JP3445432B2 - Copper alloy for electronic equipment with excellent solder wettability and Ag plating resistance to heat swelling - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy having excellent surface properties such as solder wettability and resistance to heat swelling by Ag plating and also excellent mechanical and physical properties, and particularly semiconductor lead frames, terminals and connectors. It is a copper alloy suitable for electronic equipment members such as.

[0002]

2. Description of the Related Art As described above, semiconductor lead frames, connectors and the like have excellent mechanical properties such as strength and heat resistance, and physical properties such as electrical and thermal conductivity, and tin or solder plating. There is a demand for a copper alloy having excellent surface characteristics such as heat-resistant peelability and solder wettability. In recent years, Cu-Ni-Si alloys of high strength and medium conductivity type, which have been known for a long time, are used as semiconductor
It has come to be used for electronic equipment members such as dframes. Cu-Ni-Si alloys are precipitation-strengthened copper alloys that use Ni-Si compounds as precipitates and have excellent mechanical and physical properties, but have the fatal drawback of poor wettability with solder. Also, it becomes important when used for lead frames, etc.
It is known that the Ag plating resistance to heat swelling is also poor. The Cu-Ni-Si-based alloy is, similarly to a normal precipitation-strengthened copper alloy, hot and cold rolled ingots, is subjected to solution treatment, aging treatment, etc., is manufactured, Wettability and Ag
It was thought that the cause of poor surface properties such as plating heat swelling resistance was the copper oxide film formed during heat treatment such as solution treatment. From this, as a method of improving the solder wettability of Cu-Ni-Si-based alloy, a method in which the heat treatment atmosphere is extremely limited to a non-oxidizing or reducing atmosphere and a copper oxide film is not formed, or A method has been adopted in which the oxide film is ground or melted and removed during manufacture.

[0003]

However, the method of limiting and controlling the heat treatment atmosphere is disadvantageous in terms of cost, and the method of removing the oxide film has a surface such as solder wettability and Ag plating heat swelling resistance. The characteristics were not sufficiently improved.
The present inventors investigated the cause that the surface characteristics are not improved even if the oxide film is removed. As a result, the Ni and Si do not actually precipitate all of the added material, and some remain in the state of solid solution in the Cu matrix, and some of this solid solution Si is solutionized during the manufacturing process. It has been found that when various heat treatments such as aging and annealing become oxides, which become coarse and exist in the surface layer, surface properties such as solder wettability and Ag plating heat swelling resistance deteriorate. Then, as a remedy for this, research has been conducted on a method of preventing the formation of Si oxide or removing the coarse Si oxide on the surface layer, thereby completing the present invention. INDUSTRIAL APPLICABILITY The present invention is a Cu-based alloy that has high mechanical and physical properties, excellent surface characteristics, and can be manufactured at low cost.
The purpose is to provide a Ni-Si based copper alloy for electronic devices.

[0004]

The invention according to claim 1 is
0.4～4.0Wt% of Ni, comprises 0.1-1.0% of Si, the balance being Cu
And the inevitable impurities, and the size of the Si oxide existing in the surface layer with a depth of 1 μm from the surface is 0.1 μm or less. Solder wettability and Ag plating heat resistance.
It is a copper alloy for electronic devices with excellent swelling properties .

According to the second aspect of the invention, 0.4 to 4.0 wt% of N
i, Si oxide containing 0.1 to 1.0 wt% of Si, containing an element more stable as an oxide than metallic Si, the balance consisting of Cu and inevitable impurities, and present in the surface layer at a depth of 1 μm from the surface Solder characterized by a size of 0.1 μm or less
It is a copper alloy for electronic devices, which has excellent wettability and resistance to heat swelling by Ag plating .

According to the third aspect of the invention, 0.4 to 4.0 wt% of N
i, comprises 0.1-1.0% of Si, further 0.005～0.3Wt% of A
l, 0.005 to 0.2 wt% Ti, 0.005 to 0.5 wt% Mg, and one or more selected from 0.005 to 0.5 wt% in total,
The balance is Cu and unavoidable impurities, and the size of Si oxide existing in the surface layer with a depth of 1 μm from the surface is 0.1 μm.
Solder wettability and Ag characteristics characterized by
It is a copper alloy for electronic devices that has excellent resistance to heat swelling .

