JPH06145811A - Manufacture of lead frame material - Google Patents

Abstract

PURPOSE:To manufacture a lead frame material having only a little shrinking rate after heating and residual stress and excellent stampping property by executing a strain-removing annealing at the specific temp. after slitting a cold rolled sheet material having a specific composition of Fe-Ni alloy and, executing leveler-straightening. CONSTITUTION:After working the Fe-Ni alloy containing 36-52wt.% Ni (particularly, about 42wt.%) into a thin sheet having about 0.25mm thickness by hot- rolling and few times of cold-rollings containing the annealing, the slitting is executed to the prescribed width as the lead frame. Successively, the annealing for removing the working strain is executed at 630-700 deg.C, and in order to prevent the development of burr and shear droop at the time of punching with a press in the following process caused by lowering of the hardness in this annealing, the leveler straightening is applied to increase the surface hardness. The lead frame having only a little shrinkage rate after heating and residual stress and only a little burr at the time of punching and excellent stamping property is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lead frame material which has a small amount of heat shrinkage and residual stress and has a small burr (excellent stamping property) during punching.

[0002]

2. Description of the Related Art Conventionally, for example, in the case of manufacturing an IC lead frame, a Fe--Ni-based metal material having excellent conductivity is used as a material. Specifically, Fe-42 for a lead frame is used. A strip made of (wt%) Ni alloy is used.

As a method for producing the Fe-42Ni alloy strip for the lead frame, for example, the following method is adopted. First, the Fe-Ni alloy sheet material is hot-rolled. Then, cold rolling is performed.

Further, softening annealing is performed once. Next, finish rolling is performed with a workability of 50% or less. Then, a band is manufactured by shearing (slitting) to a predetermined width. Then, in order to remove the strain due to the slit processing, strain relief annealing is performed at 600 ° C. or lower.

Thereafter, the strip (lead frame material) is subjected to processing such as press punching and strain relief annealing, and is further subjected to resin molding processing and the like.

[0006]

However, when a lead frame material is manufactured by such a manufacturing method,
The following problems are not always desirable. That is,
It is necessary to perform sufficient strain relief annealing at a high temperature in order to manufacture a lead frame material with small heat shrinkage (the dimensions change before and after annealing) and residual stress (in pressing, etc.). On the contrary, when the strain relief annealing is performed, the hardness of the lead frame material decreases. As a result, problems such as burrs and sagging occur at the time of punching with a press in a later step, and so-called stamping properties deteriorate.

If such burr or sagging occurs, problems such as mounting of ICs will occur. Therefore, in the past, with emphasis on improving stamping properties, insufficient strain relief annealing was performed at a low temperature of about 600 ° C. or less. Didn't. for that reason,
Although burr and sagging can be prevented, reduction of heat shrinkage amount and residual stress has not always been sufficiently achieved.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a method of manufacturing a lead frame material which has a small amount of heat shrinkage and residual stress and is excellent in stamping property.

[0009]

In order to achieve the above object, the present invention according to claim 1 provides a method of manufacturing a lead frame material made of a Fe-Ni-based metallic material, wherein Fe-36 to 5 are used.
After subjecting a material to be rolled made of a metal material of 2 wt% Ni to finish rolling, and then slitting, and further performing sufficient strain relief annealing in the range of 630 to 700 ° C. for the slitting, A gist is a method of manufacturing a lead frame material, which is characterized by performing leveler straightening.

Here, the lead frame is I
C lead frame can be mentioned. Further, as the Fe-Ni-based metallic material, an Fe-Ni alloy containing Ni in the range of 36 to 52% by weight can be mentioned, and among them, N is particularly preferable.
An i content of about 42% by weight is preferable because the amount of heat shrinkage during strain relief annealing is further reduced.

