JP4950734B2 - High strength and high conductivity copper alloy with excellent hot workability - Google Patents

Description

  The present invention relates to a high-strength, high-conductivity copper alloy for electronic device parts, and particularly excellent in hot workability and bending in a small and highly integrated copper alloy for semiconductor device leads and terminal connectors. The present invention relates to a copper alloy for electronic parts that is particularly excellent in strength, conductivity and thermal conductivity without impairing workability.

Copper and copper alloys are materials widely used for electronic parts such as connectors and lead terminals and flexible circuit boards. High-functionality and miniaturization of information equipment due to the rapid development of IT.・ Further improvements in properties (strength, bending workability, conductivity) are required in response to thinning.
In addition, with the high integration of ICs, many semiconductor elements with high power consumption are used, and the lead frame material of semiconductor devices has a good heat dissipation (conductivity) such as Cu-Ni-Si or Cu. Precipitation alloys such as -Fe-P, Cu-Cr-Sn, and Cu-Ni-P have come to be used.
Patent Document 1 reports an alloy having strength, conductivity, and stress relaxation resistance by adjusting the amounts of Ni, P, and Mg components in a Cu-Ni-P alloy.
JP 2000-273562 A

Generally, in the casting of a copper alloy, for example, continuous or semi-continuous casting, heat is rapidly removed by a mold, and the inside solidifies over time except for a few mm of the surface layer of the lump. For this reason, in the cooling process during solidification and after solidification, alloy elements contained exceeding the limit of the solid solubility in the Cu matrix at room temperature are crystallized or precipitated in the crystal grain boundaries and crystal grains. In particular, since the Ni-P compound crystallized or precipitated at the crystal grain boundary of the Cu-Ni-P alloy has a lower melting point than that of the parent phase Cu, the Ni-P compound is caused by stress or external force generated due to uneven strain during solidification. Destruction occurs at the portion of the -P compound. Even during hot rolling, cracking occurs during hot rolling when the Ni-P compound is softened or liquidified. As described above, the Cu—Ni—P-based alloy has a problem that a crack at the time of casting or a crack at the time of hot working occurs, but Patent Document 1 is not aware of such a problem.
The object of the present invention is to prevent cracks that occur during the casting process or during heating or hot working in the hot working process, and have good hot workability and high strength and high conductivity without impairing bending workability. An object of the present invention is to provide a copper alloy for electronic parts made of a Cu-Ni-P-based alloy that exhibits high performance and high thermal conductivity.

The present inventors have conducted research to achieve the above object, and as a result, by adopting the following configuration, Cu having excellent hot workability, excellent strength and conductivity without impairing bending workability. It has been found that a -Ni-P alloy can be obtained.
The present invention includes a copper alloy containing Ni: 0.50% to 1.00% (in the present specification,% representing the component ratio is mass%), P: 0.10% to 0.25%, Ni / P content ratio Ni / P: 4.0 to 5.5, B: 0.005% to 0.070%, O: 0.0050% or less, Fe, Co, Mn, Ti In the copper alloy in which the content of one or more of Zr is 0.05% or less in total, preferably 0.03% or less, and the balance is made of Cu and inevitable impurities, : A, minor axis: b, a: 20 nm to 50 nm and second phase particles having an aspect ratio of a / b: 1 to 5 of all second phase particles contained in the copper alloy It is a high-strength, high-conductivity copper alloy excellent in hot workability characterized by occupying 80% or more in area ratio.
The copper alloy of the present invention may further contain one or more of Sn and In in a total of 0.01% to 1.0%.

  In the present invention, by adding a specific amount of B to the Cu-Ni-P alloy, crystallization or precipitation of the Ni-P compound at the crystal grain boundary is suppressed, thereby improving the high temperature brittleness of the grain boundary. The hot workability can be improved.

