TW201840870A - Cu-Ni-Si-based copper alloy strip and method for manufacturing same - Google Patents

Abstract

The purpose of this invention is to provide a Cu-Ni-Si-based copper alloy strip and a method for manufacturing the same, the Cu-Ni-Si-based copper strip whereby the strength thereof is enhanced, the occurrence of smut is appropriately suppressed, and excellent adhesion to a resin is obtained. This Cu-Ni-Si-based copper alloy strip contains 1.5-4.5% by mass of Ni and 0.4-1.1% by mass of Si, the remainder comprising Cu and unavoidable impurities, wherein the electrical conductivity thereof is 30% IACS or greater, the tensile strength thereof is 800 MPa or greater, and the lightness L* thereof in the L*a*b* color space specified in JIS-Z8781:2013 after being immersed for 10 seconds in a 40 wt% nitric acid aqueous solution at room temperature is 50-75.

Description

 Cu-Ni-Si copper alloy strip and manufacturing method thereof  

The present invention relates to a Cu-Ni-Si-based copper alloy strip which can be preferably used for producing electronic parts such as electronic materials and a method for producing the same.

In recent years, with the miniaturization of IC packages, miniaturization and even pinning of lead frames, various terminals of electronic devices, and the like have been demanded. In particular, a pad assembly electrode pad called an LSI package called QFN (Quad Flat Non-Leaded package) has been developed, and a structure in which the lead pins are not exposed is required, and a plurality of pins and a narrow pitch are required. In order to multiply the lead frames and the like, it is necessary to perform micro-machining by etching. Therefore, it is required to improve the etching property, the plating adhesion, the resin adhesion, and the like while improving the strength of the copper alloy to be a material. According to such a situation, an aging precipitation type Cu-Ni-Si-based copper alloy was developed.

However, when a Cu-Ni-Si-based copper alloy is used for an electronic component such as a lead frame, pickling is performed as a pretreatment, but in the case of pickling, the Ni-Si-based compound is oxidized to be in the form of a smut. Remaining on the surface of the material. When the amount of the residue of the dirt is increased, there is a case where the bonding between the lead frame and the mold resin is interposed between the assembly steps of the IC package, the resin adhesion is lowered, or the solder or plating adhesion is lowered. .

Therefore, there is disclosed a technique for suppressing the residual of dirt during pickling by limiting the particle size of the Ni-Si-based precipitate of the Cu-Ni-Si-based copper alloy and limiting the contents of Ni and Si. Improved solder adhesion and plating properties (Patent Document 1).

Prior technical literature

Patent literature

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei 8-319527

However, in the case of the technique described in Patent Document 1, in order to improve the solder adhesion and the plating property, it is desired to substantially completely remove the dirt of the NiSi particles in the pickling. Therefore, there is a problem that the surface of the material exposed after pickling does not substantially generate irregularities formed by the precipitates, and the anchoring effect by the unevenness is lowered, so that the adhesion to the resin is deteriorated. Therefore, for example, the adhesion between the lead frame and the mold resin in the assembly step of the above IC package is affected.

In other words, the present invention has been made to solve the above problems, and an object of the present invention is to provide a Cu-Ni-Si-based copper alloy strip which is excellent in adhesion to a resin while suppressing the generation of contaminants while improving the strength, and the production thereof. method.

As a result of various studies, the present inventors have found that when the Cu-Ni-Si-based copper alloy strip is pickled, the dirt is excessively generated until the layered state causes the resin adhesion to be lowered, but the dirt is excessively removed. Further, the unevenness formed by the NiSi precipitates disappears, and the anchoring effect by the unevenness is lowered, so that the adhesion to the resin is lowered. In other words, the inventors of the present invention have found that the surface of the surface remains uneven due to the fact that the stain remains moderately during pickling, and the adhesion to the resin is improved. Moreover, as a method of suppressing the generation of contaminants as described above, a method of adjusting the solution treatment conditions at the time of producing a copper alloy strip was found.

That is, the Cu-Ni-Si-based copper alloy strip of the present invention contains Ni: 1.5 to 4.5% by mass, Si: 0.4 to 1.1% by mass, and the remainder is composed of Cu and unavoidable impurities, and its conductivity is 30. Above 100% IACS, the tensile strength is 800 MPa or more, and after immersing in a 40 wt% aqueous solution of nitric acid at room temperature for 10 seconds, the brightness L* in the L*a*b* color system specified in JIS-Z8781:2013 is 50. ~75.

It is preferable to further contain one or more selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr in a total amount of 0.005 to 0.8% by mass.

