JPH034612B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a copper alloy for electronic devices and a method for producing the same, and particularly relates to a copper alloy for use in electronic devices, which has particularly high strength, excellent conductivity and corrosion resistance, and
The present invention also provides a copper alloy that has good workability and plating properties, and whose interfacial strength with solder does not deteriorate over time. [Prior Art] Lead frames for electronic devices, such as semiconductors, are required to have the following characteristics. (1) High strength and good corrosion resistance. (2) High heat dissipation, that is, high thermal conductivity. (3) High electrical conductivity. (4) Good bending workability during frame forming. (5) Good plating adhesion and moldability with resin. (6) There should be no deterioration over time in the joints with solder. Conventional semiconductor lead frames are mainly made of 42 alloy (Fe-42wt%Ni alloy) (hereinafter wt% is abbreviated as %).
has been used. This alloy has a tensile strength of 63Kg/
mm ² and heat resistance of 670°C (temperature at which 70% of the initial strength is achieved by heating for 30 minutes), but the electrical conductivity is inferior to about 3% IACS. In recent years, semiconductor devices have been required to have higher reliability as well as increased integration and miniaturization, and the form of semiconductor devices is also changing from the conventional DIP type IC to the chip carrier type PGA type. For this reason, semiconductor lead frames have become thinner and smaller, and at the same time
Properties superior to those of alloys are now required. In other words, improved strength to prevent the strength of component parts from decreasing due to thinning, improved electrical conductivity, which has the same characteristics as thermal conductivity, to improve heat dissipation due to increased integration, excellent heat resistance, and improved heat resistance on the semiconductor frame. As a pretreatment for bonding from the semiconductor to the wiring at the foot of the lead frame, it improves the plating performance on the lead frame surface and the moldability with the sealing resin, and as a reliability issue, solder is used when bonding to the frame substrate. It is desired that the bonding strength does not deteriorate over time. [Problems to be solved by the invention] The above 42 alloys have a low electrical conductivity of 3% IACS and have poor heat dissipation properties.If a copper alloy is used instead, the electrical conductivity can be increased to 50-80% IACS. However, it is difficult to satisfy other properties equivalent to those of 42 alloy. [Means for Solving the Problems] In view of this, the present invention has developed a copper alloy for electronic devices that exhibits strength equal to or higher than alloy 42 and far superior conductivity, and a method for manufacturing the same. It is something. That is, the alloy of the present invention contains 0.1 to 4.8% Ni and 0.05 to 0.8% Si.
Contains Ni and Si so that the ratio of Ni and Si (Ni/Si) is 2 to 6 within the range of Zn0.05 to 0.6%,
Ca0.0005~0.3%, further Mg, B, Cr, Mn, Co,
It is characterized by containing 0.02 to 0.5% of one or more of rare earth elements, Al, Sn, and Ti individually and 0.02 to 1.0% in total, with the balance consisting of Cu and inevitable impurities. . In addition, the manufacturing method of the present invention has Ni0.1~4.8%, Si0.05~
The ratio of Ni to Si (Ni/Si) is 2 to 6 within the range of 0.8%.
Contains Ni and Si, Zn0.05~0.6%,
Ca0.0005~0.3%, further Mg, B, Cr, Mn, Co,
An alloy ingot containing one or more rare earth elements, Al, Sn, and Ti at 0.02 to 0.5% individually and 0.02 to 1.0% in total, with the remainder being Cu and unavoidable impurities, is hot worked. , followed by cold working of 80% or more, followed by heat treatment without recrystallization at 350 to 850°C for 5 seconds to 12 hours, and cold working at a working rate of 30% or less, repeated one or more times to achieve the final finish. It is characterized by the processing being less than 30%. [Function] The alloy of the present invention has the above composition, with Ni0.1 to 4.8
%, Si within the range of 0.05 to 0.8%, and containing Ni and Si so that the ratio of Ni to Si (Ni/Si) is 2 to 6, the manufacturing method of the present invention cannot be applied if each is below the lower limit. If the upper limit is exceeded, solderability will deteriorate and workability will be reduced.
In particular, it impairs hot workability and impairs manufacturability. Also
When the ratio of Ni to Si (Ni/Si) is within the above range, it exhibits sufficient strength and conductivity, and also has good plating, castability, and workability; when it deviates from this range, the above properties deteriorate significantly. Zn suppresses deterioration over time of soldering and plating joints, improves reliability, and also improves castability through its deoxidizing effect, contributing to cost reduction, but its effect is not seen below the lower limit of the above range. If the upper limit is exceeded, the conductivity decreases and workability is inhibited. Ca has a deoxidizing and desulfurizing effect, improves the soundness of the ingot and improves hot workability, and also suppresses the precipitation of Ni and Si during hot working, giving it excellent properties. If it is less than the lower limit of the above range, there is no effect, and if it exceeds the upper limit, castability and workability will be impaired and the electrical conductivity will be significantly reduced. Furthermore, Mg, B, Cr, Mn,
Any one or more of Co, rare earth elements, Al, Sn, and Ti improves strength, contributes to improving ductility, and improves formability, especially formability during bending (surface texture and dimensional accuracy). ), and also shows deoxidation and desulfurization effects, but the above range (0.02 to 0.5% alone,
