JP2797835B2 - High-strength Fe-Ni-Co alloy thin plate excellent in corrosion resistance and repeated bending characteristics, and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength Fe-Ni-Co alloy thin plate having excellent corrosion resistance and repeated bending characteristics and a method for producing the same, and relates to a material for an IC lead frame having high strength and excellent corrosion resistance and repeated bending characteristics. And a preferred production method thereof.

[0002]

2. Description of the Related Art In recent years, as the integration of semiconductors and the thickness of package have become thinner, lead frames have increased in number of pins.
It has a tendency to be thinner, and therefore, there is a demand for a higher strength of the lead frame material.

[0003] However, as the Fe-based high-strength lead frame material for multi-pin as described above, Japanese Patent Application Laid-Open No.
No. 40 has been proposed. That is, in the disclosed technology,
-To control the amount of Ni and Co in a Ni-Co alloy and to precipitate a reverse-transformed austenite phase by a work-induced martensitic transformation at a specific working ratio and subsequent annealing to form a two-phase structure at a specific ratio. the various characteristics of the lead frame, in particular solderability, plating resistance, high strength and low thermal expansion properties, without compromising (H _V in 260 or more, a tensile strength of 80 kgf / mm ² or higher)
Is to achieve.

[0004]

In the prior art as described above, H _V = 270-380 and tensile strength 85-117.
kgf / mm ² , average coefficient of thermal expansion α _RT-300 = 5.2 to 8.5 × 10
^-6 / ° C. and excellent silver plating properties, solderability and crevice corrosion, but still had the following problems. (1) There is a problem in the corrosion resistance of the material. (2) Poor repetitive bending characteristics (bending workability). (3) in the H _V 275 or more high strength material alpha _RT-300 is 6.8 ×
It has a high thermal expansion coefficient of 10 ^-6 / ° C or more, and there is a high risk that the Si chip will be damaged by thermal strain when the Si chip is mounted on a lead frame in an IC manufacturing process.

[0005] The corrosion resistance is such that the material is martensite +
Since it has a two-phase structure of austenite, and the austenite phase is mainly an austenite phase having a low dislocation density formed by reverse transformation, corrosion easily progresses between martensite having a high dislocation density and residual austenite. And was significantly inferior. In terms of product characteristics, spot rust occurs on the material surface after the coil is manufactured and before slit processing or fine processing of the lead frame is performed, which causes a serious problem. Normal 42 alloy (Fe-
In the case of 42wt% Ni), there is no such a problem. It is a low-Ni alloy with 32.5% or less Ni as in this material, and metal phases with different dislocation densities coexist in the same material. Is presumed to be the main cause of deterioration in corrosion resistance.

[0006] The repetitive bending characteristics are also deteriorated by the above-mentioned characteristic of the present material, that is, the presence of a large amount of reverse transformed austenite having a low dislocation density and a low strength in contrast to martensite having a high dislocation density and a high strength. I do.

[0007] In addition, if the thermal expansion characteristic is intended to further increase the strength, the amount of martensite increases due to the work-induced transformation at the time of cold rolling, which is a feature of this technology, and is impaired. Furthermore, the balance between the thermal expansion and the high strength, which is a feature of the present technology, cannot respond immediately to the recent needs for high strength and low thermal expansion characteristics. That is, the average thermal expansion α _30-400 ^. _{When C} is 4-8 × 10 ⁻⁶ / ° C. and the strength satisfies the tensile strength of 120 kgf / mm ² or more, the components and the structure range cannot be determined by this technique.

[0008] In recent years, there has been a demand for further cost reduction of lead frames, and the tendency of thinning of Ag has been intensified, and the thinning of the Ag plating thickness (3 μm) seen in the present technology has been advanced. At present, there is a problem of Ag plating property in the alloys characterized by the present technology in response to such a demand. Furthermore, the present alloy has achieved high performance in terms of solderability and weather resistance in the above-mentioned Japanese Patent Application Laid-Open No. 3-166340, but has not yet seen any improved technique in terms of wettability.

[0009]

SUMMARY OF THE INVENTION The present invention has been studied to solve the above-mentioned problems in the prior art, and specifies the composition and the structure of this type of Fe-Ni-Co alloy. As a result, the object has been effectively achieved, and a preferable production method has been successfully established, as follows.

In wt%, Ni: 27-30%, Co: 5-5
18%, Mn: 0.10 to 3.0%, Si: 0.10% or less, and the content of Ni, Co and Mn is less than 10% for Co: 6%.
3.5% ≦ 2Ni + Co + Mn ≦ 65.0%, Co: 10% or more satisfies the relationship of 69.5% ≦ 2Ni + Co + Mn ≦ 72.5%, C: 0.020-0.070%, N : 0.010% or less, H: 1.0 ppm or less, S: 0.0030% or less, P: 0.
003% or less, O: 0.0040% or less, Cr: 0.05% or less, Mo: 0.01 to 1.0%, the balance consisting of Fe and unavoidable impurities. 3
0-90%, high-strength Fe- with excellent corrosion resistance and repeated bending characteristics characterized in that the grain size is No. 8 or more.
Ni-Co alloy thin plate.

