JP2002194461A - Copper alloy for lead frame and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Problem] High stiffness copper for lead frame with reduced "burrs" and "blurrs" generated by punching, reduced occurrence of sticking at islands and leads, and improved flatness. Provide alloy. Ni: 0.1% (% by mass, the same applies hereinafter) or more and less than 0.5%, Sn: more than 1.0% and less than 2.5%,
Zn: more than 1.0% and 15% or less, Fe: 0.001%
0.1% or less, Mg: 0.0001% or more and 0.02 or less
% Or less, P: 0.0005% or more and less than 0.05% and S
i: One or both of 0.0005% or more and less than 0.05%, 0.0005% or more and less than 0.05%, S:
0.0005% or more and 0.003% or less, C: 0.000
5% or less, O: 0.005% or less, and H: 0.0002% or less, with the balance being Cu and unavoidable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transistor,
More particularly, the present invention relates to a copper alloy for a lead frame used for consumer and industrial electronic components having excellent stamping workability and stiffness characteristics, and a method for producing the same.

[0002]

2. Description of the Related Art Copper and copper alloys are mechanical properties such as tensile strength and elongation, physical properties such as electrical conductivity and thermal conductivity, press formability, moldability such as etching properties, plating property, bonding. It is widely used as a lead frame material for transistors, ICs, and LSIs because of its excellent secondary characteristics such as resistance and corrosion resistance. C102 (OFC), C19210 (Cu-0.1
Fe-0.03P), C151 (Cu-0.02Zr)
For applications requiring strength and electrical conductivity, C194 (Cu-
2.3Fe-0.03P-0.15Zn), Cu-Ni
-Si-based (Cu-3.2Ni-0.7Si-0.2Zn
For applications requiring higher strength, use Cu-Ni-S
i-Sn type (Cu-3.2Ni-0.7Si-0.2Z)
n-1.25Sn), C725 (Cu-9.2Ni-
2.3Sn) is used.

In response to recent demands for miniaturization of various electric and electronic devices and improvement in mounting density, transistors, ICs, and LSs have been developed.
Various types of lead frames used for electronic components such as I have been put to practical use, and lead pitch has been reduced and thinned, and required characteristics have been more sophisticated. For example, the thickness of the lead frame is 0.1%, which has conventionally been the mainstream.
Those having a diameter of 25 mm to 0.1 to 0.2 mm are frequently used, and those having a diameter of 0.08 mm are also being put to practical use.

When the thickness of the lead frame is reduced as described above, the flatness (coplanality) of the island portion on which the semiconductor element is mounted and the lead on which the wire bonding is performed is deteriorated or the stick is generated depending on the structure and mechanical properties. Easier to do. In such a lead frame, the bonding position of the Si chip and the bonding position of the wire are likely to be out of order, which causes a failure of electronic components. Therefore, in a thin-walled / narrow-pitch lead frame, not only is it required to satisfy the mechanical properties, physical properties, and secondary workability of the same level as in the past, but also the flatness (coplanality) of the island portion and the lead portion. It is strongly demanded that the islands and the lead portions do not suffer from sticking. If there is a pecking, the flatness is impaired due to the oblique inclination of the island or the lead.

[0005] In order to satisfy such demands, the composition and structure of the lead frame material are optimized so that the island portions and the lead portions after the lead frame processing have sufficient rigidity (stiffness), and that after the stamping processing. Reduction of "burrs" and "who" is being considered. Improvements in the above-mentioned existing alloys are also being studied by changing the conditions of the thermomechanical treatment. In addition, due to the thinning of the lead frame, the rate of cold working after the completion of hot rolling increases, so that the manufacturing cost of the lead frame material increases, and as a result, the price of the lead frame material tends to increase. On the other hand, since the ratio of the lead frame price to the electronic component price is large, there is a strong demand from stampers and semiconductor manufacturers to reduce the lead frame material price. In order to respond to such demands, copper wrought copper makers are making efforts to reduce the manufacturing cost of lead frame materials.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the "burrs" and "sags" generated by punching while securing properties such as strength, conductivity, plating properties and the like which are higher than those of conventional materials. Another object of the present invention is to provide a copper alloy for a lead frame having a high stiffness and having improved flatness by suppressing the occurrence of the sticking of the island portion and the lead portion.

