CN111304720B

CN111304720B - Electroplating device and electroplating method

Info

Publication number: CN111304720B
Application number: CN201811518586.5A
Authority: CN
Inventors: 白蓉生; 黄荣山; 彭昶铭
Original assignee: Unimicron Technology Corp
Current assignee: Unimicron Technology Corp
Priority date: 2018-12-12
Filing date: 2018-12-12
Publication date: 2021-04-16
Anticipated expiration: 2038-12-12
Also published as: CN111304720A

Abstract

An electroplating device is provided, which comprises an upper tank body, a cathode, a first anode, a second anode, a lower tank body, a clapboard, a liquid conveying component and a pipe body. The partition board is used for separating the upper tank body and the lower tank body and is provided with at least one first drain hole and at least one second drain hole. The electroplating method includes setting the article to be plated in the electroplating device and opening and closing the first water draining hole and the second water draining hole successively for electroplating to form the through hole wall with high aspect ratio.

Description

Electroplating device and electroplating method

Technical Field

The present invention relates to an electroplating apparatus and an electroplating method, and more particularly, to an electroplating apparatus having two drain holes disposed opposite to each other and an electroplating method using the same.

Background

The traditional copper plating method of the circuit board is to place the circuit board in an electroplating bath to carry out electroplating by using electroplating solution. The through hole on the circuit board uses the nozzle of the electroplating bath to match with the high-voltage motor, so that the electroplating solution is sprayed into the through hole of the circuit board. This method of injecting the plating solution into the through-hole with an appropriate pressure is only applicable to a circuit board having a low aspect ratio (aspect ratio). Once the thickness of the circuit board is increased to greatly increase the aspect ratio of the through hole, the electroplating solution cannot enter the through hole smoothly, so that the wall of the through hole cannot be plated with the copper layer smoothly, and the quality of the product is low.

Therefore, when the aspect ratio of the through hole of the circuit board is getting larger and larger, the conventional method of providing the plating solution by using the nozzle together with the high-voltage motor cannot meet the requirement. How to improve the problem of poor hole wall electroplating caused by large aspect ratio of the through hole is a need for improvement in the prior art.

Disclosure of Invention

The invention aims to provide an electroplating device, which can uniformly electroplate the wall of a through hole of an object to be plated with a high aspect ratio.

The invention provides an electroplating device, which comprises an upper tank body, a cathode, a first anode, a second anode, a lower tank body, a partition board, a liquid conveying assembly and a pipe body. The cathode, the first anode and the second anode are arranged on the upper tank body, and the first anode and the second anode are respectively and correspondingly arranged on two opposite sides of the cathode. The lower groove body is arranged below the upper groove body, and the partition plate is arranged between the upper groove body and the lower groove body. The partition board is provided with at least one first drain hole and at least one second drain hole, so that the upper tank body is communicated with the lower tank body, wherein the first drain hole and the second drain hole are respectively arranged at two opposite sides of the cathode. The liquid conveying assembly is arranged on the lower tank body. The body contains first pipe portion and second pipe portion, and wherein first pipe portion is connected with liquid delivery component, and the top of cell body is located to the second pipe portion.

In some embodiments, the partition plate includes a control component for driving the first drain hole and the second drain hole to be selectively opened and closed.

In some embodiments, the cathode includes a cathode first portion and a cathode second portion, the cathode first portion being disposed opposite the cathode second portion.

In some embodiments, the number of the first drain holes is plural, and the first drain holes are arranged in a row.

In some embodiments, the number of the second drainage holes is plural, and the second drainage holes are arranged in a row.

In some embodiments, the body comprises an outer tube having a plurality of rows of drainage apertures formed through the outer tube in a region adjacent the top of the upper trough.

In some embodiments, the aperture size of the drain holes increases from the position of the outer tube relative to the cathode to the position of the outer tube relative to the first anode and the second anode.

In some embodiments, the pipe further comprises an inner pipe having an outlet hole, the inner pipe is disposed inside the outer pipe, the outlet hole is formed through the inner pipe in a region adjacent to the top of the upper tank body, and the outlet hole is communicated with the liquid discharge holes.