[0011] In addition to the above components, B, Nb, Ti, Z
One or more of r, Ta, V and W are 0.0 in total.
A high-strength Fe containing 1 to 0.50% and having the structure according to claim 1, having excellent corrosion resistance and repetitive bending characteristics.
-Ni-Co alloy sheet.

[0012] The average thermal expansion coefficient of 30 to 400 ° C. is ^{(4~8) × 10 -6 / ℃} , Vickers hardness (H _V) at least 280 hardness, the tensile strength is 85 kgf / mm ² or more The corrosion resistance according to or above, which is characterized by:
High-strength Fe-Ni-Co alloy sheet with excellent repeated bending characteristics.

[0013] In the production of a thin sheet of the cold rolled material of the alloy having the above composition in the steps of primary cold rolling, primary annealing, secondary cold rolling, secondary annealing, tertiary cold rolling and low temperature heat treatment, The cold rolling rate (CR ₁ ) is 60 to 80%, the primary annealing temperature (T ₁ ) is
700-740 ° C., secondary cold rolling reduction (CR ₂ ) is 75-85.
%, The secondary annealing temperature (T ₂ ) is 700 to 740 ° C., the third cold rolling reduction (CR ₃ ) is 20 to 70%, and the low temperature heat treatment temperature (T ₃ ).
At 400 to 540 ° C. and a low temperature heat treatment time (t) of 0.5
A method for producing a high-strength Fe-Ni-Co alloy sheet having excellent corrosion resistance and repeated bending characteristics, characterized in that the thickness is 60 to 60 min.

In the production of a thin sheet of the alloy cold-rolled material having the above-described composition in the steps of primary cold rolling, primary annealing, secondary cold rolling, secondary annealing, tertiary cold rolling and low temperature heat treatment, The cold rolling rate (CR ₁ ) is 60 to 80%, the primary annealing temperature (T ₁ ) is
700-740 ° C., secondary cold rolling reduction (CR ₂ ) is 75-85.
%, The secondary annealing temperature (T ₂ ) is 700 to 740 ° C., the third cold rolling reduction (CR ₃ ) is 20 to 70%, and the low temperature heat treatment temperature (T ₃ ).
At 400 to 540 ° C. and a low temperature heat treatment time (t) of 0.5
A method for producing a high-strength Fe-Ni-Co alloy thin plate having excellent corrosion resistance and repeated bending characteristics, characterized in that the thickness is 60 min.

[0015]

In the present invention as described above, the reasons for limiting the chemical components of the alloy will be described in terms of wt% (hereinafter simply referred to as%). The low thermal expansion characteristics, high strength and excellent repeated bending characteristics and corrosion resistance intended in the present invention are as follows. It is necessary to properly control the amount of austenite in the structure, especially the amount of retained austenite, to obtain Co, Ni, Mn, S
It is necessary to optimize the amounts of i, C and N, as follows.

If Si exceeds 0.10%, the martensite initiation temperature is high, austenite becomes unstable, and martensite transformation occurs during the cooling process during the solution treatment, and Co, Ni, Mn as described below. Even if the amount was adjusted appropriately, the amount of retained austenite intended in the present invention could not be obtained, and the plating ability of the present invention could not be attained, so the upper limit was 0.10%. A more preferable Si amount for improving solderability is 0.
Not more than 05%.

If Co is less than 5% or more than 18%, the coefficient of thermal expansion becomes large, and the thermal expansion matching with the silicon chip is deteriorated. For this reason, the Co content is set in the range of 5 to 18%.

If Ni is less than 27% or more than 30%,
The coefficient of thermal expansion is increased, and deteriorates the thermal expansion matching with the silicon chip. For this reason, the Ni content is in the range of 27 to 30%.

If Mn is more than 3.0%, austenite becomes stable, and work-induced transformation hardly occurs. In addition, 0.1%
If it is less than 1, the martensite start temperature is high, austenite becomes unstable, and work-induced martensite transformation is likely to occur during cold working, and as a result, a sufficient amount of retained austenite cannot be obtained. From these facts, the upper limit of the Mn content was set to 3.0%, and the lower limit was set to 0.1%.

