JPH07130780A - Molding method of lead frame - Google Patents

Abstract

PURPOSE:To prevent unnecessary resin from adhering to a lead frame and improve the mold removability of the lead frame after resin-sealing while evacuation through air vents is not affected. CONSTITUTION:A lead frame 10 which is composed of lead parts 16 which are extended outward from parts 12 to be sealed and rail parts 14 which are connected to the lead parts 16 is placed in the offset recess 26 of a mold 22 and the parts 12 to be sealed are placed in cavities 28 which are linked with air vents 32 which are so formed in the mold 22 as to face the rail parts 14. The mold 22 is closed. The cavities 28 are filled with melted resin to seal the parts 12 with resin. When the mold 22 is closed, connection parts 42 with which the lead parts 16 and the rail parts 14 are connected to each other and which are provided in gaps 34 between the offset recess 26 and the lead parts 14 and between the cavities 28 and the air vents 32 are crashed by the mold 22 to restrict the flows of the melted resin in the gaps 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a lead frame, and more specifically, it sets the lead frame in an offset concave portion of a die and sets a sealed portion of the lead frame in a cavity, The present invention relates to a lead frame molding method in which a mold is closed, a molten resin is filled in a cavity, and a sealed portion is resin-molded (molded).

[0002]

2. Description of the Related Art A conventional lead frame molding method will be described with reference to FIGS. When the sealed portion 12 of the lead frame 10 shown in FIG. 4 is resin-sealed, for example, as shown in FIG.
00 in the offset recess 102, and the sealed portion 12 of the lead frame 10 is set in the cavity 104. Subsequently, the upper die (not shown) is moved downward to move the upper die and the lower die 1
00 and mold are closed. In this mold closed state, molten resin is filled into the cavity 104 through the resin passage 106 provided in the upper mold, and the sealed portion 12 of the lead frame 10 is sealed.
Is sealed with resin.

[0003]

However, the above-described conventional lead frame molding method has the following problems. In the case of the mold shown in FIG. 5, the parting surface of the upper mold communicates with the cavity 104 in order to remove the air accumulated in the cavity 104 at the time of filling the molten resin, and the rail portion 14 of the lead frame 10 is used. The air vent 108 that faces is recessed. Air vent 108
Although the depth of the recess is extremely shallow, the molten resin intrudes into the air vent 108. In particular, the molten resin that has entered the gap 110 formed between the inner wall surface of the offset recess 102 and the outer wall surface of the lead portion 16 of the lead frame 10 and the rail portion 14 is inside the air vent 108 facing the rail portion 14. Break into. This intrusion causes a problem that the air venting effect of the air vent 108 is reduced.

Although the molten resin solidifies, the rail portion 1
The resin that has entered and solidified in the air vent 108 facing the No. 4 adheres to the upper surface of the rail portion 14. After the resin is sealed, the lead frame 10 is moved to the next step and subjected to predetermined processing. At that time, the resin adhering to the rail portion 14 peels off and falls, which may cause an unexpected trouble. There is a problem of becoming. Further, since the resin penetrates the entire gap 110, the resin is solidified and adheres, which becomes a resistance when the lead frame 10 is released from the lower die 100 after the resin is sealed. There is also a problem that it becomes worse. Therefore, the present invention provides a lead frame molding method that does not reduce the air vent effect from the air vent, prevents unnecessary resin from adhering to the lead frame, and improves the releasability of the lead frame after resin sealing. The purpose is to provide.

[0005]

In order to solve the above problems, the present invention has the following constitution. That is, a lead frame including a sealed portion, a lead portion extending outward from the sealed portion, and a rail portion connected to the lead portion is set in an offset concave portion of a mold, The sealed part is set in a cavity communicating with an air vent formed in the mold so as to face the rail part, the mold is closed, and molten resin is filled into the cavity to form the sealed part. In a method of molding a lead frame in which a sealing portion is resin-sealed, when the mold is closed, there is a gap between the offset concave portion and the lead portion, and the cavity and the air vent The connecting portion between the lead portion and the rail portion in the middle is crushed by a mold to regulate the flow of the molten resin in the gap.

