JPS62127439A - Copper alloy for lead frame - Google Patents

Abstract

PURPOSE:To improve electric conductivity and mechanical strength of a Cu alloy for lead frames by incorporating specific amounts of Ti to a Cu-Sn alloy. CONSTITUTION:The alloy for lead frames has a composition consisting of, by weight, 0.2-2.0% Sn, 0.2-1.0% Ti, and the balance essentially Cu. If necessary, one or more kinds among 0.02-0.3% P, 0.05-0.5% Mn, 0.001-0.01% B, 0.01-0.35% Si, 0.05-0.20% Fe, and 0.02-0.20% Co are further incorporated to the above alloy. Moreover, it is preferable that oxygen content in this copper alloy is regulated to <=0.0010% and that grain size of the alloy is adjusted to <=15mum. In the above-mentioned specified compositional ranges, an intermetallic compound of Sn and Ti is dispersedly precipitated in a Cu matrix finely and uniformly, so that the effect of improving electric conductivity, strength, etc., can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application] The present invention relates to a copper alloy for lead frames, which has excellent conductivity and strength and is suitable as lead frames for semiconductor devices such as ICs and LSIs. .

[Conventional technology]

42 alloy (Fe-42%Ni), which has a small coefficient of thermal expansion and excellent sealability with ceramics and glass, has traditionally been used for lead frame materials and shite for semiconductor devices. Recently, the power consumption of ICs has increased with the progress of higher integration in LSIs and the like, so the use of copper-based materials with good heat dissipation (thermal conductivity) is increasing. Such copper-based materials include CDA194 (Cu-2,
4%Fe-0,1%Zn), Cu-0,15%Sn
Alloy, phosphor bronze (Cu-5%5n-0,1%P), Cu
-2%5n-0,2%Ni alloy, etc.

Incidentally, lead frame materials are generally required to have the following properties, including the above-mentioned thermal conductivity.

(1) Excellent thermal conductivity and electrical conductivity, (11) Relatively high strength, (iii) Good repeat bendability, Gv) High heat resistance, (■) No soldering Good adhesion properties of Jisen.

Among these required properties, electrical conductivity (thermal conductivity) and mechanical strength are particularly important.
9f/- or more is required for 50%lAC350%lAC350.

[Problem that the invention seeks to solve]

However, there are almost no currently used lead frame materials such as CDA194 that satisfy the above required characteristics. For example, CDA194 has excellent conductivity (65%lAC3)
However, the tensile strength is insufficient (45 to 9f/wl12). In addition, although phosphor bronze has sufficient strength (53KIIf/+"), its conductivity (16% lAC3) is insufficient.As a material that satisfies such requirements regarding conductivity and strength,
Precipitation hardening alloys such as Στ alloy + Cu Zr alloy are known, but they have not been widely put into practical use due to problems such as the plating property on the other side.0 This invention is required for lead frame materials. Among the above properties, especially the I
IJ-)' frame material is provided.

[Means for solving the problem J The lead frame material of this invention has Sn0.2 to 20wj
%, Ti 0.2 to 1-0 wt %, and the remainder substantially substantially Cu#x. In this invention, the above S
By uniformly and finely dispersing and precipitating an intermetallic compound of n and Ti in a Cu matrix, the above-mentioned improvements in electrical conductivity and strength can be obtained, and even better solderability can be obtained.

This material has heat resistance. Sn and Ti
The reason why the composition of is limited to the above range is that both components are 0.2
If the Sn content is less than 2.0 wt% and the Ti
If it exceeds 1.0wt%, the conductivity will decrease to 50% lA of the required value.
This is because it is significantly lower than C3, leading to deterioration in workability and solderability.

Further, in the copper alloy of the present invention, P, Mn, B or S
i is 0.02 to o, 3wt%, and 0.05 to 0.5, respectively.
wt%, 0.001-0.01wt%, 0.01
By adding it as a deoxidizing agent in the range of ~0.35 wt% during alloy melting, castability is improved, and in particular, the main component Ti is prevented from being depleted by melting, and the Ti content is reduced. can be stabilized, and the oxygen content of the alloy can be kept low. Also a trace amount of Fe or C.

(Specifically, sail05~0.2wt%, 0.02~
Addition of 0.2 wt%) has the effect of improving the strength and heat resistance of this alloy.

