JP6811136B2 - Cu-Ni-Si based copper alloy strip and its manufacturing method - Google Patents

Description

The present invention relates to Cu—Ni—Si based copper alloy strips that can be suitably used for manufacturing electronic components such as electronic materials, and methods for manufacturing the same.

In recent years, with the miniaturization of IC packages, there is a demand for miniaturization of lead frames, various terminals of electronic devices, connectors, and the like, and eventually, the number of pins. In particular, a structure called QFN (Quad Flat Non-leaded package), in which electrode pads are placed on the land of the LSI package and lead pins are not exposed, has been developed, and more pins and narrower pitches are required. .. Since fine processing by etching is required to increase the number of pins of these lead frames, etc., it is required to improve the strength of the copper alloy used as the material and improve the etching property, plating adhesion, resin adhesion, etc. Will be done. For these reasons, aging precipitation type Cu—Ni—Si based copper alloys have been developed.

By the way, when a Cu-Ni-Si copper alloy is used for an electronic component such as a lead frame, pickling is performed as a pretreatment, but the Ni-Si compound is oxidized and remains on the material surface as a smut during the pickling. I have something to do. If the amount of this smut residue increases, it may intervene between the lead frame and the mold resin in the IC package assembly process to reduce the resin adhesion or the adhesion of solder or plating.
Therefore, by regulating 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, the residual smut during pickling is suppressed, and the solder adhesion is improved. And a technique for improving the plating property has been proposed (Patent Document 1).

Japanese Unexamined Patent Publication No. 8-319527

However, in the case of the technique described in Patent Document 1, in order to improve solder adhesion and plating property, NiSi grain smut is almost completely removed by pickling. Therefore, there is a problem that the surface of the material exposed after pickling hardly has irregularities due to precipitates, the anchor effect due to the irregularities is reduced, and the adhesion to the resin is inferior. Therefore, for example, it affects the adhesion between the lead frame and the mold resin in the above-mentioned IC package assembly process.
That is, the present invention has been made to solve the above-mentioned problems, and is a Cu—Ni—Si-based copper alloy that improves the strength, appropriately suppresses the generation of smut, and has excellent adhesion to the resin. The purpose is to provide articles and their manufacturing methods.

As a result of various studies by the present inventors, the state in which the smut is excessively generated until the smut becomes a layer during pickling of the Cu—Ni—Si copper alloy strip reduces the resin adhesion, but even if the smut is removed too much. It has been found that the unevenness due to the NiSi precipitate disappears, the anchor effect due to the unevenness is reduced, and the adhesion to the resin is lowered. That is, it has been found that by allowing the smut to remain appropriately during pickling, surface irregularities remain and the adhesion to the resin is improved. Further, as a method for controlling the generation of smut in this way, it has been found that the solution treatment conditions at the time of producing copper alloy strips are adjusted.

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

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

The method for producing a Cu-Ni—Si-based copper alloy strip of the present invention contains Ni: 1.5 to 4.5% by mass and Si: 0.4 to 1.1% by mass, and the balance Cu and unavoidable impurities. an ingot of the Cu-Ni-Si-based copper alloy strips hot rolled, after cold rolling consisting of solution treatment, 375-625 ° C., subjected to aging treatment 1-50 hours in this order, further working ratio 40 After cold rolling after aging treatment at% or more, the material before aging treatment after the solution treatment was immersed in a 40 wt% nitrate aqueous solution for 10 seconds at room temperature, and then L specified in JIS-Z8781: 2013. ^{* A *} b ^{* The} solution treatment is adjusted so that the brightness L ^* in the color system is 40 to 70 when measured.

According to the present invention, a Cu—Ni—Si-based copper alloy strip having high strength, appropriately suppressing the generation of smut, and having excellent adhesion to a resin can be obtained.

Hereinafter, Cu—Ni—Si based copper alloy strips according to the embodiment of the present invention will be described. In the present invention,% means mass% unless otherwise specified.