In order to obtain the characteristics intended in the present invention,
The total amount of Ni, Co, and Mn must be controlled according to the amount of Co, as well as the above-described single amount. That is, if Co is less than 10%, (2Ni + Co + Mn) is 63.5%
In the case of less than 10% or more than 10% of Co (2Ni + Co
If (+ Mn) is less than 69.5%, the martensite onset temperature is high, austenite becomes unstable, and work-induced martensite transformation is likely to occur, with the result that a sufficient amount of retained austenite cannot be obtained. Further, when Co is less than 10% and (2Ni + Co + Mn) exceeds 65.0%, or when Co is 10% or less.
% Or more and (2Ni + Co + Mn) exceeds 72.5%, the austenite becomes stable, and it becomes difficult for the work-induced martensitic transformation to occur. For this reason, Ni, Ni is set so that 63.5% ≦ 2Ni + Co + Mn ≦ 65.0% when Co is less than 10%, and 69.5% ≦ 2Ni + Co + Mn ≦ 72.5% when Co is 10% or more.
Co and Mn are limited.

In the present invention, C and N are indispensable elements for properly controlling the martensitic transformation induced by processing and achieving higher strength in the final aging treatment. That is, first, if C is less than 0.020%, austenite becomes unstable and martensitic transformation induced by processing is apt to occur. As a result, sufficient retained austenite cannot be obtained, and an increase in strength due to age hardening cannot be expected. . On the other hand, if the content exceeds 0.070%, austenite becomes stable, and it becomes difficult for martensitic transformation induced by processing to occur, and the plating properties deteriorate. Therefore, C is
The lower limit is 0.020% and the upper limit is 0.070%.

If N is more than 0.010%, austenite becomes stable, it becomes difficult to cause work-induced martensitic transformation, and the plating property further deteriorates. Therefore, N is 0.
010% is the upper limit. The addition of N in a range of 0.01% or less has the effect of increasing the strength by age hardening. When N is in the range of 0.010% or less, all of the low thermal expansion characteristics, high strength and excellent repeated bending characteristics, corrosion resistance and plating properties intended in the present invention can be obtained.

Further, in the present invention, in addition to the above-mentioned component definition, in order to improve the repetitive bending characteristics, the S content,
It is necessary to reduce the amount of O. Further, in order to further improve the plating property intended in the present invention with this alloy, H, S, P, O
And the reduction of Cr are essential.

That is, S and O are elements which adversely affect the repetitive bending characteristics and the plating properties of the present alloy through the formation of nonmetallic inclusions. If S exceeds 0.0030%, the repeated bending property deteriorates, and the plating property cannot be at the level intended in the present invention. Therefore, the upper limit is 0.0030%. The more preferable S content for solderability is 0.0010% or less.

If O exceeds 0.0040%, the alloy is deteriorated in repeated bending characteristics and the plating property cannot attain the level intended in the present application. Therefore, the upper limit is 0.0040%. More preferable O content for solderability is 0.0020%
It is as follows.

The mechanism of the deterioration of the repeated bending characteristics due to the presence of S and O is that in the case of the present alloy, a large number of nonmetallic inclusions in which S or O is detected were found at the interface where the bending was broken. It is conceivable to promote cracks starting from these inclusions.

Further, in the alloy of the present invention, the above-mentioned O,
In addition to the reduction of S, the reduction of H, P, and Cr is essential. That is, first, P segregates on the surface during heat treatment of the present alloy steel strip, and deteriorates the plating property. If this P exceeds 0.003%, the plating property intended in the present invention cannot be obtained, so the upper limit is 0.003%. A more preferred P content for solderability is 0.001% or less.

Cr forms a strong oxide film on the surface during heat treatment of the steel strip of the present alloy, and deteriorates the plating property. Cr is 0.0
If it exceeds 5%, the plating properties intended in the present invention cannot be obtained, so the upper limit was made 0.05%. A more preferable Cr content for solderability is 0.02% or less.

H is an element that has a large effect on the plating properties of the alloy of the present invention. That is, H is inevitably mixed during the melting of the present alloy, and the amount is 1.0 in the prior art.
ppm, and in some cases about 4 to 5 ppm remained. This gas was released when the die bonding was heated after Ag spot plating in the IC manufacturing process, and the plating layer and the base alloy (lead frame material) To the interface of
Plating failure called "swelling" results. This phenomenon was not a problem from the viewpoint of the strength of the plating layer when the thickness of the Ag plating layer was relatively thick, which was about 3 μm in the related art. The plating thickness is also becoming general. With such an Ag plating thickness, the strength of the Ag plating layer becomes smaller than the gas pressure of H, and the above-mentioned problem of “swelling” has become apparent. Further, even when soldering to this kind of alloy containing the conventional level of H, there is a problem that the wettability of the solder is inferior.

The adverse effect on the plating property due to the presence of a very small amount of H as described above includes martensite (α ') as in the alloy of the present invention as compared with the conventional austenitic single phase such as 42 alloy and Kovar. In particular, clarify.

