JP2812879B2 - Plate material for electric and electronic parts and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip material for electric and electronic parts suitable as a material for a lead frame and a method for producing the same.

[0002]

2. Description of the Related Art Metal or alloy tapes, plates or strips (hereinafter referred to as plate strips) for electric and electronic parts such as IC lead frames are usually manufactured by rolling. The flat plate material for the IC lead frame is required to have flatness in order to avoid occurrence of a defect in a wire bonding step or the like. For this reason, conventionally, in the manufacturing process of the plate material for an IC lead frame, there is provided a process of correcting the distortion by passing the plate material formed by rolling through a tension leveler (Japanese Patent Application Laid-Open No. 4-94815). . In this case, low-temperature annealing may be performed before and / or after the tension leveler step in order to more reliably remove the residual stress. An IC lead frame is manufactured by cutting a plate material having a strain corrected in this way to a predetermined width, and then forming the strip material into a predetermined shape by etching or stamping. In addition, processing such as degreasing, pickling, and polishing is appropriately performed before the final rolled material is formed into a lead frame.

[0003]

However, the conventional strips for electric and electronic parts manufactured by the above-described method have the following problems. 6A and 6B are perspective views each showing a part of an IC (integrated circuit device). These ICs are formed by mounting a semiconductor chip on an island portion of a lead frame and molding the semiconductor chip with a resin or the like. In this case, as shown in FIG. 6A, the case where the outer lead 14 is linearly led out of the mold portion 13 in the horizontal direction, and FIG.
As shown in (b), the outer lead 16 led out from the resin mold portion 15 may be bent into a crank shape. In the manufacturing process of such an IC, the lead frame is deformed in the process of processing the conventional strip material into the shape of the lead frame and in the heat treatment process after processing into the lead frame, and the leads 14 and 16 are deformed by the lead frame plate. Deforms in the thickness and width directions. Conventionally, the coplanarity of the IC leads 14 and 16 in the thickness direction is 20 μm.
m, and the coplanarity in the plate width direction exceeded 30 μm. Note that coplanarity refers to flatness, and is a height difference between the highest portion and the lowest portion on the surface of the plate.

[0004] Such lead deformation occurs due to the residual stress of the strip material. FIG. 7 is a schematic diagram showing a residual stress distribution in a thickness direction in a cross section parallel to a rolling direction of a conventional lead frame plate or strip. As shown in FIG. 7, the sum of the absolute value of the tensile stress (positive value) remaining at the center in the thickness direction of the plate member 11 and the compressive stress (negative value) remaining at the end ( A) is large. Similarly, in the conventional strip material for electric and electronic parts, the residual stress in the thickness direction and the width direction during rolling is large and not uniform. For this reason, in the state of the strip material, no deformation occurs because the tensile stress and the compressive stress are balanced, but the balance between the tensile stress and the compressive stress in the process of processing into a lead frame or the like and the heat treatment process after processing. Collapses, and deformation occurs in the sheet thickness direction and the sheet width direction.

The present invention has been made in view of the above problems, and has low residual stress and uniformity. For example, in a process of processing into a lead frame or a heat treatment process after processing into a lead frame, deformation of the lead is prevented. It is an object of the present invention to provide a plate material for electric and electronic parts which is less likely to be generated and a method for producing the same.

[0006]

The strip material for electric / electronic parts according to the present invention is a strip material made of a metal, metal alloy, tape, plate or strip, and has a cross section parallel to the rolling direction and a cross section perpendicular to the rolling direction. , The sum of the absolute value of the compressive stress and the absolute value of the tensile stress is 12 kgf
/ Mm ² or less.

Further, according to the method of manufacturing a strip material for an electric / electronic part according to the present invention, a metal or alloy tape, plate or strip material is passed through a tension leveler to determine the height of the wave-like strain and the wave pitch. A first tension leveler step for reducing the steepness obtained by dividing the sheet material by 1.0% or less, and passing the plate material after the first tension leveler step through the tension leveler while maintaining a constant tension. A second tension leveler process in which the sum of the absolute value of the compressive stress and the absolute value of the tensile stress is 12 kgf / mm ² or less in the residual stress distribution in the thickness direction in the cross section parallel to and perpendicular to the rolling direction, respectively. And the following.

