JPH05190718A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To form an inner lead part or the top of an inner lead accurately by etching by dissolving the burrs made by the boring of an outer lead by electrolytic polishing or chemical polishing or rounding projections. CONSTITUTION:For a lead frame 4, in a first place an outer lead 3 is bored in a thin metallic plate 9 with a mold by a press. The burrs left behind the extraction exist off course in all directions. Such burrs are all electrolytically polished so that they may not be noxious to the formation of a photoresist or etching. Hereby, damage or break places do not form in the photoresist film provided in the metallic plate, so an inner lead or the top of an inner lead can accurately be made by etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multi-pin lead frame with a high yield by using both pressing and etching.

[0002]

2. Description of the Related Art A semiconductor device has a semiconductor integrated circuit chip mounted on a pad portion (semiconductor mounting portion) of a lead frame,
Connect the terminals of the semiconductor integrated circuit chip to the inner leads of the lead frame with wires such as gold wire or aluminum wire, or directly connect the inner leads and the semiconductor integrated circuit chip and encapsulate them with resin or ceramic. Manufactured.

By the way, the semiconductor device is indispensable for electronic equipments applied to all industrial fields, and its technological progress is remarkable, and in order to respond to it, the semiconductor device is highly functionalized, highly integrated and miniaturized. This is very important.

Recently, lead frames having a number of pins of, for example, 100 or more have been manufactured. As the number of pins increases, the lead width and lead spacing decrease,
Above all, the width and spacing of the inner leads are extremely fine.

As one of manufacturing a multi-pin lead frame, a method using both punching by a press and etching is proposed. For example, Japanese Patent Publication No. 3-6663 discloses a method of manufacturing a lead frame in which the inner lead portion and the pad portion are formed by etching and the outer lead portion is formed by pressing. According to this, the advantages of both the fine etching action of etching and the high-speed and highly stable punching action by the press are obtained, and there is an effect that a lead frame having a large number of pins can be manufactured at a relatively low cost.

Japanese Unexamined Patent Publication (Kokai) No. 63-148667 discloses a method for manufacturing a lead frame in which an outer lead, a dam bar and a guide hole are punched by a press, and then the inner lead portion is formed by etching by positioning the guide hole as a reference. Has been done. This has the effect of obtaining the advantages of pressing and etching.

[0007]

The prior art has a corresponding effect. However, a part of the lead frame, for example, the outer lead portion is formed by pressing, and is then etched to form a fine structure inner lead portion. When etching, the outer lead part formed earlier is locally etched and the shape changes slightly, and uneven etching may also locally occur on the outer lead part side of the inner lead. is there.

If the outer lead portion and the inner lead portion have a non-uniform shape, a lead frame having a large number of pins, for example, more than 100 pins, has a minute gap between the inner lead tips, for example, 0.1 mm or less. Cause It is an object of the present invention to stably produce a multi-pin lead frame having excellent shape accuracy by using pressing and etching together without the above problems.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is to punch a metal thin plate by a press to form an outer lead portion, and electrolytically or chemically polish the metal thin plate punched with the outer lead to dissolve burrs or a protrusion thereof. Then, a photoresist film is provided on both surfaces of the thin metal plate, and at least the inner lead portion or the inner lead tip portion is formed by etching.

[0010]

In the present invention, the outer lead portion is punched by pressing, and the burr of the thin metal plate on which the outer lead portion is formed is electrolytically or chemically polished to dissolve or round the protrusions, and then a photoresist film is provided and etching is performed. Then, at least the inner lead portion or the inner lead tip portion is etched to manufacture a lead frame. At this time, since the outer leads are punched by the press in any direction with respect to the rolling direction (longitudinal direction) of the material metal sheet, the direction of the punch burr naturally exists in any direction, but the melting or protrusion Since the rounding is performed by electrolytic polishing or chemical polishing, it can be completely removed or rounded regardless of the direction of burrs, and the photoresist film provided after that is not damaged, and the outer leads are locally etched by etching. No carving occurs, and even if the inner lead portion has a fine structure, it is accurately formed according to a predetermined shape.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings based on an embodiment. In the drawings, 1 is a pad for mounting a semiconductor integrated circuit chip (hereinafter referred to as a chip), 2 is an inner lead, the tip of which faces the pad 1, and the other end is continuous with the outer lead 3.
Although the lead frame 4 in this embodiment is of the quad type, the present invention is not limited to this type and the present invention can be applied to the manufacture of various types of lead frames. A tie bar 5 integrally connects a plurality of inner leads 2 and an outer lead 3 is continuously formed on the outer side thereof. 6
Is a support bar that supports the chip 1, 7 is a side rail, and 8 is a guide hole.

The lead frame 4 is formed by pressing a metal thin plate 9 with an outer lead 3 by means of a mold (not shown).
Drill a part. When forming the outer lead 3 part, up to 6 parts of the support bar may be formed. It is also possible to pierce the tie bar 5 and the portion of the inner lead 2 that extends parallel to the outer lead 3 portion.

Although it is punched with high precision and high speed in a press, a punching burr A is formed in the metal thin plate 9 at a height of 4 to 7 μm, depending on the material. Since the outer lead 3 is bored in the surface of the thin metal plate 9 in any direction, the burr A is naturally present in any direction. In this embodiment, all of the punch burrs A are electrolytically polished so as not to be harmful to the formation and etching of the photoresist film.

