Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Wire contact – lead – or bond
Patent
1990-11-19
1995-03-07
Hille, Rolf
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Wire contact, lead, or bond
257792, 174110SR, 174110N, 428458, H01L 2328, H01B 700
Patent
active
053961048
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates toga bonding wire, a method of manufacturing the same and a semiconductor device using the wire.
BACKGROUND ART
A bonding wire used in a manufacturing process of semiconductor devices has been composed of a conductive metal core wire material of, for example, gold (Au), copper (Cu), aluminum (Al) and the like in the form of a bare wire.
Therefore, when bonding pads of a semiconductor pellet are bounded to conductors to external output terminals such as inner leads of a lead frame using such wires, a problem of short-circuiting arises in such a case that a wire comes into contact with another wire, an inner lead, a tab or the like due to any reason such as poor bonding, resin flow in a resin mold type package or the like.
In particular, as a distance between a pellet and inner leads is increased in correspondence to the increase in the number of pins in a large scale integrated circuit (LSI), a length of a wire span must be increased. In this case, however, short-circuiting, faulty chip edges and mount touches and the like are more liable to be caused by a wire which is curled and comes into contact with an adjacent wire.
Consequently, it has been proposed to coat a bonding wire with an insulation film. For example, U.S. patent application Ser. No. 4,488,674 proposes to coat a bonding wire with a polymer resin material which has an insulating property and is thermally decomposed at a temperature of 200.degree. to 300.degree. C. and volatilized to prevent short-circuiting and the like. However, it is difficult to obtain resins having such properties, and further in a case of polyethylene terephthalate, a continuous bonding cannot be carried out due to wire break caused when a second bond is subjected to contact bonding, because it is a relatively brittle crystalline material, or in a case of polycarbonate, a bonding wire obtained after it has been coated with a film is naturally curled and thus it is difficult to process it by a high speed bonding machine and keep the positional accuracy thereof when it is processed at a high speed. As a result, at present, these materials are not practically used because of such a drawback that the workability of a bonding process is deteriorated, and the like.
Further, a new problem in practical use arises in that some of polymer resin materials used for coating a bonding wire is left between the bonding wire and a lead frame or bonding pads of a semiconductor pellet, or a piece of the coated resin broken by an impact produced when bonding is carried out cuts the bonding wire of gold or the like or injures it to cause wire cutting-off.
In general, a heat resistant insulation coating material includes resins called engineering plastics, and among them aromatic polyester has been found to be excellent in these characteristics [for example, Japanese Patent Kokai (Laid-Open) Nos. Sho 54-138056 and Sho 58-137905].
Nevertheless, generally known aromatic polyester resins are excellent in heat resistance, wear resistance, fire retardance, mechanical characteristics such as tensile strength and the like, impact resistance, and electric characteristics such as insulating property and the like, but it is poor in an extrusion processing property, and thus it has been very difficult to form a thin insulation film of uniform thickness on the circumference of a bonding wire by an electric wire coating method using an extruder. In addition, aromatic polyester resins whose extrusion processing property has been improved by modification or the like have a problem in that they have poor heat and wear resistances.
Further, there has been employed a method by which a resin material is dissolved in a proper solvent and coated to form an insulation film of uniform thickness on the circumference of a bonding wire. Since, however, aromatic polyester resins having high mechanical strength and heat resistance have high chemical resistance, a suitable solvent for it is not available and then it has been difficult to uniformly form a thin coating film
REFERENCES:
patent: 4486945 (1984-12-01), Aigoo
patent: 4488674 (1984-12-01), Egawa et al.
patent: 4497849 (1985-02-01), Hughes et al.
patent: 4678114 (1987-07-01), Egawa et al.
patent: 4821148 (1989-04-01), Kobayashi et al.
patent: 4926238 (1990-05-01), Mukai et al.
Hille Rolf
Nippon Steel Corporation
Ostrowski David
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