JPS6039142A - Copper alloy - Google Patents

Abstract

PURPOSE:To provide a Cu alloy provided with high strength and high electric conductivity and suitable for use as the material of a lead frame for a semiconductor by adding specified amounts of Sn, P, Ni and Zn to Cu. CONSTITUTION:This Cu alloy consists of, by weight, 1.7-2.5% Sn, 0.01-0.15% P, 0.1-0.6% Ni, 0.05-1% Zn and the balance Cu with inevitable impurities. In the composition, the lower limit of the Sn content is the irreducible minimu of Sn required in consideration of the effect of added Ni, and the upper limit is defined in points of cost and electric conductivity. Ni in said range refines the grains of a Cu-Sn alloy contg. said amount of Sn and exerts little influence on the electric conductivity. Zn is added by said relatively large amount so as to increase the deoxidizing effect of P and to improve the plastic workability. The Cu alloy is relatively inexpensive and has characteristics comparable to those of conventional phosphor bronze.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a copper-based alloy for electronic equipment, mainly for semiconductor lead frames.

[Prior art]

Materials for semiconductor lead frames have high conductivity, high strength, repeated bending properties, plating properties, and soldering properties.

Properties such as heat resistance and low coefficient of thermal expansion are required.

Conventionally, the mainstream material for semiconductor frames has been Fe-Mi-based 42 alloy, which has high strength and a small coefficient of thermal expansion.
Due to the trend toward lower prices, the proportion of copper-based alloys used is increasing. The ideal material properties for semiconductor lead frames include tensile strength of 50 to 9/ms+ as a guide for ideal strength, repeated bendability, and electrical conductivity.

The general required specifications are an elongation of 10 inches or more and an electrical conductivity of 50% lAC3 or more. However, there is no existing material that satisfies all of these requirements;
They are broadly divided into phosphor bronze materials, which prioritize repeated bending, and various copper-based metals, which prioritize conductivity and cost, and which are made by adding trace elements to copper.

However, conventional phosphor bronze has low conductivity (Sn
However, due to the high cost of copper, the material cost is inevitably high.On the other hand, the latter, which is made by adding trace elements to copper, has problems such as insufficient strength and repeated bendability.

[Summary of the invention]

The present invention has been made to solve the above-mentioned drawbacks, and it is possible to obtain mechanical strength and repeated bendability comparable to phosphor bronze type 1 at a cost that is 90% lower than that of phosphor bronze type 1.

Moreover, it is an excellent material for electronic devices with relatively high conductivity.
The main purpose is to provide gold materials for semiconductor lead frames.

[Embodiments of the invention]

An embodiment of the present invention will be described below. The present invention contains tin (Sn) 1.7-2.5%, phosphorus (p) o, o
It is a copper-based alloy containing t ~ 0.15 h, nickel (Ni) 0.1 to 0.6 h, and zinc (Zn) Tho, os ~ 1 h, with the balance consisting of copper and unavoidable impurities.

Next, the reason for limiting the alloy components constituting the alloy of the present invention will be explained.

As for the lower limit of Sn, the generally said tensile strength is 50
In order to obtain the ideal strength level of 10 cm or more and an elongation of 10 inches or more, we have shown the minimum required strength, taking into account the effect of Ni addition, and the upper limit is 1.7 cm from the point of view of price and conductivity.
~2.5% by weight.

Nij/(Then, the grain size of the Cu-an alloy is completely refined within the above Sn component range, hardly any influence on conductivity is observed, and the cost is low.

The content was 0.1 to 0.6% by weight.

Regarding P, set the total lower limit of the amount that provides a deoxidizing effect.

The upper limit was set at 0.01 to 0.15% by weight from the viewpoint of conductivity.

Regarding Zn, the purpose is to have an effect as a deoxidizing agent and to improve plastic workability in order to perform sufficient deoxidation for plating adhesion evaluation for lead frames. The range was O, OS to 1. As for the effect as a deoxidizing agent, it is possible to obtain very satisfactory quality by using P, but since P alone tends to have a large effect on electrical conductivity depending on its content, it is necessary to minimize the variation. Furthermore, in order to obtain high conductivity, it is necessary to keep it as low as possible within the required range.

For this reason, the addition of Zn, which has a relatively high deoxidizing effect, has almost no effect on conductivity in terms of supplementing the deoxidizing effect of P and fully controlling the depletion of P. There is.

An embodiment of the present invention will be described below.

Table 1 shows the component values of the samples prepared in the experiment.

Table 1 Samples of each composition were melted in a high-frequency induction heating furnace.

After ingot formation, cold rolling and annealing were repeated, and the final rolling reduction was set to 37 inches, resulting in a plate thickness of 0251181 mm. All samples were collected from this board and various objects were measured.

The results of mechanical properties and conductivity grain size are shown in Table 2.

[- *Method for measuring the number of repeated bends (one round trip with a 90° one-way facet is counted as one time. Sample cross-sectional area 0125 m, load 250 t) Table 2) 1 The alloy of the present invention has mechanical properties and repeated bending properties. is excellent, and the conductivity is not affected by the addition of N1 or Zn. In other words, although the number of N1 added is different for the samples with a diameter of 2° 4.5.6 or A7.8, the addition of Ni significantly improves tensile strength, hardness, and repeated bending, as well as elongation and electrical conductivity. No negative impact, such as a decline in

In addition, the crystal grain size is significantly affected by the addition of N1, and this is the main effect of improving mechanical properties, resulting in J, 0.2 electrification.
Above this level, the effect tends to be saturated.

In samples 41 to 3, no adverse effects such as mechanical properties, electrical conductivity, and crystal grain size were observed due to the addition of Zn.
The addition of n is limited to its effect as a deoxidizing agent.

The weather resistance of solder is an important property as a material for semiconductor lead frames, and as a method for evaluating this, each sample was immersed in pure 8n, 9/, and P b 8 n solder baths, and then exposed to air at 150°C. A weather resistance test was conducted for 500 hours. After weathering, each sample was subjected to a 180@adhesive bending test to check for solder peeling, but all samples were found to be good.

No trace of NiZn was observed.

In addition, sample AI, 2.3 was actually processed as a lead frame, and then partial Af plating was applied to the die part.

This was heated at 450° C. for 5 minutes and the blistering condition of the plating was investigated. As a result, A2 and 3 showed better results than sample AIK.

〔Effect of the invention〕

Based on the above results, the alloy of the present invention has a strength comparable to that of conventional phosphor bronze with relatively inexpensive ingredients, has relatively high conductivity and minimizes its variation, and is suitable for use in solder for semiconductor lead frames. It fully satisfies various reliability requirements such as weather resistance and plating blistering.

The alloy of the present invention has been described above as a material for semiconductor lead frames, but as described above, it can be said to be sufficiently useful as a material for other electrical equipment because of its high strength and high tenacity.

In addition, 1) when the alloy of the present invention is used as a general copper alloy for springs, 2) low-temperature annealing at 150°C to 450°C or Performing tension annealing is
It is an effective means as well as other materials used up until now.

Claims (1)

[Claims] 1.7-2.5% tin and 0.01-0.15% phosphorus by weight.
. A copper-based alloy containing 0.1 to 0.6% nickel and yo, os to 1 zi of zinc, with the remainder consisting of copper and unavoidable impurities.