If the above-mentioned H exceeds 1.0 ppm, the plating property as intended by the present invention cannot be obtained in such an alloy, so that the upper limit is set. In order to obtain such a level of H as defined in the present invention, it is necessary to optimize the vacuum degassing method during melting. That is, in order to reduce the apparent hydrogen partial pressure, in the alloy of the present invention, a method such as achieving a high vacuum degree of 0.1 Torr or less at the time of degassing or increasing the amount of the bottom blow diluted Ar gas may be employed. preferable.

In order to improve the corrosion resistance while securing the low thermal expansion characteristics, high strength and excellent repeated bending characteristics and plating properties intended in the present invention, it is essential to add an appropriate amount of Mo. If the Mo content is less than 0.01%, the corrosion resistance cannot be improved, while if it exceeds 1.0%, the thermal expansion characteristics and plating properties intended in the present invention are impaired. From the above, the addition amount of Mo is determined to be 0.01 to 1.0%.

In the alloy of the present invention, for controlling the structure,
Since the C content is higher than that of the conventional alloy, the corrosion resistance is liable to be deteriorated if this C exists at the crystal grain boundary or the phase boundary. It is considered that Mo improves corrosion resistance through grain boundaries where corrosion resistance is extremely deteriorated and grain boundary segregation and concentration at the phase boundary between austenite and martensite.

In the present invention, in addition to Mo described above,
By containing one or more of B, Nb, Ti, Zr, Ta, V, and W in a total amount of 0.01 to 0.50%, the corrosion resistance of the alloy is improved by other properties intended in the present invention. It can be further improved without deterioration. In this case, the added amount is 0.01%
If it is less than 0.5%, no further improvement in corrosion resistance is observed, while if it exceeds 0.5%, the thermal expansion characteristics and plating properties intended in the present invention cannot be obtained. From these facts, 0.01 to 0.50% was determined as an addition amount for further improving the corrosion resistance.

The final structures are an austenite phase (meaning a retained austenite phase and a reverse transformed austenite phase; the same applies hereinafter) and a work-induced martensite phase. Does not provide the intended thermal expansion characteristics. If the austenite phase exceeds 90% or the reverse transformation austenite exceeds 20%, the strength of the alloy intended in the present invention cannot be obtained.
0% or less, and the reverse transformation austenite was 20% or less.

The retained austenite in the present invention is as follows. In the present invention, a part of the austenite phase after annealing is cold-rolled, part of which undergoes work-induced transformation to become martensite, and the other part remains untransformed as austenite. This austenite is called retained austenite. In addition, the term “reverse transformed austenite” means that the above-mentioned work-induced transformed martensite is reverse transformed into austenite during the final heat treatment. However, the amount of austenite in the present invention is the sum of the above-mentioned retained austenite and reverse transformed austenite.

The amount (%) of the austenite phase in the present invention was determined from the following X-ray diffraction intensity.
The amount (%) of the retained austenite phase is a value before the low-temperature heat treatment, and the inverse transformed austenite amount (%) is the difference between the amount of the austenite after the low-temperature heat treatment and the amount of the retained austenite.

[0038]

(Equation 1)

In order to further improve the repetitive bending characteristics of the present alloy, it is important to control the final grain size of the structure in addition to the above-mentioned components. The present inventors have investigated the relationship between the grain size and the repeated bending characteristics of the alloys having the components and the amount of the austenite phase in the final structure within the range specified in the present invention. As a result, the repetitive bending characteristics were 4 with the grain size of No. 8 or more.
It has been found to show an excellent level of times or more. From this, in the present invention, No. 8 or more was determined as the range of the crystal grain size at which excellent repetitive bending characteristics were obtained. In addition,
The sized structure means a structure that does not contain coarse particles having a crystal grain size of No. 7 or less.

Next, in the method for producing an alloy of the present invention,
In order to obtain the above structure (austenite amount, crystal grain size), a process of repeating cold rolling and annealing twice, then performing cold rolling and performing low temperature heat treatment without subjecting the cold rolled material to solution treatment. It is necessary to take and optimize the conditions in each step. In addition, the cold-rolled material in the present invention was obtained by strip casting, in which a cold-rolled material was cast directly from a hot-rolled steel strip or molten steel, or a steel strip produced by a strip casting method, which was hot-pressed and lightly reduced. Means steel strip.

That is, the primary cold rolling rate (CR ₁ ), the secondary cold rolling rate (CR ₂ ), the annealing temperature after the primary cold rolling and the secondary cold rolling rate (T
₁ ) By properly setting the tertiary cold rolling rate (CR ₃ ), the low temperature heat treatment temperature (T ₃ ), and the heat treatment time (t) as shown in the following equation (2), the target structure of the present invention can be accurately obtained. Can be.

