JPH0941095A - Iron-nickel alloy sheet for electronic parts and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Fe-Ni alloy sheet for electronic parts, such as lead frame, increased in strength without deteriorating the characteristics of the conventional materials. SOLUTION: This sheet is an Fe-Ni alloy sheet for electronic parts, which has a composition consisting of, by weight, 28-55% Ni and the balance essentially Fe or further containing <=12% Co and has a structure having the crystalline grains elongated by rolling in a secondary work hardening region and also has a hardness, by Vickers hardness, satisfying Hv>=220+0.5[Ni](%)+0.7[Co](%). This sheet can be obtained by performing final cold rolling at a rolling rate corresponding to the secondary work hardening region where hardness increases abruptly with the increase of rolling rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an Fe-Ni alloy suitable for use as a material for electronic parts such as lead frames.

[0002]

2. Description of the Related Art Fe-Ni alloys, which have low thermal expansion characteristics and excellent workability and corrosion resistance, are widely used as materials for electronic parts. For example, as a material for a lead frame of an integrated circuit device, Fe-42Ni, Fe-50Ni,
Fe-Ni such as Fe-29Ni-17Co (Kovar)
A series alloy is used. Fe-36Ni (Invar), Fe-
31Ni-5Co (Super Invar) and the like are known.

When the Fe-Ni-based material as described above is applied to electronic parts, the material is subjected to fine processing such as press punching or photoetching. In electronic component materials such as lead frames, further thinning and microfabrication have been required due to high integration of semiconductor devices.
Fe-Ni-based electronic component materials that have undergone microfabrication with such a thin plate are prone to warping and bending during assembly, transportation, mounting, etc. due to insufficient strength, and they also buckle due to shock during use. There are various problems. Therefore Fe-N
There is a strong demand for improvement in strength of i-based electronic component materials.

[0004]

In response to such requirements, many proposals have been made for improving the strength of Fe-Ni alloys. For example, as a method for increasing the strength by adding an alloying element, there is an attempt to strengthen by adding Si, Mn, and Cr (JP-A-55-131155). However, since it contains a strengthening element that is easily oxidized, in addition to the main element, surface oxidation is likely to occur and the solderability and plating property tend to be slightly deteriorated. In addition, there is a proposal (Japanese Patent Laid-Open No. 2-159348) to increase the strength by adding a small amount of Be, which has a remarkable effect of solid solution strengthening. However, since Be is extremely expensive as compared with other strengthening elements, the cost increases even with a small amount. In addition, the soldering property and the plating property are slightly deteriorated due to the surface oxidation.

Fe-Ni-, which was previously proposed by the applicant of the present invention, uses a strengthening mechanism other than the addition of alloying elements.
By strengthening the two-phase structure of Co (Japanese Patent Laid-Open No. 3-16634)
0). However, controlling the two-phase structure requires advanced manufacturing technology. Further, it is proposed to control the crystal grains by annealing before the final cold rolling and to enhance the strength by performing the final cold rolling at a predetermined working ratio (JP-A-59-33857 and JP-A-4-1601).
12). Since this method uses work hardening, it has the advantage that it does not require additional elements and is easy to manufacture. However, even these methods cannot be said to sufficiently satisfy the above-mentioned further strengthening.

In view of the above points, the present invention provides a manufacturing method for obtaining a sufficiently high strength in a Fe-Ni-based electronic component material without impairing the solderability and the plating property and significantly increasing the cost. The purpose is to provide.

[0007]

Means for Solving the Problems The present inventor has proposed Fe-Ni
A detailed investigation was conducted on the influence of the alloys on the strength of the rolling process. Then, when the rolling rate is increased under specific conditions, the hardness rapidly increases after the primary work hardening, and it is found that there is a secondary work hardening region in which the strength is increased,
By applying the rolling rate in this region, without impairing the solderability and plating property, and without significantly increasing the cost,
Furthermore, they have found that the anisotropy of strength can be reduced, and have reached the present invention.