First, the reason for limiting the composition of the copper alloy strip will be described.
<Ni and Si>
For Ni and Si, by performing the aging treatment, the Ni and Si form fine precipitated particles of an intermetallic compound mainly composed of Ni ₂ Si, which significantly increases the strength of the alloy. In addition, the conductivity is improved with the precipitation of Ni ₂ Si in the aging treatment. However, when the Ni concentration is less than 1.5% or the Si concentration is less than 0.4%, the desired strength cannot be obtained even if the other component is added. Further, when the Ni concentration exceeds 4.5%, or when the Si concentration exceeds 1.1%, sufficient strength can be obtained, but the conductivity becomes low, and further, coarse Ni that does not contribute to the improvement of strength. -Si-based particles (crystals and precipitates) are formed in the matrix, which causes deterioration of bending workability, etching property and plating property. Therefore, the Ni content is 1.5 to 4.5%, and the Si content is 0.4 to 1.1%. Preferably, the Ni content is 1.6 to 3.0% and the Si content is 0.4 to 0.7%.

<Other elements>
Further, in the above alloy, for the purpose of improving the strength, heat resistance, stress relaxation resistance, etc. of the alloy, one or more selected from the group of Mg, Fe, P, Mn, Co and Cr is added in total of 0.005 to 0.8. It can contain mass%. If the total amount of these elements is less than 0.005% by mass, the above effect does not occur, and if it exceeds 0.8% by mass, the desired characteristics can be obtained, but the conductivity and bending workability may be lowered.

<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.
Since heat generation due to energization increases as the operating frequency of the semiconductor element increases, the conductivity of the copper alloy strip is set to 30% IACS or more.
Further, in order to prevent deformation of the lead frame during wire bonding and maintain the shape, the tensile strength TS is set to 800 MPa or more.

<Brightness L ^* >
The Cu—Ni—Si-based copper alloy strip according to the embodiment of the present invention is immersed in a 40 wt% nitric acid aqueous solution for 10 seconds at room temperature, and then the L ^* a ^* b ^* color system specified in JIS-Z8781: 2013. The lightness L ^{* in} is 50 to 75.
When the sample is immersed in an aqueous nitric acid solution, smut is generated and remains on the sample surface, and the color of the sample surface changes darkly. Therefore, by measuring the color tone of the sample surface, it is possible to determine whether or not smut is generated.
When the brightness L ^* approaches 0, it becomes black, and when it approaches 100, it becomes white.

By setting the brightness L ^* after immersion in the nitric acid aqueous solution of the Cu—Ni—Si based copper alloy strip according to the embodiment of the present invention to 50 to 75, NiSi precipitates appropriately remain on the surface of the material after pickling. An uneven surface can be obtained, and the adhesion with the resin is improved by the anchor effect.

On the other hand, when the brightness L ^* is less than 50, a large amount of smut is generated after pickling and covers the material surface in layers, and the resin adhesion is lowered due to the peeling of the smut layer and the copper alloy layer. When the brightness L ^* exceeds 75, the smut is removed too much by pickling, the NiSi precipitate on the surface becomes small, and the surface unevenness becomes small. As a result, the anchor effect cannot be obtained, or the surface area of the copper alloy (matrix) on the surface of the material is increased, so that the growth of the oxide film of Cu is promoted, and the oxide film is peeled off to reduce the adhesion to the resin.
As a method of controlling the brightness L ^* of the copper alloy strip to 50 to 75, it is possible to adjust the solution treatment conditions described later. The solution treatment conditions will be described later.

<Manufacturing of Cu-Ni-Si copper alloy strips>
In the Cu—Ni—Si-based copper alloy strip according to the embodiment of the present invention, the ingot is usually hot-rolled, cold-rolled, solution-treated, aging-treated, cold-rolled after aging, and strain-removed and annealed in this order. Can be manufactured. Cold rolling before solution treatment is not essential and may be carried out if necessary. Further, cold rolling may be carried out after the solution treatment and before the aging treatment, if necessary. During each of the above steps, grinding, polishing, shot blasting, pickling and the like for removing the oxide scale on the surface can be appropriately performed.

