JPS6393835A - Copper alloy for lead material of semiconductor equipment - Google Patents

Abstract

PURPOSE:To improve the adhesive strength of oxide film and the thermal peeling resistance of solder, by incorporating specific amounts of Cr, Si, and Mg to copper. CONSTITUTION:This copper alloy has a composition which consists of, by weight, 0.05-1.0% Cr, 0.01-1.0% Si, 0.01-1.0% Mg, and the balance Cu and containg, if necessary, 0.01-1.0%, in total, of one or more elements among Ni, Al, Be, Ti, Hf, Co, and In. As semiconductor equipment lead material, this copper alloy has superior electrical and thermal conductivities, mechanical properties, adhesive strength of plating, solderability, and corrosion resistance and also is excellent in the adhesive strength of the oxide film formed on a lead surface as well as in the peeling resistance of solder against the change with the lapse of time during use. In this copper alloy, when the amounts of Cr and Si are below the lower limits, respectively, neither strength nor wear resistance is satisfied and, when above the upper limits, electric conductivity after aging is reduced. Moreover, when Mg content is below the lower limit, remarkable improving effects of the peeling resistance of solder and the adhesive strength of oxide film cannot be expected and, when above the upper limit, electric conductivity is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Objectives) The present invention relates to a steel alloy for lead materials of semiconductor devices such as transistors and integrated circuits (ICs).

(Prior art and problems) Conventionally, high nickel materials such as Kovar (F e 29N i 16Co) and 42 alloy, which have a low coefficient of thermal expansion and good adhesion and sealing properties with elements and ceramics, have been used as lead materials for semiconductor devices. Alloys have been preferred. but,
In recent years, as the degree of integration of semiconductor circuits has improved, the number of ICs with high power consumption has increased, resins have been increasingly used as sealing materials, and improvements have been made to the bonding of elements and lead frames. Copper-based alloys with good heat dissipation are now being used as lead materials.

Generally, lead materials for semiconductor devices are required to have the following properties.

(1) Leads must exhibit excellent thermal and electrical conductivity, as they are required to act as an electrical signal transmission part and also have the function of discharging heat generated during the packaging process and circuit use to the outside. .

(2) Since the adhesion between the lead and the mold is important from the perspective of protecting the semiconductor device, the thermal expansion coefficients of the lead material and the mold material are close, and the adhesion of the oxide film formed on the surface of the lead is good. thing.

(3) It must have good heat resistance since various heating processes are involved during packaging.

(4) Since most leads are manufactured by punching and bending lead material, the workability of these materials must be good.

(5) Since the surface of the lead is plated with precious metals, the plating must have good adhesion to these precious metals.

(6) exposed outside the sealing material after packaging;
Since many items are soldered to the outer leads, good soldering should not only show good soldering properties but also have peeling resistance against changes over time during use.

(7) Good corrosion resistance from the standpoint of equipment reliability and lifespan.

(8) Prices are low.

With respect to these various required characteristics, the oxygen-free copper, tin-containing copper, phosphor bronze, copal, and 42 alloy that have been used conventionally all have advantages and disadvantages, and do not satisfy all of these characteristics.

On the other hand, although the Cu-Cr-Si alloy satisfies the above-mentioned required characteristics to a large extent, there is a need for improvement in terms of heat peeling resistance of solder and oxide film adhesion.

(Structure of the Invention) The present invention has been made in view of the above points, and the present invention has been made in view of the above points.
The present invention aims to improve the drawbacks of the -Cr-Si alloy and to provide a copper alloy having various properties suitable as a lead material for semiconductor devices.

The present invention has a Cr content of 0.05 wt% or more and 1.0 wt% or less.
, 0.01wt% or more and 1.0wt% or less of Si, 0.01wt% or more and 1.0wt% or less of Si.
Copper alloy for lead material of semiconductor devices, containing 0.01 wt% or more and 1.0 wt% or less Mg, and the balance consisting of Cu and unavoidable impurities, and 0.05 wt% or more and 1.0 wt% or less Cr, 0.01 wt% or more , 1.0wt% or less Si
, 0.01wt% or more and 1.0wt% or less of M'g and one or more selected from the group consisting of Ni, AI, Be, Ti, Hf, Go, and In in a total amount of 0.01wt.
% or more and 1.0 wt% or less, with the balance being Cu and unavoidable impurities, the steel alloy is for lead material of semiconductor devices, and has excellent electrical and thermal conductivity, mechanical properties, oxide film adhesion workability, and plating adhesion. It is characterized by having good properties such as durability, soldering properties, and corrosion resistance.

