JPH11323463A - Copper alloy for electrical and electronic parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Cu-Cr-Mg alloy for electrical and electronic parts, excellent in Ag platability and etching processability as well as in press blankability (minimal burr height). SOLUTION: The steel has a composition consisting of, by weight, 0.05-0.6% Cr, 0.05-1.0% Mg, 0.0003-0.02% C, 0.0003-0.005% S, 0.00001-0.001% Se, and the balance Cu with inevitable impurities and further containing, if necessary, 0.05-5.0% Zn or/and 0.05-2.0% Sn. It is desirable that crystal grain size at final sheet thickness is regulated to <=30 μm and that the number of Cr precipitates having <=0.1 μm grain size comprises >=98% of that of the whole Cr precipitates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a copper alloy for electric / electronic parts. More specifically, the present invention relates to a copper alloy for electric / electronic parts such as lead frames and terminals having high strength and high conductivity, and particularly excellent in stamping property, Ag plating property and the like.

[0002]

2. Description of the Related Art Conventionally, Cu--Cr--Mg alloys have been known as high-strength, high-conductivity copper alloys for electric and electronic parts (JP-A-62-130247, JP-A-6-130247).
3-109130, JP-A-4-21733, JP-A-8-13066 and the like). This Cu-
The Cr-Mg-based alloy has improved strength while maintaining high electrical conductivity, as compared with Cu-Cr-based alloys and Cu-Mg-based alloys.

[0003]

SUMMARY OF THE INVENTION This Cu-Cr-Mg
System alloy is stamped at high speed (press punching)
Then, it is formed into an electric or electronic component such as a lead frame, but there is a problem that a burr height is large at the time of stamping. Also, Ag plating properties are poor (protrusions are formed) due to the crystallization of Cr generated at the time of casting. Further, when the lead frame is formed by etching, the lead after etching is short-circuited. is there. Accordingly, an object of the present invention is to provide high strength, high conductivity, and exhibit bending workability and solder heat-resistant peeling properties, which are basic properties as alloys for electric / electronic parts, and furthermore, press punching. Cu (excellent in burr height) with excellent Ag plating and etching processability
-To provide a Cr-Mg based alloy.

[0004]

The copper alloy for electric / electronic parts according to the present invention comprises: Cr: 0.05 to 0.6% by weight;
g: 0.05 to 1.0% by weight, C: 0.000%
3 to 0.02% by weight, S: 0.0003 to 0.005% by weight, Se: 0.00001 to 0.001% by weight, the balance being Cu and unavoidable impurities. This copper alloy further contains Zn: 0.05 to 5.0% by weight or / and Sn: 0.
From 0.5 to 2.0% by weight. In this copper alloy, the number of precipitates (including crystallized substances in the present invention) having a crystal grain size of 30 μm or less and a grain size of 0.1 μm or less in the final plate thickness accounts for 98% or more of the whole. It is desirable to make.

[0005]

Next, the reasons for adding each component of the copper alloy according to the present invention and the reasons for limiting the crystal grain size and the grain size of precipitates will be described. (Cr) Cr has the effect of precipitating finely in Cu, which is the base material, in the aging heat treatment after soaking to improve the strength, and also has the effect of improving the press punching property. However, if the content is less than 0.05% by weight, the sufficient effect cannot be expected. If the content exceeds 0.6% by weight, not only the effect is saturated, but also excessive Cr deteriorates crystallizing bending workability and Ag plating property. . In addition, the crystallized material of hard Cr grows elongated only in the rolling direction by isotropically receiving pressure from the soft Cu base material in the rolling step, and is adjacent when the lead frame is formed by etching. This may cause a short circuit between the leads. Therefore, the content of Cr is set to 0.05% by weight to 0.6% by weight or less.

(Mg) Mg improves the strength by solid solution strengthening without significantly lowering the conductivity. In particular, it has the effect of shifting the strength softening temperature to the higher temperature side, and contributes to high strength and high electrical conductivity. It is also effective in improving press punching properties, heat-peeling resistance of solder, stress relaxation resistance, and spring limit values. However, if the content is less than 0.05% by weight, the sufficient effect cannot be expected. If the content exceeds 1.0% by weight, not only the effect is saturated, but also the molten metal becomes extremely oxidized at the time of melting and casting, and it is very difficult to form an ingot. Becomes In addition, the amount of S
Even if it is less than the weight percentage, the generation of Ag projections cannot be avoided. Therefore, the content of Mg is set to 0.05% by weight to 1.0% by weight or less.