[0042]

CR ₁ : 60 to 80% T ₁ : 700 to 740 ° C. CR ₂ : 75 to 85% T ₂ : 700 to 740 ° C. CR ₃ : 20 to 70% T ₃ : 400 to 540 ° C. t: 0. 5-60min

That is, if CR ₁ is less than 60% and / or CR ₂ is less than 75%, the final structure is
A coarse grain structure of less than No. 8 was obtained, and the repeated bending characteristics intended in the present invention could not be obtained. On the other hand, when CR ₁ exceeds 80% and / or CR ₂ exceeds 85%, the final structure has a grain size of No. 7
A mixed grain structure containing the following coarse grains is obtained, and the repeated bending characteristics intended in the present invention cannot be obtained. Each CR ₁ and CR ₂ from these things, CR _1: 60~80%, C
R ₂ : 75 to 85%.

The annealing temperature after the first cold rolling and the second cold rolling is 7
It is necessary to set it to 00 to 740 ° C. That is, if the annealing temperature is lower than 700 ° C., a complete recrystallized structure cannot be obtained after annealing, and even if the manufacturing conditions other than the annealing temperature are within the specified values of the present invention, the final structure has a grain size. A mixed grain structure containing coarse grains of No. 7 or less is not obtained, and the repeated bending characteristics as intended in the present invention cannot be obtained. If the annealing temperature exceeds 740 ° C., the grain size after annealing becomes a coarse grain structure of No. 7 or less, and even if the manufacturing conditions other than the annealing temperature are within the specified range of the present invention, the final structure is the grain size. No. 7 or less coarse grains and a mixed grain structure, and the repeated bending characteristics as intended in the present invention cannot be obtained.

As described above, in the present alloy, the annealing temperature was set at 700 to 740 ° C. as an annealing condition for obtaining a grain-size structure having a final grain size of No. 8 or more.

Control of the structure, mechanical properties, and thermal expansion properties of the material that has undergone the above-described steps is provided by optimizing the rolling reduction and appropriate low-temperature heat treatment in the final cold rolling (third cold rolling). . In other words, FIG.
When R ₁ , CR ₂ , T ₁ , and T ₂ are the final cold-rolled materials and the mechanical properties after low-temperature annealing (tensile properties,
The relationship between the repeated bending characteristics, hardness), the amount of austenite, the coefficient of thermal expansion, and the final cold rolling reduction is shown. From FIG. 1, when the cold rolling reduction before the low-temperature heat treatment is less than 20%, the strength, And hardness cannot be obtained. On the other hand, the cold rolling rate is 70
%, The strength and hardness intended in the present invention are obtained, but the levels intended in the present invention with respect to the repeated bending characteristics and the coefficient of thermal expansion are not obtained. In addition, when the cold rolling reduction is 20% or more, the amount of retained austenite is 90% or less, and when it is 70% or more, it becomes 30% or less. The amount of reverse transformed austenite after the low temperature treatment is 5% at a cold rolling reduction of 70%, and is 7% at a cold rolling reduction of 80%.

From the above technical relationships, the amount of austenite at which the strength, hardness, cyclic bending characteristics, and coefficient of thermal expansion intended in the present invention are obtained is 30 to 90%, and this amount of austenite is obtained. 20 as cold rolling rate
７０70% respectively.

In the present invention, as shown in FIG. 1, appropriate low-temperature annealing after the final cold rolling described above improves the thermal expansion characteristics and the repeated bending characteristics without changing the strength. .

The heat treatment is performed at a temperature lower than 400 ° C. and / or
If the time is less than 0.5 minutes, sufficient improvement in properties cannot be obtained, while if it exceeds 540 ° C. and / or exceeds 60 minutes, reverse-transformed austenite is formed in the alloy in excess of 20%. The intended strength cannot be obtained. This reverse-transformed austenite has a lower dislocation density than other metal phases (retained austenite and work-induced martensite), and the presence of this phase deteriorates repeated bending characteristics and corrosion resistance. Based on these facts, low-temperature heat treatment conditions exhibiting excellent repeated bending characteristics and corrosion resistance were determined as follows.

[0050]

T ₃ : 400 to 540 ° C. t: 0.5 to 30 min

In the present invention, the austenite by the reverse transformation may be contained in the range of 20% or less.
In this case, the inverse transformed austenite needs to be uniformly and finely dispersed so as not to deteriorate the strength, the repeated bending workability and the corrosion resistance.

In the method for producing an alloy as described above, by selecting conditions appropriately within the specified value of the present invention according to the composition of the alloy, more excellent characteristics (strength, repeated bending characteristics, heat Expansion properties).

