JPS63205938A - Formation of semiconductor lead - Google Patents

Abstract

PURPOSE:To prevent a gap from being produced between a lead and a resin after a bending process by a method wherein an inner lead is made thick before the lead is bent. CONSTITUTION:The following two parts are provided: a lower mold 12 where a groove is made at a part corresponding to a resin part and which supports a lead without coming in contact with the resin part; an upper mold 13, where another groove comes in contact with only the lead part. A semiconductor 7 is installed between the lower mold 12 and the upper mold 13 after a cutting process; then, a compression load is exerted on an external lead 2 by driving a press; the lead 2 is pressed down. By this process, an internal lead 3 is protruded by a height (d) due to the flow of a material and its thickness is increased. After that, the lead 2 is bent by using a bending roller. By this setup, a gap is not produced between the lead part 3 buried inside the semiconductor 7 and the resin part after a bending process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead molding method for resin-molded semiconductors.

[Conventional technology]

An overview of a conventional semiconductor package manufacturing method and a semiconductor lead bending method in the semiconductor package manufacturing process will be explained with reference to FIGS. 2 to 6.

Figure 2 is a diagram showing the manufacturing process of a semiconductor package, and Figure 3 is a plan view of a lead frame punched out with a pattern in the initial manufacturing process of the semiconductor package. As shown in , a lead frame material (for example, a thin metal plate of 2To8n-Cu alloy) is punched into a predetermined pattern using a press.
Obtain IJ-)' frame 1 as shown in the figure. The lead frame 1 has external leads 2. Internal lead 3. Tab 4. The area consisting of the dam 5 and surrounded by the two-dot chain line in FIG. 6 is the mold area to be molded in a subsequent process. Then, before the molding process, a semiconductor pellet (not shown) manufactured in a separate process is mounted on the tab 4 of the lead frame 1 and adhered.
The semiconductor pellet and the internal lead 3 are connected, and then the mold area of the lead frame 1 is molded using a molding fitting for semiconductor resin and soil. FIG. 4 is a perspective view showing the state after the molding process, and as shown in the figure, the semiconductor pellet on the tab 4 and the internal lead 3 are sealed in the mold part 7 with the molding resin. Then, after cutting out the dam burr 6 of the mold resin protruding from the casting fitting for semiconductor resin encapsulation and the dam of the lead frame 1, the external lead 2 is bent downward, and through the above manufacturing process,
A semiconductor package 8 as shown in the cross-sectional view of the semiconductor package in FIG. 5 (al) is obtained.

By the way, during such lead bending process, if the bending process is performed without mechanically restraining the external lead 2, the bending force will be transmitted to the internal lead 3 and the mold '@7.
As a result, as shown in FIG. 5(b), tensile stress acts on the interface between the mold part 7 and the upper surface of the internal lead 3, causing peeling, and as a result, a gap 9 is created between the internal lead 3 and the mold s7. Occasionally it occurred. The gap 9 has an interval δ of several μm to several tens of μm and a depth of about several 100 μm, but when such a gap 9 occurs, moisture enters the gap 9 from the outside and corrodes the internal wiring of the semiconductor package. Disconnection may occur and cause a malfunction.

Therefore, in order to prevent the occurrence of gaps in the semiconductor package, conventionally, as shown in Japanese Patent Publication No. 49-49107, etc., when bending the leads, the vicinity of the outer m + Measures were taken, such as restraining the suspects.

Fig. 6 shows a local cross-sectional view of conventional lead bending processing to prevent the occurrence of such gaps, and the same parts as in Fig. 5(b) described above are given the same reference numerals. be.

That is, 2 is an external lead, 3 is an internal lead, and 7 is a molded part. Conventionally, during lead bending, the lead bending part of the external lead 2 is machined using an upper surface restraint jig 10 and a lower surface restraint jig 11. By applying a downward bending force (lead bending load) pH to the external lead 2 while restraining the external lead 2 and applying a restraining force P from above and below, the bending force PM is transmitted to the internal lead 3 and the mold part 7. This prevents the occurrence of a gap at the interface between the internal lead 3 and the mold 7.

[Problem that the invention seeks to solve]

The above technology requires jigs to restrain the upper and lower surfaces of the leads, so the bending part of the external lead is bent from the resin end.
It is necessary to separate the lead by the width 4 of the restraint jig on the lower surface of the lead.

Therefore, the width of the resin portion had to be made smaller than the interval between the external leads by the size 4.

Recently, however, as chips have become larger, there has been an increasing demand for increasing the width of the resin portion, and it has become necessary to increase the width of the resin portion accordingly without providing a lead restraint jig. For this reason, the leads could not be restrained, and when bending the leads, bending force was transmitted to the inside, creating a gap between the internal leads and the molded part.

An object of the present invention is to widen the gap that occurs during bending without restricting the lead.

[Means for solving problems]

The above object is achieved by, before the bending process, pressing down the vicinity of the resin part of the external lead with a punch to plastically deform it, increasing the thickness of the lead inside the resin, and then performing the bending process.

[Effect]

By compressing the vicinity of the resin of the external lead with a punch before bending, the removed material flows around the punch, and the area around the punch is raised. This swelling is also transmitted to the leads inside the resin, increasing the thickness of the inner leads. At this time, the resin portion is elastically deformed.

By bending the lead after this, the thickness of the lead decreases, but by increasing the thickness of the lead before bending by an amount corresponding to this decrease, a problem occurred at the interface between the lead and the resin. Gap can be eliminated.

