JPH07216510A - High strength lead frame material and its production - Google Patents

Abstract

PURPOSE:To provide high strength and superior solderability, plating suitability, corrosion resistance, etc., and to suppress anisotropy by specifying respective contents of Ni and Co and the relationship between them, forming a dual phase structure, and specifying average coefficient of thermal expansion. CONSTITUTION:This lead frame material has a composition consisting of, by weight, 0.5-22% Co, 22-32.5% Ni, and the balance Fe with inevitable impurities, where Ni is 27-32.5% when Co is <12% and 66%<=(2Ni+Co)<=74% is satisfied when Co is =12%. Further, cooling treatment or cooling treatment and cold working are applied to form a dual phase structure consisting of martensitic phase and austenitic phase, and the proportion of austenitic phase is regulated to =30%. Moreover, the average coefficient of thermal expansion from room temp. to 200 deg.C, hardness, and tensile strength in a length direction are regulated to (2 to 9)X10<-6>/ deg.C, =Hv240, and >=78kgf/mm<2> (765MPa), respectively, and also the difference between elongation in a length direction and elongation in a width direction at tensile test is regulated to <=3.0%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to high strength leadframe materials for semiconductor devices.

[0002]

2. Description of the Related Art In recent years, with the increase in capacity and integration of semiconductor devices such as logic devices and the reduction in thickness of packages, lead frames have tended to have more pins and thinner plates. For this reason, there is a demand for lead frame materials with higher strength than ever before. Fe-42Ni-based and Fe-29Ni-17Co-based (Kovar) have been conventionally known as these Fe-based leadframe materials for multiple pins, and many proposals have been made as described later.

[0003]

The multi-pin lead frame is mainly manufactured by a photo-etching method which enables fine processing. However, these finely processed Fe-42Ni-based or Fe-29Ni-17Co-based thin-plate multi-pin lead frames are prone to lead variations such as warpage and bending during package assembly, transportation, and mounting due to insufficient lead strength. Also, there are various problems such as buckling due to impact during use.

In order to improve the Fe-Ni-based or Fe-Ni-Co-based alloy, it is attempted to strengthen it by adding Si, Mn, and Cr ((a) JP-A-55-131155) or other strengthening elements. Proposal of high strength ((b) JP-A-3-39446,
(c) JP-A-3-39447), related to thermal expansion of Fe-Ni-Co alloys ((A) JP-A-55-128565, (B) JP-A-57-82455, (C)) JP-A-61-6251, (D) Japanese Patent Publication 1-817
No. 1, (e) Japanese Patent Publication No. 1-5562, (f) Japanese Patent Application Laid-Open No. 1-61042), and the two-phase structure strengthening previously proposed by the applicant ((A) Japanese Patent Application Laid-Open No. 3-166340, ( B) There is Japanese Patent Laid-Open No. 5-271876),
Since (a) to (c) contains a strengthening element in addition to the main element, there is a problem that surface oxidation easily occurs and the solderability and plating property, which are the main characteristics of the lead frame, are significantly deteriorated. None of the items (a) to (f) other than (a) are intended to positively improve the strength of the lead frame.

In the above (a), the strengthening mechanism has a high C
(About 0.2 to 0.35%) or further Hf, Nb, V, Zr, Ta,
One or more or two or more of W and Al are added.
Further, since the above (A) is focused on increasing the strength by the processing-induced martensite and the reverse transformation austenite precipitation, sufficient cold working is required to obtain high strength characteristics. Accordingly, there was a problem in terms of material anisotropy (difference between various characteristics in the rolling direction and the sheet width direction) and shape (material warpage, waviness due to strong rolling, etc.) that are harmful to the multi-pin and thin lead frame. . Further, (B) has higher strength and reduced anisotropy than (A), but since the main focus is on the martensitic transformation in the cooling process after the solution treatment or in the subsequent cold rolling, The composition of Ni is lower than that of A), and there is a problem that the corrosion resistance deteriorates and the coefficient of thermal expansion increases. The present invention provides a lead frame material that has high strength and good solderability, plating properties, corrosion resistance, and thermal expansion properties, suppresses anisotropy, or solves the problem of shape, and a manufacturing method thereof. The purpose is to

