JPH05306436A - High strength fe-ni-co alloy sheet excellent in corrosion resistance and repeated bendability and its production - Google Patents

Abstract

PURPOSE:To produce an IC lead frame material haying high strength and excellent in corrosion resistance and repeated bendability. CONSTITUTION:This material has a composition consisting of, by weight, 27-30% Ni, 5-18% Co, 0.10-3.0% Mn, <=0.10% Si, 0.020-0.070% C, <=0.010% N, <=1.0ppm H, <=0.0030% S, <=0.03% P, <=0.0040% O, <=0.05% Cr, 0.01-1.0% Mo, and the balance Fe with inevitable impurities and satisfying either 63.5%<=2Ni+Co+ Mn<=65.0% (when Co<10%) or 69.5%<=2Ni+Co+Mn<=72.5% (when Co>=10%). Further, the amount of austenite in the structure is regulated to 30-90% and the grains are graded to grain size No.8 or above.

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 sheet excellent in corrosion resistance and cyclic bending characteristics and a method for manufacturing the same, and is a material for an IC lead frame having high strength and excellent corrosion resistance and cyclic bending characteristics. And a preferable method for producing the same.

[0002]

2. Description of the Related Art In recent years, with the high integration of semiconductors and the thinning of packages, the lead frame has a large number of pins,
Since there is a tendency toward thinning, there is a demand for higher strength in lead frame materials.

However, as the Fe-based high-strength lead frame material for a large number of pins as described above, there has been recently been disclosed in JP-A-3-6633.
Publication No. 40 is proposed. That is, in this disclosed technology, Fe
-Controlling the amount of Ni and Co in a -Ni-Co alloy and precipitating a reverse transformation austenite phase by work-induced martensitic transformation with a specific working ratio and subsequent annealing, and forming 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 achieved.

[0004]

According to the conventional technique as described above, H _V = 270 to 380 and tensile strength 85 to 117.
kgf / mm ² , average coefficient of thermal expansion α _RT-300 = 5.2-8.5 × 10
^It has characteristics of ^-6 / ° C and excellent silver plating property, solder property, and crevice corrosion property, but it still has the following problems. (1) There is a problem in the corrosion resistance of the material. (2) The repeated bending property (bending workability) is inferior. (3) With high strength materials of H _V 275 or higher, α _RT-300 is 6.8 ×
It has a high coefficient of thermal expansion of 10 ⁻⁶ / ° C. or higher, and there is a high risk that the Si chip will be damaged by thermal strain when the Si chip is mounted on the lead frame in the IC manufacturing process.

The above-mentioned corrosion resistance of this material is martensite +
Corrosion between martensite and retained austenite having a high dislocation density is likely to occur because the austenite phase having a two-phase structure of austenite and the austenite phase mainly formed by reverse transformation and having a low dislocation density are mainly formed. It was markedly inferior. Due to the characteristics of the product, rust is generated on the surface of the material after the coil is manufactured and before slitting and fine processing of the lead frame are performed, causing a serious problem. Normal 42 alloy (Fe-
42 wt% Ni) has no such problems, it is a low Ni alloy with Ni of 32.5% or less like this material, and that metal phases with different dislocation densities coexist in the same material. However, it is speculated that this is the main cause of deterioration in corrosion resistance.

The cyclic bending property is also deteriorated by the above-mentioned characteristic of the present material, that is, the presence of a large amount of reverse transformation austenite having a low dislocation density and a low strength with respect to martensite having a high dislocation density and a high strength. To do.

Further, the thermal expansion characteristics are also impaired with an increase in the amount of martensite due to the work-induced transformation during cold rolling, which is a feature of this technique, when further strengthening is intended. Further, the balance of thermal expansion and high strength, which is a feature of the present technology, cannot immediately meet 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., the strength satisfies the tensile strength of 120 kgf / mm ² or more, and the composition and the structural range cannot be determined by this technique.