The invention according to claim 4 is such that 0.4 to 4.0 wt% of N
i, comprises 0.1-1.0% of Si, further 0.005～0.3Wt% of A
l, 0.005 to 0.2 wt% Ti, 0.005 to 0.5 wt% Mg, and one or more selected from 0.005 to 0.5 wt% in total,
0.001 to 0.1 wt% P, 0.05 to 1.0 wt% Zn as sub-components,
Either 0.01 to 0.5 wt% Mn or 0.005 to 0.1 wt% Ag 1
Includes 0.005 to 2.0 wt% in total of two or more species, with the balance being
Solder wettability and Ag plating resistance characterized by the fact that the size of the Si oxide existing in the surface layer with a depth of 1 μm from the surface is 0.1 μm or less, which consists of Cu and inevitable impurities.
It is a copper alloy for electronic devices with excellent heat swelling properties .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, Ni and Si are elements that are precipitated as a Ni-Si compound (Ni ₂ Si phase) in a Cu matrix to improve the strength without lowering the conductivity. In the present invention, the reason for defining Ni to 0.4 to 4.0 wt% and Si to 0.1 to 1.0 wt% is that Ni is less than 0.4 wt% and Si is less than 0.1 wt%. Strength is not obtained, and even if Ni exceeds 4.0 wt% or Si exceeds 1.0 wt%, precipitates that do not contribute to strength improvement occur during casting or hot working, and strength commensurate with the amount added. This is because it is not obtained, and the hot workability and bending workability are also adversely affected.

In the present invention, the reason why the size of the Si oxide existing in the surface layer with a depth of 1 μm from the surface is specified to be 0.1 μm or less is that the size of the Si oxide exceeds 0.1 μm and the solder wets. This is because surface properties such as heat resistance and heat swelling resistance of Ag plating deteriorate. The Si oxide formed near the surface of the sample by heat treatment becomes larger as it approaches the surface and smaller as it gets inside. Therefore, when the Si oxide in the vicinity of the sample surface exceeds 0.1 μm, the surface characteristics are improved by removing the surface layer until the size of the Si oxide becomes 0.1 μm or less. For removing the surface layer, any method such as grinding, buffing, and chemical dissolution (pickling) can be applied.

In the second aspect of the invention, the reason for adding the element more stable as an oxide than Si is that the element becomes an oxide and traps oxygen by heat treatment during the manufacturing process.
This is to prevent generation or coarsening of Si oxide. According to this method, the removal of the copper alloy surface layer can be reduced or omitted.

Examples of elements that are more stable as oxides than Si include Al, Ti and Mg. In the invention of claim 3, the reason for defining Al to be 0.005 to 0.3 wt% is that Al is 0.1%.
This is because if it is less than 005 wt%, generation or coarsening of Si oxide cannot be prevented, and if it exceeds 0.3 wt%, the conductivity is significantly reduced and the solder wettability is also reduced.

The reason for defining Ti to 0.005 to 0.2 wt% is that Ti is
Is less than 0.005 wt% it is not possible to prevent the formation or coarsening of Si oxide, and if more than 0.2 wt% causes a significant decrease in conductivity,
This is because the surface characteristics also deteriorate. Ti is a solid solution Ni that prevents the formation or coarsening of Si oxide and also deteriorates the surface characteristics.
And Si are deposited as Ti-Ni compounds or Ti-Si compounds to render them harmless. However, if Ti is added in excess of 0.2 wt%,
In some cases, a large amount of Ti-Ni compound, etc. precipitates and the important Ni-Si compound decreases, resulting in a decrease in strength.

The reason why Mg is specified to be 0.01 to 0.5 wt% is that Mg is
This is because if it is less than 0.01 wt%, generation or coarsening of Si oxide cannot be prevented, and if it exceeds 0.5 wt%, the conductivity is significantly reduced and the surface characteristics are also degraded. In addition, Mg also has the effect of improving hot workability. The added amounts of Al, Ti, and Mg are individually adjusted according to the required performance. If the total amount of Al, Ti, and Mg added at the same time is less than 0.005wt%, the solder wettability is not improved, and if it exceeds 0.5wt%, not only the conductivity decreases significantly, but also the surface characteristics. Also gets worse. Therefore, the total amount is defined as 0.005-0.5 wt%.

Next, P, Zn, Mn, and Ag, which are auxiliary components added in the invention of claim 4, will be described. P has the effect of reducing the solid solution amount of Ni and Si in the Cu matrix. That is, P increases the precipitation amount of Ni-Si compound and improves the strength and the conductivity. In addition, P has the function of trapping oxygen and suppressing the formation of Si oxide. 0.001 to 0.1 wt% P
The reason is as follows: If P is less than 0.001 wt%, the effect cannot be obtained sufficiently, and if it exceeds 0.1 wt%, the hot workability deteriorates.
Also, the heat-resistant peelability of tin or solder plating is reduced.

