JPS6251246A - Lead frame - Google Patents

Abstract

PURPOSE:To prevent formation of a gap between an inner lead and a molded part when the lead is bent, by making the bending resistance of a part of an outer lead, which undergoes bending machining, smaller than the bending resistance of the other part of the outer lead. CONSTITUTION:A semiconductor pellet, which is mounted on a lead frame 1A, and the lead frame are wired. After molding, an outer lead 2A of the lead frame, which is extended from the molded part 7, is bent, and a semiconductor package 16A is obtained. The bending resistance of a part 10 of the outer lead 2A of the lead frame 1A, which is bent in this way, is made smaller than the bending resistance of the other part of the outer lead 12A. For example, the bending part of the outer lead 12A is locally annealed at a temperature 450 deg.C within the annealing region, and the annealed part 10 is obtained. The annealed part 10 is formed after the pattern blanking process and before the semiconductor-pellet mounting processes, by the projection of laser light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a lead frame for a semiconductor package, and in particular, to an IJ-fold V-frame that does not create a gap at the interface between the lead frame and the mold part during lead bending. - It is related to the system.

[Background of the invention]

First, an overview of the manufacturing method of conventional semiconductor packages,
The problem will be explained using drawings.

FIG. 8 is a manufacturing process diagram for explaining a conventional semiconductor package manufacturing method, and FIG. 9 is a partial plan view showing an example of the lead frame in FIG. 8.

10 is a partial perspective view showing the state after the molding process in FIG. 8, and FIG. 11 is a sectional view showing the state after the lead bending process in FIG. 8.

First, the thin metal sheet that is the lead frame material (for example,
2% Sn-copper alloy) is punched into a predetermined pattern using a V-strip (not shown) to obtain the lead frame 1 shown in FIG. In FIG. 9, the area surrounded by the two-dot chain line is the mold area that will be molded in the subsequent process. 4 is a tab, 3 is an internal lead, 2 is an external lead, and 5 is a dam.

On the other hand, a semiconductor pellet is manufactured from the semiconductor pellet material in a separate process, and this semiconductor pellet is mounted on the dove 4 of the lead frame 1 and bonded. The semiconductor bet V and the internal lead 3 are wired, and the mold area shown in FIG. 9 is molded using a semiconductor resin sealing mold (not shown), and the tab 4. The semiconductor pent on this tab 4.

Internal leads 3 are sealed in resin in mold part 7.

After the dam burr 6, which is the resin protruding from the semiconductor resin encapsulation mold, and the dam 5 of the lead frame 1 are removed, the external lead 2 is moved downward as shown in FIG. 11(a). Bending process (hereinafter referred to as lead bending process)
, a semiconductor package 16 is obtained.

By the way, during lead bending, the bending force is applied to the internal lead 3. The tensile stress is transmitted to the mold part 7, and a tensile stress acts on the interface between the resin of the mold part 7 and the upper surface of the internal lead 3, causing peeling, and as shown in detail in FIG. 11(b), the internal lead 3 There was a possibility that a gap 17 would be generated between the mold part 7 and the mold part 7. The dimensions of this gap 170 include a gap interval δ of approximately several μm to several tens of μm, and a depth of 1.5 μm. is approximately several 100 μm.

If such a gap 17 exists, moisture may enter there, causing internal corrosion and possibly causing failure.

As a countermeasure for this, the bending force during lead bending is reduced to 3. A method for preventing the transmission of the particles to the mold part 7 is known (for example, the method described in Japanese Patent Publication No. 49-491.07).

FIG. 12 is a sectional view of a main part illustrating a conventional means for preventing bending force during lead bending from being transmitted to the mold portion side.

In this FIG. 12, parts with the same numbers as in FIG. 11(b) are the same parts. This means
The part closest to the mold part 7 is restrained by an upper restraint jig 8 and a lower restraint jig 9.

By applying a bending force while applying a restraining force Pe from the vertical direction, the bending force is applied to the internal wire 3. This is designed to prevent it from being transmitted to the mold part 7.

However, in recent years, with the miniaturization of semiconductor packages,
It has become difficult to implement this method because there is no longer enough dimensional space to provide the upper and lower restraining jigs 8 and 9 having the width t2k necessary to prevent the transmission of the bending force.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lead frame for a semiconductor package that eliminates the problems of the prior art described above and does not create a gap at the interface between the internal lead and the mold part during lead bending. be.

[Summary of the invention]

The structure of the lead frame according to the present invention is such that the semiconductor pellet mounted on the lead frame and the IJ-form V-me are wired, and after this is molded, the lead frame V-me is exposed from the molded part to the outside. In the lead frame in which a semiconductor package is obtained by bending the external leads, the bending resistance of the part of the external lead to be bent is made smaller than the bending resistance of other parts of the external lead. .

More details are as follows.

The part of the external lead to be bent is locally annealed prior to the lead bending process to reduce the hardness of the lead frame, thereby reducing the bending force and localizing bending deformation. It was designed to do so.