[0007]

According to the present invention, a copper alloy for a lead frame according to the present invention comprises: Ni: 0.1% or more and less than 0.5%;
n: more than 1.0% and less than 2.5%, Zn: more than 1.0% and 15% or less, Fe: 0.001% or more and 0.1% or less,
Mg: 0.0001% or more and 0.02% or less, P: 0.0
0.005% or more and less than 0.05% and Si: 0.0005% or more and less than 0.05%,
5% or more and less than 0.05%, S: 0.0005% or more.
003% or less, C content: 0.0005% or less,
Further, O: 0.005% or less, and H: 0.0002%
The following is a feature that the balance is made of Cu and inevitable impurities. If necessary, Ag, Ti, C
a, Mn, Be, Al, V, Cr, Co, Zr, Nb,
Mo, In, Pb, Hf, Ta, B, Ge, Sb: each containing one or more selected from the group of 0.001 to 0.1% in a total amount of 0.001% to 0.1%. be able to.

[0008] Further, as a characteristic of the copper alloy for lead frames, the maximum value of the conductivity obtained by annealing is 90%.
% On the rolled surface of the sheet or strip, the crystal grain size measured in the sheet width direction is 5 to 20 μm, and the crystal grain size measured in the direction parallel to the rolling direction is 5
It is desirable that the value of proof stress (σ0.2) / tensile strength (σB) be 0.9 or more. In order to produce a copper alloy for a lead frame having such properties, a copper alloy having the above composition is subjected to annealing during cold rolling and stabilized annealing after final cold rolling at 250 ° C to 850 ° C.
It is desirable to carry out in a temperature range of 5 seconds to 1 minute.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a copper alloy for a lead frame according to the present invention will be described in detail. First, the reason for adding each additive element and the reason for limiting the composition will be described. (Ni) Ni is an element that forms a modulation structure in the coexistence with Sn or improves strength, elongation, and stiffness characteristics in a solid solution state. If the content is less than 0.1%,
Even if Sn is contained in an amount exceeding 1.0% and less than 2.5%, the above effect cannot be obtained. Further, when the content is 0.5% or more, the electric conductivity and the solder weather resistance are reduced, which is disadvantageous in cost. Therefore, the content of Ni is set to 0.1% or more and less than 0.5%. When the alloy contains P, the strength and the stiffness of the alloy are reduced instead of the formation of the phosphide of Ni. Therefore, it is desirable to select a manufacturing method that does not form the phosphide of Ni.

(Sn) In the copper alloy of the present invention, Sn is N
In the coexistence with i, a modulation structure is formed, or in a solid solution state, it has an effect of improving strength, elongation and stiffness. However, the above effect cannot be obtained, and when the content is 2.5% or more, the conductivity is lowered. Therefore, the amount of Sn added is set to be more than 1.0% and less than 2.5%. In the range of the contents of Ni and Sn, when the content of Ni is x and the content of Sn is y, it is desirable that x and y satisfy the following relational expression. Within this range, the balance among mechanical properties, electrical conductivity, bending workability, and the like is particularly excellent. y = 3.75x + α−0.875 ≦ α ≦ 1.125

(Zn) In the copper alloy of the present invention, Zn is an element effective for improving the strength and the weather resistance of the solder and for suppressing the occurrence of whiskers in the Sn-plated material. Zn content is 1.
When the Zn content is less than 0%, the effect is small, and when the Zn content exceeds 15%, the electrical conductivity is reduced and stress corrosion cracking is easily caused. Therefore, the Zn content is set to be more than 1.0 and 15% or less. (Fe) In the copper alloy of the present invention, Fe forms a solid solution or forms a compound with P, and has an effect of improving strength, heat resistance and stiffness characteristics even in a trace amount. Since Fe forms phosphides more easily than Ni, Fe forms a phosphide and plays a role of hindering phosphide formation of Ni. When the content is less than 0.001%, there is no effect, and when the content exceeds 0.1%, the conductivity, the solder weather resistance and the like become poor. Therefore, the added amount of Fe is 0.001% or more and 0.1% or more.
The following is assumed.

[0012] (Mg) S easily enters from the raw material, atmosphere, etc. in the melting casting process.
Fixes S in the matrix in the form of a stable compound and improves hot workability. Further, even a small amount of Mg has an effect of improving strength, heat resistance and stiffness characteristics. M
If the content of g is less than 0.0001%, the above effect is not sufficient. When the content exceeds 0.02%,
When Ag plating is performed, Ag is abnormally deposited in a protruding manner, and the reliability of wire bonding is reduced. Therefore, Mg
The content is at least 0.0001% and at most 0.02%.