In some embodiments, the exit holes are substantially aligned with the cathode, and the aperture size of the drain holes increases from the position of the outer tube relative to the cathode to the position of the outer tube relative to the first anode and the second anode.

In some embodiments, the exit holes are substantially aligned with the first anode, and the aperture sizes of the liquid discharge holes are gradually increased from the arrangement of the outer tube relative to the first anode to the arrangement of the outer tube relative to the second anode; or the outlet holes are approximately aligned with the second anode, and the aperture sizes of the liquid discharge holes are gradually increased from the arrangement of the outer pipe relative to the second anode to the arrangement of the outer pipe relative to the first anode.

In some embodiments, the lower tank body includes a partition member, the partition member dividing the lower tank body into a first lower tank region and a second lower tank region, the first lower tank region being disposed below the first drain hole, the second lower tank region being disposed below the second drain hole.

In some embodiments, the liquid delivery assembly comprises a first pump and a second pump, wherein the first pump is disposed below the first drain hole and the second pump is disposed below the second drain hole; and the body still contains the third pipe portion, and wherein first pipe portion is connected with first pump, and the third pipe portion is connected with the second pump.

The present invention further provides a method of electroplating, comprising (1) providing an electroplating apparatus as described above; (2) providing an object to be plated, wherein a plurality of through holes penetrate through the object to be plated; (3) injecting electroplating solution into the upper tank body and the lower tank body; (4) electrically connecting the object to be plated with the cathode, wherein the object to be plated divides the upper tank body into a first tank and a second tank, the first drain hole is formed in the first tank, and the second drain hole is formed in the second tank; (5) providing electricity to the cathode, the first anode and the second anode to carry out an electroplating process, and opening the first drain hole to enable a part of electroplating solution arranged on the upper tank body to flow from the second tank to the first tank and then flow from the first tank to the lower tank body through the first drain hole; and (6) during the electroplating process, closing the first drain hole and opening the second drain hole, so that a part of the electroplating solution arranged on the upper tank body flows to the second tank from the first tank and then flows to the lower tank body from the second tank through the second drain hole.

In some embodiments, the step (5) further comprises continuously pumping the electroplating solution in the lower tank into the tube by the liquid delivery assembly, and then discharging the electroplating solution into the upper tank.

In some embodiments, the step (6) further comprises continuously pumping the electroplating solution in the lower tank into the tube by the liquid delivery assembly, and then discharging the electroplating solution into the upper tank.

In some embodiments, the object to be plated is a printed circuit board.

Electroplating is carried out by opening and closing the first drain hole and the second drain hole in sequence, so that the wall of the through hole of the object to be plated with high aspect ratio can be uniformly electroplated.

Drawings

The above and other structures, features and other advantages of the present invention will be more clearly understood by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of an electroplating apparatus according to the present invention.

FIG. 2 is a top view of an electroplating apparatus according to the present disclosure.

Fig. 3 is a cross-sectional view taken along line a-a of fig. 2.

Fig. 4 is a perspective view of another embodiment of the tube body of the electroplating device according to the present invention.

Fig. 5 is a perspective view of another embodiment of a tube body of the electroplating device according to the present invention.

Fig. 6 is a perspective view of another embodiment of a tube body of the electroplating device according to the present invention.

FIG. 7 is a perspective view showing a state of use of the plating apparatus according to the present invention.

[ description of main element symbols ]

100 electroplating device 10 upper tank body

11 first groove 12 second groove

20 cathode 21 cathode first part

22 cathode second portion 30 first anode

40 second anode 50 lower tank body

51 baffle 52 first lower trough area

53 second lower trough area 60 baffle

61 first drain hole 62 second drain hole

63 control assembly 70 liquid delivery assembly

71 first pump 72 second pump

80 pipe 81 first pipe part

82 second pipe part 821 liquid discharge hole

83 third pipe section 84 outer pipe

85 inner pipe 851 outlet hole

X-to-be-plated Y-through hole

Detailed Description

In order to make the description of the present invention more complete and complete, embodiments and examples of the present invention will be described with reference to the accompanying drawings; it is not intended to be the only form in which the embodiments of the present disclosure may be practiced or utilized. The following embodiments of the invention may be advantageously combined with or substituted for one another, or additional embodiments may be added to one embodiment, without further recitation or description.

