JPS59200788A - Striking method - Google Patents

Abstract

PURPOSE:To improve the adhesive strength of a film formed by striking on a material with inferior suitability to electrodeposition by forming a film at a high current density in a short time in the early stage of striking and by carrying out striking at a low current density for a prescribed time. CONSTITUTION:When a metal with inferior suitability to electrodeposition such as Rh is subjected to Au striking, Au striking is carried out on Rh at >=3A/ dm<2> high current density for a short time, and the striking is continued at about 0.2A/dm<2> low current density. The resulting Au layer is electroplated with Au by a conventional method to form an Au layer. Since the under Au layer with superior adhesive strength is formed even on Rh with inferior suitability to electrodeposition, the upper Au layer is not stripped from Rh.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a 1-like plating method, and more specifically, plating is performed at myoelectric/M density at the initial stage of plating to form a plating film in a short time, and thereafter, a low current The present invention relates to a strike plating method that can form a plating film with excellent adhesion and appearance even on a plated object with poor electrodepositivity by changing the density.

In recent years, functional plating has increasingly become multilayered with a plurality of platings, such as by providing an intermediate layer as a barrier on the base material 11. However, some of these materials or base platings have poor adhesion to the target plating deposits on the upper layer, and often do not function satisfactorily after plating. For this reason, the processing steps before and after plating have become more complicated, and workability has also decreased. When plating is applied to such a material that is often electrodepositable, or in other words, a base plating, strike plating is usually applied to improve adhesion before transferring to a multilayer structure.

However, even with this strike plating, since conventionally it was carried out at a constant current density, there were drawbacks such as poor adhesion, poor appearance, and poor workability. To explain this in the case of applying gold strike plating on rhodium plating, Figure 1 is a potential one-hour curve diagram, and in the same figure, curves 1 and 2 are respectively current density 3
A/ljm', 0.2A/dm'' shows the potential change over time when plating is performed, and A and B are the points at which the potential becomes constant under each condition, that is, when the entire surface of the object to be plated is gold plated. This shows the point at which the coating reaches point A. When S1H-like plating is performed under the conditions of curve 1, the time to reach point A is as short as 6 to 7 seconds, so the adhesion is good, but 10 seconds Plating over this period will result in discolored plating, and as strike plating requires plating for more than 30 seconds due to various constraints, the plating will become particularly severe.
Thin plating has the disadvantage of impairing the appearance.

On the other hand, if it is performed under the conditions of curve 2, it will not show a good appearance, or it will take a long time to reach a stable potential, about 20 seconds, and the plating will take a long time to develop, causing blistering and peeling, and poor adhesion. There are some difficulties.

The present invention has been made in view of the above-mentioned drawbacks, and its purpose is to provide a method for electrodepositing rhodium, etc., even if the electrodepositability is above 4A.
The purpose of this method is to provide a strike plating method that can perform plating without impairing adhesion (and appearance).The feature is that in strike plating on objects with poor electrodepositivity, plating can be performed at a high current density in the early stage of plating. The process involves forming a plating film on the surface of the object to be plated in a short time, and then switching to a low current density and plating for a predetermined period of time.

The present invention operates at a high current density at point A in FIG. 1, that is, until the entire surface of the object to be plated is covered with a plating film.
Plating is performed under the conditions of a certain curve 1 at a high current density of about 0.2 A/dm2, and thereafter plating is continued at a low current density of about 0.2 A/dm2, that is, under the conditions of curve 2. A time-current density diagram in this case is shown in FIG. FIG. 3 shows a state diagram of plating applied to a ceramic package housing a semiconductor element. In the figure, 10 is a gold actual plating layer, 12 is a gold strike layer deposited by low current density, 14 is a gold strike layer deposited by high current density, 16 is a rhodium plating layer, 18 is a nickel plating layer, and 20 is a gold strike layer deposited by high current density. Tungsten metallized layer 22 is a ceramic substrate. Table 1 shows the wire bond peel test results.

Table 1 After heating at 200° C. for 50 hours, 30 μm ψ aluminum wires were ultrasonically bonded and the number of pieces peeled off was examined.

From Table 1, the adhesion of gold to rhodium is significantly improved.
You can see that it is empty.

The method of the present invention is particularly effective for strike plating on materials to which gold plating and the like are difficult to electrodeposit, such as rhodium, molybdenum, stainless steel, aluminum, and di-Nokel-plated tungsten metallized layers.

As described above, according to the strike plating method of the present invention, a plating film is formed over the entire surface of the object to be plated in a short time using a high current density in the early stage of plating, so that the surface of the object to be plated is not roughened by the plating solution. , impurities do not stand out and the adhesion is extremely excellent, and since the current density is switched to a low current density thereafter, there is no possibility of discoloration (it is highly effective in that a dense plating surface with an excellent appearance can be obtained).

Although the present invention has been variously explained above with reference to preferred embodiments, the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. It is.

[Brief explanation of drawings]

Figure 1 is a potential hourly curve diagram of conventional strike plating.
FIG. 2 is a time-current density diagram of the method of the present invention, and FIG. 3 is a diagram of the plating state when applied to a ceramic casing. 10... Authentic gold plating layer, 12... Gold 1-like layer deposited by low current density. 14... Gold strike layer deposited by high current density, 16... Rhodium plating layer. 18... Nickel plating layer, 20... Tungsten metallized layer, 22... Ceramic substrate. Patent applicant Shinko Electric Industry Co., Ltd. Representative Takekio Mitsunobu Figure 1 Time (seconds) Figure 2 Washing time (seconds)

Claims (1)

[Claims] 1. In strike plating for objects with poor electrodepositivity, plating is performed at a high current density in the early stage of plating to form a plating film on the surface of the object in a short time, and thereafter the current density is switched to a lower current density to achieve the specified level. A strike plating method characterized by time plating.