The solution treatment is a heat treatment in which silicide such as a Ni—Si compound is dissolved in a Cu base material and at the same time the Cu base material is recrystallized.
In the method for producing Cu—Ni—Si-based copper alloy strips according to the embodiment of the present invention, the material after the solution treatment and before the aging treatment is immersed in a 40 wt% nitric acid aqueous solution at room temperature for 10 seconds, and then JIS-. The solution treatment conditions are adjusted so that the brightness L ^* in the L ^* a ^* b ^* color system specified in Z8781: 2013 is 40 to 70 when measured.
By adjusting the solution treatment conditions as described above, Ni and Si, which cause smut, were appropriately dissolved in Cu, and the amount of NiSi precipitate was controlled in just proportion, and as a result, it was obtained. The brightness L ^* in the Cu—Ni—Si based copper alloy strip can be controlled to 50 to 75.

If the lightness L ^* of the material after the solution treatment is less than 40, the solution treatment is insufficient and the amount of NiSi precipitates to be smut becomes too large.
If the lightness L ^* of the material after the solution treatment exceeds 70, the solution treatment is excessive and the amount of NiSi precipitates to be smut becomes too small.
In order to change the solution treatment conditions, the temperature and time of the solution treatment may be controlled, but the specific temperature and time of the solution treatment are not specified for Ni and Si in the copper alloy strip. This is because the amount and particle size of the Ni—Si-based compound before the solution treatment differ depending on the amount of the addition and the conditions of the step before the solution treatment.

<Aging process>
In the aging treatment, the silicide dissolved in the solution treatment is precipitated as fine particles of an intermetallic compound mainly composed of Ni ₂ Si. This aging treatment increases the strength and conductivity. The aging treatment can be carried out under the conditions of, for example, 375 to 625 ° C. and 1 to 50 hours, whereby the strength can be improved.
If the aging time is less than 1 hour, the amount of Ni—Si-based precipitates precipitated may be small and the strength may be insufficient. When the aging temperature exceeds 625 ° C. or the aging time exceeds 50 hours, the precipitates become coarse and resolidified, the amount of smut generated increases, the strength becomes insufficient, and the conductivity becomes low. May be low.

<Cold rolling>
Next, after the aging treatment, cold rolling (cold rolling after the aging treatment) is performed at a processing degree of 40% or more.
If cold rolling with a work degree of 40% or more is performed, the tensile strength becomes 800 MPa or more due to work hardening.
If the degree of processing is less than 40%, the strength may be insufficient.
It is more preferable to perform cold rolling after the aging treatment at a processing degree of 40 to 90% or more. If the degree of processing exceeds 90%, the conductivity is significantly lowered due to the processing strain, and the conductivity may be low even if the strain is removed and annealed.
The workability of cold rolling after aging treatment is the rate of change in thickness due to cold rolling after aging treatment with respect to the material thickness immediately 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, but may be, for example, 0.03 to 0.6 mm.

<Distortion annealing>
Strain removal annealing can be performed after cold rolling after aging treatment. Strain removal annealing may be performed under general conditions, for example, 300 ° C. to 550 ° C., and a holding time of 5 seconds to 300 seconds. This makes it possible to remove the residual stress in the material.

Samples of each Example and each Comparative Example were prepared as follows.
Using electrolytic copper as a raw material, copper alloys having the compositions shown in Tables 1 and 2 were melted and cast into an ingot having a thickness of 20 mm and a width of 60 mm using an atmospheric melting furnace. This ingot was hot-rolled at 950 ° C. to a plate thickness of 10 mm. After hot rolling, grinding was performed, and cold rolling was performed in this order.
Next, the solution treatment and the aging treatment were performed in this order under the conditions shown in Tables 1 and 2. Then, cold rolling was performed after aging treatment to a plate thickness of 0.150 mm at the processing degrees shown in Tables 1 and 2, and strain annealing was performed at 450 ° C. for 30 seconds to obtain a sample.

<Conductivity (% IACS)>
The obtained sample was measured for conductivity (% IACS) at 25 ° C. by the 4-terminal method based on JIS H0505.

<Tensile strength (TS)>
The tensile strength (TS) of the obtained sample was measured by a tensile tester in a direction parallel to the rolling direction according to JIS-Z2241. First, from each sample, a JIS13B test piece was prepared using a press machine so that the tensile direction was the rolling direction. The conditions of the tensile test were 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, one side of the sample before the aging treatment and the sample after strain annealing were immersed in a 40 wt% nitric acid aqueous solution at room temperature for 10 seconds and then rinsed with running water. The brightness L * of the treated sample surface was determined using a color difference meter.
The color difference meter was measured using CR-200 manufactured by Konica Minolta.

