JPH03209752A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To obtain a lead frame wherein plating metal does not attach on the tip side surface of an inner lead, by a method wherein, after a lead frame is wrought and plated, release agent is brought into contact with the lead frame in the state that a region to be plated is coated, and a plated layer attaching on the unnecessary part is exfoliated and eliminated. CONSTITUTION:By a stamping method, belt type material is wrought and molded in the shape of an ordinary lead frame including inner leads 4 facing a die pad 2, outer leads 8, a tie bar 7, etc. Through a coining process, a flat width of an inner lead tip is ensured and then the tip part is plated M. A lead frame wherein shaping and plating are finished in this manner is mounted on a plated layer releasing equipment, and the plated layers on unnecessary parts are exfoliated and eliminated. Said releasing equipment uses an electrolytic method; electric charges are generated by bringing an anode contactor 19 into contact with the lead frame; releasing liquid is sprayed via a cathode electrode 14; the negatively charged releasing liquid is supplied on the non-plated surface side of the lead frame.

Description

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

(Prior Art) Lead frames for semiconductor devices such as ICs and LSIs are formed by processing a metal band material into a shape using either a photoetching method or a press processing method, followed by a plating process.

Incidentally, as the density and integration of semiconductor devices become higher, the chip area and the number of lead bins increase, but there is a tendency for packages to remain the same as before or to become smaller.

Therefore, the distance from the tip of the inner lead to the package line becomes shorter.

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 tip of the inner lead may be deformed during transportation to the plating equipment, or as shown in Figure 4, plating metal such as silver (Ag) may adhere to the side surface of the tip of the inner lead, causing the plating area to overlap. Because the distance to the package line is short, migration occurs in the semiconductor device after mounting, causing short circuits between adjacent inner leads, which causes a decrease in reliability.

In order to solve these problems, by plating precious metal at a predetermined position on the strip material and then forming it, it is possible to prevent the plating metal from adhering to the side surface of the inner lead, and also to prevent the tip of the inner lead during the plating process. A method has also been proposed to prevent deformation.

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.

Therefore, a method of forming pilot holes for positioning prior to plating has been proposed, but this requires a stamping process to form the pilot holes, resulting in the need to perform stamping twice, which reduces productivity. There was a problem with it being bad. In addition, since the plated portion is stamped, it is easily damaged and has a problem of poor yield.

A method has also been proposed in which a protrusion is provided on the plating mask after molding using a normal method, and the protrusion is inserted between the inner leads to prevent the plating solution from entering the side surfaces of the inner leads. However, this method also has problems in that if the inner leads and the protrusions of the mask do not match, the inner leads are deformed, the mask deteriorates quickly, and the cost is high.

Furthermore, a method has been proposed in which the plating solution is jetted in a direction opposite to the plating solution injection direction to prevent the plating solution from entering between the inner leads. There is also the problem that control is difficult.

Furthermore, a method has been proposed in which the plating layer is formed thicker than a predetermined thickness, and then the entire surface is etched, and the plating layer adhering to the side surface is peeled off to restore the predetermined thickness. However, with this method, the plating thickness is not stable and the yield is poor.

Additionally, a method has been proposed in which a notch is added to the boundary of the plating area on the side surface of the tip of the inner lead to stop the plating solution from flowing out, but this method is also not reliable as the plating solution flows out beyond the notch. However, there is a problem in that the mechanical strength of the tip of the inner lead is extremely reduced due to the presence of the notch.

(Problems to be Solved by the Invention) As described above, with the increasing integration of semiconductor devices, the lead spacing is becoming smaller and smaller, and the adhesion of plating metal to the side surfaces of the tips of inner leads reduces the reliability of semiconductor devices. It was causing this.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a lead frame in which no plating metal adheres to the side surface of the tip end of the inner lead.

[Structure of the invention]

(Means for Solving the Problems) Therefore, in the present invention, after shaping the lead frame and plating it, a stripping agent is brought into contact with the lead frame while covering the area to be plated, and the plating layer adhering to unnecessary parts is peeled off. I'm trying to remove it.

(Function) According to the method of the present invention, the plating layer at the tip of the inner lead is contacted with the stripping agent while the plating region is coated, and the plating layer adhering to the unnecessary portion is peeled off. Therefore, special equipment is not required. It can be manufactured using normal equipment without the need for
It is extremely easy to obtain a lead frame with uniform plating thickness and no plating on the side surfaces of the inner leads.

