JP3047689B2 - Lead frame downset processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for downsetting a lead frame.

[0002]

2. Description of the Related Art Memory ICs are increasing in density and capacity year by year, and the demand for reliability is rapidly increasing. In recent DRAMs, in order to meet this demand, and from the viewpoint of mounting high density and high speed operation, the package structure is COL (Chip On Lead) and LOC (Lead On Chip).
It has attracted attention to adopt.

FIG. 5 shows an example of an assembling process of the LOC package, in which etching (a), plating (b), downset (c), film bonding (d), die bonding (e), and wire bonding are performed. (F), a process such as mold cutting and molding (g).

Incidentally, in such an assembling process, the downset step (c) is to form the downset portion 2 bent into the lead frame 1 as shown in FIG.

[0005] The downset method conventionally performed is as follows.
Downset processing is performed by cold working with a mold. That is, as shown in FIG. 4, the lead frame 1 is placed on the die 4, and the plastic working is performed by the punch 5 while the periphery of the downset processing surface is pressed by the stripper 3 (FIG. 4A). (FIG. 4B) In the processing control, the amount of crushing of the processing surface is controlled by the bottom dead center control of the punch 5 by the high stopper, and the shape and the depth are finely adjusted.

[0006]

However, the prior art has the following problems.

(1) Since the shape control is controlled by the amount of crushing by the mold, there is a difficulty in the initial setting of the mold, and the residual strain after processing is large.

(2) If the lead shape is not uniform, the downset shape is not uniform for each lead.

(3) When the downset is deep, the bonding coordinates at the tip of the lead are drawn toward the bending side, so that it is necessary to correct the production pattern at the time of etching or pressing.

(4) When the downset depth is almost twice or more the material thickness, it is difficult to perform the downset once or at one place.

(5) When bending at a plurality of locations, simultaneous processing is difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of downsetting a lead frame which can solve the above-mentioned disadvantages of the prior art and can obtain a stable downset shape.

[0013]

According to a first aspect of the present invention, there is provided a method for downsetting a lead frame, comprising: two sets of electrodes for supporting both ends of a downset processed portion of a lead frame at four points. The pair is clamped, and a current is applied between the two pairs of electrodes to heat the downset processed portion of the lead frame to soften the material of the portion, and in this state, the two sets of clamped portions are clamped. One of the electrode pairs is fixed, and the other
By moving the lead frame downward, a displacement of the downset processing is relatively given to the lead frame .

In a second aspect of the present invention, there is provided a lead frame downset processing method in which a plurality of downset processing portions are provided, and both ends of each downset processing portion are provided with a plurality of sets of corresponding electrodes. It clamps with a pair, energizes between each electrode pair corresponding to both ends of each downset processed part, heats each downset processed part of the lead frame, softens the material of the part, and in this state, Of the electrode pairs at both ends that clamp the processed part, the outer lead side of the lead frame
Fix the two electrode pairs that are positioned and
The two electrode pairs located on the side of the
By moving at times, it is intended to relatively impart a displacement of downset processing to the lead frame .

[0015]

According to the first invention, both ends of the downset processed portion of the lead frame are clamped by two pairs of electrodes. The electrode pair for clamping the lead frame is designed so that one electrode pair can be moved relative to another electrode pair in the processing direction. The simplest and cheapest way to keep the electrode pairs relatively movable is to keep one set stationary and the other movable.

When a voltage is applied between the two pairs of electrodes and energized, only the downset processed portion of the lead frame is heated, and the material in this portion is softened. In this softened state, when the two electrode pairs clamping both ends of the portion to be processed are relatively moved to give a displacement of the downset process, the portion is downset processed.

According to this, the residual strain after the working is reduced because of the hot working by the electric heating, and the shape is easily controlled because the working is performed at the time of softening at a high temperature. Therefore, there are no difficulties in the initial setting as in the case of using a mold, and the downset shapes are not uniform for each lead when the lead shape is uneven.

In addition, since the softened portion to be processed is elongated by the displacement of the electrode pair, it is possible to perform a simultaneous deep bending according to the displacement amount regardless of the material thickness. Therefore, even when the downset depth is twice or more the material thickness, it is easy to perform the downset once or at one place.

In addition, since local heating is performed to heat only the downset processed portion, there is little influence such as deformation to portions other than the processed portion. In addition, the lead-up and lead-down are both performed in any direction regardless of the direction in which the lead is relatively displaced during downset processing. Even if the downset is deep, the bonding coordinates at the tip of the lead are not drawn into the bending side, so that the bonding coordinate shift is very small, and there is no need to correct the production pattern at the time of etching or pressing.

According to the second aspect of the present invention, a plurality of downset portions to be processed in the lead frame are clamped by electrode pairs, and the downset is simultaneously performed by energizing and heating. Batch bending becomes possible.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows a first downsetting method of the present invention.
It shows an example.

The downset processed portion 2 of the lead frame 1 is clamped by two pairs of electrodes 6, 6, 7 and 7.
The two electrode pairs 6,6 and 7,7 are such that one of the electrode pairs 6,6 is fixed and the other electrode pair 7,7 is movable in the thickness direction of the lead frame 1. Has become.