In addition, the same can be achieved by creating a lead frame in which the plate thickness of the portion of the external lead to be bent is locally thinned prior to the lead bending process.

The bending force is reduced and one bending deformation is localized.

[Embodiments of the invention]

In the adhesive film of the present invention, prior to the lead bending process, the bending resistance of the part of the external lead to be bent, that is, the moment required for bending, is made smaller than that of other parts of the external lead. It is something.

The first means (means according to the first embodiment described in detail below) is to reduce the bending resistance of the part of the external lead by not annealing the part to be bent.
The means according to the second embodiment, which will be described in detail below, reduces the 1-bending resistance by reducing the plate thickness of the portion.

Examples will be described below.

FIG. 1 shows a lead frame according to a first embodiment of the present invention, FIG. 1(a) is a partial plan view, and FIG. 1(b) is a partial plan view of FIG. 1(a). 2 is an annealing temperature-hardness diagram of the material of the lead frame according to FIG. 1, and FIG. 3 is an enlarged sectional view taken in the direction of arrow I-1. FIG. 3 is an enlarged cross-sectional view of the main parts of the manufactured semiconductor package.

In each figure, the same parts are denoted by the same numbers as in FIGS. 9 and 11. Reference numeral 10 denotes an annealing part in which the parts of the two external leads to be bent are locally annealed at a temperature of 450C within the annealing region. This annealing part 1
0 was obtained by V-za irradiation after the pattern punching process and before the semiconductor sheet mounting process (details will be described later).

The material of this lead frame IA is a 2% Sn-copper alloy, and the relationship between its annealing temperature and Vickers hardness is as follows:
As shown in Figure 2, by annealing at 450C, the Vickers hardness of the lead frame material is 17.
5 to about 90. External lead 2 like this
By annealing the part to be bent by a person, the bending force during lead bending is reduced and the bending deformation is localized. is the eighth
As shown in detail in FIG. 3, there is no gap between the internal lead 3 and the molded part 7.

The annealing treatment by the V-za irradiation will be explained with reference to the drawings.

FIG. 4 is a schematic diagram showing a method of annealing the lead frame by V-za irradiation.

In FIG. 4, 14 is a V-zabeam, and 15 is a focusing V-lens. Place the lead frame on the table (not shown)
It is placed on one end side 10a'k of the portion of the two external leads to be bent, and positioned at the focal point of the V-the beam. Then, processing conditions such as heating temperature (450C) and moving speed of the table are set.

When the laser beam processing apparatus is turned on, the V-the beam 14 is irradiated onto the one end side 10a.

The table moves in the X direction at a set speed, and the outside.

Sequentially from the one end side 10a of the two leads to the other end side 450
heated to C. When this heating is completed, the laser beam processing device is turned off. The part irradiated with the laser beam is naturally cooled and annealed part 10. is obtained.

According to the first embodiment described above, the part of the external lead 2A to be bent is irradiated with V-za to annealing the part 10.
As a result, the bending force is reduced and the bending deformation is localized, causing the inner lead 3 and the mold part 7 to
This has the effect of not creating a gap at the interface with the There are still some unique advantages to having two external leads.

In this example, the annealed portion 10 is obtained by an annealing process using laser irradiation after the pattern punching process and before the semiconductor pellet mounting process.
It may be annealed at the collapse stage before the lead bending process. If the part of the external lead to be bent is annealed in the lead frame material state, the annealing process can be easily performed, resulting in the best production efficiency and lower lead frame V-frame costs. .

Furthermore, in this embodiment, the annealed portion 1 is heated by laser irradiation.
I tried to get 0, but local resistance heating occurred.

The external lead may be partially annealed to obtain the annealed portion 10 using methods such as heating element local contact heating.

Furthermore, in this example, the material of the lead frame is 2%
Although the case of a Sn-copper alloy has been described, the same effect can be obtained in the case of other materials, such as a 42-copper Ni-iron alloy, by completely annealing the portion of the external lead to be bent.

FIG. 5 shows a lead frame according to a second embodiment of the present invention, FIG. 5(a) is a partial plan view, and FIG. 5(1)) is a partial plan view of FIG. 5(a). An enlarged cross-sectional view taken along the V-V arrow,
FIG. 6 is an enlarged sectional view of a main part of a semiconductor package manufactured using the lead frame according to FIG. 5.

In each figure, the same numbers as in Figures 9 and 11 indicate the same parts. Reference numeral 11 denotes a recess formed on the side 2a of the bending portion of the external lead 2B, which is the outer periphery of the bend, and the plate thickness of the recess 11 is 1. is thinner than the plate thickness to of other parts.

The recess 11 is formed by punching after the pattern punching process and before the semiconductor sheet mounting process (details will be described later).

By making the bent portion of the external lead 2B thinner in this way, the bending force during the lead bending process is reduced and bending deformation is localized, so the semiconductor package manufactured using this lead frame IB is 16B
As shown in detail in FIG. 6, no gap is generated between the internal lead 3 and the molded part 7.

A specific example will be shown.