(P) In the copper alloy of the present invention, P is an element that contributes to deoxidation of molten metal and improvement of fluidity, and improves the soundness of the ingot. However, if the P content is less than 0.0005%, the above effect is not sufficient. On the other hand, if P is added in an amount of 0.05% or more, an Ni-P intermetallic compound is easily formed depending on the manufacturing process, and the strength, stiffness, and plating property are reduced. Further, even when the heat treatment is performed under the condition that the Ni-P compound is not precipitated, the conductivity is easily reduced, the solder and the Sn plating are separated, and the stress corrosion cracking is easily generated. Therefore, the amount of P added is set to 0.0005% or more and less than 0.05%. A more desirable range is 0.001% or more and 0.03%.
Is less than. In addition, when P and Si are contained together as described later, the same deoxidizing effect as when P is contained alone is obtained, but in that case, the total content of P and Si is as follows:
0.0005% or more and less than 0.05%. Desirably, it is 0.001% or more and less than 0.03%.

(Si) In the copper alloy of the present invention, Si has a deoxidizing effect on the molten copper and, even when contained in the same amount, has a small effect of lowering the conductivity as compared with P. Therefore, Si
Makes it possible to reduce the P content accordingly. Therefore, it is added instead of or together with P. However, P has a greater deoxidizing effect than P and Si. However, when stress corrosion cracking is considered, Si is preferable. Further, Si has the effect of increasing the recrystallization temperature. In order to obtain these effects, Si should be 0.00
It is desirable that the content be at least 05%. On the other hand, when Si is set to 0.
When the content is more than 0.05%, most of the oxides are removed from the molten metal as deoxidized oxides.
Causes whitening or peeling of the solder and Sn plating, and further reduces the conductivity. Therefore, when Si is added, its content is set to 0.0005% or more and less than 0.05%. A desirable range is 0.001% or more and less than 0.03%. When P is contained together with P, the total content of P and Si is set to 0.0005% or more and less than 0.05%. Desirably, it is 0.0001% or more and less than 0.03%.

(S) In the copper alloy of the present invention, S is a simple substance,
It exists at the crystal grain boundary in the form of a low melting point intermetallic compound or composite oxide, and therefore has the effect of improving punching workability (reducing burrs and improving shearing workability) and reducing mold wear. When the S content is 0.0005% or less, the above effect is not obtained. On the other hand, when the content of S exceeds 0.003%, S or the sulfide present at the grain boundaries during hot working is melted to cause grain boundary cracking, and cracks occur in the ingot. . For this reason, the S content must be 0.003% or less. Therefore, the content of S is set to 0.0005% or more and 0.003% or less. (C) In the copper alloy of the present invention, C is a deoxidizing action of the molten metal,
It has the effect of improving the punching workability, especially the shearing workability. However, when the content exceeds 0.0005%, the hot workability is deteriorated. Therefore, the content of C is 0.0
005% or less. In addition, C can be contained in the molten metal by bringing the charcoal, C particles, and the like that coat the surface of the molten metal into contact with the molten metal during melting and casting. According to this method, C can usually be contained at about 0.0001 to 0.0004%.

(O, H) The copper alloy of the present invention can be prepared by using an ordinary coreless furnace, a grooved furnace or the like without using a vacuum furnace or the like.
By coating the surface of the molten metal with charcoal, C particles, a suitable flux, or the like, the molten metal can be melt-cast in the atmosphere. However, in the melting and casting process in the atmosphere, the raw material, the coating material on the surface of the molten metal, moisture or oxide attached to or contained in the furnace material, and water vapor, oxygen, carbon dioxide, hydrogen, and the like present in the atmosphere. It is inevitable that the molten metal contains O and H by reacting with the molten metal. Particularly, once H is contained, it is difficult to effectively remove it. Therefore, it is necessary to pay attention to the melting casting atmosphere, the raw materials used, the drying of the molten metal coating material, and the like so as not to contain more than a predetermined amount. In the copper alloy of the present invention,
If the H content exceeds 0.0002%, cracks during hot rolling, swelling during annealing, plating swelling and the like occur, and the yield decreases, so the content must be regulated to 0.0002% or less. Preferably it is 0.0001% or less, more preferably 0.00007% or less.

[0017] In the copper alloy of the present invention, the content of O is 0.1.
If it exceeds 005%, an oxide is likely to be formed in the melting casting step, the hot rolling, and the annealing step, and this oxide tends to reduce the ductility of the product. Further, the plating properties of Ag, Sn, solder and the like are reduced by the oxide and the solid solution oxygen. Therefore, the O content must be regulated to 0.005% or less. Preferably it is 0.003% or less, more preferably 0.002% or less. Incidentally, both H and O are usually contained, but when the H content is a ppm and the O content is b ppm, when the value of a × b exceeds 40, H and O are used in a heating step such as hot rolling and annealing. O reacts to easily form water vapor, which causes cracking and swelling. Therefore, a × b (H content (ppm) × O content (pp
It is desirable that the value of m)) is 40 or less. The value is more preferably 30 or less, and further preferably 20 or less.

