JP5101149B2 - 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.
Therefore, 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-based 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 and during the heating or hot working in the hot working process, which is a problem of the Cu-Ni-P alloy, and has good hot workability. Thus, an object of the present invention is to provide a copper alloy for electronic parts made of a Cu-Ni-P-Mg alloy that exhibits high strength, high conductivity, and high thermal conductivity without impairing bending workability.

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-Mg alloy can be obtained.
In the copper alloy according to the present invention, Ni: 0.50% to 1.00% (hereinafter,% representing the component ratio is mass%), P: 0.10% to 0.25%, Mg: 0.01 to Containing 0.20%, Ni / P content ratio Ni / P: 4.0-5.5 and B: 0.005% -0.070%, 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, short diameter: b, the second phase particles (A) having an aspect ratio a / b of 2 to 50 and a short diameter b of 10 to 25 nm, and the second phase particles (A) The sum of the second phase particles (B) having an aspect ratio of less than 2 and a major axis a of 20 to 50 nm is the surface of all second phase particles in the copper alloy. Is a high strength and high conductivity copper alloy having excellent hot workability, characterized in that the relative total 80% or more.
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—Mg alloy, crystallization or precipitation at the crystal grain boundary of the Ni—P compound is suppressed, thereby improving the high temperature brittleness of the grain boundary. Thus, 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 750 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%.

[Mg amount]
Mg precipitates a compound with Ni and P to improve the strength and heat resistance of the alloy. Further, when a Cu—Ni—P-based alloy is manufactured without adding Mg in the method described later, second-phase particles having an aspect ratio a / b of 1 to 5 close to a granular shape are obtained, whereas when Mg is added. Fibrous second phase particles having an aspect ratio a / b of 2 to 50 are obtained. In this case, higher strength can be achieved compared to a Cu—Ni—P alloy having the same amount of Ni and P. Furthermore, the effect is greater than the increase in strength obtained when Mg is dissolved.
However, when the Mg content is less than 0.01%, desired strength and heat resistance cannot be obtained. On the other hand, if the Mg content exceeds 0.20%, the workability during hot rolling is remarkably lowered and the conductivity is significantly lowered. Further, when the second phase particles are easily coarsened and the size is in the range of the present invention, that is, (A) major axis: a and minor axis: b, the aspect ratio a / b is 2 to 50 and the minor axis b. Is preferably 10 to 25 nm, or (B) the second phase particles deviate from the aspect ratio of less than 2 and the major axis a is 20 to 50 nm, and the total area ratio of (A) and (B) is reduced. Absent. Accordingly, the Mg content of the alloy of the present invention is 0.01% to 0.20%, preferably 0.02 to 0.15%.

[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 or more and 5.5 or less, preferably 4.5 to 5.0.

[B amount]
B suppresses the crystallization or precipitation of the Ni-P compound at the grain boundary during the solidification of the Cu-Ni-P-Mg based alloy, during the cooling process after solidification, and during the heating during hot working. Improve processability. 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, the Ni—P—Mg-based second phase particles are decreased, and the strength of the alloy is decreased. 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.

[Zn, Sn, In amount]
Zn, Sn and In all 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 Zn, 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, no precipitate other than the Ni—P—Mg based precipitate is usually deposited, and the Ni—P—Mg based precipitate can be controlled to a specific size by solution treatment and aging treatment. . As other second phase particles, in the present invention, “crystallized substances” (Ni—P, Ni—P—Mg, Ni—P—B, Ni—P—B—Mg, etc.) generated during melting and casting, Inclusions "(Cu-O, Cu-O-Mg, Cu-Ni-PO, Cu-Ni-PO-Mg, Cu-Ni-PO-B, Cu-Ni-PO- Oxides and sulfides such as B-Mg, Cu-S, and Cu-S-Mg) may be present, but when these are present, the size thereof exceeds 100 nm to 1 μm, and is obtained by solution treatment and aging treatment. Cannot be controlled within the range of the present invention. 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 particles in the alloy of the present invention is classified according to the aspect ratio a / b where a (nm) is the major axis and b (nm) is the minor axis, the alloy has a / b = 2 to 2 before the final cold rolling. It is possible to generate two kinds of needle-like and / or fibrous second-phase particles (A) having a large aspect ratio of about 50 and granular second-phase particles (B) having an a / b of less than 2. It is. By making rolling deformation strain η before aging treatment less than 0.4, preferably less than 0.1, needle-like and fibrous second phase particles (A), working strain η before aging treatment is 0.4 or more. In this way, granular second phase particles (B) are produced. In the vicinity of the rolling processing degree η = 0.4 before the aging treatment, the second phase particles (A) and the second phase particles (B) are mixed to some extent. However, when the processing degree is less than 0.4, the second phase particles (A) are mostly in the second phase. When the degree of processing is 0.4 or more, most of the particles become the second phase particles (B). It is the working strain eta, the plate thickness before rolling t _0, when the plate thickness after rolling was t, is expressed by _{η = ln (t 0 / t} ).

