Semiconductor device and method for producing the same

Abstract

A high-reliability power semiconductor device uses a lead-free solder layer to connect a semiconductor chip such as an IGBT to an insulating substrate having a ceramic board and conductor layers, and a lead-free solder layer to connect the insulating substrate to a radiating base. Before the insulating substrate and the radiating base are solder-connected, the radiating base is warped such that the surface of the radiating base on the side opposite to the insulating substrate is convex. The insulating substrate is solder-connected onto the warped radiating base with the lead-free solder so as to provide a substantially flat solder-connected radiating base. When the radiating base is attached to a cooling fin, the thermal resistances are lower, and heat from the semiconductor chip is effectively dissipated so as to prevent abnormal temperature rise.

Description

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT [0001] The present invention relates to a semiconductor device and a method of producing the same, and particularly to a semiconductor device such as a power semiconductor module comprising a power semiconductor, and a method of producing the same. [0002] Power semiconductor modules capable of working even under large current and high voltage have recently been used in various fields. Such power modules comprise a power semiconductor such as an Insulated Gate Bipolar Transistor (IGBT) and a Free Wheeling Diode (FWD) as a main component. [0003]FIG. 11 is a schematic cross-sectional view showing a principal part of a conventional power semiconductor module. [0004] In a power semiconductor module 100 shown in FIG. 11, a semiconductor chip 103 of a power semiconductor, etc. is connected by a solder layer 102 onto an insulating substrate 101, which comprises a ceramic board 101a of aluminum nitride (AlN), etc. and conductor layers 101...

AI Technical Summary

Benefits of technology

[0019] In view of the above problems, an object of the present invention is to provide a low-cost, high-reliability, semiconductor device designed with environmental impact, and a method for producing the same.

[0021] In the semiconductor device, the lead-free solder is used for connecting the insulating substrate and the radiating base and for connecting the insulating substrate and the semiconductor chip, whereby elution of lead from the soldering portions is not caused even when the device is placed in an outdoor location. Further, in the semiconductor device, the radiating base is solder-connected in the approximately (i.e., substantially) flat state to the insulating substrate, whereby the radiating base can be attached to a flat surface of another member such as a cooling fin without a large gap with a preferred contact area. In addition, deterioration of the ceramic board can be prevented in the attaching step.

[0024] In the semiconductor device of the invention, the lead-free solder is used for connecting the insulating substrate and the radiating base and for connecting the insulating substrate and the semiconductor chip, lead is not eluted so as to prevent environmental contamination. Further, in the semiconductor device of the invention, the radiating base is in the approximately flat state after the connecting step using the lead-free solder, so that a large gap is not formed between the radiating base and a cooling fin, etc. and the contact thermal resistance is lowered, whereby heat generated in the semiconductor chip can be dissipated efficiently.

[0025] Thus, there is provided a high-reliability semiconductor device that can stably work without abnormal temperature rise in the semiconductor chip. Further, components of the semiconductor device may be the same as conventional ones except for using the lead-free solder, whereby a low-cost, high-reliability, semiconductor device can be realized.

Problems solved by technology

However, in production of the above power semiconductor modules, in the case of using a solder for connecting members, particularly members with different heat expansion coefficients, the following problems can result.

When electronic devices and parts using lead-containing solders are discarded, left in an outdoor location, and exposed to acid rain, etc., lead in the solders may be eluted off to cause environment contamination.

However, as compared with copper, these materials are poorer in thermal conductivity and disadvantageous in heat dissipation though they have low heat expansion coefficients.

Further, these materials are more costly than copper.

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