(Other selected elements) Ag, Ti, Ca,
Mn, Be, Al, V, Cr, Co, Zr, Nb, M
Since o, In, Pb, Hf, Ta, B, Ge, and Sb all have the effect of improving the strength and stiffness of the copper alloy of the present invention, one or two selected from these groups can be used.
More than one element is added as needed. However, if the content of each element is less than 0.001%, the above effect is not sufficient. On the other hand, if one or more of these elements is contained in a total amount of more than 0.1%, the dissolution may occur. Coarse oxides are formed during casting, hot rolling or during thermomechanical treatment, or coarse crystals are formed, thereby deteriorating plating properties and conductivity. Therefore, the content of these selected elements is 0.001% or more and 0.1% or less, respectively, and the total amount of one or more types is 0.001% or more and 0.1% or less.

Next, the characteristics and structure of the copper alloy of the present invention will be described. (Conductivity) In the copper alloy of the present invention, when the Ni-P compound is precipitated, the strength and the stiffness are rather deteriorated,
It is desirable that the compound be spinodal-decomposed or dissolved (spinodal-type modulation structure) without precipitating the compound. N
Since there is a correlation between the amount of precipitation of the i-P compound and the electrical conductivity, the deposition state of the compound can be estimated from the electrical conductivity. In order to achieve the desired strength and stiffness in the copper alloy of the present invention, it is desirable that the conductivity be 90% or less of the maximum value of the conductivity obtained by annealing the copper alloy. In the copper alloy of the present invention, the maximum conductivity is obtained at about 500 ° C., and the longer the heating time at this temperature, the higher the conductivity is, but the conductivity is practically almost saturated by heating for 4 hours. This is because precipitates are generated in almost the maximum amount by this annealing. Therefore, in the present invention, the annealing condition at which the maximum conductivity is obtained is set to 500 ° C. × 4 hours. In order to obtain the above-mentioned electrical conductivity after the stabilized annealing, the electrical conductivity needs to be the above-mentioned electrical conductivity after the annealing during the cold rolling (before the stabilized annealing).

(Crystal Grain Size) In order to achieve the desired strength and stiffness in the copper alloy of the present invention, the average crystal grain size measured in the sheet width direction on the rolled surface of the sheet or strip is 5 to 5.
It is desirable that the average crystal grain size measured in a direction parallel to the rolling direction is 5 to 300 μm.
When the former crystal grain size is smaller than 5 μm or the latter is smaller than 5 μm, and when the former crystal grain size is 20 μm
If the average particle diameter exceeds 300 m or the crystal grain diameter of the latter exceeds 300 μm, the bending workability is lowered, and cracks are easily formed in the bent portion. Therefore, it is desirable that the crystal grain size measured in the width direction of the rolled surface be 5 to 20 μm and the crystal grain size measured in a direction parallel to the rolling direction be 5 to 300 μm.

In order to achieve the above-mentioned crystal grain size, it is desirable to perform a final cold rolling after forming a recrystallized structure once, and then to carry out a stabilized annealing at a low temperature. In stabilized annealing, the dislocations introduced by cold rolling rearrange,
The stiffness and elongation are slightly improved with little decrease in strength. It is also effective for improving the anisotropy of the mechanical properties. The recrystallized structure before the final rolling has an average size of 5 to 3 without specific orientation or bias as measured by a cutting method defined in JIS H0501.
Desirably, recrystallized grains of 0 μm are formed. Here, the lower limit of the crystal grain size during recrystallization, 5 μm, is a size that can be relatively easily realized within the heat treatment range that can be industrially performed. The heat treatment must be completed and is not practical. On the other hand, when the crystal grain size at the time of recrystallization exceeds 30 μm, it undergoes deformation due to its own weight while passing through a process such as a continuous vertical heat treatment furnace, resulting in a difference in strain between crystal grains and grain boundaries, resulting in a product The surface becomes rough, and the appearance, bending workability, and uniformity of product characteristics are deteriorated. Since the strength of the recrystallized structure is reduced, a final cold working at a working ratio of about 10 to 90% is performed to accumulate a large amount of dislocations and improve the strength. Due to the cold working, the recrystallized structure is inevitably stretched in the rolling direction to have a rugby ball shape. In this case, for example, when measured by a cutting method prescribed in JIS H0501, the average crystal grain size measured in the width direction of the plate on the rolled surface of the plate or strip is substantially in the range of 5 to 20 μm, and is parallel to the rolling direction. The average crystal grain size measured in the direction is in the range of approximately 5 to 300 μm.

