JPWO2009041194A1 - High strength and high conductivity copper alloy with excellent hot workability - Google Patents

Abstract

Provided is a copper alloy for electronic parts made of a Cu-Ni-P-based alloy that exhibits good hot workability and exhibits high strength, high electrical conductivity, and high thermal conductivity without impairing bending workability. In terms of mass ratio, Ni: 0.50% to 1.00%, P: 0.10% to 0.25%, Ni / P content ratio Ni / P: 4.0 to 5.5 And Cr: 0.03% to 0.45%, O: 0.0050% or less, and the total content of one or more of Fe, Co, Mn, Ti, and Zr is 0.05% or less. In a copper alloy, preferably 0.03% or less, and the balance being Cu and inevitable impurities, the size of the Ni-P-based second phase particles is a: 20 nm when the major axis is a and the minor axis is b. A copper alloy that occupies 80% or more in terms of the area ratio of all second phase particles in which the second phase particles having an aspect ratio of a / b: 1 to 5 are included in the copper alloy.

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

In general, in the casting of a copper alloy, for example, continuous or semi-continuous casting, the ingot is heat-extracted by a mold, and the inside solidifies with some time except for a few mm of the surface layer of the ingot. At this time, in the cooling process during solidification and after solidification, alloy elements contained exceeding the limit of solid solution 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-based compound crystallized or precipitated at the crystal grain boundary of the Cu-Ni-P-based alloy has a melting point lower than that of the parent phase Cu, due to stress or external force generated due to non-uniform strain during solidification, Breakage occurs in the Ni-P compound portion. Further, even during hot rolling, cracking occurs during hot rolling when the Ni-P compound softens or becomes liquid phase. 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 rolling occurs, but Patent Document 1 does not recognize such a problem.
The object of the present invention is to prevent cracks that occur during heating or hot working in the casting process or hot working process, and have good hot workability and high strength and high conductivity without impairing bending workability. And a copper alloy for electronic parts made of a Cu-Ni-P alloy exhibiting 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, Cr: 0.03% to 0.45%, 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 the second phase particles having an aspect ratio of a / b: 1 to 5 are 80% in terms of the area ratio of all the second phase particles contained in the copper alloy. It is a high-strength, high-conductivity copper alloy excellent in hot workability characterized by occupying the above.
The copper alloy of the present invention may further contain one or more of Sn and In in a total of 0.01% to 1.00%.

  In the present invention, by adding a specific amount of Cr 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 (high strength maintenance at high temperatures), and precipitates a compound with P, which will be described later, thereby contributing to an increase in the strength of the alloy. To do. 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 decrease in conductivity becomes significant, 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 improves heat resistance and precipitates a compound with Ni to improve the strength 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 or less, preferably 4.5 to 5.0.

[Cr content]
In general, when the cooling rate during solidification of a Cu—Ni—P alloy is slow, for example, when the cooling rate from 1100 ° C. to 950 ° C. is less than 30 ° C./min, the Ni—P compound is aggregated and coarsened at the grain boundaries. It is not preferable because it crystallizes with crystallization.
Cr suppresses crystallization or precipitation of the Ni-P compound at the grain boundary during the solidification of the Cu-Ni-P-based alloy, during the cooling process after solidification, and during hot working, thereby hot working the alloy. Improve sexiness. However, if the content is less than 0.03%, the effect of improving hot workability cannot be obtained. On the other hand, if the Cr content exceeds 0.45%, Ni—P—Cr, Cr—P, etc. This compound is generated during dissolution or solidification, and a crystallized product of Cr is generated. These Cr-containing compounds and crystallized substances are not solid-dissolved in the Cu matrix by the solution treatment, so that the Ni—P compounds precipitated by the aging treatment are reduced, and the strength of the alloy is reduced. Further, compounds such as Ni—P—Cr and Cr—P remain in the product as inclusions having a major axis of 5 μm or more, and surface defects of the product, starting points of cracks during bending, and defects during plating processing. Since it becomes a starting point, it is not preferable. Therefore, the Cr content of the alloy of the present invention is 0.03% to 0.45%, preferably 0.05% to 0.30%.

