JP3356992B2 - Fe-Ni-based lead frame material excellent in punching workability, Fe-Ni-based press-punched product, and method of punching Fe-Ni-based material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fe-Ni-based lead frame material having good punching characteristics, and by controlling the size of nonmetallic inclusions to improve the shearing characteristics at the time of punching. It relates to a technique for obtaining excellent punching characteristics.

[0002]

2. Description of the Related Art In recent years, the number of pins in a lead frame has been increasing, as represented by a flat package, and the required level of miniaturization has been increasing. In general, lead frame materials are divided into punching applications in which the lead pattern is formed by punching and etching applications in which the lead pattern is formed by etching with a ferric chloride solution. Suitable for forming. In general, the characteristics required for lead frame materials include excellent punching characteristics, excellent workability in press working, good solderability, plating properties, and problems when bonding with semiconductor elements. No deformation, high strength after processing, low deformation, high electrical conductivity, and the actual operating temperature 2
Low thermal expansion coefficient at 00 ° C. or lower. The manufacturing process of an IC semiconductor package using a punched lead frame can be roughly divided as follows.

(1) Punching of a material (lead frame material) (2) Mounting step of mounting a lead frame on a resin mold (3) Bonding step of connecting a lead frame and a semiconductor element with a conductive wire

Here, the punching property is required in the step 1, the press formability is required in the step 2, and the plating property and the solderability are required in the step 3 respectively. The strength after the processing is required because it is necessary that deformation such as warpage or bending is less likely to occur at the time of bonding, and that the yield is prevented from lowering due to occurrence of defects due to deformation during handling. The electrical conductivity is
It affects the heat generated by the current flowing through the leads and affects the stability of the operation of the semiconductor element. Lead frame materials include
It is necessary that the thermal expansion coefficient of the semiconductor element or the mold resin be close to that of the semiconductor element or the mold resin in order to prevent the characteristic fluctuation of the semiconductor element due to the distortion caused by the difference in thermal expansion during the assembly process due to heating and the deterioration of the adhesion with the mold resin. Have been. As a typical metal material that meets such demands,
Fe-42Ni alloy, Fe-45Ni alloy, Fe-50
A material such as a Ni alloy is used.

[0005] In terms of heat conduction, copper alloys are more advantageous than Fe-Ni alloys. However, recently, the effective ratio due to the improvement of the stability of semiconductor elements, the improvement of heat dissipation, and the improvement of the shape of leads (thinning) has been improved. Due to individual improvements such as reduced resistance, the thermal conductivity of Fe-Ni alloys is not a technical bottleneck. On the other hand, regarding the punching property, the quality variation in this process greatly affects the yield of products, and it is considered to be an important process along with the trend of higher definition and more pins in the future. Are being considered. As an attempt to improve the punching performance so far, as disclosed in, for example, JP-A-61-44156, the size of inclusions having a cross section parallel to the rolling direction is set to 5 μm or less,
B-type inclusions having a total number of 20 or more per 1 mm ² or those in which fine non-metallic inclusions having a particle size of 3 μm or less are uniformly dispersed in the structure as shown in JP-A-60-255953. is there. Further, JP-A-9-87808, 24
As shown in 9943, 10 to 1000 A- or B-based inclusions having a size of 10 μm or more per 1 mm ^{2 in} cross-sectional area parallel to the rolling and sheet pressure directions were used. The number is limited to 100 to 50,000, and the number of sulfide inclusion traces after etching is set to 1000 to 200.
In many cases, inclusions are positively used to improve punchability, such as zero. Also, JP-A-63-24
By performing the refining temperature outside the furnace at 1700 ° C. or lower as shown in FIG. 010, the formation of inclusions of spinel-based oxides such as MgO—Al ₂ O ₃ having a size exceeding 10 μm, which is harmful to punching properties, can be prevented. Suppression techniques have also been proposed.
These facts show how important inclusion control is to punching performance.

[0006]

In a lead frame material, not only does the performance of the product deteriorate due to burrs and scum generated at the time of press punching, but also the mold is damaged or warped or bent due to residual stress. Trouble occurs in handling. For this reason, in a semiconductor manufacturing process, it may hinder stable manufacturing or lower the yield, which may cause a serious trouble. In recent years, as the fineness of the leads has increased, the clearance of the mold has been set to a small value.This has resulted in the generation of scraps during pressing and the shortening of the mold life, and the boundary between the shear surface and the fracture surface has been disturbed. Large burrs are generated. For this reason, recently, materials having good punching properties have been increasingly demanded, but in order to satisfy such demands, control of the above-described inclusions alone was not sufficient.