Next, the reason for limiting the numerical range of the component composition of the copper alloy in the present invention will be described together with its action.
[Ni content]
Ni dissolves in the alloy and has the effect of ensuring strength, stress relaxation resistance and heat resistance (maintaining high strength at high temperatures), and precipitates a compound with P described later, thereby contributing to an increase in strength of the alloy. . However, if the content is less than 0.50%, the desired strength cannot be obtained. On the other hand, if Ni is contained in excess of 1.00%, the electrical conductivity decreases significantly, and the tensile strength is 650 MPa or more. In addition, high strength and high conductivity with a conductivity of 45% IACS or higher cannot be obtained. Therefore, the Ni content of the alloy of the present invention is 0.50% to 1.00%.
[P amount]
P precipitates a compound with Ni to improve the strength and heat resistance of the alloy. If the P content is less than 0.10%, precipitation of the compound is insufficient, so that the desired strength cannot be obtained. On the other hand, if the P content exceeds 0.25%, the balance of Ni and P content is lost, P in the alloy becomes excessive, the amount of solute P increases, and the decrease in conductivity becomes significant. . Therefore, the P content of the alloy of the present invention is 0.10% to 0.25%.
[Ni / P ratio]
Even if the content of Ni and P is within the above-mentioned limited range, if the content ratio Ni / P of Ni and P deviates from the appropriate stoichiometric composition ratio of the second phase particles, that is, less than 4.0 In this case, the amount of solid solution of P is increased, and when the amount exceeds 5.5, the amount of solid solution of Ni is increased. Therefore, the Ni / P ratio of the alloy of the present invention is 4.0 to 5.5, preferably 4.5 to 5.0.

[B amount]
B suppresses the crystallization or precipitation of the Ni-P compound at the grain boundaries during solidification of the Cu-Ni-P alloy, during the cooling process after solidification, and during heating during hot working, and the hot workability of the alloy. To improve. However, if the content is less than 0.005%, the effect of improving hot workability cannot be obtained. On the other hand, if the content of B exceeds 0.070%, Ni-P-B, BP, etc. This compound occurs during dissolution or coagulation. These B-containing compounds are not solid-dissolved in the Cu matrix by the solution treatment, and therefore the Ni-P compounds precipitated by the aging treatment are reduced, leading to a reduction in the strength of the alloy. Further, compounds such as Ni-P-B and BP remain in the product as inclusions having a size of 5 μm to 50 μm in the product, surface defects of the product, starting points of cracks during bending, Since it becomes a starting point of a defect, it is not preferable. Therefore, the B content of the alloy of the present invention is 0.005% to 0.070% or less, preferably 0.007% to 0.060%.

[Fe, Co, Mn, Ti and Zr amounts]
Fe, Co, Mn, Ti and Zr all easily form compounds with P, and compounds such as Fe-P, Co-P, Mn-P, Ti-P, Zr-P are formed during dissolution and solidification. Further, when these compounds are precipitated by the aging treatment, Ni-P-based precipitates are reduced, and the strength of the alloy is reduced. Therefore, the content of Fe, Co, Mn, Ti and Zr alone or in combination of two or more is 0.05% or less, preferably 0.03% or less in total.

[O amount]
O easily reacts with P and Cu in the alloy, and when present in the alloy in an oxide state (Cu—P—O), the precipitation of Ni and P compounds is hindered, the strength improvement is lowered, and bending workability is reduced. Deteriorates. Therefore, the O content of the alloy of the present invention is 0.0050% or less, preferably 0.0030% or less.

[Sn, In amount]
Both Sn and In have the effect of improving the strength mainly by solid solution strengthening without greatly reducing the conductivity of the alloy. Accordingly, if necessary, one or more of these metals are added. If the total content is less than 0.01%, the effect of improving the strength by solid solution strengthening cannot be obtained, while the total amount is 1.0. When adding more than%, the electrical conductivity and bending workability of the alloy are significantly reduced. For this reason, the amount of Sn and In added individually or in combination of two or more types is 0.01% to 1.0%, preferably 0.05% to 0.8% in total. In the present invention, these elements are intentionally added elements and are not regarded as inevitable impurities.