Incidentally, due to the recent demand for further cost reduction of the lead frame, the tendency of thinning Ag plating has been strengthened, and the thickness of Ag plating (3 μm) seen in the present technology has become thinner. In response to such a demand, the present situation is that the alloy featuring in the present technology has a problem of Ag plating property. Further, the solderability of the present alloy has achieved high performance in the above-mentioned Japanese Patent Laid-Open No. 3-166340 in terms of weather resistance, but no technique has been found to be improved in terms of wettability.

[0009]

Means for Solving the Problems The present invention has been studied to solve the problems in the prior art as described above, and to specify the composition and the structure in this kind of Fe-Ni-Co alloy. Have succeeded in achieving the object effectively and establishing a preferable manufacturing method thereof, and are as follows.

In wt%, Ni: 27-30%, Co: 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% Co: 6
3.5% ≦ 2Ni + Co + Mn ≦ 65.0%, and when Co: 10% or more, the relationship of 69.5% ≦ 2Ni + Co + Mn ≦ 72.5% is satisfied, and C: 0.020 to 0.070%, N : 0.010% or less, H: 1.0 ppm or less, S: 0.0003% or less, P: 0.0.
003% or less, O: 0.0040% or less, Cr: 0.05% or less, Mo: 0.01 to 1.0%, and the balance Fe and unavoidable impurities. Further, the amount of austenite in the structure is Three
High-strength Fe with excellent corrosion resistance and cyclic bending characteristics characterized by 0-90% and grain size control of No. 8 or more
Ni-Co alloy thin plate.

In addition to the above components, B, Nb, Ti, Z
One or two or more of r, Ta, V and W in total of 0.0
High strength Fe excellent in corrosion resistance and cyclic bending characteristics, characterized by containing 1 to 0.50% and having the structure of claim 1.
-Ni-Co alloy thin plate.

The average thermal expansion coefficient at 30 to 400 ° C. is (4 to 8) × 10 ⁻⁶ / ° C., the hardness is 280 or more in Vickers hardness (H _V ), and the tensile strength is 85 kgf / mm ² or more. Corrosion resistance according to the above or characterized by
A high-strength Fe-Ni-Co alloy sheet with excellent cyclic bending properties.

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

The cold-rolled material of the alloy having the above composition is used in the following steps: primary cold-rolling-primary annealing-secondary cold rolling-secondary annealing-tertiary cold rolling-low temperature heat treatment. Cold rolling rate (CR ₁ ) is 60 to 80%, primary annealing temperature (T ₁ ) is
700 to 740 ° C., secondary cold rolling rate (CR ₂ ) of 75 to 85
%, Secondary annealing temperature (T ₂ ), 700 to 740 ° C., tertiary cold rolling rate (CR ₃ ) 20 to 70%, low temperature heat treatment temperature (T ₃ ).
400 to 540 ° C., low temperature heat treatment time (t), 0.5
A method for producing a high-strength Fe-Ni-Co alloy sheet having excellent corrosion resistance and repeated bending properties, which is characterized by setting the time to -60 min.

[0015]

In the present invention as described above, the reason for limiting the chemical composition of the alloy will be explained by wt% (hereinafter simply referred to as "%"). The low thermal expansion characteristics, high strength and excellent repeated bending characteristics and corrosion resistance intended by the present invention will be explained. It is necessary to properly control the amount of austenite in the structure, especially the amount of retained austenite, in order 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 starting temperature of martensite becomes high, austenite becomes unstable, and martensite transformation occurs in the cooling process during solution treatment, and Co, Ni, and Mn as described below are generated. Even if the amount is optimized, the amount of retained austenite intended in the present invention cannot be obtained, and the plating property cannot be the level of the present invention, so 0.10% was made the upper limit. A more preferable Si amount for improving the solderability is 0.
It is 05% or less.

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 deteriorates. Therefore, the Co content is set in the range of 5 to 18%.

When Ni is less than 27% or more than 30%,
The coefficient of thermal expansion increases, and the thermal expansion matching with the silicon chip deteriorates. Therefore, the Ni content is set to the range of 27 to 30%.

