US20030075449A1

US20030075449A1 - Method for controlling field flow decouple plating and a device thereof

Info

Publication number: US20030075449A1
Application number: US10/266,061
Authority: US
Inventors: Shyh Jiang; Dong Lee; Chi Yang; Hsin Ming; Chuan Huang
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-19
Filing date: 2002-10-07
Publication date: 2003-04-24
Also published as: TW574436B

Abstract

A method for controlling plating with two independent power sources, wherein the high voltage power source is used for controlling the electrical swimming speed of the metal positive ions while the other is low-voltage power source for being used to control rate of plating rate. Positively charged metal ions of the strong electric field in the plating solution can reach to the negatively charged and unevenly distributed surface of the extraction negative pole more quickly, which is in turn connected to the negative of the low voltage power source. The ions aggregate at the recess of the extraction negative pole surface and waiting incoming electrons so as to perform electric extraction and produce uniform plating. The present invention also provides the apparatus for carrying out the mentioned method and therefore achieves better plating quality.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for controlling field flow decouple plating, and, in particular, to a method of controlling a decouple plating with which an electric field allowing metal ions electrically swimming and current extracting the metal ions can be controlled such that a coarse surface ready for being plated can be controlled to acquire an even plating. The present invention further relates to a novel plating apparatus utilizing the control method so as to enhance the quality of plating greatly.

2. Description of Related Art

The basic theory with regard to metal plating includes a process of electrical separation process, in which metal ions moving away the surface of the positive pole and entering the plating solution as positive ions; a process of electrical swimming, in which the positive ions moving toward the negative in the plating solution; and a process of electrical extraction, in which the positive ions capture electrons from the negative pole as metal molecules adhering to the negative poles.

Referring to FIG. 1, the earliest conventional plating apparatus includes a rated voltage direct

current power source

101, a conductive work piece 102 connecting with a negative pole and a plating metal 103 connecting with a positive pole. As soon as the power is on, metal molecules 105 of the plating metal 103 loses electrons and are ionized as positive metal ions 106 such that the positive metal ions move toward the work piece 102 at the negative pole to contact and obtain the electrons so as to analyze metal molecules 104 electrically and deposit on the work piece 102 due to diffusion action of ions and the electric field in the plating solution. On the other hand, the electrolyzing reaction performs continuously so that further new metal molecules 105 lose electrons to become new metal positive ions 106 to replenish the consistency of the plating solution. The positive metal ions 106 ceaselessly move toward the work piece 102 at the negative pole to electrolyzing-extract metal molecules 104 to complete the plating process for the work piece due to diffusion action and electric swimming caused by the electric field.

The plated thickness on the work piece is varied depending on the time duration of plating while the prior art of plating device shown in FIG. 1 is operated. The work piece at the negative pole has a surface with certain roughness to result in uneven plated surface while ions binds together with electrons in the electrolyzing-extraction process. Referring to FIG. 2, a micro view of electrolyzing-extraction process is illustrated to show the ions binding together with the electrons in case of the

work piece

102 having a coarse surface. Because the electrons in the work piece 102 at the negative pole move faster than positive ions 106 in the plating solution, the surface of the work piece 102 at the left side thereof produces an ion void layer 107 after being plated a period of time and the electrons will aggregate at the surface of the work piece 102 for waiting the positive ions electrically swimming over the void layer 107. However, the surface of the work piece 102 has a coarse extrusion 109 accumulating with more electrons 110 under actuation of the electric field. A void layer 111 at the left side of the tip of the jut contacts with incoming positive ions first so that the ions at the area of the tip has faster and more extractions. Thus, a situation of uneven plating surface occurs during the positive ions joining the electrons for performing the process of electrolyzing extraction such that the roughness of the plated surface is getting rougher and the thickness of plating is getting more uneven.

