JP2001237359A - Semiconductor device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a conventional power semiconductor device, a connection portion between a semiconductor chip and a terminal fitting is a weak point portion, and an optimum construction method for this connection can be selectively used depending on a chip size and an energizing current value. The challenge was to be able to manage to stable quality. SOLUTION: A first electrode and a second electrode are formed on the same terminal fitting so that a wire bonding method and a direct soldering method can be selectively used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device in which a metal base on which a semiconductor chip is mounted is housed in a resin case and external terminals are led out.

[0002]

2. Description of the Related Art FIGS. 4 and 5 are sectional views of a conventional semiconductor device. Reference numeral 1 denotes a metal base, to which the semiconductor chip 2 is fixed on the upper surface by soldering. There are cases where the semiconductor chip 2 is fixed via an insulating layer and cases where the semiconductor chip 2 is not interposed. The terminal fitting 3 embedded and fixed in the resin case frame 4 is bent and extended toward the center of the resin case to form a first electrode, and is connected to the semiconductor chip 2 on the first electrode as shown in FIG. Bonding wire 7 is fixed. In some cases, the terminal fitting 3 is fixed to the upper surface of the semiconductor chip 2 with solder 8 as shown in FIG. 5. In this case, a horizontal plane having a height obtained by adding the thickness of the solder 8 to the upper surface of the semiconductor chip 2 is used. It is important that the terminal fittings 3 be embedded in the resin case frame 4 with high accuracy so that the lower surface heights of the terminal fittings 3 coincide with each other. If the solder 8 is finished in a state where it is pressed on the solder 2, the thickness of the solder 8 becomes insufficient and a connection failure occurs. Further, if a gap between the semiconductor chip 2 and the terminal fitting 3 is formed due to insufficient solder, crevice corrosion may progress and damage may be promoted. Further, when the connection is made by the bonding wire 7 in FIG. 4, the connection portion where a large current is concentrated causes abnormal heat generation, and the diameter of the bonding wire 7 in the power semiconductor chip 2 is increased. There was a limit.

[0003]

As described above, the terminal fitting which is embedded and extended on the upper surface of the semiconductor chip with poor dimensional accuracy causes poor soldering with the semiconductor chip.
Poor connection and crevice corrosion lead to damage to the semiconductor chip. Further, the maximum value of the current value determines whether or not the connection by the bonding wire is possible. When the current value exceeding the limit is applied, heat is generated at the wire connection portion due to heat generation of the wire and disconnection occurs at the connection portion. The solution to these was an issue.

[0004]

In order to solve the above-mentioned problems, a semiconductor chip provided on a metal base, a terminal fitting wired and led out from the semiconductor chip, and a resin case frame for fixing the terminal fitting are provided. In the semiconductor device in which the metal base and the resin case frame are fixed, one end of the terminal fitting is led out as an external terminal, and the other end protrudes and is exposed inside the resin case frame, and is flat as a bonding wire connection surface. Forming a first electrode in a shape of a circle, extending the tip of the first electrode, forming a second electrode as a lap joint for soldering, and connecting the semiconductor chip to the terminal fitting from the first electrode. The second electrode can be soldered directly from the second electrode or can be selected from two methods with one terminal fitting.

[0005] In order to arrange the tips of the terminal fittings on the same horizontal plane with respect to the upper surface of the semiconductor chip, the embedded and fixed terminal fittings are bent flat plate-shaped. In order to correct a dimensional difference between the horizontal surface of the first electrode and the horizontal surface of the upper surface of the semiconductor chip, a bent portion is formed in the first electrode, and the first electrode is provided with a step or an inclination.
The second electrode is formed by extending the tip of the electrode.

According to the third aspect of the present invention, it is necessary to distinguish between the case where the second electrode is accurately arranged on the upper surface of the semiconductor chip and soldering is performed, and the case where the state of the soldering surface is poor due to manufacturing variations due to manufacturing variations. Therefore, considering that the second electrode is a flat plate having a hole, it is possible to control the quality with respect to manufacturing variations by discriminating whether the excess solder at the time of completion of soldering comes out of the hole or is insufficient. ing.

According to a fourth aspect of the present invention, the shape of the second electrode is set to be a comb shape so that the finished state of the soldering can be clearly confirmed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention will be described with reference to FIG. Reference numeral 1 denotes a metal base to which a semiconductor chip 2 is fixed directly or via an insulating layer, and is wired to a terminal fitting 3. The resin case frame 4 is fixed by embedding or embracing the terminal fitting 3 and is also fixed to the metal case 1 at the same time. One end portion of the terminal fitting 3 is led out as an external terminal, and the other end portion is bent substantially at a right angle from the embedded resin case frame and projects into the resin case to form a bonding wire 7 for connection with the semiconductor chip 2. A first electrode 5 in the form of a flat plate to be fixed is formed. The first electrode has a tip extended to form a second electrode 6, which acts as a lap joint for soldering on the upper surface of the semiconductor chip.