(Proof Strength / Tensile Strength) In the copper alloy of the present invention, the ratio of the proof strength to the tensile strength is determined by the punching workability (burr amount,
Punching cross-section ratio (shear surface / fracture surface), and stiffness. The closer the punching cross-section ratio (shear surface / fracture surface) = 1, the better the punching workability. Further, when a lead frame is processed from the copper alloy strip of the present invention, the greater the stiffness, the less likely the island to stick. When the ratio of proof stress to tensile strength (proof strength / tensile strength) is 0.9 or more, the punching cross-sectional ratio becomes almost 1 and the punching workability is improved, and the stiffness is improved. Peking is less likely to occur. For these reasons, it is desirable that the ratio of proof stress / tensile strength be 0.9 or more.

Next, the manufacturing process of the present invention will be described. (Melting Casting) The copper alloy of the present invention can be melt-cast in the atmosphere. As the melting furnace, a coreless furnace, a grooved furnace, or the like can be used, and the surface of the molten metal is preferably covered with charcoal, graphite particles, covering flux, or the like, and is desirably performed under conditions that minimize contact with the atmosphere. In the melting procedure, for example, first, an electrolytic copper ingot is melted, and then Sn, Zn, Fe, P and / or Si are added in the form of an appropriate intermediate alloy or a pure metal to the molten copper in this order, thereby causing a problem. do not do. Also, as a raw material for melting, scrap generated in the manufacturing process,
Dust after punching can also be used. In order to prevent hydrogen from being taken into the molten metal, it is desirable that charcoal, graphite particles, flux, furnace materials, molds, gutters, jigs, and the like that are in contact with the molten metal be sufficiently dried. Since the copper alloy of the present invention contains Zn in excess of 1.0%, in the melting and casting step, Zn vapor is generated from the molten metal, which is advantageous for reducing the hydrogen content of the molten metal. For casting, the slab may be ingot by vertical continuous casting, or horizontal continuous casting may be performed.

(Working heat treatment) In the case of a slab, the steps of hot rolling, cold rolling, annealing, cold rolling, and stabilizing annealing (may be repeated), and in the case of a horizontally continuous cast material, It is desirable to perform the steps of soft annealing, cold rolling, annealing, cold rolling, and stabilized annealing. In the hot rolling, an appropriate rolling temperature may be appropriately selected depending on the alloy composition. However, after the ingot is heated to 750 to 950 ° C., the ingot is held for about 30 minutes to 2 hours, and then rolling is started. After the completion of the hot rolling, it is desirable to perform water cooling to suppress the precipitation of the Ni-P compound.

In order to improve the strength and stiffness, which are the features of the copper alloy of the present invention, it is necessary to perform a final cold rolling after forming a recrystallized structure once, and then to perform a stabilized annealing and a strain relief annealing at a low temperature. desirable. In the stabilized annealing strain relief annealing, the dislocations introduced in the cold rolling rearrange, and the stiffness and elongation are slightly improved without substantially reducing the strength. It is also effective for improving the anisotropy of the mechanical properties. In any of the intermediate annealing and the stabilizing annealing, it is desirable to set the electric conductivity to 90% or less of the maximum value. Therefore, in the above-described intermediate annealing, a uniform recrystallized structure having an average crystal grain size of about 5 to 30 μm is obtained, and the Ni—P compound is not precipitated as much as possible.
Annealing is preferably performed at a temperature of 50 to 850 ° C., more preferably 550 to 650 ° C., for 5 seconds to 1 minute (the temperature and the heating time after the material to be heated reaches the above temperature).

The above-mentioned final rolling is necessary for improving the strength and stiffness of the alloy softened by annealing, and the working ratio may be selected from 10 to 90%. Then, the stabilization annealing is performed, but the purpose is to rearrange the dislocations introduced by the final rolling, and to improve ductility while maintaining strength and stiffness.
Annealing (the temperature and the heating time after the material to be heated reaches a predetermined temperature) is preferably performed in a temperature range of 250 to 850 ° C., more preferably 300 to 450 ° C., for 5 seconds to 1 minute. . Since the purpose of annealing the alloy of the present invention is to recrystallize and remove strain, it is desirable to perform the annealing in a continuous annealing furnace.