If Mn exceeds 3.0%, austenite becomes stable, and it becomes difficult for work-induced transformation to occur. Also, 0.1%
When it is less than 1, the martensite start temperature is high, austenite becomes unstable, and the work-induced martensite transformation is likely to occur during cold working, and as a result, a sufficient retained austenite amount cannot be obtained. From these facts, the upper limit and the lower limit of the amount of Mn were set to 3.0% and 0.1%, respectively.

In order to obtain the characteristics intended by the present invention,
The total amount of Ni, Co, and Mn must be controlled according to the Co amount, in addition to the above-mentioned regulation of the individual addition amount. That is, when Co is less than 10%, (2Ni + Co + Mn) is 63.5%
In the case of less, and when Co is 10% or more, (2Ni + Co
When + Mn) is less than 69.5%, the martensite start temperature is high, austenite becomes unstable, work-induced martensite transformation is likely to occur, and as a result, a sufficient retained austenite amount cannot be obtained. Also, if Co is less than 10%, (2Ni + Co + Mn) exceeds 65.0%, or Co is 10%.
%, When (2Ni + Co + Mn) exceeds 72.5%, the austenite becomes stable and the work-induced martensite transformation hardly occurs. Therefore, when Co is less than 10%, 63.5% ≦ 2Ni + Co + Mn ≦ 65.0%, and when Co is 10% or more, 69.5% ≦ 2Ni + Co + Mn ≦ 72.5%.
Co and Mn are limited.

In the present invention, C and N are essential elements for properly controlling the work-induced martensitic transformation and achieving higher strength during the final aging treatment. That is, first, when C is less than 0.020%, austenite becomes unstable, work-induced martensitic transformation is likely to occur, and as a result, sufficient retained austenite cannot be obtained, and strength increase due to age hardening cannot be expected. .. On the other hand, if it exceeds 0.070%, austenite becomes stable on the contrary, work-induced martensitic transformation becomes difficult to occur, and the plating property deteriorates. Therefore, C is
The lower limit was 0.020% and the upper limit was 0.070%.

If N exceeds 0.010%, austenite becomes stable, work-induced martensite transformation is less likely to occur, and the plating property is further deteriorated. Therefore, N is 0.
The upper limit is 010%. The addition of N in the range of 0.01% or less has the effect of increasing the strength by age hardening. If N is in the range of 0.010% or less, all of the low thermal expansion characteristics intended in the present invention, high strength and excellent repeated bending characteristics, corrosion resistance, and plating property can be obtained.

Further, in the present invention, in addition to the above-mentioned compositional regulation, in order to improve the cyclic bending property, the S content,
It is necessary to reduce the amount of O. In order to further improve the plating property of the present alloy, which is intended in the present invention, H, S, P, O
And Cr reduction is essential.

That is, S and O are elements that adversely affect the repetitive bending properties and plating properties of the present alloy through the formation of non-metallic inclusions. If S exceeds 0.0030%, the cyclic bending property deteriorates and the plating property does not attain the level intended by the present invention, so 0.0030% was made the upper limit. A more preferable S content for soldering is 0.0010% or less.

If the O content exceeds 0.0040%, the present alloy deteriorates the repeated bending property and the plating property does not reach the level intended by the present invention, so 0.0040% was made the upper limit. More preferable O content for soldering is 0.0020%
It is below.

The mechanism by which the presence of S and O deteriorates the cyclic bending property is that, in the case of the present alloy, a large number of non-metallic inclusions in which S or O is detected are found at the interface where bending and fracture occur. It is conceivable to promote cracking starting from these inclusions.

Further, in the alloy of the present invention, in order to bring the plating property to the level intended in 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 the heat treatment of the 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 0.003% was made the upper limit. A more preferable P amount for soldering property is 0.001% or less.

[0028] 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 property intended in the present invention cannot be obtained, so 0.05% was made the upper limit. A more preferable amount of Cr for solderability is 0.02% or less.