[0006]

Means for Solving the Problems The present inventor has found that Fe--Ni--C
Focusing on the phase transformation mechanism of the o-based alloy, various experiments were conducted on the composition and manufacturing conditions, and as a result, a solution treatment and a cooling treatment for actively cooling to a temperature lower than normal temperature or a cooling treatment in addition to the cooling treatment were performed. By performing hot working, (A)
It has been found that, in the Ni content region equivalent to, the cold working after the solution treatment can be eliminated or the cold working ratio can be reduced to make the structure at least two phases of the martensite phase and the austenite phase. Further, the material thus obtained has the characteristic of the proposal (A) that the strength can be increased without deteriorating the various characteristics of the lead frame, particularly the solderability and the plating property, and further, the cold working can be eliminated or reduced. It was also found by the present inventor that the processing rate can solve the above-mentioned problems of anisotropy and plate shape.

That is, the first invention of the present application is 0.5 to 22% by weight%, Ni 22 to 32.5% by weight, Ni 27 to 32.5%, Co 12% or more when the content of Ni and Co is less than 12%. Then
The relation of 66% ≦ (2Ni + Co) ≦ 74% is satisfied, and the balance is F
e and unavoidable impurities, and a structure in which the main structure is cooled to a temperature lower than normal temperature, or a structure in which at least two phases of a martensite phase and an austenite phase are formed by the cooling processing and cold working, and the austenite phase is 30 % Or more, the average coefficient of thermal expansion from room temperature to 200 ° C is (2 to 9) × 10-6 / ° C, the hardness is HV 240 or more, and the tensile strength in the length direction of the strip is 78 kgf / mm. ² (765 MPa) or more, a high-strength lead frame material characterized by less anisotropy with a difference in elongation in the length direction of the strip and the width direction of the strip in the tensile test of 3.0% or less. 2nd invention is Nb, Ti, Zr, Mo, V, W, in addition to the alloy composition described in the said 1st invention, respectively.
It is a high-strength leadframe material having the same structure and characteristic values as defined in the first aspect of the present invention, in which 0.1 to 3% in total of any one or more of Be is added.

The third and fourth inventions of the present application are based on the compositions of the first and second inventions, respectively.
i 0.5% or less, Mn 1.0% or less at least one kind is added,
It is a high-strength leadframe material having the same structure and specific value as defined in the first invention and the like. In each material of the present invention, C is 0.020% or less of inevitable impurities,
Desirably, S is 0.015% or less, O is 150 ppm or less, and N is 100 ppm or less.

Further, a fifth invention (claim 6) of the present application is a solution treatment of heating the alloy material of each composition described in the first to fourth inventions to a temperature above an austenitizing end temperature, After the solution treatment, if necessary, at least three treatments of a cooling treatment for positively cooling to a temperature lower than room temperature, which is performed by combining cold rolling and the like, and a heating treatment performed after the cooling treatment are performed, and the main structure is a martensite phase. And a structure comprising at least two phases of austenite phase of 30% or more and 30% or more.

[0010]

The alloy composition of each material of the present invention is the same as that proposed in the above-mentioned JP-A-3-166340 (A) and Ni-C.
o Overlap on the figure. The material of this proposal (A) is transformed into austenite phase by solution treatment, and then, this austenite phase is transformed into a work-induced martensite phase by cold working, and this martensite phase is annealed to a reverse transformation austenite phase to obtain a high content. It is strengthened. And, in order to obtain a sufficient strength improvement effect, a high cold working rate of 40 to 90%, etc. is required. There is a problem of the above, and it is effective to evaluate the anisotropy by using the difference in elongation in the tensile test by the test piece taken in the length direction, the longitudinal direction of the strip and the strip width direction. Confirmed by the inventor.

Therefore, as a result of various tests, the present inventor was indispensable in the above proposal by performing at least two treatments including a solution treatment and a cooling treatment such as a subzero treatment for cooling to a temperature lower than room temperature. Eliminates cold working or reduces its working rate, which eliminates material anisotropy,
It has also been found that the strength can be increased while remarkably decreasing, or solving the problems in the plate shape.