Further, by performing pickling and / or polishing with a pickling polishing device attached to the continuous annealing furnace or another line, a plate or strip for a lead frame having a surface oxide film of about 2 to 4 nm. Can be manufactured. For applications in which low distortion is particularly important, a step of tension leveling or tension annealing may be added after the final annealing. Many of the current high-strength copper alloys contain Ni-Si, N
Compounds such as i-P and Cu-Zr, and precipitation-strengthened copper alloys in which metal atoms such as Cr are precipitated occupy the majority (see, for example, JP-A-2000-119779). On the other hand, in order to form these precipitate particles in the copper matrix, it is necessary to diffuse a precipitate constituent element dissolved in copper to form a compound. Further, since this diffusion requires one to several hours even at a temperature of 400 to 600 ° C., annealing of these precipitation-type copper alloys is carried out after charging the coil into a bell type furnace or the like,
Batch annealing is employed in which the temperature is maintained for a predetermined time after reaching a predetermined temperature, and further lowered to a temperature near room temperature. In batch type annealing, from the start of annealing to the completion of annealing, 20 to 30 minutes is required.
Since it takes time, the productivity of the precipitation-type copper alloy is reduced, which is one of the causes of an increase in cost. In the copper alloy of the present invention, since it is not necessary to precipitate a Ni-P compound, a continuous annealing furnace can be applied, which greatly contributes to improvement in productivity and reduction in manufacturing cost.

[0028]

EXAMPLES Examples of the copper alloy according to the present invention will be described below. (Example 1) A copper alloy having the composition shown in Tables 1 and 2 was melted in an air atmosphere under a charcoal coating in an electric furnace, and cast into a book mold to produce an ingot of 50 mm x 70 mm x 200 mm. This ingot was heated to 750 to 900 ° C., held for one hour after reaching a predetermined temperature, and then hot rolled. Board thickness 15mm
Rolled to quenching in water to obtain a hot rolled material. The temperatures during quenching were all 600 ° C. or higher. In the hot-rolled material, the presence or absence of cracks was visually confirmed. The hot rolled material in which cracks occurred was not subjected to the subsequent thermomechanical treatment.

[0029]

[Table 1]

[0030]

[Table 2]

In Tables 1 and 2, the No. of the present invention example. 1 to
No. 8 and Comparative Example Nos. No cracks during hot rolling occurred in any of Nos. 9 to 10, and 15 to 27. On the other hand, N
o. Since the alloys 11 to 14 cracked during hot rolling,
No subsequent thermomechanical treatment was performed. In addition, No. 11
No. 2 was insufficient in P and Si, so that a sound ingot could not be obtained due to insufficient deoxidation. In No. 12, hot rolling was not performed in any case because a large number of pipe-shaped holes considered to be caused by hydrogen were formed in the ingot due to excessive H. No. In No. 13, cracks occurred during hot rolling due to excessive S, and hot rolling was stopped halfway. No. In No. 14, since the C was excessive, many small cracks were generated in the hot-raised material, and the subsequent working heat treatment was not performed.

Subsequently, No. For 1 to 10, 15 to 27, the hot-rolled material is subjected to working heat treatment under the following conditions,
A plate material having a thickness of 0.11 mm was produced. Hot rolled material (15 mmt) → cold rolling to 0.22 mmt → annealing at 500-700 ° C x 20 seconds (salt bath furnace) →
Cold rolling to 0.11 mmt → stabilized annealing at 350 ° C for 20 seconds. A test piece was processed from the thin plate having a thickness of 0.11 mm thus produced, and the following test was performed. Table 3 shows the results.

(Mechanical properties) A JIS No. 5 test piece (n = 2) was machined with the longitudinal direction of the test piece being parallel to the rolling direction.
A tensile test was performed to measure 0.2% proof stress and tensile strength. The average of the measured values of n = 2 was taken as the value of each test material. In addition, the elongation of 10% or more was able to be secured also in the test piece of the displacement. (Electrical conductivity) The electrical conductivity was evaluated by measuring the electrical conductivity. The conductivity was measured based on JIS H505. (Solder weather resistance) MIL-STD-202F METH
After soldering using 60Sn-40Pb eutectic solder based on OD 208D, n = 3, 150 ° C x 1000Hr in air at n = 3, and 18 mm in bending diameter of 1mm
It was bent back by 0 °, and the presence or absence of peeling of the solder at the bent portion was visually confirmed.

(Stiffness Characteristics) Using a moment type testing machine based on Electronic Materials Manufacturers Association Standard: EMAS-1003, bending radius: 30 mm, bending moment: 0.1.
The displacement angle (゜) under load was measured at 12 N / m (n =
2). The test piece has a width of 10 mm and a length of 60 mm, and the bending moment is applied to a position 30 mm from a fulcrum holding the test piece. (Ag plating property) After applying 5 μm thick Ag plating,
After heating at 450 ° C. for 5 minutes in the air, the surface was inspected with an optical microscope at a magnification of 200 × to observe the presence of swelling and protrusions.