[0006]

[Operation] The operation will be described. When closing the mold,
Since the connecting portion of the lead portion and the rail portion between the cavity and the air vent, which is in the gap between the offset concave portion and the lead portion, is crushed by the mold, the crushed connecting portion is deformed. To close the gap. As a result, the molten resin is prevented from flowing in the gap, so that the resin can be prevented from entering the air vent.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. In the present embodiment, a lead frame molding method in a transfer molding apparatus for resin-sealing the sealed portion 12 of the transistor lead frame 10 shown in FIG. 4 will be described as an example. First, FIG.
Along with this, the structure of the lead frame 10 will be described in detail. Transistor elements (not shown) are mounted on the sealed portion 12. In the case of the transistor of this embodiment, the lead portions 16 are extended three from the sealed portion 12 to the outside.

The rail portion 14 is formed outside each lead portion 16. In the case of the lead frame 10 of FIG. 4, the rail portion 14 is formed on the upper row (the outer side) and the lower row (the inner side) of the sealed portion 12 of the upper row and the sealed portion 12 of the lower row. It is formed on the outer (lower) side and the inner (upper) side of the lead portion 16. The outer end portion of each lead portion 16 is connected to each rail portion 14
Is connected at a right angle to. The through hole 18 of the lead frame 10 is a hole for inserting a guide pin (not shown) when it is set in a mold (not shown).

Next, a molding method of resin-sealing the sealed portion 12 of the lead frame 10 using a transfer molding apparatus will be described. FIG. 1 is a partial plan view showing a state in which the lead frame 10 is set in the lower die 22 which is one die. The mold is composed of a lower mold 22 and an upper mold 24 (see FIG. 3), and the upper mold 24 is mounted on a known transfer molding device (not shown) that moves up and down by a pressing mechanism to open and close the mold. There is. In the mold of this embodiment, the lead frame 10 is provided on the parting surface of the lower mold 22.
Is provided with an offset concave portion 26 for setting and a cavity 28 for resin-sealing the sealed portion 12.
On the other hand, on the parting surface of the upper mold 24, a resin passage 30 (only a part of which is shown in FIG. 1) for introducing the molten resin into the cavity 28, and for discharging air in the cavity 28 at the time of resin filling are provided. An air vent 32, which communicates with the cavity 28 when the mold is closed and faces the rail portion 14, is provided as a recess. With the upper mold 24 moved upward, the lead frame 10 is set in the offset recess 26 of the lower mold 22. At the same time, the sealed portion 12 of the lead frame 10 is set in the cavity 28.

FIG. 2 is an enlarged view of the portion shown in FIG. 1A when the lead frame 10 is set on the lower die 22. A gap 34 formed between the inner wall surface of the offset recess 26 of the lower die 22 and the lead portion 16 and the rail portion 14 of the lead frame 10.
Inside the connecting portion 36 of the lead portion 16 and the rail portion 14 between the cavity 28 and the air vent 32,
As shown in FIG. 2, it constitutes a part of the lower mold 22, and is in contact with the corner portion 44 of the protruding dam block 38. More specifically, as shown in FIG. 3 which is a sectional view taken along the line BB of FIG. 2, the side wall 40 of the dam block 38 is formed into an inclined surface, and the connecting portion 36 of the lead frame 10 is formed before the mold is closed. Contact is made in the middle of the slope. In this example,
The connecting portion 36 of the lead portion 16 and the rail portion 14 is in contact with the side wall 40 of the dam block 38 at the connecting portion 36 of the portion A shown in FIG. 2 and the connecting portion 42 of FIG.

In this state, the press mechanism is driven to drive the upper mold 2
Move 4 down and close the mold. When the mold is closed, the upper mold 24 moves downward in the direction of arrow C as shown in FIG. As the upper die 24 moves downward, the lead frame 10 is pressed against the lower die 22. At this time, the connecting portion 36 that is already in contact with the side wall 40 of the dam block 38 is compressed between the upper mold 24 and the lower mold 22. Since the lead frame 10 is formed of a material far softer than the upper mold 24 and the lower mold 22, the lead frame 10 is crushed during the compression and spreads outward. Due to this crushing and spreading, the gap 34 is closed between the cavity 28 and the air vent 32. As a result, the flow of the molten resin in the gap 34 is restricted by the crushed portion. This action is similarly performed for the connecting portion 42 shown in FIG. When the mold is sufficiently closed, a molten resin is filled into each cavity 28 through a resin passage 30 by a resin filling mechanism (not shown, which is a conventionally known mechanism including a pot, a plunger, etc.), and the sealed portion 12 is formed. Are resin-sealed. At the time of resin sealing, the molten resin leaking from the cavity 28 enters the gap 34, but the gap 34 is closed by the connecting portions 36 and 42, so that the molten resin cannot further enter. Therefore, the resin does not enter the air vent 32 through the gap 34, and unnecessary resin does not adhere to the rail portion 14.

