JP6926970B2 - Manufacturing method of semiconductor devices - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device.

For example, a semiconductor device in which a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) and a lead frame are soldered is known. In this semiconductor device, a signal pin for insertion into a connector may be formed as a part of a lead frame.

As a method for manufacturing such a semiconductor device, Patent Document 1 discloses a method for manufacturing a semiconductor device by soldering a lead frame on which a signal pin is formed in advance and a semiconductor element.

JP-A-2017-59726 (see, for example, FIG. 4).

However, in the method for manufacturing a semiconductor device described in Patent Document 1, the lead frame is softened due to heating during soldering. As a result, the mechanical strength of the signal pin formed in the lead frame in advance is lowered, so that the signal pin may be unexpectedly deformed when the signal pin is inserted into the connector.

The present invention has been made in view of the above points, and the present invention provides a method for manufacturing a semiconductor device capable of ensuring the mechanical strength of a signal pin when it is inserted into a connector.

In order to solve the above problems, the present invention manufactures a semiconductor device including a lead frame having a signal pin for inserting into a connector and a lead frame main body, and a semiconductor element soldered to the lead frame main body. The method is a preparatory step of preparing a base material corresponding to the lead frame on which the signal pin is not formed, and a portion of the prepared base material corresponding to the lead frame main body and the semiconductor element. It is characterized by including at least a soldering step of soldering and a molding step of forming the signal pin by pressing on the base material after the soldering step.

According to the present invention, after soldering a portion of the base material corresponding to the lead frame body and the semiconductor element, a signal pin is formed by press working on the base material to which the semiconductor element is soldered. Therefore, even if the metal material of the portion corresponding to the signal pin softens due to heating during soldering, the metal material of the molded signal pin is work-hardened by the press working after soldering. Mechanical strength can be ensured. As a result, the mechanical strength of the signal pin can be ensured when it is inserted into the connector.

(A) is a schematic perspective view of the semiconductor device manufactured by the manufacturing method of the present embodiment, and (b) is a cross-sectional view taken along the line AA of the semiconductor device shown in FIG. .. It is a flow diagram explaining the process of the manufacturing method of the semiconductor device which concerns on this Embodiment. It is a schematic perspective view for demonstrating the press working process shown in FIG. This is the result of the tensile test of the test piece made of the material corresponding to the signal pin. be.

An embodiment according to the present invention will be described with reference to FIGS. 1 to 4.

First, a schematic configuration of the semiconductor device 1 of the present embodiment will be described with reference to FIG. 1, and then a method of manufacturing the semiconductor device 1 of the present embodiment will be described with reference to FIGS. 2 and 3. .. FIG. 1 (a) is a schematic perspective view of the semiconductor device 1 manufactured by the manufacturing method of the present embodiment, and FIG. 1 (b) is an arrow view along the line AA of the semiconductor device 1 of (a). It is a cross-sectional view.

The semiconductor device 1 according to the present embodiment is used as a double-sided cooling type semiconductor device. As shown in FIGS. 1A and 1B, the semiconductor device 1 is joined to the lead frame 3 in which a plurality of signal pins 32 and the lead frame main body 31 are formed, and to the lead frame main body 31 via a solder layer 21. At least the semiconductor element 4 is provided. The semiconductor device 1 of the present embodiment further includes a block 6, a lead frame 7, and a sealing resin body 5. The lead frame 3 and the lead frame 7 are joined to the collector side and the emitter side of the semiconductor element 4, respectively.

A block 6 and a lead frame 7 are arranged in order on the semiconductor element 4, the semiconductor element 4 and the block 6 are joined via a solder layer 22, and the block 6 and the lead frame 7 are a solder layer. It is joined via 23. The sealing resin body 5 covers around them.