Spatially relative terms, such as "lower" and "upper," are used herein to describe one element or feature's relationship to another element or feature in the figures. These spatially relative terms are intended to encompass different ways of using or operating the device in addition to what is shown in the figures. The device may be otherwise configured (e.g., rotated 90 degrees or otherwise) and the spatially relative descriptors used herein interpreted accordingly.

In this document, unless the context requires otherwise, the word "a" and "an" may mean "one" or "more". It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used herein, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

Fig. 1 is a perspective view of an electroplating apparatus according to an embodiment of the present disclosure, and fig. 2 is a top view of fig. 1. As shown in fig. 1 and 2, the electroplating apparatus 100 includes an upper tank 10, a cathode 20, a first anode 30, a second anode 40, a lower tank 50, a partition 60, a liquid delivery assembly 70, and a tube 80.

The cathode 20 is disposed on the upper tank 10, and the cathode 20 includes a cathode first portion 21 and a cathode second portion 22, and the cathode first portion 21 and the cathode second portion 22 are disposed opposite to each other. In some embodiments, the cathode first portion 21 and the cathode second portion 22 are in a concave shape in the top view of fig. 2, and are recessed away from each other, so that two sides of the object to be plated can be respectively engaged with the cathode first portion 21 and the cathode second portion 22.

The first anode 30 and the second anode 40 are disposed on the upper tank 10 and disposed on two opposite sides of the cathode 20, respectively. In some embodiments, the distance between the first anode 30 and the cathode 20 is about 10 cm to 30 cm, preferably 10, 15, 20, 25, or 30 cm. In some embodiments, the first anode 30 and the second anode 40 are coupled to a plating metal, wherein the plating metal includes, but is not limited to, gold, copper, aluminum, titanium tungsten, titanium, or chromium, etc. In some embodiments, the first and

second anodes

30, 40 are in the form of elongated plates.

The lower tank body 50 is disposed below the upper tank body 10. In some embodiments, the upper tank 10 and the lower tank 50 have a length of about 1 to 2 meters and a width of about 0.5 to 1 meter, and the total height of the upper tank 10 and the lower tank 50 is about 1 to 2 meters. The lower tank 50 includes a barrier 51, and the barrier 51 divides the lower tank 50 into a first lower tank area 52 and a second lower tank area 53.

The partition plate 60 is disposed between the upper tank 10 and the lower tank 50, the partition plate 60 has at least one first drainage hole 61 and at least one second drainage hole 62, such that the upper tank 10 is communicated with the lower tank 50, wherein the first drainage hole 61 and the second drainage hole 62 are disposed on two opposite sides of the cathode 20, respectively, the first drainage hole 61 is disposed above the first lower tank region 52, and the second drainage hole 62 is disposed above the second lower tank region 53. In some embodiments, the shapes of the first drainage hole 61 and the second drainage hole 62 include, but are not limited to, a circle or a polygon. In some embodiments, the number of the first drain holes 61 is plural, and the first drain holes 61 are arranged in a row and arranged in parallel with the first anode 30 in the shape of the long plate. In some embodiments, the number of the second water discharge holes 62 is plural, and the second water discharge holes 62 are aligned in a row and arranged in parallel with the second anode 40 in the shape of an elongated plate. In some embodiments, the first drainage holes 61 and the second drainage holes 62 are circular in shape and have a diameter of 0.5 inches to 5 inches, preferably 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 2.0, 2.5, 3.0, 4.0 or 5.0 inches. In some embodiments, the number of the first drainage holes 61 and the second drainage holes 62 is 10 to 100, preferably 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100. In some embodiments, the distance between two adjacent first drainage holes 61 or two adjacent second drainage holes 62 is 5 mm to 50 mm, preferably 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 mm.

The partition 60 includes a control unit 63, and the control unit 63 controls and drives the first drain hole 61 and the second drain hole 62 to be selectively opened and closed. In some embodiments, the control unit 63 controls the water stop plate to move below the first drain hole 61 or the second drain hole 62, so as to open or close the first drain hole 61 or the second drain hole 62, so that the plating solution disposed on a portion of the upper tank body 10 selectively flows into the first lower tank region 52 through the first drain hole 61 or flows into the second lower tank region 53 through the second drain hole 62.

