JPH07176671A - Lead frame and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an inexpensive lead frame being employed in an IC and manufacturing method thereof. CONSTITUTION:When a long lead frame 11 is formed by press, for example, the parts to be punched are distributed uniformly in terms of quantity and position on the surface and rear of a thin metal plate 12. The thin metal plate 12 is then punched on the surface (blank part) and on the rear (hatched part) according to the distribution thus forming a lead frame 13 for a plurality of elements and a large number of openings 14. Since the long lead frame 11 is formed by punching the thin metal plate 12 from the opposite sides, the thin metal plate 12 is prevented from warping at the time of pressing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame used in, for example, a semiconductor device and a method of manufacturing the same, and particularly to a multi-pin IC (Integrated C).
It is used for ircuit) and the like.

[0002]

2. Description of the Related Art Conventionally, a lead frame formed by pressing has a predetermined shape and size by combining a plurality of punching processes.

FIG. 4 schematically shows a long lead frame formed by press working. This long lead frame 1 has a structure in which a lead metal frame 3 for a plurality of elements and a large number of openings 4 for positioning are formed by punching a horizontally elongated metal thin plate 2 by press working, for example. ing.

In this case, each of the lead frames 3
That is, the lead frame 3 for one element includes a chip mounting portion 3a on which a semiconductor chip (not shown) is mounted,
It is composed of a plurality of lead terminals 3b electrically connected to the electrodes of the semiconductor chip mounted on the chip mounting portion 3a.

By thus forming the lead frames 3 for a plurality of elements on the thin metal plate 2 by pressing,
A plurality of ICs can be obtained from one long lead frame 1.

However, the conventional elongated lead frame 1 is generally formed by punching in one direction from the front surface to the back surface of the metal thin plate 2 or from the back surface to the front surface. For this reason, the elongated lead frame 1 is not entirely flat in both the long-side direction and the short-side direction of the metal thin plate 2, so that a deformation having a curved surface is likely to occur.

For example, as shown in the drawing, when the elongated lead frame 1 is formed with the punching direction at the time of punching as the arrow direction, in the long side direction, the concave shape is formed so that the sagging surface side of the thin metal plate 2 in each punching direction shrinks. To a convex shape so that the burr surface side of the metal thin plate 2 opposite to the drawing direction extends (hereinafter, this deformation in the long side direction is referred to as warp in the length direction).

Similarly, in the short-side direction, the sagging surface side of the thin metal plate 2 in the pulling direction is deformed into a concave shape so as to shrink, and the burr surface side of the thin metal plate 2 opposite to the pulling direction is deformed into a convex shape ( Hereinafter, this deformation in the short side direction is referred to as a warp in the width direction).

The cause of the above-mentioned warpage will now be described. FIG. 5 shows an outline of a process in punching with a press die.

First, the thin metal plate 2 is transferred by a transfer means (not shown), and the die 101 of the press die 100 is pressed.
It is set at a predetermined position above ((a) in the same figure). In this state, the upper die 102 of the press die 100 is gradually lowered by a press machine (not shown), so that the metal thin plate 2 is pressed and fixed to the die 101 by the stopper 104 having the spring 103. It

Then, when the upper die 102 is further lowered, the punch 105 fixed to the upper die 102 is lowered, and the punching process of the metal thin plate 2 fixed on the die 101 is started (see FIG. (B)).

In this way, the upper die 102 continues to descend until the punch 105 penetrates the thin metal plate 2, and the punching process is completed when the punch 105 penetrates (FIG. 3C).

By combining a plurality of punching processes as described above, that is, by sequentially feeding and feeding the thin metal plate 2 to a plurality of press dies 100 to which punches having different shapes are attached, the elongated shape shown in FIG. Lead frame 1 is formed.

Now, in the above punching process,
For example, as shown in FIG. 6, immediately after the punching process of the punch 105 on the metal thin plate 2 is started, the metal thin plate 2 is pressed.
A great deal of force will be applied to.

The force applied at the start of the punching process causes the largest deformation, and in particular, in the case of the long lead frame 1 formed by a combination of a plurality of punching processes from one direction of the thin metal plate 2, each of the lead frames 1 has a different shape. Deformation during processing gradually overlaps and finally appears as a warp in the length direction and a warp in the width direction.

