TW201335442A - The electrochemical deposition process associated with the supercritical fluid - Google Patents

Abstract

This invention discloses the electrochemical process performed in the non-supercritical state which uses the solution that had been mixed with supercritical fluid. According to this invention, part or all of the solution in the filtering circulation is diverged into a supercritical mixing chamber where it is mixed with the supercritical fluid. The well-mixed solution is then released to reaction environment of the electrochemical chamber and mixed with the remaining solution in the chamber. The electrochemical reaction conducted in the supercritical-fluid-mixed solution produces the treatment on the workpiece with improved quality.

Description

Supercritical fluid assisted electrochemical deposition process system

The present invention relates to a process for electrochemically treating a surface of a material, such as electroplating, electroless plating, etc., to improve the surface properties of the material.

The modification of the surface of the material can be generally divided into processing and coating treatment, the former includes heat treatment, mechanical cutting, electrochemical cutting, etc., while the latter covers electroplating, electroless plating, physical vapor deposition, chemical vapor deposition, and spray coating. Etc., its functions range from general decorative purposes to performance adjustments. In the electrochemical treatment process, mainly electroplating, electroless plating, conversion coating, etc., are used to produce a metal or non-metal layer different from the substrate by electrochemical reaction on the surface of the material. Electroplating is a conventional process in which an ion in an electrolyte that is in contact with a substrate is electrically connected, and a plating layer is formed on the substrate, such as electroplating copper, electroplating nickel, electroplating, and the like.

In the traditional electroplating process, the process control parameters such as composition, temperature, and current density of the electroplating solution are quite sensitive to the electroplating result, and the reduction efficiency of electroplating is often less than 100%, resulting in hydrogen reduction, pinhole formation, surface roughness, etc. . In order to improve these problems, the use of plating bath additives such as wetting agents, gloss agents, stress modifiers, etc., has become a very important technique in electroplating. However, although the use of additives changes the distribution of the electric field by the adsorption of organic molecules on the surface of the cathode, improves the surface roughness of the coating, reduces the internal stress, etc., and solves some difficulties, but also derives organic substances such as sulfur and other elements in electroplating. In the deposition process, the plating layer is incorporated, causing the coating to become brittle. Therefore, in U.S. Patent No. 6,793,793, the supercritical fluid is mixed with the treatment liquid, the plating solution, and the low viscosity of the supercritical fluid is utilized. No surface tension, easy to recycle characteristics, in the same reaction tank, successive processes such as pickling, activation, electroplating, cleaning, etc., to reduce process time, reduce waste pollution, reduce production costs, and improve coating quality. China CN101092716B invention patent also discloses superfine carbon dioxide with metal nickel, metal copper solution, and the addition of dodecyl compounds, in the micro-electroforming process under pulse current, can deposit dense structure, smooth surface, sharp edges and corners Micro parts.

Compared with other fluids, carbon dioxide has a pressure and temperature threshold (7.39 MPa, 31.1 ° C) that easily reaches the supercritical state, and is not toxic to the environment. The industry is often used for cleaning of objects, dyeing and finishing of fabrics, and drugs. Extraction and so on. Since the supercritical carbon dioxide has a good solubility to hydrogen, the hydrogen generated in the above electroplating process can be effectively carried away from the surface of the cathode, thereby reducing hydrogen gas entrapment in the plating layer to form pinholes. In addition, due to the low viscosity and surface tension of supercritical carbon dioxide, the overall viscosity and surface tension of the plating solution can be reduced, so that the plating solution can easily enter and wet the surface shape of the object, improve the surface coverage of the plating, and improve the flatness. Increase the surface gloss. On the other hand, due to the microbubbles formed by the supercritical carbon dioxide in the plating solution, the local current distribution during plating is changed, and the effect of refining the grain of the plating layer is produced, thereby effectively improving the hardness and corrosion resistance of the plating layer. Studies have shown that this coating improvement effect is related to the dissolution of carbon dioxide in the bath.

Although the technique of mixing the plating solution in a supercritical state can achieve the effect of improving the plating performance, a technique using different supercritical fluids or subcritical fluids is proposed, but the supercritical or subcritical state is maintained. All must be carried out in a pressure vessel under high pressure or even high temperature. For larger workpieces, maintaining a large-capacity supercritical environment would be very expensive and relatively reduce the practical feasibility of the process.

Therefore, in order to improve the above problems, the present invention proposes an innovative method which can simultaneously obtain the advantages of the supercritical fluid electrochemical process, but does not greatly increase the cost of setting a large high pressure vessel.

