JPH098199A - Lead frame for semiconductor device - Google Patents

Abstract

PURPOSE: To prevent the short-circuit between the outer periphery of a radiating metal plate mounted at the frame and the lead frame by increasing the insulating distance between the lead frame and the outer periphery of the plate. CONSTITUTION: The lead frame for the semiconductor device is formed by preparing a metal plate previously coated with adhesive 2 and laminating to the frame 1 while punching the plate 3 of a predetermined shape from it. A coining part 4 for increasing the insulating distance between the outer periphery 3a of the plate 3 and the frame 1 is provided at the position opposed to the outer periphery 3a of the plate 3 to be laminated with the frame 1 at the frame 1. The depth of the part 4 is suitably substantially equal to the thickness of the adhesive 2. The outer periphery 3a of the plate 3 may be disposed substantially at the center of the part 4 in the lateral direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame for a semiconductor device in which a metal plate is attached to a lead frame via an insulating layer, and more particularly to a lead frame for preventing a short circuit between the metal plate and the lead frame.

[0002]

2. Description of the Related Art In recent years, with the increase in the density and speed of elements, development of lead frames for semiconductor devices having improved heat dissipation has become active. A metal plate that functions as a heat spreader is laminated in the thickness direction of the lead frame in order to improve heat dissipation, but especially recently, a metal plate to which an adhesive has been applied in advance has been prepared, and the metal plate has a predetermined shape. Attention has been paid to the method of sticking to the lead frame while punching. This has the advantage that the metal plate can be attached to the lead frame at low cost.

FIG. 2 is a typical example of the lead frame structure for a semiconductor device bonded in this way. The inner lead portion 1a of the lead frame 1 having the device hole 6 in the center is covered with the device hole 6. The metal plate 3 coated with the adhesive 2 is attached to the. The semiconductor chip is bonded inside the device hole 6 on the metal plate 3.

[0004]

A particular problem in a lead frame for a semiconductor device, in which a metal plate for heat dissipation is attached to a lead frame, is an electrical short circuit between the metal plate and the lead. As shown in FIG. 3, which is an enlarged view of the portion C in FIG. 2, the portion A in the drawing in which the lead frame 1 and the adhesive-attached metal plate 3 overlap each other has a high electrical insulation property with respect to the interposing adhesive 2. The problem can be solved by using, for example, a thermoplastic polyimide adhesive.

However, at the location B in the figure where the outer peripheral portion 3a of the metal plate 3 faces the lead frame 1, the shortest insulation distance between the two is inevitably the thickness of the adhesive 2, but Since the thickness is generally as thin as about 20 μm, the following problems occur.

(1) Conductive foreign matter generated by punching out a metal plate produced by punching a metal plate with an adhesive is placed between the outer peripheral portion of the metal plate and the lead frame. Short the metal plate and the lead frame.

(2) A lead frame for a semiconductor device is packaged after mounting a semiconductor element. However, when the moisture absorption of the resin of the package becomes large, especially when the lead frame and the metal plate are both made of copper, the lead is formed. Due to the potential applied to the frame side, migration occurs and copper dendrites (dendrites) are deposited from the lead frame side toward the metal plate side, causing a short circuit between the metal plate and the lead frame.

An object of the present invention is to solve the above-mentioned problems of the prior art and provide a lead frame for a semiconductor device capable of preventing a short circuit between the outer peripheral portion of the metal plate and the lead frame. is there.

[0009]

SUMMARY OF THE INVENTION The present invention provides a lead frame for a semiconductor device in which a metal plate is bonded to a lead frame via an insulating layer, in a lead frame at a portion facing the outer peripheral portion of the bonded metal plate. A coining portion for increasing the insulation distance between the outer peripheral portion of the metal plate and the lead frame is provided.

Further, according to the present invention, in a lead frame for a semiconductor device in which a metal plate coated with an adhesive in advance is punched into a predetermined shape and bonded to a lead frame, a lead at a position facing an outer peripheral portion of the bonded metal plate. The frame is provided with a coining portion for increasing the insulation distance between the outer peripheral portion of the metal plate and the lead frame.

