US20070108044A1

US20070108044A1 - Plating tank

Info

Publication number: US20070108044A1
Application number: US11/595,685
Authority: US
Inventors: Tomoji Okuda; Junji Mizumoto; Yutaka Kimura; Hiroki Omura
Original assignee: C Uyemura and Co Ltd
Current assignee: C Uyemura and Co Ltd
Priority date: 2005-11-08
Filing date: 2006-11-08
Publication date: 2007-05-17
Also published as: JP4711805B2; KR20070049551A; JP2007131869A; TW201127997A; TW200720489A; KR20110055494A; CN1962962A; TWI471461B; TWI437130B; KR101324018B1; KR101324017B1; CN1962962B

Abstract

Provides a plating tank that can transport platy work securely without causing abrasion and attain uniform plating quality and uniform plating film thickness. The shields are comprised of four shielding plates 108, 109, 112, and 113 on upper part and lower part of the thin plate board as follows. The restrict roller 304 is comprised of the roller stand body 120 which reaches until nearly upper end area's height of thin plate board and stood on upper face of the lower shielding plates 108, and the work-end deviation preventing member 122.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The entire disclosure of Japanese Patent Application No. 2005-300255 including specification, claims, drawings and summary are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the skill which is used for electroplating a platy work, for example printed board etc., by a surface treatment device like an electroplating device.

