JPS63105996A - Surface treatment of metallic bar - Google Patents

Abstract

PURPOSE:To form a metallic film which does not tarnish for a long time on the surface of a metallic bar by continuously feeding and plating, then rolling the bar. CONSTITUTION:A metallic bar 1 is continuously pretreated by electrolytic alkali degreasing in a degreasing tank 2 and pickling in a pickling tank 3. The pretreated bar 1 is fed to a plating cell 4 and plated to form a metallic film. The plated bar 1 is washed in a washing tank 5, sent to a drier 7 and dried. The thickness of the bar 1 is then measured with a thickness gauge 8, rolling oil is adhered to the surface of the bar 1 and the bar 1 is rolled under pressure controlled according to the measured thickness. The rolled bar 1 is sent to a degreasing tank 10 and degreased with an org. solvent to remove the rolling oil. Thus, a metallic film capable of preventing tarnish is formed on the surface of the bar 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for surface treatment of a metal strip used as a lead frame material of a semiconductor element, for example.

[Conventional technology]

Lead frame materials for semiconductor devices, which are used in many electronic devices, are generally formed into lead frames by punching or etching.

Ni plating is applied to the entire surface, and Ag plating is applied to parts of the dyno set in which the semiconductor chip is mounted and the leads to which the semiconductor chip is wire-bonded.

However, in recent years, attempts have been made to omit this Ag plating, and at the same time, so-called direct bonding technology, which uses thin Cu wires instead of thin wires of Au or Al, which are conventional wire bonding materials, has been actively developed. There is.

This direct bonding technology connects copper alloy base and Cu
This is a technology that directly joins thin wires, but some attempts have been made to use copper-coated materials such as phosphor bronze on the surface of copper alloy lead frame materials to improve the reliability of the joint. This is the current situation.

FIG. 2 is a process diagram showing a conventional continuous surface treatment method for coating this type of lead frame material with copper. In the figure, (1) is a metal strip, (2) is an alkaline electrolytic degreasing tank, (3) is an acid cleaning tank, (4) is a plating tank, (5) is a water washing tank, and (6) is a discoloration prevention treatment tank. , (7) is a drying device. In the conventional surface treatment method, a metal strip (1), which is a lead frame material rolled to a predetermined thickness, is continuously moved while being subjected to alkaline electrolytic degreasing in an alkaline electrolytic degreasing tank (2) and acid cleaning tank (3). After performing pretreatment such as acid cleaning in , plating is performed in a plating bath (4) to form a coat of a plated gold crown on the surface of the metal strip (1). In this case, between each treatment process, water is washed in a water washing tank (5), and finally, after undergoing discoloration prevention treatment in a discoloration prevention treatment tank (6) and drying in a drying device (7), it is coiled again. It was to be taken.

[Problem that the invention seeks to solve]

In the conventional surface treatment methods described above, even if anti-discoloration treatment is applied, the plating surface is made of precipitated gold crown particles with extremely high activity, so it discolors in a relatively short period of time.For example, copper plating Lead frame materials subjected to this treatment had a problem in that they had an adverse effect on direct bonding.

The present invention was made to solve these problems, and an object of the present invention is to provide a surface treatment method for gold crown strips that can form a coating that does not discolor for a long time.

[Means for solving problems]

The method for surface treatment of a metal strip according to the present invention is a method in which a metal strip is plated while being continuously moved, and then rolled.

In this invention, the metal strip serving as the base material includes a copper alloy used as a lead frame material, but is not limited thereto. In addition, the plating applied to this metal strip varies depending on each metal strip, such as copper plating, and generally it is a gold crown plating that is different from the base metal strip. Yes, it is done in the same way as before. Rolling is performed by applying rolling oil to the surface of the metal strip to cause plastic deformation.

[For production]

In the method for surface treatment of a metal strip of the present invention, the metal strip is plated while being moved continuously, and then rolled to perform surface treatment on the metal strip. In this case, after a highly active plating film is formed on the gold crown strip, rolling oil is applied to the plated metal strip within a very short period of time, and the plated metal strip is rolled with rolling oil blocked from air. Since plastic deformation is applied through processing, the extremely highly active state is lost, resulting in a stable surface state and preventing discoloration.

〔Example〕

FIG. 1 is a process diagram of a method for surface treatment of metal strips showing an embodiment of the present invention, and in the figure, (1) to (5) and (7) indicate the same or equivalent parts as in FIG. 2. . (8)
1 is a plate thickness meter that continuously measures the thickness of the plated metal strip (1) that is continuously running, and 9 is a rolling roll whose pressure is controlled based on the measured value of the plate thickness meter (8). be. (1
0) is a solvent degreasing tank, which has the role of immersing the metal strip (1) in an organic solvent to remove rolling oil adhering during rolling.

The method for surface treatment of metal strips involves first performing pretreatments such as alkaline electrolytic degreasing in an alkaline electrolytic degreasing tank (2) and acid cleaning in an acid cleaning tank (3) while continuously moving the metal strip (1). After that, a gold crown coating is formed by plating in a plating tank (4), and after washing in a water washing tank (5), drying is performed in a drying device (7). Following this process, the plate thickness is measured using a plate thickness meter (8), and while controlling the pressure based on the measured value, rolling oil is applied to the surface of the metal strip (1), and the rolling roll (9) is applied to the surface of the metal strip (1). ) and degreased with an organic solvent in a solvent degreasing tank (10) to remove rolling oil. In this case, the state in which the surface of the plating film is extremely highly active is limited to a very short period of time, and therefore the progress of diffusion between the plating metal atoms and the strip metal atoms can be completely ignored, and the plated strip material is then Compared to the rolling method, there is no change over time and a stable surface condition can be obtained.

According to experiments, a phosphor bronze strip (C5101R) with a thickness of 0.3 nm, which had been subjected to alkaline electrolytic degreasing and acid cleaning, was treated with copper in a cyanizing bath, generally known as a medium concentration bath, using the method illustrated in Figure 1. Plating was applied to 15 μm, and after drying, a 5 μm skin pass was performed using a rolling roll with a diameter of 250 nn, and when the rolling oil was removed by immersion in 1,1.1-trichloroethane, sufficient discoloration occurred when stored at room temperature. could be prevented.

By the way, in the above explanation, the case where a copper coating is formed on the surface of the lead frame material is described, but it goes without saying that it can also be applied to the case of forming a fully curved coating that is highly sensitive to discoloration. Furthermore, this does not preclude applying an appropriate discoloration prevention treatment during or after solvent degreasing. The rolling process may be performed by a skin pass of approximately several μm, and the object of the present invention can be achieved even if plastic deformation is performed at a large processing rate, as long as changes in the material strength and shape of the metal strip are within an acceptable range. be.

〔Effect of the invention〕

As explained above, this invention can prevent discoloration of the metal coating formed on the surface of the strip by a simple method of plating the strip while continuously moving it and then rolling it. There is an effect.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an embodiment of the present invention, and FIG. 2 is a process diagram showing a conventional surface treatment method for metal strips. In the figure, (1) is a metal strip, (4) is a plating tank, (
5) is a washing tank, (7) is a drying device, (9) is a rolling roll, and (10) is a solvent degreasing tank. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A method for surface treatment of a metal strip, characterized in that the metal strip is plated while being moved continuously, and then rolled. (2) The method for surface treatment of a metal strip according to claim 1, wherein the plating is made of a metal different from that of the metal strip.