JPS60218440A - Copper alloy for lead frame - Google Patents

Abstract

PURPOSE:To obtain a Cu alloy for a lead frame having superior strength, electric conductivity, heat resistance and workability by adding specified amounts of Ti and one or more among Sb, Ag, Te, Si, Cr, Co, Fe, P, Sn, Mg, Zr, Al, Mn, Be and Ni to Cu. CONSTITUTION:The composition of a Cu alloy for a lead frame is composed of 0.05-2wt% Ti, <3wt% one or more among Sb, Ag, Te, SI, Cr, Co, Fe, P, Sn, Mg, Zr, Al, Mn, Be and Ni as the 3rd element and the balance Cu. Cu is melted in a graphite crucible, Ti is added, and then the 3rd element is added to manufacture said Cu alloy.

Description

Detailed Description of the Invention The present invention has high strength, excellent conductivity and heat resistance, and has excellent workability as a copper alloy. ) This relates to a copper alloy for lead frames with excellent properties.

BACKGROUND ART In recent years, semiconductor integrated circuits have become more highly integrated and smaller, and at the same time are required to have high reliability.

Furthermore, the form of semiconductor integrated circuits is also changing from the conventional DIP type IC to chip carrier type, PGA type, etc. For this reason, the materials used for the lead frames of these integrated circuits have become thinner and smaller, and at the same time, the materials are required to have excellent properties, and the Fe-Ni There was an urgent need to improve the material, 112 alloy. That is, the first characteristic is an improvement in the strength of the material, which prevents the strength of its constituent parts from decreasing as the material becomes thinner. The second property is an improvement in heat dissipation caused by an increase in the degree of integration, that is, an improvement in electrical conductivity, which is the same property as thermal conduction. The fifth characteristic is heat resistance, and the fourth characteristic is pretreatment for bonding the gold wire used when fixing the semiconductor on the frame and for wiring from the semiconductor to the leg part of the lead frame. is the adhesion of plating to the surface of the lead frame during plating treatment.

The above characteristics are the properties found in the material. Currently, the 42 alloy mainly used has an electrical conductivity of approximately 5% lAC.
3, which is a major drawback in terms of heat dissipation.
Improvements are desired.

However, if this is replaced with a copper alloy, the electrical conductivity will dramatically improve from the aforementioned 3% to 50-70% lAC3, but it will not be able to satisfy the strength of 112 alloy, which is 50-70 kg/-. This characteristic could only be achieved by subjecting some Cu alloys to a heat treatment of quenching and tempering.

In view of these circumstances, as a result of various experimental studies, the present invention has been developed to produce a material that does not require the expensive "quenching-tempering" process, and has a strength comparable to that of l12 alloy. In addition, we have developed a copper alloy for use in lead frames that has good electrical conductivity, and has a Ti content of 005 to 2. ．． 0wt
% (hereinafter abbreviated as ``chi''), and further contains SbXAg, Te, Si, Or, and Go as tertiary elements.

FeXP, Sn, Mg, Zr, Ail, Mn,
It is characterized in that one or more of Be and Ni is added in an amount of 3 or less by autopsy, and the remainder consists of cu.

When Cu IICTi is added, a 0u-Ti compound is formed (precipitated in Eu). These precipitations are generally performed by solution treatment at high temperatures and aging treatment after quenching to improve strength and at the same time increase electrical conductivity. During solution treatment, Ti dissolved in Cu and the temporary decrease recovered.
Although properties having both strength and electrical conductivity can be obtained, in the present invention, Cu is generally treated without solution treatment and temporary quenching treatment.
The properties are ensured through the process of manufacturing the alloy, that is, by repeating hot working, cold working, and annealing to obtain the final product. After hot working the alloy of the present invention, annealing is performed at 500°C.
When carried out at ~700°C for 1 hour, Ti dissolved in Cu precipitates in the form of Cu-Ti, Cu-Ti-X, or Ti-X (X is the third element of the alloy of the present invention). Although the strengthening effect caused by these precipitates is somewhat weaker than that in temporary hardening treatment, the strengthening effect of 0u-Ti-X, Ti-X precipitates is stronger than that in temporary hardening treatment of Cu-Ti. We have discovered that it is not only possible to compensate for this, but also to have an effect that outweighs it.