The reason for defining the size of the second phase particles is as follows. The second phase particles having a minor axis b of less than 10 nm before the final cold rolling are subjected to final cold rolling with a processing strain η = 2 or more, and the second phase particles are broken and decomposed to resolidify in copper. It melts and lowers the conductivity, which is not preferable. On the other hand, the second phase particles having a minor axis of 10 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 diameter of 10 nm or more. In particular, the second phase particles having a minor axis b of 20 nm or more have little change in size before and after rolling, and the second phase particles are difficult to break and dissolve by cold rolling. On the other hand, the second phase particles whose major axis a before rolling exceeds 50 nm and whose minor axis exceeds 25 nm maintain their size after rolling, but because the volume of each second phase particle is large, Since the dispersion interval of the second phase particles becomes too large, precipitation strengthening and work strengthening cannot be obtained.
The major axis a and the minor axis b are all the second phase particles whose major axis a is 5 nm or more using an image analysis device by cutting the alloy strip before the final cold rolling in parallel to the rolling direction and at a right angle to the thickness. It is the average value of each major axis and minor axis of all second phase particles measured for.
From the above, the second phase particles before the final cold rolling of the alloy of the present invention are added to the second phase particles (A) having an aspect ratio a / b of 2 to 50 and a minor axis b of 10 to 25 nm. The second phase particles (B) having an aspect ratio a / b of less than 2 and a major axis a of 20 to 50 nm are included.

  In order to make the second phase particles before the final cold rolling of the copper alloy of the present invention have an aspect ratio a / b of 2 to 50 and a minor axis b of 10 to 25 nm, the rolling strain η before aging treatment is set to The temperature, time, and the like during the aging treatment are appropriately adjusted to be less than 0.4, preferably less than 0.1. In order to set the aspect ratio a / b to less than 2 and the major axis a to 20 to 50 nm, the processing strain η before the aging treatment is set to 0.4 or more, preferably about 1.5, and the temperature during the aging treatment is set. And adjust the time accordingly.

However, since it is difficult to make all the second phase particles within the preferable ranges of a and a / b, the second phase particles (A) and (B ) To the total second phase particles having a major axis a of 5 nm or more. Therefore, when the ratio of the total area of the second phase particles (A) and (B) in which a, b, and a / b are in a preferable range with respect to the total area of all the second phase particles in the alloy is an area ratio C. 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 second phase particle in which a is greater than 50 nm and the minor axis b is greater than 25 nm, a second phase particle having a major axis a of less than 20 nm, and a second phase particle having a minor axis b of less than 10 nm. This is a case where there are many phase particles and any of the second phase particles having an aspect ratio a / b exceeding 50. For example, the second-phase particles in which a exceeds 50 nm and the minor axis b exceeds 25 nm and the crystallized product generated during melt casting remain in a form of Ni—over 1000 nm that remains without being dissolved by hot rolling or solution treatment. When many P-Mg-based particles (crystallized substances) are present, the number of fine second-phase particles in the range defined by the present invention that contributes to strength improvement is small, and the dispersion interval of the second-phase particles is large. The desired strength cannot be obtained by work hardening of the rolling process. On the other hand, the second phase particles having a major axis “a” of less than 20 nm or a minor axis “b” of less than 10 nm are re-dissolved by rolling, so that a desired conductivity cannot be obtained.

The copper alloy of the present invention comprises the second phase particles (A) having an aspect ratio a / b of 2 to 50 and a minor axis b of 10 to 25 nm before the aging treatment and before the final cold rolling, and the aspect ratio a / In order that the sum total of the second phase particles (B) in which b is less than 2 and the major axis a is 20 to 50 nm accounts for 80% or more with respect to the total area of all the second phase particles in the copper alloy, It is preferable to adjust the temperature and time during the aging treatment as appropriate by setting the rolling strain η before treatment to about 0 to 1.5.
The Cu—Ni—P—Mg based alloy that satisfies 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, and final cold rolling. In the strain relief 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. The rolling process before the aging treatment corresponds to the above (6). Note that (6) is omitted when the processing strain η = 0 before the aging treatment. In the evaluation of the second phase particles of the present invention, (7) the material after the aging treatment is used as a sample.