The method for producing a Cu-Ni-Si-based copper alloy strip according to the present invention is Cu-Ni-Si containing Ni: 1.5 to 4.5% by mass, Si: 0.4 to 1.1% by mass, and the balance being Cu and inevitable impurities. After the hot-rolling and cold-rolling of the ingots of the copper alloy strips, the solution treatment is followed by the aging treatment, and the aging treatment is performed at a degree of work of 40% or more, followed by cold rolling, and the solution treatment is adjusted as follows. That is, after the solution treatment and the material before the aging treatment are immersed in a 40 wt% aqueous solution of nitric acid at room temperature for 10 seconds, it is in the L*a*b* color system defined in JIS-Z8781:2013. When the brightness L* is measured, the brightness L* is 40 to 70.

According to the present invention, a Cu-Ni-Si-based copper alloy strip having high strength and moderately suppressing generation of contaminants and having excellent adhesion to a resin is obtained.

Hereinafter, a Cu-Ni-Si-based copper alloy strip according to an embodiment of the present invention will be described. In addition, in the present invention, the % is referred to as % by mass unless otherwise specified.

First, the reasons for limiting the composition of the copper alloy strip will be described.

<Ni and Si>

In the Ni and Si systems, Ni and Si form fine precipitated particles of an intermetallic compound mainly composed of Ni ₂ Si by aging treatment, and the alloy strength is remarkably increased. Further, as Ni ₂ Si is precipitated in the aging treatment, the conductivity is improved. However, in the case where the Ni concentration is less than 1.5%, or when the Si concentration is less than 0.4%, the required strength cannot be obtained even if other components are added. Further, in the case where the Ni concentration exceeds 4.5% or the Si concentration exceeds 1.1%, although sufficient strength can be obtained, the conductivity is lowered, and further, a coarse Ni- which does not contribute to strength improvement is formed in the parent phase. Si-based particles (crystals and precipitates) cause deterioration in bending workability, etching properties, and plating properties. Therefore, the content of Ni is set to 1.5 to 4.5%, and the content of Si is set to 0.4 to 1.1%. It is preferable to set the content of Ni to 1.6 to 3.0% and the content of Si to 0.4 to 0.7%.

<other elements>

Further, in the alloy, it is possible to further improve the strength, heat resistance, stress relaxation resistance, and the like of the alloy, and further comprise a total of 0.005 to 0.8% by mass of a group selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr. More than one. When the total amount of the elements is less than 0.005% by mass, the above effect is not obtained. When the amount exceeds 0.8% by mass, the desired properties are obtained, but the conductivity or the bending workability may be lowered.

<Electrical conductivity and tensile strength TS>

The Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention has a conductivity of 30% IACS or more and a tensile strength TS of 800 MPa or more.

As the operating frequency of the semiconductor element increases, the heat generation due to energization increases, so the conductivity of the copper alloy strip is set to 30% IACS or more.

Moreover, the tensile strength TS is set to 800 MPa or more in order to prevent deformation of the lead frame at the time of wire bonding and the like to maintain the shape.

<Brightness L*>

The Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention is immersed in a 40 wt% aqueous solution of nitric acid at room temperature for 10 seconds, and is then in the L*a*b* color system specified in JIS-Z8781:2013. The brightness L* is 50~75.

When the sample is immersed in an aqueous solution of nitric acid, dirt is generated on the surface of the sample and remains, and the color of the surface of the sample is darkened. Therefore, by measuring the color tone of the surface of the sample, it is possible to determine whether or not the stain is generated.

If the brightness L* is close to 0, it turns black, and if it is close to 100, it turns white.

By immersing the Cu-Ni-Si-based copper alloy strip of the embodiment of the present invention in a nitric acid aqueous solution, the brightness L* is 50 to 75, and it is possible to obtain a moderate residual NiSi precipitation on the surface of the material after pickling. The uneven surface of the object has good adhesion to the resin by the anchoring effect.

On the other hand, when the brightness L* is less than 50, the stain is largely generated after the pickling, and the surface of the material is covered in a layered manner, and the resin adhesion is lowered due to the peeling of the dirt layer and the copper alloy layer. When the brightness L* exceeds 75, the dirt is excessively removed during pickling, and the NiSi precipitate on the surface becomes small and the surface unevenness becomes small. As a result, the anchoring effect is not obtained, or the surface area of the copper alloy (substrate) on the surface of the material is increased, whereby the growth of the oxide film of Cu is promoted, and the oxide film is peeled off and the adhesion to the resin is lowered.

As a method of controlling the brightness L* of the copper alloy strip to 50 to 75, a method of adjusting the following solution treatment conditions can be mentioned. The solution treatment conditions will be described below.