Referring to fig. 1 to 3, the liquid conveying assembly 70 is disposed on the lower tank 50, and the liquid conveying assembly 70 includes a first pump 71 and a second pump 72, wherein the first pump 71 is disposed in the first lower tank area 52, i.e., below the first drain hole 61; the second pump 72 is provided below the second lower tank region 53, i.e., the second drain hole 62.

The pipe body 80 includes a first pipe portion 81, a second pipe portion 82, and a third pipe portion 83. The first pipe section 81 is connected to the first pump 71, the second pipe section 82 is adjacent to the top of the upper tank 10, and the third pipe section 83 is connected to the second pump 72. The second pipe portion 82 has a plurality of rows of liquid holes 821. In some embodiments, the first and

third duct portions

81, 83 converge along the lower portion of the separator 60 and then communicate upwardly with the second duct portion 82 disposed opposite the cathode 20. The diameter of the drain holes 821 increases from the position of the second pipe portion 82 with respect to the cathode 20 to the position of the second pipe portion 82 with respect to the first anode 30 and the second anode 40.

In some embodiments, please refer to fig. 1, 2 and 4, wherein the tube 80 of fig. 4 replaces the tube 80 of fig. 1. The pipe 80 further includes an outer pipe 84 and an inner pipe 85, and the drainage holes 821 are formed through the outer pipe 84 in the area near the top of the upper tank 10. The inner tube 85 is provided inside the outer tube 84, and the inner tube 85 has an outlet hole 851. An outlet hole 851 is formed through the inner pipe 85 in the region adjacent to the top of the upper tank 10, and the outlet hole 851 is in communication with the drain holes 821. In one embodiment, the exit holes 851 are substantially aligned with the cathode 20, and the aperture size of the liquid discharge holes 821 increases from the position of the outer tube 84 relative to the cathode 20 to the position of the outer tube 84 relative to the first anode 30 and the second anode 40. In another embodiment, please refer to fig. 1, fig. 2 and fig. 5, wherein the tube 80 of fig. 5 replaces the tube 80 of fig. 1. The exit holes 851 are substantially aligned with the first anode 30, and the diameters of the drain holes 821 increase from the position of the outer tube 84 relative to the first anode 30 to the position of the outer tube 84 relative to the second anode 40. In another embodiment, please refer to fig. 1, fig. 2 and fig. 6, wherein the tube 80 of fig. 6 replaces the tube 80 of fig. 1. The exit holes 851 are substantially aligned with the second anode 40, and the diameters of the drain holes 821 increase from the position of the outer tube 84 relative to the second anode 40 to the position of the outer tube 84 relative to the first anode 30. The diameter of the drain holes 821 can be adjusted as required, and the purpose of the invention is to discharge the plating solution from the drain holes 821 in the same amount, so as to reduce the disturbance of the plating solution in the upper tank 10.

Although the methods disclosed herein are illustrated below as a series of acts or steps, the order in which the acts or steps are presented should not be construed as a limitation of the present invention. For example, certain operations or steps may be performed in a different order and/or concurrently with other steps. Moreover, not all illustrated operations, steps and/or features may be required to implement an embodiment of the present invention. Further, each operation or step described herein may comprise several sub-steps or actions.

Another aspect of the present invention provides a method of electroplating, comprising the following steps.

(1) An electroplating apparatus 100 (shown in fig. 2 and 7) is provided.

(2) Providing an object to be plated X, wherein the object to be plated X is provided with a plurality of through holes Y which penetrate through the object to be plated X.

(3) The plating solution is poured into the upper tank 10 and the lower tank 50.

(4) The object to be plated X is electrically connected to the cathode 20, wherein the object to be plated X divides the upper tank 10 into a first tank 11 and a second tank 12, the first drain hole 61 is disposed in the first tank 11, and the second drain hole 62 is disposed in the second tank 12. In some embodiments, the object X to be plated may abut against the bottom of the upper tank 10, or the distance between the object X and the bottom of the upper tank is 0.1 cm to 100 cm, preferably 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 cm. In some embodiments, the object to be plated X is a printed circuit board having a plurality of through holes Y. Printed circuit boards include, but are not limited to, high-speed thick large boards (high-layer count). Compared with a common circuit board, the high-speed thick and large board has a large aspect ratio, so that the hole walls of the through holes Y are deep and long.