Zn improves the thermal peel resistance of tin or solder plating. However, the mechanism is not clear. Zn is 0.0
If it is less than 5 wt%, the desired effect cannot be obtained, and if it exceeds 1.0 wt%, the effect is saturated and the solder wettability is deteriorated.
Therefore, Zn is specified to be 0.05 to 1.0 wt%.

Mn is a solid solution present in Cu at the impurity level.
Takes in S and suppresses deterioration of hot workability due to S. Mn
Is less than 0.01 wt%, the effect is not sufficiently obtained, and 0.5 wt%
If it exceeds, the electrical conductivity is significantly reduced and the solder wettability is also reduced. Therefore, Mn is specified to be 0.01 to 0.5 wt%.

Ag improves strength and heat resistance. Ag is 0.00
If it is less than 5 wt%, the effect cannot be sufficiently obtained, and if it exceeds 0.1 wt%, it is disadvantageous in cost. Therefore, Ag is 0.005-0.1wt%
Stipulated in. When adding two or more of the above-mentioned sub-component elements, the total amount should be 0.005 to 2.0w in consideration of solder wettability, Ag plating heat swelling resistance, heat peeling resistance of tin or solder plating, conductivity, etc.
Specified as t%.

[0018]

EXAMPLES The present invention will be described in detail below with reference to examples. The alloy having the composition shown in Table 1 is melted in a high frequency melting furnace,
Then, it was cast into an ingot having a thickness of 50 mm and a width of 120 mm. This ingot was subjected to reheat solution treatment at 950 ° C. for 1 hour, and then hot rolled to a thickness of 11 mm. After hot rolling, the surface was ground to remove oxide scale produced during hot rolling, and then cold rolled to a thickness of 0.3 mm. After cold rolling, some samples were subjected to an intermediate solution treatment (heating at 800 ° C for 60 seconds and then water quenching) using a continuous annealing furnace. Next, 300-600 for all the samples that have been subjected to the intermediate solution treatment and those that have just been cold rolled.
Heat treatment is performed by heating at ℃ for 1 to 6 hours, and after heat treatment, 0.
It was cold-rolled to a thickness of 25 mm and then tempered by low temperature annealing to obtain a product. The surface of some of the products after conditioning was removed by polishing the surface.

The resulting product was measured for tensile strength, conductivity, solder wettability, and resistance to heat swelling by Ag plating. The results are shown in Table 1 together with the alloy composition and manufacturing conditions. still,
Tensile strength was measured according to JIS-Z2241, and conductivity was measured according to JIS-H0505. Solder wettability is 10mm wide, 50mm long after electrolytic degreasing, pickling with 10% H ₂ SO ₄ and pre-treatment with flux such as rosin.
The mm test piece was immersed in a eutectic solder bath at 230 ° C., and the wet state was visually observed. Ag plating heat swelling resistance is, after electrolytic degreasing, pickled with 10% H ₂ SO ₄ , then subjected to Ag plating, heated in air at 450 ° C for 10 minutes, and then checked for swelling with a microscope. It was observed at 20 times magnification. Further, the size of the Si oxide existing in the surface layer having a depth of 1 μm from the surface was observed using a transmission electron microscope (TEM). 20,000 to 10
The diameter of the shortest part of the largest Si oxide in the field of view observed at 10,000 times was defined as the size of the Si oxide.

[0020]

[Table 1]

As is clear from Table 1, the products of the present invention (No. 1)
All of 11 to 11) showed excellent properties in solder wettability and Ag plating heat swelling resistance. In the case where the element whose oxide is more stable than that of metallic Si was added, the Si oxide was small even if the number of times of surface polishing was once or less. In addition, N with the addition of Zn
o.6,9,10,11 had excellent heat-resistant peeling property of solder plating. Further, Nos. 6, 10, and 11 in which Mn was added in addition to Zn were excellent in hot workability, and No. 9 in which Ag was added was excellent in tensile strength and heat resistance. No. 8 with P added has improved tensile strength and conductivity compared to No. 4 without P. still,
The low conductivity of No. 11 is due to the manufacturing process including the intermediate solution treatment.

