JPH0828457B2 - Lead frame manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a method for manufacturing a lead frame, and in particular, a lead frame body having inner leads and a semiconductor element mounting portion are separately formed. The present invention relates to a method of manufacturing a lead frame that is fixed.

(Prior Art) In the field of high-power semiconductor integrated circuits, in order to use high power, the leads for current supply use a power plate instead of a bonding wire in order to prevent an increase in inductance in the connection part with the wire. In many cases, the method of connecting to the bonding pad of the chip is adopted.

Furthermore, since the amount of heat generated is large, there is a tendency that a large heat dissipation plate made of a metal plate having good heat dissipation is required instead of the die pad.

In such a power device, the lead frame main body and the heat dissipation plate are separately formed, and the heat dissipation plate and the lead frame main body are attached to the back side of the tip of the inner lead via an insulating double-sided tape. There are many.

Also proposed is a ground plate for grounding and a power plate, which are laminated on the lead frame body via double-sided tape, respectively, to achieve a reduction in the package size by substantially reducing the number of leads. ing. Thus, for the purpose of reducing the number of leads, for example, in the case of dropping from a plurality of pads to the ground line, a method of providing a grounding plate and connecting all of them to the grounding plate has become effective.

By the way, in these lead frames, coining and silver (Au), precious metal plating such as silver (Ag) are performed on the inner lead tip surface to ensure wireless bonding. Further, in the two-layer and three-layer bonding process, there is a problem that the plating surface is scratched or foreign matter is attached as the number of processes is increased.

In order to minimize this problem, the heat block H is subjected to relief processing as shown in FIG. 4, and the lead frame main body 5 is arranged so that the plated surface M is located in this relief processed portion K.
Measures are taken such as by mounting the and pressing from above.

However, this method not only makes it difficult to process the heat block, but also sometimes causes the plated surface to be damaged due to the positional deviation when the lead frame is placed on the heat block.

Furthermore, the problems that the plated surface comes into contact with the heater block or the guide portion during the transportation of the lead frame, and the plated surface is scratched or foreign matter adheres still remain.

(Problems to be Solved by the Invention) As described above, in the conventional lead frame, the plating surface at the tip of the inner lead is scratched or foreign matter is attached in the tape attaching process or the transporting process, which may reduce reliability. It was the cause.

The present invention has been made in view of the above circumstances, and provides a lead frame manufacturing method capable of protecting the plated surface of the tip of the inner lead in the tape attaching step and the conveying step and improving the lead frame manufacturing yield. The purpose is to provide.

[Structure of Invention]

(Means for Solving the Problem) Therefore, in the method of the present invention, thinning (coining) is performed at a position spaced a predetermined distance from the tip of the inner lead to the outer lead side to form a wide and thin region. ,
After applying the noble metal plating to the concave surface formed by this thinning, this inner lead is placed so that the concave side contacts the heat block, and further on this upper layer via the double-sided tape, for mounting the semiconductor chip By stacking the semiconductor chip mounting portions and heating them, the lead frame body is fixed to the semiconductor chip mounting portion.

(Operation) With the above configuration, the wall thickness of the tip of the inner lead is kept the same as the other regions, the coining region is formed to be slightly shifted to the outer lead side, and the plated region is the thin region. Therefore, even when the lead frame is placed on the heat block in the tape adhering step, the plated surface can be supported by the leading end portion and the inner lead middle portion so as not to come into direct contact with the heat block.

In addition, also when adhering to a conductive plate, a ground plate, or the like, it is possible to support the plated surface so that it does not directly contact the heat block.

Further, even in the carrying step, the carrying tool can be supported so as not to come into direct contact with the plated surface due to the presence of the most advanced thick portion.

As described above, the presence of the most advanced thick-walled portion enables mounting and carrying without the plated surface being constantly in contact with the support such as the heat block, and thus the manufacturing yield is significantly improved.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a main part of an inner lead tip of a lead frame for a power device formed by the method of the embodiment of the present invention.

As shown in the overall view of FIG. 2, this lead frame has a wide coining area (thin area) C formed at a position slightly spaced from the tip of the inner lead 1 to the outer lead 2 side, It is characterized in that the surface of this coining region C is plated with silver to form a plated surface M.