A strip material having a high geometrical accuracy and a high surface quality is brought to a finishing stage through a large number of cold rolling steps with a large amount of work, so that at this stage, a high plastic strain and a strong anisotropy are obtained. have. Therefore, in the manufacturing method invention of the present application, first, the strain and anisotropy are removed by solution heat treatment, the structure is austenitized, and then a process of cooling to a temperature lower than normal temperature such as sub-zero treatment is performed alone or by cold rolling. It is applied in combination with and finely precipitates the martensite phase in the austenite phase to strengthen it. In order to secure the shape accuracy of the plate material, it is preferable to correct it by applying tension while heating and to stabilize the material. Therefore, in the present invention, the final step is preferably a heat treatment (note that after this treatment, cold rolling may be added to an extent that does not impair the shape accuracy of the plate material).

The martensite phase in the material of the present invention includes not only the martensite phase associated with the cooling treatment, but also the martensite phase induced by the cold working which is added before or after the cooling treatment or both of them, if necessary. Good. That is, in the present invention, cold working for obtaining martensite is not essential, and the amount of martensite phase for obtaining a predetermined precipitation strengthening may be reduced by cold working by the effect of the cooling treatment, Therefore, the cold working amount can be set to 0 or reduced to prevent or suppress the increase in anisotropy and the defect in the plate shape.

Further, the austenite phase in the material of the present invention is not limited to the one remaining after the cooling treatment or cold working, but may also be the heating that is optionally performed in the above martensite after the cooling treatment or cold working. The reverse transformed austenite phase precipitated by the treatment may be included, or only the reverse transformed austenite may be included. In the invention of the manufacturing method of the present application (claim 6), the heat treatment step is an essential step from the viewpoint of lowering the coefficient of thermal expansion and lowering internal stress. That is, the austenite phase in the material of the present invention is due to either one or both of solution treatment and reverse transformation. Further, the martensite phase in the material of the present invention is essentially required to be the one by the cooling treatment, and may include only or in addition to this, the one induced by the processing.

The alloys according to the first and third inventions of the present application are
It was found that when the above heat treatment is performed, the inverse transformation from the martensite phase to the austenite phase during the heat treatment is temperature-sensitive, so that the annealing temperature has a large dependency on strength, and there are some problems in stable production. . Therefore, the present inventor
By the addition of a small amount of the specific element, to suppress the reverse transformation from the martensite phase to the austenite phase until heat treatment, further utilizing the solid solution hardening or precipitation strengthening by these elements to increase the heat treatment temperature dependence of the strength. While relaxing
The inventors have made the second and fourth inventions by discovering that the strength can be increased without impairing the solderability, plating property, thermal expansion property, and corrosion resistance.

Further, the material of the present invention is characterized in that its structure is controlled or further strengthened by solid solution strengthening or precipitation strengthening with a specific element. However, the material of the present invention also has solderability and plating property. In the process of evaluation, if the residual Mn, Si added as a deoxidizer and impurities of carbon, sulfur, oxygen, and nitrogen are regulated to below a specific value, the solderability and plating property will be further improved.
It was found that the required practical properties other than strength and thermal expansion properties were improved.

Next, the reasons for limiting the numerical values of the present invention will be described. Co
The content is optimal for minimizing the coefficient of thermal expansion at around 17% and around 5%, and is less than 0.5% or 22%.
If it exceeds, the coefficient of thermal expansion becomes large and the thermal expansion matching with the silicon chip is deteriorated. Therefore, the Co content is limited to the range of 0.5% to 22%. The Ni content is determined in relation to the Co content. If less than 12% Co and less than 27% Ni, or more than 12% Co and less than 66% (2Ni + Co), the austenite becomes too unstable, the austenite amount becomes insufficient, and precipitation occurs even when annealing is added as the final step. The reverse transformation austenite undergoes martensitic transformation in the cooling process and the coefficient of thermal expansion increases.