H is an element having a great influence on the plating property of the alloy of the present invention. That is, H is inevitably mixed during the melting of this alloy, and its amount is 1.0
It is more than 4 ppm, and in some cases remains about 4 to 5 ppm. This gas is released during the heating of the die bonding after Ag spot plating in the IC manufacturing process, and the plating layer and the base alloy (lead frame material). Move to the interface of
It causes plating failure called “blister”. 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 comparatively thick, about 3 μm, but due to the recent tendency of Ag thinning, it is 2 μm or less. The plating thickness is becoming common, and 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 "blister" problem has become apparent. Further, there is a problem that the wettability of solder is inferior even when soldering to this kind of alloy containing the conventional level of H.

As described above, the adverse effect on the plating property due to the presence of an extremely small amount of H includes martensite (α ') as in the alloy of the present invention as compared with the conventional austenite single phase alloy such as 42 alloy or Kovar. In particular, it will be clarified.

When the above-mentioned H exceeds 1.0 ppm, the plating property intended by the present invention cannot be obtained in such an alloy, so this was made the upper limit. It is necessary to optimize the vacuum degassing method at the time of melting in order to obtain such a level of H amount defined in the present invention. That is, in order to reduce the apparent hydrogen partial pressure, in the alloy of the present invention, it is possible to achieve a high vacuum degree of 0.1 Torr or less at the time of degassing and to adopt a method of increasing the amount of bottom-blown diluted Ar gas. preferable.

In order to improve corrosion resistance while ensuring low thermal expansion characteristics, high strength and excellent repeated bending characteristics and plating properties intended by the present invention, addition of an appropriate amount of Mo is essential. If the amount of Mo 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 by the present invention are impaired. From the above, the addition amount of Mo was determined to be 0.01 to 1.0%.

In the alloy of the present invention, in order to control the structure,
Since the amount of C is higher than that of the conventional alloy, if this C is present at the grain boundaries or phase boundaries, the corrosion resistance is likely to deteriorate. It is considered that Mo improves the corrosion resistance by grain boundary segregation or concentration at the grain boundaries where the corrosion resistance deteriorates locally or at the phase boundaries between austenite and martensite.

In the present invention, in addition to the above Mo,
By containing one or two 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 present alloy can be changed to other characteristics intended by 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%, the corrosion resistance is not further improved, while if it exceeds 0.5%, the thermal expansion characteristics and plating properties intended by the present invention cannot be obtained. From these facts, 0.01 to 0.50% was set as the addition amount for further enhancing the corrosion resistance.

The final structure is an austenite phase (which means a retained austenite phase and a reverse transformation austenite phase. The same applies hereinafter) and a work-induced martensite phase. If the austenite content is less than 30%, the present invention Therefore, the intended thermal expansion characteristics cannot be obtained. Further, 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, so the austenite phase is 30% or more,
The reverse transformation austenite content was set to 0% or less and 20% or less.

The retained austenite used in the present invention is as follows. In the present invention, the austenite phase after annealing undergoes work-induced transformation to martensite by cold rolling, and the other portion remains untransformed as austenite. This austenite is called retained austenite. Further, the reverse transformation austenite means that the above-mentioned work-induced transformation martensite is reverse transformed to 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 obtained from the X-ray diffraction intensity as shown below.
The amount (%) of the retained austenite phase is the value before the low temperature heat treatment, and the reverse transformation austenite amount (%) is the difference between the amount of the austenite after the low temperature heat treatment and the retained austenite amount.

[0038]

[Equation 1]

In order to further improve the cyclic bending property of the present alloy, it is important to control the final texture crystal grain size in addition to the above-mentioned compositional regulation. The present inventors have investigated the relationship between the grain size and the cyclic bending property in alloys in which the amount of the austenite phase of the composition and final structure is within the scope of the present invention. As a result, when the grain size was adjusted to No. 8 or more, the cyclic bending property was 4
It has been found to show excellent levels over and over. From this, in the present invention, No. 8 or more was set as the range of the crystal grain size at which excellent repeated bending properties were obtained. In addition,
The grain size controlled structure means a structure that does not include coarse particles having a grain size of No. 7 or less.