That is, according to the method for producing the material of the present invention, Ni of 28 to 55% or Co of 12% by weight is used.
% Or less, and the balance being substantially Fe after hot rolling or after at least one cold rolling and annealing after hot rolling, the alloy is rapidly hardened against the rolling ratio. Vickers hardness HV ≧ 220 + 0.5 [Ni] (%) + at the rolling rate corresponding to the secondary work hardening region in which
0.7 [Co] (%), [C when not containing Co
o] = 0, and the final cold rolling is performed so that

In the present invention, the term "final cold rolling" refers to cold rolling that is not followed by annealing at a recrystallization temperature or higher. Therefore, the strain relief annealing, which is the annealing at the recrystallization temperature or lower, can be performed after the final cold rolling of the present invention. Further, in the present invention, Vickers hardness HV ≧ 125 + before final cold rolling.
0.5 [Ni] (%) + 0.7 [Co] (%), when Co is not contained, [Co] = 0 is calculated, so that the above-mentioned secondary work hardening region can be easily adjusted. It can be achieved and becomes preferable.

The Fe-Ni alloy thin plate for electronic parts of the present invention obtained by the above-mentioned manufacturing method of the present invention is Ni28.
.About.55%, or further containing 12% or less of Co, and the balance being substantially Fe, the structure is a structure in which crystal grains are expanded by rolling, and the hardness is HV in Vickers hardness.
≧ 220 + 0.5 [Ni] (%) + 0.7 [Co]
(%) Is satisfied.

Further, the Fe-Ni alloy thin plate for electronic parts of the present invention is applied with the secondary work hardening region, and when heated in a hydrogen atmosphere at 900 ° C. for 15 minutes, the relative crystal planes by X-ray diffraction. It is preferable that the X-ray has a characteristic that the intensity of the (200) plane is 80% or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The greatest feature of the present invention is that the final cold rolling is performed in a secondary work hardening region in which work hardening is performed subsequent to primary work hardening, to enhance strength. In the present invention, by applying the rolling rate in this secondary work hardening region, the difference in strength between the rolling direction and the direction orthogonal to the rolling, which is caused by the strain imparted by cold working, which has been a conventional problem, that is, the strength difference. It is possible to reduce the directionality and dramatically increase the strength of the thin plate.
The strength anisotropy does not increase in the secondary work-hardening region used in the present invention because the dislocation density that is unevenly distributed due to the influence of the cold rolling direction at the rolling ratio of the secondary work-hardening region or less is the secondary workability. It is considered that both the rolling direction and the direction perpendicular to the rolling are saturated in the hardening region. Further, in this region, the hardness is sharply increased, and the material strength can be remarkably increased, and it is possible to obtain two unprecedented advantages of securing the strength and reducing the anisotropy.

A concrete example of the secondary work hardening region is shown in FIG. FIG. 1 shows the relationship between the cold rolling rate and the hardness of Fe-42Ni. In FIG. 1, the hardness before cold rolling is set to a high Vickers hardness of 152 in advance. As shown in FIG. 1, when the rolling rate is increased, it can be roughly divided into three regions. That is, in the low rolling ratio region, the hardness increases in proportion to the rolling ratio (region I). Then, when the rolling rate becomes high, the hardness becomes not so high even if the rolling rate is increased, and it becomes a blunt region (region II). Then, when the rolling rate is further increased, it becomes a secondary work hardening region where the hardness is remarkably increased (region III).

