KR100234162B1 - Heat treatment method of semiconductor lead frame - Google Patents

Abstract

The present invention relates to a heat treatment method of a semiconductor lead frame.

A heat treatment method of a semiconductor lead frame forming a multi-plating layer on a predetermined portion of a semiconductor lead frame and heat-treating the multi-plating layer, the method comprising: washing the multi-plating layer; Drying to remove moisture remaining in the multiple plating layer; Heat-treating the multiple plated layer in a furnace in a vacuum state; and cooling the multiple plated layer in an atmosphere of a gas means.

According to the present invention, since the surface of the multiple plating layer of the semiconductor lead frame is subjected to high temperature heat treatment in a vacuum state and cooled in an inert atmosphere, hydrogen stress existing in the multiple plating layer can be removed when exposed to the air, thereby reducing internal stress. Therefore, the peeling phenomenon of the surface of the multiple plating layer does not occur.

Description

Heat treatment method of semiconductor lead frame

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method of a semiconductor lead frame, and more particularly, to a semiconductor lead frame having an improved heat treatment method after plating layer formation.

In general, a semiconductor lead frame is a core component of a semiconductor package together with a semiconductor chip, and serves as a lead connecting the inside and the outside of the semiconductor package and a support for supporting the semiconductor chip. Simultaneously plays the role of. Such a lead frame may exist in various shapes according to a method of densification, high integration, and substrate mounting of a semiconductor chip.

The lead frame is generally composed of a pad mounted with a chip, which is a memory device, to be kept in a static state, and an inner lead connected by wire bonding and an outer lead connected to an external circuit.

A leadframe having such a structure is usually made by a stamping process or an etching process.

Here, the stamping process is a method of manufacturing a lead frame by punching a thin material into a predetermined shape by using a press mold apparatus which is sequentially transferred, while the etching process is suitable for mass production using chemicals. As a chemical etching method for forming a product by corrosion, it is mainly applied to small quantity production.

The semiconductor lead frame having such a structure forms a semiconductor package through an assembly process with other components, for example, a chip, which is a memory device.

In the process of manufacturing such a semiconductor package, a semiconductor lead frame is obtained by forming a plating layer made of a metal such as copper or nickel and a multiple plating layer on which a palladium or palladium alloy layer is stacked.

Such plating methods are generally classified into electroplating, electroless plating, cathode spattering, vacuum deposition plating, and ion plating.

Among these, the electroplating method is a surface treatment method in which an adhesive metal coating is electrodeposited on a metal surface or a nonmetallic surface for the purpose of corrosion resistance, abrasion resistance, or decoration. Electroplating consists of two electrodes, an anode and a cathode, and an electrolyte between the two electrodes, from which an electron flows into one electrode through a metal conductor, which is an external electric circuit, and from the other electrode, the electron Flows into the electrical circuit. An electrode in which electrons are released to an external circuit, that is, an electrode in which an electrode reaction is an oxidation reaction, is called an anode. In contrast, an electrode in which electrons flow from an external ash, that is, an electrode in which an electrode reaction is a reduction reaction is called a cathode. .

This electroplating method can deposit metal cations dissolved in a solution on the surface of a plated object in a plated object such as a semiconductor lead frame serving as a cathode electrode. The metal cation is deposited in the form of a nucleus on the surface of the plated object. . This nucleus is unevenly deposited depending on the shape of the product, the current density and the concentration distribution of the metal cations dissolved in the solution. When nuclei are generated at a point on the surface of the object to be plated, metals grow around the nucleus, which is faster than nuclei are generated at adjacent points.

When forming the multiple plating layers of the semiconductor lead frame, gas or bubbles flow into the nucleus of the plating layer.

In particular, in the case of forming the palladium plating layer, since there is almost no electrode potential difference with hydrogen, hydrogen is adsorbed in a large amount during plating. The hydrogen adsorbed as described above increases the internal stress of the palladium plating layer, and causes a change in current density during plating, thereby causing the palladium plating layer to be partially peeled off due to an imbalance of internal stress. As a result, the wire leadability and the corrosion resistance of the semiconductor leadframe are greatly reduced due to the adsorbed hydrogen.

In order to solve this problem, after forming the multiple plating layers of the semiconductor lead frame, the harmful gas component is removed through the heat treatment process, and the crystal structure of the plating layer is rearranged to minimize the number of bubbles. This is done by placing the leadframe inside the furnace and heat treatment to a certain temperature.

However, in the conventional heat treatment process, the surface of the multiple plating layer of the semiconductor lead frame forms an oxide film by bonding with oxygen in the atmosphere. Since the diffusion path is blocked due to the oxide layer of the multiple plating layer, hydrogen remaining in the plating layer is prevented from escaping to the outside of the plating layer.