To achieve the above object, the process of the present invention is in a solution filtration circulation loop of a conventional electrochemical treatment apparatus, and a mixing tank of a supercritical fluid and an electrochemical solution is disposed. In the circulation of the solution used in the electrochemical treatment device, a part of the solution is taken into the mixing tank, and the supercritical fluid and the solution are mixed and stirred in a supercritical fluid with a critical pressure and temperature, and the mixed electrochemical solution is further mixed. The pressure is reduced, sent back to the electrochemical treatment tank, and mixed with the original solution in the tank, and the electrochemical treatment is continued.

Since the electrochemical solution mixed with the supercritical fluid in a supercritical environment returns to the environment of electrochemical treatment, it will still have some characteristics of the solid solution supercritical fluid, thereby improving the treatment effect of the conventional electrochemical process. On the other hand, the supercritical mixing tank and the electrochemical treatment tank do not need to be built in a ratio of 1:1, which can reduce the size of the supercritical mixing tank and reduce the cost of the equipment.

Therefore, the object of the present invention is to innovate an electrochemical treatment process which can simultaneously improve the plating properties of the electrochemical treatment process and reduce the investment cost of the equipment.

Furthermore, another object of the present invention is to reduce the use of the electrochemical solution by utilizing the characteristics of easy recovery of the supercritical fluid solution, and to alleviate the environmental pollution problem of the waste liquid.

Furthermore, another object of the present invention is that the supercritical processing procedure for extraction, mixing, and returning is sustainable, and therefore, the effect of improving the electrochemical treatment is not degraded by the elongation of the electrochemical time.

In order to understand the objects, features and advantages of the present invention, the present invention will be described in detail by the following detailed description and the accompanying drawings.

As shown in Figure 1, the conventional electrochemical treatment equipment is mainly composed of a treatment tank (102), a filter circulator (120), a circulation pump (109), a cathode (105), an anode (106), a thermometer (104), and a heating temperature. The controller (110), the heater (108), the power supply (103), the agitator (101), and the like are formed. The electrochemical solution (107) is mainly filled in the treatment tank (102) and maintained at the temperature of the electrochemical reaction by the temperature controller (110), and is externally circulated by the piping system of the filtration circulator (120) to filter the electrochemical Impurity particles that may be present in the liquid. The power supply (103) provides current to the circuit formed by the cathode (105), the anode (106), and the electrochemical fluid. The cathode (105) is the workpiece to be processed, and the anode (106) is a plating material or an insoluble anode. In general, in addition to the main reduction reaction at the cathode during electroplating, hydrogen is often formed by reduction of hydrogen ions, causing pinholes in the plating layer to occur. In addition, due to the surface tension, the general electrochemical liquid often cannot enter the fine holes or gaps on the surface of the workpiece. This problem is common in the fabrication of MEMS, which causes the coating to not cover the surface of the workpiece uniformly.

As shown in Fig. 2, the structural diagram of the conventional supercritical plating system is first filled with the expected plating solution (216) in the high pressure tank body (215), and the cathode (209) and the anode (210) are fixed on the upper cover (219). After that, the upper cover (219) above the tank is covered. On the other hand, the auxiliary plating fluid (217) is cooled by the cylinder (201) into the condenser (204) via the control valve (202) to ensure that the fluid remains in a liquid state. Subsequently, the auxiliary fluid is pressurized into the high pressure tank (215) by a high pressure pump (205) and the pressure in the tank is measured by a pressure gauge (218). After a sufficient auxiliary fluid (217) is fed into the high pressure tank (215), the temperature control water jacket system (222) on the periphery of the high pressure tank body (215) is started, and the temperature in the tank is monitored by a thermometer (211). At this time, the magnet agitator (214) under the tank is simultaneously activated to drive the stirrer (208) in the tank to mix the plating solution (216) with the auxiliary fluid (217). When the temperature and pressure in the tank reach the conditions required for supercritical, and the plating solution is uniformly mixed by stirring, the power supply (206) connected to the cathode (209) and the anode (210) can be turned on for electroplating. After the electroplating is completed, the inlet valve (220) of the high pressure tank body is closed and the outlet valve (221) is opened to release the high pressure gas in the high pressure tank body (215), and at the same time, the plating liquid is discharged in the plating liquid recovery tank (207). liquid.