In these cases, the depth of the coining portion is preferably in the range of about the thickness of the insulating layer or adhesive to about half the thickness of the lead frame. If it is too shallow, a short circuit between the metal plate and the lead frame cannot be effectively prevented,
This is because the strength of the lead frame becomes too weak if it is too deep.

Further, it is preferable that the outer peripheral portion of the metal plate is positioned substantially at the center in the width direction of the coining portion. If the width of the coining portion is too narrow, the interface between the adhesive and the package resin cannot be long, and if it is too wide, the lead frame strength will be insufficient.
The range is good.

[0013]

When a coining portion is provided on the lead frame at a position facing the outer peripheral portion of the metal plate as in the present invention, when the coining portion is not provided, only the thickness of the insulating layer has been used. The shortest insulation distance between the outer peripheral portion of the plate and the lead frame is increased by the depth of the coining portion. Therefore, the risk of a short circuit between the metal plate and the lead frame is reduced. In addition, the insulation distance from the outer peripheral portion of the metal plate along the adhesive to the lead frame increases by the amount corresponding to the coining portion width, and the distance between the insulating layer and the package resin increases significantly. It is possible to prevent migration / dendrite that is expected to occur.

Further, as in the present invention, when a metal plate with an adhesive is punched and bonded to a lead frame,
Conductive burrs such as punching burs that are generated during punching are brought in as they are, but since the coin frame is provided on the lead frame at the opposite location on the outer periphery of the metal plate, there is a gap between the metal plate and the lead frame due to the conductive burrs. The short circuit of can be effectively avoided.

Here, the depth of the coining portion is preferably substantially equal to the thickness of the insulating layer or the adhesive. This is because if the depth of the coining portion is shallower than these thicknesses, the insulation distance cannot be obtained, and if it is deeper, the strength of the lead frame cannot be maintained.

Further, it is preferable that the outer peripheral portion of the metal plate is positioned substantially in the center of the coining portion in the width direction. This is because if the outer peripheral portion of the metal plate deviates from the center of the coining portion, a short circuit due to dendrite / migration may not be effectively avoided.

[0017]

1 is a cross-sectional view showing a bonding state of metal plates of a lead frame for a semiconductor device according to an embodiment of the present invention. In this case, a metal plate 3 having an adhesive layer 2 as an insulating layer applied on one side in advance is prepared. As the adhesive 2, for example, a thermoplastic polyimide adhesive having high electric insulation is used. Further, copper having high thermal conductivity is used for the metal plate 3 as the heat spreader. This metal plate 3 is punched with a die to form a metal plate 3 having a predetermined shape, and the punched metal plate 3 is continuously bonded to the lead frame 1 as it is. The bonding position of the metal plate 3 is the inner lead portion 1 a adjacent to the device hole 6.
The same copper as the metal plate 3 is also used for the lead frame 1.

As shown, the metal plates 3 to be bonded together
A coining portion 4 for increasing the insulating distance between the outer peripheral portion 3a of the metal plate 3 and the lead frame 1 is provided on the lead frame 1 at a position facing the outer peripheral portion 3a in the direction crossing the leads. For a lead frame thickness of 150 μm, the depth of the coining portion 4 is 20 μm, which is equal to the thickness of the adhesive 2. The width of the coining portion 4 is 0.5 mm. The outer peripheral portion 3a of the metal plate 3 is attached so as to be located at the center of this width.

Therefore, the shortest insulation distance of the conventional one having no coining portion 4 is 20 μm corresponding to the thickness of the adhesive 2, whereas the shortest insulating distance is 20 μm in this embodiment.
Doubled to 40 μm, which is a large increase. This effectively prevents a conductive flash such as a punching flash that normally occurs when punching a metal plate from coming into contact with the lead frame 1 and the outer peripheral portion 3a of the metal plate 3 and short-circuiting during bonding. be able to.