When the content of Co is less than 12% and the content of Ni exceeds 32.5%, or when the content of Co is 12% or more and (2Ni + Co) exceeds 74%, the martensite transformation is unsatisfactory even in the cooling treatment combined with solution treatment and cold working. Will be enough. Therefore, due to the increase in the amount of cold work required for sufficient strengthening, strong anisotropy,
In addition, the plate shape also makes it unsuitable for ordinary applications. Therefore, if less than 12% Co, Ni27-32.5%, Co12%
In the above, Ni is limited so as to satisfy the relation of 66% ≦ (2Ni + Co) ≦ 74%. The most desirable component ranges of Co and Ni are Ni 28.0 to 30.0% and Co 6.0 to 7.0%. This range is consistent in corrosion resistance, strength, coefficient of thermal expansion and cost with conventional leadframe materials.

It is desirable that Mn is not contained, and even if it is used as a deoxidizer, if it exceeds 2.0%, the thermal expansion coefficient increases, and the solderability and plating property deteriorate.
Limited to 0% or less. It is desirable that Si does not remain in the material. Even when it is used as a deoxidizer, if it exceeds 0.5%, the coefficient of thermal expansion rises and the solderability and plating property deteriorate, so it was limited to 0.5% or less. When Si and Mn are used as a deoxidizing agent, one or two kinds are used within the above range.

Nb, Ti, Zr, Mo, V, W, and Be strengthen the matrix by solid solution strengthening or precipitation strengthening of the material of the present invention, and also from the martensite phase to the austenite phase during the above-mentioned heat treatment. It is important as an element that relaxes the temperature dependence of reverse transformation. The material of the present invention is strengthened by forming a structure consisting of at least two phases of austenite and martensite, but it is desirable that the amount of austenite is large from the viewpoint of thermal expansion characteristics, and when heat treatment is performed, the temperature is as high as possible. It is desirable to take. However, when these additive elements are not added and the heat treatment is performed, the mechanical characteristics rapidly decrease as the temperature rises. For this reason,
From the viewpoint of production stability, it is desirable to stabilize the mechanical properties on the high temperature heat treatment side by adding these elements. Further, addition of these elements is effective because it has the effect of solid solution strengthening and precipitation strengthening even when heat treatment is not performed.

By adding these solid solution strengthening elements or precipitation strengthening elements, it is possible to prevent the hardness on the high temperature side, that is, the deterioration of mechanical properties, especially when heat treatment is performed. If the added amount of these elements is less than 0.1%, there is no effect in improving the mechanical properties, and if it exceeds 3%, surface oxidation is promoted, solderability,
Plateability is significantly impaired. Further, since these elements act on the austenite generation side, if the addition amount increases, the austenite of the substrate becomes too stable, so the addition amount is 0.1 to 3%.
Limited to A desirable amount of addition is 0.2 to 2.5%.

Next, the impurity element will be described. If C, which is an impurity, exceeds 0.020%, the etching property of the material is significantly deteriorated, and further, excessive precipitation of carbide deteriorates the solderability and plating property. Therefore, it is preferable to limit the content to 0.020% or less. Is 0.010% or less. S
Is more than 0.015%, excessive MnS is formed, surface defects are likely to occur, and solid solution S deteriorates hot workability, so it is preferable to limit it to 0.015% or less. The desirable range of S is 0.008% or less.

When O exceeds 150 ppm, it forms an excess oxide with an element having a strong affinity with O, such as Si as a deoxidizer and Al, Mg mixed inevitably, which deteriorates the surface cleanliness. The amount is preferably 150 ppm or less in order to reduce the solderability and the plating property, and the desirable range of O is 80 ppm or less. Since N has an austenite stabilizing effect, 10
If the content exceeds 0 ppm, the austenite phase is excessively stabilized and transformation to martensite is less likely to occur. Further, since nitride is excessively deposited and solderability and plating property are deteriorated, the content is preferably 100 ppm or less, and the preferable amount of N is 50 ppm or less.

The final main structure is a structure consisting of at least two phases consisting of a martensite phase and an austenite phase (which may partially contain retained austenite). However, if the austenite phase is 30% or less, sufficient strengthening is achieved. The austenite phase is limited to 30% or more because it is not obtained and the coefficient of thermal expansion becomes large and the compatibility with the silicon chip becomes poor. The desirable range of the amount of austenite is 60% or more. The amount of austenite phase in the present invention
(%) Is a value obtained from the X-ray diffraction intensity described in Examples below. In the invention of each material of the present application, mechanical characteristics and coefficient of thermal expansion were specified. The hardness and tensile strength of the material of the present invention are 42 alloys (200HV, tensile strength 64kgf / m
m ² (about 628 MPa)), the hardness HV is 240 or more, and the tensile strength (stripe length direction) is 78 kgf / mm ² (765 MPa) or more. Desirable hardness and tensile strength are HV250 or higher and 81 kgf / mm ² (794
MPa) or higher.