Up to now, there are two ways having been proposed to improve the plating process in order to attain homogeneous plated thickness and a flat plated surface. One of the ways, which is disclosed in U.S. Pat. No. 4,789,437, is that flattering agent such as syrup is added in the plating solution. Referring to FIG. 3, the

flattering agent

205 is utilized to enclose the positive ions and the positive ions enclosed by the flattering agent excludes mutually to distribute uniformly with an equal span 202 respectively before reaching the work piece 102 at the negative pole such that the ions 201 electrically swim toward the surface of the work piece 102 in parallel and perpendicularly to the surface. Being affected by the traction force of more electrons at the tip part during moving close to work piece, each positive ion becomes deviated and moves toward tip part with the flattering agent 205 enclosing each of the positive ions respectively. Because the flattering agent 205 stays at the surface of the work piece after the ions being electrically extracted, the tip part will be stayed with more flattering agent 205 due to more electrically extracted ions being produced at the tip part. Usually, the viscosity of the flattering agent is greater than the plating solution and the positive ions move slower in the flattering agent than in the plating solution so that it is easier for the positive ions to arrive the recess parts on the surface of the work piece instead of the tip part thereof. The viscosity and distribution of the flattering agent make the ions not easy to congregate at the tip part where the electrons congregate and force the electrically extracted ions to distribute on the surface of the work piece evenly in order to obtain the purpose of flattering. However, the first treatment with flattering agent is disadvantageous that it is easy for the flattering agent to be surrounded and mixed in the extracted metal molecules 207. Although it is possible to force the flattering agent out by way of heat treatment, residue stress will be produced at the plated surface. In addition, the plating solution becomes more complicated and hard to be treated well in case of being added with the flattering agent so that the cost for the waste solution becomes higher.

The second way for improving the plating process in order to attain homogeneous plated thickness and a flat plated surface is pulse input power method, which has been disclosed in prior art such as U.S. Pat. Nos. 4,459,460, 3,886,053, 6,071,398, 4,789,437 and 6,132,584. The basic theory of operation for the pulse input method is shown in FIGS. 4 to 9.

Referring to FIG. 4, a state of the pulse input power being not supplied is illustrated. Metal

positive ions

301 should be distributed evenly on the surface 305 of the work piece 102 at the negative pole under an equilibrium condition due to the phenomenon of exclusion between positive electricity of ions. Referring to FIG. 5, it illustrates a state of electron current flows into the work piece 102 at the negative pole simultaneously as soon as the pulse source is input. Because electrons in the work piece flow speedily and the heavier positive ions move slowly. The positive ions can find out a nearest negative pole surface 305 respectively to take an electron for being extracted as a metal molecule 303. Referring to 6, the plating solution on the surface of the work piece at the negative pole can form a void layer 305 of positive ions while the metal ions on the metal surface have consumed completely. Under this circumference, new electrons entering the negative pole are unable to join with the positive ions except aggregating at the surface of the work piece waiting for positive ions electrically swimming from the void layer 304. Most electrons may aggregate at the tip part 306 on the surface of the work piece due to attraction of the positive pole. Because the tip part at the surface thereof has a thinner void layer 307 and the electrons aggregating at the tip part can produce a local electrical field concentration 308 to attract the positive ions, the plating job after the void layer 304 forming will concentrate at the tip part to coarsen the plating surface with inconsistent thickness. Referring to FIG. 7, a state of the pulse power source being off supplying electrons right after the void layer forming for avoiding the electrons concentrating at the tip part awaiting positive ions is illustrated. The positive ions can be diffused to distribute evenly so as to reach a balance naturally during the power being disconnected. Then, next pulse plating can be treated after the balance distribution. It is hard to estimate the number of the ions on the surface of the work piece accurately during the pulse plating. If less ions are estimated, it results in slow plating and if excessive ions are estimated, it results in the electrons aggregating at the tip part. The conventional way is to estimate the ions excessively to admit more electrons and the excessive electrons are removed by way of inverse impulse. FIG. 8 shows a pulse wave signal is added with an inverse pulse. The pulse plating can obtain a plating surface flatter than that obtained by way of rated voltage. But, the ions diffusing to the surface of the work piece naturally is limit in speed so that the plating is slow in speed too. Further, it only can maintain the original flatness instead of more flat plating surface even if the plating process is the best condition, i.e., the ions are distributed evenly. In addition, a further disadvantage is that it needs time to switch on or off the pulse power source instead of switching on or off instantaneously. An actual wave pattern for switching on or off the power source is shown in FIG. 9 and a section of voltage rise 310 is increasing gradually with insufficient plating current. Under the condition of insufficient plating current, the electrons will choose a position with shortest electrical swimming distance to extract the positive ions such that it is possible to produce tip part effect. This is why the flattering agent is still utilized while the method of pulse power input is applied.

