JPH05165B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling residual stress in a metal plate,
More specifically, slit distortion occurs in the metal plate obtained by slitting a wide metal strip, but in order to prevent this from causing abnormal distortion during subsequent secondary processing, the metal plate is processed. method for controlling and modifying residual stresses.

(Prior art) Metal ribbons used in IC lead frames and the like are obtained by slitting a wide metal strip cold-rolled to a predetermined thickness to a predetermined width, and then
This metal plate is punched or photoetched into products such as lead frames of predetermined shapes and dimensions.

At that time, significant residual stress is generated near the edges (end faces) of the metal plate due to the slit processing, and when punching or photo etching is performed in this state, some of this residual stress is partially released and the stress Since the distribution is unbalanced, abnormal distortion occurs, resulting in the problem that products such as lead frames with good shape accuracy cannot be obtained.

(Object of the Invention) The present invention has been made to solve the above-mentioned problems, and is to correct the slit distortion generated in the metal plate after slitting by a simple means, and to The object of the present invention is to provide a method that enables products such as lead frames that do not cause abnormal distortion and have good shape accuracy.

(Structure of the Invention) In order to achieve the above object, the present inventors have tried a method of subjecting a metal plate to stress relief annealing, but in this method, the strength is increased by work hardening through cold rolling. Considering that this is not necessarily a preferable method as it has the disadvantage of not being able to maintain its original state and softening, it is a method that can be used at room temperature, and is simple and does not require the addition of a separate process. As a result of studying the means, we found that it is possible to pull out the metal plate at room temperature with an edge roller or a hole die, and have conceived the present invention.

The present invention will be explained in detail below.

As mentioned above, significant residual stress is generated in the metal plate after the slit processing, and slit distortion appears. This point will be explained using FIG.

In FIG. 1, a indicates a cross section of the metal plate, and the lugs 2 of the metal plate 1 are slit-processed. In this state, the strain distribution in the length direction of the metal plate 1 is such that, as shown in b, an elongation strain (+) is generated near the ears due to the slit processing. The distribution of residual stress caused by this strain is as shown in c, where a compressive residual stress (-) is generated near the edge of the metal plate, and in order to maintain stress balance with this, a tensile stress is applied to the central part. This results in a residual stress (+) of .

Then, the metal plate 1 with such residual stress
When photo-etched into a strip shape as shown in d (however, the pin 3, including the ears, is chemically corroded to prevent distortion), the compressive residual stress, which increases toward the outside, is removed. Since it is released, the pin 3 stretches more outwardly, and as a result, the pin 3 bends more inwardly. The strain testing method by photo-etching the strips is based on the method used to determine residual stress in metal plates used in IC lead frames.

In the present invention, based on the knowledge that in order to control the distortion of the slit ears without heating, it is necessary to change the distribution of residual stress in this part, this has been made possible by cutting the corners of the slit ears. It is something.

That is, as shown in Figure 2a, when the corner of the edge of the metal plate is plastically deformed into the shape shown in 4 by drawing with an edge roller or a hole die, a portion of area 4-1 is removed. The width is expanded to an area of 4-2. As a result, as shown in b, the elongation in the length direction is corrected to be smaller in the portion that has expanded to this width, and the strain distribution 5 up to the slit is corrected to a distribution 6. As a result, the distribution of residual stress is also modified from 7 to 8, which is the same as the slit, as shown in c. That is, the compressive residual stress in the ear portion becomes smaller, and the gradient of the stress distribution also becomes smaller. In this regard, the photoetching test also shows that the bending of the pin including the ears is significantly smaller than that of slit 3, as shown in 3', to the extent that it is not substantially affected by secondary processing, as shown in d. This was confirmed.

Note that slitting often causes bending in the thickness direction of the metal plate, which also causes harmful distortion.
This bending can be sufficiently removed by straightening with a commonly used roller leveler.

Furthermore, although the above-mentioned corner cutting process is performed using an edge roller or a hole die, it is practical to install a device for this purpose in connection with the exit side of the slitter processing machine.

Example 1 42% Ni steel plate thickness 0.25mm for IC lead frame
× A 400 mm wide strip was slit to obtain 9 ribbons with a 40 mm width. One of them was left with a slit, and the other one had its ears pulled out with a roller to the shape and dimensions shown in FIG. After straightening the bends in the thickness direction of these ribbons using a roller leveler,
It was processed into a strip by photo etching. In this case, the pin width is 0.9mm, the gap between the pins is 0.3mm,
The length of the pin was 120 mm. As a result of measuring the lateral bending of each pin in the plane of the pin, including the ears, it was found that at the tip of the pin, the ribbon without slits
It was 9.5mm, but the corner-cut ribbon was 1.5mm.
It became noticeably smaller.

Example 2 42% Ni steel plate thickness 0.25mm for IC lead frame
× A striped clad band with a width of 25 mm, made by cladding aluminum with a thickness of 5 μm and a width of 5.0 mm on one surface in the center in the width direction, is slitted to a width of 23 mm, then divided into two parts, and one A hole die was drawn into the shape and size of the ear shown in FIG. 4. Each ribbon was processed into a strip by photoetching, and the lateral bending of the pin including the ears was measured. As a result, the slit material has a diameter of 12 mm.
In contrast, it was significantly smaller at 2.0 mm for the cut-off material.

Example 3 A phosphor bronze strip for IC lead frames with a thickness of 0.25 mm and a width of 100 mm was slit to obtain two ribbons with a width of 40 mm. One of these is left with a slit, and the other one is cut with a roller to the shape and dimensions shown in Figure 5, and then both are leveled and photo-etched into a strip shape to remove the pin including the ears. Lateral bending was measured. As a result, the bending of the slit-shaped material was 6.5 mm, while the bending of the corner-cut material was 0.5 mm.
improved.

(Effects of the Invention) As is clear from the detailed description above, according to the present invention, the residual stress caused by slit distortion can be easily controlled and corrected by corner cutting, and since this is done at room temperature, the strength of the softening etc. Products such as lead frames with good shape accuracy can be obtained without the above problems. In addition, in practical terms, by connecting and installing a corner removing device such as an edge removing device on the exit side of the slitter processing machine, it is possible to remove distortion without increasing the number of processes. It has great effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the metal plate after slitting and the occurrence of strain in the slit, in which a is a cross-sectional view of the metal plate, b is a strain distribution, c is a residual stress distribution, and d is a cross-sectional view of the metal plate. The state after the photo etching process is shown, and FIG. 2 is a diagram for explaining the corner cutting process and its effect in the present invention, in which a shows the area where the corner cutting is applied, b shows the strain distribution, and c shows the area where the corner cutting is applied. The residual stress distribution is shown, d shows the state after the photoetching process, and FIGS. 3 to 5 are diagrams each showing a corner cutting process according to an embodiment of the present invention. 1... Metal plate, 2... Ear (end surface), 3, 3'...
pin.

Claims (1)

[Claims] 1. A method for controlling residual stress in a metal plate, characterized in that in controlling and correcting residual stress caused by slit distortion generated in a slit-processed metal plate, the corners of the end faces of the metal plate are rounded.