JPS627280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an extremely small area for plating processing.
The present invention relates to a micro-partially silver-plated product in which gold, gold alloy, platinum metal, or nickel is subjected to base plating treatment in minute portions, and the surface thereof is coated with silver plating having a diameter smaller than the diameter of the base plating, and a method for plating the same.

That is, the present invention provides a bonding area in a lead frame of an integrated circuit element (hereinafter referred to as IC),
For parts that are extremely small and require high conductivity, such as contactors and connectors of ultra-small switches and relays, or lead parts of printed circuit boards, we use gold, gold alloys, platinum metals, and nickel to conduct very small parts. Undercoat plating is formed in a partial area, and the surface of the undercoating is directly plated with silver in a finer range than this, which eliminates the substitution prevention treatment and peeling treatment that are indispensable in conventional silver plating methods. This invention relates to a micro-partially silver-plated product and a method for plating the same, in which the means can be omitted, the cost of silver-plating can be greatly reduced, and the quality of plating, including the adhesion of the silver-plated layer, can be greatly improved.

Generally, in the bonding area of an IC lead frame, the lead part of a contactor, or a printed circuit board, the area that truly requires high conductivity is extremely small, so it is necessary to partially plate gold, etc. in the narrowest possible area. It was being processed.

However, since each of the above-mentioned products is produced in extremely large quantities, the reality is that even if it is only partially plated, the consumption of precious metals increases and the cost of plating processing cannot be ignored.

For this reason, cheaper silver plating is increasingly being used as a substitute for gold, etc., and it is well known that silver plating is carried out through the steps shown in FIG.

First, the part to be plated is degreased with a caustic soda solution in a degreasing step 1, then the caustic soda solution is washed away in a water washing step 2, and then impurities and oxides on the metal surface are removed with concentrated hydrochloric acid in a pickling step 3. After removal, washing is performed in water washing step 2.

In the next base plating step 4, copper plating is performed on the entire surface of the member to be plated as described later to form a base plating, and then through the water washing step 2, the replacement prevention treatment step 5
The member to be plated is transferred to. Here, for the reason described later, it is immersed in a substitution prevention agent, and after silver plating is partially plated at predetermined locations in the next silver plating step 6, it is washed with water in a water washing step 2.

In the next stripping step 7, the substrate is dipped in a stripping agent to strip off the excess base plating, and is completed through the water washing step 2.

The conventional silver plating process requires a multi-step process as described above, but in the base plating step 4, a base coat is applied to the entire surface in accordance with the base material of the member to be plated. For example, in the case of an iron base, it is necessary to first perform strike plating for the iron base and then plating for the copper base, and strike plating for the copper base must also be performed in the case of a copper alloy or the like.

In other words, multi-stage strike plating is often applied to parts that do not require plating, resulting in a waste of materials and man-hours.

Further, the substitution prevention treatment step 5 is also essential.
In other words, since the deposition potential of silver plating in a silver plating bath (for example, silver cyanide) is very base, simply immersing a copper or copper alloy substrate or a base-treated member to be plated in the bath causes a substitution reaction. Silver is precipitated, but the ring base silver precipitated at this time has extremely weak adhesion to the base.

Therefore, in order to maintain the plating strength, it is necessary to prevent this substitution reaction, and it is necessary to treat the object to be plated to prevent substitution.

Furthermore, in the silver plating step 6, the member to be plated is connected to the cathode electrode, and a mask for masking is arranged, while the plating liquid is applied from a nozzle connected to the anode electrode and facing the member to be plated through the mask. It is made to spray.

However, with the above-mentioned conventional means, the plated liquid and surplus liquid tend to diffuse or stay in the nozzle or the through-hole part of the mask, and they also tend to infiltrate from the masking boundary, so it is difficult to miniaturize the diameter of the plating process and improve accuracy. From solid,
In large-volume processing processes, it is difficult to avoid a decrease in plating efficiency and deterioration in plating quality.

Therefore, in the past, it was not accurate plating in very small parts, but only spot plating, which increased the consumption cost of plating materials such as silver and the plating processing cost, and also caused variations in the quality of plating. There was an inconvenient problem.

Furthermore, conventional means require a stripping step 7.

As a result of the base plating being formed in areas other than those that are truly required on the part to be plated, this may cause problems such as the formation of a film due to oxidative corrosion or chemical changes, such as making it difficult to solder, or Since there are problems such as an adverse effect on the plating layer, it is necessary to peel off the excess base plating.

For this reason, the silver-plated product is immersed in a release agent to remove the base plating, and then washed with water.

