JPH03185855A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To prevent the adhesion and positional deviation of a plating metal to the side faces of inner leads at their leading ends by plating the metal in a state where the inner leads are coupled with each other near the areas to be plated at their leading ends and forming the leading end sections of the inner leads after the plating. CONSTITUTION:Outer leads, etc., are formed by punching areas other than the areas between each inner lead 4 at the leading end sections of the inner leads including the areas which become plating areas M at the leading end sections of the leads facing die pads 2, with the areas left un-punched being used as coupling pieces 5. The areas used as the coupling pieces 5 are larger than the plating areas M. Therefore, leakage of a plating liquid to the side faces of the leads at their leading ends can be prevented completely. The plating is performed after coining treatment is performed and flat widths are secured at the leading end section of the leads. Then the leading end sections are punched and the pieces 5 are removed so as to separate the leading ends of the leads from each other. Therefore, the inner leads make no deformation even when the widths of the leads are narrow and no sufficient strength is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a lead frame, and particularly to a method for processing the tip portion of an inner lead thereof.

(Prior Art) Lead frames for semiconductor devices such as ICs and LSIs are formed by shaping a metal strip-shaped material by either photo-etching or press processing.

Incidentally, as the density and integration of semiconductor devices become higher, the number of lead bins increases, but packages tend to remain the same or become smaller.

As the number of inner leads increases within the same area, the width of the inner leads and the distance between adjacent inner leads naturally become narrower. Therefore, deformation of the inner leads due to a decrease in strength and short circuits between the inner leads due to the deformation may occur.

Furthermore, in order to improve bonding properties, the tip of the inner lead and the semiconductor element mounting portion are often plated with noble metal.

For this reason, the tips of the inner leads may be deformed during transportation to the plating equipment, and plating metal such as silver (Ag) may also adhere to the side surfaces of the tips of the inner leads, causing migration in the semiconductor device after mounting. This caused a decrease in reliability.

In order to solve this problem, a method has been proposed in which plating is performed while the inner leads are connected by a connecting piece provided on the end face of the inner lead, and after plating is completed, the connecting piece is removed and the inner lead is divided. has been done.

As an example of this method is shown in FIG. 2, a die pad 2 for mounting a semiconductor element, a tip end extending so as to surround the die pad, and an end surface of the die pad 2 are provided with an end face connecting piece 3.
A large number of inner leads 4 integrally connected by a tie bar 7 extending in a direction substantially perpendicular to the inner leads and integrally supporting these inner leads, and a tie bar 7 connected to each of the inner leads on the outside of the tights. The shape is processed to include the outer lead 8 and the support part 9 that supports the dieper/sod 2, and after a process such as a plating process, the connecting piece is drawn along the broken line C.
In this method, the inner leads are cut out and the inner leads are separated from each other. In FIG. 2, 1 is a sidebar.

However, although this method can prevent the tip of the inner lead from deforming during the plating process, since the side surface of the tip of the inner lead has already been formed and is exposed during the plating process, plating on the side surface of the inner lead may occur. There is a problem in that metal adhesion cannot be prevented from IE.

Further, in this method, only the end surfaces of the tips of the inner leads are connected by the connecting pieces, so there is a problem that support is insufficient.

Therefore, we also developed a method in which the strip material is plated with a precious metal at a predetermined position and then molded to prevent the plating metal from adhering to the side surface of the inner lead, as well as to prevent the tip of the inner lead from deforming during the plating process. has also been proposed.

However, in this method, expensive precious metal plating is applied and then stamping is performed in a predetermined shape, so if a stamping failure occurs, the precious metal plating is completely wasted, causing a rise in costs.

Furthermore, in this method, since plating is performed on a band-shaped material with an incomplete shape, it is difficult to confirm the positional shift, and there is a risk that a large number of defective products will be produced.

(Problems to be Solved by the Invention) As described above, as semiconductor devices become more highly integrated, the lead spacing is becoming smaller and smaller, leading to problems such as adhesion of plating metal to the side surfaces of the tips of the inner leads and misalignment of the tips of the inner leads. However, this has caused a decrease in the reliability of semiconductor devices.

The present invention has been made in view of the above-mentioned circumstances, and aims to improve the reliability of semiconductor devices by preventing plating metal from adhering to the side surfaces of the tips of inner leads, as well as preventing displacement of the tips of the inner leads. purpose.

