JPH0546044U - Lead frame for semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] To make resin filling uniform and to obtain a good package product without generation of voids without complicating a mold for resin encapsulation. [Structure] A pattern in which pads, inner leads, and outer leads are formed in a portion sandwiched between outer frames at both ends in the width direction, and one outer frame faces the pad side when resin-sealed except for the outer leads. A first notch for resin inflow is provided on the other side, and a second notch for resin accumulation is similarly provided on the surface facing the pad side on the other outer frame, and these first and second notches are resin-sealed. It is included in the region of the space and is exposed to the resin supply gate and the air vent channel provided in the mold. [Effect] It is possible to prevent deformation of pads and inner leads, breakage of wires, etc. in the resin sealing step, and a simple air vent channel provided in the mold is sufficient.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a lead frame for a semiconductor device, and more particularly to a lead frame capable of favorably performing resin mounting after mounting an element and wire bonding.

[0002]

[Prior Art]

 A lead frame used for assembling a semiconductor device is manufactured by a method in which a band-shaped metal material is stamped to form a pattern. This pattern mainly consists of a combination of a pad on which a semiconductor element is mounted, inner leads arranged around it, and outer leads connected to this inner lead, and various patterns are manufactured according to the product specifications. Then, after fixing the semiconductor element to the pad, the semiconductor element and the inner lead are bonded with a wire, and the stage and the inner lead portion are resin-sealed so that only the outer lead is projected outside to form a package.

An example of this resin sealing method is described in Japanese Patent Application Laid-Open No. 2-109343. This is to facilitate the charging of resin into a pair of resin-sealing upper and lower molds sandwiching the upper and lower sides of the lead frame, and to allow air to escape quickly at the start of sealing. The lower mold provided with a resin reservoir is used. If such a resin reservoir is provided, air can be quickly released from the resin-sealed space, and a good package product without voids can be obtained.

[0004]

[Problems to be solved by the device]

 However, it is necessary to prepare many molds for resin encapsulation, depending on the size of the lead frame, the shape of the package, and the like. Moreover, the shape of the inner wall of the mold differs intricately depending on the specifications, and it is often very difficult to manufacture the mold itself. For this reason, providing a resin reservoir in the lower mold as in the conventional example described above further complicates the design and manufacture of the mold, which may cause an obstacle in terms of cost. In addition, depending on the specifications, there may be cases where the resin reservoir cannot be made wide, making it impossible to expel air quickly, and it is not possible to support all products.

Further, in recent years, in the field of semiconductor devices, development of thin and small devices has been further advanced, and in particular for semiconductor devices used for IC cards, there has been an increasing demand for a total thickness of 1 mm or less. Further, in the case of an element of a semiconductor device having a large storage capacity, its size also increases, and the area occupied by the element with respect to the package size also increases.

Against such a background, when resin is sealed, if the resin is not evenly filled in the resin sealing spaces on the upper surface side and the lower surface side of the lead frame, the element is mounted. The pad portion is deformed so as to bend in the direction of low filling pressure. And, this phenomenon is more remarkable as the package thickness is smaller.

If the lead frame is deformed during resin encapsulation, the wire-bonded wire may be broken or a part of the pad may be exposed from the package, resulting in a high defective rate of the product. Moreover, not only the influence on the lead frame but also the warping and deformation of the lead frame between the upper die and the lower die will cause a gap, and the resin will flow out and cause resin burr.

As described above, particularly in the case where the pad size is small and the resin package is thin, the balance of resin injection is likely to be disturbed, so that there is a limit to the reduction of the defective rate and the yield is greatly affected. There is.

The problem to be solved in the present invention is to make the resin filling uniform and to obtain a package product without generation of voids without complicating the mold for resin encapsulation. ..

[0010]

According to the present invention, an outer frame is left at both ends in the width direction of a strip-shaped material made of a thin metal plate, and a pad, an inner lead, and an outer lead pattern are provided between these outer frames. The upper and lower surfaces of the band-shaped material are covered with a resin sealing mold, and the region from the pad to the inner lead portion is sealed with resin together with the semiconductor element mounted on the pad, leaving only the outer leads. A lead frame having a first notch for communicating a resin-sealed space between one surface of the strip-shaped material and the other surface of the outer frame on one end side in the width direction on the side where the outer frame faces the pad. A second notch that bulges along the resin sealing space is provided in the outer frame on the other end side, and the first notch is formed in the mold for resin sealing. It faces the resin supply gate and the second notch , Characterized in that the attachable to face the air flow path communicating with the outside of the resin sealing space into said mold.