The plurality of signal pins 32 are formed at one end of the lead frame 3 and are exposed from the sealing resin body 5. In the present embodiment, the signal pin 32 is inserted into, for example, a connector (not shown) provided in an electronic device or the like. Examples of the semiconductor element 4 include an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal oxide semiconductor Field Effect Transistor), an FWD (Free Wheeling Diode), and the like. The lead frames 3 and 7 are made of aluminum, copper, or an alloy thereof, and a plating layer or the like may be formed on their surfaces.

The solder layers 21 to 23 may be either Pb-based solder or Pb-free solder, but Pb-free solder is preferable. Examples of such Pb-free solder include Sn-Ag-based solder, Sn-Cu-based solder, Sn-Ag-Cu-based solder, Sn-Zn-based solder, and Sn-Sb-based solder. The block 6 adjusts the height of the semiconductor device 1, and examples of the material include Cu and the like.

The sealing resin body 5 seals the semiconductor element 4, and examples of the material of the sealing resin body 5 include an epoxy-based thermosetting resin. The epoxy-based thermosetting resin may contain an inorganic filler such as silica, alumina, boron nitride, silicon nitride, silicon carbide, or magnesium oxide.

Next, the manufacturing method of the semiconductor device 1 according to the present embodiment will be described along with each step shown in FIG. FIG. 2 is a flow chart illustrating a process of a manufacturing method of the semiconductor device 1 according to the present embodiment. FIG. 3 is a schematic perspective view for explaining the press working process S5 shown in FIG.

<Preparation step S1>
In this step, the base material 3A corresponding to the lead frame on which the signal pin 32 is not formed is prepared (see, for example, the left figure of FIG. 3). An Au plating layer may be formed on the surface of the base material 3A in order to improve the wettability with the solder. Alternatively, an antioxidant may be applied to the surface of the base material 3A in order to prevent oxidation of a metal such as copper.

The base material 3A is composed of a portion corresponding to the lead frame main body 31 and a portion 32A corresponding to the signal pin 32. Since the signal pin 32 is formed in the press working step S5 described later, in the present embodiment, the signal pin 32 is not formed in advance unlike the conventional case, and the portion 32A corresponding to the signal pin 32 has a substantially plate shape. (For example, see the left figure in FIG. 3).

<Soldering process S2>
After the preparation step S1, the soldering step S2 is performed. In this step, the portion of the prepared base material 3A corresponding to the lead frame main body 31 and the semiconductor element 4 are soldered. Specifically, the semiconductor element 4 is laminated on the portion corresponding to the lead frame main body 31 via the solder serving as the solder layer 21. Further, the block 6 is laminated on the semiconductor element 4 via the solder serving as the solder layer 22, and the lead frame 7 is laminated on the block 6 via the solder serving as the solder layer 23. These are then heated with a predetermined thermal history (temperature profile) and joined by reflow soldering. As a result, the above-mentioned solder layers 21 to 23 are formed between the members. In this embodiment, these are joined by reflow soldering, but for example, they may be joined by individually melted solder.

<Wire bonding process S3>
The soldering step S2 is followed by the wire bonding step S3. In this step, for example, ultrasonic waves are used to connect the semiconductor element 4 and the substrate 3A via wires (not shown).

<Resin molding process S4>
After the wire bonding step S3, the resin molding step S4 is performed. In this step, as shown in FIGS. 1A and 1B, the portion including the semiconductor element 4 is covered with the sealing resin body 5 so that the portion 32A and the like corresponding to the signal pin 32 are exposed. An uncured thermosetting resin such as an epoxy resin is potted and cured by heating it.

<Pressing process S5>
In this step, a plurality of signal pins 32 are molded by press working on the base material 3A after the resin molding step S4. Specifically, as shown in the left figure of FIG. 3, cold press working is performed on the portion 32A of the base material 3A corresponding to the signal pin 32. As a result, the semiconductor device 1 as shown in the right figure of FIG. 3 can be obtained. The cold press working is preferably carried out using, for example, an 80t to 200t press machine at 25 ° C. and a reduction rate (compression deformation amount) of 50% or more of the portion 32A.

