JPS6338547A - High strength conductive copper alloy - Google Patents

Abstract

PURPOSE:To obtain a high strength conductive Cu alloy for electronic and electrical apparatus having superior characteristics such as solderability, adhesion to plating and resistance to stress corrosion cracking by reducing the O2 content in a phosphor bronze type Cu alloy with a deoxidizing agent and adding Ni, other specified element and Cr, Fe or Co to the alloy. CONSTITUTION:A Cu alloy having superior characteristics as a lead material or a spring material for electronic and electrical appliances is obtd. by adding 0.05-0.5wt% Ni, <=5wt% in total of one or more among 0.05-5% Zn, 0.01-0.5% Mn, 0.01-0.1% B, 0.01-1% Al, 0.01-0.2% Mg, 0.01-0.5% Si and 0.01-0.5% Ti and 0.05-0.5wt% at least one among Cr, Fe and Co to a phosphor bronze type Cu alloy contg. 2-8wt% Sn, <0.2wt% P and <0.0025wt% O2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high-strength conductive copper alloy suitable for lead members, spring members, etc. used in electronic and electrical equipment.

(Prior Art) Conventionally, phosphor bronze has been mainly used for connectors, various switches, electromagnetic switches, various springs, etc. used in electronic and electrical equipment.

Phosphor bronze has Sn5-9wt% (hereinafter abbreviated as Chi), Pα0
It is a copper alloy containing 3 to 35% α, and its characteristics are an
The conductivity and tensile strength can be appropriately selected according to the purpose depending on the content, and as a solid solution alloy, it has excellent moldability into precision parts.

Copper alloys for electronic and electrical equipment other than phosphor bronze include spinodal Cu-Ni-Sn alloys and Cu-Be alloys. The former has a higher tensile strength than phosphor bronze, but has a low electrical conductivity of 5 to 7% IAGS and poor workability, and the latter is very expensive, so its uses are limited.

As an improved alloy for phosphor bronze, 0.3 to 2% of Fe, Go, etc., and Cr are added to phosphor bronze for the purpose of improving hot workability.
, Zr, Ti, V, etc. added at α2 to 0.8% (Japanese Patent Application Laid-open No. 52/21211), phosphor bronze with Fef0.
There are those with 5α05 to α09% added (time opening 57 metres 894 offerings 9).

In addition, A1005-1 is applied to phosphor bronze for the purpose of improving corrosion resistance.
% added (time opening 49% 75417).

(Problems to be solved) When using phosphor bronze for various parts such as electronic and electrical equipment,
Soldering is a phenomenon in which the joint strength of parts deteriorates over time, or S
A phenomenon in which the plating film of n, 5n-Pb, etc. peels off over time is observed.

These phenomena further embrittle the ε phase, which is a compound of Cu and Sn that diffuses and concentrates at the interface between the P phosphor bronze and the solder or plating film in the phosphor bronze and forms at the interface. .

To deal with the peeling of the plating film, a method has been proposed in which a layer of Cu or N1 is interposed between the bronze and the plating film, but there are problems such as the manufacturing process becoming complicated.

Of the above, the aging phenomenon of solder joints is an issue that needs to be solved as soon as possible in the current situation where printed circuit board mounting is transitioning from through-hole mounting to high-density surface mounting in which solder connections are frequently used.

On the other hand, as designs for the efficient use of these parts progress, there is a tendency for members to be loaded with excessive stress, and NHs,
So! It is increasingly desired to develop an alloy with excellent stress corrosion cracking resistance that does not cause cracking even in a corrosive environment where , NOx, etc. are present.

To summarize the points that need to be improved in order for phosphor bronze to be used more efficiently and reliably as a component of electronic and electrical equipment, (1) deterioration of solder joints over time; (2)
Sn, 5n-Pb plating adhesion deterioration over time, (3
) Stress corrosion cracking resistance, 0) Hot workability, (5) Formability, (6) Mechanical strength, especially springiness and stress relaxation properties, (
7) Conductivity, etc.

(Means for Solving the Problems) The present invention was made in view of the above situation, and is a high-strength conductive material suitable for parts for electronic and electrical equipment having excellent solder bonding properties, plating adhesion properties, stress corrosion cracking resistance, etc. This relates to steel alloys.