As described above, as long as it is formed by a plurality of punching processes from one direction, the warp in the length direction and the warp in the width direction are inevitable. However, such a warp in the length direction and a warp in the width direction cause a problem of ups and downs of the lead terminals 3b (see FIG. 4). Therefore, in this state, the long lead frame 1 is mounted on the semiconductor of the subsequent stage. Cannot be put into the assembly process.

In the long lead frame 1, the amount of warp is usually a plate thickness × 0.3 to a plate thickness × 4 m due to the warp in the length direction.
Strict management such as about m, and about 0.05 mm to 0.3 mm in width direction warp is required.

As a method of correcting these warps, conventionally, for example, a device called a leveler 200 as shown in FIG. 7 is used to correct the warpage of the elongated lead frame 1.

In the leveler 200, the warped long lead frame 1 is flattened by passing the long lead frame 1 between a plurality of rollers 200a arranged vertically in two steps by shifting by half pitch. It is about to be transformed.

However, in the case of this method, the warp in the length direction of the elongated lead frame 1 can be corrected,
Of the outer dimensions, the dimension in the lateral direction is absolutely small (for example, the dimension in the longitudinal direction is 100 to 250 mm, whereas the dimension in the lateral direction is short, 10 to 60 mm).
Therefore, the leveler 200 does not correct the widthwise warp.

Therefore, a method of flattening the long lead frame 1 is used by using a method of correcting the warp in the width direction with a bending mold or a coining mold.

FIG. 8 shows a method for correcting the warp in the width direction of the elongated lead frame 1 using the bending mold 300. In this method, a long lead frame 1 having a warp in the width direction is sandwiched between a punch 300a and a die 300b having a shape opposite to the warp direction, so that the long lead frame 1 is warped. Bending is performed on the opposite side to forcibly flatten the widthwise warp.

FIG. 9 shows the use of a coining mold 400.
1 shows a method of correcting a warp in the width direction of a long lead frame 1. In this method, a long lead frame 1 having a warp in the width direction is sandwiched between a punch 400a having a square protrusion and a flat die 400b (FIG. 10A), or a triangular protrusion is formed. It is sandwiched between the punch 400c and the flat die 400b (FIG. 2 (b)), coined on the sag surface (concave) side of the elongated lead frame 1 and extended from the burr surface (convex) side. Thus, the warp in the width direction is forcibly flattened.

However, the long lead frame 1
In the case of the method of correcting the warp in the length direction of the same using the leveler 200, an expensive device (leveler 200) is required,
Also, since the correction processing cost is added, there is a drawback that the long lead frame 1 becomes expensive accordingly.

Further, the warp in the width direction of the elongated lead frame 1 is bent by a bending mold 300 or a coining mold 400.
In the case of the method of straightening using
Is required, and the correction processing cost is added, the long lead frame 1 becomes expensive and has the same drawback as described above, and is used for the long lead frame 1. Depending on the strength of the thin metal plate 2 to be formed and the wear state of the molds 300 and 400, it is extremely difficult to adjust the degree of correction for different warp amounts.

Further, in the case of the correction method using the coining mold 400, the traces remain on the long lead frame 1, so that not only the appearance defect but also the dimensional change may occur. There was a drawback that the correction could only be performed within a limited range and amount.

[0027]

As described above, in the prior art, the warp of the long lead frame 1 caused by press punching is corrected by the leveler 200 for the warp in the longitudinal direction. Since the direction warpage is corrected by using the bending mold 300 and the coining mold 400, there is a problem that the obtained long lead frame 1 becomes expensive.

Therefore, an object of the present invention is to provide a lead frame capable of eliminating the warp correction in the lead frame and supplying a cheaper lead frame, and a manufacturing method thereof.

[0029]

In order to achieve the above object, in a lead frame of the present invention, a chip mounting portion for mounting a semiconductor chip on a thin metal plate and a chip mounting portion mounted on this chip mounting portion are mounted. A lead terminal for electrically connecting to an electrode of a semiconductor chip, the chip mounting portion and the lead terminal are formed from a first direction and a second direction with respect to the thin metal plate. It is formed by pressing.