Next, in the method for producing the alloy of the present invention,
In order to obtain the above-described structure (austenite amount, grain size), cold rolling and annealing are repeated twice without solution treatment of the cold rolled material, then cold rolling is performed, and low temperature heat treatment is performed. It is necessary to optimize the conditions in each process. The cold-rolled material in the present invention was obtained by stripping a hot-rolled steel strip or molten steel directly by casting a cold-rolled material, or by lightly rolling a steel strip manufactured by a strip casting method in a hot state. Means steel strip.

That is, the primary cold rolling rate (CR ₁ ), the secondary cold rolling rate (CR ₂ ), the annealing temperature (T after the primary cold rolling and the secondary cold rolling rate (T
₁ ) To properly obtain the target structure of the present invention by setting the third cold rolling rate (CR ₃ ), the low temperature heat treatment temperature (T ₃ ) and the heat treatment time (t) as shown in the following mathematical expressions 2. You can

[0042]

## EQU00002 ## 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, when the CR ₁ is less than 60% and / or the CR ₂ is less than 75%, the final structure has a grain size.
The coarse grain structure is less than No. 8, and the repeated bending properties intended by the present invention cannot be obtained. On the other hand, when CR ₁ exceeds 80% and / or CR ₂ exceeds 85%, the final structure has a grain size No. 7
The mixed grain structure contains the following coarse grains, and the repeated bending properties intended in the present invention cannot be obtained. Each CR ₁ and CR ₂ from these things, CR _1: 60~80%, C
R _2: was defined as 75% to 85%.

The annealing temperature after primary cold rolling and secondary cold rolling is 7
It is necessary to set the temperature to 00 to 740 ° C. That is, when this annealing temperature is less than 700 ° C., a complete recrystallized structure cannot be obtained after annealing, and the final structure has a grain size even if the manufacturing conditions other than the annealing temperature are within the specified values of the present invention. It has a mixed grain structure containing coarse grains of No. 7 or less, and the repeated bending property intended in the present invention cannot be obtained. Further, when 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 has the grain size. Coarse-grained and mixed-grained structure of No. 7 or less cannot be obtained, and the repeated bending property as intended in the present invention cannot be obtained.

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

Control of the structure, mechanical properties and thermal expansion characteristics of the material that has undergone the above-mentioned steps is imparted by optimizing the reduction ratio in final cold rolling (third cold rolling) and appropriate low temperature heat treatment. .. That is, in FIG. 1, the invention alloy No. 1 described later is C
_{R 1, CR 2, T 1} , T 2 is still the final cold rolling of the material in the prescribed present invention, and mechanical properties (tensile properties after low-temperature annealing,
The relationship between the cyclic bending property, the hardness), the amount of austenite, the coefficient of thermal expansion and the final cold rolling rate is shown. From FIG. 1, when the cold rolling rate before the low temperature heat treatment is less than 20%, the strength intended by the present invention, And hardness cannot be obtained. On the other hand, the cold rolling rate is 70
%, The strength and hardness intended by the present invention are obtained, but the levels intended by the present invention regarding the cyclic bending property and the thermal expansion coefficient are not obtained. When the cold rolling rate is 20% or more, the amount of retained austenite is 90% or less, and when it is 70% or more, it is 30% or less. The amount of reverse transformed austenite after the low temperature treatment was 5% at a cold rolling rate of 70% and 7% at a cold rolling rate of 80%.

From the above technical relationships, the amount of austenite that can obtain the strength, hardness, cyclic bending property, and coefficient of thermal expansion intended in the present invention is 30 to 90%, and this amount of austenite is obtained. Cold rolling rate is 20
.About.70% was set for each.

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

This heat treatment is performed below 400 ° C. and / or
If it is less than 0.5 minutes, sufficient improvement in properties cannot be obtained, while if it exceeds 540 ° C. and / or more than 60 minutes, more than 20% of reverse transformed austenite is formed in the alloy. The intended strength cannot be obtained. This reverse transformation austenite has a lower dislocation density than other metal phases (residual austenite and work-induced martensite), and the presence of this phase deteriorates cyclic bending characteristics and corrosion resistance. From these facts, the low temperature heat treatment condition showing excellent cyclic bending property and corrosion resistance was defined as the following formula.

