JP4885016B2 - Copper alloy wire for semiconductor container - Google Patents

Description

  The present invention relates to a copper alloy wire suitable for manufacturing a metal container that houses a power semiconductor designed to control electrical energy of power transmission equipment, automobiles, home appliances, and the like.

  In recent years, power semiconductor devices have attracted attention as devices for inverters such as hybrid vehicles. This power semiconductor device is formed, for example, by soldering a power semiconductor element such as a diode to the bottom of a dish-shaped metal container, and press-fitting the metal container portion of the diode into the hole of the heat sink. In practice, a power semiconductor element such as a diode is soldered to the bottom of the metal container, and then sealed with silicon resin or the like.

  Since the operating environment temperature of the semiconductor device reaches 200 ° C. or higher, high temperature solder is used as the solder. When the metal container is softened during soldering, the metal container is deformed when it is press-fitted into the hole of the heat sink, and the internal power semiconductor is cracked. Therefore, the metal container has a heat resistance Cu that does not soften during soldering. -Zr system precipitation type copper alloy is used (patent document 1).

JP 2002-261210 A

  However, some lead-free high-temperature solders that have been recently studied have a melting point of 400 ° C., and it is desired to develop a copper alloy for metal containers that has heat resistance that does not soften even when soldering at this temperature. . The copper alloy for metal containers is also required to be excellent in heat dissipation (indicator having an electrical conductivity of 50% IACS or more) and cold forgeability for forming into a metal container.

  An object of this invention is to provide the copper alloy wire for semiconductor accommodation metal containers which is excellent in heat resistance, electroconductivity (heat dissipation), and cold forgeability.

  The invention according to claim 1 is a copper alloy wire containing 0.2 to 1.1% by mass of Cr, with the balance being Cu and inevitable impurities, the elongation is 10% or more, and the conductivity is 50% IACS. As described above, the copper alloy wire for a semiconductor-containing metal container has a hardness of Hv135 or more when heated at 400 ° C. for 1 hour after cold forging.

  Invention of Claim 2 contains Cr 0.2-1.1 mass%, Furthermore, Sn0.1-1.0 mass%, 1-one or more types among Zn 0.1-1.5 mass% or less are included, The balance is a copper alloy wire composed of Cu and inevitable impurities, the elongation is 10% or more, the conductivity is 50% IACS or more, and the hardness when heated at 400 ° C. for 1 hour after cold forging is Hv135 or more There is a copper alloy wire for a semiconductor-containing metal container.

  The invention according to claim 1 is a copper alloy wire containing an appropriate amount of Cr, and the invention according to claim 2 is a copper alloy wire containing an appropriate amount of Cr and further containing an appropriate amount of at least one of Sn or Zn. The elongation is 10% or more, and the cold forgeability is excellent. Moreover, since this copper alloy wire has an electrical conductivity of 50% IACS or more, a metal container manufactured using this wire has excellent heat dissipation and heat dissipation from the semiconductor is well dissipated. In addition, since the hardness when heated at 400 ° C. for 1 hour after cold forging is Hv135 or higher, the metal container manufactured using the wire has high strength even after soldering at high temperature, and is deformed when the semiconductor device is assembled. There is no crack in the power semiconductor.

The alloy composition of the copper alloy wire of the present invention will be described in detail.
Cr precipitates in the copper matrix and contributes to improving the strength, and the precipitates prevent heat softening and improve heat resistance. The reason for limiting the Cr content to 0.2 to 1.0% by mass is that the effect cannot be sufficiently obtained if it is less than 0.2% by mass, and if the content exceeds 1.0% by mass, the effect is saturated. This is because the material cost becomes high.

  Sn dissolves in the matrix and improves strength and heat resistance. The reason why the Sn content is limited to 0.1 to 1.0% by mass is that the effect cannot be sufficiently obtained when the content is less than 0.1% by mass, and the conductivity decreases when the content exceeds 1.0% by mass. It is.