[0008] Further, another manufacturing method of the strip material for electric and electronic parts according to the present invention includes a first tension leveler step of passing a metal or alloy tape, plate or strip plate material through a tension leveler; After completion of the first tension leveler step, the sheet material is passed through a tension leveler at a tension of 1/3 or less of the tension in the first tension leveler step, and a thickness in a cross section parallel to the rolling direction and a cross section orthogonal to the rolling direction. In the residual stress distribution in each direction, the sum of the absolute value of the compressive stress and the absolute value of the tensile stress was 12 kgf / mm.
^{A second} tension leveler step of reducing the number to ² or less.

[0009] The steepness is obtained by dividing the height of the wavy strain generated in the strip by the pitch of the waves. Specifically, as shown in FIG. 8, when the distance between the wave bottoms of the wavy distortion generated in the tape, the plate or the strip made of strip is L, and the height is H, the steepness = ( H / L) × 100.

In the present application, the sum of the absolute value of the compressive stress and the absolute value of the tensile stress in the residual stress distribution in the thickness direction is defined as the absolute value of the maximum value of the compressive stress in the residual stress distribution in the thickness direction and the tensile value. The sum of the maximum value of the stress and the absolute value.

Further, the first and second tension leveler steps may be performed continuously by, for example, two tension levelers, or may be performed individually (discontinuously).

[0012]

The present inventors have conducted various experimental studies to suppress the deformation of the leads of a lead frame formed of a tape, a plate, or a plate material for an electric / electronic component made of a material having a rectangular cross section. As a result, for example, in a lead frame,
In order to reduce the coplanarity of the leads arranged at a pitch of 0.4 mm to 20 μm or less, the absolute value of the compressive stress in the residual stress distribution in the thickness direction in the cross section parallel to the rolling direction and the cross section orthogonal to the rolling direction of the lead frame. It was found that the sum of the absolute value of the stress and the absolute value of the tensile stress was required to be 12 kgf / mm ² or less.

Further, the inventors of the present invention set the tension applied to the sheet material to be low at the time of correcting the distortion by the tension leveler, and set the sum of the absolute value of the compressive stress and the absolute value of the tensile stress in the residual stress distribution in the thickness direction. Was found to be smaller. However, if the tension at the time of passing through the tension leveler is reduced, the distortion of the strip material cannot be corrected.

Therefore, in the first invention method of the present application, first, as a first tension leveler step, the plate material is passed through a tension leveler while applying a relatively large tension to reduce the steepness to 1.0% or less. By doing so, the flatness required as a plate material for electric and electronic components such as a lead frame is secured. After the completion of the first tension leveler step, the plate material has good flatness, but has relatively large residual stress in the stress distribution in the thickness direction. In order to reduce the residual stress, as a second tension leveler step, the plate material is passed through the tension leveler while keeping the tension constant. Thereby, the residual stress can be reduced, and the sum of the absolute value of the compressive stress and the absolute value of the tensile stress in the cross section parallel to the rolling direction and the distribution of the residual stress in the thickness direction in the cross section orthogonal to the rolling direction is 12 kgf / mm
² or less. Thereby, for example, in the lead frame, the coplanarity of the leads arranged at a pitch of 0.4 mm can be set to 20 μm or less.

[0015] In the second invention method of the present application,
First, in a first tension leveler step, the plate material is passed through a tension leveler while applying a relatively large tension to secure a desired flatness, and then, in a second tension leveler process, the first strip material is applied to the plate material. Through the tension leveler while applying a tension of 1/3 or less of the tension in the tension leveler process, the residual stress distribution in the thickness direction in a cross section parallel to the rolling direction and a cross section orthogonal to the rolling direction,
The sum of the absolute value of the compressive stress and the absolute value of the tensile stress is 12
kgf / mm ² or less. Thereby, for example, the deformation of the lead in the step of processing the plate material into the lead frame and the heat treatment step after the processing can be reduced.