Further, the coefficient of thermal expansion is limited to α _30-200 = (2-9) × 10 ₋₆ powers / ° C. from the viewpoint of compatibility with Si chips. A desirable coefficient of thermal expansion is _α30-200 = (4.5 to 7.5) × 10 -6 powers / ° C. When the anisotropy becomes large, a problem arises in a QFP type package having leads in four directions because the bending shapes of the leads in the longitudinal direction and the width direction are different. Therefore, in the present invention, as a method of measuring anisotropy, the difference in elongation in the tensile test when the length direction of the test piece is the longitudinal direction and the width direction of the plate material is used. If the difference in elongation exceeds 3.0%, the problem due to the difference in the above-mentioned bending shape becomes remarkable. For this reason, 3.0% or less is specified. It is preferably 2.0% or less.

Next, a method for producing the material of the present invention will be described. At the final stage of manufacturing leadframe material,
First, it has already been described that the solution treatment to remove the strain and anisotropy which had been received before, and to austenite the solution. When the solution treatment temperature is lower than the austenitization end temperature, the cooling process to the room temperature thereafter and the cooling process to a temperature lower than the room temperature for accelerating the martensitic transformation thereafter, or further before or after this cooling process are inserted as necessary. Since the martensitic transformation does not sufficiently occur in cold rolling or the like, the solution treatment temperature is set to the austenitization end temperature or higher. The austenitizing finish temperature is about 650 ° C, although it varies depending on the component system. However, in order to sufficiently eliminate the anisotropy, it is desirable that this treatment be performed at a recrystallization temperature of about 800 ° C. or higher.

The cooling treatment after the solution treatment is the most important treatment in the present invention. By this treatment, the cold working is eliminated or the low working ratio is suppressed to suppress the increase of anisotropy and a large phase transformation is caused. A predetermined strength-enhancing effect can be obtained by the generation. From the viewpoint of accelerating martensitic transformation, this cooling treatment is preferably performed at 0 ° C. or lower, and more preferably at −40 ° C. or lower. In addition, before or after the cooling treatment after the solution treatment, the working ratio of the cold working added as necessary before or after both, the material anisotropy in the rolling direction and the strip width direction becomes strong when it exceeds 80%, and It is not preferable because the shape tends to be warped, waviness, etc., and the cold working rate is preferably limited to 80% or less. Desirably 60% or less, more desirably 50%
By controlling the amount to the following, lower anisotropy and a good material shape can be obtained. In the present invention, since the cooling treatment is indispensable, cold working is unnecessary, or the working rate can be reduced, which is advantageous in terms of anisotropy and plate shape. Further, this cold working also has an effect of transforming the austenite phase remaining in the cooling treatment into work-induced martensite.

In this way, high strength is achieved by precipitation of the martensite phase in the cooling process after the solution treatment or in the subsequent cooling process or cold working. When heat treatment is applied, the amount of martensite phase before the treatment is
If it is 10% or less, sufficient reverse transformation austenite precipitation strengthening cannot be obtained by this heat treatment, so the amount of martensite before this treatment is preferably 10% or more. In order to obtain more stable precipitation strengthening, it is preferable to set it to 50% or more. on the other hand,
The above heat treatment temperature is not more than the austenitization end temperature because all the martensite phases are transformed into the austenite phase when the austenite end temperature is exceeded and the martensite phase disappears, and desired precipitation strengthening cannot be obtained. It is necessary.