That is, the present invention contains Sn 2 to 8%, P 0.2 w4 or less, 0, α0025 or less, Ni 0.05 to L5, and Zn (L 05-5m%, Mn 0.0
1-α5-ti, B0.01-0.1M%, Atα0l-
1st%, MgC101-02w1*%, S1αO1-
Contains a total of 51114% or less of one or more of α5, T1α01-0, 5%, Or, Fe,
At least one species of Go'i0.05-0.5wpt%
It is a high-strength conductive steel alloy containing copper with the remainder being copper.

In the present invention, Sn is effective in improving strength, but the reason why the content is limited to 5 to 8% is that if it is less than 3%, the tensile strength and springiness are insufficient, and if it exceeds 8%, the uniform α
This is because it becomes a solid solution, resulting in poor moldability.

P reacts with N1 to form Nls P, Nis P, N
Compounds such as 1tP are generated and finely dispersed in the steel, completely inhibiting the coarsening of crystal grains, improving hot workability, and further improving strength and strength.
Improves heat resistance and stress corrosion cracking resistance. The stoichiometric ratio of P and Ni to form the above compound is N
PO02 for il, but if P is excessive, hot workability, solder bondability, and plating adhesion will decrease.
When 1 is in excess, solid solution N1 increases and the conductivity decreases.

What is the P content here? The reason for limiting it to 0.02% or less is that 0.02% or less.
This is because if the content exceeds 2% gold, P will diffuse and concentrate at the solder or plating interface, degrading solder bonding properties and plating adhesion over time.

The reason for limiting the N1 content to 005 to L5% is that α0
This is because if it is less than 5%, the above effects cannot be obtained, and if it exceeds L5%, the electrical conductivity, moldability, solderability, and plating adhesion will decrease. The content that is particularly desirable in practice is N1 is O.
11-0.5%, P is 0.005-0.1%.

Os is contained as an impurity, but its amount is 60. .

The reason why the content is limited to 0.025% or less is that if O and OO exceed 25%, not only the molding processability will be markedly lowered, but also the solder bondability and plating adhesion will be lowered.

In addition to the above elements, Zn0.05-5%, MnO, OL
-0.5%, AE0.01-1%, Mg0.01-0
．． 2%, Bα01~0.1%, SiO,Ol~0.
5%, T10.01-0.5%, the total content of one or two or more elements is 5% or less, but these elements have a deoxidizing effect and reduce the amount of snow in the copper, making it easier to form. It improves solderability, stress corrosion cracking resistance, plating adhesion, and further contributes to increased strength. Among the above elements, B, Si, and T1 have the secondary effect of forming a compound with N1 and finely precipitating to improve both strength and conductivity, in addition to their deoxidizing effect.

The reason for limiting the content of these elements as above is that
If the content of each element is less than the lower limit, the above effects cannot be obtained, and if it exceeds the upper limit, the electrical conductivity decreases greatly in the case of Zn, the stress corrosion cracking resistance decreases, and the content of Mn,
This is because, in the case of Ae, B, Si, and T1, the conductivity decreases greatly, and in the case of Mg, the workability decreases and manufacturing becomes difficult.

Particularly desirable contents for practical use are Zn0.1-1%, Mnα
05-0.2%, Alt0.05-α2%, Mg0.0
2-0.1%, 80.03-0.08%, Si 0.
02 to 0.2%, and Ti 0.02 to 0.2%.

In addition to the above elements, at least one of Or, Fe%CO is contained in an amount of 005 to 0.5%, but Or, Fe%G
O reinforces the action of N1, and is dispersed as fine precipitates, improving strength, heat resistance, stress corrosion cracking resistance, and further improving hot workability. These contents are 0.
The reason why it is limited to 0.05 to 0.5% is that if it is less than 0.05%, the above effect cannot be obtained, and if it exceeds 0.05%, the decrease in electrical conductivity will be large and the manufacturing processability will be reduced.

Among the five elements mentioned above, Cr contributes to an improvement in strength without significantly lowering the electrical conductivity, but Fe has a relatively large decrease in conductivity, and if it exceeds 0.5%, the solderability deteriorates. Particularly desirable contents for practical use are 0.1 to 04% for Or, and 0.1 to 0.4% for F.
e and gloss are each αO75-0.5%.

The above alloy of the present invention has higher strength when compared with conventional phosphor bronze at the same Sn concentration.Therefore, at the same strength, the Sn content can be reduced by 0.5 to 2%, and the electrical conductivity is improved accordingly. do.