Manufacture of samples Mainly made of electrolytic copper or oxygen-free copper, nickel (Ni), 15% P—Cu master alloy, 10% Mg—Cu master alloy (Mg), 2% B—Cu master alloy (B), tin (Sn), indium (In), 10% Fe—Cu master alloy (Fe), 10% Co—Cu master alloy (Co), 25% Mn—Cu master alloy (Mn), sponge titanium (Ti) and sponge zirconium (Zr) was used as an auxiliary material, melted in a vacuum or argon atmosphere in a high-frequency melting furnace, and 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 750 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 a right angle 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). 100 of the second phase particles having a major axis a of 5 nm or more are selected at random, and the aspect ratio a / b is 2 to 50 and the minor axis b is 10 to 25 nm with respect to the total area of 100 selected. The ratio of the total area of the second phase particles (B) having the area of the second phase particles (A) and the aspect ratio a / b of less than 2 and the major axis a of 20 to 50 nm was calculated as the area ratio C (%). .
In addition, by the final cold rolling (usually processing strain η = 2 or more), the Ni—P—Mg second phase particles in which the minor axis b of the second phase particles before cold rolling is smaller than 10 nm are dissolved. Although not observed, it was confirmed that the second phase particles having a minor axis b of 10 nm or more maintain their major axis, minor axis and aspect ratio even after the final cold rolling. Similarly, the area ratio C of the second phase particles hardly changes even after the final cold rolling.

Examples of high-strength, high-conductivity copper alloys excellent in hot workability according to the present invention are evaluated for each hot-rolling workability, second phase particles, and properties of copper alloys having the composition shown in Table 1. A result is shown with a comparative example. If it is in the range of a = 20-1250, b = 10-25, and a / b = 2-50, it corresponds to a 2nd phase particle (A), a = 20-50, b = 10-50, and a / If it is in the range of b = 1-2, it corresponds to a 2nd phase particle (B).
Alloy Examples 1 to 11 of the present invention had excellent strength and conductivity without cracking during hot rolling. On the other hand, when the results of Comparative Examples 12 to 35 were examined, in Comparative Examples 12 to 16, there was no addition of B or less than the specified amount, and therefore cracking occurred during hot rolling. In Comparative Example 17, the total addition amount of Sn and In exceeds 1.0%, and in Comparative Example 18, the total addition amount of Sn exceeds 1.0%. Workability was inferior. In Comparative Example 19, cracks occurred during hot rolling because the added amount of Mg deviated from the range defined by the present invention. Comparative Example 20 has a lower strength than that of Inventive Example 2 having the same chemical composition except Mg, because the added amount of Mg deviates from the range defined by the present invention. In Comparative Example 21, since the Ni / P ratio is low, the amount of dissolved P increases and the conductivity is low. Comparative Example 22 has low strength because the amounts of Ni and P added deviate from the range defined by the present invention. In Comparative Example 23, the Ni content and the Ni / P ratio deviated from the range defined by the present invention, so that the conductivity decreased. In Comparative Example 24, the amount of P deviated from the range defined by the present invention, and the Ni / P ratio deviated from the range defined by the present invention.

In Comparative Example 25, since the content of O exceeds 0.050%, an oxide of Cu—P—O is generated when dissolved, the amount of second phase particles is reduced, the strength and conductivity are low, and bending processing is performed. Also inferior.
In Comparative Example 26, 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 at the time of 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 27 to 30, since the content of one or more of Fe, Co, Mn, Ti, and Zr deviates from the range defined by the present invention in total, the second phase particles are reduced, and Fe, Co, Crystallized substances of Mn, Ti, Zr and P and second phase particles were coarsely formed, and the evaluation results of the second phase particles were out of the range defined by the present invention, so the strength was lowered.
In Comparative Example 31, the short diameter b of the second phase particles deviated from the range defined by the present invention, so the conductivity was low. In Comparative Example 32, since the minor axis b of the second phase particles deviates from the range defined by the present invention, the strength is low. In Comparative Example 33, the major axis “a” and the minor axis “b” of the second phase particles deviate from the range defined by the present invention, so the strength and conductivity are low. In Comparative Examples 34 and 35, the major axis “a” and minor axis “b” of the second phase particles deviated from the range defined by the present invention.

Claims (2)

Ni: 0.55 % to 0.95 % in mass ratio, P: 0.12 % to 0.21 %, Mg: 0.02% to 0.14 %, Ni and P content the ratio Ni / P: 4.0 to 5.5 and at, B: 0.025% ~ 0.061% , O: a 0.0015% ~0.0032%, Fe, Co , Mn, Ti, Zr In the copper alloy in which the content of one or more of the total is 0.05% or less and the balance is made of Cu and inevitable impurities, the size of the second phase particles is set to a major axis: a and a minor axis: b. The second phase particles have an aspect ratio a / b of 2 to 50 and a short diameter b of 10 to 25 nm, and the second phase particles have an aspect ratio of less than 2 and a long diameter a of 20 to 50 nm. The sum of the two-phase particles accounts for 80% or more of the total area of all the second-phase particles in the copper alloy. Hot workability excellent high strength and high conductivity copper alloy to. 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 amount of 0.42 % to 0.73 %.