[0029]

EXAMPLES The material of the present invention will be described with reference to examples. Alloys having the compositions shown in Table 1 were melted and cast in a vacuum melting furnace,
Forged at 50 ℃ and hot rolled to a thickness of 3mm, then 1000 ℃
After the solution heat treatment of × 1Hr, cold rolling was performed to a thickness of 0.5 mm (compression ratio: 83%). Of the sample Nos. In the table, A to P are alloy materials according to the present invention, V to Z are comparative alloy materials, of which V contains excessive strengthening elements, and W and X are Ni of the present invention. Higher than specified, Y and Z have lower Ni than specified in the present invention. For each of the above materials (0.5 mm thickness), cold rolling up to 0.25 mm, solution treatment at 800 ° C, cooling treatment at -70 ° C, 0.12
A series of treatments (manufacturing method 1) of cold rolling (50%) to 5 mm and heat treatment at 560 to 600 ° C. were performed. Table 2 shows the structure ratio in the manufacturing process and various characteristics after the heat treatment (measurement conditions and the like are shown in the table).

Table 3 shows that among the alloy materials, A, L, and
For H material (0.5mm thickness), solution treatment at 800 ℃, 0.1
Cold rolling up to 25 mm (75%), followed by a series of heat treatments at 560 to 600 ° C (manufacturing method 2), structural ratios at each stage, and various characteristics after heat treatment (measurement conditions, etc.) Indicates the table). In addition, Table 4 shows that for the cold-rolled material of the composition A having the plate thickness of 0.25 mm in the above process, the solution treatment at 800 ° C, the cooling treatment at 0 ° C, and the cold rolling at 50% (t = 0.125). mm) and 5
Heat treated at 60 ℃ (Production method 3), 8
Solid solution treatment at 00 ℃, cold rolling at 50% (t = 0.125mm), -70 ℃
Which has been subjected to cooling treatment at 560 ° C. and heat treatment at 560 ° C. (manufacturing method 4), and solid solution treatment at 800 ° C., -70
The amounts of austenite in the final state and the respective main characteristics are shown for those subjected to the cooling treatment at ℃ and the heat treatment at 560 ° C (manufacturing method 5 t = 0.25 mm).

The tissue ratio is a value obtained by the following formula. However, when ferrite is included, it is included in Iα. Austenite phase (%) = {Iγ / (Iα + Iγ)} × 100 Iα = Iα (110) + Iα (200) + Iα (211) Iα (110) is the X-ray diffraction intensity of martensite Iγ = Iγ (111) + Iγ ( 200) + Iγ (220) + Iγ (311) Iγ (111) and the like are X-ray diffraction intensities of austenite. Also, the anisotropy is indicated by the difference between the elongation in the length direction and the elongation in the width direction of the strip by the tensile test. The measurement of elongation at this time
Crosshead speed of 0.5 mm / m for 0.125t × 25w × 100L (parallel part: 5w × 25L) tensile test piece in Instron type universal test
Tensile test was conducted with in, and an extensometer attached to the parallel part of the test piece was used.

[0032]

[Table 1]

[0033]

[Table 2]

As can be seen from Table 2, the materials A1 to P1 of the present invention and the comparative materials V1, Y1, and Z1 have a mixed structure of austenite phase and martensite phase of 30% or more, as can be seen from the structure ratio III after heat treatment. Therefore, it can be seen that, compared with the comparative materials W1 and X1 in which the austenite became too stable in terms of composition and became 100%, it exhibited higher strength characteristics. Furthermore, the present invention material A1
P1 to P1 are superior in corrosion resistance to the comparative materials Y1 and Z1 in which the austenite is too unstable due to their composition, and also have a low coefficient of thermal expansion. In addition, 1 of Nb, Ti, Zr, Mo, V, W, Be
Material of the present invention G1 to N1 and P1 added with one or more kinds
Has a higher strength than those of A1 to F1 and O1 in which these are not added. That is, of these, G for A1, O1
L1-N1 for 1-K1, P1 and E1 are Ni and
Corresponding to the content of Co, the latter has high hardness and high tensile strength. However, since the comparative material V1 contains an excessive amount of the strengthening element, the plating property is poor with "swelling".

Further, O1 and P1 which do not contain Si and Mn have substantially the same characteristics as the corresponding A1 and M1.
In addition, each material in Table 2 has a cold working ratio after the final solution treatment.
Since it is as small as 50%, the anisotropy is as small as 2.5% or less due to the difference in elongation, and the plating property and corrosion resistance are the same. From Table 3, the materials A2, L2, and H2 according to the conventional manufacturing method (manufacturing method 2) have a strong rolling rate (75%) without the cooling treatment according to the present invention. The anisotropy is larger than that of A1, L1 and H1 in Table 2, and the amount of martensite phase after cold rolling is small (the amount of austenite is large). , It is inferior to H1.