As described above, the conventional silver plating process requires the substitution prevention treatment step 5, the stripping step 7, and the accompanying water washing step 2, which increases the processing cost.In addition, the plating quality deteriorates due to the adhesion of these liquids. There were many problems in the silver plating step 6, such as increased processing costs and increased consumption of materials such as silver.

The present invention was made in view of the above problems, and
When silver plating is applied to parts to be plated, the replacement prevention process and peeling process are omitted, simplifying the overall processing time, and greatly improving the processing efficiency of the silver plating process, reducing the consumption of silver and other materials. The object of the present invention is to provide a method for silver plating in small areas, which reduces the amount of silver plating and significantly reduces processing costs.

Another object of the present invention is to perform base plating or silver plating only on the truly necessary parts of the plated member, and to obtain high-quality plated products at low cost. Furthermore, it is an object of the present invention to provide a micro-partially silver-plated product in which the micro-partially plated cylindrical part is colored to make it distinguishable from others.

That is, in the present invention, a predetermined portion of the member to be plated is coated with gold, a gold alloy, a platinum metal, or nickel in minute areas, and then silver plating is applied directly on the plated surface in minute areas. , which eliminates the need for replacement prevention treatment or peeling treatment.

Hereinafter, embodiments of the present invention will be described based on FIG. 2 and subsequent figures.

First, to explain the entire plating process according to the present invention, the member to be plated is degreased and washed in the above-described degreasing process 1, water washing process 2, pickling process 3, and water washing process 2 in the same way as in the known example. , and transferred to the base plating step 11.

Here, a plating device to be described later is used to perform base plating on a minute area that truly requires silver plating.

This base plating uses a material with a tendency to ionize to which silver can firmly adhere even if the base material of the plated member is iron, copper or copper alloy. The plating area and thickness are made to be extremely small.

Next, the plated member with the base plating is washed in a water washing step 2 and then directly transferred to the next silver plating step 12, where the upper surface that has been minutely plated with gold, gold alloy, platinum metal, or nickel is Silver plating of minute diameters (=portions that truly require plating) is then performed, and this is also done using a plating device, which will be described later. The treated product, which has been silver-plated on the base plating in this way, is cleaned of the plating solution in the final washing step 2, and the entire process is completed.

The plating device used in the base plating step 11 and the silver plating step 12 is an invention previously provided by the applicant of the present invention (Japanese Patent Application No. 100722 of 1982 entitled "Method and Apparatus for Plating a Small Area"). 1982 No. 134493
No. ``Small part plating method and device'', patent application
No. 134494 of 1983, "Partial plating method and device", Patent application No. 125783 of 1982, "Minute partial plating method and device"...etc.).

For example, when the member to be plated is an IC lead frame 20 and the silver plating processing area is a bonding area, a plating apparatus schematically shown in FIG. 3 is used.

This includes a mask 22 that masks the bonding area and has a through hole 21 formed therein, a jacket tube 24 that fits with this mask 22 to form a sealed space 23, and a through hole 21 in this jacket tube 24. A nozzle 25 is disposed facing each other and injects a pressurized plating liquid, and an intake pipe 26 communicating with the jacket pipe 24 is connected to an intake mechanism (not shown), so that the inside of the jacket pipe 24 is brought to a negative pressure to a predetermined value. An arbitrary outside air introduction groove (not shown) may be formed in the mask 22 as necessary.

Note that the nozzle 25 is connected to the anode side, the lead frame 20 is connected to the cathode side, and both are connected to a DC power source.

Then, in the plating device disposed in the base plating step 11, a plating liquid for gold, gold alloy, platinum metal, or nickel is supplied under pressure to the nozzle 25,
Further, a silver plating liquid is supplied under pressure to the nozzle 25 of the silver plating step 12.

Also, in both plating devices, the plating target and mask 2
The position of the second through hole 21 is mechanically set in advance with good precision. According to the plating process related to the above process,
The plating liquid is injected into the bonding area of the lead frame 20 through the mask 22 from a place where excess liquid and used liquid are forcibly expelled to the outside due to the negative pressure inside the mantle tube 24 of the device. Through hole 2
It is possible to accurately plate only a minute part determined by the processing form and dimensions of 1.

Furthermore, since the plating liquid that comes into contact with the part to be plated is always fresh and there is no stagnation or infiltration phenomenon, the plating efficiency and plating quality are extremely good, and it is particularly suitable for processing large quantities. (For details, please refer to
Since it has been disclosed in the above invention, the explanation here will be omitted. ) Incidentally, in this example, as shown in FIG. 4, the base plated part A made of precious metal such as gold or nickel has a diameter D ₁ =0.3 mm and a thickness of 0.01 μm, and a silver plated part B treated on the surface. It was confirmed that plating of small parts with a diameter D ₂ =0.25 mm and a thickness of 3 to 5 μm can be performed in large quantities in an extremely short period of time and is at a practical level.