BACKGROUND ART

A conventional surface treatment device like an electroplating device treats a platy work which is secured to a rack as to transfer without swinging. However, the surface treatment device of rackless type is suggested, because it is bothering task to mount the platy work in the rack and it is so large load that the device grows in size.
As a surface treatment device of rackless type like this, Japanese Laid Open Patent Application No. 2002-363796 (Patent Document 1) is known. Referring to FIG. 14 and FIG. 15, the structure of the surface treatment device will be described as follows. FIG. 14 shows plane view of the surface treatment device 300 from upside. FIG. 15 shows side view of the surface treatment device 300 from α-direction.
As shown in FIG. 14 and FIG. 15, the surface treatment device 300 is the surface treatment device of so-called pusher type, and has guide rails 10-13 for transporting the transport hanger 15 which is holding the platy work such as a printed board. Along with these guide rails 10-13, the surface treatment device 300 has the pre-treatment tank 1 of each type for processing before plating, plating tank 2 for electroplating, recovery tank 3 and water-washing tank 4 for processing after plating, unload section 5 for unloading the platy work, exfoliate tank 6 for separating plating films (hanger restoring process), water-washing tank 7 for water-washing the transport hanger 15 after separating, and load section 8 for loading a board.
As rise-and- fall guide rails 10, 12 shown in FIG. 14 falls, the platy work W is dipped into various tanks (e.g., plating tank 2, exfoliate tank 6, water-washing tank, and hot water-washing tank, cleaner tank, etc.). Also, when Rise-and- fall guide rails 10, 12 are fallen as shown in FIG. 15, guide rails 10-13 configure one circular guide rail.
By falling of rise-and- fall guide rails 10, 12 shown in FIG. 14, the platy work W is guided into treatment liquids on a dipping position ((x) position of FIG. 14) of the plating tank 2. The platy work W dipped into treatment liquids is transferred inside the platy tank 2.
The transport hanger 15 used for the surface treatment device 300 of the above-mentioned so-called pusher type, as shown FIG. 9, has treating-object holding member 47 with plural clamps 48 for holding the platy work W, slide member 35 which contact slidably with guide rails such as fixed guide rail 11, and connecting members 44 for connecting such members. The transport hanger 15 holds the upper end of the platy work W by clamp 48.
For the purpose to achieve uniform plating quality or uniform plating film thickness, the surface treatment device 300 of pusher type like the above-mentioned treats the platy work W by spouting jet flow of treatment liquids to the platy work W from spouters arranged both sides of the platy work W inside the platy tank. However, because it doesn't use the rack, the plating film thickness of platy work W became non-uniform as the platy work W swings when transporting and the distance to electrode is not constant, or the plating film thickness of the edge of the platy work became thicker unusually because current concentration has occurred on the edge of the platy work.
Therefore, it is big issue to be solved for the surface treatment device of rackless type to restrict swinging of the platy work and not to occur current concentration on the edge of the platy work W.
Consequently, the above-mentioned Patent Document 1 discloses interval between adjacent platy works of back-and-forth is adjusted by fast-forwarding until it becomes predetermined distance (for example, 50 mm) inside the plating tank 2 to prevent from occurring current concentration on the back-and-forth end of the platy work W. Additionally, a linear guide made of Teflon (registered trademark) is attached inside of a surface treatment tank such as a plating tank for preventing the platy work W from swinging, or a shielding plate is attached for preventing from occurring current concentration on the edge of the platy work W (Refer to the Japanese Laid Open Patent Applications No. 2000-178784 (Patent Document 2) and No. 2002-13000 (Patent Document 3)).
Moreover, when the printed board (thickness is below 0.1 mm) is used as the platy work (hereinafter referred to as thin plate board), it is suggested that leading guide etc. as shown in FIG. 16 is arranged inside a tank for the purpose of dipping the platy work W smoothly into each treatment tank (Refer to the Japanese Laid Open Patent Applications No. 2004-346391 (Patent Document 4).
The leading guide of Patent Document 4 is comprised of a pair of commutate members 131 (slant down flow boards 131 a, 131 b) placed at falling position of the thin plate board. As shown in FIG. 16, the slant down flow boards 131 a, 131 b are formed its upper side like as V style. And spouting tubes 132 are arranged along upper end area of the slant down flow boards 131 a, 131 b. Further, a liquid suction tube 133 is arranged on lower part of the slant down flow boards 131 a, 131 b, which aspirates plating liquids and spouts it from the spouting tubes 132. Therefore, it becomes possible to guide the thin plate board promptly with the flow on the lower side spouting from the slant down flow boards 131 a, 131 b.
However, the above-mentioned conventional art can't achieve uniform plating quality by jet flow of plating liquids or uniform plating film thickness by preventing from occurring current concentration on the upper and lower end of the platy work W, though it was possible to prevent current concentration on the back-and-forth end of platy works.
For instance, although Patent Documents 2 and 3 discloses that a louver is used for achieving uniform plating quality by commutating the jet flow of plating liquids, the plating efficiency or plating quality may get worse as it may occur excessive current shielding effect in some cases. Also, although shielding plate is arranged on the lower end of the platy work W, enough effect was not attained because currency detouring occurs in some cases. Thus, it is likely to vary plating thickness as occurring current concentration on the upper and lower end of the platy work W.
Further, although a linear guide made of Teflon is used for preventing the platy work W from swinging, linear shaped Teflon was easily to break away by touching with platy work W. Therefore, sometimes it is not prevented platy work W from swinging. Further, although it is possible to add metal wire as a core member to the linear guide made of Teflon, when plastic Teflon is broken away and metal wire became exposed, it was caused abrasion on the platy work W by touching with exposed metal wire, and plating quality became worse because the plating adhered to the metal wire is mixed in treatment liquids. Especially, when the thin plate board (thickness is below 0.1 mm) is used, it is subject to swing and twist easily because of plating jet flow. And it is subject to cause abrasion as transporting slidably with platy work W.