  Zn prevents solder bondability from deteriorating over time. The reason for limiting the Zn content to 0.1 to 1.5% by mass is that the effect cannot be sufficiently obtained if the content is less than 0.1% by mass. The reason for this is that the addition of excess leads to a decrease in conductivity (heat dissipation). In addition, when plating a metal container with Ni or Au, it is not necessary to contain Zn.

  In addition, the alloy composition of the copper alloy wire of the present invention contains 0.2 to 1.1% by mass of Cr, Sn is 0.1 to 1.0% by mass, and Zn is 0.1 to 1% by mass. Two types may be included within the range of 5% by mass.

  The copper alloy wire of the present invention is produced by subjecting a copper alloy ingot having the composition defined by the present invention to solution heat treatment, hot extrusion or hot rolling, wire drawing, precipitation heat treatment, for example. The wire drawing and precipitation heat treatment are repeated as desired as necessary.

  The copper alloy wire of the present invention is a copper alloy having an elongation of 10% or more, an electrical conductivity of 50% IACS or more, and a heat resistance of Hv135 or more when heated at 400 ° C. for 1 hour after cold forging, This copper alloy can be manufactured by performing the precipitation heat treatment. That is, by performing heat treatment, solid solution elements are discharged from the matrix and elongation and cold forgeability are improved, and the discharged matter (precipitate) suppresses softening of the material and heat resistance is improved.

  This copper alloy wire is cut into a predetermined length, which is made into a disk body by cold forging, and further processed into a dish-shaped metal container 1 (see FIG. 1).

  As shown in FIG. 2, the semiconductor chip 2 is soldered 3 to the bottom 1 a of the metal container 1, and the diode 4 is manufactured. As shown in FIG. 3, the metal container 1 is pressed into a hole 5 a of a heat sink 5 made of copper or aluminum to assemble the semiconductor device 6.

  In the present invention, if the clearance between the metal container 1 of the semiconductor device 6 and the radiator plate hole 5a is large, the metal container 1 is likely to come off due to vibration or the like, and the heat transfer to the radiator plate 5 becomes insufficient and is released. The amount of heat decreases. On the contrary, if the clearance is small, the metal container 1 may be deformed at the time of press fitting, and the semiconductor chip 2 may be cracked due to the distortion. In the present invention, it is preferable to use a metal container 1 having a high strength and to reduce the clearance between the metal container 1 and the heat sink hole 5a.

  In the present invention, the irregularities generated on the cut surface of the copper alloy wire may remain after cold forging and cause problems during diode fabrication. This unevenness can be reduced by adding about 0.01 to 0.04 mass% of Si to the copper alloy.

  The copper alloy wire of the present invention can be widely used for electronic and electrical equipment parts that require heat resistance and heat dissipation such as diode lead pins.

[Example 1]
Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples.
The Cu—Cr copper alloy specified in the present invention is melted by a high-frequency melting furnace and cast into a billet, and the billet is hot-extruded into a round bar at a temperature of 900 to 1000 ° C., immediately water-quenched, and then the round bar Was cold drawn to a diameter of 7.0 mm, and further subjected to precipitation hardening heat treatment at a temperature of 400 to 500 ° C. for 2 hours to produce a copper alloy wire.

Next, the copper alloy wire (circular cross section) is cut to a length of 10 mm, cold forged into a 3 mm high disk, and further cold forged to form a dish-shaped metal as shown in FIG. Container 1 was obtained. Next, the semiconductor chip 2 was soldered to the bottom 1a of the dish-shaped metal container 1 as shown in FIG. The soldering was performed using Pb—Sn solder and Au—Sn solder and heating to a temperature of 300 to 350 ° C.
As shown in FIG. 3, the obtained diode 4 is press-fitted into a hole 5a (a diameter of the hole is 0.2 to 0.4 mm smaller than the outer diameter of the metal container) of the copper heat sink 5 to assemble the semiconductor device. It was.