Note that α _30-400 ^. _{As for C} (average coefficient of thermal expansion from 30 ° C. to 400 ° C.), hardness and tensile strength, as a result of studying the package assembling process and use conditions, α
_30-400 ^. _C is (4-8) × 10 ⁻⁶ / ° C., hardness H _V ≧ 28
0, since the tensile strength is 85 kgf / mm ² or more, which can sufficiently withstand use, the above-mentioned characteristic values are set in the range of the present invention.

[0054]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific examples according to the present invention will be described in more detail as follows.

Example 1 The ingots of the present invention and comparative alloys having the chemical components shown in Table 1 were melted and cast in a vacuum melting furnace, and subjected to slab rolling, hot rolling, descaling and descaling and surface flaw removal. Do,
A cold-rolled material having a thickness of 2.5 mm was obtained.

[0056]

[Table 1]

The cold-rolled material obtained as described above is then subjected to primary cold-rolling (rolling reduction 60%) → annealing (730 ° C. × 2 mi)
n) → Secondary cold rolling (75% reduction) → Annealing (720 ° C x 2mi)
n) → Third cold rolling (60% reduction) → Low temperature heat treatment (500 ℃
X 10 min) to obtain an alloy thin plate having a thickness of 0.10 mm. Also, for each alloy plate obtained in this way,
Each characteristic value as shown in the following Tables 2 and 3 was investigated.

[0058]

[Table 2]

[0059]

[Table 3]

In Table 2, the amount of austenite was determined by the X-ray diffraction technique as described above. The Ag plating property in Table 3 is as follows. The alloy thin plate is subjected to solvent degreasing, electrolytic degreasing, and acid treatment, and then subjected to Cu strike plating with a thickness of 0.5 μm, followed by Ag plating with a thickness of 2 μm, and 450 ° C.
The plating layer was heated in the air for 5 min, and the presence or absence of blisters on the plating layer was investigated by magnifying 50 times.

The solderability shown in Table 3 was 1.5 μm on the alloy thin plate.
Using a tin-plated material having a thickness of m and a meniscograph method, the solder composition is set to 60% Sn, 40% Pb, solder bath temperature 235 ° C. ± 5 ° C., solder bath immersion depth 2 mm, and solder bath immersion time 5 seconds. It was immersed in the sample and evaluated at a solder wetting time t ₂ . The corrosion resistance was evaluated by conducting a salt spray test according to JIS Z 2371 on the alloy thin plate for 100 hours, and then examining the frequency of rust spots.

From the results shown in Tables 2 and 3, the samples No. 1 to N
Each material of o.7 satisfies the component rules of the present invention,
It shows the texture, mechanical properties, thermal expansion properties, plating properties and corrosion resistance intended in the present invention. In particular, Samples No. 1 to No. 3 and No. 7 have higher Si, P, S, O,
Cr has been reduced to a more preferable level, indicating a more excellent level of solderability. Sample N
o.1, No. 3 to No. 7 are elements in which, in addition to Mo, additional corrosion resistance improving elements are added within the scope of the present invention, compared to Sample No. 2 in which those elements are not added. It is clear that the frequency of spot rust occurrence is low and the corrosion resistance is more excellent.

Compared to these invention examples, in sample No. 8, the C content exceeded the upper limit specified in the present invention, the austenite amount exceeded the upper limit specified in the present invention, and the required strength was obtained. No plating property is inferior. Also sample
No. 9 is a case where the amount of C and the amount of 2Ni + Co + Mn are less than the lower limit of the present invention, and the amount of austenite is less than the specified value of the present invention, and the required thermal expansion characteristics are not obtained.

[0064] Furthermore, sample No.10 is Si amount is above the upper limit specified by the present invention, also less than 2Ni + Co + Mn amount present invention defines the lower limit, the austenite has become less than the lower limit of the present invention defined alpha _{30- 400} ^. _C exceeds 8 × 10 ⁻⁶ / ° C., and has poor thermal expansion characteristics and poor plating properties. In sample No. 11, the amount of Mn exceeded the upper limit specified in the present invention, and the amount of austenite exceeded the upper limit specified in the present invention, and the required strength was not obtained. On the other hand, sample No. 12
The Mn content is less than the lower limit specified in the present invention, and austenite is lower than the lower limit specified in the present invention, and the required thermal expansion characteristics are not obtained.

Samples No. 13, No. 14, No. 15, No. 16 and No. 17 each had a P content, S content, N content, O content and Cr content exceeding the upper limits specified in the present invention. In any case, the plating properties are inferior to those of the examples of the present invention. Particularly, in samples No. 14 and No. 16, the repeated bending characteristics are further inferior to those of the other comparative examples.

In sample No. 19, the amount of H exceeds the upper limit specified in the present invention, and the plating property is inferior to those of the examples of the present invention. In Samples Nos. 20 and 21, the amount of 2Ni + Co + Mn exceeded the upper limit specified in the present invention. In each case, the amount of austenite exceeded the upper limit specified in the present invention, and the required strength was not obtained. Also, the Si content exceeds the upper limit specified in the present invention, and the plating property is inferior.