(Stress corrosion cracking resistance)
A 2.7 mmw × 150 mm test piece (n = 4) was cut out and subjected to a stress corrosion cracking test by the method of Thompson (Material
s Research & Standards (1961) 1081).
That is, after the test piece was formed into the loop shape shown in FIG.
The test piece was exposed to a desiccator filled with saturated steam at a temperature of 40 ° C. containing ammonia water of mass% and the time until the test piece was broken was measured. (Whisker resistance) A strip-shaped test piece is bent into an arc shape using a jig, and thereby approximately 400 N is applied inside the apex of the arc.
After applying a compressive stress of 3 mm / mm ² and holding at room temperature for 3 months, the occurrence of whiskers on the compressed surface (the inside of the top of the arc) was observed with a stereoscopic microscope.

[0036]

[Table 3]

Inventive Example No. Each of Nos. 1 to 8 has good mechanical properties, conductivity, stiffness properties, solder weather resistance, stress corrosion cracking resistance, Ag plating properties, and whisker resistance, and is suitable as a thin lead frame material. On the other hand, in Comparative Example No. Samples 9 and 10 are inferior in stiffness characteristics due to insufficient Sn content. No. 15 is Ni
Is excessively contained, the conductivity is low, the solder is peeled off, and the stiffness characteristics are poor. No. 16 is Ni
Is insufficient, yield strength is low and stiffness characteristics are inferior. No. No. 17 has a low electrical conductivity because it contains excessive Sn. No. No. 18 has insufficient Sn content because of insufficient Sn content, and is inferior in stiffness characteristics. No. No. 19 has a low conductivity due to excessive Zn content and is inferior in stress corrosion cracking resistance. No. In the case of No. 20, the peeling of the solder occurs because the Zn content is insufficient,
Further whiskers are occurring. No. In the case of 21, P is excessively contained, so that the electrical conductivity is lowered, the solder is peeled off, and the stress corrosion cracking resistance is poor. No. Sample No. 22 has an excessively large amount of Si, and thus has a low electrical conductivity and has peeled solder. No. In No. 23, since Fe is excessively contained, the electrical conductivity is lowered and the solder is peeled off. No. 24 contains Mg in excess, so A
g When plating is performed, protrusions are generated, and further, solder peeling occurs. No. In No. 25, since Mn and the like are excessively contained, the electrical conductivity is lowered and the solder is peeled off. No.
In No. 26, since the contents of P and Si exceed the upper limit values, the electrical conductivity is lowered, the solder is peeled off, and the stress corrosion cracking resistance is further deteriorated.

(Example 2) Cold-rolled-intermediate annealing-cold rolling- on hot-rolled material 2 (15mmt)
A plate material having a thickness of 0.15 mm was produced by performing a working heat treatment such as final annealing. Table 4 shows the thermomechanical treatment conditions. The crystal grain size, mechanical properties, electrical conductivity, stiffness, etc. of these sheet materials were investigated. Table 5 shows the results.

[0039]

[Table 4]

[0040]

[Table 5]

Inventive Example No. In 2-1 to 2-3, proof stress,
The conductivity and the contact bending workability are good, the conductivity is 90% or less as compared with the batch annealing material 2-10, the ratio of proof stress / tensile strength is 0.9 or more, and the stiffness characteristics are also excellent. On the other hand, in Comparative Example No. 2-4 has a low intermediate annealing temperature,
In addition, since the heating time is short, recrystallization does not occur during the intermediate annealing, and the stiffness characteristics are poor. In addition, although not described in the table, it is elongated and has poor bending workability. No. In No. 2-5, since the heating time of the intermediate annealing is long, the crystal grains are coarsened, the conductivity is 90% or more of the batch-annealed material, and the strength is reduced.
Further, the ratio of proof stress / tensile strength is less than 0.9, and the stiffness characteristics are also poor. Comparative Example 2-6 is inferior in stiffness characteristics since final annealing was not performed. In addition, although not described in the table, it is elongated and has poor bending workability. No. 2-7
Since the final annealing temperature is low and the heating time is short, rearrangement of dislocations does not occur, and the stiffness characteristics are poor. In addition, although not described in the table, it is elongated and has poor bending workability. N
o. In No. 2-8, since the final annealing temperature was high and the heating time was long, the crystal grains were coarsened and the strength was reduced. The ratio of proof stress / tensile strength is less than 0.9, and the stiffness characteristics are also poor. No. In 2-9, the final annealing time was long, the crystal grains were coarsened, and the precipitation of Ni-P compounds and the like occurred, so that the electrical conductivity was 90% or more of the batch-annealed material, and the strength was reduced. The ratio of proof stress / tensile strength is less than 0.9, and the stiffness characteristics are also poor. No. In 2-10, the intermediate annealing was performed by batch annealing to cause precipitation of Ni-P compounds and the like.
Poor stiffness characteristics.