[0036]

[Table 3]

[0037]

[Table 4]

A3, A4 and A5 in Table 4 are obtained by increasing the temperature of the cooling treatment to 0 ° C. with respect to the above-mentioned A1 in the manufacturing process, and performing 50% cold rolling before the cooling treatment. And those with cold rolling omitted. They are,
Characteristically, there is no difference in plating property and corrosion resistance compared to A1,
The coefficient of thermal expansion and anisotropy are equal or superior, and are slightly inferior in strength, but they are significantly better in anisotropy and superior in strength than A2 produced by the conventional manufacturing method. Next, FIGS. 1 (a), (b), and (c) show the results of the above-mentioned manufacturing method 1 for A in Table 1.
3 is photographs (magnification: 400 times) showing the structures after solid solution treatment (0.25 t) at 800 ° C., cooling treatment at −70 ° C. and heat treatment (final treatment), respectively. Further, FIG. (D) is a photograph (magnification: 400 times) showing the structure after heat treatment (final treatment) in Production Method 2 for A in Table 1.

That is, FIG. 1 (a) shows that by the solution treatment,
You can see that it is 100% austenite. The black dots are non-metallic inclusions. Figure 1 (b)
Is the above-mentioned (a) that has been subjected to a cooling treatment at -70 ° C. Even if no cold working is performed by this treatment, the structure ratio is as shown in I of A1 of Table 2, austenite (white part )
Is 45%, while martensite is 55% (black part)
Has occurred.

FIG. 1 (c) shows the above (b) with 50% cold rolling and 5%
As shown in Table 2, the heat treatment at 60 ℃, the austenite content is 88% due to the appearance of reverse transformed austenite after the heat treatment after the reduction of austenite to 32% by cold rolling. Therefore, the strength and structure of the structure are stabilized. Fig. 1 (d) shows a test piece obtained by subjecting the material after solution treatment [almost the same structure as (a) and austenite 100%] to 75% cold rolling and 560 ° C heat treatment as shown in Table 3. Since the amount of austenite was only cold-rolled, it decreased to only 78% and then increased to 92% by heat treatment, and it can be imagined from the photograph that the anisotropy is considerably large. .

[0041]

As described above, the material of the present invention occupies the same Fe-Ni-Co alloy composition as in Japanese Patent Application Laid-Open No. 3-166340 (A) by the present inventors. Has good solderability, plating properties, corrosion resistance, and low thermal expansion,
By introducing a cooling treatment during the manufacturing process, the cold working after the solution treatment is eliminated, or a low cold working rate is possible, and in particular, a high-strength lead frame material with a lower anisotropy is obtained. And is suitable for a lead frame such as QFP. The materials of the second and fourth inventions are
One or two of Nb, Ti, Zr, Mo, V, W, Be
By adding more than one species, more stable low thermal expansion and high strength characteristics can be obtained.

[Brief description of drawings]

1 is a photograph showing a metal microstructure of a material in each step of Example 1 of the present invention and a conventional manufacturing method. (a), (b)
And (c) are the structures of A in Table 1 after the solution treatment at 800 ° C. (0.25 t), the cooling treatment at −70 ° C., and the heat treatment (final treatment) in the above production method 1. Showing pictures
(Magnification 400 times). Also, Figure (d) is for A in Table 1,
Heat treatment (final treatment) in the manufacturing method 2 (conventional method)
It is a photograph (magnification 400 times) showing the later structure.