(5) The electrical equipment is provided to the cathode 20, the first anode 30 and the second anode 40 to perform the electroplating process, and the first drain hole 61 is opened, so that a part of the electroplating solution provided in the upper tank 10 flows from the second tank 12 to the first tank 11, and then flows from the first tank 11 to the lower tank 50 through the first drain hole 61. In some embodiments, in the step (5), the plating solution in the lower tank 50 is continuously pumped into the tube 80 by the liquid delivery assembly 70 and then discharged into the upper tank 10. In some embodiments, in step (5), the plating solution in the first lower tank region 52 is continuously pumped into the inner pipe 85 of the first pipe portion 81 by the first pump 71, and then discharged into the upper tank body 10 through the drain hole 821 of the second pipe portion 82. In some embodiments, the drain hole 821 is provided 5 cm to 10 cm below the liquid level of the upper tank 10. In the step (5), based on the principle of white effort, under the condition that the liquid delivery assembly 70 rapidly absorbs the electroplating solution and only opens the first drain hole 61, a part of the electroplating solution disposed in the upper tank body 10 flows from the second tank 12 to the first tank 11 through the through holes Y of the object to be plated X, so that the problem that the electroplating solution is not easily exchanged in the deep hole walls of the through holes Y is improved, and better electroplating quality is provided. In addition, in the step (5), the external pressure generated by the liquid delivery assembly 70 breaks through the surface tension between the electroplating solution and the openings of the through holes Y, and accelerates the flow velocity at the deep position of the through holes Y, so that the electroplating solution can fill the inner hole walls of the through holes Y.

(6) During the plating process, the first drain hole 61 is closed and the second drain hole 62 is opened, so that the plating solution disposed in a portion of the upper tank body 10 flows from the first tank 11 to the second tank 12, and then flows from the second tank 12 to the lower tank body 50 through the second drain hole 62. In some embodiments, in step (6), the plating solution in the lower tank 50 is continuously pumped into the tube 80 by the liquid delivery assembly 70 and then discharged into the upper tank 10. In some embodiments, in step (6), the plating solution in the second lower tank region 53 is continuously pumped into the inner pipe 85 of the second pipe portion 83 by the second pump 72, and then discharged into the upper tank body 10 through the drain hole 821 of the second pipe portion 82. In this step (6), when the first drain hole 61 is closed and the second drain hole 62 is opened, a portion of the plating solution disposed in the upper tank 10 flows from the first tank 11 to the second tank 12 according to the principle of "white effort", so that the through holes Y do not accumulate the plating thickness on the same side due to unidirectional water flow, thereby improving the uniformity of plating.

(7) The second drain hole 62 is closed during the plating process.

(8) And (5) repeating the steps (5) to (7) until the electroplating is finished.

The electroplating method of the invention enables the inner hole walls of the through holes Y to be uniformly electroplated by means of the first drain hole 61 and the second drain hole 62 in combination with the liquid conveying component 70. In addition, the first drainage hole 61 and the second drainage hole 62 are opened and closed alternately, so that the electroplating solution in the upper tank 10 is changed in different flow directions, and the uniformity of electroplating is improved.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. An electroplating apparatus, comprising:

an upper trough body;

the cathode is arranged on the upper groove body;

the first anode and the second anode are arranged on the upper tank body and respectively correspond to two opposite sides of the cathode;

the lower tank body is arranged below the upper tank body; and

the baffle is arranged between the upper tank body and the lower tank body and provided with at least one first drainage hole and at least one second drainage hole, so that the upper tank body is communicated with the lower tank body, wherein the first drainage hole and the second drainage hole are respectively arranged at two opposite sides of the cathode;

the liquid conveying assembly is arranged in the lower groove body;

the pipe body comprises a first pipe part and a second pipe part, wherein the first pipe part is connected with the liquid conveying assembly, and the second pipe part is arranged at the top of the upper groove body; and

a plating object having a plurality of through holes penetrating through the plating object, wherein the plating object is electrically connected to the cathode, wherein the plating object divides the upper tank into a first tank and a second tank, wherein the first drain hole is disposed in the first tank, the second drain hole is disposed in the second tank,

the lower tank body comprises a baffle piece which divides the lower tank body into a first lower tank area and a second lower tank area, the first lower tank area is arranged below the first drain hole, and the second lower tank area is arranged below the second drain hole.