[0050]

[Equation 3] T ₃ : 400 to 540 ° C t: 0.5 to 30 min

In the present invention, however, austenite due to reverse transformation may be contained in the range of 20% or less.
In this case, the reverse transformed austenite must be dispersed uniformly and finely 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, more excellent characteristics (strength, repeated bending characteristics, heat resistance, etc.) can be obtained by appropriately selecting the conditions within the specified values of the present invention according to the composition of the alloy. Expansion characteristics).

It should be _noted that α _30-400 ^. Regarding _C (average coefficient of thermal expansion between 30 ° C and 400 ° _C ), hardness, and tensile strength, as a result of examining the package assembling process and usage conditions, α
_30-400 ^. _C is (4 to 8) × 10 ⁻⁶ / ° C., hardness H _V ≧ 28
The above characteristic values were defined in the range of the present invention, since it has a tensile strength of 85 kgf / mm ² or more and can be sufficiently used.

[0054]

EXAMPLES The details of specific examples according to the present invention will be described below.

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 the ingots were subjected to slab rolling, hot rolling, descaling, and surface flaw removal. Do
A cold rolled material having a plate thickness of 2.5 mm was obtained.

[0056]

[Table 1]

The cold-rolled material obtained as described above is subsequently subjected to primary cold-rolling (reduction of 60%) → annealing (730 ° C. × 2 mi
n) → Secondary cold rolling (75% reduction) → annealing (720 ℃ × 2mi
n) → tertiary cold rolling (60% reduction) → low temperature heat treatment (500 ℃
A series of treatments (× 10 min) were performed to obtain an alloy thin plate having a plate thickness of 0.10 mm. 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 obtained by the X-ray diffraction method described above. As for the Ag plating property in Table 3, the alloy thin plate was subjected to solvent degreasing-electrolytic degreasing-acid treatment, followed by Cu strike plating having a thickness of 0.5 µm, and Ag plating having a thickness of 2 µm, which was 450 ° C x
After heating in the atmosphere for 5 minutes, the presence or absence of blisters on the plating layer was examined 50 times more.

The solderability of Table 3 is 1.5μ on the alloy thin plate.
Solder composition Sn 60%, Pb 40%, solder bath temperature 235 ° C ± 5 ° C, solder bath immersion depth 2mm, solder bath immersion time 5 seconds by meniscograph method using m-thick tin-plated material. It was dipped in and evaluated at a solder wetting time t ₂ . Regarding the corrosion resistance, a salt spray test according to JIS Z 2371 was carried out for 100 hours on the alloy thin plate, and the frequency of rust formation after that was examined.

From the results of Tables 2 and 3 above, sample Nos. 1 to N
Each material of o.7 satisfies the compositional regulations of the present invention,
It shows the structure, mechanical properties, thermal expansion properties, plating properties and corrosion resistance intended in the present invention. In particular, sample No.1 to No.3 and No.7 have Si, P, S, O, compared with sample No.4 to No.6.
Cr is reduced to a more preferable level, and the solderability shows a more excellent level. Also, sample N
o.1 and No.3 to No.7 are those in which, in addition to Mo, within the rules of the present invention, further corrosion resistance improving elements are added, and compared with Sample No.2 in which those elements are not added. It is clear that the frequency of spot rusting is low and the corrosion resistance is better.

Compared with these invention examples, Sample No. 8 had a C content exceeding the upper limit specified in the present invention, and the austenite amount exceeded the upper limit specified in the present invention, and the required strength was obtained. The plating property is also poor. 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 regulation of the present invention, and the required thermal expansion characteristics are not obtained.