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

FIG. 1(a) and FIG. 1(b) are main part views of a lead frame and its inner lead tip portion manufactured by the method of the embodiment of the present invention.

A uniform plating layer is formed in the plating area at the tip of the inner lead, and a good plating area is formed without any plating leakage to the side surfaces.

FIGS. 2 and 3 are diagrams showing the manufacturing process of the lead frame.

First, a strip-shaped material is processed by a stamping method and molded into the shape of a normal lead frame including inner leads 4, outer leads 8, tie bars 7, etc. facing the die pad 2. 1 is a sidebar.

Next, a coining process is performed to ensure a flat width at the tip of the inner lead, and then plating is performed on the tip. M indicates a plating area.

At this time, if necessary, an insulating tape may be attached via a thermosetting resin so as to avoid the bonding area at the tip of the inner lead, and cured and fixed through a heating process.

Thereafter, the lead frame which has been shaped and plated in this way is mounted on a plating stripping device as shown in FIG. 2, and the stuckness adhering to unnecessary parts is stripped off and removed. This plating stripping device uses an electrolytic method, and the container 10
Inside, tension roll 12 and drive roll 13
The lead frame 1 is caused to run, and the anode contactor 15 is brought into contact with the lead frame to charge it, and a stripping solution is injected through the cathode electrode 14 to apply the negatively charged stripping solution to the non-plated areas of the lead frame. I try to feed it to the side. In the container 10, as shown in FIG. 3, a back plate 11 made of silicon is pressed and pressed by a tension roll 12 to the plating surface side of the lead frame 1, so as to protect the plating area. It has become.

While the lead frame is running inside this plating stripping device,
Unnecessary material attached to the side of the tip of the inner lead is removed.
This results in a good lead frame with a uniform plating layer formed in the plating area.

The lead frame thus formed can be obtained without plating metal adhering to the side surfaces of the tips of the inner leads, making it possible to suppress the occurrence of migration.

Further, by simply adding a plating stripping step in which the plating is run through a plating stripping device after the plating step, the lead frame can be formed as is without changing normal lead frame manufacturing equipment, and it is possible to provide a highly reliable lead frame extremely easily. becomes possible.

In the above example, an electrolytic method was used to remove the plating, in which the stripping solution was sprayed while applying an electric charge. However, it is not necessary to use the electrolytic method. It goes without saying that other methods such as the method may also be used.

Furthermore, in the embodiment described above, the plating region was protected in the plating stripping process by bringing the plating region forming surface into close contact with the back plate, but other methods such as pasting tape may be used.

〔Effect of the invention〕

As explained above, according to the method of the present invention, the plating layer at the tip of the inner lead is contacted with the stripping agent while the plating region is coated, and the plating layer adhering to the unnecessary portion is peeled off. It is possible to extremely easily obtain a highly reliable lead frame with uniform plating thickness and no plating on the side surfaces of the inner leads without changing the manufacturing process.

[Brief explanation of drawings]

FIGS. 1(a) and 1(1) are diagrams showing a lead frame formed by the manufacturing method according to the embodiment of the present invention, and FIGS. 2 and 3 are diagrams showing the plating used in the method according to the embodiment of the present invention. FIG. 4 is a diagram showing a peeling device, and FIG. 4 is a diagram showing the tip of an inner lead of a lead frame formed by a conventional method. 1... Side bar 2... Die pad, 4... Inner lead, 7... Tie bar 8... Outer lead, 9... Support bar, M... Plating area, P
...Bay container line, 10...Container, 11...
・Back plate, 12...Tension roll, 13
... Drive roll, 14 ... Cathode electrode, 15
...Anode contactor. (b) Figure 1

Claims (1)

[Claims] A method for manufacturing a lead frame comprising: a plurality of inner leads extending from the periphery of a semiconductor element mounting portion at predetermined intervals; and outer leads connected to each inner lead. The method includes a plating step of plating a region to be plated including the tip of the inner lead, and a stripping step of bringing a stripping agent into contact with the region to be plated in a state where the region to be plated is coated to peel off and remove the plating layer adhering to unnecessary parts. A method for manufacturing a lead frame, characterized in that: