JP2953662B2 - Fe-Ni alloy for lead frame with excellent punchability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a Fe-
It is about Ni alloy.

[Conventional technology]

With respect to the characteristics of Fe—Ni alloys used for lead frames for ICs and the like, not only good punching properties but also properties relating to surface properties such as plating properties are becoming increasingly important.

However, regarding the surface properties, by introducing a chemical polishing step in the processing step to the lead frame,
It seems that the degree of dependence on the material is relatively small because consideration is given to obtain stable plating properties.

On the other hand, recent lead frames tend to be multi-pin and complicated, and the requirements from the end user regarding the shape of the lead frame after punching are becoming more stringent, or due to cost considerations, conventional lead frames have been replaced by etching methods. Due to the necessity of changing to the punching method and the like, a material having better punching properties is required.

[Problems to be solved by the invention]

Regarding the punchability of Fe-Ni alloys for lead frames, it has been considered that (1) mechanical properties of materials, (2) shape (flatness), and (3) residual stress have been important factors. Major improvements have been made in this regard. For example, JP-A-62-224636, JP-A-61-9552, JP-A-61-6251
And JP-A-61-3835.

However, as shown in FIG. 1 (a view in which most of the leads are omitted), in a multi-pin lead frame having 40 pins or more, the width of the lead 1 is extremely small and complicated, and the lead frame shown in FIGS. Inconveniences at the time of punching, such as the deviation 3 of the lead and the step 4 which are differences from the normal position 2 of the lead shown in the drawing, increase, and it is no longer possible to cope with only the above-mentioned factors affecting the punching performance. Here, the shift 3 of the lead is a phenomenon in which the intervals between the leads become uneven in a plane, and the step 4 of the lead is a phenomenon in which the position changes in the vertical direction.

In view of the above, it is an object of the present invention to improve the punchability of an Fe-Ni alloy for a lead frame and reduce lead shape defects at the time of punching.

[Means for solving the problem]

The present invention provides a lead having excellent punching characteristics, characterized in that the relative X-ray intensity of each crystal plane by X-ray diffraction satisfies the following table, and Ni is 30 to 55 wt%, the balance being Fe and unavoidable impurities. It is an Fe-Ni alloy for frames.

30% by weight of Ni in Fe-Ni alloy for IC lead frame
Below, the coefficient of thermal expansion of the alloy becomes large and does not match the coefficient of thermal expansion of the silicon chip of the IC. In addition, 55wt%
Exceeding 0.2% yield strength increases and the workability greatly decreases. Furthermore, containing a large amount of Ni is economically disadvantageous. For this reason, the Ni content is specified to be 30% to 55% by weight.

Fe-Ni alloys for IC lead frames are used after repeated cold rolling and intermediate annealing, and then subjected to finish rolling, strip cutting, and stress relief in view of the above-described punchability. In this state, the Fe-Ni alloy has a certain crystal orientation.

For the Fe-Ni alloy, (311) and (2
The relative X-ray intensities of the (20), (200), and (111) planes are obtained, and the degree of aggregation of the crystal orientation can be determined. This crystal orientation changes depending on the processing conditions. The present inventors have found that due to the difference in crystal orientation, the frequency of occurrence of defects such as deviation of the lead at the time of punching and steps is greatly different.

FIG. 4 shows the change in the relative X-ray intensity of each diffraction surface when the rolling degree was changed using the Fe—Ni alloy and when annealing was performed. Thus, it is apparent that the relative X-ray intensities of the (220) and (200) planes are significantly changed.

The inventors of the present invention have found that by controlling the relative X-ray intensity of the specific surface, it is possible to suppress the occurrence of defects such as deviation of the lead at the time of punching and a step. That is,
When the relative X-ray intensity of the (200) plane exceeds 50%, the anisotropy of the material becomes strong, and the lead tends to be displaced at the time of punching, and a step difference problem is easily caused.

From the above points, the relative X-ray intensity of the (200) plane is 25-50%
Specified in the range. The other relative X-ray intensities that satisfy the specified range of the relative X-ray intensity of the (200) plane and do not cause the deviation of the lead or the step difference at the time of punching are the (220) plane, the (311) plane,
30 ~ 50%, 5 ~ 20%, 3 ~ 1 for (111) plane
5%, which is defined in this range.

EXAMPLES Hereinafter, the present invention will be described based on one example.

By changing the processing condition of Fe-Ni alloy for IC lead frame consisting of 42wt% Ni, balance Fe and unavoidable impurities,
Materials having relative X-ray intensities as shown in the table were produced.
Next, this material was punched into a lead frame shown in FIG. The results are also shown in Table 1.

As is clear from Table 1, in the alloy of the present invention, both the deviation 3 of the lead after punching and the step 4 of the lead could be made less than 0.1 mm, and the punching properties as a lead frame were good. On the other hand, in the comparative alloy, the deviation 3 of the lead and the step of the lead were large, and a problem occurred in the punchability.

The relationship between the relative X-ray intensity and the shift 3 of the lead and the step 4 of the lead is the same even when the Ni content is changed.
The range of the relative X-ray intensity is 5 to 20, 30 to 50, 25 to 50, 3 to 15% with respect to the (311) (220) (200) (111) planes, respectively.
Was satisfied, the punching property was good.

〔The invention's effect〕

According to the present invention, by defining the relative X-ray intensity with respect to the diffraction surface, a Fe-Ni alloy for a lead frame having good punchability can be obtained, and the punching of a lead frame having a multi-pin lead can be achieved. Even if it is unplugged, the deviation of the lead and the step of the lead can be sufficiently tolerated, and the quality of the lead frame is greatly improved.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a lead frame, FIG. 2 is an explanatory view of a lead side, FIG. 3 is an explanatory view of a step of the lead, and FIG. 4 is a relation between X-ray intensity with respect to a diffraction surface and rolling and annealing. FIG. 1: Lead, 2: Normal position, 3: Lead shift, 4: Lead step

Claims (1)

(57) [Claims] An excellent punching characteristic characterized in that the relative X-ray intensity of each crystal plane by X-ray diffraction satisfies the following table, and Ni is 30 to 55 wt%, the balance being Fe and unavoidable impurities. Fe-Ni alloy for lead frames.