SUMMARY OF THE INVENTION

As to solve the above problems, an object of the present invention is to provide a plating tank used for a surface treatment device such as a electroplating device (especially, for the electroplating device which transports a platy work such as printed board in holding vertically) which can transport platy work such as thin printed board (thickness is below 0.1 mm) securely without causing abrasion, and attain uniform plating quality and uniform plating film thickness.
A plural of Independent aspects of the present invention will be indicated as follows.
(1) In accordance with characteristics of the present invention, there is provided a plating tank comprising:
a treatment tank main body for holding treatment liquids which is arranged as extending in transporting direction of the platy work;
a positive electrode;
a spouter for spouting the treatment liquids to the said platy work from lateral side of the treatment tank main body;
a restrict roller having a plural of rollers, wherein the rollers are attached rotatably from upper part until lower part of the treatment tank main body and arranged consecutively in transporting direction of the platy work as sandwiching both sides of the platy work on moving inside the treatment tank main body;
a current shield for preventing from occurring current concentration on the end of the platy work.
Therefore, it becomes possible to maintain upright state of the thin plate board W by restrict roller. Also, it doesn't cause abrasion as roller is used. It becomes possible to treat uniformly.
(2) In accordance with characteristics of the present invention, there is provided a plating tank:
wherein the said restrict roller is comprised of a plural of roller stand bodies which are having plural rollers vertically, and arranged in transporting direction of the said plating work, and interval on the spouting position of the spouter between adjacent roller stand bodies are wider than the other intervals.
Therefore, it becomes possible to provide treatment liquids with platy work (especially, thickness is below 0.1 mm) uniformly by spouter, and it becomes possible to maintain upright state of the thin plate board W by restrict roller. Also, it doesn't cause abrasion as roller is used. It becomes possible to treat uniformly.
(3) In accordance with characteristics of the present invention, there is provided a plating tank:
wherein a deviation preventing member is placed at lower end area of the platy work where the spouting position of the spouter is placed as sandwiching both sides of the platy work on moving.
Therefore, it becomes possible to prevent from bending on the lower end of platy work (especially, thickness is below 0.1 mm) properly.
(4) In accordance with characteristics of the present invention, there is provided a plating tank:
wherein the rollers are arranged at least one per predetermined unit area in a region that the restrict rollers are arranged.
Therefore, it becomes possible to prevent from swinging or twisting of platy work (especially, thickness is below 0.1 mm) in transporting direction or vertical direction and to maintain intervals between platy work and positive electrode constantly. It becomes possible to attain uniform of plating film thickness.
(5) In accordance with characteristics of the present invention, there is provided a plating tank:
wherein the said restrict roller is comprised of a plural of roller stand bodies which are having plural rollers vertically, and arranged in transporting direction of the said plating work, and vertical intervals that the rollers of the restrict roller is arranged are range from 50 mm to 100 mm.
Therefore, it becomes possible to prevent from swinging or twisting of platy work (especially, thickness is below 0.1 mm) in transporting direction or vertical direction and to maintain upright state. It becomes possible to maintain intervals between platy work and positive electrode constantly and to attain uniform of plating film thickness.
(6) In accordance with characteristics of the present invention, there is provided a plating tank:
wherein the said restrict roller is comprised of a plural of roller stand bodies which are having plural rollers vertically, and arranged in transporting direction of the said plating work, and the rollers placed over predetermined height differs the vertical position mutually between the roller stand bodies.
Therefore, it becomes possible to prevent from causing electrical shielding effect at same height. It becomes possible to prevent from occurring unevenness of plating and to attain uniform plating.
(7) In accordance with characteristics of the present invention, there is provided a plating tank:
wherein the said current shield is comprised of a upper shielding plate for preventing from occurring current concentration on the upper end of the platy work and/or a lower shielding plate for preventing from occurring current concentration on the lower end of the platy work.