[0007]

Means for Solving the Problems The present inventor has proposed Fe-Ni
As a result of examining the effect of inclusions on the punchability of lead frame materials, the form of the fracture surface, that is, the boundary between It has been found that the linearity is greatly affected.

[0008] The present invention has been made based on the above findings, and in a Fe-Ni-based lead frame material containing 30 to 50% by weight of Ni, the size of inclusions contained in the material is determined by the thickness of the material. Is set to 0.07t or less when t is set to t. Further, the Fe-Ni of the present invention
In the method of punching a Fe-Ni alloy material containing 30 to 50% by weight of Ni using a punch and a die, the size of the inclusions contained in the material is determined by:
The feature is that it is smaller than the clearance between the punch and the die. Note that a typical Fe—Ni-based material is a lead frame material.

In general, the clearance when punching a lead frame by a press is set to a maximum of 0.07 t when the thickness is t. In the above lead frame material, since the size of the inclusions is set to 0.07 t or less,
The inclusions can generally pass through the clearance, and the linearity of the boundary between the shear surface and the fracture surface is obtained. In addition, since the clearance may be set to a minimum of 0.03 t, if the size of the inclusion is 0.03 t or less, the linearity of the boundary between the shear surface and the fracture surface can be reliably obtained. .

[0010] The shear resistance of the press is greater when the material is sheared in a plane perpendicular to the rolling direction than in a plane parallel to the rolling direction. This is because the inclusions extend in the rolling direction, and therefore, the frequency of inclusions on the punched surface is high in a plane parallel to the rolling direction. Such anisotropy of the shear load has to be suppressed as much as possible to cause a problem of residual stress. Then, the present inventor quantitatively analyzed MnS, which is known to contribute to free-cutting ability among inclusions, and found that MnS having a particle size of 0.2 to 3 μm.
By dispersing nS at a rate of 1000 to 60,000 particles / mm ² , it was found that breakage occurs uniformly on any surface. Therefore, the Fe—Ni-based lead frame material of the present invention is a Fe—N alloy containing 30 to 50% by weight of Ni.
In the i-type lead frame material, the size of the inclusions contained in the material is 0.07 when the thickness of the material is t.
t and MnS having a particle size of 0.2 to 3 μm
It is characterized by being dispersed at a rate of 00 to 60,000 particles / mm ² . The particle size of MnS is preferably 2 μm or less, and more preferably 1 μm or less. Further, MnS is preferably dispersed at a rate of 2000 / mm ² or more, more preferably 5000 / mm ² or more, and even more preferably 10,000 / mm ² or more. In addition, MnS was 50,000 / mm ²
The following is preferable, and it is more preferable that it is 40,000 pieces / mm ² or less, and it is further preferable that it is 30,000 pieces / mm ² or less.

Next, a preferred component composition of the present invention will be described. The preferred composition of the Fe—Ni-based lead frame alloy of the present invention is C: 0.003 to 0.1% by weight.
02%, Si: 0.05 to 1.0%, Mn: 0.1 to
1.5%, Ni: 30-50%, S: 0.0005-
0.02%, N: 0.001 to 0.02%, balance: Fe
And unavoidable impurities. Hereinafter, the grounds of the above limitation will be described. In the following description, “%” means “% by weight”.

C: Since C is an element that contributes to solid solution strengthening and material strengthening by work hardening, it needs to be added in an amount of 0.003% or more. On the other hand, if the C content is too large, the electrical resistance is increased and the conductivity is deteriorated. In addition, a large amount of carbide is precipitated and hot workability and toughness (repeated bending property, etc.) are obtained.
In addition, the punching property is deteriorated, and the low thermal expansion characteristic inherent in the Fe—Ni alloy is impaired. for that reason,
The content of C was regulated to 0.003 to 0.02%.

Si: Si is added as a deoxidizing agent, but if its content is too large, low thermal expansion characteristics are impaired similarly to C, and the punching properties are reduced. On the other hand, an oxide of Si becomes a starting point of precipitation of sulfides such as MnS generated by heterogeneous nucleation in the structure, and therefore, it is desirable to add an appropriate amount thereof. From such a viewpoint, the content of Si is 0.05 to 1.0%.
And

Mn: Mn is one of the deoxidizing components like Si, but it is effective for improving hot workability because it combines with S which is harmful to hot workability to form MnS. . Further, like Si, the Mn oxide becomes a starting point of precipitation of sulfides such as MnS generated by heterogeneous nucleation in the structure, and therefore, it is desirable to add an appropriate amount thereof. On the other hand, if the added amount of Mn is too large, the coefficient of thermal expansion becomes high, and the difference from the coefficient of thermal expansion with the semiconductor element becomes large, making it unsuitable as a base material. From the above viewpoint, the content of Mn is set to 0.1 to 1.5%.

