JPH0331776B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) 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, connectors used in electronic and electrical equipment,
Phosphor bronze is mainly used for various switches, electromagnetic switches, and various springs. Phosphor bronze contains Sn3-9wt% (hereinafter abbreviated as %),
It is a copper alloy containing P0.03~0.35%, and its characteristics are that the conductivity and tensile strength can be appropriately selected depending on the purpose depending on the Sn content, and as a solid solution alloy, it has excellent moldability for precision parts. That's true. Copper alloys for electronic and electrical equipment other than phosphor bronze include spinodal type Cu-Ni-Sn alloys and Cu-Be
There are alloys. The former has a higher tensile strength than phosphor bronze, but has a low electrical conductivity of 5 to 7% IACS and poor workability, and the latter is very expensive, so its uses are limited. As an improved alloy for phosphor bronze, Fe, Co, etc. are added to phosphor bronze by 0.3 to 2 to improve hot workability.
%, 0.2 to 0.8% of Cr, Zn, Ti, V, etc. added (JP 52-21211), phosphor bronze with 0.5 to 1.5% of Fe,
Added 0.005 to 0.8% Zn (Special Publication 58-
35584), and phosphor bronze with 0.03 to 0.09% Zr added (Japanese Patent Application Laid-Open No. 57-89449). There is also a product in which 0.05 to 1% Ag is added to phosphor bronze for the purpose of improving corrosion resistance (Japanese Patent Laid-Open No. 49-75417). (Problems to be solved) When using phosphor bronze for various parts such as electronic and electrical equipment, there is a phenomenon that the joint strength of soldered parts deteriorates over time, or the plating film of Sn, Sn-Pb, etc. deteriorates over time. A phenomenon of peeling is observed. These phenomena occur because P in the phosphor bronze diffuses and concentrates at the interface between the phosphor bronze and the solder or plating film, further embrittling the ε phase, which is a compound of Cu and Sn, that forms at the interface. be. To deal with the peeling of the plating film, a method has been proposed in which a layer of Cu or Ni is interposed between the phosphor bronze and the plating film (Japanese Patent Publication No. 51-41222 and 49-108562), but the manufacturing process becomes complicated. There are other problems. 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. Meanwhile, as the design for efficient use of these parts progresses,
As members tend to be subjected to more excessive stress, it is increasingly desirable to develop alloys with excellent stress corrosion cracking resistance that do not crack even in corrosive environments where NH ₃ , SO ₂ , NOx, etc. are present. There is. 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, the following points can be summarized: (1) Deterioration of solder joints over time, (2) Sn and Sn-Pb plating Deterioration of adhesion over time,
(3) stress corrosion cracking resistance, (4) 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 copper alloys. That is, the present invention has Sn2 to 8%, P0.2% or less,
_O2 0.0025% or less, Mn0.01~0.5%, Cr0.05~0.5
%, containing Fe or/and Co0.05-1.5wt%,
Furthermore, Zn0.01~5wt%, B0.01~0.1wt%, Al0.01~
1wt%, Mg0.01~0.2wt%, Ti0.01~0.2wt% 1
It is a high-strength conductive copper alloy containing a total of 0.01 to 5% of one or more species, with the remainder being copper. In the present invention, Sn is effective in improving strength, but the reason for limiting its content to 2 to 8% is as follows:
If it is less than 8%, the tensile strength and springiness will be insufficient.
This is because if it exceeds %, it will be difficult to form a uniform α solid solution and the moldability will deteriorate. P is Fe or Co and Fe ₃ P, Fe ₂ P, FeP, Co ₂ P,
Compounds such as CoP and CoP ₃ are generated and finely distributed,
It prevents coarsening of crystal grains, improves hot workability, and further improves strength, heat resistance, and stress corrosion cracking resistance. The reason for limiting the P content to 0.2% or less is 0.2
%, P will diffuse and concentrate at the solder or plating interface, reducing solder bondability and plating adhesion, and is also harmful to hot workability. The content of P is preferably 0.0005 to 0.08%, which is equal to or lower than the stoichiometric amount of Fe and/or Co. The reason for limiting the content of Fe and/or Co to 0.05 to 1.5% is that if it is less than 0.05%, the action and effect with the above P will be insufficient, and if it exceeds 1.5%, the decrease in conductivity will be large and the manufacturing processability will be reduced. This is because the solder bondability and plating adhesion deteriorate. O ₂ is contained as an impurity, but the amount
The reason why it is limited to 0.0025% or less is that if it exceeds 0.0025%, not only will the moldability deteriorate significantly, but
This is because solder jointability and plating adhesion deteriorate. Mn has a deoxidizing effect and works to reduce the amount of _O2 . The reason why the content is limited to 0.01 to 0.5% is that less than 0.01% is insufficient to reduce O ₂ to 0.0025% or less, and more than 0.5% causes a significant decrease in electrical conductivity. Zn0.01~5%, B0.01~0.1%, Al0.01~1%,
One or more of Mg0.01~0.2% and Ti0.01~0.2% are contained in a total of 5% or less, but these elements reinforce the effects of Mn and improve moldability, solderability, and metallization. Improves adhesion. The reason for limiting the content of each element 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 conductivity will decrease significantly and the manufacturing processability will be reduced. This is because the amount decreases. The reason why the total amount of two or more of these elements is limited to 5% or less is that if it exceeds 5%, the electrical conductivity will decrease significantly and the manufacturing processability will decrease. The particularly desirable content of these elements is Zn0.1~1
%, B0.03~0.08%, Al0.05~0.2%, Mg0.02~
0.07%, Ti 0.02-0.1%. Cr improves hot workability, strength, heat resistance and stress corrosion cracking resistance. Cr is more effective than Fe or Co because the amount of solid solution in Cu is smaller. here
The reason for limiting the Cr content to 0.05-0.5% is 0.05%.
If it is less than 0.5%, the above effect cannot be obtained, and if it exceeds 0.5%, the precipitates become coarse and hot workability deteriorates. A particularly desirable Cr content is 0.15-0.4%. The 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 can be improved accordingly. The alloys of the invention can be manufactured by conventional methods. That is, after melting Cu and adding alloying elements to it and homogenizing it, a water-cooled casting method is used to form an ingot, which is then hot-rolled, and then cold-rolled with intermediate heat treatment as necessary to form a predetermined size. The material is then processed into a desired material through low-temperature annealing, tension leveling, tension annealing, etc. When a thin ingot is cast by a continuous strip casting method using a graphite mold or the like, it is directly cold-rolled to a predetermined size without hot rolling. (Examples) The present invention will be explained in detail below using examples. The alloys shown in Table 1 were melted in a graphite crucible in the atmosphere with a charcoal coating, and cast into a mold of 150 x 30 x 300 mm. This ingot was faceted to remove oxide scale, then hot rolled at 850°C to a thickness of 8mm, then cold rolled to a thickness of 0.9mm, heat treated at 600°C for 30 minutes, and further 0.3mm thick. Cold rolled until thick and finally
Heat treatment was performed at 300°C for 15 minutes. The tensile strength, elongation, electrical conductivity, solder joint strength, stress corrosion cracking resistance, and Sn plating adhesion of the samples thus obtained were investigated. The solder joint strength was determined by cutting a sample into a 5 x 5 mm chip, eutectic soldering a hard copper wire with a diameter of 2 mm to the chip, holding the chip at 150°C for 500 hours, and performing a post-pull test. Stress corrosion cracking resistance is 3Vol% according to JISC8306
The time until cracking was measured by applying a load of 1/2 of the breaking load in NH ₃ vapor. Sn plating adhesion was determined by degreasing and pickling the sample, plating it with 5 μm of Sn, holding it at 120℃ for 1000 hours, performing an adhesion bending test, magnifying the bent part 10 times with a microscope, and measuring the Sn plating layer. The presence or absence of peeling was examined. The bath and conditions for Sn plating are SnSO ₄ : 100g/
, H ₂ SO ₄ : 50g/, β-naphthol: 1g/
, Glue: 2g/, Bath temperature 16℃, Current density:
It is 1.5A/ ^dm2 . The results are shown in Table 2.