[0011]

[Action]

 The band-shaped material on which the lead frame pattern is formed is sandwiched between the upper and lower molds for resin encapsulation, and resin is injected from the resin injection gate opened in the upper mold. Since the notch is located so as to widen the entrance of the resin material, the resin flows through the first notch into the upper mold and the lower mold almost evenly. Therefore, it is possible to balance the amount of resin injected into the upper and lower surfaces of the strip-shaped material, and to prevent the pad and the inner lead portions from being bent or displaced.

Further, since the second notch provided in the outer frame on the other end side communicates with the air vent passage provided in the mold, this second notch can be used not only as a resin reservoir but also as an air vent. .. Therefore, it is not necessary to provide the mold with a large recess for air removal, and a simple structure of the mold is sufficient.

[0013]

【Example】

 FIG. 1 is a schematic plan view of the lead frame of the present invention when it is resin-sealed.

In the figure, a lead frame pattern is formed on a metal thin strip material 1 by punching or etching. This pattern includes pads 2 on which semiconductor elements 6 are mounted, a large number of inner leads 3 arranged around them, and outer leads 5 which are integrated with these inner leads 3 by tie bars 4. These lead frame patterns are formed by resin-sealing, then the parts up to the outer leads 5 are separated from the strip-shaped material 1, the tie bars 4 are cut, and the bending process required for the outer leads 5 is performed. By applying, the final product is obtained.

FIG. 2 is a schematic view showing a pattern of only the pad 2 in the strip-shaped material 1, in which the inner leads 3 and the outer leads 5 are omitted.

When the lead frame pattern is formed by using the strip-shaped material 1, the strip-shaped material 1 is wound in a coil shape and continuously or intermittently flows in a line to sequentially form patterns. A manufacturing method is adopted. In such a manufacturing method, holes are required for feeding the band-shaped material 1 and for positioning. For this reason, the outer frame 1a is left on both ends in the width direction of the strip-shaped material 1, and the reference pin holes 1b for use in feeding and positioning the strip-shaped material 1 are formed in the outer frame 1a at a predetermined pitch. Things are used. On the other hand, the pad 2 is processed to be connected to the outer frames 1a on both sides by the support piece 2a.

In contrast to such lead frame pattern molding, in the present invention, in order to promote the flow of resin into the lower mold at a position corresponding to the gate side at the time of resin sealing with a mold. Have a composition. That is, as shown in FIG. 2, one outer frame 1a is provided with a resin inflow notch 1c on the surface facing the pad 2 as a first notch in the lengthwise direction. The distance between the outer edge of the pad 2 and the outer frame 1a is increased as shown in the arrow cross-sectional view).

Further, the other outer frame 1a is provided with a resin pool cutout 1d as a second cutout on the side facing the same direction of the pad 2. As shown in FIG. 1, the resin pool notch 1d has a front surface facing the pad 2, and has a shape in which an opening area is enlarged outward from the front surface. Note that FIG. 4 is a vertical cross-sectional view of the resin reservoir notch 1d, which corresponds to the view taken along the line BB in FIG.

FIG. 5 is a schematic vertical cross-sectional view of an essential part showing a state where the strip-shaped material 1 is sandwiched between the upper mold 10 and the lower mold 11, and the gate 11a is positioned so as to be aligned with the resin inflow notch 1c. The resin pool notch 1d communicates with a resin-filled space 12 formed by an upper mold 10 and a lower mold 11. The lower surface of the upper die 10 is provided with an air vent groove 10a for venting air from the resin-filled space 12 to the outside when the resin is filled. As shown in FIG. 1, this air vent groove 10a has a flow path that extends outward from the resin pool notch 1d and is opened to the outside at the end face of the upper die 10.

Here, when the resin is injected from the gate 11 a, the resin is filled so as to be distributed from the resin inflow notch 1 c to the upper surface side and the lower surface side of the strip-shaped material 1. That is, when the resin inflow notch 1c is not provided, when the resin is filled from the gate 11a as shown in FIG. 5, the resin flows upward into the resin-filled space 12, so that the upper surface side of the strip-shaped material 1 is Easy to be filled in advance. On the other hand, since the resin inflow notch 1c is positioned so as to be continuous with the flow path from the gate 11a, the resin inflow notch 1c also flows into the lower mold 11 direction below the strip material 1. It will be easier. Therefore, the upper mold 10 side is not filled with the resin first, and the resin is sealed in the upper mold 10 and the lower mold 11 at a substantially uniform filling speed.