<Adhesion with resin>
The sample after strain-removal annealing was cut out to a length of 100 mm and a width of 20 mm in the parallel direction of rolling, and then one side of the sample was immersed in a 40 wt% nitric acid aqueous solution at room temperature for 10 seconds and then rinsed with running water. Next, this sample was heated to the atmosphere at 240 ° C. for 5 minutes. After heating to the atmosphere, an acid-resistant tape was attached to the range of 60 mm in length on one side and then peeled off, and the presence or absence of deposits on 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, the ratio of the total area of the black image area to be the deposit to the area of the adhesive surface of the acid-resistant tape was calculated, and evaluated according to the following criteria. If the evaluation is ◯, the adhesion with the resin is excellent.
◯: The total area of deposits is 10% or less of the area of the tape adhesive surface ×: The total area of deposits exceeds 10% of the area of the tape adhesive surface

The results obtained are shown in Table 1.

As is clear from Table 1, in each of the examples having a brightness L ^* of 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 brightness L ^* exceeded 75, the adhesion to the resin was inferior. It is considered that this is because the amount of NiSi precipitates on the surface of the material is too small, the Cu oxidation on the surface is remarkable, and the surface oxide film is peeled off to reduce the adhesion to the resin.
In the case of Comparative Example 2 in which the brightness L ^* was less than 50, the amount of smut generated was large and the adhesion to the resin was inferior.

In the case of Comparative Example 3 in which the workability of cold rolling after aging treatment exceeded 90%, the conductivity was less than 30% IACS.
In the case of Comparative Example 4 in which the workability of cold rolling after aging treatment was less than 40%, the tensile strength was less than 800 MPa.

In the case of Comparative Example 5 in which the contents of Ni and Si exceeded the specified range, the conductivity was less than 30% IACS.
In the case of Comparative Example 7 in which one or more selected from the group of Mg, Fe, P, Mn, Co and Cr was contained in a total amount of more than 0.8% by mass, the conductivity was less than 30% IACS.

In the case of Comparative Example 8 in which the aging temperature was less than 625 ° C. and Comparative Example 10 in which the aging time was less than 1 hour, sub-aging was achieved and the tensile strength was less than 800 MPa.
In the case of Comparative Example 9 in which the aging temperature exceeded 625 ° C. and Comparative Example 11 in which the aging time exceeded 50 hours, overaging occurred and the tensile strength was less than 800 MPa. In addition, Ni—Si-based precipitates were remarkably precipitated due to overaging, the brightness L ^* became less than 50, the amount of smut generated increased, and the adhesion to the resin was inferior.

Claims (3)

A Cu—Ni—Si copper alloy strip containing 1.5 to 4.5% by mass of Ni and 0.4 to 1.1% by mass of Si, and composed of the balance Cu and unavoidable impurities.
The conductivity is 30% IACS or more, the tensile strength is 800 MPa or more, and
After immersing in a 40 wt% nitric acid aqueous solution at room temperature for 10 seconds, a Cu—Ni—Si copper alloy having an L ^* a ^* b ^* color-based brightness L ^* specified in JIS-Z8781: 2013 is 50 to 75. Article. The Cu—Ni—Si-based copper alloy strip according to claim 1, further containing 0.005 to 0.8% by mass in total of one or more selected from the group of Mg, Fe, P, Mn, Co and Cr. Hot-rolled Cu-Ni-Si copper alloy strip ingot containing 1.5 to 4.5% by mass of Ni and 0.4 to 1.1% by mass of Si, and consisting of the balance Cu and unavoidable impurities. After cold rolling, solution treatment, aging treatment at 375-625 ° C. for 1 to 50 hours are performed in this order, and cold rolling is performed after aging treatment at a processing degree of 40% or more.
After the solution treatment, the material before the aging treatment is immersed in a 40 wt% nitric acid aqueous solution for 10 seconds at room temperature, and then the lightness L ^* in the L ^* a ^* b ^* color system specified in JIS-Z8781: 2013 ^. The method for producing a Cu—Ni—Si-based copper alloy strip according to claim 1 or 2 , wherein the solution treatment is adjusted so that the color is 40 to 70 when measured.