That is, a lead frame is mainly composed of copper, and a large number of inner leads 1 arranged so that their tips are located around the semiconductor chip mounting portion, and outer leads 2 connected to the inner leads 1 via tie bars 3. And a die pad 6 as a semiconductor chip mounting portion made of a copper plate having a large thickness and good heat dissipation, both of which are fixed via a double-sided tape T made of an insulating polyimide tape. ing.

Next, a method of manufacturing this lead frame will be described.

First, as shown in FIG. 3 (a), a normal lead including an inner lead 1, an outer lead 2, a tie bar 3 and the like, which is processed by a normal stamping method to process a band-shaped material and faces the semiconductor chip mounting area a. The frame body 5 is molded. 7 is a sidebar.

Next, as shown in FIG. 3 (b), coining treatment is performed on the tip region of the inner lead, leaving the tip of the inner lead, and a flat width of the bonding area at the tip of the inner lead 1 is secured. Plating (plating surface M) is performed. M indicates a silver-plated surface. At this time, if necessary, an insulating tape may be attached and fixed so as to avoid the bonding area at the tip of the inner lead.

On the other hand, as shown in FIG. 3C, a copper plate having a good heat dissipation property is processed by a normal stamping method, and the die pad 6 is punched out.

After that, as shown in FIG. 3 (d), the inner lead 1 is placed so that the concave side is in contact with the heat block H, and the die pad 6 is further laminated on the upper layer via the double-sided tape T and heated. By doing so, the lead frame body 5 is fixed to the die pad 6.

In this way, the lead frame as shown in FIGS. 1 and 2 is completed.

After that, the semiconductor chip is mounted and wire bonding is performed, and resin sealing is performed to complete the device.

According to this lead frame, as shown in FIG. 3 (d), even in the heating step of fixing the lead frame body 5 and the die pad 6 to each other, the heat block H is plated with the plated surface M.
Since they can be favorably supported and fixed without contact with each other, the manufacturing yield is improved.

Further, even during transportation, the plated surface does not come into contact with the heater block or the guide portion, and the plated surface is not scratched or foreign matter is attached.

Although the lead frame body and the die pad are separately formed in the above embodiment and the lead frame for wire bonding is connected to each other, it is also effective for a normal wire bonding lead frame in which the die pad is integrally formed. In addition to the above, the lead frame body having the inner leads is laminated on the first conductive plate made of a copper plate that plays a role of a ground plate and the upper layer, and is connected to the power supply line as a power plate made of a copper plate. It is also applicable to those which are welded to the two conductive plates so as to achieve the electrical connection between them.

〔The invention's effect〕

As described above, according to the method of the present invention, the coining area is slightly shifted to the outer lead side, and the wall thickness of the tip end portion of the inner lead is kept the same as the other areas. Since it is fixed to the die pad, the plated surface can be fixed without coming into contact with the supporting portion such as the heat block, and the mounting manufacturing yield is significantly improved.

In addition, there is no defect such as peeling of plating during transportation.

[Brief description of drawings]

FIG. 1 is a diagram showing an inner lead of a lead frame of an embodiment of the present invention, FIG. 2 is an overall view of the lead frame, and FIGS. 3 (a) to 3 (d) show a mounting process of the lead frame. FIG. 4 and FIG. 4 are views showing a part of the mounting process of the lead frame of the conventional example. 1 ... Inner lead, 2 ... Outer lead, 3 ...
Diver, M: silver plating area, 5: lead frame body, 6: die pad, 7: side bar, T: polyimide tape.

Claims (1)

[Claims] 1. A step of forming a lead frame main body comprising a plurality of inner leads arranged so that their tips are located at the periphery of a semiconductor chip mounting area, and outer leads connected to each of the inner leads. A thinning step of forming a thinned region at a position spaced a predetermined distance from the tip of the inner lead to the outer lead side, and a plating step of applying a precious metal plating to the concave surface formed by this thinning step, The inner lead is placed so that the concave side is in contact with the heat block, and a semiconductor chip placing portion for mounting a semiconductor chip is further laminated on this upper layer via a double-sided tape, and the leads are heated. A method of manufacturing a lead frame, characterized by including a fixing step of fixing the frame body to the semiconductor chip mounting portion. .