Therefore, the electrons are influenced by the electric field in case of the preceding conventional methods being used for the plating operation so that the tip part jutting out of the surface of the work piece at the negative pole aggregates more electrons to result in the surface of the work piece being hard to become flat completely with projection areas thereon getting more extending outward and recess area thereon getting more dented.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a novel plating method, wherein the electric field and flowing current can be adjusted independently so that the positive ions will accumulate on the surface of the negative pole much faster than the incoming electrons. Under the influence of the electric field, positive ions will accumulate at the region closest to the field negative pole, where they will wait at the recess of the plating surface for electrons to arrive so electric extraction can proceed and perform the uniform plating.

Another object of the present invention is to provide an apparatus for performing the method for controlling field flow decouple plating so that the uneven surface of the negative pole will be flat after the plating.

Following the plating method of this invention, the placement of its electric poles includes a high voltage power source for the driving field for electrical swimming positive ions but it does not provide the plating current. The electric poles also include another low voltage high current power source for supplying the plating current slow and it is located at the inner of the poles of the high voltage power source. Therefore, by using the connected high voltage power source to control the electrical swimming speed of the positive ions to be faster than the electrons supplied by the low voltage high current power source, more positive ions will accumulate and await for incoming electrons so that the spiking effect of the electrons will not have time to occur. On the other hand, as the positive ions on the recess of the extraction negative pole is closest to the high voltage power source's negative pole which is positioned behind the extraction negative pole, the ions will be attracted by the static electrons of the high voltage power source and accumulate more rapidly in the recess and perform electric extraction with the electrons. Thus, the invention makes use of the fact that electric extraction is more preferable in the recess of the extraction negative pole compared to other regions; the uneven surface of the work piece at the negative pole will become flat naturally by the plating method of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reference to the following detailed description and accompanying drawings, in which: [0014]
FIG. 1 is a schematic diagram of a conventional apparatus for plating illustrating an arrangement of battery power source and two electric poles; [0015]
FIG. 2 is an enlarged schematic diagram illustrating the surface roughness of the negative pole shown in FIG. 1 and a reaction structure of positive ions electrically separating the rough surface; [0016]
FIG. 3 is a schematic diagram illustrating a state with regard to electric separating reaction of positive ion on the surface of the negative pole after the plating solution in the conventional plating apparatus being added with flatten agent; [0017]
FIGS. [0018] 4 to 9 are schematic diagrams illustrating a series states of reactions with regard to positive ions of an electric board being treated with conventional plating process under a condition of pulse power source;
FIG. 10 is a plan view of a layout with regard to a field power, an electric separation power source and all electric poles according to the present invention; and [0019]
FIG. 11 is a schematic diagram illustrating positive ions being electrically extracted between the field negative pole and the extraction negative pole shown in FIG. 10.[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 10, the present invention includes two sets of [0021] electric power sources 401, 405 in the plating device constituted by the driving field of electrical swimming and plating current. The field power source 401 is a field source for producing the electrical swimming metal positive ions. The positive of the field power source 401 is connected to the positive 402 of the driving field for electrical swimming, while its negative is connected to the negative of the driving field 403. The two electric poles 402, 403 are both covered with insulation material 404. The driving field for electrical swimming only provides the electric field for guiding the electrical swimming positive ions and does not provide the plating current. Therefore, by utilizing a high voltage and low current power source and insulation material 404, it will cut off the electrons from entering and thus prevent the surface of both positive and negative from being covered with ions or electric extraction. The plating power source 405 is used for producing the plating current. The positive pole thereof is connected to the positive pole 406 of the electrical swimming metal ions, which is located near the right surface of the field positive pole 402. While the negative pole 403 of the plating power source (405) is connected to the extraction negative pole 407 on the surface close to the field negative pole 403. The plating power source 405 is mainly for controlling the flow speed of the electron current, thus a low voltage and high current power source is being used.
According to the present invention, the respective pole of the field power source and the plating power source are first placed into the plating solution in a plating trough. When the [0022] field power source 401 and plating power source 405 form a closed circuit, an electrical swimming electric field is established between the two electric poles 402, 403 of the field power source and it is used to guide the electrical swimming metal positive ions in the plating solution 408. The purpose of the plating power source 405 is to produce plating current, which will cause the positive metal ions at the extraction negative pole to gain electrons and allow the electric extraction to perform the plating process at the extraction negative pole 407.
Referring to FIG. 11, indicated in this invention, due to the presence of the [0023] negative pole 403 of the driving field for electrical swimming, the positive metal ions are affected by it to create a flatness effect on the extraction negative pole 407 of the plating power source 405 and thus leading to the electric extraction on the extraction negative pole 407. In the present invention, by using a high voltage electric field power source 401 to control the faster electrical swimming speed of the positive ions and at the same time, using low voltage power source 405 to control the electrical extraction rate, more metal positive ions will accumulate on the surface of the extraction negative pole 407 as the electrical swimming speed is faster than the plating speed. When the height (409) of the surface of the extraction negative pole 407 is not uniform, positive ions will congregate towards the recess 410 of the extraction negative pole 407 under the attraction of the static electrons on the field negative pole 403, which is located behind the extraction negative pole 407. This leads to the positive ions tending to move closer to the field negative pole 403 and wait for new electron (411) to arrive on the extraction negative pole 407, in order to carry out electric extraction. Due to the plating solution volume of the invention on the extraction negative pole 407 has more recess regions than projecting regions; the final result of plating will tend to be uniform across the surface and thus achieving the goal of a flat plating surface.
The main feature of the present invention is in that two control factors, the driving field for electrical swimming and supply of the plating current, can be independently regulated. The number of poles can be four or it can be reduced to three in case of the two positive poles being combined together. The design of the circuit can also allow a single power source to generate individually controlled current and electrical field by way of the circuit control. It is noted that the driving field for electrical swimming and the extraction power source in the preceding description and in the following claims being explained separately is for the purpose of being understood easily. Hence, it does not have to provide two independent power sources and any change can be possibly done as long as the goal of the positive ions residing in the recess of the surface of the extraction negative pole and awaiting for electronic join and extraction can reach. [0024]
While the invention has been described with reference to a preferred embodiment thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention, which is defined by the appended claims. [0025]