[Size and area ratio of second phase particles]
The second phase particles of the present invention include precipitates, crystallization products, inclusions and the like. Within the composition range of the present invention, precipitates other than Ni-P-based precipitates usually do not precipitate, and Ni-P-based precipitates can be controlled to a specific size by aging treatment in addition to solution treatment. As other second phase particles, in the present invention, "crystallized substances" (Ni-P, Ni-P-B, etc.) and "inclusions" (Cu-O, Cu-Ni-P-) generated during melting and casting are used. O, Cu—Ni—P—O—B, Cu—S, and the like) may be present, but if they are present, the size of the oxide may exceed 100 nm to 1 μm, and solution treatment and aging may occur. The size within the range of the present invention cannot be controlled even by processing. Therefore, solution treatment is sufficiently performed so that crystallized substances and inclusions do not remain in the alloy, and the addition amount of P, B, etc. is specified to suppress the formation of inclusions, and oxide (inclusion) is generated. In order to suppress this, the O content is specified low. The area ratio C of all second phase particles in the sample in which the crystallized substances and inclusions could not be sufficiently reduced is less than 80%, which is outside the scope of the present invention.

When the major axis of the second phase particle is a (nm) and the minor axis is b (nm), the second phase particle having a before the final cold rolling of less than 20 nm undergoes a rolling process with a working strain η = 2 or more. Then, the second phase particles are re-dissolved in copper, which lowers the conductivity, which is not preferable. Here, the processing strain η is represented by η = ln (t ₀ / t), where t _{0 is} the thickness before rolling and t is the thickness after rolling. On the other hand, the second phase particles having an a of 20 nm or more before the final cold rolling are not easily re-dissolved even in a rolling process having a working strain η = 2 or more, and are present as second phase particles having a thickness of 10 nm or more. The second phase particles of 20 nm or more have little change in size before and after rolling. Particularly, the second phase particles having a major axis a before rolling exceeding 50 nm maintain a major axis exceeding 50 nm after rolling. Since the dispersion interval of the phase particles becomes too large, precipitation strengthening and work strengthening cannot be obtained.
The major axis a and the minor axis b are obtained by cutting the alloy strip before the final cold rolling in a direction perpendicular to the thickness parallel to the rolling direction, and using the image analysis apparatus to analyze the cross-sectional image of the second phase particles having the major axis a of 5 nm or more. It is the average value of each major axis and minor axis of all second phase particles measured for all.
From the above, the preferred size of the second phase particles before the final cold rolling of the alloy of the present invention is that the major axis a is 20 nm to 50 nm.

  In addition, when the aspect ratio of the second phase particles is represented by a / b, when a / b exceeds 5, the second phase particles are re-dissolved in copper when rolling is performed with η = 2 or more. As a result, the conductivity is lowered. Therefore, the aspect ratio a / b of the second phase particles before the final cold rolling is preferably 1 to 5, more preferably 1 to 3.

In order to prevent a decrease in strength and electrical conductivity, the a of the second phase particles after the final cold rolling of the alloy of the present invention is preferably 10 nm to 50 nm and a / b is 1 to 5. However, since it is difficult to make all the second phase particles within the preferable ranges of a and a / b, the ratio of the second phase particles in the range of a and a / b to the total second phase particles. Becomes important. “All second phase particles” refers to all second phase particles having a major axis a of 5 nm or more. Therefore, the ratio of the total area of the second phase particles in the preferable range of a and a / b to the total area of all the second phase particles in the alloy after the aging treatment and before the final cold rolling is expressed as an area ratio C. Then, the area ratio C of the present invention is 80% or more.
The case where the area ratio C is less than 80% is a case where there are many second phase particles in which a exceeds 50 nm or second phase particles less than 20 nm. For example, second-phase particles with a exceeding 50 nm or crystallized products generated during melt casting remain 1000-nm or more Ni-P particles (crystallized products) remaining without being dissolved in the heating or solution treatment before hot rolling. ) Is present in large amounts, the dispersion interval of fine second phase particles having a size of 20 to 50 nm that contributes to the strength improvement is large, so that the desired strength by work hardening in the rolling process cannot be obtained. On the other hand, since the second phase particles having a of less than 20 nm are re-dissolved by rolling, the decrease in conductivity becomes remarkable.