The first electrode 5 must have a projecting length greater than the shortest dimension from the inner side surface of the resin case frame 4 at which bonding can be performed. The length dimension is determined on condition that it reaches the upper surface of the first electrode without hitting the inner wall of the fourth electrode. In addition, it is a necessary condition that the first horizontal electrode is horizontally arranged in contact with the bottom horizontal portion of the resin case frame 4 so as to withstand the bonding pressure of the jig tip.

A condition required for the second electrode 6 is that a space overlaid on the upper surface of the semiconductor chip is filled with a sufficient amount of solder so that no stress such as a pressing force or a tensile force is applied to the semiconductor chip. That is, it is held in a position, and is held within a dimension and a position range that do not hinder soldering workability.

The second electrode 6 is made of a copper plate and has typical dimensions of 1 mm in thickness and 18 m in width.
m, the length of the projecting length from the inner wall of the resin case frame 4 into the case is formed to be 30 mm, and a bent portion having a step or an inclination is formed at a position 8 mm from the inner wall, for example, an emitter electrode on the upper surface of the semiconductor chip 2. The lower surface of the second electrode 6 is held at a horizontal position higher than the layer by 0.2 mm, and the process proceeds to a soldering step, where the second electrode 6 is soldered so as to fill a gap of 0.2 mm.

The first electrode 5 is bonded to the upper surface of the semiconductor chip 2, for example, a cathode electrode layer by a thin aluminum wire. In this way, considering the current value, workability and quality variation, either wire bonding or lap joint soldering can be selected and the construction method can be used properly, so the quality is stable and the reliability is improved. Can be
Because of the improved workability, the product defect rate has been reduced, and it has become possible to provide products at low cost.

A second embodiment will be described with reference to FIG. FIG. 2 is a plan view of the second electrode 6. For example, since a hole of 1.2 mm in diameter is provided in a portion of 18 mm length of 30 mm protruding from an inner wall having a thickness of 1 mm and a width of 18 mm with a copper plate, after the lower surface thereof is soldered, the upper surface of the semiconductor chip is soldered from the hole. The appropriateness of the amount was confirmed, and it became easier to manage the variation in soldering quality.

A third embodiment will be described with reference to FIG. FIG. 3 is a plan view of the second electrode, in which a comb-shaped cut portion is formed in a flat metal plate and soldered to the upper surface of the semiconductor chip. The finished state of soldering can be checked more clearly.

[0015]

According to the present invention, the first electrode and the second electrode are formed on the same terminal fitting, and the first electrode is formed by wire bonding and the second electrode is formed by soldering. The configuration is such that the method selected according to the shape and dimensions of the upper surface of the semiconductor chip can be used properly, so that the workability is improved by using a more advantageous method.
Reliability degradation such as disconnection has been improved. For example, when manufacturing 5 series of terminal fittings for each dimension according to the current rank, the molds required to produce 10 different dimensions of fittings in each of the two conventional types could be consolidated into five types, so the required molds are required. The material can be reduced by half, and the product can be provided at low cost, which has great industrial value.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is an enlarged view of a main part of a semiconductor device according to a third embodiment of the present invention.

FIG. 4 is a structural explanatory view of a conventional semiconductor device.

FIG. 5 is a structural explanatory view of a conventional semiconductor device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 metal base 2 semiconductor chip 3 terminal fitting 4 resin case frame 5 first electrode 6 second electrode 7 bonding wire 8 solder 9 hole 10 comb-shaped electrode cutout

Claims (4)

[Claims] 1. A semiconductor chip provided on a metal base, a terminal fitting wired and led out from the semiconductor chip, and a resin case frame for fixing the terminal fitting, wherein the metal base and the resin case frame are fixed. In the semiconductor device, one end of the terminal fitting is led out as an external terminal, and the other end is projected and exposed to the inside of the resin case frame to form a first plate-shaped electrode as a bonding wire connection surface. The tip of the wire is extended and used as a lap joint for soldering.
The second electrode is formed and the wiring can be selected from the first electrode, soldered directly from the second electrode, or the connection between the semiconductor chip and the terminal. Semiconductor device. 2. The semiconductor device according to claim 1, wherein the tip of the first electrode is extended by providing a step or an inclination, and the second electrode is formed on a plane different from the first electrode. 3. The semiconductor device according to claim 1, wherein the shape of the second electrode is a flat plate having holes. 4. The semiconductor device according to claim 1, wherein the second electrode has a comb shape.