In the lead frame manufacturing method of the present invention, the chip mounting portion on which the semiconductor chip is mounted and the electrode of the semiconductor chip mounted on the chip mounting portion are electrically mounted on the thin metal plate. A first press working step of punching the metal thin plate from a first direction to a second direction to form a lead terminal to be connected, and the chip mounting portion and the metal thin plate on the metal thin plate. It comprises a second pressing step for punching the thin metal plate from the second direction to the first direction to form the lead terminal.

[0031]

According to the present invention, since the warp in the lead frame due to the press working can be suppressed as much as possible by the above means, the cost for correcting the warp can be made unnecessary. Is.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic structure of a lead frame according to the present invention. This elongated lead frame 11 is formed by punching a thin metal plate 12 by a first press working from the front surface to the back surface and a second press working from the back surface to the front surface, respectively. The lead frame 13 and a large number of openings 14 for positioning are formed.

In this case, the lead frame 13 for a plurality of elements and the large number of holes 14 in the elongated lead frame 11 are appropriately formed by the metal thin plate 12 during press working.
By switching the punching direction when punching, for example by reversing the front and back of the metal thin plate 12 and supplying it to a plurality of press dies (not shown), each is formed at a predetermined position and with a predetermined shape and size. It is supposed to be done.

That is, a portion selectively formed by punching from the front surface to the back surface of the metal thin plate 12 (in the figure,
(A portion indicated by white space) and a portion selectively formed by punching from the back surface to the front surface of the metal thin plate 12 (a portion indicated by diagonal lines in the drawing), the lead frame 13 for a plurality of elements and a large number of openings. Holes 14 are formed on the thin metal plate 12, respectively, and the long lead frame 1 is formed.
1 is formed.

The details of the manufacturing method for forming the elongated lead frame 11 by pressing will be described later. Here, as the metal thin plate 12,
For example, 42 alloy (42% Ni—Fe alloy) is used as the material, and the outer dimension thereof is 167.
4mm, short side dimension is 50mm, board thickness is 0.15m
It has become m.

Each of the lead frames 13, that is, one element of the lead frame 13, has a chip mounting portion 13 on which, for example, a semiconductor chip (not shown) is mounted.
a and a plurality of lead terminals 13 electrically connected to the electrodes of the semiconductor chip mounted on the chip mounting portion 13a
It consists of b and.

The lead frame 13 for one element having such a structure is formed for each frame 11, for example, for 4 to 64 elements. Next, a method for manufacturing the long lead frame 11 described above will be described.

FIG. 2 shows an outline of a manufacturing process when the long lead frame 11 is formed by press working. In this press working step, a die (not shown) similar to the press die 100 shown in FIG. 5 is used, and the punching process is performed by this press die.

For example, the thin metal plate 12 is conveyed by a conveying means (not shown) or the like, and first, with its surface facing upward, it is set at a predetermined position of the first press die. Then, punching of the thin metal plate 12 is started by the punch fixed to the press die.

As a result, for example, as shown in FIG. 2A, by punching a white portion from the front surface to the back surface of the thin metal plate 12, the chip mounting portion 13a and the lead terminal 13b of the lead frame 13 for each element are punched. And a part of the large number of openings 14 are formed.

After that, the metal thin plate 12, which has been punched from the front surface to the back surface, is again conveyed by a conveying means (not shown) or the like. Set to position.

Then, the punching process of the metal thin plate 12 is started by the punch fixed to the press die. As a result, as shown in FIG. 2B, for example, a portion of the lead terminal 13b of the lead frame 13 for each element and a large number of holes are formed by punching out the hatched portion from the back surface to the front surface of the metal thin plate 12. A part of 14 is formed.

By performing the punching from the front surface to the back surface of the metal thin plate 12 and the punching from the back surface to the front surface in this way, for example, as shown in FIG. A lead frame 13 for elements and a large number of openings 14 are formed,
A long lead frame 11 is formed.

In this case, the punching from the front surface to the back surface of the metal thin plate 12 and the punching from the back surface to the front surface are performed so that the portions formed by the respective punchings do not concentrate locally (specific locations). For example, a thin metal plate 1
This is performed based on empirical rules and experimental rules in consideration of the characteristics (2) (plate thickness, hardness, etc.) or the number and size of lead frames 13 for each element (the number of pins of the lead terminal 13b).

That is, by punching from the front surface to the back surface of the metal thin plate 12 and from the back surface to the front surface,
To prevent warping of the long lead frame 11,
This press working is performed so that the portions formed by punching from each direction maintain a quantitative and positional balance.