As the temperature range of the strain relief annealing, the range of 630 to 650 ° C. is particularly preferable among the above ranges.
When performing the leveler straightening, the intermesh (IM) varies a little depending on the diameter of the roller. For example, the maximum value (IM) ma of the intermesh is calculated by the following formula.
It is possible to find x.

[0012]

[Equation 1]

However, r: roller radius, a: distance between roller surfaces, t: plate thickness Therefore, for example, when the diameter of the roller is 20 mm, the intermesh is preferably 1.0 mm or more. By this leveler straightening, the surface hardness of the lead frame material increases, but the surface hardness is 200 to 25
The range of 0 Hv is preferable because the stamping property is good. The hardness of the central portion of the lead frame material is preferably in the range of 180 to 200 Hv because punching is easy.

[0014]

In the present invention, contrary to the conventional method, first, in order to greatly reduce the amount of heat shrinkage and the residual stress, sufficient strain relief annealing is performed at a high temperature after slit processing. When this sufficient strain relief annealing is performed, the hardness of the lead frame material is lowered, so leveler correction is next performed to increase the surface hardness of the lead frame material.

That is, the surface hardness and the intermesh (indentation amount) by the leveler correction have a constant relationship as shown in FIG. 4, and the surface hardness and the burr height as shown in FIG. Since there is a certain relationship with (stamping property), the stamping property can be improved by performing leveler correction.

The reason why the surface strength is increased by the leveler correction is that the leveler causes the strain ε to be larger on the surface side than on the center side of the plate material as shown in FIG. 6, and the larger the strain ε, the higher the hardness. It is thought that it will increase. That is, according to the first aspect of the invention, the material to be rolled made of a metallic material of Fe-36 to 52 wt% Ni is subjected to finish rolling, and then slit processing is performed, and further 630
Since sufficient strain relief annealing in the range of up to 700 ° C. is performed, the residual stress in slit processing is reduced and the heat shrinkage amount (in the later strain relief annealing) is reduced. next,
By performing the leveler straightening, the surface hardness of the lead frame material is increased, so that the stamping property is improved.
This makes it possible to achieve the goals of reducing the amount of heat expansion and contraction and residual stress and improving stamping properties.

[0017]

Next, preferred examples will be described in order to further clarify the present invention. In the present embodiment, as the material of the lead frame material, a material composed of, for example, Fe-42% Ni in the range of Fe-36 to 52 (weight)% Ni is used, and the lead frame 1 shown in FIG. Band 2
Was manufactured.

The material is repeatedly annealed and rolled several times to produce a rolled material having a thickness of 0.25 mm. Next, in a vacuum, the temperature is kept at about 1000 ° C. for 5 minutes and then cooled to perform softening annealing.

Next, a predetermined pressure is applied to cool the mixture to 5
Finish rolling is performed at a working rate of 0% or less to a thickness of 0.15 mm to form a rolled material having a width of about 400 mm. Next, as shown in FIG. 2A, the shearing rings 3 and 4 are used.
The rolled material 7 is sandwiched between the upper and lower rollers 5 and 6 provided with, and shearing (slitting) is performed in a width range of 20 to 70 (for example, 50 mm) as shown in FIG. 2B. ) Is performed to manufacture the strip-shaped lead frame material 8.

Thereafter, the lead frame material 8 is heated in an atmosphere of an inert gas (hydrogen or nitrogen) at a temperature of 630 to 7.
Sufficient strain relief annealing for slit processing is performed by holding in the range of 00 ° C (for example, 650 ° C) for about 1 minute.
By this strain relief annealing, the residual stress due to the slit processing is reduced to about 1/10, and the heat expansion / contraction amount in the strain relief annealing after the subsequent press working is greatly reduced to about 1/10.

Next, as shown in FIG. 3, for example, a roller leveler 11 in which two rollers 10 having a roll diameter of 10 mm are arranged on the upper side and three rollers 10 are arranged on the lower side is pushed in (intermesh IM). Is 1.5 mm, for example, and the leveler is corrected, and the surface hardness is 2 in Vickers hardness [Hv].
Increase to 00 or more.

