JP2781233B2 - Lead frame mold forming method and mold forming apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mold forming method and a mold forming apparatus for performing resin molding and forming of a lead frame.

(Prior art) Outer leads of a lead frame are bent into a required shape to be mounted on a substrate or the like, and are commercialized. In a normal manufacturing process, a semiconductor chip is mounted on a lead frame and sealed with a resin. , Forming process in the post process.

However, when bending the outer lead after resin sealing, a micro gap may be formed at the boundary between the outer lead and the resin sealing part due to deformation distortion due to tensile force or the like when bending the outer lead. A defect such as disconnection may be caused by affecting the semiconductor chip portion in the resin.

If a micro gap enters the boundary between the resin sealing portion and the outer lead, it has a significant adverse effect on the moisture resistance of the semiconductor device.To avoid this, separately from the above method, bend the lead frame before resin sealing. A method of processing the lead frame and sealing the lead frame with a resin is also performed.

(Problems to be Solved by the Invention) In the case of the above-described method in which the resin is sealed after bending the lead frame, a micro gap is not inserted in the sealing resin because the force at the time of bending is not applied to the sealing resin. However, since the lead frame that has been bent in advance must be set in a mold, bending accuracy of the lead frame is an important issue. That is, the bending accuracy of the lead frame is much lower than the accuracy of the mold due to springback or the like. Therefore, it is extremely difficult to accurately set the bent lead frame in the mold, and there has been a problem that the mold is damaged at the time of molding, and mold flash is likely to occur due to an error in accuracy.

Therefore, the present invention has been made as a method for solving the problems of bending the outer lead after the resin sealing described above and the problem of bending the resin after bending the resin in advance. An object of the present invention is to provide a lead frame mold forming method and a mold forming apparatus which can be bent without generating a micro gap in a resin.

(Means for Solving the Problems) The present invention has the following configuration to achieve the above object.

That is, a cavity for resin sealing, a mold dam provided around the cavity to resin seal a dam barless lead frame, and a base of an outer lead of the lead frame around the cavity at the time of mold clamping. And a guide die for positioning the lead frame. The mold is guided by the outer surface of the mold and moves toward and away from the outer lead. By this, a mold forming method of a lead frame using a bending die for forming the outer lead,
A lead frame is set in the mold die, the mold die is clamped, the outer lead is pinched and supported at the base by the pinch portion, and the outer lead is bent by driving the bending die. After the processing is started, the cavity is filled with a molten resin to obtain a package in which resin sealing and outer lead bending have been performed.

A cavity for resin sealing; a mold dam provided around the cavity for resin sealing a lead frame without a dam bar; And a guide pin for positioning the lead frame, and the outer lead is positioned at the base position by the clamping unit by clamping the mold. Before the cavity is filled with the molten resin, the outer lead is guided by the outer surface of the mold and starts moving toward and away from the outer lead, thereby forming the outer lead. A bending die is provided.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory view showing one embodiment of a mold forming apparatus to which a mold forming method for a lead frame according to the present invention is applied.

The mold forming apparatus includes a mold for sealing a semiconductor chip with a resin, and a bending mold provided adjacent to the mold. The bending mold is for bending the outer lead of the lead frame.

The mold has an upper mold 12 and a lower mold 14 in which a cavity 10 for resin sealing is formed, and the upper mold 12 and the lower mold 14 are fixed to bases 16 and 18, respectively. Base 16
Ejector pins 20 and 22 are respectively installed in the upper mold 12, the base 18 and the lower mold 14 so as to penetrate them.

The bending die is installed adjacent to the side of the upper die 12 and the lower die 14, and in the embodiment, the upper die 30 of the bending die can be moved up and down on one side of the upper die 12. And a lower mold 32 of a bending mold is integrally formed on the side of the lower mold 14. Upper die 30 above
Is connected to a pushing pin 34 linked to a cylinder driven separately from the mold clamping cylinders of the upper mold 12 and the lower mold 14, and the pushing pin
It is pushed by 34 and slides along the side surface of the upper mold 12.

The upper die 30 and the lower die 32 are formed in accordance with the bent shape of the outer lead.

The connection between the upper mold 12 and the lower mold 14 and the bending mold is a clamping portion 15 for clamping the base of the outer lead of the lead frame. That is, when the upper mold 12 and the lower mold 14 are clamped, the clamping portion 15 clamps and supports the base of the outer lead.

36 is a guide pin for positioning the lead frame when setting the lead frame in the mold. The guide pin 36 is connected to a cylinder 38 or the like and is driven up and down.

Next, a method of performing resin sealing and forming of outer leads using the mold forming apparatus of the above embodiment will be described.

Although the shape of the lead frame 40 to be used is not particularly limited, a lead frame in which the outer leads 42 are provided on one side of the frame as shown in FIG. 2 will be described. The lead frame 40 may be formed only on one side of the frame. 44 is a resin sealing portion.
Here, the resin sealing is performed by the mold dam 45. Mold dam
Numeral 45 is for projecting by the thickness of the lead frame according to the shape of the lead, and for sealing the resin within a predetermined range without using a dam bar.