S: S is a component harmful to hot workability, but is a component necessary for producing sulfides such as MnS useful for punching properties. is necessary. From such a viewpoint, the content of S is 0.000.
5 to 0.02%. N: N is also a harmful component to hot workability, but like C, it is an element that contributes to solid solution strengthening and material strengthening by work hardening, so an appropriate amount of addition is required. From such a viewpoint, the content of N is set to 0.001 to 0.02%.

Ni: If Ni is less than 30%, martensite is formed even in an annealed state, and magnetic properties, thermal expansion properties, strength, and other physical properties are impaired.
% Or more is required. However, Ni is 50
%, The electric resistance and the saturation magnetic flux density decrease, and the coefficient of thermal expansion increases, which is not preferable.
Since the cost is disadvantageous, the upper limit is set to 50%.

It is desirable that at least one of Ti, Zr, Mg and Ca is contained in a total amount of 0.0001 to 0.01% by weight. All of these are elements that form an oxide that becomes a nucleus site where MnS precipitates during solidification, and are necessary to make the form of MnS spherical and finely disperse it. The total amount of these elements is 0.0
If the amount is less than 001% by weight, the above effects cannot be expected. If the amount exceeds 0.01% by weight, the thermal expansion coefficient increases and the plating property is impaired.

Next, the inventor examined the linearity of the boundary between the shear surface and the fracture surface in the punched fracture surface (hereinafter, referred to as the fracture surface uniformity). The uniformity of the fracture surface
Although it is obtained by improving the punching workability of the material as described above, it also serves as an index indicating the possibility of temporal deformation due to residual stress. Therefore, the present inventors quantitatively analyzed the uniformity of the fracture surface by the following method.

Firstly, by observing the fracture surface was punched by a press with an optical microscope, and the fracture surface height 5μm intervals measured 50 points the average value s of the fracture surface height h _n. The standard deviations were calculated by substituting h _n and s in Equation 1.

(Equation 2)

According to the study of the present inventor, it has been found that if the standard deviation of the fracture surface height is 15 or less, deformation of the material after punching hardly occurs. Therefore, the present invention has been made on the basis of such findings, and has a Ni content of 30 to 50.
Weight percent Fe-Ni press stamped product,
The standard deviation obtained by observing the punched fracture surface with an optical microscope and measuring 50 points of the fracture surface width at intervals of 5 μm is 15 or less. This standard deviation is preferably 10 or less, and more preferably 5 or less.
Note that a typical stamped product is a lead frame.

[0021]

Hereinafter, the present invention will be described in more detail with reference to specific examples. Fe-Fe-42%
The Ni-based alloy was melted into a steel ingot in a vacuum melting furnace. At that time, in order to change the form, size, and number of oxide-based inclusions and MnS, melting conditions, agglomeration conditions, and the timing and amount of addition of the deoxidizing agent were appropriately selected. Thereafter, forging was performed on each steel ingot, and normal hot rolling, cold rolling, and annealing were performed to obtain a cold-rolled sheet having a sheet thickness of 0.15 mm. The surface of each cold rolled sheet is corroded by SPEED method and SEM photograph (7000x,
17 μm × 11 μm, average of 10 visual fields)
The size of the oxide-based inclusions and the number of MnS were measured, and the measurement results are shown in Table 1 together with the component composition of each cold-rolled sheet. The size of the oxide-based inclusions was an average of at most 10 inclusions. FIG. 3 is an example of an SEM photograph, in which (a) shows seven MnS and (b) shows two MnS.

[0022]

[Table 1]

Each of the cold rolled sheets was subjected to a punching test by the following method. First, a 10-ton press was used under the condition of 230 spm, the clearance was 4.5 μm, and the cold-rolled sheet was 1
A 2 mm square was punched out. The fracture surface at that time was observed with an optical microscope, and the fracture surface ratio and the uniformity of the fracture surface were determined.
Fracture surface ratio (%) of the fracture surface height h _n at 5μm intervals measured 50 points against fracture surface was calculated by dividing the average value s in thickness. Also, the uniformity of the fracture surface, fracture surface height h _n
And its average value s was substituted into the above equation 1 to calculate a standard deviation, and the value was evaluated based on the calculated standard deviation.

Next, as shown in FIG. 1, a 12 mm square punch is used for a cold rolled sheet having a width of 10 mm and a length of 120 mm, and a direction (P direction) parallel to the rolling direction (RD). A punching test was performed in a direction (R direction) orthogonal to the above. At that time, the punching speed of the press was set to 0.5 mm / min, and the punch stroke value from when the punch came into contact with the cold rolled sheet until when the punch was cut was measured. The anisotropy (%) was calculated by substituting the punch stroke value (P) in the P direction and the punch stroke value (R) in the R direction into the following equation, and the results are also shown in Table 1.