2. The electroplating apparatus as claimed in claim 1, wherein the partition comprises a control member for selectively opening and closing the first drain hole and the second drain hole.

3. The plating apparatus of claim 1, wherein the cathode comprises a cathode first portion and a cathode second portion, the cathode first portion and the cathode second portion being disposed opposite one another.

4. The plating apparatus as recited in claim 1, wherein the first drain hole is plural in number, and said first drain holes are arranged in a row.

5. The plating apparatus as recited in claim 1, wherein the number of the second drain holes is plural, and the second drain holes are arranged in a row.

6. The electroplating apparatus as claimed in claim 1, wherein the tube comprises an outer tube having a plurality of rows of drain holes, the drain holes being formed through the outer tube in a region adjacent to the top of the upper tank.

7. The plating apparatus as recited in claim 6, wherein the drain hole has a diameter that increases from the position of the outer tube with respect to the cathode toward the position of the outer tube with respect to the first anode and the second anode.

8. The electroplating apparatus as claimed in claim 6, wherein the tube further comprises an inner tube having an outlet hole formed therein, the outlet hole being disposed through an area of the inner tube adjacent to the top of the upper tank, the outlet hole being in communication with the drain hole.

9. The electroplating apparatus of claim 8, wherein the exit aperture is substantially aligned with the cathode, and the drain aperture increases in diameter from the position of the outer tube relative to the cathode to the position of the outer tube relative to the first anode and the second anode.

10. The plating apparatus as recited in claim 8, wherein

The outlet hole is approximately aligned with the first anode, and the aperture size of the liquid discharge hole is gradually increased from the arrangement of the outer pipe relative to the first anode to the arrangement of the outer pipe relative to the second anode; or

The outlet hole is approximately aligned with the second anode, and the aperture size of the liquid discharge hole is gradually increased from the arrangement of the outer pipe relative to the second anode to the arrangement of the outer pipe relative to the first anode.

11. The plating apparatus as recited in claim 1, wherein

The liquid conveying assembly comprises a first pump and a second pump, wherein the first pump is arranged below the first drain hole, and the second pump is arranged below the second drain hole; and

the tube further comprises a third tube part, wherein the first tube part is connected with the first pump, and the third tube part is connected with the second pump.

12. A method of electroplating, comprising:

(1) providing the electroplating apparatus of claim 1;

(2) providing an object to be plated, wherein the object to be plated is provided with a plurality of through holes which penetrate through the object to be plated;

(3) injecting electroplating solution into the upper tank body and the lower tank body;

(4) electrically connecting the object to be plated with the cathode, wherein the object to be plated divides the upper tank body into a first tank and a second tank, the first drain hole is arranged in the first tank, and the second drain hole is arranged in the second tank;

(5) providing electricity to the cathode, the first anode and the second anode to perform an electroplating process, and opening the first drain hole to enable a part of the electroplating solution arranged on the upper tank body to flow from the second tank to the first tank and then flow from the first tank to the lower tank body through the first drain hole; and

(6) during the electroplating process, the first drain hole is closed and the second drain hole is opened, so that a part of the electroplating solution arranged on the upper tank body flows to the second tank from the first tank and then flows to the lower tank body from the second tank through the second drain hole.

13. The method as claimed in claim 12, wherein the step (5) further comprises discharging the plating solution in the upper tank after the plating solution in the lower tank is continuously pumped into the tube by the liquid delivery assembly.

14. The method as claimed in claim 12, wherein the step (6) further comprises discharging the plating solution in the upper tank after the plating solution in the lower tank is continuously pumped into the tube by the liquid delivery assembly.

15. The method of claim 12, wherein the object to be plated is a printed circuit board.