JP2727251B2 - Lead frame and manufacturing method thereof - Google Patents

Description

The present invention relates to a lead frame and a method of manufacturing the same, and more particularly, to a lead frame having a high-density lead arrangement plated with palladium.

(Prior art) Lead frames for semiconductor devices such as ICs and LSIs are formed by removing unnecessary portions of 0.25 mm or 0.15 mm metal thickness by either photo-etching or pressing. After processing, it is formed through a plating step of plating a predetermined portion, a taping step of attaching a tape and fixing the inner leads to each other, and the like.

By the way, in recent years, the lead interval and the lead width have been decreasing with the increase in the degree of integration of the semiconductor device, and the improvement of the processing accuracy has become a major problem. Furthermore, surface mounting technology for connecting the tip of the outer lead to a wiring pattern formed on the surface of the mounting board is becoming popular.In this case, palladium plating is also applied to the outer lead to reduce solder adhesion. In addition to being good, the bonding area at the tip of the inner lead has an advantage that the bonding property can be improved by applying palladium plating.

Further, since the palladium plating layer is hard, sufficient strength can be given even to a thin lead frame, and there is no limitation to a base material.

However, after molding, the tie bar must be cut off, and the base material of the lead frame is exposed at the cut section, which causes rust.

Therefore, it is desirable to use a lead frame structure without tie bars.However, as the density of the lead frame continues to increase, the mechanical strength decreases when the plate thickness is reduced. There has been a problem that damage such as breakage or bending is apt to occur due to insertion or removal of pins, and the yield and reliability of the lead frame are reduced. In addition, when a lead frame without tie bars is used, there is a problem in that the yield and reliability of the lead frame are reduced, such as the possibility of the inner lead being raised or lowered, which lowers the accuracy of wire bonding. Was.

(Problems to be Solved by the Invention) As described above, with higher integration of semiconductor devices, lead intervals and lead widths have been decreasing, and improvement in processing accuracy has become a major problem. However, the base material of the lead frame is exposed on the cross section of the cut portion of the tie bar, which causes rust.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a lead frame that is easy to manufacture, has high accuracy, and has high reliability while maintaining the position between leads without rust. I do.

[Configuration of the invention]

(Means for Solving the Problems) Therefore, in the lead frame of the present invention, a plurality of outer leads extending inward and a plurality of inner leads connected to the outer leads and extending toward the vicinity of the semiconductor element mounting portion are provided. And a lead frame having the entire surface of the lead frame coated with a palladium or palladium alloy plating layer, and instead of a diver as a fixing member for connecting and fixing between adjacent outer leads, between adjacent inner leads and between adjacent inner leads. An insulating tape as a fixing member for connecting and fixing the outer leads is adhered.

Preferably, the lead frame is a surface mounting lead frame for fixing the outer lead tips in parallel with the surface of the mounting substrate, and the fixing member for connecting and fixing the outer leads is located near the tips of the outer leads. And is disposed so as to be parallel to the mounting substrate.

Further, in the method for manufacturing a lead frame according to the present invention, the plurality of outer leads extending inward and the plurality of inner leads connected to the outer leads and extending toward the vicinity of the semiconductor element mounting portion are separated from each other by the inner leads. The first to process the shape while leaving the connecting piece to connect and fix the space
Shape processing step, a plating step of plating the entire lead frame surface with palladium or palladium alloy, a fixing step of fixing the adjacent inner leads or outer leads with insulating tape, and the inner lead tip portion And a second shape processing step of separating the tip of the inner lead by removing a connecting piece for connecting the inner lead.

Here, the outer lead refers to a lead area outside the package line.

(Operation) According to the above configuration, since there is no tie bar, there is no danger of rusting due to exposure of the base material in the tie bar cutout area, and a lead frame with good solder adhesion and high bonding property can be obtained even during mounting. It becomes possible.

In addition, since the mutual positions are maintained with high accuracy by the insulating tape instead of the tie bars, high-precision surface mounting can be directly performed. Further, since the outer leads are formed so as to be thin, bending is easy.

In addition, since a highly accurate position is maintained during transportation and positioning between steps and during the step, a highly reliable lead frame can be obtained.