Further, in Sample No. 10, the amount of Si exceeds the upper limit of the present invention, the amount of 2Ni + Co + Mn is less than the lower limit of the present invention, and austenite is less than the lower limit of the present invention α _{30- 400} ^. _C exceeds 8 × 10 ⁻⁶ / ° C., the thermal expansion property is poor, and the plating property is also poor. Further, in sample No. 11, the amount of Mn exceeds the upper limit specified in the present invention, and the amount of austenite exceeds the upper limit specified in the present invention, and the required strength is not obtained. On the other hand, sample No. 12
The amount of Mn is less than the lower limit specified in the present invention, and the amount of austenite is less 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 are those in which the amounts of P, S, N, O and Cr exceed the upper limits specified in the present invention. However, the plating properties are inferior to those of the examples of the present invention. In particular, Samples No. 14 and No. 16 have further inferior cyclic bending properties as compared with other comparative examples.

Sample No. 19 had an H content exceeding the upper limit specified in the present invention, and was inferior in plating property to the examples of the present invention. Further, in samples No. 20 and No. 21, the amount of 2Ni + Co + Mn exceeds the upper limit specified in the present invention, and in any case, the amount of austenite exceeds the upper limit specified in the present invention, and the required strength is not obtained. In addition, the amount of Si exceeds the upper limit specified in the present invention, and the plating property is poor.

Especially, the samples No. 20 and No. 21 are described in JP-A-3-16
It is an examination of the alloy found in 6340, but none of the materials has the Ag plating property, solderability, and corrosion resistance intended by the present invention, and the conventional technique alone achieves the intended effect of the present invention. Obviously not. Further, Sample No. 18 is the case where Mo is less than the regulation of the present invention, the rust occurrence frequency is significantly higher than that of the present invention example, the corrosion resistance is inferior, and in the present invention, it is essential to add an appropriate amount of Mo. Be understood.

As described above, in order to obtain the structure, mechanical properties, thermal expansion characteristics, plating properties and corrosion resistance intended by the present invention, it is achieved that the composition of the present invention is only satisfied. It became clear in the examples.

Example 2 With respect to the invention alloy having the components of sample No. 1 in Table 1, the steel ingot that had been melted and cast in a vacuum melting furnace was subjected to slab rolling, hot rolling, descaling and surface flaw removal. Conducted and obtained cold rolled material. After that, a series of treatments shown in the following Table 4 was performed and the plate thickness was 0.10
An alloy thin plate of mm was obtained, and the characteristic values shown in Tables 5 and 6 were investigated by the same method as in Example 1.

[0070]

[Table 4]

[0071]

[Table 5]

[0072]

[Table 6]

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

Further, in Samples No. 32 and No. 36, T ₁ and T ₂ respectively exceed the upper limit specified in the present invention, the structure is mixed grain, and the grain size No. falls below the lower limit specified in the present invention. However, the required repeated bending properties have not been 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 repeated bending properties 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 grain size and grain size control of the structure, and it is possible to improve the cyclic bending property by this control. To be understood.

Further, the samples No. 38 and No. 39 are C
R ₃ is above the upper limit or below 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 the required thermal expansion characteristics and repeated bending characteristics are not obtained. In the latter case, the amount of austenite exceeds the upper limit specified in the present invention, and the required strength is not obtained.

The sample No. 40 was not subjected to the final heat treatment, and the required repeated bending properties were not obtained. Samples No. 41 and No. 43 had T ₃ and t exceeding the upper limits specified in the present invention, and the residual austenite amount before the final heat treatment was 40%, but No. 4
No. 1 produced 20% austenite by reverse transformation, and No. 43 produced 11% austenite by reverse transformation.
% Was generated. These materials do not have the required strength and cyclic bending properties, and are inferior in plating property and corrosion resistance to the examples of the present invention. Sample No.42, No.44
Have T ₃ and t respectively less than the lower limit specified in the present invention, and do not have the required repeated bending properties.

Appropriate final heat treatment, as seen in the above Samples No. 40 to No. 44, is necessary for obtaining the structure, mechanical properties, thermal expansion characteristics, platability and corrosion resistance intended in the present invention. It is understood that there is.