Claims (7)

[Claims] 1. Co 0.5 to 22% and Ni 22 to 3 in% by weight.
2.5%, the content of Ni and Co is less than Co 12% Ni 27
〜32.5%, Co 12% or more 66% ≦ (2Ni + Co) ≦ 74
%, The balance consists of Fe and unavoidable impurities, and a cooling treatment for cooling the main structure to a temperature lower than normal temperature or at least two phases of a martensite phase and an austenite phase by the cooling treatment and cold working. , The austenite phase is 30% or more, the average thermal expansion coefficient from room temperature to 200 ℃ (2 ~ 9) × 10 minus 6
/ ° C, hardness is HV 240 or more, strip length tensile strength is 78 kgf / mm ² (765 MPa) or more, and the difference in elongation between the strip length direction and the strip width direction in the tensile test is High strength leadframe material characterized by less than 3.0% anisotropy. 2. Co 0.5 to 22%, Ni 22 to 3 in% by weight.
2.5%, Nb, Ti, Zr, Mo, V, W, Be of one or more kinds in total of 0.1 to 3%, Ni and Co contents of Co 27% to Ni 27 to 32.5% , Co 12% or more, the relationship of 66% ≦ (2Ni + Co) ≦ 74% is satisfied, the balance consists of Fe and unavoidable impurities, and the main structure is cooled to a temperature lower than room temperature or a cooling process with the cooling process. It is a structure composed of at least two phases of a martensite phase and an austenite phase by hot working, the austenite phase is 30% or more, and the average thermal expansion coefficient from room temperature to 200 ° C. is (2 to 9) × 10 −6 power / ℃, hardness HV 240 or more, strip length tensile strength 78kgf / mm ² (765M
Pa) or more, and the difference in elongation between the length direction of the strip and the width direction of the strip in a tensile test is 3.0% or less, and the high-strength leadframe material is characterized by little anisotropy. 3. At least one of Si 0.5% or less and Mn 2.0% or less by weight% is included, and Co 0.5 to 22%, Ni 22 to
32.5%, the content of Ni and Co is less than Co 12% Ni 27
〜32.5%, Co 12% or more 66% ≦ (2Ni + Co) ≦ 74
%, The balance consists of Fe and unavoidable impurities, and a cooling treatment for cooling the main structure to a temperature lower than normal temperature or at least two phases of a martensite phase and an austenite phase by the cooling treatment and cold working. , The austenite phase is 30% or more, the average thermal expansion coefficient from room temperature to 200 ℃ (2 ~ 9) × 10 minus 6
/ ° C, hardness is HV 240 or more, strip length tensile strength is 78 kgf / mm ² (765 MPa) or more, and the difference in elongation between the strip length direction and the strip width direction in the tensile test is High strength leadframe material characterized by less than 3.0% anisotropy. 4. A 0.5% to 22% Co, 22 to 3% Ni, containing at least one of Si 0.5% or less and Mn 2.0% or less by weight.
2.5%, Nb, Ti, Zr, Mo, V, W, Be, or any one or more of them in total of 0.1 to 3%, and when the content of Ni and Co is less than Co 12%, Ni 27 to 32.5%, When Co is 12% or more, the relation of 66% ≦ (2Ni + Co) ≦ 74% is satisfied, the balance consists of Fe and unavoidable impurities, and the main structure is cooled to a temperature lower than room temperature or the cooling process and cold treatment. A structure consisting of at least two phases of a martensite phase and an austenite phase by processing, the austenite phase is 30% or more, and the average coefficient of thermal expansion from room temperature to 200 ° C is (2 to 9) × 10 −6 powers / ° C. , Hardness of 240 or more at HV, tensile strength in the length direction of the strip is 78 kgf / mm ² (765M
Pa) or more and a difference in elongation between the length direction of the strip and the width direction of the strip in a tensile test is 3.0% or less, and a high-strength leadframe material characterized by little anisotropy. 5. Ni 28.0 to 30.0% and Co 6.0 to% by weight.
It is 7.0%, The manufacturing method of the high strength lead frame material in any one of Claims 1-4. 6. A solution treatment for heating the alloy having the composition according to any one of claims 1 to 5 to a temperature above an austenitizing end temperature, and a cooling treatment for cooling the solution to a temperature lower than room temperature after the solution treatment. And at least three heat treatments to be performed after the cooling treatment to produce a high-strength leadframe material characterized in that the main structure is a structure consisting of at least two phases of a martensite phase and an austenite phase of 30% or more. Method. 7. The method for producing a high-strength leadframe material according to claim 6, wherein cold working is performed at least before or after the cooling treatment.