Even if it is less than the lower limit (total of 0.02 to 1.0%) or exceeds the upper limit, it has no effect, lowering the electrical conductivity and deteriorating hot workability. In addition, Ba, V, Zr, Y, Fe,
A similar effect, albeit slight, is also seen in Au, Ga, In, Ge, Sb, Bi, Ag, Tl, lanthanoids, and actinides. In addition, the O ₂ content of unavoidable impurities was reduced to 40ppm.
The reason why the O ₂ content was limited to the following is that it is harmful to the uniform precipitation of Ni and Si, which are the components of the alloy of the present invention.
If it exceeds 40 ppm, coarse precipitate particles tend to form, which not only hinders the improvement of strength, but also deteriorates plating and solderability, and even deteriorates moldability, making it difficult to manufacture precision processed parts required for electronic devices. This is because it is harmful in practice. Furthermore, the size of the precipitated grains was set to 10 μm or less because the size of the precipitated grains greatly affects strength, plating properties, solderability, etc., and if the particle size exceeds 10 μm, the above characteristics deteriorate significantly. be. Among the unavoidable impurities, P forms a Ni _x P compound with Ni, resulting in excessive Si in the matrix and greatly deteriorating conductivity and solderability. Therefore, the P content should be 0.05% or less, preferably 0.03%. % or less. The alloy of the present invention has the above-mentioned structure, and can be imparted with optimum characteristics for use in electronic devices by the above-mentioned manufacturing method. In other words, after hot working, cold working of 80% or more is performed, then heat treatment without recrystallization at 350 to 850°C for 5 seconds to 12 hours, and cold working with a working rate of 30% or less are repeated one or more times. , and the final finishing rate is 30%
The following shall apply. However, if the heat treatment conditions are outside of this range, such as a recrystallized state or a partially recrystallized state, sufficient strength cannot be obtained due to coarsening of the precipitated grains due to excessive precipitation, and properties may become unstable due to the non-uniformity of the structure. Furthermore, the processing rate of cold working combined with this heat treatment was set to 30% or less because the processing rate was 30%.
%, the precipitation effect due to heat treatment and the work hardening effect will be amplified due to the introduction of dislocations due to working.
It is possible to obtain high strength, but on the other hand, it reduces ductility and greatly deteriorates manufacturability and bending formability.
For precision processed parts required for electronic equipment,
This is because it is harmful in practice. Furthermore, the final finishing rate was set to 30% or less because if the rate exceeds this, the manufacturability and bending formability due to the balance between strength and ductility deteriorate. In the present invention, hot working is started at 800 to 880°C, and after completion of the hot working, it is desirable to cool quickly in order to keep precipitated Ni, Si, etc. in a solid solution state. If it is not cold, it will not affect the characteristics in any way. Also, after the final finishing process,
By combining temper annealing at 200 to 550℃, tension leveler, tension annealing, etc.
It can have higher properties. [Example] A copper alloy having the composition shown in Table 1 was semi-continuously cast using a cooling mold, hot rolled at 850°C, and then face-faced to form a plate with a thickness of 10 mm. This was cold rolled to a thickness of 0.4 mm at a processing rate of 96%, then heat treated at 450℃ for 1 hour, further cold rolled to a thickness of 0.3mm at a processing rate of 25%, and then heated at 400℃. After heat treatment for 1 hour, final cold rolling was carried out at a processing rate of 16.7% to form a plate with a thickness of 0.25 mm, and temper annealing was further performed at 250° C. for 30 minutes. Strength, elongation, bending shape,
Solderability, corrosion resistance and plating properties were investigated. The results are shown in Table 2 in comparison with the conventional 42 alloy. The strength was measured based on JIS Z 2241, and the electrical conductivity was measured based on JIS H 0505. Bending formability was tested according to the V-block method of JIS Z 2248, and was expressed as the value R/t, which is the minimum bending radius R that causes cracks on the surface of the test piece divided by the thickness t of the test piece. Solderability was determined by cutting a sample with a width of 25 mm and a length of 25 mm, joining a 2 mm diameter oxygen-free copper wire to the 9 mm diameter section using 60/40 eutectic solder, and performing an accelerated test at 150°C for 500 hours. The joint strength was determined by a tensile test. Corrosion resistance is JIS C 8306 (stress corrosion cracking)
The time until cracking was determined using the constant load (50% of tensile strength) method in 3 vol% NH ₃ vapor. The plating property was determined using a borofusate bath with a thickness of 7.5 μm.
Sn-5%Pb alloy plating was applied, held at 105°C for 2000 hours, then bent at 180°, and peeling of the plating layer at the bent portion was examined using a microscope. Comparative examples No. 18 and 19 in Table 2 are the same alloys as the invention example No. 7 in Table 1, but comparative example No. 18 is the invention example No. 7.
In the manufacturing process of No. 7, heat treatment was performed for 2 hours at a temperature that completely softens (900°C), and in Comparative Example No. 19, cold treatment was performed before heat treatment in the manufacturing process of Invention Example No. 7. The machining rate is 93% and the final finishing rate is 50%.