By such press working, the signal pin 32 is formed, and plastic strain is introduced into the metal material of the signal pin 32, and the metal material is work-hardened. By this work hardening, even if the portion 32A corresponding to the signal pin 32 is softened due to heating during reflow soldering, the mechanical strength of the signal pin 32 can be improved.

In particular, in the present embodiment, even when the metal material of the portion 32A corresponding to the signal pin 32 is softened by the heat of curing the thermosetting resin of the sealing resin body 5 in the resin molding step S4, after that. In addition, since the press working step S5 is performed, the mechanical strength of the signal pin 32 can be improved.

The signal pin 32 of the obtained semiconductor device 1 has a mechanical strength that can withstand deformation when it is inserted into the connector. Further, since it is not necessary to perform surface treatment such as electroless Ni-P plating on the surface of the signal pin 32, the cost can be suppressed, and by applying an antioxidant to the signal pin 32, the signal pin 32 is oxidized. Can be suppressed.

Further, according to the present embodiment, since the signal pin 32 is formed on the lead frame 3 by press working, it is not necessary to prepare only the signal pin as a separate part and join the signal pin 32. As a result, it is possible to suppress an increase in the number of parts and an increase in the work process.

In the above-mentioned manufacturing method, the press working step S5 is performed after the resin molding step S4, but if it is the soldering step S2 or later, the press working step S5 may be performed before the wire bonding step S3, and the wire bonding step S3 After that, the press working step S5 may be performed before the resin molding step S4. If the press working step S5 is performed after the soldering step S2, it is possible to suppress a decrease in the strength of the signal pin 32 due to heat during soldering.

Here, the inventor prepared a test piece made of a material (copper alloy) corresponding to a signal pin and conducted a tensile test. Specifically, a test body 1 before reflow, a test body 2 after reflow and without press working, and a test body 3 after reflow and with press working were prepared, and their tensile strengths were measured. The result is shown in FIG. The test piece 1 is not press-processed.

In addition, "after reflow" here means that the same thermal history as that at the time of reflow soldering is actually applied to the test piece, and "with press working" means the plastic strain given at the time of pressing. This is the case where the same plastic strain as in the above is applied to the test piece.

As shown in FIG. 4, the tensile strength of the test piece 2 after reflow and without press working is lower than that of the test body 1 before reflow and without press work, and the tensile strength of the test body 3 after reflow and without press work. The strength was higher than that of Specimen 2 after reflow and without press working. From this, it can be seen that the metal material of the signal pin is softened by reflow soldering, and then the softened metal material is work-hardened by press working.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various types are described within the scope of the claims as long as the spirit of the present invention is not deviated. It is possible to make design changes.

1: Semiconductor device 3: Lead frame, 31: Lead frame body, 32: Signal pin, 4: Semiconductor element, S1: Preparation process, S2: Soldering process, S5: Pressing process

Claims (1)

A lead frame having a plurality of signal pins and a lead frame body for insertion into a connector, a semiconductor element soldered to the lead frame body, and the lead frame body are covered so that the plurality of signal pins are exposed. A method for manufacturing a semiconductor device including a sealing resin body for sealing the semiconductor element.
In the manufacturing method, the plurality of signal pins are formed from the flat plate-shaped portion by pressing the flat plate-shaped portion formed on the base material with respect to the base material to be processed into the lead frame. To do,
The manufacturing method includes a preparatory step for preparing the base material and
A soldering step of soldering the semiconductor element to a portion of the prepared base material corresponding to the lead frame body,
After the soldering step, a resin molding step of molding the sealing resin body so that the flat plate-shaped portion of the base material is exposed is included.
A semiconductor device characterized in that, after the resin molding step, the flat plate-shaped portion exposed from the sealing resin body is press-processed to form the plurality of signal pins from the flat plate-shaped portion. Manufacturing method.

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