Further, as in this embodiment, the lead frame 1
When both the metal plate 3 and the metal plate 3 are made of copper, migration and dendrites are likely to occur along the interface between the adhesive 2 and the package resin due to moisture absorption of the package resin. In the example, the outer peripheral portion 3a of the metal plate 3 is located substantially in the center of the coining portion 4 in the width direction, and the interface insulation distance 5 from the lead frame 1 to the metal plate 3 is 0 in addition to the thickness of the adhesive 2. Since it is 0.25 mm, it can be said that migration or dendrite that causes a short circuit does not occur. Further, even if it should occur, the horizontal distance from the outer peripheral portion 3a to the left and right lead frame portions is about 13.5 times that of the conventional one, that is, the life is 13.5.
Since it doubles, it can be said that there is almost no problem in practical use. This can effectively prevent a short circuit between the lead frame 1 and the metal plate 3.

By the way, when the lead frame is formed by punching, the coining portion can be processed by coining simultaneously with the punching in the die for punching the inner leads, so that the cost does not increase.

In the above embodiment, the lead frame for a semiconductor device, which is attached to the lead frame while punching the metal plate, has been described. However, in the present invention, the punching of the metal plate and the attaching of the metal plate are performed in separate steps. It can also be applied to a lead frame for a semiconductor device manufactured by the method.
Also, the case where both the lead frame and the metal plate are made of copper has been described.
Other metal material such as copper alloy may be used, and the metal plate may be other metal material such as aluminum and iron.

[0023]

According to the invention described in claim 1, since the lead frame is provided with the coining portion to increase the insulation distance between the outer peripheral portion of the metal plate and the lead frame, the metal plate and the lead frame are separated from each other. The risk of short circuiting can be reduced. Further, by providing the coining, the interface between the adhesive and the package resin is extended, and it is possible to prevent the generation of dendrite which causes a short circuit.

According to the second aspect of the present invention, since the metal plate with the adhesive is applied to the lead frame while being punched, it is applied to the lead frame. It is possible to effectively avoid a short circuit between the metal plate and the lead frame.

According to the third aspect of the present invention, the depth of the coining portion is in the range from the thickness of the insulating layer or the adhesive to about half of the thickness of the lead frame. The lead frame strength can be compatible.

According to the fourth aspect of the invention, since the outer peripheral portion of the metal plate is positioned substantially at the center in the width direction of the coining portion, a short circuit due to dendrite / migration can be more effectively avoided. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a bonding state of a metal plate with an adhesive for explaining an embodiment of a lead frame for a semiconductor device of the present invention.

FIG. 2 is a cross-sectional view of a cross-sectional view showing a bonding state of an adhesive-attached metal plate of a semiconductor device lead frame of a conventional example.

FIG. 3 is an enlarged view of a portion C in FIG. 2;

[Explanation of symbols]

 1 Lead Frame 2 Adhesive (Insulating Layer) 3 Metal Plate 3a Outer Part 4 Coining Part 5 Interface Insulation Distance

 ──────────────────────────────────────────────────の Continuing on the front page (72) Isao Yamagishi 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Within Hitachi Cable, Ltd.System Materials Research Laboratories (72) Inventor Shigeharu Takahagi 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Company System Materials Laboratory

Claims (4)

[Claims] 1. A lead frame for a semiconductor device in which a metal plate is bonded to a lead frame with an insulating layer interposed therebetween. In the lead frame facing the outer circumference of the bonded metal plate, the outer circumference of the metal plate and the leads are provided. A lead frame for a semiconductor device, comprising a coining portion for increasing an insulation distance between the frames. 2. A lead frame for a semiconductor device, wherein a metal plate coated with an adhesive in advance is punched into a predetermined shape and is bonded to a lead frame. In a lead frame at a portion facing the outer peripheral portion of the bonded metal plate, a metal is formed. A lead frame for a semiconductor device, comprising a coining portion for increasing an insulation distance between the outer peripheral portion of the plate and the lead frame. 3. The lead frame for a semiconductor device according to claim 1, wherein the coining portion has a depth ranging from the thickness of the insulating layer or the adhesive to about half the thickness of the lead frame. 4. The lead frame for a semiconductor device according to claim 1, wherein an outer peripheral portion of the metal plate is located substantially at a center in a width direction of the coining portion.