## EQU2 ## (RP) / P × 100

As can be seen from Table 1, in the examples of the present invention in which the size of the oxide-based inclusions is not more than the clearance (4.5 μm), the standard deviation indicating the uniformity of the fracture surface is small, and FIG. The fracture surface as shown in d) was exhibited. On the other hand, in the comparative examples in which the size of the oxide inclusions exceeded 4.5 μm, the standard deviation was large in each case, and the fracture surfaces shown in FIGS. 2A to 2C were exhibited. Further, in each of the examples of the present invention, since MnS having a particle size of about 0.2 to 1 μm is dispersed at a rate of 1000 to 60,000 particles / mm ² , the anisotropy of the shear resistance is considerably smaller than that of the comparative example. Has become.

[0026]

As described above, according to the present invention, the uniformity of the fractured surface can be improved, so that there is no material defect due to the generation of burrs in the punching process of the lead frame material and the defect due to handling. It can be expected that the life of the mold will be greatly improved, and it will be possible to supply parts that are excellent in improving the definition, reliability and production efficiency of lead frame materials for IC packages in recent years. .

[Brief description of the drawings]

FIG. 1 is a plan view for explaining a punching test for examining anisotropy of shear resistance.

FIG. 2 is a view showing a punched surface of each cold rolled sheet.

FIG. 3 is a SEM photograph of a cold rolled sheet surface corroded by a SPEED method.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhide Kuroda 4-2 Kojimacho, Kawasaki-ku, Kawasaki-shi, Kanagawa Nippon Yakin Kogyo Co., Ltd. R & D Headquarters R & D Headquarters (72) Inventor Hidekazu Todoroki Kawasaki-ku, Kawasaki-shi, Kanagawa No.4-2, Kojimacho Nippon Yakin Kogyo Co., Ltd. Research and Development Division Technology Research Laboratory (56) References JP-A-60-255953 (JP, A) JP-A-9-249943 (JP, A) JP-A-61-44156 (JP, A) JP-A-7-34200 (JP, A) JP-A-7-179998 (JP, A) JP-A-2000-17400 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) C22C 38/00-38/60

Claims (3)

(57) [Claims] C: 0.003 to 0.02 by weight%
%, Si: 0.05 to 1.0%, Mn: 0.1 to 1.5
%, Ni: 30 to 50%, S: 0.0005 to 0.02
%, N: 0.001 to 0.02%, Ti, Zr, Mg,
And at least one of Ca and 0.000 in total.
1-0.01% by weight, balance: Fe-
In the Ni-based lead frame material, the size of the inclusions included in the material is 0.0 when the thickness of the material is t.
7t or less and MnS having a particle size of 0.2 to 1 μm
A lead frame material excellent in punching workability, characterized by being dispersed at a rate of 000 to 60,000 pieces / mm ² . 2. C: 0.003 to 0.02 by weight%
%, Si: 0.05 to 1.0%, Mn: 0.1 to 1.5
%, Ni: 30 to 50%, S: 0.0005 to 0.02
%, N: 0.001 to 0.02%, Ti, Zr, Mg,
And at least one of Ca and 0.000 in total.
1-0.01% by weight, balance: Fe-
In a Ni-based stamped product, the size of inclusions contained in the material is set to 0.07 t or less when the thickness of the material is t, and MnS having a particle size of 0.2 to 1 μm is 1000
６０60,000 pieces / mm ² dispersed and punched
Observe the fracture surface with an optical microscope and measure the fracture surface height at 5 μm intervals.
It measured 50 points, an average value s of the fracture surface height h _n, h
_The standard deviation calculated by substituting _n and s into Equation 1 is 15
Fe-Ni based press punching characterized by the following:
Goods . (Equation 1) 3. C: 0.003 to 0.02 by weight%
%, Si: 0.05 to 1.0%, Mn: 0.1 to 1.5
%, Ni: 30 to 50%, S: 0.0005 to 0.02
%, N: 0.001 to 0.02%, at least one of Ti, Zr, Mg and Ca in a total amount of 0.000 %
1 to 0.01% by weight , balance: Fe
The size of the inclusions contained in the material is represented by t
0.07t or less, and a particle size of 0.2 to 1
The rate of 1000 to 60000 MnS of μm / mm ²
Of Fe-Ni-based lead frame material dispersed by
A come method, Pont the size of the inclusions contained in the material
The feature is to make it smaller than the clearance between the die and the die
Punching method of Fe-Ni-based material .