In addition, in the case of Gu-Ti, the electrical conductivity is T with respect to Cu.
Since the solid solubility of 1 is relatively large, even if Cu-Ti is completely precipitated, the electrical conductivity is 2.0% Ti and 30% lA.
By adding the third additive element of the present invention to C3, Gu-Ti-X and Ti-X are precipitated, and the electrical conductivity is significantly improved.

Next, heat resistance is one of the important properties required of lead frame materials. The heat resistance of lead frame material is generally l1
00°C to 500°C is sufficient. This is (3u IIC
This value can already be cleared if Ti is added. However, when the T1 addition of the present invention falls within the range of 07 to 20 inches, the heat resistance of the 0u-Ti alloy becomes 650° C. or higher, which increases the annealing temperature when producing this alloy and deteriorates energy efficiency. As the third element, X (= Sb, Ag
, Te, etc.) to increase the annealing temperature to 500~
It is possible to lower the temperature to 650°C, and it is also possible to sufficiently secure four-thermal properties as a lead frame material.

In addition, the plating adhesion (solderability) required for lead frame materials is 100~2 after applying Ag, Sn, 5n-Pb (solder) to the copper alloy base material by plating or dipping.
Adhesion is good when a slight interdiffusion layer is formed between the plating element and the base material when kept at 00°C for a long period of time, but if the diffusion progresses further, the elements in the base material will spread to the plating surface. This leads to a deterioration in the bonding properties of the Au wire that connects the semiconductor and the lead frame during the manufacture of integrated circuit components. On the other hand, the interdiffusion layer is thick, and at the same time, T1, which is a solid solution in Cu in 0u-Ti alloys, diffuses into this layer, forming brittle compounds with Sn and Ag in the plating and soldering. This may cause peeling. To prevent this, Cu-T
i If the solid solution of T1 in the base material is made into precipitates and fixed as much as possible, the diffusion of T1 will be reduced and the releasability will be reduced.

In the alloy of the present invention, if only Cu-Ti is used, T1 is considerably dissolved in solid solution, but the fifth element Sb, Ag, Te, Si
, Or.

C01Fe%Ps "0% Mgz Zr %' jV
! -, Mn, Be, Nl by adding T1
This makes it possible to create a compound with and fix it, thereby reducing the influence of T1, which causes diffusion layer embrittlement.

However, the reason why the composition of the alloy of the present invention is limited as mentioned above is that if T1 is less than 0.05 mm, it is ineffective, and if T1 exceeds 20 mm, castability and workability are poor, making it difficult to manufacture. This is because if it exceeds %, it becomes difficult to manufacture.

The present invention will be described in detail below using examples.

Copper was melted using a graphite crucible, the surface of the hot water was covered with charcoal powder, and after sufficient melting, Ti was added, and the various elements mentioned above were added to make a width of 150 mm.
The ingot was 200 mm long and 25 mm thick. Next, the surface of the ingot was milled by 2.5 mm per surface, and then hot rolled to produce a plate with a thickness of 8 mm and a width of 150 mm. Thereafter, annealing and rolling were repeated to obtain a plate having a final thickness of 025 mm. Note that the finishing rate after intermediate annealing was 40%.

Based on the sample material thus obtained, electrical conductivity, tensile strength, heat resistance, and plating adhesion were measured. These results are shown in Table 1.

As is clear from Table 1, the alloy of the present invention is a copper alloy for lead frames that has the same strength and plating adhesion as the conventional L2 alloy, and has significantly superior electrical conductivity. .

On the other hand, comparative alloy Nα2 with no third element added
0. Comparative alloy Ugly 2 with less Ti and no fifth element added
It can be seen that No. 1 is inferior in plating adhesion or strength.

As mentioned above, the alloy of the present invention has good electrical conductivity, tensile strength,
This copper alloy for lead frames has excellent plating adhesion and heat resistance, and has remarkable effects in the electronics industry.

Claims (1)

[Claims] T1 is 005 to 2. Contains Owt% and further contains SbXAg, Te, Si, Or, co, F as a fifth element.
e, P, Sn, Mg, Zr, U. A copper alloy for lead frames, characterized in that one or more of Mn, Be, and 'Ni are added in a total amount of 54 Pwt% or less, and the balance is Cu.