After that, press punching and the like are performed, further, in vacuum, the temperature is kept at about 600 ° C. for 5 minutes, followed by cooling and strain relief annealing, and press punching and the like are performed again. A strip 2 having a large number of lead frames 1 shown in is formed. After that, the strip 2 is separated and the lead frame 1 is separated, and a resin molding process or the like is performed.

That is, in the method of manufacturing the lead frame material of this embodiment, the material to be rolled made of a metallic material of Fe-36 to 52 wt% Ni is subjected to finish rolling, then slit processing is performed, and further 630 to 630. Since sufficient strain relief annealing in the range of 700 ° C. is performed, residual stress due to slit processing is reduced, and the amount of heat expansion and contraction (in the strain relief annealing of later processing) is also reduced. Moreover, since the leveler straightening is performed after the sufficient strain relief annealing, the surface hardness of the lead frame material 8 is increased, whereby burrs and sagging can be prevented and the stamping property can be improved.

(Experimental Example 1) Next, an experimental example in which the relationship between the indentation amount and the surface hardness was confirmed will be described. In this experimental example,
Fe-42% Ni material is used, roller diameter is 10φm
m, as the pushing amount, 0.0, 0.5, 1.0, 2.0,
A change in surface hardness of the lead frame material was examined by adopting 3.0 and 4.0 mm. The result is shown in FIG.

As is clear from FIG. 4, the surface hardness increases as the indentation amount increases. In particular,
When the pushing amount is 1.0 mm or more, the surface hardness is 220 [H
v] or larger, which is preferable. (Experimental Example 2) Next, an experimental example in which the relationship between the surface hardness and the burr height was confirmed will be described.

In this experimental example, a material of Fe-42% Ni was used, and the surface hardness was 200, 220, 230, 240,
A stamping property was observed by press-punching a 250 [Hv] lead frame material and measuring the burr height. The result is shown in FIG.

As is apparent from FIG. 5, the burr height decreases as the surface hardness increases. Especially when the surface hardness is 220 [Hv] or more, the burr height is about 56.
It is preferable because it becomes as small as [μm] or less. Although the embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to these embodiments and can be implemented in various modes without departing from the scope of the invention.

[0028]

As described above, in the present invention, Fe-36
~ 52 wt% Ni for the material to be rolled made of a metal material,
After finish rolling, slitting is performed, and sufficient strain relief annealing in the range of 630 to 700 ° C. is performed, and then leveler correction is performed, so that heat shrinkage amount and residual stress are reduced and stamping property is improved. It has a remarkable effect that it can be realized together.

Therefore, it is possible to prevent the occurrence of burrs and sagging in the subsequent press working, and to make the amount of heat shrinkage in the strain relief annealing of the press working extremely small.

[Brief description of drawings]

FIG. 1 is a plan view showing a shape of a strip material of a lead frame manufactured by press punching in an example.

FIG. 2 is an explanatory diagram showing a method of slit processing.

FIG. 3 is an explanatory diagram showing a leveler correction method.

FIG. 4 is a graph showing the relationship between surface hardness and indentation amount.

FIG. 5 is a graph showing the relationship between burr height and surface hardness.

FIG. 6 is a graph showing the relationship between plate thickness and strain.

[Explanation of symbols]

 1 ... Lead frame 2 ... Band material 8 ... Lead frame material 11 ... Roller leveler

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C22C 38/08

Claims (1)

[Claims] 1. A method of manufacturing a lead frame material made of a Fe—Ni-based metallic material, wherein a material to be rolled made of a metallic material of Fe—36 to 52 wt% Ni is subjected to finish rolling and then slit processing is performed. 630-700 ° C for the slit processing
The method for manufacturing a lead frame material, which comprises performing leveler straightening after performing sufficient strain relief annealing in the range.