[Structure of the invention]

(Means for Solving the Problems) Therefore, in the present invention, after molding the other areas except for the vicinity of the plating area at the tip of the inner lead, the tip of the inner lead is molded while the tip of the inner lead remains connected. Plating is performed on the area to be plated, including the area to be plated, and finally the tip of the inner lead is molded.

(Function) According to the method of the present invention, plating is performed with the region to be plated at the tip of the inner lead connected as it is, and the tip of the inner lead is shaped after plating. Since the side surfaces of the tips of the inner leads are not exposed to the surface, there is no risk of plating metal adhering to them.

In addition, because the area near the plating area at the tip of the inner lead is connected as it is, plating and other treatments are performed, and then the tip of the inner lead is molded, so the lead width of the inner lead is narrow and sufficient strength cannot be achieved. Even in a lead frame that cannot be obtained, the original position can be maintained without deformation.

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

FIG. 1(a) to FIG. 1(c) are diagrams showing the manufacturing process of a lead frame according to an embodiment of the present invention.

First, as shown in FIG. 1(a), a strip-shaped material is processed by a stamping method, and between the inner leads in the tip region including the region that will become the plating region M at the tip of the inner lead 4 facing the die pad 2. The area is left as it is as the connecting piece 5, only the other area is punched out, and a part of the inner lead, the outer lead, the tie bar, etc. are formed into a bottom mold.

The area where this connecting piece 5 is left is made to be larger than the plating area M, sufficiently including the area that will become the plating area M.

By doing so, it is possible to completely prevent the plating solution from leaking to the side surface of the tip of the inner lead.

Next, after performing a coining process to ensure a flat width at the tip of the inner lead, as shown in FIG. 1(b),
Plating is performed on the tip. M indicates a plating area. At this time, if necessary, an insulating tape coated with thermosetting resin is pasted to avoid the bonding area at the tip of the inner lead, and cured through a heating process.
It may be fixed.

Thereafter, as shown in FIG. 1(C), the tip of the inner lead is punched out, the connecting piece 5 is removed, and the tip of the inner lead is separated.

In the lead frame formed in this way, plating is performed while the vicinity of the plating area M at the tip of the inner lead 4 is connected as it is, and after plating, the tip of the inner lead is molded. Since the side surface of the tip of the inner lead is not exposed to the surface, the side surface of the tip of the inner lead can be obtained without plating metal adhering to it, and the occurrence of migration is suppressed.

In addition, the area near the plating area M at the tip of the inner lead is connected as it is during the plating process, and then the tip of the inner lead is molded, so the lead width of the inner lead is narrow and sufficient. Even in lead frames that do not have sufficient strength, the original position can be maintained without deformation.

In addition, as mentioned above, if the tips of the inner leads are reinforced with insulating tape before being molded, the mutual positional relationship can be further maintained.
Not only short circuits between the leads are prevented, but also short circuits with the bonding wires are prevented, resulting in extremely high reliability.

〔Effect of the invention〕

As explained above, according to the method of the present invention, plating is performed while the vicinity of the plating area at the tip of the inner lead is connected as it is, and the tip of the inner lead is molded after plating. There is no risk of plating metal adhering to the side surface of the tip of the inner lead, and the lead width of the inner lead is narrow when increasing the density.
Even in a lead frame that does not have sufficient strength, the original position can be maintained without deformation, and the manufacturing yield is significantly improved.

[Brief explanation of drawings]

1(a) to 1(c) are diagrams showing the manufacturing process of a lead frame according to an embodiment of the present invention, and FIG. 2 is a diagram showing a part of the manufacturing process of a conventional lead frame. 1... Side par 2... Die pad, 3... End face connection piece, 4... Inner lead, 5... Connection piece,
7... Tie bar 8... Outer lead, 9...
Support bar M...Plating area. 0') Dimension 0 Σ U)

Claims (1)

[Scope of Claims] A semiconductor device mounting portion, a plurality of inner leads extending at predetermined intervals from a periphery of the semiconductor device mounting portion, and an outer lead connected to each inner lead, respectively. A lead frame manufacturing method for processing the shape of a lead frame, which includes: a first molding step of shaping an area other than a region to be plated at the tip of the inner lead; A method for manufacturing a lead frame, comprising: a plating step for plating a region; and a second molding step for molding the tip of the inner lead.