In the first and second invention methods,
As the tension in the first tension leveler process increases, the steepness of the strip material decreases, but if the tension is too high, the residual stress of the material after the first tension leveler process increases, and the second tension leveler increases. In order to reduce the residual stress in the process, the tension in the second tension leveler process needs to be close to one third of the tension in the first tension leveler process, and it becomes difficult to sufficiently reduce the residual stress. For this reason, the tension in the first tension leveler step is 9 to 25 kgf / mm.
It is preferred to be about ² . Further, by setting the tension in the second tension leveler step to 3 to 8 kgf / mm ² , the residual stress can be reduced more reliably. Further, when a work roll having a small diameter (16 mm or less) is used as the work roll of the tension leveler, the residual stress can be further reduced.

Although the present invention is mainly directed to a Cu alloy used for a lead frame, the present invention can be applied to other metals or alloys.

[0018]

Next, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic view showing a tension leveler used in a method of manufacturing a strip material for an electric / electronic component according to an embodiment of the present invention. The tension leveler includes a plurality of work rolls 1 and first and second intermediate rolls 2 and 3.
As shown in FIG. 2, a large amount x ₁ bite roll of the roll 1 of the entry side is set so that the amount x _n bite roll as the subsequent roll 1 is decreased. First and second
The intermediate rolls 2 and 3 are provided in order to reinforce the strength of the first work roll against bending stress. Also,
Bridle sections 4 and 5 each composed of a plurality of rolls are provided on the entrance side and the exit side of the tension leveler. The tension of the material to be processed (rolled material 10) between the bridle portions 4 and 5 can be adjusted by a method such as adjusting the tension of each roll of the bridle portions 4 and 5.

On the other hand, the final rolled material 10 to be treated (for example, a rolled Cu alloy material) is wound around a roll 6. The rolled material 10 is unwound from the roll 6, is wound between the rolls constituting the entrance bridle section 4, passes between the work rolls 1 of the tension leveler, and further rolls constituting the exit bridle section 5. After being wound around, it is taken up by a take-up roll 7.

In this embodiment, first, as a first tension leveler step, the elongation of the rolled material 10 is kept constant (for example, 0.25% or 0.3%), and the rolled material 10 is tensioned by a tension leveler. Through. In this case, the tension fluctuates (vibrates), but the average tension is, for example, 15 kgf / m.
and m ^2.

FIG. 3 shows the tension (unit tension) applied to the sheet material on the horizontal axis and the steepness on the vertical axis, and shows three types of sheet materials (A material, B material and C
FIG. 4 is a graph showing the relationship between unit tension and steepness of the material (material). The material A is a plate having a tensile strength about 1.5 times that of the material B, and the material C is a plate having a tensile strength of about 0.5 times that of the material B. As shown in FIG. 3, when the tension applied to the strip is increased, the steepness of the strip is reduced. When used as a lead frame, the steepness is set to 1% or less. Although the preferable range of the tension is different depending on the tensile strength of the sheet material, if the tension is too large, it is difficult to sufficiently reduce the residual stress in the second tension leveler step. For this reason, the tension applied to the strip material (rolled material 10) in the first tension leveler process is 9 to 25.
It is preferable to be about kgf / mm ² .

Next, as a second tension leveler step, the tension applied to the rolled material 10 is set to be 1/3 or less of the tension in the first tension leveler step, and the bridle parts 4, 5 are adjusted so that the tension is constant. Adjusted rolled material 1
Pass 0 through the tension leveler. In this case, it is preferable that the tension is set to 0 only in consideration of reducing the residual stress. However, when the tension is set to 0, a lateral flow of the rolled material 10 occurs in the tension leveler. For this reason, it is necessary to apply a minimum tension that does not cause lateral flow. Specifically, the tension in the second tension leveler step is preferably set to 3 to 8.3 kgf / mm ² .

As described above, by reducing the tension in the second tension leveler step to 1/3 or less of the tension in the first tension leveler step, the rolled material 1
The sum of the absolute value of the compressive stress and the absolute value of the tensile stress in the residual stress distribution in the thickness direction of 0 can be reduced.