First, as shown in FIG. 1 (a), the lead frame 40 is set on the lower mold 14 with the mold opened. 50 is a semiconductor chip. Here, the outer lead 42 of the lead frame 40 is the upper die of the bending mold as shown in the figure.
30 and the lower die 32, and inserted through the guide pins 36 and the guide holes 46 of the lead frame 40 so that the lead frame
Position 40. Note that a guide hole 47 may also be provided on the other side edge of the lead frame 40 and set on the lower mold 14.

Next, the upper mold 12 and the lower mold 14 are clamped, the clamping unit 15 clamps and supports the base of the outer lead 42 of the lead frame, and the upper mold 30 is lowered and pressed between the lower mold 32 and the lower mold 32. And the outer lead 42 is bent. At this time, the side edges of the lead frame 40 are bent together with the outer leads 42.

During bending, the guide pin 36 moves down and guide holes
It deviates from 46, which enables bending.
In addition, as shown in FIG. 2, the guide hole 46 may be formed in an elongated hole in the width direction so that the bending can be performed while the guide pin 36 is projected.

When applying the method of forming the guide hole to the long hole when bending both side edges of the lead frame, both the guide holes on both side edges are formed in the long hole, and the guide is set when the lead frame is set in the mold. Make sure the pin abuts inside the slot. Thus, the lead frame can be positioned without play and can be used as a relief during bending.

When the bending process is completed, the cavity 10 is filled with a molten resin and sealed with the resin while the lead frame 40 is held by the pressure. 60 is a mold resin. At the time of resin sealing, the upper mold 12 and the lower mold 14 close the mold for a while to cure the resin, and during this time, the upper mold 30 and the lower mold 32 also close to form the outer leads 42. .

After resin sealing is completed, the upper mold 30 of the bending mold is moved upward to return to the original position, and then the upper mold 12 and the lower mold 14 are opened, and the package is ejected using the ejector pins 20 and 22. Release the mold. After releasing the package, the guide pins 36 are moved up for the next lead frame setting.

Thus, a package in which the resin sealing and the outer lead bending process are performed can be obtained. The obtained package is thereafter commercialized by removing unnecessary parts such as rails.

The above example is an example in which one side of the mold portion is formed. FIG. 3 shows an example in which both sides of the mold portion are formed. In this example, the cutting and bending punch 70 is provided to move up and down adjacent to both sides of the upper mold 12,
Further, a frame holding plate 72 is provided on the side of the cutting / bending punch 70. The frame holding plate 72 is fixed to the suspension bolt 74 and is pushed up and down. A fitting hole 78 into which the protruding end of the fixed guide pin 76 fits is formed in the lower surface of the frame holding plate 72.

The lower mold 14 is provided with a cavity for resin sealing in the same manner as in the above example, and is provided with a clamping portion 15 for clamping and supporting the lead frame 80. Further, the lower die 14 is provided with a lower die 32 for bending and forming a lead corresponding to the cutting and bending punch 70, and a die 82 for shearing off the lead frame 80. The fixed guide pin 76 is fixed to the lower mold 14 and positions the lead frame 80.

FIG. 4 shows an example of a lead frame used in a forming mold having the above configuration. The lead frame 80 has leads extending from both sides of the molded portion, and is formed and resin-sealed using the forming die having the above-described configuration. Although the illustrated lead frame 80 is a matrix frame having two rows of molded parts, the same applies to a case of a normal lead frame of one row or a matrix frame of three or more rows.

The position A in the figure is a portion which is sheared off by the cutting and bending punch 70 and the die 82. Connecting piece for connecting the tip of the lead
By shearing off both ends of 83, the lead is formed while its tip is connected.

The resin sealing is performed by a mold dam. Mold Dam 84
Is a dam provided on the mold side in order to prevent the mold resin from leaking between the leads during resin sealing, and is provided so as to protrude by the thickness of the lead frame according to the lead shape.
The mold dam 84 is indicated by a two-dot chain line in FIG. 86 is a guide hole provided on the rail.

When the mold forming is performed by the mold apparatus shown in FIG. 3, it is performed as follows. First, the guide hole
The lead frame 80 is pinched and held between the upper mold 12 and the lower mold 14 by aligning the 86 and the fixed guide pin 76, and the lead frame 80 is clamped between the frame holding plate 72 and the lower mold 14. Hold. With the lead frame held down by the frame holding plate 72, as shown in FIG.
Is moved downward, the portions A at both ends of the connecting piece 83 are sheared off, and then the lead is bent by being pressed against the lower mold 32. After bending, the cavity is filled with resin and molded.
After the molding, the products that have been lead-formed and resin-sealed by the ejector pins 20 and 22 are released.

In the case of the matrix frame shown in FIG. 4, two sets of mold forming sections are provided in the width direction in accordance with the arrangement of the matrix frame.

In the case of the mold forming apparatus shown in FIG. 3, the mold forming can be performed on the lead frame of the type in which the leads extend from both sides of the mold portion, and the shear-off of the lead frame and the bending of the leads are the same. Can be performed in the mold, and when forming the lead, the lead tip is formed while being connected with the connecting piece 83, so that the lead can be bent accurately without being separated, and the connecting piece 83 There is an advantage that chips are not left in the mold because they are discharged in connection with the lead.

FIG. 5 shows another example of a lead frame used in the above molding. In this lead frame, outer leads 90 extend on both sides of the center line, the ends of the outer leads are supported by a rectangular frame 92, and adjacent frames 92 are connected by connecting portions 94. The guide hole 96 is a connecting part 94
Is provided. In the case of this lead frame, since the guide hole 96 is inside the bending position of the outer lead 90, it does not hinder the bending process, and there is no need to move the guide pin up and down. When sealing with resin, a method using a mold dam 98 is used in the same manner as in each of the above examples.

As described above, according to the mold forming apparatus of the present invention, the bending of the lead and the resin sealing of the semiconductor chip can be performed in the same apparatus, which has the following advantages.

Since the lead frame is set in the mold before bending, the setting is much easier than in the case where the lead frame is set in the mold after bending. Further, there is no need to worry about an accuracy error caused by bending.

By positioning the lead frame with the guide pins 36 and the like, the lead frame can be accurately set on the mold and the bending mold. As a result, the occurrence of mold flash during resin sealing can be reduced, and accurate processing can be performed during forming processing.

Since the mold is heated to about 180 ° C. to seal the resin, the lead frame can be formed at a relatively high temperature by this heat. By performing the forming process at a high temperature, the spring back of the lead frame can be reduced, and the forming accuracy can be improved.

Since the outer lead is formed first and then sealed with the resin, it is possible to eliminate the adverse effect of forming a micro gap when bending the outer lead in the sealing resin.

In the above embodiment, the resin sealing is performed after the lead forming process. However, the resin sealing may be started with a slightly delayed timing from when the lead forming process is started. This is because the lead frame is clamped and held by the upper mold and the lower mold, and it is necessary to clamp the mold for a while during resin molding. In this way, the production efficiency can be increased.

As described above, the present invention has been described variously with reference to the preferred embodiments. However, the present invention is not limited to the above-described embodiments, but can be applied to various types of lead frames and the like. Of course, many modifications can be made without departing from the scope of the invention.

(Effect of the Invention) According to the lead frame mold forming method and the mold forming apparatus according to the present invention, as described above, the lead frame can be accurately set in the mold and the bending process can be performed accurately. And resin sealing. In addition, since the outer lead is bent before the resin is sealed, problems such as generation of a micro gap at the boundary between the sealing resin and the outer lead can be solved. Also, since the bending of the outer leads and the resin sealing can be performed in the same step, the working steps can be shortened, and the production efficiency can be improved, and so on.

[Brief description of the drawings]

1 (a), 1 (b) and 1 (c) are explanatory views showing the operation of a mold forming apparatus according to the present invention, FIG. 2 is an explanatory view showing a lead frame, and FIG. FIG. 4 is an explanatory view showing another example and operation of the lead frame, FIG. 4 is an explanatory view showing another example of the lead frame, and FIG. 5 is an explanatory view showing still another example of the lead frame. 10 …… cavity, 12 …… upper mold, 14 …… lower mold, 15…
… Nipping part, 16, 18… Base, 20, 22… Ejector pin, 30… Upper die, 32… Lower die, 34… Pushing pin, 36…
Guide pin, 40: Lead frame, 42: Outer lead, 44: Mold part, 46, 47… Guide hole, 50
…… Semiconductor chip, 60 …… Mold resin, 70 …… Cutting punch, 72 …… Frame holding plate, 76 …… Fixed guide pin, 80 …… Lead frame, 82 …… Die, 84, 98 …… Die dam.

Claims (2)

(57) [Claims] 1. A cavity for resin sealing, a mold dam provided around a peripheral portion of the cavity to resin seal a dam-barless lead frame, and an outer part of the lead frame around the cavity at the time of mold clamping. A molding die having a pressing portion for pressing and supporting the base of the lead, and a guide pin for positioning the lead frame; a mold guided by an outer surface of the molding die and in contact with the outer lead; A method of forming and molding a lead frame using a bending mold for forming the outer leads by moving apart, wherein a lead frame is set in the mold, and the mold is closed. The outer lead is squeezed and supported at the base position by the squeezing portion, and the outer die is driven by driving the bending mold. And forming a package in which resin sealing and outer lead bending have been performed by filling the cavity with a molten resin after starting bending of the lead frame. 2. A cavity for resin sealing, a mold dam provided around the cavity for resin sealing a dam-barless lead frame, and an outer part of the lead frame around the cavity at the time of mold clamping. A molding die having a pressing portion for pressing and supporting the base of the lead, and a guide pin for positioning the lead frame; and an outer lead formed by the pressing portion by clamping the mold. Is squeezed and supported at the base position, and before the molten resin starts to be filled into the cavity, the outer lead is guided by the outer surface of the mold and starts to move toward and away from the outer lead. A lead frame mold / forming apparatus, comprising: a bending die for forming.