The present invention is applicable to the above-mentioned region III.
It is a secondary work hardening region corresponding to. The secondary work hardening region is the point at which the increase rate of hardness changes from decreasing to rising when a work hardening curve showing the relationship between rolling rate and hardness as shown in FIG. 1 is created, that is, the work hardening curve of the material. It can be specified as an inflection point or higher. However, Fig. 1 shows an example of the work hardening curve, and the material and the hardness of the material at the start of cold
The shape of the curve differs depending on (HV). Therefore, the final cold rolling rate at which the secondary work hardening starts is about 80% in FIG. 1, but the value is not constant and may change up and down. For example, the hardness before cold rolling is about Vickers 1
In the case of No. 74, the curve is as shown in FIG. 2A, and the final cold rolling rate at the start of secondary work hardening is 70%. When the hardness before cold rolling is 131 in Vickers hardness, a curve as shown in b of FIG. 2 is obtained, and the final cold rolling rate at the start of secondary work hardening is 83%. Desirably, a rolling rate of 5% or more higher than the inflection point is used. When the material rolled in the secondary work hardening region is heated and recrystallized, the relative X of the (200) plane is
A material having a linear strength of 80% or more and a material having a desired rolling rate is 90% or more, which is extremely high.

The strength anisotropy still left in the material by such rolling in the region III can be further improved by performing stress relief annealing under an appropriate condition of not higher than the recrystallization temperature without significantly lowering the strength. Can be reduced.

Further, it is desirable that the hardness is as high as possible before the final cold rolling. The present inventor has further found that the higher the hardness before the final cold rolling is, the lower the rolling rate falls into the secondary work hardening region. That is, higher strength can be obtained.

Then, according to the above-mentioned method, the hardness is a Vickers hardness of HV ≧ 220 + 0.5 [Ni] (%) + 0.
7 [Co] (%), [Co] = when Co is not contained
Fe- with an unprecedentedly high hardness, calculated as 0
A Ni-based alloy thin plate can be obtained. [N in the present invention
i] (%) and [Co] (%) represent the weight percentage values of Ni and Co, respectively. In the present invention, the hardness is defined because the hardness is almost proportional to the strength, and the material can be identified most accurately. The coefficients of Ni and Co in the above-mentioned relational expression representing hardness were determined to be 0.5 and 0.7 from the hardness obtained when each element was added.

Next, the reasons for limiting the composition of the present invention will be described. N
The i content adjusts the coefficient of thermal expansion of an electronic component manufactured by using the material, and minimizes the coefficient of thermal expansion in the vicinity of 36% thereof. Ni is less than 28% or 55%
When it is more, the thermal expansion becomes too large, and the merit of low thermal expansion, which is one of the features of the Fe-Ni alloy, is lost. However, in terms of thermal expansion characteristics, Ni can be partially replaced by Co. Therefore, the Ni content is limited to 28 to 55%.

As described above, Co can be replaced with Ni in terms of thermal expansion. Co is solderability like other elements,
It does not impair the plating property, has the effect of increasing the hardness during annealing by forming a solid solution in the Fe-Ni alloy, and thereby also increasing the hardness after the final cold rolling. That is, by adding Co, the effect of performing the final cold rolling at the rolling ratio in the secondary hardening region becomes more remarkable. But 12
No further effect is seen with the addition of more than%. For this reason C
The o content is limited to 12% or less.

The following elements are preferably specified as elements contained in the Fe-Ni alloy thin plate as impurities or additives. When C exceeds 0.02%, the etching property of the material is remarkably deteriorated, and the excessive precipitation of carbide deteriorates the solderability and plating property.
It is desirable to be 2% or less. Mn is added for the purpose of improving the deoxidizing agent and workability, but if it exceeds 1.0%, the coefficient of thermal expansion increases and the solderability and plating property deteriorate, so 1.0% or less is desirable. Si is added as a deoxidizer, and it is desirable that Si does not remain in the material.
%, An extreme increase in the coefficient of thermal expansion and an extreme deterioration in solderability and plating properties do not occur, so that it is acceptable. Further, elements such as Cr, Cu, Ti, and V may be added for the purpose of improving corrosion resistance, strength, or adhesion characteristics of the oxide film. However, since these elements are elements that deteriorate etching properties, plating properties, solderability, etc., even if added, it is desirable that the total amount be 10% or less.