The Cu—Ni—P alloy satisfying the above-mentioned requirements of the present invention is generally used by those skilled in the art for ingot casting, hot rolling, solution treatment, intermediate cold rolling, aging treatment, final cold rolling, strain. In the annealing and the like, it can be produced by appropriately selecting the heating temperature, time, cooling rate, rolling rate and the like. For example, (1) melting and casting, (2) hot rolling, (3) oxide scale removal, (4) cold rolling (thickness adjustment), (5) solution treatment, (6) cold rolling, ( 7) Manufactured by repeating or omitting some steps in the order of aging treatment, (8) surface cleaning treatment (polishing and pickling), (9) cold rolling (final), and (10) strain relief annealing. To do.
Preferably, the temperature and time during the aging treatment are appropriately adjusted so that the work strain η = 0 to about 1.4 in the final cold rolling.

Manufacture of samples Mainly made of electrolytic copper or oxygen-free copper, nickel (Ni), 15% P—Cu master alloy, 2% B—Cu (B), tin (Sn), indium (In), 10% Fe— Cu (Fe), 10% Co—Cu (Co), 25% Mn—Cu (Mn), sponge titanium (Ti) and sponge zirconium (Zr) are used as auxiliary materials in a high frequency melting furnace in a vacuum or argon atmosphere. And was cast into a 45 × 45 × 90 mm ingot. Ingots were subjected to a hot rolling test, and ingots that were not cracked by hot rolling were subjected to hot rolling and solution treatment, aging treatment, intermediate cold rolling, aging treatment, final cold rolling, and strain relief annealing. It implemented in order and was set as the flat plate of thickness 0.15mm. Various test pieces of the obtained plate material were collected and tested, and “strength” and “conductivity” were evaluated.

Evaluation of hot workability of the ingot “hot workability” was evaluated by hot rolling. That is, the ingot was cut into 45 × 45 × 25 mm, heated to 850 ° C. for 1 hour, and then subjected to a hot rolling test in three passes from a thickness of 25 mm to 5 mm. The case where cracks were visually observed on the surface and edge of the sample after hot rolling was defined as “cracked”, and the case where the surface and edge were not cracked and smooth was defined as “no crack”.
In the present invention, “excellent in hot workability” means “no crack” in the above evaluation.
About physical property evaluation "strength" of a test piece, it carried out using the No. 13 B test piece by the tensile test prescribed | regulated to JISZ2241, and measured the tensile strength.
In the present invention, high strength means that the tensile strength is 650 MPa or more in the above evaluation.
“Conductivity” was measured by measuring the electrical resistance of a test piece using a four-terminal method and expressed in% IACS.
In the present invention, high conductivity means that the conductivity is 45% IACS or more in the above evaluation.
“Bending workability” was evaluated by a 90 ° W bending test. The test was performed in accordance with CES-M0002-6, and bending was performed 90 degrees with a load of 50 kN using an R-0.1 mm jig. In the evaluation of the bent portion, the state of the surface of the central mountain was observed with an optical microscope. The bending axis was set at right angles to the rolling direction (Good way).

Evaluation of Second Phase Particles The alloy strip before the final cold rolling is cut at a right angle to the thickness parallel to the rolling direction, and the second phase particles in the cross section are observed in 10 fields using a scanning electron microscope and a transmission electron microscope. did. When the size of the second phase particles is 5 to 50 nm, the field of view is about 500,000 to 700,000 times (approximately 1.4 × 10 ^{10 to} 2.0 × 10 ¹⁰ nm ² ), and when the size is 100 to 2000 nm, 50,000 Images were taken with a field of view of about 100,000 to 100,000 times (approximately 1.0 × 10 ^{13 to} 2.0 × 10 ¹³ nm ² ). Using the image of the photographed photograph, the major axis a, the minor axis b, and the area of each of the second phase particles having a major axis a of 5 nm or more were measured using an image analyzer (trade name Luzex, manufactured by Nireco Corporation). Randomly select 100 particles from these second phase particles to obtain the average major axis a _ta and the minor axis average b _{ta of} all the second phase particles and the average aspect ratio a _ta / b _{ta determined} from them. a, minor axis b, and aspect ratio a / b. The total area of all the second phase particles having a major axis “a” of 5 μm or more was defined as the total area of all the second phase particles. The ratio of the total area of the second phase particles having a major axis a of 10 nm to 50 nm and an aspect ratio a / b of 1 to 5 was defined as an area ratio C (%) with respect to the total area of all the second phase particles.
In addition, by the final cold rolling (usually processing strain η = 2 or more), the second phase particles having a major axis of 20 nm or less or the second phase particles having a major axis of more than 20 nm but an aspect ratio exceeding 3 are dissolved. However, it was confirmed that the second phase particles having an aspect ratio of 1 to 3 of 20 nm or more maintain their major axis, minor axis and aspect ratio even after the final cold rolling. Further, the area ratio C of the second phase particles hardly changed even after the final cold rolling because the second phase particles exceeding 200 nm were not dissolved.