The alloys of the invention can be manufactured by conventional methods. That is, cut-melt, add alloying elements to it, homogenize it, make it into an ingot by water-cooling casting method, hot roll it, and then cold roll it with intermediate heat treatment as necessary to give it a predetermined size. The material is then processed into the desired material by further processing such as low-temperature annealing, tension leveling, and tension annealing.

When a thin ingot is cast by a continuous strip casting method using a graphite mold or the like, the ingot is directly cold rolled to the predetermined dimensions without hot rolling.

(Example) The present invention will be explained in detail below using examples.

The alloys listed in Table 1 were melted in a graphite crucible in air with a charcoal coating, and cast into a 150 x 30 x 300 square mold. This ingot was face-faced to remove oxide scale, then hot-rolled to Bmt at 850°C, and then α9
After cold rolling to mt, heat treatment at 600℃ for 30 minutes, further cold rolling to O-3mat, and finally 300℃
Heat treatment was performed for 15 minutes.

The tensile strength of the sample obtained in this way,
Elongation, electrical conductivity, solder joint strength, stress corrosion cracking resistance, Sn
The plating adhesion was investigated.

The solder joint strength was determined by cutting a sample 'ii'' into a 5 x 5 m chip, to which a hard copper wire of 211111φ was eutectic soldered, holding it at 150° C. for 500 hours, and then performing a pull test.

Stress corrosion cracking resistance is 5 vo according to JISCg306
A load equal to the breaking load was applied in 1% NH-vapor, and the time until cracking occurred was measured.

Sn plating adhesion was determined after degreasing and pickling the sample.
After plating 5μ of Ni and holding it at 120° C. for 1000 hours, a close bending test was performed and the bent portion was magnified 10 times with a microscope to check for peeling of the Sn plating layer.

The bath and conditions for Sn plating are 8nSOs: 100 ri/
1°H*804: 5 Of /'s β naphthol:
1 f/l, glue: 2 f/L1 bath temperature 16°C,
The current density is 2 L5A/di.

The results are shown in Table 2.

As is clear from Table 1 and Table 2, the products (1 to II) of the present invention are:
Solder joint strength compared to conventional phosphor bronze (14, 15),
Excellent stress corrosion cracking resistance and plating adhesion.

Among the comparative products, P exceeds the upper limit (8) t- is inferior in solder joint strength and plating adhesion, and N1 is less than the lower limit, so stress corrosion cracking resistance is also inferior.

O due to insufficient deoxidation! (9) exceeding the upper limit has low tensile strength and elongation, and is also poor in solder joint strength and plating adhesion. N1 or Zn exceeds the upper limit (10, 11)N
i or those in which Zn or Sl exceeds the upper limit (10 to 12
) has a large decrease in conductivity. Items with Mg exceeding the upper limit (
6) is a strong Mg 0! Due to the affinity with steel, oxides are incorporated into the steel, making it impossible to obtain a healthy ingot, resulting in low tensile strength and elongation, and poor solder joint strength and plating adhesion.

The material (6) in which Cr exceeds the upper limit is elongated and has low electrical conductivity.

Is jr6 the upper limit? Those exceeding (7) are elongated, have low conductivity, and are also inferior in solder joint strength and plating adhesion. Ni, G
.

(5) below the lower limit is inferior in solder joint strength and stress corrosion cracking resistance.

(Effects of the present invention) The alloy of the present invention has superior strength and conductivity compared to conventional phosphor bronze, does not deteriorate over time in solder bondability and plating adhesion, and has excellent stress corrosion cracking resistance. Therefore, it can be applied to lead members or spring members of electronic and electrical equipment to achieve remarkable effects.

Claims (1)

[Claims] (1) Sn2-8wt%, P0.2wt% or less, O_2
0.0025wt% or less, Ni0.05-1.5wt%
Contains Zn0.05-5wt%, Mn0.01-0
．． 5wt%, B0.01-0.1wt%, Al0.01
~1wt%, Mg0.01~0.2wt%, Si0.0
Contains a total of 5 wt% or less of one or more of 1 to 0.5 wt%, 0.01 to 0.5 wt% of Ti, and Cr, Fe.
, Co, in an amount of 0.05 to 0.5 wt%, with the remainder being copper.