<Manufacture of Cu-Ni-Si copper alloy strip>

The Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention can be produced by sequentially performing hot rolling, cold rolling, solution treatment, aging treatment, post-aging cold rolling, and relaxation annealing on the ingot. Cold rolling before solution treatment is not necessary and can be carried out as needed. Further, cold rolling may be performed after the solution treatment and before the aging treatment as needed. During the above steps, grinding, polishing, shot blasting, pickling, and the like for removing scale on the surface can be suitably performed.

The solution treatment is a heat treatment in which a telluride such as a Ni-Si compound is dissolved in a Cu parent material and a Cu parent material is recrystallized.

In the method for producing a Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention, the solution treatment conditions are adjusted in such a manner that the material before the solution treatment and before the aging treatment is immersed at room temperature. After 10 seconds in a 40 wt% aqueous solution of nitric acid, the luminance L* in the L*a*b* color system specified in JIS-Z8781:2013 was 40 to 70.

By adjusting the solution treatment conditions as described above, Ni and Si, which are causes of the dirt, are moderately dissolved in Cu, and the amount of NiSi precipitates is precisely controlled. As a result, the obtained Cu can be obtained. The brightness of the Ni-Si copper alloy strip is controlled to be 50 to 75.

When the brightness L* of the material after the solution treatment is less than 40, the solution treatment is insufficient, and the amount of NiSi precipitates which become dirt is excessive.

When the brightness L* of the material after the solution treatment exceeds 70, the solution treatment is excessive, and the amount of NiSi precipitates which become dirt is too small.

Further, in order to change the solution treatment conditions, it is only necessary to control the temperature and time of the solution treatment, but the temperature and time of the specific solution treatment are not specified because the addition of Ni, Si, etc. in the copper alloy strip is added. The amount of the Ni-Si compound before the solution treatment or the particle size differs depending on the amount of the step or the solution treatment.

<Aging treatment>

The aging treatment is such that the solid solution dissolved in the solution treatment is precipitated as fine particles of an intermetallic compound mainly composed of Ni ₂ Si. The strength and electrical conductivity increase due to the aging treatment. The aging treatment can be carried out, for example, at 375 to 625 ° C for 1 to 50 hours, whereby the strength can be improved.

When the aging time is less than one hour, there is a case where the precipitation amount of the Ni-Si-based precipitate is small and the strength is insufficient. In addition, when the aging temperature exceeds 625 ° C or the aging time exceeds 50 hours, there is a case where the precipitate is coarsened or re-solidified, the amount of generated dirt is increased, the strength is insufficient, or the conductivity is lowered. .

<cold rolling>

Next, after the aging treatment, cold rolling is performed at a working degree of 40% or more (cold rolling after aging treatment).

When the cold rolling is performed at a degree of work of 40% or more, the tensile strength is 800 MPa or more by work hardening.

If the degree of processing is less than 40%, there is a case where the strength is insufficient.

It is more preferable to carry out cold rolling after aging treatment with a working degree of 40 to 90% or more. When the degree of work exceeds 90%, the decrease in electrical conductivity due to the processing strain becomes remarkable, and even if the relaxation annealing is performed, the electrical conductivity is low.

The degree of cold rolling after aging treatment is the rate of change of the thickness after cold rolling after aging treatment with respect to the thickness of the material before cold rolling after aging treatment.

The thickness of the Cu-Ni-Si-based copper alloy strip of the present invention is not particularly limited, and may be, for example, 0.03 to 0.6 mm.

<Swelling Annealing>

The relaxation annealing can be performed after cold rolling after the aging treatment. The relaxation annealing may be carried out under ordinary conditions, for example, at 300 ° C to 550 ° C and a holding time of 5 seconds to 300 seconds. Thereby, the residual stress in the material can be removed.

Example 1

Samples of the respective examples and comparative examples were as follows.

The electrolytic copper was used as a raw material, and the copper alloy having the composition shown in Tables 1 and 2 was melted by an atmospheric melting furnace, and cast into an ingot having a thickness of 20 mm and a width of 60 mm. The ingot was hot rolled at 950 ° C until the sheet thickness was 10 mm. After hot rolling, grinding and cold rolling are carried out in sequence.

Next, the solution treatment and the aging treatment are sequentially performed under the conditions shown in Tables 1 and 2. Thereafter, aging treatment was carried out in accordance with the processing degrees shown in Tables 1 and 2, followed by cold rolling until the sheet thickness was 0.150 mm, and annealing was performed at 450 ° C for 30 seconds to obtain a sample.

<Electrical conductivity (%IACS)>

For the obtained sample, the conductivity (% IACS) at 25 ° C was measured by a four-terminal method based on JIS H0505.

<tensile strength (TS)>

With respect to the obtained sample, the tensile strength (TS) in the direction parallel to the rolling direction was measured by a tensile tester in accordance with JIS-Z2241. First, a JIS 13B test piece was produced from each sample so that the stretching direction became the rolling direction. The conditions of the tensile test were set to a test piece width of 12.7 mm, room temperature (15 to 35 ° C), a tensile speed of 5 mm/min, and a gauge length of 50 mm.

