JPS5852343B2 - Handout Taisouchino Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly, when manufacturing a semiconductor device using leads formed from a lead frame, it is possible to easily and reliably connect the leads to a semiconductor element. It is an object of the present invention to provide a method for manufacturing a semiconductor device including a means for tightening the semiconductor device.

The process order of a conventional method for manufacturing a semiconductor device will be explained below with reference to the drawings.

1st Step 2 A lead frame 1 is prepared, which is shown in a top view in FIG. 1a and partially shown in a side view in the same figure.

This lead frame has inner leads 1b, lc, and 1d protruding from a bridging support portion 1a, and among these, the inner leads 1b and 1d have their tip ends connected to each other.

As shown in FIG. 1C, the inner lead 1c will later be connected to the support 3 of the semiconductor element 2, and the inner leads 1b and 1d will be connected to the electrodes of the semiconductor element at their respective tips (after cutting). It becomes like this.

In order to facilitate the connection, a solder layer is applied, for example, to the area where dots have been made in advance.

This attachment is accomplished by dipping the part into a layer of low melting point solder.

Second step: As shown in FIG. 2a''-c, the connecting portions of the tips of the inner leads 1b and 1d of the lead frame 1 are cut to form respective ends.

Further, the inner lead 10 is bent in order to be connected to the support 3 of the semiconductor element.

1e in the figure shows the cut surface of the inner lead 1b obtained by the above processing, and the material of the lead frame, for example, copper or copper alloy (the surface of the plate is nickel plated) is exposed.

Third step: As shown in Fig. 3, the semiconductor element 2 (the solder film of the collector electrode is formed on the bottom surface, and the base electrode and the emitter electrode are formed on the top surface) is placed at a predetermined position on the support 3 by a guide. The inner leads 1c and the support body 3 are mechanically caulked, and at the same time, the tips of the base and emitter inner leads are respectively brought into contact with the solder electrodes 4 on the upper surface of the semiconductor element.

Fourth Process: After the third step, the semiconductor element is fixed to the support by the solder of the downward collector electrode by heating to about 3600 to 400°C in a reducing atmosphere (for example, in a hydrogen furnace), and at the same time the semiconductor element is fixed to the support by the solder of the downward collector electrode. The electrodes and emitter electrodes are connected to the tips of the inner leads to which they are connected by melting the solder 4 (FIG. 3) provided thereon.

At this time, as shown in FIG. 4, since the cut surface 1e of the inner lead 1b is made of copper or a copper alloy, it is pre-dipped in another solder to form a solder film on the surface (indicated by dots in the figure). The solder does not adhere well to the solder portion 4 of the electrode, and the cut surface 1e is exposed from the melted solder 4 without being fused to the solder portion 4 of the electrode.

Fifth step: After the fourth step, the surface of the semiconductor element is chemically cleaned by, for example, etching, and then a resin 5 for protecting the element is applied and dried, resulting in the result as shown in FIG.

Sixth step: Next, as an example, mold sealing is performed using silicone resin 6, etc., as shown in FIG. 6a.

Furthermore, the bridging support portion 1a of the lead frame is cut to form individual semiconductor devices as shown in FIG.

According to the above-mentioned conventional semiconductor device manufacturing method, a surface (cut surface of the inner lead) that is not compatible with a connecting body such as solder, for example, is created at the connection part of the inner lead of the lead frame with the electrode of the semiconductor element. , connections tend to be mechanically and electrically unstable.

For this reason, there is a serious drawback in that open defects (defects in conduction between an electrode and a lead of the electrode) are likely to occur during use of the semiconductor device.

In particular, recent electronic devices using semiconductor devices are required to have a To 0000 or less for serious defects such as open defects and short circuit defects (electrical short circuits).

It is generally known that in resin-encapsulated semiconductor devices, open defects often occur during long-term use due to thermal stress during use due to differences in thermal expansion coefficients between the resin, semiconductor element, and support. , this measure was strongly requested.

The present invention has been made in order to improve the above-mentioned conventional drawbacks and meet the demands.

That is, in the method of manufacturing a semiconductor device according to the present invention, a lead frame is prepared in which at least a plurality of inner leads are formed by connecting end portions to be connected to electrodes of a semiconductor element, and the connecting portion (this connecting portion) is prepared. Cutting is performed to form an end portion to be connected to an electrode or other member of a semiconductor element, and then a metal layer and/or a brazing layer is applied to the cut surface of the inner lead. It is characterized by performing the above-mentioned scheduled connections.

Hereinafter, an embodiment of the method for manufacturing a semiconductor device according to the present invention will be described with reference to the drawings, and the differences from the conventional method for manufacturing a semiconductor device will be described.

First step: A lead frame as shown in FIG. 7 is prepared.

This step differs from the first step in the conventional semiconductor device manufacturing method in that a solder layer is not deposited.

That is, the lead frame 11 is prepared as shown in a top view in FIG. 7a and in a side view in the same figure.

This lead frame has inner leads 11b, 11c, and 11d protruding from the bridging support portion 11a, and among these, the inner leads 11b and 11d have their tip ends connected to each other.

As shown in FIG. 7C, the inner lead 11c will later be connected to the support 3 of the semiconductor element 2, and the tips of the inner leads 11b and 11d will be connected to the electrodes of the semiconductor element (after cutting). .