Therefore, the long lead frame 11
It is possible to suppress the warpage that occurs in the frame as much as possible, and it becomes possible to easily supply the flat frame 11 without the need to correct the warp.

In the pressing step, the punching from the front surface to the back surface of the metal thin plate 12 and the punching from the back surface to the front surface are not performed by one pressing work, but the portions to be punched from each direction are punched. When the lead frame 13 and the large number of openings 14 for a plurality of elements are finally formed by dividing into a plurality of pieces and combining a plurality of punching processes in each direction, the flatness is higher. That is, it is possible to form the elongated lead frame 11 with extremely small warpage.

FIG. 3 shows a long lead frame 11 (bidirectional processed product) formed by the above method and an equivalent product (unidirectional processed product) formed by punching from one direction in the related art. The amount of warpage is compared and shown.

As is clear from this figure, the metal thin plate 1
By performing press working from both the front side to back side punching and the back side to front side punching, both lengthwise and widthwise warping are so flat that warping correction is unnecessary. It is possible to form the long lead frame 11 having a high degree of flexibility.

As described above, the occurrence of warpage in the lead frame due to press working can be suppressed as much as possible. That is, the parts to be punched are distributed on both the front surface and the back surface of the thin metal plate without being quantitatively and positionally offset, and according to the distribution, the punching from the front surface to the back surface and the back surface to the front surface of the thin metal plate are performed. By doing so, a long lead frame is formed. As a result, punching from one direction can be prevented from concentrating on a specific location, so that the forces applied to the respective surfaces of the thin metal plate during press working can be made substantially equal, and the amount of warpage that occurs can be kept small. It becomes possible. Therefore, the cost for correcting the warp can be eliminated, and an inexpensive lead frame can be provided accordingly.

In particular, the number of pins I is increased because the number of press dies is increased (the number of punches is increased) and the pitch of lead terminals is narrowed.
This is useful when forming a lead frame or the like used for C. The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the invention.

[0052]

As described above in detail, according to the present invention, it is not necessary to correct the warp in the lead frame,
It is possible to provide a lead frame capable of supplying a cheaper lead frame and a manufacturing method thereof.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a lead frame according to an embodiment of the present invention.

FIG. 2 is a diagram which is also shown for explaining a method of manufacturing a lead frame.

FIG. 3 is a diagram showing the amounts of warpage of the lead frame formed by the method of the present invention and the lead frame formed by the conventional method in comparison.

FIG. 4 is a configuration diagram of a lead frame shown for explaining a conventional technique and its problems.

FIG. 5 is a diagram similarly shown for explaining the method for manufacturing the lead frame.

FIG. 6 is a diagram similarly shown for explaining the cause of the warp of the lead frame.

FIG. 7 is a diagram for explaining a method of correcting warp in the length direction of the lead frame by using a leveler.

FIG. 8 is a diagram similarly shown for explaining a method of correcting the widthwise warp of the lead frame by using a bending mold.

FIG. 9 is a diagram for explaining a method of correcting the widthwise warp of the lead frame using the coining mold.

[Explanation of symbols]

11 ... long lead frame, 12 ... metal thin plate, 13
... lead frame for each element, 13a ... chip mounting part,
13b ... Lead terminal, 14 ... Open hole.

Claims (3)

[Claims] 1. A lead frame comprising a thin metal plate on which a chip mounting portion for mounting a semiconductor chip and lead terminals for electrically connecting to electrodes of a semiconductor chip mounted on the chip mounting portion are formed. In the lead frame, the chip mounting portion and the lead terminal are formed by pressing the metal thin plate from the first direction and the second direction. 2. A chip mounting portion on which a semiconductor chip is mounted and a lead terminal to which electrodes of a semiconductor chip mounted on the chip mounting portion are electrically connected are formed on a thin metal plate. A first pressing step of punching the metal thin plate from a first direction to a second direction; and a first pressing process of the metal thin plate for forming the chip mounting portion and the lead terminal on the metal thin plate. 2. A method of manufacturing a lead frame, comprising: a second press working step of punching from the direction 2 to the first direction. 3. The first and second press working steps are each performed by combining a plurality of punching processes,
The method of manufacturing a lead frame according to claim 2, wherein the chip mounting portion and the lead terminal are formed.