonded portion due to the thickness of the Ni plating film 2 in Al wire bonding, a strong bond can be obtained if the thickness is 0.2 μm or more.

As described above, according to the present invention, it is possible to obtain various semiconductor devices in which leads and Al wires are easily and firmly bonded with high reliability through a Ni plating film.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a resin molded semiconductor device showing an embodiment of the present invention, and Fig. 2 shows the relationship between the thickness of the Ni plating film and the shear strength when an Al wire is bonded to the Ni plating film. The diagram showing the relationship, Figure 3, is
A diagram showing the relationship between the thickness of the Ni-plated film and the bonding rate of the Al wire. Figure 4 shows the thickness of the thermally oxidized Ni-plated film and the shear strength of the joint of the Al wire bonded to this Ni-plated film. Figure 5 shows the relationship between
FIG. 3 is a diagram showing the relationship between the thickness of the Ni plating film and the aging deterioration of the bonded portion after bonding the Al wire. 1...Al wire, 2...Ni plating film, 3...
Silicon pellet, 4...Mold resin, 5...
...electrode, 6...solder, 7...lead.

Claims (1)

[Claims] 1. In a semiconductor device having a semiconductor element on a lead, and having a structure in which an electrode located on the surface of the semiconductor element and the lead are connected by an Al wire, the lead is attached to the Fe-Ni alloy surface by 0.2 μm.
1. A semiconductor device comprising an electroplated film having a thickness greater than or equal to the above thickness, and wherein the lead and the semiconductor element are bonded to each other by solder.