Also, at the time of attaching the insulating tape, the temperature must be raised to 180 ° C or higher, but in the case of solder plating, it melts at 180 ° C or higher, and tends to flow and cause a defect such as a short circuit with an adjacent lead. When palladium (Pd) or palladium alloy plating is used, it is well maintained without melting.

Furthermore, if the connecting piece is left at the tip of the inner lead and the shape is processed, and the position between the inner leads is fixed using an insulating member before cutting the connecting piece, the lead spacing can be maintained well. Thus, the bonding property can be improved.

As described above, according to the configuration of the present invention, since the outer leads of the lead frame are formed of thin plate members, they are easy to bend and are extremely effective for surface mounting, but are liable to be deformed. In addition, palladium plating enhances the reinforcing effect, and overcomes the problem by fixing two places between the inner leads and between the outer leads with an insulating tape.

In addition, when attaching the insulating tape, the temperature must be raised to 180 ° C or higher, but since palladium plating is used, it does not melt as in the case of solder plating, it is maintained well, and the bonding property is enhanced. be able to.

In addition, if the tip portion of the outer lead, which requires the highest positional accuracy in surface mounting, is fixed, the reliability becomes higher.

Also, if an insulating tape is arranged near the package line, the flow of the mold resin can be stopped more favorably.

According to the method of the present invention, at the tip of the inner lead,
It is processed leaving the connecting piece that keeps it in the initial state, and in this state, the tip of the inner lead and the outer lead are reinforced with insulating tape, but the palladium plating does not melt out and is fixed well. By separating the tip of the inner lead in a state where the inner lead is reinforced at two points, it is possible to obtain a lead frame with high positional accuracy while using an extremely thin material.

 Further, processing is easy, and there is no decrease in dimensional accuracy.

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

A lead frame according to an embodiment of the present invention is a lead frame without tie bars as shown in a plan view in FIG. 1 (a) and a cross-sectional view taken along the line AA in FIG. 1 (b). And the inner lead 12
In addition, a polyimide tape 18 is attached to a predetermined area of the outer lead 14.

That is, the inner leads 12 around the die pad 11
Are arranged radially and connected by a polyimide tape 18, and outer leads 14 are connected to the respective inner leads.The outer leads are also connected by the polyimide tape 18 and the ends are supported by side bars 15, 16. ing. Here, 17 is a support bar.

A palladium plating layer m is formed on the inner lead surface of the lead frame and the back surface of the outer lead.

Next, a method for manufacturing the lead frame will be described.

First, as shown in FIG. 2 (a), a metal strip material designated as an alloy 42 is mounted on a progressive die and pressed to form an inner lead having a desired shape (the tip surface is Excluded) 12, a first punched area A1 for forming the outer leads 14 and the like is sequentially formed, and the inner lead portions, the outer lead portions, and the like are patterned except for the tip surface of the inner leads.

Thereafter, a predetermined region is punched out sequentially, and the tie bar T is left at the tip of the inner lead.
The patterning of 12 and the outer leads 14 is completed.

Subsequently, a nickel plating layer having a thickness of 1 μm and a thickness of 0.
After a plating step of forming a palladium plating layer m of 3 to 0.5 μm, as shown in FIG. 2B, a polyimide tape for fixing the inner leads and the outer leads
Stick 18 on.

Thereafter, as shown in FIG. 2 (c), the second punched area A2 (cavity area) at the end of the inner lead left in the above step is punched out, the tie bar is cut off, and the die pad is removed.
11 is separated from the tip of the inner lead, and the processing of the lead frame is completed.

In the lead frame thus formed, the semiconductor chip 20 is connected to the die pad 11, the resin is sealed through a wire bonding process, the side bars 15 and 16 are cut off, and the surface as shown in FIG. The outer leads are bent for mounting, positioned on the wiring pattern of the mounting substrate, and fixed by heating the mounting substrate side.

In this way, a semiconductor device having outer leads formed at high density can be mounted very easily and with high reliability.

In particular, since the tie bar is not used, there is no tie bar cut surface, and there is no possibility that rust is generated by exposing the lead frame base. The inner leads are palladium plated on the surface and reinforced with polyimide tape, and the outer leads are palladium plated on the entire surface, including the mounting surface, and the opposite side of the mounting surface is reinforced with polyimide tape. Therefore, surface mounting can be realized very easily and reliably.