In particular, samples No. 20 and No. 21 are disclosed in
Although the alloys found in 6340 were examined, none of the materials achieved the Ag plating properties, solderability, and corrosion resistance intended in the present invention, and the effects intended in the present invention were achieved with the prior art alone. Obviously not. Sample No. 18 is a case where Mo is less than the present invention, the frequency of rust generation is remarkably higher than that of the present invention, the corrosion resistance is inferior, and in the present invention, addition of an appropriate amount of Mo is essential. It is understood that.

As described above, in order to obtain the texture, mechanical properties, thermal expansion properties, plating properties, and corrosion resistance intended in the present invention, it can be achieved only when the component specifications of the present invention are satisfied. It became clear in the examples.

Example 2 An ingot having the composition of sample No. 1 in Table 1 was subjected to slab-rolling, hot rolling, descaling, and descaling of a steel ingot that had been melted and cast in a vacuum melting furnace. Performed to obtain cold rolled material. Thereafter, a series of processing shown in the following Table 4 was performed, and the sheet thickness was 0.10.
An alloy thin plate having a thickness of 1 mm was obtained, and the characteristic values as shown in Tables 5 and 6 were investigated in the same manner as in Example 1.

[0070]

[Table 4]

[0071]

[Table 5]

[0072]

[Table 6]

From the above Tables 4 to 6, samples No. 22 to No. 29
Satisfies all the manufacturing conditions defined in the present invention, and shows the structure, mechanical properties, thermal expansion properties, plating properties and corrosion resistance intended in the present invention. On the other hand, sample No. 30
, No. 34 are cases where CR ₁ and CR ₂ respectively exceed the upper limit specified in the present invention, the structure is a mixed grain, and the required repeated bending characteristics are not obtained. In addition, sample No. 31
, No. 35 is the case where CR ₁ and CR ₂ are respectively less than the lower limit of the present invention, and the structure is such that the crystal grain size number is lower than the lower limit of the present invention, and the required repetitive bending characteristics can be obtained. Not.

Further, in Samples No. 32 and No. 36, T ₁ and T ₂ respectively exceeded the upper limit specified in the present invention, the structure was mixed, and the grain size No. was lower than the lower limit specified in the present invention. The required bending characteristics were not obtained. Samples No. 33 and No. 37 are T ₁ and T ₂ respectively.
Is less than the lower limit of the present invention, the structure is a mixed grain, and the required repetitive bending characteristics are not obtained.

As described above, the control of the primary and secondary cold rolling rates and the annealing temperature is extremely important for the crystal grain size and the uniform grain size of the structure, and it can be seen that the control can improve the repeated bending characteristics. Understood.

Further, Samples No. 38 and No.
R ₃ exceeds the upper limit and less than the lower limit of the present invention. In the former, the amount of austenite is less than the lower limit specified in the present invention, and required thermal expansion characteristics and repetitive bending characteristics are not obtained. In the latter, the amount of austenite exceeds the upper limit specified in the present invention, and the required strength is not obtained.

Sample No. 40 was not subjected to the final heat treatment, and the required repetitive bending characteristics were not obtained. In Samples No. 41 and No. 43, T ₃ and t exceeded the upper limits specified in the present invention, and the amount of retained austenite before the final heat treatment was 40%.
In No. 1, 20% of austenite was formed by the reverse transformation, and in No. 43, austenite by the reverse transformation was 11%.
% Had been produced. These materials do not have the required strength and repetitive bending characteristics, and are inferior in plating properties and corrosion resistance as compared with the examples of the present invention. Sample No.42, No.44
Has T ₃ and t respectively less than the lower limits specified in the present invention, and does not have the required repeated bending characteristics.

As can be seen from the above samples Nos. 40 to 44, it is necessary to provide an appropriate final heat treatment in order to obtain the structure, mechanical properties, thermal expansion properties, plating properties and corrosion resistance intended in the present invention. It is understood that there is.

Sample No. 45 is a case where the manufacturing method characterized in Japanese Patent Application Laid-Open No. 3-166340 was adopted. The amount of austenite exceeded the upper limit specified in the present invention, the structure was mixed grains, and the crystal grain size No. Exceeds the upper limit of the present invention. The amount of austenite was 29% before the secondary annealing, and 63% of reverse transformed austenite was generated by the secondary annealing. This material is inferior in required strength, repetitive bending characteristics, plating property, and corrosion resistance as compared with the examples of the present invention, and it is clear that the effects intended by the present invention have not been achieved by the conventional technology.