(Zn) Zn is added as necessary to improve strength, solder weather resistance and migration resistance. However, if the content is less than 0.05% by weight, a sufficient effect cannot be expected, and if it exceeds 5.0% by weight, the conductivity is significantly reduced. On the other hand, if the content exceeds 5.0% by weight, the growth of the alloy layer formed at the interface between the solder and the base material is accelerated,
A phenomenon (whitening) occurs in which the alloy layer is brittle from the base material interface to the surface and changes into an alloy layer having poor electrical conductivity. Therefore, the content of Zn is set to 0.05% by weight to 5.0% by weight or less.

(Sn) Sn improves strength by solid solution strengthening. In particular, it has the effect of shifting the strength softening temperature to a higher temperature side and contributes to high strength and high electrical conductivity. Further, there is an effect of improving the spring limit value. However, if the content is less than 0.05% by weight, the sufficient effect cannot be expected, and if it exceeds 2.0% by weight, the electrical conductivity decreases. Therefore, the content of Sn is set to 0.05% by weight to 2.0% by weight or less.

(C, S, Se) These elements are composed of Cu-C
Improves the press punching property of the r-Mg based alloy. Explaining each element individually, C is 0.0003% by weight
If less than that, the effect is not sufficient. On the other hand, 0.0
If the content exceeds 2% by weight, crystallization of Cr is generated at the time of casting, and solder heat resistance and Ag plating property are deteriorated.
Therefore, the content of C is set to 0.0003% by weight to 0.02% by weight or less. S is present as an inclusion in Cu, and has an effect of improving the press-punching property and the machinability of the hot-rolled material during face cutting. However, if the content is less than 0.0003% by weight, the effect is not sufficient, and if it exceeds 0.005% by weight, the hot workability deteriorates. In addition, S contained in the copper alloy
Easily forms a compound with Mg. If a large amount of this Mg-S compound is present in the alloy, when the Ag plating is performed (the lead frame is usually subjected to Ag plating),
Ag may be abnormally precipitated in the -S compound portion, and a projection of Ag may be formed. S also forms a compound with Se,
If this Se-S is present in large numbers on the plate surface, it causes the Ag plating to have a partial luster. Since the presence of such Ag projections and partial luster lowers the reliability of wire bonding, S is 0.005 from the standpoint of preventing this.
% By weight or less. Therefore, the content of S is set to 0.0003 to 0.005% by weight. Se is Se-
Forming a compound such as S, Cu-Se, etc., has the effect of improving press punching properties and improving the machinability at the time of face milling of a hot-rolled material. However, the effect is insufficient when less than 0.00001% by weight. On the other hand, when the content exceeds 0.001% by weight, the Se—S compound increases, the soldering heat-peelability decreases, and the Ag content increases.
Partial gloss occurs on the surface after plating, and the reliability of wire bonding is reduced. Therefore, the content of Se is set to 0.00001% by weight to 0.001% by weight.

(Crystal Grain Size) Generally, the larger the crystal grain size,
The drawability improves and the anisotropy of the mechanical properties disappears, but the strength itself decreases as the crystal grain size increases. In addition, copper alloys for electric and electronic parts, which are applications of the alloy of the present invention, are often subjected to complicated bending processing. If the crystal grain size is too large, roughened skin called orange peel at the bent portion and cracks due to it are caused. Occur. The rough surface is caused by a difference in distortion due to deformation between the crystal grain and the grain boundary, and it is necessary to control the crystal grain size so as not to deteriorate the commercial value. Further, the susceptibility to stress corrosion cracking increases as the crystal grain size increases, and the corrosion resistance decreases. For these reasons, the crystal grain size of the final product is desirably 30 μm or less on average. In addition,
The crystal grain size is determined by observing the structure of the plate cross section parallel to the rolling direction with an optical microscope and setting the cutting direction to the plate thickness direction according to JIS-H-0.
It is measured according to the cutting method specified in 501.

(Grain Size of Precipitates) Coarse precipitates and crystallized substances not only contribute little to strength but also cause deterioration of Ag plating properties. Particularly hard crystallization of Cr grows elongated only in the rolling direction by isotropically receiving hydrostatic pressure from a soft Cu base material in the rolling step, and is adjacent when the lead frame is formed by etching. This may cause a short circuit between the leads. Therefore, it is better that the number of coarse Cr precipitates and crystallized substances is as small as possible. The number of precipitates and crystallized substances having a particle size of 0.1 μm or less should be 98% or more of the total number of Cr compounds in the structure. Is desirable. In the copper alloy according to the present invention, especially when the Cr content exceeds 0.3 wt%, the grain size is 0.1 μm during casting.
May be formed, and coarse Cr precipitates of about 0.1 μm may be formed during hot rolling. The amount of these coarse precipitates and precipitates Is
By the following manufacturing process, it can be suppressed to 1% or less of the whole. In addition, the particle size of a crystallized substance and a precipitate is observed with a transmission electron microscope (TEM), and those having a particle diameter of 10 nm or more are counted. Usually, a precipitate compatible with the base material is observed in the shape of coffee beans, and a precipitate incompatible with the base material is observed in the shape of a circle or an ellipse.