Further, the oxygen content in the alloy of the present invention is 0.0010wt.
% or less, the plating properties of solder and the like and the adhesion of the plating become better than when the oxygen amount exceeds this value. Further, in the alloy of the present invention, by reducing the crystal grain size to 15 μm or less, the bending workability and repeated bendability of the alloy can be further improved. The following method is optimal for reducing the crystal grain size of the alloy to the above-mentioned level. That is, Cu-8n-Ti having the composition according to the present invention
The system alloy is a precipitation hardenable alloy, and like general precipitation hardenable alloys, it is possible to cause precipitation by aging treatment after solution treatment at a high temperature. Crystal grains become coarser. Therefore, an effective method for the precipitation treatment is to perform furnace cooling (in-furnace cooling) after annealing at a relatively low temperature to cause precipitation during the slow cooling process. As a result, a fine grain size of 15 μm or less is achieved, and the appropriate annealing temperature in this case is 400 to 650°C.

[For production]

In this invention, in the specified composition range as described above, the intermetallic compound of Sn and Ti is
It is extremely uniformly and finely dispersed and precipitated in the J-socks, which is why the above-mentioned improvement in conductivity 1 strength etc. can be obtained.

[Embodiments of the invention]

Examples of the present invention will be described below.

Examples 1-10. Comparative Examples 1 to 5 Alloys having the compositions shown in Table 1 were melted using a high frequency melting furnace. Each obtained ingot was homogenized at 800°C for 5 hours, then cut into holes, and intermediate annealing and cold rolling were repeated to obtain a thickness of 0.25 + a + the conductivity of each of these example plates at a final cold working rate of 37%. The properties such as elasticity, tensile strength, repeated bendability, and solderability were measured and the results are shown in the same table.

Among these characteristics, the repeated bending property was measured using MIL-8TD-883B (load of 500 passes) using a strip of width 7m.

The test method (t = 51, 90° bending and reciprocation once) or the adhesion of solder plating was carried out by cleaning the surface of the strip specimen with 15% hydrochloric acid and placing it in a 60Sn-40Pb solder bath at 230°C for 10 minutes.
After immersion for 2 seconds, immersion in the atmosphere at 150°C for 500 hours for 20
90V for each held at 0℃ x 500hr
A bending test was conducted and evaluation was made based on the presence or absence of peeling of the plating layer. In the same table, plating adhesion was good at 150°C for 500 hours, but poor at 200°C (
Items marked with ``with cracks'' are marked Δ, 150℃, 200℃
Those with good adhesion under both conditions are marked with a circle.

The heat resistance was also evaluated by measuring the tensile strength after heating for 350'CXS in a non-nitrogen atmosphere.

In addition, except for Example 8, furnace cooling was performed after final annealing at 450°C.
After that, it was cold rolled, and Example 8 was cold worked after solution treatment at 850°C, and then subjected to aging treatment at 450°C for 1 hour.

According to the results in the same table, the Cu-8n-Ti alloy of the present invention has high conductivity 2 strength that satisfies the property levels required for lead frame materials, excellent repeated bending properties,
Adhesion and heat resistance of solder plating are obtained. In addition, as a deoxidizing agent, P is used as described above.

If Mn, B, and Si are used together, the oxygen content will be reduced, improving the soundness of the ingot, and stabilizing the Ti content by suppressing the oxidation loss of Ti, which is the main component contained, making manufacturing work easier. It is clear that the adhesion of plating such as solder, which is important when used as a lead frame, can be further improved. In Table 1, the adhesion of Examples 1 and 2 indicated by Δ did not pose any practical problems.

Also Fe, C.

The addition of a small amount of the alloy improved the heat resistance of the alloy, and in those with finer grain size (other than Example 8), a remarkable improvement in repeated bendability was observed.

[Effects of the Invention] According to the alloy of the present invention, in the Cu-8n-Ti alloy, fine intermetallic compounds consisting of KSn and Ti are uniformly dispersed in the Cu matrix, resulting in high electrical conductivity and high strength. In addition, the solderability and other properties such as plating properties, heat resistance, and moldability have been significantly improved for Tranzostar and IC.

A material suitable for lead frames of semiconductor devices such as LSIs can be provided.

Claims (4)

[Claims] (1) Sn0.2-2.0wt%, Ti0.2-1.0
A copper alloy for lead frames including wt% and the remainder substantially consisting of Cu. (2) Sn0.2-2.0wt%, Ti0.2-1.0
wt%, the remainder substantially consists of Cu, and further P0
．． 02-0.3wt%, Mn0.05-0.5wt%,
B0.001~0.01wt%, Si0.01~0.3
5wt%, Fe0.05-0.20wt% and Co0.
A copper alloy for lead frames containing one or more of 0.02 to 0.20 wt% in a total amount of 0.001 to 0.8 wt%. (3) The copper alloy for lead frames according to claim (1) or (2), wherein the copper alloy has an oxygen content of 0.0010 wt% or less. (4) Claims (1), (2), or (3), wherein the copper alloy has a crystal grain size of 15 μm or less.
Copper alloy for lead frames described in ).