Also, the lead frame thus formed is
Since the material is reinforced by hard palladium plating, the starting material for the pressing step can be made thinner, and thus a lead frame with less distortion can be obtained. Therefore, it is possible to obtain a lead frame with less deformation even after a heating step in a subsequent step.

Furthermore, since the connection piece is left at the tip of the inner lead, the shape is processed, and prior to the cutting of the connection piece, a fixing step of fixing the positions between the inner leads using a polyimide loop is included, so that the lead interval is improved. It is possible to maintain and improve the bonding property.

In the embodiment, since there is no tie bar, there is a possibility that the resin may flow out at the time of resin sealing. However, it is possible to prevent the resin from flowing out by forming a projection on the mold.

In the above embodiment, plating was performed after punching the region between the inner leads.However, prior to the step of punching the region between the inner leads, palladium plating was performed on a region corresponding to the tip of the inner lead including the element mounting region. It may be performed, and by doing so, it is possible to prevent the plating metal from adhering to the entire inner lead or outer lead side portion,
The prevention of the reduction in dimensional accuracy is complete.

In the above-described embodiment, the position where the polyimide resin is adhered can be changed as appropriate.

In this case, as shown in FIGS. 4 (a) and 4 (b), the polyimide tape 18 may be formed only at the tip of the inner lead, or the palladium plating layer m may be formed on the entire surface of the lead frame. In this case, since it is sufficient to form each of them on one entire surface, the formation is extremely easy.

Further, as shown in FIG. 5, the polyimide tape 18 may be adhered to the position of a normal tie bar.

In addition, the lead frame material is not limited to the alloy 42, and another material such as copper may be used.

〔The invention's effect〕

As described above, according to the present invention, at least the outer lead surface of the lead frame is covered with a palladium (Pd) or palladium alloy plating layer, and instead of the tie bar, between the adjacent inner leads or between the adjacent outer leads. Since an insulating tape as a fixing member to be connected and fixed is attached, it is possible to obtain a lead frame with high accuracy, high reliability, and easy mounting.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are views showing a lead frame according to an embodiment of the present invention, FIGS. 2 (a) to 2 (c) are views showing manufacturing steps of the lead frame, and FIGS. FIG. 3 is a perspective view of a semiconductor device formed using the lead frame of the embodiment of the present invention, and FIGS. 4 and 5 are views showing a lead frame of another embodiment of the present invention. 11 ... Die pad, 12 ... Inner lead, 13 ... Dumb bar, 14 ... Outer lead, 15,16 ... Side bar, 1
7 ... Support bar, 18 ... Polyimide tape, T ...
Tie bar, m: plating layer.

Claims (3)

(57) [Claims] 1. A lead frame, comprising: a plurality of outer leads extending inward; and a plurality of inner leads connected to the outer leads and extending toward a vicinity of a semiconductor element mounting portion. The entire surface is covered with a palladium or palladium alloy plating layer, and instead of a diver as a fixing member for connecting and fixing between adjacent outer leads, insulation as a fixing member for connecting and fixing between adjacent inner leads and between adjacent outer leads is used. A lead frame to which a conductive tape is adhered. 2. The lead frame according to claim 1, wherein the lead frame is a surface mounting lead frame in which a distal end portion of an outer lead is arranged and fixed in parallel with a surface of a mounting substrate, and a fixing member for connecting and fixing the outer leads is formed of the outer lead. 2. The lead frame according to claim 1, wherein the lead frame is arranged near the tip so as to be parallel to the mounting substrate. 3. A connecting piece for connecting and fixing a plurality of outer leads extending inward and a plurality of inner leads connected to the outer leads and extending toward a vicinity of a semiconductor element mounting portion between the inner leads. A first shape processing step of forming a shape while leaving a lead, a plating step of performing palladium or palladium alloy plating on the entire surface of the lead frame, and fixing between adjacent inner leads or outer leads with an insulating tape. Removing the connecting piece connecting the tip of the inner lead,
A second shape processing step of separating the tip of the inner lead.