Since the bending force is approximately proportional to the square of the plate thickness, the bending force can be significantly reduced by reducing the plate thickness of the portion to be bent. The stress generated in the internal lead 3 and the mold part 7 decreases in proportion to the bending force. By making the plate thickness t1 of the recess 11 30% thinner than the plate thickness to of other parts, the bending force is reduced to less than half.

The method of forming the four parts 11 by pressing with the punch will be explained with reference to the drawings.

FIG. 7 is a schematic diagram illustrating a method of forming a recess in the lead frame 6 by pressing with a punch.

In this FIG. 7, 12 indicates an external lead 2 at the tip.
Convex-shaped convex portions 128 that match the four portions 11 to be formed in B
The punches 13 included in the punches 13 are flat-topped dies, and the punches 12. Prepare die 13. The die 13 is placed and fixed on the bed of a press (not shown), and the punch 12 is
, die .

13 and is attached to the ram of the above-mentioned pump. The portion of each external lead 2B to be bent is the convex portion 12 of the punch 12.
The lead frame is set on the die 13 so that it is located directly under the lead frame a.

At this point, when the above-mentioned switch is turned on, each punch 12 is pushed into the external lead 2B, and the plurality of external leads 2B are pressed.
The desired four parts 11 are formed simultaneously. To give an example of specific dimensions, the plate thickness of the external lead 2B is to=o, 20 holes,
Plate thickness t1 of recess 11 - 0.15 mm, width 13 of recess 11
=0.20mm.

According to the second embodiment described above, the external IJ-board 2B
A concave portion 11f is formed on the outer periphery of the bent portion 2a of the bent portion 11! : Since the lead is formed to be thinner, the bending force is reduced and there is an effect that no gap is created at the interface between the internal lead 3 and the molded part 7. Further, as explained with reference to FIG. 7, since the processing equipment used to form the recesses 11 is simple and inexpensive, this embodiment has the unique advantage that the cost of forming the recesses is low.

Note that in this embodiment, the recess 11 is formed on the side 2 that is the outer circumference of the bend.
Although it is formed on the side 2b which is the inner circumference of the bend, the same effect can be obtained.

It is more advantageous in terms of strength to form the recess 11 on the side 2a that is the outer periphery of the bend.

Further, in this embodiment, the recesses 11 are formed after the pattern punching process and before the semiconductor pellet mounting process, but they may be formed at any stage before the lead bending process. .

Since the recesses formed in the bent portions of the external leads are formed in the lead frame material by rolling, the production efficiency for forming the recesses is the highest and the cost of the lead frame is reduced.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide an IJ-frame for a semiconductor package that does not create a gap at the interface between the internal lead and the mold part during lead bending.

[Brief explanation of the drawing]

FIG. 1 shows a lead frame according to a first embodiment of the present invention, FIG. 1(a) is a partial plan view, and FIG. 1(b) is a partial plan view of FIG. 1(a). 2 is an annealing temperature-hardness diagram of the material of the lead frame shown in FIG. FIG. 4 is a schematic diagram showing a method of annealing the lead frame by V-za irradiation, and FIG. 5(a) is a partial plan view, FIG. 5(b) is an enlarged sectional view taken along the line V-V in FIG. 5(a), and FIG. 6 is a partial plan view of the lead frame. FIG. 5 is an enlarged cross-sectional view of a main part of a semiconductor package manufactured using the re-doped frame, and FIG. 7 is a schematic diagram showing a method of forming four parts of the lead frame by punching. FIG. 8 is a manufacturing process diagram illustrating a conventional semiconductor package manufacturing method, FIG. 9 is a partial plan view showing an example of the lead frame in FIG. 8, and FIG. Partial perspective view showing the state after the process, 1st
Figure 1 shows the lead in Figure 8, 2a... the side that becomes the outer periphery of bending, 7... the mold part, 10... the annealing part,
11... recess, 16A. 16B...Semiconductor package.

Claims (1)

[Claims] 1. After wiring a semiconductor pellet mounted on a lead frame and the lead frame and molding the same,
In the lead frame in which a semiconductor package is obtained by bending the external leads of the lead frame that have come out from the mold, the bending resistance of the bent portion of the external lead is determined by the bending resistance of the external lead. A lead frame characterized by having a bending resistance smaller than that of its parts. 2. By annealing the part of the external lead to be bent, the bending resistance of the part to be bent can be reduced.
The lead frame according to claim 1, wherein the bending resistance of the other parts of the external lead is smaller than that of other parts of the external lead. 3. The lead frame according to claim 2, wherein the portion of the external lead to be bent is annealed before mounting the semiconductor pellet. 4. By making the plate thickness of the part of the external lead to be bent thinner than other parts, the bending resistance of the part to be bent is made smaller than that of other parts of the external lead. A lead frame according to claim 1. 5. A concave portion is formed on the outer periphery side of the bending portion of the external lead, so that the thickness of the bending portion is made thinner than the other portion.
Lead frame as described in section. 6. The lead frame according to claim 4, wherein the thickness of the portion of the external lead to be bent is made thinner before the semiconductor pellet is mounted.