Therefore, it becomes possible to prevent current concentration on both upper and lower end of platy work. It becomes possible to attain uniform of plating film thickness.
(8) In accordance with characteristics of the present invention, there is provided a plating tank:
wherein the said upper shielding plate and/or the lower shielding plate are comprised of plural shielding plates arranged between the said platy work and the said positive electrode, and its overlap with the platy work is the smaller, the closer to the platy work.
Therefore, it becomes possible to prevent from detouring of currency by shielding plate. It becomes possible to attain uniform of plating film thickness even if the shielding area of platy work is small. Also, it is possible to enhance productivity as gaining enough current shielding effect without decreasing current value.
(9) In accordance with characteristics of the present invention, there is provided a plating tank:
wherein the said plurality of shielding plates are formed in a unified manner and able to rise and fall.
Therefore, it becomes possible to attain uniform of plating film thickness even if the size of platy work is varied.
The other aspects of the present invention will be indicated as follows.
(a) In accordance with characteristics of the present invention, there is provided a platy work dipping device, comprising:
a treatment tank for dipping a platy work into treatment liquids;
a board guide for guiding platy board falling into the treatment tank having a upper guide board and a lower guide board, wherein the lower guide plate is arranged parallel spacing predetermined distance and upper board guide is arranged like taper as widening toward upside vertically and having slit of cutout, and a tip of upper board guide is projecting from fluid level and dipping its slit into plating liquids;
a liquid current generator arranged outside the said board guide.
Therefore, it becomes possible to guide a platy work smoothly along board guide, as liquid flow from outside of board guide can be led to downward inside the board guide through cutout. Especially, if treatment liquids are acid cleaner including fizzy material like surface-active agent, it is possible to prevent deterioration in plating quality which cause by bubble generated on fluid level and to guide platy board smoothly.
(b) In accordance with characteristics of the present invention, there is provided a platy work dipping device:
wherein the liquid current generator is sparger for spouting jet flow against the said cutout nearly in a horizontal direction, or air-bubbling tube arranged at nearly middle height inside the treatment tank.
Therefore, it becomes possible to guide a platy work smoothly along board guide, as liquid flow from sparger can be led to downward inside the board guide through cutout without occurring bubble on fluid level inside the board guide.
(c) In accordance with characteristics of the present invention, there is provided a platy work dipping device:
wherein the liquid current generator is sparger for spouting jet flow toward upper part than the said cutout in upper direction against a horizontal direction.
Therefore, it becomes possible to guide a platy work smoothly along board guide, as liquid flow from sparger toward upper part in upper direction against a horizontal direction can be led to downward inside the board guide through cutout without occurring bubble on fluid level inside the board guide.
(d) In accordance with characteristics of the present invention, there is provided a platy work dipping device:
wherein liquid current generator is air-bubbling tube discharging air upwards.
Therefore, it becomes possible to guide a platy work smoothly along board guide by simple structure, as liquid flow from air-bubbling tube which discharging air upwards can be led to downward inside the board guide through cutout without occurring bubble on fluid level inside the board guide.
(e) In accordance with characteristics of the present invention, there is provided a platy work dipping method for guiding a platy work falling into the treatment body by using a board guide:
projecting a tip of upper board guide from fluid level and dipping its slit into plating liquids;
generating by liquid current generator arranged outside the said board guide and under fluid level;
falling and dipping a platy work into treatment liquids.
Therefore, it becomes possible to guide a platy work smoothly along board guide, as liquid flow from outside of board guide can be led to downward inside the board guide through cutout. Especially, if treatment liquids are plating liquids, it is possible to prevent deterioration in plating quality which cause by bubble generated on fluid level and to guide platy board smoothly.
The characteristics of the present invention are broadly indicated as noted above, but structure, contents, object, and features will be clear though reference to the figures and according to the following disclosure.