On the other hand, the comparative sample No. 12 had no surface polishing, and the sample No. 13 had only one surface polishing.
The size of the Si oxide in the surface layer of the product (layer from the surface to a depth of 1 μm) both exceeded 0.1 μm. As a result, the surface properties (solder wettability and heat swelling resistance to Ag plating) were poor. Since No. 14 was subjected to intermediate solution treatment, even if the surface was polished twice, Si oxides exceeding 0.1 μm remained on the surface layer of the product and the surface characteristics were poor. Since No. 15 contained Ni and Si in amounts exceeding the limits of the present invention, cracking occurred during hot rolling and normal production could not be performed. In No. 16, the addition amount of Al, which is an element whose oxide is more stable than that of metallic Si, was small, and since the surface was not polished, the Si oxide in the surface layer exceeded 0.1 μm and the surface characteristics were not improved. No.17,18,19 contains Al or Mg, which is an element whose oxide is more stable than metallic Si, so the size of Si oxide on the product surface layer is 0.1 μm without surface polishing.
The following was obtained, and the heat swelling resistance of Ag plating was improved. However, since the addition amount of Al, Mg, or Zn as a subcomponent was too large, the solder wettability and the conductivity were all decreased. Since No. 20 contained P in an amount exceeding the regulation of the present invention, cracking occurred during hot rolling, and the product could not be manufactured normally.
In No. 21, the additive element other than Ni and Si is an element (Fe) whose oxide is more unstable than Si, so the formation or coarsening of Si oxide is not prevented, and the surface characteristics are the same as No. 12. Fell.

Structure photographs of the vicinity of the product surface by a transmission electron microscope are shown in FIGS. 1A and 1B are the No. 3 and No. 4 microstructures of the product of the present invention, respectively, and the white elongated shape near the center is the Si oxide, and the size (diameter of the short portion) is 0.03 in each case. It is as small as ~ 0.04μm. On the other hand, FIG. 1C shows the No. 13 structure of the comparative example product, and the Si oxide is large at about 0.14 μm.

[0024]

As described above, the copper alloy for electronic devices of the present invention has a high degree of mechanical and physical properties, and has a Si oxide with a size of more than 0.1 μm, which impairs surface characteristics. Since it does not exist in the surface layer, it has excellent surface characteristics, and since it does not require heat treatment in a non-oxidizing atmosphere, it can be manufactured at low cost.
Therefore, it has a remarkable industrial effect.

[Brief description of drawings]

FIG. 1 is a transmission electron micrograph of a Cu—Ni—Si-based copper alloy surface layer.

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C22C 9/06 H01L 23/48

Claims (4)

(57) [Claims] 1. 0.4 to 4.0 wt% Ni, 0.1 to 1.0 wt% Si
Wherein the remainder being Cu and unavoidable impurities, 1 from the surface
The size of Si oxide existing in the surface layer with a depth of up to μm
Solder wettability characterized by being 0.1 μm or less and
Copper alloy for electronic equipment with excellent Ag plating resistance to heat swelling . 2. 0.4 to 4.0 wt% Ni, 0.1 to 1.0 wt% Si
Containing an element that is more stable as an oxide than metallic Si, the balance consisting of Cu and unavoidable impurities, and the size of the Si oxide existing in the surface layer at a depth of 1 μm from the surface is 0.1 μm or less. Solderability and Ag plating characterized by
Copper alloy for electronic devices with excellent resistance to heat swelling . 3. 0.4 to 4.0 wt% Ni, 0.1 to 1.0 wt% Si
In addition, 0.005-0.3wt% Al, 0.005-0.2wt% Ti,
It contains 0.005 to 0.5 wt% in total of one or more selected from 0.005 to 0.5 wt% Mg, the balance consisting of Cu and unavoidable impurities, and exists in the surface layer with a depth of 1 μm from the surface. A copper alloy for electronic devices , which is excellent in solder wettability and resistance to heat swelling by Ag plating , characterized in that the size of Si oxide is 0.1 μm or less. 4. 0.4 to 4.0 wt% Ni, 0.1 to 1.0 wt% Si
In addition, 0.005-0.3wt% Al, 0.005-0.2wt% Ti,
It contains 0.005 to 0.5 wt% in total of one or more selected from 0.005 to 0.5 wt% Mg, and 0.001 to 0.
1wt% P, 0.05-1.0wt% Zn, 0.01-0.5wt% Mn, 0.0
05-0.1wt% Ag, one or more in total
Comprises 0.005～2.0Wt%, half the remainder being Cu and unavoidable impurities, the size of the Si oxides present from the surface to the surface layer of depth to 1μm is characterized in that it is 0.1μm or less
A copper alloy for electronic devices that has excellent wettability and resistance to heat swelling on Ag plating .