The copper alloy according to the present invention can be produced, for example, by the following steps. (1) Solution treatment ... (a) After heating at a temperature of 850C to 1050C for 10 minutes to 5.0 hours, hot rolling is performed,
Ensure that the hot-rolling end temperature is at least 700 ° C and immediately after 100
Cooling at a rate of not less than 25 ° C./min, and / or (b) using a continuous annealing line and heating at a temperature of not less than 700 ° C. for 5 seconds to 5 minutes in a heating furnace, and Cool at speed. (2) Cold working: After solution treatment, cold working is performed at a working rate of 30% or more. (3) Precipitation annealing: 30 at a temperature of 300 to 600 ° C
Anneal for minutes to 5 hours. (4) Cold working: Cold working is performed at a working ratio of 90% or less. (3) and (4) are repeated a plurality of times as necessary.

Next, the above manufacturing steps will be described. (1) Solution treatment ... The solution treatment is performed in order to dissolve Cr in the matrix. The higher the solution temperature, the higher the solid solution limit because the higher the solid solution limit, the higher the solid solution amount, and high strength is obtained after the subsequent aging treatment. Therefore, it is necessary to secure at least 700 ° C. or higher. If the cooling rate after the solution treatment is low, coarse precipitates inconsistent with the base material are deposited if the cooling rate is low, and the strength after the aging treatment cannot be secured. Therefore, it needs to be performed as quickly as possible. One or both of the above (a) and (b) are performed as a solution solution method. (A) also serves as a solution treatment step by hot rolling, and (b) is suitable for performing more uniform solution treatment on a thin plate. In the case of (b), the heating rate is preferably 50 ° C./sec or more.

(2) Cold working: This cold working is performed after the solution treatment, for work hardening and for forming precipitate nuclei in the subsequent aging step. If the working ratio is less than 30%, the effect is insufficient. Therefore, the cold working rate after the solution treatment is set to 30% or more. (3) Precipitation annealing: Precipitation annealing is performed in order to uniformly and finely precipitate the solid solution Cr in the base material by the solution treatment to obtain high strength. When the annealing temperature is lower than 300 ° C., the precipitation does not proceed rapidly and a long time is required to obtain high strength,
Not economic. On the other hand, when the temperature exceeds 600 ° C., coarsening of the crystal grain size (growing to more than 30 μm) and coarsening of the Cr precipitate (growing to more than 0.1 μm) progress, and the strength is significantly reduced. Further, the re-solution of a part of Cr also proceeds, and the electric conductivity is remarkably reduced. Therefore, the processing temperature is 300 ° C. to 600 ° C.
And the processing time was 30 minutes to 5 hours. (4) Cold working: This cold working is performed to adjust the desired strength, electrical conductivity, bending workability, and the like of the refining. However, if the working ratio exceeds 90%, the bending workability after working cannot be ensured. Therefore, the cold working ratio is set to 90% or less.
In addition, by repeating the above-described precipitation annealing and cold working a plurality of times as needed, a copper alloy having higher strength and higher conductivity can be provided.

[0015]

Embodiments of the present invention will be described below. (Example 1) Copper alloys having the components shown in Table 1 were lumped in air in a crypt furnace under a borax coating, and were subjected to 50 mmt x 8
An ingot of 0 mmw × 180 mm1 was prepared. These ingots were heated at 950 ° C. for 30 minutes, subjected to hot rolling, and then rapidly cooled from a temperature of 800 ° C. or higher to form a solution treatment. Thereafter, cold rolling was performed, annealing was performed at 450 ° C. for 2 hours as a precipitation treatment, and final rolling was performed to obtain a 0.25 mmt sheet material. In addition, No. In No. 15, the subsequent steps were not performed because cracks occurred during hot rolling.

[0016]

[Table 1]

A test material was sampled from this plate material, and the characteristics of the alloy were examined by the following tests. The results are shown in Tables 2 and 3. (Tensile strength and electrical conductivity) The tensile test was performed by machining a test piece specified in JIS No. 5 by Shimadzu Corporation.
The test was performed using a ton universal testing machine. The conductivity is JI
According to the non-ferrous metal material conductivity measurement method described in S-H0505, the measurement was performed using a double bridge manufactured by Yokogawa Electric Corporation. (W bending test) The test was performed according to the W bending test shown in JIS-H3110. The bending limit was defined as the ratio r / t between the minimum bending radius r at which no cracking occurs and the plate thickness t. The presence or absence of cracks in the sample was determined by SEM observation (250 times) and cross section observation (200 times).