BRIEF DESCRITION OF THE DRAWINGS

FIG. 1 shows α-α cross-section of plating tank 2 (FIG. 14).
FIG. 2 shows the structure of inside plating tank 2 from β-direction of FIG. 1.
FIG. 3 shows plane view of plating tank 2 from γ-direction of FIG. 1.
FIG. 4 shows detail structure of roller stand body from β-direction of FIG. 1.
FIG. 5 shows detail structure of deviation preventing member 122 (122 a, 122 b).
FIG. 6 shows detail structure of board dipping device 600.
FIG. 7 shows perspective view of board guide 62.
FIG. 8 shows detail structure of jet nozzle 64.
FIG. 9 shows detail structure of the transport hanger 15.
FIG. 10 shows cross-section near the center of the transport hanger 15.
FIG. 11 shows plane view of intermittent transporter 17 on the rise-and-fall guide rail 10.
FIG. 12 shows the structure of positioning transporter 18.
FIG. 13 shows the structure of board dipping device.
FIG. 14 shows plane view of surface treatment device 300 from upside.
FIG. 15 shows side view of surface treatment device 300 from α-direction.
FIG. 16 shows the structure of conventional leading guide.
FIG. 17 shows the structure of spouter 302.
FIG. 18 shows the structure of shields (shielding means) 303.
FIG. 19 shows view of support connecting member 216 from thin plate board W's side.
FIG. 20 shows the structure of positive electrode 102.
FIG. 21 shows overlapping range of thin plate board W and shielding plate.
FIG. 22 shows the structure of roller stand body 120's lower part.
FIG. 23 shows the view of swinging board W from transporting direction.
FIG. 24 shows the view of swinging board W from upside of plating tank.
FIG. 25 shows the structure of roller stand body 120's upper end.
FIG. 26 shows relationship between number of roller 116 and predetermined area of thin plate board W to be transported.