The material of the present invention can be specified not only by the extremely high hardness described above, but also by the recrystallization texture when the material is heat-treated for recrystallization. When used as an actual electronic component material, such recrystallization heat treatment is not performed, but it is effective in determining whether the material is the material of the present invention. That is, in the material rolled in the secondary work hardening region, when the material is subjected to recrystallization heat treatment, the (200) plane has a recrystallized texture in which the (200) plane is extremely strongly aggregated. Since the degree of aggregation of the (200) plane is different when the recrystallization heat treatment conditions are different, in the present invention, the relative X-ray intensity of the crystal plane by X-ray diffraction when heated at 900 ° C. for 15 minutes. The strength of the (200) plane was defined as 80% or more. It is preferably 90% or more. In the present invention, the relative X-ray intensity means (111) by X-ray diffraction,
The diffracted X-ray intensity of each of the (200), (220), and (311) planes is obtained and is defined by the ratio of each plane to the total sum.

[0022]

The present invention will be described below with reference to examples. Fe
Fe-42Ni alloy shown in Table 1 as a Ni-based alloy, F
e-36Ni alloy, Fe-50Ni alloy, Fe-31N
i-5Co alloy, Fe-34Ni-10Co alloy, Fe
Melting -38Ni-5Co alloy in a vacuum high frequency induction furnace,
After casting, forging and hot rolling were performed to a thickness of 3 mm, and the scale was removed on the surface to a thickness of 2.5 mm.

[0023]

[Table 1]

When the final cold rolling is directly applied after the hot rolling without passing through the intermediate step to obtain the Fe-Ni alloy thin plate, the final cold rolling is applied to this 2.5 mm material at the rolling rate shown in Table 2. Hot rolled. The samples 1, 15 and 31 of the present invention and the sample 19 of the comparative example correspond to this. In addition, after hot rolling, cold rolling is performed, followed by annealing and then final rolling.
In order to obtain a Ni-based alloy thin plate, the material obtained by this hot rolling is subjected to cold rolling to a thickness of 1.5 mm or less, and then subjected to intermediate annealing so as to have the hardness shown in the table. After that, final cold rolling was performed at a rolling rate as shown in Table 2.

[0025]

[Table 2]

Table 2 shows the rolling ratio of the final cold rolling described above,
In addition to the final cold rolling region evaluated in the same manner as in FIG. 1, the Vickers hardness before final cold rolling, the final Vickers hardness, solderability, plating property, and tensile strength obtained by final cold rolling, Anisotropy was measured. As described above, the sample of the present invention is in the secondary work hardening region (region III).

Solderability is 235 ° C. after flux treatment
It was immersed in a solder bath for 5 seconds, and a solder wetted area of 100% was evaluated as ◯. Plating is performed after degreasing and oxidation treatment, 0.5-μm-thick Ni strike plating, and 3 μm-thick Ag on top of it, then heating in air at 450 ° C. for 3 minutes, swelling and 90-degree plating Bent and not peeled off was evaluated by ○. Mechanical properties are JISZ2241
It was measured by the metal material tension method shown in. The test pieces are JISZ220 in the rolling direction and the direction perpendicular to the rolling direction from each sample.
No. 13B test piece shown in No. 1 was sampled, and 0.2% proof stress was strain increase rate 1% / mi using a Tensilon tester.
The tensile strength was determined by n, the tensile strength was determined by the offset method, and then the tensile strength was determined at a strain increase rate of 20% / min. The tensile strength in Table 2 is a value in the rolling direction. Further, the anisotropy is 100 × (L−T) when 0.2% proof stress in the direction perpendicular to the rolling is “T” and 0.2% proof stress in the rolling direction is “L”.
/ L (%) value. Further, in order to evaluate the obtained sample, the relative X-ray intensity of the (200) plane after the recrystallization heat treatment of heating at 900 ° C. for 15 minutes is shown.