That is, according to the present invention, the cold-rolled material is not subjected to a solution treatment such as 1000 ° C. for 1 hour, and by omitting the solution treatment, the crystal grain size and the uniform grain size of the final structure can be adjusted. Is possible.

As described above, the definition of the production conditions in the present invention is also an important requirement in order to accurately obtain the target structure, mechanical properties, thermal expansion characteristics, plating properties and corrosion resistance in the present invention.

[0082]

According to the present invention as described above, a high strength required for a multi-pin thin-plate lead frame with a specific composition of Fe-Ni-Co system, excellent repetitive bending characteristics, and required thermal expansion characteristics are obtained. Provide alloy thin plate having both plating property, corrosion resistance, etc., and control the final structure and austenite amount of alloy of the above composition by optimizing cold rolling after hot rolling, annealing conditions and final cold working and heat treatment. This is an invention capable of appropriately producing the alloy thin plate, and is industrially effective.

[Brief description of the drawings]

FIG. 1 shows tensile strength, hardness, cyclic bending characteristics, α _{30-400 of an} Fe—Ni—Co alloy ^. ₃ is a table showing the relationship between _C and austenite content and final cold rolling reduction.

[Explanation of symbols]

In the above chart, the solid was subjected to a low-temperature heat treatment (500 ° C.).
× 10 min), open indicates low temperature heat treatment.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-65602 (JP, A) JP-A-4-176844 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00 302 C21D 8/02 C21D 9/46

Claims (5)

(57) [Claims] (1) In wt%, Ni: 27 to 30%, Co: 5-1.
8%, Mn: 0.10-3.0%, Si: 0.10% or less, and when the content of Ni, Co and Mn is less than 10%, 63.5% ≦ 2Ni + Co + Mn ≦ 65. 0%, Co: 10% or more satisfies the following relationship: 69.5% ≦ 2Ni + Co + Mn ≦ 72.5%, C: 0.020 to 0.070%, N: 0.010% or less, H:
1.0 ppm or less, S: 0.0030% or less, P: 0.003% or less, O: 0.0
040% or less, Cr: 0.05% or less, Mo: 0.01 to 1.0%, the balance consisting of Fe and unavoidable impurities, the austenite content in the structure is 30 to 90%, and the crystal grain size is small.
A high-strength Fe-Ni-Co alloy sheet with excellent corrosion resistance and repetitive bending characteristics characterized by a grain size of No. 8 or more. 2. In addition to the components of claim 1, B, Nb, Ti, Z
One or more of r, Ta, V and W are 0.0 in total.
A high-strength Fe containing 1 to 0.50% and having the structure according to claim 1, having excellent corrosion resistance and repetitive bending characteristics.
-Ni-Co alloy sheet. 3. An average coefficient of thermal expansion at 30 to 400 ° C. is (4)
~8) × 10 ^-6 / ℃, Vickers hardness (H _V) at least 280 Hardness, claim tensile strength is characterized in that it is 85 kgf / mm ² or more 1 or 2 corrosion resistance according to, repeated High strength Fe-Ni-Co alloy thin plate with excellent bending characteristics. 4. A thin sheet is produced from a cold-rolled material of the alloy having the composition of claim 1 in the steps of primary cold rolling, primary annealing, secondary cold rolling, secondary annealing, tertiary cold rolling and low temperature heat treatment. At this time, the primary cold rolling rate (CR ₁ ) is 60 to 80%, the primary annealing temperature (T ₁ ) is 700 to 740 ° C., the secondary cold rolling rate (CR ₂ ) is 75 to 85%, 2 The secondary annealing temperature (T ₂ ) is 700 to 740 ° C., the third cold rolling reduction (CR ₃ ) is 20 to 70%, the low temperature heat treatment temperature (T ₃ ) is 400 to 540 ° C. The low temperature heat treatment time (t) 0.5-60 min. A method for producing a high-strength Fe-Ni-Co alloy thin plate having excellent corrosion resistance and repeated bending characteristics. 5. A thin plate is produced from a cold rolled material of the alloy having the composition of claim 2 in the steps of primary cold rolling, primary annealing, secondary cold rolling, secondary annealing, tertiary cold rolling and low temperature heat treatment. At this time, the primary cold rolling rate (CR ₁ ) is 60 to 80%, the primary annealing temperature (T ₁ ) is 700 to 740 ° C., the secondary cold rolling rate (CR ₂ ) is 75 to 85%, 2 Next annealing temperature (T ₂ ): 700 to 740 ° C., third cold rolling reduction (CR ₃ ): 20 to 70%, Low temperature heat treatment temperature (T ₃ ): 400 to 540 ° C., Low temperature heat treatment time (t) From 0.5 to 60 min. A method for producing a high-strength Fe-Ni-Co alloy thin plate having excellent corrosion resistance and repeated bending characteristics.