Further, Sample No. 45 is a case where the manufacturing method characterized by Japanese Patent Laid-Open No. 3-166340 is adopted, but the amount of austenite exceeds the upper limit specified in the present invention, the structure is mixed grain, and the grain size is 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 to the examples of the present invention in required strength, repeated bending properties, plating properties, and corrosion resistance, and it is clear that the effects intended by the present invention have not been achieved by the prior art.

That is, according to the present invention, the solution treatment such as 1000 ° C. × 1 hr is not applied to the cold rolled material, and by omitting the solution treatment, the grain size and grain size of the final structure are adjusted. Is possible.

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

[0082]

According to the present invention as described above, the Fe-Ni-Co-based specific composition has a high strength required for a multi-pin thin lead frame, and has excellent cyclic bending characteristics and required thermal expansion characteristics. We provide alloy thin plates that combine plating, corrosion resistance, etc., and control the final structure and the amount of austenite by optimizing cold rolling, annealing conditions and final cold working and heat treatment of alloys of the above composition. It is an invention that can appropriately produce the alloy thin plate and has a great effect industrially.

[Brief description of drawings]

FIG. 1 Tensile strength, hardness, cyclic bending property of an Fe-Ni-Co alloy, α _30-400 ^. It is a chart showing the relationship between _C and the amount of austenite and the final cold rolling rate.

[Explanation of symbols]

In the above chart, solids are after low temperature heat treatment (500 ℃
× 10 min), open means low temperature heat treatment.

Claims (5)

[Claims] 1. Wt%, Ni: 27-30%, Co: 5-1
8%, Mn: 0.10 to 3.0%, Si: 0.10% or less, and the content of Ni, Co and Mn is less than Co: 10%, 63.5% ≦ 2Ni + Co + Mn ≦ 65. 0%, and when Co: 10% or more, the relationship of 69.5% ≦ 2Ni + Co + Mn ≦ 72.5% is satisfied, C: 0.020 to 0.070%, N: 0.010% or less, H:
1.0ppm or less, S: 0.0003% 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 Fe and inevitable impurities, and the austenite amount in the structure is 30 to 90%, and the grain size is
A high-strength Fe-Ni-Co alloy thin plate with excellent corrosion resistance and cyclic bending characteristics, characterized by having a grain size of No. 8 or more. 2. In addition to the components of claim 1, B, Nb, Ti, Z
One or two or more of r, Ta, V and W in total of 0.0
High strength Fe excellent in corrosion resistance and cyclic bending characteristics, characterized by containing 1 to 0.50% and having the structure of claim 1.
-Ni-Co alloy thin plate. 3. The average thermal expansion coefficient of 30 to 400 ° C. is (4
8) × 10 ⁻⁶ / ° C., hardness of 280 or more in Vickers hardness (H _V ), and tensile strength of 85 kgf / mm ² or more, corrosion resistance, repeatability according to claim 1 or 2. High-strength Fe-Ni-Co alloy sheet with excellent bending properties. 4. A thin plate is manufactured from a cold-rolled material of an alloy having the composition of claim 1 by the steps of primary cold rolling, primary annealing, secondary cold rolling, secondary annealing, tertiary cold rolling, and low temperature heat treatment. At that 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 ) is 700 to 740 ° C., third cold rolling rate (CR ₃ ) is 20 to 70%, low temperature heat treatment temperature (T ₃ ) is 400 to 540 ° C. low temperature heat treatment time (t). , 0.5 to 60 min. A method for producing a high-strength Fe-Ni-Co alloy sheet excellent in corrosion resistance and cyclic bending characteristics. 5. A cold-rolled material of an alloy having the composition of claim 2 is manufactured into a thin plate by the steps of primary cold rolling, primary annealing, secondary cold rolling, secondary annealing, tertiary cold rolling, and low temperature heat treatment. At that 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 ) is 700 to 740 ° C., third cold rolling rate (CR ₃ ) is 20 to 70%, low temperature heat treatment temperature (T ₃ ) is 400 to 540 ° C., low temperature heat treatment time (t) For 0.5 to 60 min. A method for producing a high-strength Fe-Ni-Co alloy sheet excellent in corrosion resistance and cyclic bending characteristics.