DETAILED DESCRIPTION OF DESIRED EMBODIMENTS

1. Plating Tank
The basic structure of the surface treatment device is the same as shown in FIG. 14 and FIG. 15. FIG. 14 shows plane view of surface treatment device 300 from upside. FIG. 15 shows side view of surface treatment device 300 from α-direction.
As shown in FIG. 14 and FIG. 15, the surface treatment device 300 is the surface treatment device of so-called pusher type, and having guide rails 10-13 for transporting the transport hanger 15 which is holding the platy work such as a printed board, and arranged such that along these guide rails 10-13, the pre-treatment tank 1 of each type for processing before plating, plating tank 2 for electroplating, recovery tank 3 and water-washing tank 4 for processing after plating, unload section 5 for unloading the platy work, exfoliate tank 6 for separating plating films (hanger restoring process), water-washing tank 7 for water-washing the transport hanger 15 after separating, and load section 8 for loading a board.
As rise-and- fall guide rails 10, 12 shown in FIG. 14 falls, the platy work W is dipped into various tanks (e.g., pre-treatment tank 1, plating tank 2, recovery tank 3 and water-washing tank 4, and exfoliate tank 6). Also, when Rise-and- fall guide rails 10, 12 has fallen as shown in FIG. 15, guide rails 10-13 configure one circular guide rail.
FIG. 1 shows α-α cross-section of plating tank 2 (FIG. 14) as one embodiment of the present invention. A treatment tank main body 100 (including after-mentioned overflow tank 202, drain 200) is holding treatment liquids. The thin plate board W (platy work), which is to be treated in the treatment tank main body 100 filled with treatment liquids, is held and hung by clamping of the transport hanger 15 on its upper end. By transferring the transport hanger 15, the thin plate board W also moves inside the treatment tank main body 100.
The treatment tank main body 100 is comprised of positive electrode 301 for supplying metal ion of electroplating, spouter 302 for spouting treatment liquids toward the thin plate board W, shielding means 303 for shielding currency not to occur current concentration on the edge of the thin plate board W, restrict roller 304 arranged as sandwiching the thin plate board W for keeping the thin plate board W on standing state when moving in the treatment tank main body 100. Furthermore, the concrete structure of the positive electrode 301, the spouter 302, the shielding means 303, the restrict roller 304 will be described as follows.
The positive electrode 301 is comprised of a pair of positive electrodes 102, 104 which is arranged plenty with keeping a predetermined interval along transporting direction of the thin plate board W, and power supply rail 224 which is arranged in the treatment tank main body 100 along transporting direction of the thin plate board W for suspending and energizing positive electrodes 102, 104 shown in FIG. 1.
The spouter 302 is comprised of eductor box 204 for equalizing pressure of plating liquids, a pair of spargers 106 for spouting plating liquids from both sides of the thin plate board W at nearer position to the thin plate board W than positive electrodes 102, 104, pipe 210, and circulation pump 208 for returning plating liquids through the pipe 210 to the eductor box 204 after filtering discharged through drain 200 or overflow tank 202 by barrier filter shown in FIG. 1.
The shielding means 303 is comprised of following four shielding plates shown in FIG. 1. The lower board shielding plates 108 are arranged with facing at lower end of the thin plate board W close to the thin plate board W along transporting direction of the thin plate board W. On the other hand, the upper board shielding plates 109 are arranged with facing at upper end of the thin plate board W close to the thin plate board W along transporting direction of the thin plate board W as well. Also, between positive electrode 102, 104 and sparger 106, the lower electrode shielding plate 112 is arranged around lower end area of positive electrode 102, 104 and the upper electrode shielding plate 113 is arranged around upper end area of positive electrode 102, 104 close to positive electrode 102, 104 along transporting direction of the thin plate board W respectively. Also, the shielding means 303 has a height adjuster 220 for adjusting height of lower board shielding plates 108 and lower electrode shielding plate 112 based on size of the thin plate board W. Left side of FIG. 1 indicates lowered condition corresponding to large sized thin plate board W and right side of FIG. 1 indicates heightened condition corresponding to small sized thin plate board W.
The restrict roller 304 is comprised of the roller stand body 120 which reaches until nearly upper end area's height of thin plate board and stood on upper face of the lower shielding plates 108, and the work-end deviation preventing member 122. The restrict roller 304 is possible to adjust a height based on size of the thin plate board W with lower board shielding plates 108 and lower electrode shielding plate 112 by the above-mentioned height adjuster 220.
The roller stand body 120 is comprised of shaft 114 which stands on the lower board shielding plate, and roller 116 which is attached vertically on the shaft 114 and rotatably. Also, it is possible to secure the roller 116 to shaft 114 and to rotate itself the shaft 114.
Concretely, as shown in FIG. 4 that shows detail structure of roller stand body from β-direction of FIG. 1, the roller stand body 120 has the roller 116 formed by PP (Polypropylene) resin, and adjusting member 116 e which adjust each distance between upper and lower rollers by putting shaft 114 to each insert hole and intermediating between upper and lower rollers. Further, securing member 116 g is attached around upper end area of the shaft 114 for the roller 116 and the adjusting member 116 e not to be tripped.