(Detailed Description of the Invention) Next, the reasons for limiting the alloy components constituting the alloy of the present invention will be explained.S The content of Cr is set to 0.05 wt% or more and 1.0 wt% or more.
The content of Cr is 0.05 wt% or less.
If it is less than 1.0 wt%, the amount of intermetallic compounds formed with other additive elements will not be sufficient and the expected strength and heat resistance will not be obtained.On the other hand, if it exceeds 1.0 wt%, it will not be possible to form a solid solution in Cu after solution treatment. This is because the electrical conductivity after aging decreases significantly as the amount of Cr increases. The content of Si is 0.01 wt% or more,
The Si content is 0.01 wt% or less.
If it is less than 1.0 wt%, the amount of intermetallic compounds formed with other additive elements will not be sufficient and the expected strength and heat resistance will not be obtained, and if it exceeds 1.0 wt%, residual S will form a solid solution in Cu after aging.
This is because the electrical conductivity decreases significantly as the amount of i increases. Mg is an effective component for improving oxide film adhesion and heat-removability of solder, and at the same time improving strength without deteriorating workability. Mg content is 0.0
This is because when the Mg content is less than 1 wt%, the effect of reducing the resistance due to the Mg content is not significant, whereas when the Mg content exceeds 1.0 wt%, the conductivity decreases significantly.

Furthermore, the addition of one or more selected from the group consisting of Ni, Al, Be, Ti, Hf, Co, and In improves strength and heat resistance without significantly reducing conductivity. This is because the content is set to 0.01 wt% or more and 1.0 wt% or less in total because the above effect cannot be expected if it is less than 0.01 wt%, so 1.0 wt% is This is because if it exceeds the range, the conductivity will drop significantly.

(Effects of the Invention) The alloy of the present invention has excellent strength, electrical conductivity, and heat resistance, and exhibits moderately good mechanical properties such as strength and elongation for punching and bending, and is suitable for soldering. It is a copper alloy with good adhesive properties, plating adhesion, and corrosion resistance. In addition, the copper alloy has good solder peeling resistance and oxide film adhesion, which are important technical items for the premise of not reducing reliability, which is a key point when making a copper alloy for a lead frame. or,
Its coefficient of thermal expansion is close to that of plastic, making it suitable for plastic packaging. No prior art alloy has this combination of overall properties.

(Example) The material of the present invention will be explained below with reference to Examples.

Ingots having various compositions of the alloys of the present invention shown in Table 1 were melted and cast using electric or oxygen-free copper as a raw material in a high-frequency melting furnace in air, an inert atmosphere, or a reducing atmosphere.

Next, after solidifying these ingots, they were heated at 850° C. for 1 hour and hot rolled into a 5 nn plate. This thickness 5
The plate I was subjected to solution treatment at 950°C for 1 hour, cold rolled into a plate with a thickness of 0.25 m, and finally aged at 400°C for 2 hours.

To evaluate the sample prepared in this way as a lead material, the strength and elongation were measured by a tensile test, and the bendability was measured by repeated 90° reciprocating bending at the same bending radius as the plate thickness (=0.25 mm) (until breakage). The heat resistance was shown by the softening temperature at a heating time of 5 minutes, and the electrical conductivity (heat dissipation) was shown by the electrical conductivity (% engineering AC3). This is because electrical conductivity and thermal conductivity are proportional to each other and can be evaluated by electrical conductivity. Soldering strength is 230± by vertical dipping method.
It was immersed in a solder bath (S n 60%, Pb 40%) at 5° C. for 5 seconds, and the state of solder wetting was evaluated visually. The peeling resistance of the solder was determined by heating the sample soldered by the above method in the air for 150'C for 11,500 hours.
A 90° bend of 25R was performed to evaluate the presence or absence of peeling chicks. Plating adhesion was evaluated by applying Ag plating to a thickness of 3 μm to a sample and visually observing the presence or absence of blisters occurring on the surface. Oxide film adhesion was determined by heating the sample at 400°C for 1 minute, then carving the surface of the material with a grid knife at 2 mm intervals.
Adhesive tape was applied, peeled off from the material, and adhesion was evaluated based on the presence or absence of an oxide film adhering to the tape. These results are shown in Table 1 along with comparative alloys.

As shown in Table 1, it is clear that the alloy of the present invention exhibits excellent electrical and thermal conductivity, mechanical properties, oxide film adhesion, plating adhesion, solderability, heat resistance, and processability. ,
It can be said that this material is suitable as a lead material for semiconductor devices.

Margin below

Claims (1)

[Claims] 1) Cr0.05-1.0wt%, Si0.01-1.0wt%.
A copper alloy for a lead material of a semiconductor device, characterized by comprising 0 wt% of Mg, 0.01 to 1.0 wt% of Mg, and the remainder Cu and inevitable impurities. 2) Cr0.05-1.0wt%, Si0.01-1.
0wt%, Mg0.01-1.0wt% and Ni, Al
, Be, Ti, Hf, Co, and In, the total amount of one or more selected from the group consisting of 0.01 to 1.0 wt%
1. A copper alloy for lead material of semiconductor devices, characterized in that the remainder consists of Cu and unavoidable impurities.