Example 3 Two ingots having the compositions shown in Table 6 were formed by continuous casting. The size of the ingot is 150m
m, width 500 mm, length 5000 mm. This ingot was kept at 850 ° C. for 2 hours, hot-rolled to a thickness of 15 mm, and an oxide film on the surface was removed with a scalper.
mm, cold-rolled, continuously annealed, pickled and polished in a DX gas atmosphere. Thereafter, the thin plate was cold-rolled to 0.125 mm, finish annealing was performed in a continuous annealing furnace in a DX gas atmosphere, and after annealing, pickling and polishing were performed to remove an oxide film on the surface to obtain a test material.

[0043]

[Table 6]

From the test materials, mechanical properties, electrical conductivity, stiffness characteristics and the like were measured by the above-mentioned methods, and stamping was performed by the following methods to evaluate punching workability and shearing workability. Table 7 shows the results. (Punching workability) Using a 25t press (BRUDERER BSTA-25), a QFP type lead frame was punched out by 1,000,000 shots at a clearance of 5% and a punching speed of 600 spm, and the burring height and droop width of the material were measured. (Shearability)

[0045]

[Table 7]

The copper alloy of the present invention has mechanical properties, electrical conductivity, stiffness properties, solder weather resistance, stiffness properties, stress corrosion cracking resistance, Ag plating properties, whisker resistance, punching workability and shearing workability. I understand. Also,
No peko was generated on the island portion of the punched lead frame, and the flatness of both the island portion and the lead portion was extremely good. Furthermore, the oxide film on the surface was 2-3 nm, and the Ag plating and Sn plating properties were also very good. Mount the Si chip on the lead frame after plating,
Although LSIs were manufactured, problems such as insufficient strength, warpage of leads, and pecking of islands did not occur even by heating in the manufacturing process, and LSIs could be manufactured with good yield and productivity.

[0047]

According to the present invention, a copper alloy for a lead frame which is excellent in punching workability and stiffness properties, and is also excellent in strength, solder weather resistance, stress corrosion cracking resistance, Ag plating property and whisker resistance is inexpensive. Can be supplied to

[Brief description of the drawings]

FIG. 1 is a diagram showing a loop-shaped test piece used for a stress corrosion cracking resistance test.

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) // C22F 1/00 606 C22F 1/00 606 630 630A 630K 661 661A 682 682 685 685Z 686 686B 691 691B 691C 694 694A ) Inventor Hiroshi Sakamoto 14-1, Nagafuminatocho, Shimonoseki City, Yamaguchi Prefecture F-term in Kobe Steel, Ltd. Chofu Works (reference) 5F067 AA09 AA10 EA04

Claims (6)

[Claims] 1. Ni: 0.1% (% by mass, hereinafter the same) or more and less than 0.5%, Sn: more than 1.0% and less than 2.5%,
Zn: more than 1.0% and 15% or less, Fe: 0.001%
0.1% or less, Mg: 0.0001% or more and 0.02 or less
% Or less, P: 0.0005% or more and less than 0.05% and S
i: One or both of 0.0005% or more and less than 0.05%, 0.0005% or more and less than 0.05%, S:
0.0005% or more and 0.003% or less, C: 0.000
A copper alloy for a lead frame, containing 5% or less, further O: 0.005% or less, and H: 0.0002% or less, with the balance being Cu and unavoidable impurities. 2. Ag, Ti, Ca, Mn, Be, Al,
V, Cr, Co, Zr, Nb, Mo, In, Pb, H
f, Ta, B, Ge, Sb: 0.001% in total of one or more selected from the group of 0.001 to 0.1%.
The copper alloy for lead frames according to claim 1, wherein the copper alloy contains at least 0.1%. 3. The copper alloy for a lead frame according to claim 1, wherein the copper alloy has a conductivity of 90% or less of a maximum value of a conductivity obtained by annealing. 4. The rolled surface of the plate or strip has an average crystal grain size measured in the width direction of the plate of 5 to 20 μm and an average crystal grain size measured in a direction parallel to the rolling direction of 5 to 300 μm.
The copper alloy for a lead frame according to any one of claims 1 to 3, wherein the thickness is μm. 5. The copper alloy for a lead frame according to claim 1, wherein the value of proof stress / tensile strength is 0.9 or more. 6. The copper alloy according to claim 1 is subjected to annealing during cold rolling and stabilized annealing after final cold rolling in a temperature range of 250 ° C. to 850 ° C. A method for producing a copper alloy for a lead frame, which is carried out for at least one second and at most one minute.