Examples of the high-strength, high-conductivity copper alloy excellent in hot workability according to the present invention will be described with reference to the copper alloys having the component compositions shown in Table 1 together with comparative examples. Alloy Examples 1 to 9 of the present invention had excellent strength and electrical conductivity without cracking during hot rolling.
On the other hand, when the results up to Comparative Examples 10 to 27 were examined, in Comparative Examples 10 to 13 there was no addition of B or less than the specified amount, so cracking occurred during hot rolling. In Comparative Example 14, the total addition amount of Sn and In exceeded 1.0%, and in Comparative Example 15, the total addition amount of Sn exceeded 1.0%, resulting in a decrease in conductivity. In Comparative Example 16, since the Ni / P ratio deviates high, the amount of Ni dissolved increases and the conductivity decreases, and the amount of second phase particles is small, so the strength is low. In Comparative Example 17, since the Ni / P ratio deviated from an appropriate composition ratio, the amount of dissolved P increased and the conductivity decreased. Comparative Example 18 has low strength because the addition amounts of Ni and P deviate from the range defined by the present invention. In Comparative Example 19, the amount of Ni was different, and in Comparative Example 20, the amount of P was outside the range defined by the present invention, resulting in a decrease in conductivity. In Comparative Example 21, since the O content exceeds 0.050%, an oxide of Cu-PO is generated when dissolved, the amount of second phase particles is reduced, the strength is low, and the bending workability is inferior. . In Comparative Example 22, since the content of B deviates from the range defined by the present invention, Ni-P-B, BP, and the like are generated and crystallized during melting and casting, so that the amount of second phase particles is increased. Decrease, strength and conductivity are low, and bending workability is also poor. In Comparative Examples 23 and 24, since the contents of Fe, Co, Mn, Ti and Zr deviate from the range defined by the present invention, the amount of the second phase particles was reduced by the formation of compounds by these elements and P. Decrease and strength is low. In Comparative Example 25, since the average major axis of the second phase particles deviates from the range defined by the present invention, the strength increase due to cold rolling cannot be obtained, and the strength is low. In Comparative Examples 26 and 27, the average major axis of the second phase particles deviated from the range defined by the present invention, and in Comparative Example 27, the aspect ratio also deviated. Is low.

Claims (2)

In mass ratio, Ni: 0. 61 % to 0.93 %, P: 0.15 % to 0.19 %, Ni / P content ratio Ni / P: 4.0 to 5.5, and B: 0.021 % ~ 0.041 %, O: 0.0012% to 0.0030% , and the total content of one or more of Fe, Co, Mn, Ti and Zr is 0.05% or less with the balance being Cu and In the copper alloy composed of inevitable impurities, the size of the second phase particles is a: 20 nm to 50 nm when the major axis: a and minor axis: b, and the second phase particle aspect ratio a / b: 1 A high-strength, high-conductivity copper alloy excellent in hot workability, wherein the second phase particles 5 occupy 80% or more in the area ratio of all second-phase particles contained in the copper alloy. The high-strength, high-conductivity copper alloy excellent in hot workability according to claim 1, comprising one or more of Sn and In in a total amount of 0.21 % to 0.5 %.