〔Example〕

Embodiments of the present invention will be described using FIG. 1 and FIGS. 7 to 9.

Figure 7 is a perspective view showing the thickness increasing method before bending and the mold used therein, Figure 1 is an enlarged view showing details of the part to be thickened in Figure 7, and Figure 8 is after the thickness increasing. FIG. 9 is a front view showing a bending method and an apparatus used therein, and is an explanatory diagram showing the size of a gap that occurs when bending is performed without increasing the thickness.

First, the method for increasing the thickness will be explained. In Figure 7, 1
Reference numeral 2 designates a lower mold having a groove in a portion corresponding to the resin portion and shaped so as to support the lead without coming into contact with the resin portion. Reference numeral 1'3 designates an upper mold having a groove provided therein so as to contact only the lead portion.

This lower mold 22 is set on the table of a normal press device (not shown), and the upper mold is similarly attached to the upper part of the press device. The semiconductor after the cutting process is placed on the lower die 12. Next, drive the press device, and press the external lead 2 through the upper and lower molds.
A compressive load is applied to the reed and the reed is rolled down. At this time, the periphery of the punch bulges due to the flow of the material, increasing the thickness of the lead.

Next, it will be explained with reference to FIG. In the figure, 12 is the lower mold, 13 is the upper mold, and the portion where the internal lead 3 is to be thickened is shown in an enlarged manner.

As shown in the figure, the contact width S of the lower die 12 with the lead.

The contact width S of the upper die 13! By making it larger than
An indentation can always be made on the top surface of the lead.

By pressing down the external lead 2 in the vicinity of the resin portion by the above-mentioned upper mold and lower mold, a bulge is generated around the rolled part of the upper mold due to the flow of the removed material. Let the height of this swelling be d. This swelling propagates to the inside of the resin portion, increasing the thickness of the internal lead. At the same time, the resin part is compressed and deformed, but since the elastic modulus of the resin is as small as one tenth to several tenths of that of metal, and the strain in the elastic range is much larger than that of metal, no plastic deformation occurs.

Thereafter, the lead is bent using the apparatus shown in FIG. In FIG. 8, 14 is a lower mold on which a semiconductor is placed, 15
1 is an upper mold, and 16 is a bending roller fixed to the upper mold.

The resin portion of the semiconductor is placed on the lower die 14 so as to be in contact with it, and the upper die to which the rotatable bending roller 16 is attached is lowered to bend the lead.

At this time, due to the bending process, the wall thickness of the lead near the bend process area is reduced. However, since the internal lead has increased in thickness as described above, this offsets the increase in thickness and keeps the thickness at the same level as before deformation.

At this time, the resin portion that has been compressed as a result of increasing the thickness of the internal lead recovers elastically, and no gap is created between the internal lead and the resin portion.

In this example, the lead was made of steel with a thickness of 0.2M. Further, the height d of the internal lead at the end of the resin was determined as follows. FIG. 9 shows the phenomenon that occurs when bending the lead in this embodiment with only the bottom surface of the resin part supported without increasing the thickness.
This is the size of the gap between the lead and the resin. The horizontal axis represents the ratio of the distance from the resin end to the lead thickness. The raised height d may be set so that this gap is filled even after the bending process.

Further, the contact width S of the upper die was made 2 to 3 times the plate thickness, and the width of Sl was made larger than the island by about the size of the plate thickness.

As described above, according to this embodiment, since the thickness of the internal lead is increased before the lead is bent, no gap is created between the lead and the resin even after the bending process.

In this embodiment, the shape of the surface of the upper mold that comes into contact with the lead is flat, but the peripheral part of the upper mold can be thickened even if it has a wedge shape, a circular shape, or the like.

Furthermore, it has been clearly demonstrated in the field of plastic mechanics that by using a material with a particularly small work hardening index n value, a large amount of heave can be obtained with the same amount of reduction.

In addition, in this embodiment, the contact width St of the upper mold is changed to the contact width S of the lower mold.
, is made smaller than S, but conversely, even if S is made larger than S, the thickness of the internal lead can be increased in the same way.

〔Effect of the invention〕

According to the present invention, a semiconductor package with no gaps can be manufactured without supporting the leads.

The width of the resin part can be increased, making it possible to mount a larger chip.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the semiconductor lead forming method according to the present invention, FIG. 2 is a manufacturing process diagram of a semiconductor package,
Fig. 3 is a plan view of the lead frame used for lead bending, Fig. 4 is a partially omitted perspective view showing the state of the semiconductor package during the manufacturing process, Figs. 5(a), (b), and Fig. 6. 7 is a cross-sectional view of a main part of a semiconductor package after lead bending has been performed using a conventional lead bending method, FIG. 7 is a perspective view showing a mold used in the thickness increasing method before bending according to the present invention, and FIG. FIG. 9 is a front view showing the apparatus used in the bending method after increasing the thickness of the present invention, and is an explanatory view showing the size of the gap that occurs when the lead is bent without increasing the thickness. 2...External lead 3...Internal lead 7...
・Mold ga 12...Lower mold 13...Upper mold 16...Bending roller-ゝ、Representative Patent attorney Masaru Ogawa Yujizuke A,, --,/ 1 Figure 12, T-type 131 Type Oni 2 Items Figure 3 Figure 4 Figure 5 (C) Figure 6 Figure 7 Hardware

Claims (1)

[Claims] 1. In the semiconductor lead molding method, before bending the lead, the vicinity of the resin end is crushed to create a bulge in the peripheral area, and as a result, the thickness of the internal lead near the resin end is increased. A semiconductor lead forming method.