As shown in Figure 2, the conventional supercritical plating process, it is obvious that the size of the high pressure tank body (215) limits the size of the workpiece that can be processed, and increases the volume of the high pressure tank body (215), which inevitably increases the cost of the process, and The design of the continuous plating process cannot be performed. In order to solve the above limitation, FIG. 3 is a schematic view of the process of the first embodiment of the present invention, wherein the main system device is a circuit (300) for supercritical fluid mixing outside the conventional electrochemical treatment tank (313). The circuit mainly consists of an auxiliary fluid storage cylinder (302), a cooling and cooling water tank (318), a high pressure gas pump (317), an autoclave mixing tank (305), a mixing tank temperature controlled circulating water tank (306), and a mixing tank ( 305) consisting of a circulation pump (315) between the plating solution overflow tank (312). First, part of the electrochemical solution in the electrochemical treatment tank (313) flows into the overflow tank (312) via the overflow pipe (322), and the plating liquid in the tank is quantitatively sent by the circulation pump (315) through the pipeline (311). Into the autoclave mixing tank (305), and then close the line valve (323). On the other hand, the auxiliary fluid is cooled by the pressure regulating valve (301) of the gas cylinder (302) through the line (303) and the cooling water tank (318), and then enters the high pressure gas pump (317). The auxiliary fluid enters the autoclave mixing tank (305) through the line (324) and the control valve (325) under pressure at a set pressure. When the pressure of the mixing tank (305) reaches the set pressure, the inlet valve (325) is closed, and the temperature of the fluid supplied from the temperature control circulating water tank (315) to the water jacket (326) outside the tank is controlled. When the electrochemical solution and the auxiliary fluid reach the set pressure and temperature in the mixing tank (305), the stirring device (316) in the tank is simultaneously activated to perform mixing under supercritical or subcritical conditions.

When the liquid in the mixing tank (305) is mixed and stirred within a set time, the outlet valve (327) is opened, and the mixed liquid is sent to the electrochemical treatment tank (313) via the pipeline to be mixed with the original electrochemical solution. The mixture sent out will have a process of depressurization, and most of the auxiliary fluid will return to a gaseous state and be withdrawn from the mixture. The process of extracting the electrochemical solution, mixing with the auxiliary fluid under supercritical or subcritical conditions, and returning to the electrochemical treatment tank for remixing can be continued in a periodic manner, so regardless of the length of the electrochemical treatment, the treatment liquid will Continuously mixed with the auxiliary fluid while maintaining some of the advantages of electrochemical treatment in the supercritical or subcritical state. FIG. 4 is a schematic diagram of the device system of the embodiment.

Figure 5 shows the X-ray diffraction spectrum and grain size measurement results of electroplated nickel in different processes. The diffraction patterns (a), (b), and (c) are respectively measured results of conventional nickel plating, supercritical plating after the present invention, and conventional supercritical plating. The plating system is mainly a Watt's bath system, the auxiliary supercritical fluid is carbon dioxide, and the surfactant is a nonionic surfactant of Polyoxyethylene Sorbitan Monolaurate. From this, the full width of the diffraction peak (Full Width at Half Maximum) is taken into the Scherre formula to calculate the size of the corresponding crystal grain. The measurement results show that the grain of the conventional supercritical plating layer can reach the nano-scale grain, which has obvious refinement effect compared with the grain of the conventional electroplating layer, and the supercritical process after the invention is also equivalent to the general electroplating. The grain refinement is improved. This improvement in grain refinement will reflect the increase in hardness of the coating described below. In addition, the diffraction peak of the diffraction pattern also shows that the preferred orientation of the crystal changes from {200} of general plating to {111} of supercritical, which also causes a change in the mechanical properties of the coating.

Figure 6 shows the hardness measurement results of different electroplated nickel coatings. With the refinement of the above grains and the preferred crystal orientation, the hardness of the coating is increased from 400 Hv of general plating to 700 Hv of supercritical, while supercritical after the present invention The coating still achieves a hardness of 550 Hv. In terms of the surface topography of the coating, Fig. 7 (a) and (b) are the surface scanning electron microscope (SEM) photographs of the supercritical plating and the supercritical plating after the present invention, respectively, and the results show that the conventional supercritical plating is used. The surface of the nickel layer is rougher than the post-supercritical coating and has more fine pinholes (pointed by the arrows in the figure). From the above results, it can be clearly found that although the supercritical process of the present invention is carried out under atmospheric pressure, it is still possible to retain some of the effects of the conventional supercritical plating process.

Figure 8 is a block diagram showing the structure of a second embodiment of the present invention applied to electroless plating. The system architecture of this embodiment is similar to that shown in FIG. 3, and is mainly composed of an auxiliary fluid supercritical mixing system (400) combined with an electroless plating tank system (421) and a circulation pipeline (410, 420). Wherein, the auxiliary fluid supercritical mixing system (400) mainly extracts the electrochemical reaction liquid through the inlet line (410) into the autoclave mixing tank (405) and the auxiliary fluid for supercritical or sub-supercritical mixing, and then exits the pipeline. (420) Returning the electroless plating bath (412) to the original electrochemical reaction solution for remixing, periodically updating the reaction solution to maintain the advantage of supercritical processing. Since the electroless plating is electroless plating, only the workpiece (408) is suspended in the processing tank (412), and no external power supply is required to supply power. Figure 9 is a schematic view of an electroless plating apparatus according to a second embodiment of the present invention corresponding to Figure 8.