【table】

【table】

〔Effect of the invention〕

As described above, the present invention has excellent strength, conductivity, bending formability, solderability, plating performance, and corrosion resistance, and can be used for lead frames, connectors, switches, etc. for electronic devices, and can be used for thinner and more compact devices. It has remarkable industrial effects such as making it possible to

Claims (1)

[Claims] 1. Ni 0.1 to 4.8 wt% and Si 0.05 to 0.8 wt% so that the ratio of Ni to Si (Ni/Si) is 2 to 6.
Contains Ni and Si, Zn0.05~0.6wt%, Ca0.0005~
0.3 wt%, and further contains 0.02 to 0.5 wt% of one or more of Mg, B, Cr, Mn, Co, rare earth elements, Al, Sn, and Ti individually, and 0.02 to 1.0 wt% in total. ,
Copper alloy for electronic devices consisting of Cu and unavoidable impurities. 2. The copper alloy for electronic devices according to claim 1, in which the content of O ₂ in inevitable impurities is limited to 40 ppm or less, and the particle size of precipitates is 10 μm or less. 3 So that the ratio of Ni to Si (Ni/Si) is 2 to 6 within the range of Ni 0.1 to 4.8 wt% and Si 0.05 to 0.8 wt%.
Contains Ni and Si, Zn0.05~0.6wt%, Ca0.0005~
0.3 wt%, and further contains 0.02 to 0.5 wt% of one or more of Mg, B, Cr, Mn, Co, rare earth elements, Al, Sn, and Ti individually, and 0.02 to 1.0 wt% in total. ,
An alloy ingot consisting of residual Cu and unavoidable impurities is hot-worked, then cold-worked to 80% or more, and then heat-treated at 350-850℃ for 5 seconds to 12 hours without recrystallization, and processing. A method for producing copper alloys for electronic devices, characterized by repeating cold working at a rate of 30% or less one or more times and making the final finishing rate 30% or less.