[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 second phase particles 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, the second phase particles other than the Ni-P-based second phase particles usually do not precipitate, and the Ni-P-based second phase particles have a specific size in the aging treatment in addition to the solution treatment. You can control it. As other second phase particles, in the present invention, “crystallized substances” (Ni—P, Ni—P—Cr, etc.) and “inclusions” (Cu—O, Cu—Ni—P—) generated during melting and casting are used. O, Cu-Ni-P-Cr-O, Cu-S, and the like) may be present, but when they are present, the size thereof exceeds 100 nm to 1 μm, and solution treatment and aging The size within the range of the present invention cannot be controlled even by processing. Therefore, in order to prevent the formation of inclusions by sufficiently performing solution treatment so as not to leave crystallized substances and inclusions in the alloy, the amount of addition of P, Cr, etc. is specified, and oxides (inclusions) In order to suppress the formation, the O content is specified to be low. The area ratio C of all the second phase particles in the sample in which the crystallized substances and inclusions could not be sufficiently reduced becomes 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 processing strain η = 2 or more, and are present as second phase particles of 20 nm or more. Contributes to strengthening. However, in the second phase particles having a major axis a of more than 50 nm before rolling, it is difficult to re-dissolve after rolling, and the size thereof is maintained. Therefore, the dispersion interval of the second phase particles in the alloy becomes too large. The processing strengthening effect cannot be obtained.
The major axis a and the minor axis b are obtained by cutting the alloy strip before the final cold rolling parallel to the rolling direction at a right angle to the thickness, and using the image analysis apparatus for the sectional image, the major axis a is 5 nm or more of the second phase particles. 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 20 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 the 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 degree of work η = 0 to 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 (P), 10% Cr—Cu master alloy (Cr), 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, and vacuum is used in a high-frequency melting furnace. It melt | dissolved in the inside or argon atmosphere, and casted to the ingot of 45x45x90 mm. 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 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.
Evaluation of Physical Properties of Test Pieces “Strength” was measured using a No. 13 B test piece by a tensile test specified in JIS Z 2241, and the tensile strength was measured.
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 Ni-P System Second Phase Particles The alloy strip before the final cold rolling is cut parallel to the rolling direction at a right angle to the thickness, and the second phase particles having a cross section are obtained using a scanning electron microscope and a transmission electron microscope. 10 fields of view were observed. 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 50 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 20 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, the final cold rolling (usually processing strain η = 2 or more) causes Ni—P-based second phase particles having a major axis of 20 nm or less or second phase particles having a major axis of more than 20 nm but an aspect ratio of more than 5 to be solid. Although it melts, it was confirmed that the second phase particles having an aspect ratio of 1 to 5 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 was hardly changed even after the final cold rolling because the second phase particles exceeding 20 nm were not re-dissolved by rolling.

  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 8 of the present invention had excellent strength and conductivity without cracking during hot rolling. On the other hand, when the results of Comparative Examples 9 to 26 were examined, in Comparative Examples 9 to 12 there was no addition of Cr or less than the specified amount, so cracking occurred during hot rolling. In Comparative Example 13, the total addition amount of Sn and In exceeds 1.0%. In Comparative Example 14, the total addition amount of In exceeds 1.0%. It was inferior in nature. In Comparative Example 15, 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 16, since the Ni / P ratio deviates from an appropriate composition ratio, the amount of dissolved P increases, resulting in a decrease in conductivity and low strength. Comparative Example 17 has low strength because the addition amounts of Ni and P deviate from the range defined by the present invention. In Comparative Example 18, the amount of Ni was different, and in Comparative Example 19, the amount of P was significantly out of the range defined by the present invention, resulting in a decrease in conductivity. In Comparative Example 20, since the content of O exceeds 0.050%, an oxide of Cu-PO is generated when dissolved, the amount of Ni-P-based second phase particles is reduced, and the strength is low. Bending workability is inferior. In Comparative Example 21, since the content of Cr deviates from the range defined by the present invention, Ni—P—Cr, Cr—P, etc. are produced and crystallized during melting / casting. Two-phase particles are reduced, strength and conductivity are low, and bending workability is also poor. In Comparative Examples 22 and 23, the contents of Fe, Co, Mn, Ti and Zr deviate from the range defined by the present invention. Two-phase particles are reduced and the strength is low. In Comparative Example 24, since the average major axis of the Ni-P-based second phase particles deviates from the range defined by the present invention, the area ratio C of the second phase particles having a major axis of 20 to 50 nm and an aspect ratio of 1 to 5 is zero. Thus, the strength cannot be increased by cold rolling, and the strength is low. In Comparative Examples 25 and 26, since the average major axis of the Ni-P-based second phase particles deviated from the range defined by the present invention, the area ratio C was less than 80%, and the Ni-P-based second phase was obtained by cold rolling. Particles are solid solution and conductivity is low.

Claims (2)

  In terms of mass ratio, Ni: 0.50% to 1.00%, P: 0.10% to 0.25%, Ni / P content ratio Ni / P: 4.0 to 5.5 And Cr: 0.03% to 0.45%, O: 0.0050% or less, and the total content of one or more of Fe, Co, Mn, Ti, and Zr is 0.05% or less. In the copper alloy consisting of Cu and inevitable impurities, the size of the second phase particles is as follows: a: 20 nm to 50 nm and aspect ratio a / b: 1 when the major axis is a and minor axis is b A high-strength, high-conductivity copper alloy excellent in hot workability, characterized in that the second phase particles of 5 or less occupy 80% or more in the area ratio of all the second phase particles contained in the copper alloy.   The high-strength, high-conductivity copper alloy excellent in hot workability according to claim 1, wherein one or more of Sn and In are contained in a total of 0.01% to 1.0%.