【table】

【table】

[Table] As is clear from Table 2, the products of the present invention (2 to 5)
has better solder joint strength than conventional phosphor bronze (14, 15),
Excellent stress corrosion cracking resistance and plating adhesion.
(2, 4, 5) have even higher tensile strength. Among the comparative products, the one (6) in which P exceeds the upper limit is inferior in solder joint strength, stress corrosion cracking resistance, and plating adhesion. Items with Mn, Fe or Co exceeding the upper limit (8~
10) has a large decrease in conductivity. Those with Zn above the upper limit and Fe and Co below the lower limit (11) have poor electrical conductivity and stress corrosion cracking resistance. Mg
In the case of exceeding the upper limit (12), Mg's strong affinity with O ₂ causes oxides to be incorporated into the copper, making it impossible to obtain a sound ingot, resulting in low tensile strength and elongation, and poor solder joint strength and plating. Poor adhesion. In the case where Cr exceeds the upper limit (13), the conductivity decreases significantly. (Effects of the 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. It produces remarkable effects when applied to lead members or spring members of electronic and electrical equipment.

Claims (1)

[Claims] 1 Sn2~8wt%, P0.2wt% or less, O ₂ 0.0025wt%
Below, Mn0.01~0.5wt%, Cr0.05~0.5wt%, Fe
or/and contains Co0.05-1.5wt%, and further
Zn0.01~5wt%, B0.01~0.1wt%, Al0.01~1wt
%, Mg 0.01 to 0.2 wt %, and Ti 0.01 to 0.2 wt %, in a total of 0.01 to 5 wt %, and the balance is copper.