FIG. 4 shows the relationship between the work roll diameter in the second tension leveler process on the horizontal axis and the sum of the absolute value of the compressive stress and the absolute value of the tensile stress on the vertical axis. FIG. However, the tension in the first tension leveler step was 15 kgf / mm ² , the diameter of the work roll was 16 mm, and the tension in the second tension leveler step was 4.5 kgf / mm ² .
In addition, the sum of the absolute value of the compressive stress and the absolute value of the tensile stress of the plate material subjected to only the first tension leveler process is about 2
It is 2 kgf / mm ² . From FIG. 4, the work roll diameter in the second tension leveler step is set to 16 m.
It can be seen that the sum of the absolute value of the compressive stress and the absolute value of the tensile stress can be set to 12 kgf / mm ² or less by setting the value to m or less.

FIG. 5 is a schematic diagram showing the residual stress distribution in the thickness direction in a cross section parallel to the rolling direction of the sheet material having undergone the first and second tension leveler processes. As shown in FIG. 5, the strip material 11 manufactured by the method of this embodiment has a small compressive stress and a low tensile stress. Also, usually, in a cross section orthogonal to the rolling direction,
Residual stress is smaller than a cross section parallel to the rolling direction.
In this manner, in the cross section parallel to the rolling direction and the cross section orthogonal to the rolling direction, the sum of the absolute value of the compressive stress and the absolute value of the tensile stress is set to 12 kgf / mm ² or less, thereby processing the lead frame. The deformation of the lead in the heat treatment step after processing into the lead frame can be suppressed.

Next, a strip material for a lead frame was actually manufactured by the method of the embodiment of the present invention, and the deformation of the lead of the lead frame formed from this strip material in the thickness direction and the width direction was examined. Will be described in comparison with a conventional example and a comparative example.

As a raw material, a Cu alloy (Cu-3.2 wt% Ni-0.7 wt% Si-1.25 wt% Sn-
A thin plate having a thickness of 0.127 mm was prepared. The thin plate was passed through a tension leveler twice in Examples 1 to 4 and Comparative Example 1 and once in Conventional Examples 1 and 2 while applying the tension shown in Table 1 below. In this case, the work roll diameter in the second tension leveler process of Example 4 is 12 mm, and the work roll diameter in the other tension leveler processes is 16 mm. In Conventional Example 2, low-temperature annealing (380 ° C. × 2 hours) was performed after passing through a tension leveler.

From the thin plate subjected to the straightening as described above,
A lead frame was formed. The lead arrangement pitch of this lead frame is 0.4 mm. Then, the distribution in the thickness direction of the residual stress remaining in the rolling direction (L) and the direction perpendicular to the rolling direction (width direction: C) is examined, and the sum of the absolute value of the compressive stress and the absolute value of the tensile stress is obtained. Was. That is, (L)
Is the residual stress in the cross section parallel to the rolling direction,
(C) is a residual stress in a cross section orthogonal to the rolling direction. The results are shown in the column of residual stress in Table 1. In addition, the amount of deformation of the lead in the thickness direction and the width direction of the lead was measured with a three-dimensional tool microscope. The results are also shown in Table 1.

[0029]

[Table 1]

As is clear from Table 1, the residual stress (the sum of the absolute value of the compressive stress and the absolute value of the tensile stress) in the cross section parallel to the rolling direction in both Comparative Example 1 and Conventional Examples 1 and 2 is shown. 14 kgf / mm ² or more, and the amount of deformation of the lead in the thickness direction of the lead is 23 μm, 60 μm and 37 μm, respectively, whereas in the embodiment of the present invention, the residual stress in the section parallel to the rolling direction and the section orthogonal to the rolling direction. Are 12 kgf / mm ² or less, and the amount of deformation in the thickness and width direction of the lead is as small as 17 μm or less. Thus, it is apparent that the present invention is extremely useful for producing a strip material for an electric / electronic component used for a lead frame.

In each of the above-mentioned Examples 1 to 4, the heat treatment step is not provided before and after the tension leveler step, but is performed before and / or after the tension leveler step.
Alternatively, a heat treatment step may be added later.

The plate material for electric and electronic parts according to the present invention is, of course, not limited to the above-described copper alloy. It can also be applied to alloys and the like. Further, the first and second tension leveler steps may be performed continuously by, for example, two tension levelers, or after the first tension leveler step is performed by one tension leveler, the tension may be reduced. After the adjustment, the second tension leveler step may be performed by the tension leveler.