<Brightness L*>

After the solution treatment, the sample before the aging treatment and the single surface of the sample after the relaxation annealing were immersed in a 40 wt% aqueous solution of nitric acid at room temperature for 10 seconds, and then rinsed with running water. For the surface of the sample after the treatment, the luminance L* was obtained using a color difference meter.

The color difference meter was measured using a CR-200 manufactured by Konica Minolta.

<Adhesion to resin>

After the sample subjected to the relaxation annealing was cut into a length of 100 mm in the parallel direction and a width of 20 mm, the single side of the sample was immersed in a 40 wt% aqueous solution of nitric acid at room temperature for 10 seconds, and then rinsed with running water. Next, the sample was subjected to atmospheric heating at 240 ° C for 5 minutes. After heating in the air, the acid-resistant tape was attached to the surface of the one-side length of 60 mm, and then peeled off, and the presence or absence of the adhering substance to the adhesive surface of the acid-resistant tape was determined by image processing. Specifically, the image of the adhesive surface of the acid-resistant tape was binarized, and the ratio of the total area of the black image area to be attached to the area of the adhesive surface of the acid-resistant tape was calculated and evaluated based on the following criteria. When the evaluation is ○, the adhesion to the resin is excellent.

○: The total area of the attached matter is less than 10% of the area of the adhesive surface of the tape

×: The total area of the attached matter exceeds 10% of the area of the adhesive surface of the tape

The results obtained are shown in Table 1.

As is apparent from Table 1, in the case of each of the examples in which the luminance L* was 50 to 75, the strength was high and the adhesion to the resin was excellent.

On the other hand, in the case of Comparative Example 1 in which the luminance L* exceeded 75, the adhesion to the resin was inferior. The reason is considered to be that the NiSi precipitate on the surface of the material is too small, the Cu on the surface is significantly oxidized, and the surface oxide film is peeled off, and the adhesion to the resin is lowered.

In the case of Comparative Example 2 in which the luminance L* was less than 50, the amount of generated dirt was increased, and the adhesion to the resin was inferior.

In the case of Comparative Example 3 in which the degree of processing of cold rolling after aging treatment exceeded 90%, the electrical conductivity was less than 30% IACS.

In the case of Comparative Example 4 in which the degree of cold rolling after the aging treatment was less than 40%, the tensile strength was less than 800 MPa.

In the case of Comparative Example 5 in which the content of Ni and Si exceeded a predetermined range, the electrical conductivity was less than 30% IACS.

In the case of Comparative Example 7 containing one or more of a group selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr in a total amount of more than 0.8% by mass, the electrical conductivity was also less than 30% IACS.

In the case of Comparative Example 8 in which the aging temperature was less than 625 ° C and the comparative example 10 in which the aging time was less than 1 hour, it became sub-aging and the tensile strength was less than 800 MPa.

In Comparative Example 9 in which the aging temperature exceeded 625 ° C and Comparative Example 11 in which the aging time exceeded 50 hours, it became overaged, and the tensile strength was less than 800 MPa. Further, the Ni-Si-based precipitates are remarkably precipitated due to overaging, and the luminance L* is less than 50, and the amount of generated contaminants is increased, and the adhesion to the resin is inferior.

Claims (3)

 A Cu-Ni-Si copper alloy strip containing Ni: 1.5 to 4.5% by mass, Si: 0.4 to 1.1% by mass, and the remainder consisting of Cu and unavoidable impurities, and its conductivity is 30% IACS The tensile strength is 800 MPa or more, and after immersing in a 40 wt% aqueous solution of nitric acid at room temperature for 10 seconds, the brightness L* in the L*a*b* color system specified in JIS-Z8781:2013 is 50-75. .    The Cu-Ni-Si-based copper alloy strip according to claim 1 further contains at least one selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr in a total amount of 0.005 to 0.8% by mass.    A method for producing a Cu-Ni-Si-based copper alloy strip, which is Cu-Ni-Si containing Ni: 1.5 to 4.5% by mass, Si: 0.4 to 1.1% by mass, and the balance being Cu and inevitable impurities After the hot-rolling and cold-rolling of the ingots of the copper alloy strips, the solution treatment is followed by the aging treatment, and the aging treatment is performed at a degree of work of 40% or more, followed by cold rolling, and the solution treatment is adjusted as follows. That is, after the solution treatment and the material before the aging treatment are immersed in a 40 wt% aqueous solution of nitric acid at room temperature for 10 seconds, it is in the L*a*b* color system defined in JIS-Z8781:2013. When the brightness L* is measured, the brightness L* is 40 to 70.