After clamping both ends of the downset processed portion 2 of the lead frame 1 between the electrode pairs 6 and 6 and between the electrode pairs 7 and 7, the voltage of the power source 8 is applied between the electrode pairs 6 and 7. Then, power is supplied to the downset processed portion 2 (FIG. 1A).

By this energization, the part 2 to be processed is set down.
Of the lead frame material is softened by heating. Simultaneously with the start of the softening, the movable electrode pair 7 is displaced by a predetermined downset depth with respect to the fixed electrode pair 6 while holding the clamp of the lead frame 1, and then the energization is stopped.
Waiting for the hardened portion to be processed, the downset process is completed (FIG. 1B).

Since the portion to be processed becomes hot and oxidizes, it is preferable to perform the processing in an atmosphere of an inert gas such as N ₂ or Ar.

According to the method according to the above-described embodiment, since the hot downsetting is carried out by the application of electric current, the residual distortion after the working can be reduced, and the shape can be easily controlled since the working is performed at the time of softening at a high temperature. It is. In addition, since the processing is performed by displacing the electrode pair, batch deep bending can be performed according to the displacement amount, and local heating is performed between the electrode pairs, so that there is little influence such as deformation to a portion other than the portion to be processed. Furthermore, since the displacement of the electrode pair is a relative displacement, lead up, lead down,
In any case, the processing direction is irrelevant. Even if the downset is deep, the bonding coordinates are not drawn to the bending processing side, so that the displacement of the bonding coordinates is minute.

FIG. 2 shows an application example that makes use of the advantages of electric heating. That is, a second embodiment that enables simultaneous downset processing at two locations is shown. Two fixed electrode pairs 6, 6 and 6, which clamp the lead frame 1
6 are disposed at both outer ends of the two downset processed parts 2, 2, and the downset processed parts 2, 2 located between the two fixed electrode pairs 6, 6, 6, 6. The movable electrode pairs 7, 7 are provided at both inner ends.

As shown, the movable electrode pairs 7, 7 are formed longer in the width direction (lead direction of the lead frame) than the fixed electrode pairs 6. Both ends protrude into a clamp portion, and two portions of the lead frame 1 can be clamped at the same time by the clamp portion, but an intermediate portion is recessed so as not to be in contact with the lead frame 1. The movable electrode pairs 7, 7 can be moved up and down with respect to the fixed electrode pairs 6, 6.

With the two fixed electrode pairs 6, 6 and the movable electrode pairs 7, 7 clamping the respective downset processed parts 2, 2 of the lead frame 1, the movable electrode pairs 7, 7 are simultaneously clamped.
And a power supply 8 between the two fixed electrode pairs 6 and 6 on both sides.
Is applied. Then, power is supplied to the two portions 2 and 2 to be processed, whereby the corresponding two portions of the lead frame are heated and the material is softened. In this state, the displacement of the downset processing is applied to the movable electrode pairs 7, 7, and the downset processing portions 2, 2 are simultaneously subjected to the downset processing.

Thus, downset processing can be performed on the two fixed electrode pairs 6, 6 and 6, 6 on both sides by a pair of movable electrode pairs 7, 7 and a single action thereof.

[0031]

(1) According to the lead frame downset processing method according to the first aspect, the downset processing portion is clamped by the electrode, and is hot stretched by electric heating.
Because performs a down-set processing by, residual strain after processing can be effectively reduced, and little influence of deformation of the other workpiece part for local heating, stable down set shape is obtained.

(2) According to the lead frame downset processing method according to the second aspect, in addition to the above effects, a plurality of locations can be further processed at once.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of a lead frame downset processing method according to the present invention.

FIG. 2 shows a second embodiment of the method of the present invention.

FIG. 3 is a view showing a downset shape of a general lead frame.

FIG. 4 is a view showing a conventional lead frame downset processing method.

FIG. 5 is a diagram illustrating a conventional LOC package assembling process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lead frame 2 Downset processed part 6 Fixed electrode pair 7 Movable electrode pair 8 Power supply

──────────────────────────────────────────────────の Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 23/50

Claims (2)

(57) [Claims] 1. A downset processed portion of a lead frame is clamped by two pairs of electrodes supporting both ends of a downset processed portion of a lead frame at four points, and a current is applied between the two pairs of electrodes. By heating, the material of the part is softened, and in this state , one of the two electrode pairs that clamps the processed part is fixed, and the other electrode pair is fixed.
By moving the electrode pair up and down, the lead frame
A method of downsetting a lead frame, wherein a displacement of downsetting is relatively given to a system. 2. There are a plurality of downset processed portions of a lead frame, and both ends of each downset processed portion are clamped by a plurality of corresponding electrode pairs to correspond to both ends of each downset processed portion. Heat is applied to each downset processed part of the lead frame by applying a current between each pair of electrodes to soften the material of the part, and in this state, of the electrode pairs at both ends clamping each processed part in this state , Re
The two sets of power cables located on the outer lead side of the lead frame
Fix the pole pair and attach it to the inner lead side of the lead frame.
The two pairs of electrodes that are located must be movable vertically.
Wherein the lead frame is relatively displaced by down-set processing.