In any of the compositions shown in the table, the final cold rolling reduction was performed in the secondary work hardening region (region III), and the samples of the present invention had the final hardness and tensile strength in the regions I and II. It is higher than the applied material and shows excellent strength. Table 1
And the samples (3, 4, 5) and (10, 11,
12) and the like having the same final cold rolling rate in the alloy group of the same composition, the higher the hardness before the final cold rolling is, the higher the final hardness is, even if the final cold rolling rate is the same. In other words, it can be seen that the tensile strength is increased and the strength is superior. It can be seen that the higher the Ni content, the higher the strength as a whole, and also the higher the strength by adding Co. Among the samples of the present invention, 2, 26 and 31, which used more preferable manufacturing conditions, achieved high strength which was not obtained by this composition. Final Cold Rolling Area II
Although the strength anisotropy of the sample of the present invention subjected to the final cold rolling in I is larger than that of the material applied in the region I, the strength anisotropy is equal to or less than that of the material applied in the region II. It can be seen that the strength anisotropy decreases.

The samples shown in Table 1 have good solderability and plating properties which are indispensable as electronic component materials. Further, the samples of the present invention have high relative X-ray intensities of 80% or more on the (200) plane after heating at 900 ° C. for 15 minutes, and all of the comparative materials have lower than 80%. It is understood that the material of the present invention can be specified by the relative X-ray intensity after heating. It can be seen that the sample of the present invention in which the relative X-ray intensity of the (200) plane is 90% or more has higher intensity.

[0030]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, by applying the secondary work hardening region, the material has extremely high strength without depending on the additive element that deteriorates the etching property and the solder property, and the material is It is possible to suppress the anisotropy of. Therefore, the Fe-Ni alloy thin plate of the present invention can be applied to the thinning of electronic component materials such as lead frames, and has an extremely great industrial effect.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between final cold rolling rate and hardness of an Fe-42Ni alloy.

FIG. 2 is another diagram showing the relationship between the final cold rolling rate and hardness of the Fe-42Ni alloy.

Claims (5)

[Claims] 1. A composition having a composition of 28 to 55% by weight of Ni and the balance being substantially Fe, wherein the structure is a structure in which crystal grains are expanded through rolling in a secondary work hardening region, Vickers hardness is HV ≧ 220 + 0.5 [Ni] (%)
Fe-Ni alloy thin plate for electronic parts, which satisfies 2. Ni-28 to 55%, Co1 in weight%
2% or less, the balance being substantially Fe, and the structure is a structure in which crystal grains are expanded by rolling in the secondary work hardening region, and the hardness is Vickers hardness HV ≧ 220 + 0.
An Fe-Ni alloy thin plate for electronic parts, which satisfies 5 [Ni] (%) + 0.7 [Co] (%). 3. When heated at 900 ° C. for 15 minutes, X
In the relative X-ray intensity of the crystal plane by line diffraction (200)
The surface strength is 80% or more.
Alternatively, the thin plate for Fe-Ni alloy electronic component according to any one of 2). 4. An alloy containing 28 to 55% by weight of Ni, or 12% or less of Co, with the balance being essentially Fe, is subjected to hot rolling or at least once after hot rolling. After the cold rolling and annealing described above, the Vickers hardness H at the rolling rate corresponding to the secondary work hardening region where the hardness rapidly increases after the primary work hardening with respect to the rolling rate.
V ≧ 220 + 0.5 [Ni] (%) + 0.7 [Co]
(%), When not containing Co, [Co] = 0 is calculated, and the final cold rolling is performed so that the Fe-Ni alloy thin plate for electronic parts is manufactured. 5. Vickers hardness HV ≧ 125 + 0.5 [Ni] (%) is used for hot rolling or annealing before final cold rolling.
+1 [Co] (%), [Co] when not containing Co
It calculates so that it may be set as = 0, and it applies so that it may satisfy, The manufacturing method of the Fe-Ni type alloy thin plate for electronic components of Claim 4.