Tensile strength, elongation, and electrical conductivity were measured for the precipitation-hardened copper alloy wire.
Tensile strength and elongation were measured in accordance with JIS Z 2241. As for the tensile strength, an average value of 400 MPa or more was determined to be good. The elongation (mark distance 100 mm) was determined to have good cold forgeability when the average value was 10% or more. Conductivity (distance between terminals: 100 mm) was measured in a thermostatic chamber controlled at 20 ° C (± 1 ° C) by the four-terminal method, and the average value of 50% IACS or higher was judged as good heat dissipation. did.

The heat resistance of the disc having a height of 3 mm was examined by the following method.
That is, each disk was heated at 400 ° C. for 1 hour in an Ar atmosphere, cooled to room temperature, and used as a sample. The Vickers hardness of this sample was measured according to JIS Z 2244. Five points on the surface of each sample were randomly measured, and those having an average value of Hv135 or higher were determined to have good heat resistance. Vickers hardness was measured in the same manner for the sample before heating.

About the said semiconductor device, the presence or absence of the crack of a semiconductor chip was observed.
When 10 chips are measured, and all 10 chips are not cracked, the heat resistance of the metal container (copper alloy wire) is good, and if even one semiconductor chip is cracked, the heat resistance is poor. Judged.

[Example 2]
A semiconductor device was produced by the same method as in Example 1 except that the Cu—Cr—Sn copper alloy, Cu—Cr—Zn copper alloy, or Cu—Cr—Sn—Zn copper alloy defined in the present invention was used. The same investigation as in Example 1 was performed.

[Comparative Example 1]
A semiconductor device was fabricated by the same method as in Example 1 except that the Cr content was outside the specified value of the present invention, and the same investigation as in Example 1 was performed.

[Comparative Example 2]
A semiconductor device was fabricated by the same method as in Example 2 except that the content of Cr, Sn, or Zn was outside the specified value of the present invention, and the same investigation as in Example 1 was performed.

  The investigation results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1. The same investigation was conducted on the conventional material (Cu-Zr alloy). The results are also shown in Table 1.

  As shown in Table 1, the copper alloy wires of Examples 1 and 2 of the present invention example have high elongation (10% or more: good), and thus excellent cold forgeability and high-quality metal containers without defects are obtained. It was. In addition, since the metal container has high heat resistance (good), high hardness (strength) is maintained after soldering, and when the metal container is press-fitted into the hole of the heat sink, the metal container is deformed and cracked into the semiconductor chip. Never occurred.

  On the other hand, the comparative example 1 (No. 1) and the comparative example 2 No. No. 2 had a low Cr content, and therefore had low heat resistance, and cracked the semiconductor chip when the metal container was press-fitted into the hole of the heat sink. No. of Comparative Example 2 In Nos. 3 to 6, the conductivity (heat dissipating property) was lowered because the contents of Sn, Zn, or Sn and Zn were large. Since the conventional material has low heat resistance, the semiconductor chip was cracked.

It is an isometric view explanatory drawing which shows embodiment of the plate-shaped metal container manufactured using the copper alloy wire of this invention. It is side surface explanatory drawing which shows embodiment of the diode produced by soldering a semiconductor chip to the said plate-shaped metal container. It is side surface explanatory drawing which shows embodiment of the process which press-fits the said diode in a heat sink hole part, and assembles a semiconductor device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plate-shaped metal container 1a Bottom part of metal container 2 Semiconductor chip 3 Solder (joining member)
4 Diode 5 Heat sink 5a Heat sink hole 6 Semiconductor device

Claims (2)

  A copper alloy wire containing 0.2 to 1.1% by mass of Cr, with the balance being Cu and unavoidable impurities, elongation of 10% or more, conductivity of 50% IACS or more, at 400 ° C. after cold forging A copper alloy wire for a semiconductor-containing metal container, wherein the hardness when heated for 1 hour is Hv135 or more.   Cr 0.2-1.1% by mass, Sn 0.1-1.0% by mass, Zn 0.1-1.5% by mass, including at least one of the other, the balance consisting of Cu and inevitable impurities A copper alloy wire having an elongation of 10% or more, an electrical conductivity of 50% IACS or more, and a hardness when heated at 400 ° C. for 1 hour after cold forging is Hv135 or more. Copper alloy wire for use.

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