When the resin filled in the cavity 28 is solidified, the upper mold 24 is moved upward to open the mold. When the mold is sufficiently opened, the resin-sealed lead frame 10 is released. Also in this case, since the amount of the resin that enters the gap 34 is regulated to be small, the adhesive force between the lower mold 22 and the lead frame 10 due to the intruding resin is weak, and the mold can be easily released. It should be noted that although traces due to crushing remain on the connecting portions 36 and 42 of the lead frame 10, there is no problem because the lead portion 16 and the rail portion 14 are finally separated from this portion.

Further, in the above embodiment, the lead frame 10 is connected to the rail portion 14 continuous in the longitudinal direction (formed at right angles to the longitudinal direction of the lead frame 10).
Although the lead frame having the lead portion 16 has been described, it goes without saying that the present invention is also applicable to a lead frame having lead portions formed in other directions. For example,
The lead portion 16 as shown in FIG. 4 and a section bar 14a (see FIG. 4) that constitutes a part of the rail portion 14 and defines the adjacent sealed portion 12 are connected (in the longitudinal direction of the lead frame). It can also be applied to a lead frame having lead portions (not shown) formed in parallel. Also in this case,
Similar to the embodiment of FIG. 1, the lead portion and the section bar 14a
By crushing the connection portion of with a mold, the gap can be closed and the flow of the molten resin can be prevented. Although various preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. For example, the lead frame 10 may be a lead frame other than a transistor. It goes without saying that many more modifications can be made without departing from the scope.

[0014]

When the lead frame molding method according to the present invention is used, when the mold is closed, the lead frame is present in the gap between the offset recess and the lead portion and between the cavity and the air vent. Since the connecting portion between the lead portion and the rail portion is crushed by the mold, the crushed connecting portion is deformed to close the gap. As a result, the molten resin is prevented from flowing in the gap, so that it is possible to prevent the resin from entering the air vent, so that the air venting effect from the air vent during the resin sealing is not reduced. Further, since the resin is prevented from entering the air vent, unnecessary resin does not adhere to the lead frame, so that it is possible to prevent the occurrence of troubles caused by the unnecessary resin falling in the step after the resin sealing. . Furthermore, since the amount of resin that enters the gap between the offset recess and the lead portion can be regulated, the adhesive force between the die and the lead frame due to the intruding resin is weak, and the lead frame after resin sealing It exhibits a remarkable effect such as not lowering the releasability.

[Brief description of drawings]

FIG. 1 is a partial plan view of a lower mold showing an embodiment of a lead frame molding method according to the present invention.

FIG. 2 is an enlarged view of part A in FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a partial plan view of a lead frame which is resin-sealed by the molding method of the embodiment.

FIG. 5 is a partial plan view of a lower mold showing a conventional lead frame molding method.

[Explanation of symbols]

 10 lead frame 12 sealed part 14 rail part 16 lead part 22 lower mold 24 upper mold 26 offset recess 28 cavity 30 resin path 32 air vent 34 gap 36, 42 connection part 38 dam block 40 dam block side wall 44 dam block corner

Claims (1)

[Claims] 1. A lead frame comprising a sealed portion, a lead portion extending outward from the sealed portion, and a rail portion connected to the lead portion is set in an offset concave portion of a mold. Then, the sealed portion is set in a cavity communicating with an air vent formed in the mold so as to face the rail portion, the mold is closed, and molten resin is filled into the cavity. In the method of molding a lead frame in which the sealed portion is resin-sealed, when the mold is closed, the lead frame is present in a gap between the offset recess and the lead portion, A method for molding a lead frame, comprising: crushing a connecting portion between the lead portion and the rail portion between the air vent and a mold to regulate the flow of the molten resin in the gap.