The electrolytic polishing apparatus 10 is filled with an electrolytic solution such as sulfuric acid, phosphoric acid, perchloric acid, nitric acid, oxalic acid, chromic acid, hydrofluoric acid, etc. In the protruding burr A having the shape of a protrusion, the protrusion is first selectively subjected to an electrolytic action to be melted or the protrusion is rounded. Excessive electropolishing reduces the base metal of the thin metal plate 9, so overelectrolysis is avoided.

In the electropolishing, the electrolysis effect is exerted on the extraction burr A regardless of the orientation of the extraction burr A in the surface of the thin metal plate 9, so that the removal burr A is completely detoxified.

Even if the electrolytic polishing is replaced by chemical polishing, the burr A is similarly subjected to a strong chemical polishing action from the protruding end thereof, and the protruding end is melted or the protrusion is rounded.

Then, the photoresist 11 is applied to the thin metal plate 9.
Is provided on the entire surface, and the photomask pattern 12 of the inner lead 2, the pad 1, and the support bar 6 is exposed on the photoresist 11 in contact with the formation area of the lead pattern other than the outer lead 3 formed earlier.

Since the burrs A on the metal thin plate 9 where the outer leads 3 have been previously formed by pressing have been melted or rounded, when the photoresist 11 is provided, after that, during development and etching, and when the metal thin plate 9 is formed. No damage or tear during handling. Further, the photoresist 11 is densely adhered to the thin metal plate 9 with the projections removed, and the etching forming accuracy of the subsequent etching is improved.

Next, the photoresist 11 film is subjected to a development process, and the photoresist 11 film other than the region exposed through the photomask pattern 12 is removed to form an etching mask.

An etching solution is jetted and etched on the surface of the thin metal plate on which the etching mask is formed. The thin metal plate 9 is eroded by the etching, and in this embodiment, the inner lead 2, the pad 1 and the support bar 6 are formed, and the pattern of the lead frame 4 is completed. The used photoresist 11 film is dissolved and removed with a solvent.

In this embodiment, the photomask pattern 12 is used.
Formed the inner leads 2, the pads 1, and the support bars 6, but the present invention is not limited to this, and is formed non-parallel to not only all of the inner leads 2 but also the inner lead tips, for example, the outer leads 3, forming a radial pattern. It may be a photomask pattern of the existing portion. In this case, a part of the inner lead 2 is formed by pressing.

Positioning when manufacturing the lead frame 4 using both pressing and etching is facilitated by using a known guide hole 8 formed in the side rail 7 as a reference.

Next, the present invention is applied to the lead frame 4
A description will be given of an example of manufacturing. The test material is a 42% Ni alloy with a plate thickness of 0.10 mm. The outer leads 3 corresponding to the number of pins of 160 were punched and formed by a die using a press, and then electrolytic polishing was performed to melt and round the burr protrusions of the test material. The comparative material was not subjected to electrolytic polishing treatment and had burrs with a height of 4 to 6 μm. Next, a photoresist was provided, and the photomask patterns of the inner leads, pads, and support bars were exposed on the photoresist so as to be in contact with each other. As a result of investigating their shapes, in the method of the present invention, both the outer leads and the inner leads had good shapes, and the lead width and spacing were uniform and excellent. On the other hand, in the comparative material, the inner lead has a non-uniform shape and the outer lead has a local etched portion, which is a problem as a lead frame having an extremely large number of pins.

In the above embodiment, the manufacture of the quad type lead frame is described, but it can be applied to the manufacture of various lead frames such as a dual in-line type.

Further, plating may be applied between the pressing and the etching.

[0026]

According to the present invention, the outer lead portion is formed by pressing, and then the burr having the outer lead portion formed therein is dissolved or rounded by electrolytic polishing or chemical polishing.
For this reason, the outer lead part is drilled in all directions in the surface of the thin metal plate, and burrs are present in various directions.
All melts or the protrusions are rounded without any problems.
Thus, the photoresist film provided on the thin metal plate is not damaged or broken, and the inner lead portion or the inner lead tip portion can be accurately formed by etching even if it has a fine structure. Furthermore, there is no local erosion of the outer lead and there is no deterioration of shape. Thus, a multi-pin lead frame is stably manufactured by using both pressing and etching.

[Brief description of drawings]

FIG. 1 is a diagram showing a lead frame according to an embodiment of the present invention.

FIG. 2 is a diagram showing removal of burrs by an electrolytic polishing apparatus in one embodiment of the present invention.

FIG. 3 is a diagram showing a part of a photoresist and a photomask pattern of an inner lead according to an embodiment of the present invention.

[Explanation of symbols]

 1 Pad 2 Inner Lead 3 Outer Lead 4 Lead Frame 5 Tie Bar 6 Support Bar 7 Side Rail 8 Guide Hole 9 Metal Thin Plate 10 Electrolytic Polishing Device 11 Photoresist 12 Photomask Pattern

Claims (1)

[Claims] 1. A metal thin plate is punched out by a press to form an outer lead portion, and the metal thin plate punched with the outer lead is electrolytically or chemically polished to dissolve burrs or round the protrusions thereof, and then to both sides of the metal thin plate. A method for manufacturing a lead frame, comprising providing a photoresist film and forming at least the inner lead portion or the inner lead tip portion by etching.