As described above, by evenly filling the upper mold 10 and the lower mold 11, the load applied to the pad 2 from above is not increased and the pad 2 is prevented from being deformed so as to bend downward. To be done. Therefore, the position of the pad 2 does not change and the pad 2 is not exposed from the lower surface of the package after the resin sealing due to the large bending. Furthermore, since the deformation of the pad 2 is suppressed, the bonded wire is not broken.

Further, the injected resin is gradually filled to the right side in FIG. At this time, the air in the resin-filled space 12 is forced to flow toward the resin reservoir notch 1d, and is discharged to the outside from the air vent groove 10d communicating with the resin reservoir notch 1d. Since the resin pool notch 1d is formed relatively wide as shown in FIG. 1, even if the air vent groove 10a is small, the air flow is stagnated in the resin pool notch 1d. Can be discharged in this way. Therefore, even if the mold is not provided with a resin reservoir, by utilizing the space formed by the resin reservoir notch 1d of the band-shaped material 1, air can be quickly evacuated from the resin sealing space 12 during resin sealing. it can. Therefore, the inclusion of voids in the resin is eliminated and good packaged products can be obtained.

[0023]

[Effect of the device]

 In the present invention, since the resin inflow notch is provided on the side of the outer frame of the strip-shaped material of the lead frame facing the pad, when the resin is sealed, the resin passes through the resin inflow notch to the upper and lower surfaces of the strip-shaped material. Flow evenly. As a result, the filling pressure on the upper and lower surfaces of the lead frame pattern can be maintained evenly, deformation of the pads and inner leads and breakage of the bonded wires during the resin encapsulation process can be prevented, and resin encapsulation with a low defect rate is achieved. The product is obtained.

Further, since the resin reservoir notch is provided in the outer frame on the side opposite to the resin inflow notch, this resin reservoir notch can also be used as a flow path for air release during resin sealing. Therefore, if the mold is provided with a simple air vent groove and the resin reservoir notch is positioned so as to be continuous with the air vent groove, it is not necessary to provide the mold with a complicated recess or the like for venting air. Therefore, it is possible to easily manufacture a mold for resin encapsulation, sufficiently deal with the manufacture of package products with different specifications, and improve the productivity.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a lead frame of the present invention when it is resin-sealed.

FIG. 2 is a schematic perspective view showing a pattern of a lead frame having only a pad portion.

3 is a vertical sectional view taken along the line AA of FIG.

FIG. 4 is a view showing a notch for resin accumulation, which is taken along line B- of FIG.
It is a vertical cross-sectional view taken along the line B.

FIG. 5 is a schematic vertical cross-sectional view showing the flow of resin at the time of resin sealing by the upper mold and the lower mold.

[Explanation of symbols]

 1 band-shaped material 1a outer frame 1b reference pin hole 1c resin inflow notch (first notch) 1d resin pool notch (second notch) 2 pad 3 inner lead 4 tie bar 5 outer lead 6 semiconductor element 10 upper die 10a air vent Groove 11 Lower mold 11a Gate 12 Resin sealing space

Claims (1)

[Scope of utility model registration request] 1. A strip-shaped material made of a thin metal plate is left with outer frames at both ends in the width direction, and a pattern of pads, inner leads, and outer leads is formed between these outer frames, and upper and lower surfaces of the strip-shaped material are formed. A lead frame which is covered with a resin sealing mold and is sealed with a resin together with a semiconductor element mounted on the pad in the region of the inner lead portion from the pad, leaving only the outer leads. A first notch for communicating the resin-sealed space between the one surface and the other surface of the strip-shaped material is provided in the outer frame on one end side of the outer frame along the side where the outer frame faces the pad, and the other end side On the outer frame of
A second notch that bulges along the resin-sealed space is provided,
The first cutout is made to face the resin supply gate formed in the resin sealing mold, and the second cutout is made to face the air flow path communicating with the outside of the resin sealing space. A lead frame for a semiconductor device, which can be mounted inside.