The present invention has been disclosed in some preferred embodiments, and is not intended to limit the scope of the invention. Any change and modification that may be made in accordance with the present invention, which is within the spirit and scope of the present invention, should be covered by the scope of the present invention. The definition shall be based on the scope of the patent application.

209. . . Supercritical plating cathode

210. . . Supercritical plating anode

301. . . Auxiliary fluid storage cylinder control valve

302. . . Auxiliary fluid storage cylinder

318. . . Auxiliary fluid cooling cooler

317. . . High pressure pump for auxiliary fluid

305. . . Hot autoclave mixing tank

316. . . Stirring device

320. . . Stirrer

306. . . Temperature controlled water bath of autoclave mixing tank

323. . . Pipeline control valve

312. . . Electrolyte overflow tank

311. . . Connecting pipe between overflow tank and autoclave mixing tank

321. . . Electrochemical treatment tank circulation filter

309. . . Electrochemical treatment tank power supply controller

313. . . Electrochemical treatment tank

412. . . Electroless plating reactor

408. . . Electrolessly processed workpiece

The first figure shows the structure of traditional electrochemical processing equipment

The second picture of the conventional supercritical electrochemical processing equipment architecture diagram

Third Embodiment Illustration of an electroplating apparatus structure according to a first embodiment of the present invention

Fourth Figure Schematic diagram of a plating apparatus according to a first embodiment of the present invention

Figure 5 X-ray diffraction spectrum and grain size of electroplated nickel plating in different processes

Figure 6 Hardness of electroplated nickel plating in different processes

Figure 7 Scanning electron micrograph of surface electroplated nickel in different processes

Eighth Diagram of an Electroless Plating Apparatus Structure of a Second Embodiment of the Invention

Ninth diagram of the electroless plating apparatus of the second embodiment of the present invention

301. . . Auxiliary fluid storage cylinder control valve

302. . . Auxiliary fluid storage cylinder

318. . . Auxiliary fluid cooling cooler

317. . . High pressure pump for auxiliary fluid

305. . . Hot autoclave mixing tank

316. . . Stirring device

320. . . Stirrer

306. . . Temperature controlled water bath of autoclave mixing tank

323. . . Pipeline control valve

312. . . Electrolyte overflow tank

311. . . Connecting pipe between overflow tank and autoclave mixing tank

321. . . Electrochemical treatment tank circulation filter

309. . . Electrochemical treatment tank power supply controller

313. . . Electrochemical treatment tank

Claims (10)

A supercritical fluid-assisted electrochemical deposition process system, the system comprising an auxiliary fluid supply system, a high pressure pressurization pump, a autoclave mixing tank, a mixing agitator, an electrolyte, and an electrochemical treatment tank system And a circulation pipeline system between the tanks, wherein a part of the electrolyte in the electrochemical treatment tank enters the autoclave mixing tank through the circulation line between the tanks, and is supplied by the auxiliary fluid supply system and is pressurized by the high pressure pump After the pressure, the auxiliary fluid is stirred in the mixing tank of the autoclave, and then stirred by the mixing agitator, and then returned to the electrochemical treatment tank system through the inter-tank circulation pipeline system, and mixed with the original electrolyte in the tank to continuously improve. Electrochemical deposition process in an electrochemical treatment cell. For the process system described in claim 1, the temperature and pressure of the autoclave mixing tank can be adjusted to the supercritical or sub-supercritical state of the auxiliary fluid. The process system of claim 1, wherein the ratio of the electrolyte to the auxiliary fluid through the autoclave mixing tank is adjustable. For example, in the process system described in claim 1, the ratio of the extracted electrolyte in the circulation line can be adjusted. The process system of claim 1, wherein the electrolyte is mixed with the auxiliary fluid through the autoclave mixing tank and returned to the electrochemical treatment tank system for a period of time. For example, in the process system described in claim 1, the auxiliary flow system is carbon dioxide. The process system of claim 1, wherein the electrochemical treatment tank is subjected to a plating reaction. The process system of claim 1, wherein the electrochemical treatment tank is subjected to an electroless plating reaction. The process system of claim 1, wherein the electrochemical treatment tank is converted into a reactor. The process system of claim 1, wherein an electrolyte is added to the electrolyte to adjust a mixture of the auxiliary fluid and the electrolyte.