[0033]

As described above, the strip material for an electric / electronic part according to the present invention has an absolute value of a compressive stress and a tensile stress in a residual stress distribution in a thickness direction in a cross section parallel to and perpendicular to a rolling direction. Is regulated to be equal to or less than a predetermined value, the deformation of the lead in the process of forming the lead frame and the heat treatment process after the process is small.

Further, in the method for producing a strip material for an electric / electronic part according to the present invention, the steepness of the strip material is set to 1% or less in the first tension leveler step, and the strip value is reduced in the second tension leveler step. Since the sum of the absolute value of the compressive stress and the absolute value of the tensile stress is less than or equal to a predetermined value in the residual stress distribution in the thickness direction in a cross section parallel to the rolling direction of the material and a cross section orthogonal to the cross section, the flatness is excellent. In addition, it is possible to obtain a plate material for electric and electronic parts in which the lead is less deformed in the step of processing into a lead frame and the heat treatment step after processing into the lead frame.

Further, according to another method of manufacturing a plate member for an electric / electronic component according to the present invention, the plate member is passed through a tension leveler in first and second tension leveler steps, respectively. Since the sheet is passed through the tension leveler at a low tension of 1/3 or less of the tension in the first tension leveler step, the flatness is excellent, the residual stress can be reduced, and the lead frame processing step and the heat treatment step after the processing are performed. It is possible to obtain a plate material for electric and electronic parts in which the deformation of the lead is extremely small.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a tension leveler used in a method of manufacturing a plate material for an electric / electronic component according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an arrangement of work rolls of a tension leveler.

FIG. 3 is a graph showing a relationship between a tension (unit tension) applied to a strip material and a steepness.

FIG. 4 is a graph showing a relationship between a diameter of a work roll and a residual stress in a second tension leveler step.

FIG. 5 is a view showing a residual stress distribution in a thickness direction in a cross section parallel to a rolling direction of a strip obtained through first and second tension leveler processes.

FIG. 6 is a perspective view showing a part of an IC.

FIG. 7 is a view showing a residual stress distribution in a thickness direction in a cross section parallel to a rolling direction of a conventional strip for electric and electronic parts.

FIG. 8 is a schematic diagram showing steepness.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Work roll 2,3; Intermediate roll 4,5; Bridle part 10; Rolled material 11; Plate material 13,15;

Claims (6)

(57) [Claims] 1. A plate or strip made of metal or alloy tape, a plate or a strip, wherein the absolute value of the compressive stress and the absolute value of the compressive stress in the thickness direction residual stress distribution in a cross section parallel to the rolling direction and a cross section orthogonal to the rolling direction, respectively. The sum with the absolute value of the tensile stress is 12 kgf
/ Mm ² or less. 2. The strip material for electric and electronic parts according to claim 1, wherein the metal or alloy is a Cu alloy. 3. A steepness obtained by passing a metal or alloy tape, plate or strip made of a metal or alloy through a tension leveler and dividing the height of the wavy strain by the pitch of the wave to 1.0% or less. A first tension leveler step, and passing the plate material after completion of the first tension leveler step through a tension leveler while maintaining a constant tension, in a thickness direction in a cross section parallel to the rolling direction and a cross section orthogonal to the rolling direction. A second tension leveler step for adjusting the sum of the absolute value of the compressive stress and the absolute value of the tensile stress in the residual stress distribution to 12 kgf / mm ² or less, respectively. Manufacturing method. 4. A first tension leveler step of passing a metal or alloy tape, plate or strip plate material through a tension leveler, and the plate material after completion of the first tension leveler step is subjected to the first tension leveler process. Through the tension leveler at a tension of 1/3 or less of the tension in the tension leveler process, the absolute value of the compressive stress and the absolute value of the tensile stress in the thickness direction residual stress distribution in a cross section parallel to the rolling direction and a cross section orthogonal to the rolling direction, respectively. A second tension leveler step of making the sum of the values equal to or less than 12 kgf / mm ² . 5. The method according to claim 3, wherein the work roll diameter of the tension leveler in the second tension leveler step is 16 mm or less. 6. The method according to claim 3, wherein the metal or alloy is a Cu alloy.