Second step: As shown in Figure 8a, the inner lead 1 of the lead frame
The connecting portions of the tips of 1b and inner lead 11a are cut to form respective ends.

Further, the inner lead Ilc is bent in order to be connected to the support 3 of the semiconductor element.

Third step: The tip of the inner lead of the lead frame processed in the second step is immersed in, for example, a low melting point solder bath.
A solder layer is applied as indicated by dots in the figure.

This state is similar to the conventional method shown in FIG. 2C, but differs in that the cut surfaces 11e and 11f of the inner lead tip are coated with solder.

Fourth step: As shown in FIG. 10, the semiconductor element 2 (the solder film of the collector electrode is formed on the bottom surface, and the base electrode and the emitter electrode are formed on the top surface) is placed in a predetermined position on the support 3 by a guide. Then, the inner lead 11c and the support are mechanically caulked, and at the same time, the tips of the base and emitter inner leads are brought into contact with the solder electrodes 4 on the upper surface of the semiconductor element, respectively.

Step 5: After the third step, the semiconductor element is fixed to the support by the solder of the collector electrode on the lower surface by heating to about 3600 to 400°C in a reducing atmosphere (for example, a hydrogen furnace), and at the same time the base electrode emitter on the upper surface is fixed to the support. The electrodes are formed by melting the solder 4 (see Figure 10) and forming a shape like 4"
As shown in FIG. 11, each is connected to the tip of the inner lead to which it is connected.

At this time, the cut surface 11e of the inner lead. Since 11f is coated with solder, it is completely integrated with the solder layer on the side surface of the tip of the inner lead to achieve a strong connection.

Sixth Step and Seventh Step: Since there is no difference from the fifth step and sixth step of the conventional semiconductor device manufacturing method, the description will be omitted.

Furthermore, regarding the method of the present invention, the following was carried out in addition to the above.

That is, between the second and third steps of the conventional method, the tips of the inner leads are immersed in a low melting point solder layer, and the core portion is again coated with a solder layer.

As a result, the cut surfaces of the inner leads are covered with the solder layer.

According to the present invention, since the connection between the inner lead and the electrode or other member of the semiconductor element is reliable both mechanically and electrically,
Open defects, short circuit defects, etc., which were previously easy to occur during the use of semiconductor devices, have been significantly reduced.

This remarkable effect was found to be clearly different from that achieved by conventional methods in the following tests.

The semiconductor device is held in a low temperature atmosphere of -55°C for 12 minutes, and then held in a high temperature atmosphere of +150°C for 12 minutes.

(However, the temperature transition time is 6 minutes) as one cycle, and this is repeated.

The numbers in the table below are the number of defects that occur per 100 pieces.

Good results were obtained using the method of the present invention as follows.

That is, the first rounding step: The second rounding step is the same as the first step of the above-described embodiment: In the second step of the above-described embodiment, the bending process of the inner lead 11c in the latter half is not performed.

Third step: Same as the third step in the above embodiment. After the third step, the inner lead 11c is bent. The fourth step and the subsequent steps are the same as in the above embodiment.

This example was also subjected to the same tests as in the previous example.

The results are as follows, and remarkable effects were observed.

Semiconductor device according to the method of the present invention (kilocycles 0 0.5 0 01
0 02
0 05
0 110
0 515
0 1420
0 51 Semiconductor device by conventional method Note that in the above embodiments of the method of the present invention, the method of applying a solder layer to the tip portion of the inner lead, particularly the cut surface, was exemplified, but a metal layer (for example, nickel) was previously applied by plating or other means. It is also possible to apply a solder layer in advance and then apply a solder layer in a superimposed manner.

[Brief explanation of the drawing]

Figures 1 to 6 are diagrams for explaining the conventional semiconductor device manufacturing method step by step. In Figure 1, a is a top view of the lead frame, b is a side view, and C is a cross section showing the lead frame after assembly. figure,
Figure 2 a is a top view of the lead frame, b is a side view,
C is a perspective view, FIG. 3 is a side view showing assembly, FIG. 4 is a side view showing assembly, b is a partial perspective view, FIG. 5 is a partially sectional side view showing assembly, Figure 6 shows the device after assembly, Figure a is a partially sectional side view, and Figure 6 is a perspective view. 7 to 11 are for explaining the method of manufacturing a semiconductor device according to the present invention, and in FIG. 1, a is a top view of the lead frame, b is a side view, and C is a sectional view after assembly; Fig. 8a is a top view of the lead frame, b is a side view, Fig. 9 is a perspective view of the lead frame, Fig. 10 is a partially sectional side view showing assembly, and Fig. 11 is a view after assembly. FIG. 1A is a partially sectional side view, and FIG. Note that the same reference numerals in the drawings indicate the same or corresponding parts, respectively. 3...Semiconductor element support (other members), 11
...Lead frame, 11a...Bridging support portion of lead frame, 11b, 11c, 11d...
...Inner lead, 11e, 11f...Cut surface of inner lead.

Claims (1)

[Claims] 1. A step of preparing a lead frame in which at least a plurality of inner leads are formed by connecting the end portions to be connected to the electrodes of the semiconductor element, and cutting the connecting portions to connect them to the electrodes of the semiconductor element. Manufacturing a semiconductor device, comprising: forming an end portion; applying a metal layer to the cut portion of the inner lead; and connecting the end portion of the inner lead to an electrode of the semiconductor element. Method.