Furthermore, needless to be explained, the nickel used as the base plating is easily oxidized and its film is tough, so even if silver is plated on top of it, it is difficult to cause substitution, and the plating is difficult to oxidize at high current densities. Does not deteriorate the adhesion of the film. On the other hand, the underlying gold, gold alloy, or platinum metal has a smaller ionization tendency than silver ions compared to other metals, so there is no precipitation of reduced silver, and the properties are stable, so iron It has strong adhesion to substrates and copper alloy substrates, as well as strong adhesion to silver, allowing for reliable silver plating.

Incidentally, since the base plating diameter (D ₁ )>the silver plating diameter (D ₂ ), misalignment of the silver plating can be prevented.

In the silver plating treated in this way, ring source silver does not precipitate when the base plating treated product is silver plated, so there is no need for substitution prevention treatment as in the conventional silver plating process.

Furthermore, since both base plating and silver plating are plated in minute portions only where truly necessary, there is no need to peel off the base plating, and the man-hours in the entire plating process can be greatly reduced. Further, in the present invention, even if gold or gold alloy is used as the base plating, the material cost is extremely low.

For example, even when used in the lead frame 20, since one place has a diameter of 0.3 mm and a thickness of about 0.01 μm, the total amount of gold required for the entire plating area is very small.

Of course, the silver one has a diameter of 0.25mm and a thickness of 3μ.
Since it is 5 μm, the total amount of silver is only a small amount.

Furthermore, since both of the above plating processes can be performed in an extremely short time, the processing costs can be reduced significantly compared to conventional silver plating methods due to the simplification of steps. Furthermore, since gold, gold alloys, and nickel are themselves rich in brightness, it is highly distinguishable between the base and the base, and in the case of gold alloys in particular, various hues appear depending on the alloy. The identifiability is further improved, and it is easy to detect with a sensor when silver plating or bonding is performed on it, and it is suitable for positioning, and the processing accuracy can be further improved.

As described above, according to the present invention, gold, gold alloy, platinum metal, or nickel is used as the base plating, and minute portions are plated in the necessary areas, and
Since the base plating surface is silver-plated in smaller parts, it has the following characteristics.

(1) The gold, gold alloy, platinum metal, or nickel of the base plating has strong adhesion to both the base material of the plated part and the silver plating surface, and there is no generation of ring base silver, so it is possible to plate small parts. However, it has extremely high plating strength and excellent heat resistance, so the properties of the plating area can be sufficiently maintained.

(2) Since the silver plating process eliminates the need for a substitution prevention process, a peeling process, and the accompanying water washing process, the plating process time is shortened and the process costs are significantly reduced.

(3) Since no anti-displacement agent or stripping agent is used, not only are these waste liquid treatment equipment and processes unnecessary, but also the negative effects of these liquids on each plating forming area can be prevented and the plating quality can be further improved.

(4) Because the base is made of a material with extremely low resistance such as gold, gold alloy, platinum metal, or nickel, the plating area has high conductivity, and is suitable for bonding areas of IC lead frames, contactors, and lead parts of printed circuit boards. Ideal for

(5) By adding a hue at the stage of base plating and its own brightness, it is highly distinguishable from the base material of the member to be plated, and the positioning accuracy can be much higher.

Therefore, the coordinates can be set accurately during silver plating or bonding processing.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional silver plating process, Fig. 2 is a block diagram showing a silver plating process according to the present invention, and Fig. 3 is a schematic configuration of a plating device used in the above process. FIG. 4 is a perspective view of a plated product obtained through the same treatment process. 1... Degreasing process, 2... Water washing process, 3... Pickling process, 11... Base plating process, 12... Silver plating process, 20... Lead frame (member to be plated), 21... Through hole, 22...Mask, 23...
Closed space, 24... Mantle tube, 25... Nozzle, 2
6...Intake pipe.

Claims (1)

[Scope of Claims] 1. A base plated portion is formed by partially plating with gold, gold alloy, platinum metal, or nickel at a specific location of a member to be plated, and on the surface of this base plated portion, finer particles than this are formed. A product that has been plated with silver in small areas. 2. A step of degreasing and pickling the member to be plated, and a means of spraying a gold, gold alloy, platinum metal, or nickel plating liquid onto the cleaned member to be plated in a sealed negative pressure space to perform base plating on minute portions; A microscopic silver plating method comprising means for spraying a silver plating liquid in a sealed negative pressure space onto the base plating portion of the member to be plated to silver the microscopic areas.