In addition, since the particles adsorbed after plating are carbonized during the heat treatment process, additionally, impurities are generated on the surface, so that the wire bonding property is greatly degraded, and the surface of the plating layer is easily scratched. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a heat treatment method of a semiconductor lead frame in which the heat treatment process after forming multiple plating layers of the semiconductor lead frame is improved.

1 is a block diagram schematically showing a heat treatment step according to the present invention.

In order to achieve the above object, the heat treatment method of the semiconductor lead frame of the present invention, in the heat treatment method of the semiconductor lead frame to form a multi-plated layer on a predetermined portion of the semiconductor lead frame, the heat treatment of the multi-plated layer, the multi-plated layer Washing the; Drying to remove moisture remaining in the multi-plating layer; Heat-treating the multi-plated layer in a vacuum in a furnace; And cooling the multi-plated layer in an atmosphere of gas means.

According to the present invention, the furnace further comprises the step of forming a low vacuum state before the heat treatment step, wherein the heat treatment zone (zone) in the furnace in the heat treatment step is preferably 20 to 50 centimeters.

Hereinafter, exemplary embodiments of a heat treatment method of a semiconductor lead frame according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically illustrating a heat treatment process performed after the multiple plating layers of the semiconductor lead frame according to the present invention are formed.

Referring to the drawings, in step S1, a predetermined multi-plating layer is formed on the semiconductor lead frame. At this time, the outermost plating layer of the multiple plating layer is a palladium plating layer.

Subsequently, in step S2, degreasing is performed in order to remove the coating film deposited on the surface of the plating layer in step S1. After degreasing, the hot water dryer blows hot air in order to remove the degreasing liquid remaining in the plating layer and completely removes moisture from the surface of the lead frame (step S3).

After the water is removed in step S3, heat treatment is performed for a predetermined time so that hydrogen remaining in the multiple plating layers of the semiconductor lead frame is released to the outside of the lead frame.

First, in order to form the atmosphere in the furnace in a vacuum state, in step S4, the furnace is preliminarily heated to a low state before the heat treatment. This is for the purpose of increasing the vacuum efficiency during the heat treatment. After the low vacuum state, the crystal structure of the plating layer is rearranged, the corrosion resistance is improved, and heat treatment is performed at a high temperature to prevent brittleness by hydrogen ions in advance (S5). In this case, a high frequency, a laser, a plasma, or the like may be used as a heat source. And, in order to heat-treat only the surface of the multiple plating layer of the semiconductor lead frame during heat treatment, the heat treatment zone in the furnace is set to about 20 to 50 centimeters.

After the harmful gas such as hydrogen gas introduced during the plating in step S5 is removed, the vacuum degree of the heat treatment zone is maintained for a predetermined time (S6). Subsequently, in step S7, the surface of the multiple plating layer of the semiconductor lead frame is cooled before being exposed to the atmosphere. At this time, the heat treatment process is completed by blowing gas means, for example, inert gas or air, to the surface so that the surface of the multiple plating layer of the semiconductor lead frame is not oxidized to form an oxide film.

As described above, the heat treatment method of the semiconductor lead frame of the present invention can obtain the following effects.

First, since the surface of the multi-plated layer of the semiconductor lead frame is subjected to high temperature heat treatment in a vacuum state and cooled in an inert atmosphere, the internal stress can be reduced because hydrogen gas existing in the multi-plated layer can be removed when exposed to air. Therefore, the peeling phenomenon of the surface of the multiple plating layer does not occur.

Second, since the multiple plating layers of the semiconductor lead frame do not generate impurities due to carbonization of impurities during the heat treatment process, corrosion resistance of the plating layer is improved and wire bonding properties are improved.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (5)

In the heat treatment method of the semiconductor lead frame to form a multiple plating layer on a predetermined portion of the semiconductor lead frame, the heat treatment of the multiple plating layer, Washing the multi-plated layer; Drying to remove moisture remaining in the multi-plating layer; Heat-treating the multi-plated layer in a vacuum in a furnace; and Cooling the multi-plated layer in an atmosphere of gas means. The method of claim 1, And further comprising forming a low vacuum state in the furnace before the heat treatment. The method of claim 1, The heat treatment zone in the furnace in the heat treatment step is 20 to 50 centimeters, characterized in that the heat treatment method of the semiconductor lead frame. The method of claim 1, After the heat treatment step, the heat treatment method of the semiconductor lead frame, characterized in that to maintain the vacuum degree of the heat treatment zone for a certain time. The method of claim 1, And said gas means comprises air or an inert gas.

Images