Claims

What is claimed is:

1. A method for controlling field flow decouple plating, comprising following steps:

a driving field for electrical swimming being produced in plating solution;

a pair of ionic positive pole and extraction negative pole being connected to a plating power source placed in the plating solution;

positive metal ions on the ionic positive pole being controlled by the driving field for electrical swimming to move towards the extraction negative pole and the electric extraction taking place at a recess on the extraction negative pole surface.

2. The method for controlling field flow decouple plating according to claim 1, wherein the driving field for electrical swimming comprises a field positive pole and a field negative pole that are connected to a high voltage electric field power source and placed away from each other in the plating solution as well.

3. The method for controlling field flow decouple plating according to claim 1, wherein the ionic positive pole and the extraction negative pole in between the electric poles of the driving field for electrical swimming are connected to the corresponding positive and negative field poles.

4. An apparatus of field flow decouple plating, comprising:

a high voltage direct current power source for a driving field with electrical swimming, providing a first positive pole and a first negative pole;

a low voltage plating direct current power source, providing a second positive pole and a second negative pole;

plating solution, containing a driving positive pole and a driving negative pole for electrical swimming and the driving positive pole spacing apart from the driving negative pole, a driving positive pole and a driving negative pole for electric swimming, and a metal ionic positive pole and an extraction negative pole;

wherein, the first positive and first negative poles are connected to the driving positive pole and the driving negative pole respectively, the second positive pole is connected to the metal ionic positive pole and the second negative pole to the extraction negative pole, and the metal ionic positive pole and the extraction negative pole are disposed to oppose to the driving positive pole and the driving negative pole for electrical swimming respectively.

5. The apparatus of field flow decouple plating according to claim 4, wherein the first positive pole and the first negative pole are covered with insulation material.