(Solder Resistance to Heat Resistance) After the test material was subjected to electrolytic degreasing and pickling with sulfuric acid, an inactive flux was applied and immersed in a 245 ° C. 60Sn / 40Pb solder layer for 5 seconds for soldering. And furthermore, the materials
Heat in an oven at 50 ° C for 1000 hours, then 2mm
After bending by 180 ° at R, the plate was bent back, and the peeling and whitening of the solder were observed. (Ag plating property test) All the samples were mirror-polished to reduce the influence of the surface. As plating pretreatment, electrolytic degreasing and pickling with sulfuric acid were performed. Ag plating was performed through a substitution prevention treatment after applying a Cu base plating to the pretreated material. The observation was performed with a stereoscopic microscope (× 40). Those which did not produce protrusions or partial gloss and were excellent in Ag plating properties were evaluated as ○.

(Press punching test) The press punching test is carried out by applying a compressive load using a circular die with a universal testing machine, and observing burrs generated in the rolling parallel direction by SEM (500 times). The average height was measured. In addition, the punching clearance is one side: plate thickness of 20.
%. (Migration resistance test) A test piece having a width of 3 mm was fixed at a gap of 1 mm, and the exposed length was set to 20 mm.
Immersion (tap water) and drying were repeated 50 cycles while applying V, and migration resistance was evaluated based on the maximum leak current at that time.

[0020]

[Table 2]

[0021]

[Table 3]

From Tables 2 and 3, the alloy of the present invention has high strength,
It can be seen that it has high conductivity, and is excellent in W bending workability, solder weather resistance, Ag plating property, press punching property (burr height), and migration resistance (Leak current). On the other hand, the comparative alloy is inferior in either property. In particular, no. In Nos. 16, 18, and 20, the added amounts of C, S, and Se are insufficient, and the press punching property (burr height) is not sufficient. In addition, No. 1 containing these elements in excess. 1
Nos. 7, 19, and 21 have good press punching properties, but are inferior in bending workability, solder heat peelability, and Ag plating properties.

Example 2 Cu-0.35Cr-0.3
4Mg-1.0Zn (S: 0.0005%, C: 0.0
(007%, Se: 0.0002%), after hot rolling and solution treatment in the same steps as in Example 1, then cold rolling, precipitation and final rolling under various conditions. Was performed to obtain three types of plate materials (0.25 mmt) in which the crystal grain size and the precipitate grain size were changed. A test material was sampled from this plate, and the grain size and the grain size were 0.1 μm according to the method described above.
The ratio of precipitates of m or less was measured, and the characteristics of the alloy were examined by the above-mentioned test, and the etching workability was examined by the following test. (Etching workability test)
The actual lead frame etching was simulated, the leads were etched at a pitch of 0.2 mm in the direction perpendicular to the rolling direction, the presence or absence of short circuits between adjacent leads was examined, and the etching workability was evaluated by the number of short circuits / the total number.

[0024]

[Table 4]

As shown in Table 4, No. 1 having a crystal grain size exceeding 30 μm was used. In No. 2, the W-bending workability is greatly deteriorated.
Further, in the case of No. 3 having a large ratio of precipitates exceeding 0.1 μm.
No. 3 has deteriorated Ag plating property and etching processability, and coarse precipitates and crystallized substances not only act as starting points of projections during Ag plating, but also cause short-circuiting of leads after etching. I understand.

[0026]

The copper alloy for electric / electronic parts according to the present invention is excellent in high strength, high conductivity, bending workability, heat peeling resistance of solder, press punching property, Ag plating property and etching workability. .

Claims (4)

[Claims] 1. Cr: 0.05 to 0.6% by weight, Mg:
0.05-1.0% by weight, C: 0.0003-
0.02% by weight, S: 0.0003 to 0.005% by weight, Se: 0.00001 to 0.001% by weight, the balance being Cu and unavoidable impurities.
Copper alloy for electronic components. 2. Cr: 0.05 to 0.6% by weight, Mg:
0.05 to 1.0% by weight, Zn: 0.05 to 5.0% by weight, C: 0.0003 to 0.02% by weight, S:
0.0003 to 0.005% by weight, Se: 0.00000
1 to 0.001% by weight, with the balance being Cu and unavoidable impurities, a copper alloy for electric / electronic parts 3. The copper alloy for electric / electronic parts according to claim 1, further comprising Sn: 0.05 to 2.0% by weight. 4. The method according to claim 1, wherein the crystal grain size at the final plate thickness is 30 μm or less, and the number of precipitates having a grain size of 0.1 μm or less accounts for 98% or more of the whole. Copper alloys for electric or electronic parts described in any of them