As shown in FIG. 25, the securing member 116 g is attached as spacing clearance (L70) from upper end of top roller 116. Therefore, as the roller 116 can float in plating liquids, it will be prevented from rotating improperly based on scratching between each roller 116 and adjusting member 116 e, and further be prevented from causing abrasion based on contact between the thin plate board W and roller 116.
FIG. 2 shows the structure of inside plating tank 2 from β-direction of FIG. 1. It is indicated that a number of the roller stand body 120 is arranged toward transporting C-direction of the thin plate board W.
FIG. 3 shows plane view of plating tank 2 from γ-direction of FIG. 1. The thin plate board W is transported between facing roller stand bodies 120. Thus, the thin plate board W is transported with right state (maintaining upright state) because the roller 116 of roller stand body 120 restricts the thin plate board W. By the way, the restrict roller 304 has roller stand body 120 and roller 116 for maintaining upright state (right state) as shown below.
First, the arrangement of the roller stand body 120 will be described. As shown in FIG. 22, facing roller stand bodies 120 are arranged as the distance L40 between roller 116 and thin plate board W becomes from 1 mm to 5 mm (e.g., this case is 4 mm). If the distance is below 1 mm, it may cause abrasion on surface of the thin plate board W as the roller 116 contacts with thin plate board W. Also, if the distance is over 5 mm, it may cause non-uniform of plating film thickness as the thin plate board W is distorted vertically.
Also, intervals L3 between roller stand body 120 are wider than the other intervals L2 at the position where sparger 106 is placed (indicated as N in FIG. 4) in this embodiment. Interval L3 is lager than diameter of the roller 116 at the position N where the sparger 106 is placed in this embodiment. Interval L2 is smaller than diameter of the roller 116 at the other position. Therefore, it is possible to spread jet flow of plating liquids on the thin plate board W effectively as the roller stand body 120 doesn't interfere with jet flow of plating liquids which is discharged by the sparger 106.
However, because of the said large intervals L3, it may be caused bending of the thin plate board W at the position based on jet flow of the sparger 106, or incomplete transporting as bent part intrudes between the roller stand bodies 120. Therefore, deviation preventing member 122 a is placed at lower part of the roller stand body 120, and deviation preventing member 122 b is placed at middle height of the roller stand body 120 in this embodiment. Especially, it is important that the deviation preventing member 122 a, which is for preventing lower end of the thin plate board W from bending, is placed at lower end part.
FIG. 5 shows detail structure of deviation preventing member 122 (122 a, 122 b). FIG. 5A shows plane view, and FIG. 5B shows side view. As shown in FIG. 5, deviation preventing member 122 a is obviously secured to lower part of shaft 114 (0-50 mm from top face of the lower board shielding plate 108, especially in the range of 0-20 mm: 5 mm, in this case). While the roller 116 is attached rotatably, the deviation preventing member 122 a doesn't rotate. Also, as shown in FIG. 5A, transporting space 124 of the thin plate board W is formed between facing deviation preventing members 122 a. In this way, it is prevented from that bent part intrudes between the roller stand bodies 120, or that deviates from lower board shielding plate 108. Furthermore, the structure of deviation preventing members 122 b is same as deviation preventing members 122 a.
Next, the arrangement of the rollers will be described. As shown in FIG. 26 in the region that 10-12 units of roller stand bodies 120 are arranged, there is at least one roller per predetermined unit area (e.g. 100 mm×100 mm). The region that the roller stand bodies 120 are arranged means region viewed where the roller stand bodies 120 are arranged in a transporting direction of the thin plate board W from a direction perpendicular to the transporting direction on as shown in FIG. 26. On the region, it is possible to reduce swinging of the thin plate board W effectively, by arranging at least one the rollers 116 for restricting swing per predetermined unit area against the thin plate board W in the region. The reason why based on this per predetermined unit area for arranging roller is to restrict both swings toward transporting direction and vertical direction. Furthermore, predetermined unit area is desirable up to 100 mm×100 mm.
Therefore, it becomes possible to prevent non-uniform plating film thickness occurring from that the thin plate board W loses erectness by jet flow of plating liquids and a distance from positive electrode 102, 104 changes as shown in FIG. 23 and 24. And, it becomes possible to prevent incomplete transport occurring from that the tip of thin plate board W swings and intrudes between the roller stand bodies 120. Furthermore, FIG. 24 shows the view of swinging board W from upside of plating tank.
Vertical intervals between adjacent rollers 116 of the roller stand bodies 120 are 50-100 mm. The vertical Intervals mean the intervals of circular plates of rollers 116 (L30 shown in FIG. 4). If it is below 20 mm, the rollers 116 cause electrical shielding effect against the thin plate board W, and it may be caused non-uniform plating film thickness. On the other hand, if it is over 100 mm, thin plate board W is bent between rollers 116 and lose erectness, and it may be caused non-uniform plating film thickness by varying a distance of the thin plate board W to the positive electrode 102, 104 vertically and locally as shown in FIG. 23. Furthermore, FIG. 23 shows the view of swinging board W from transporting direction.
Further, FIG. 4 shows arranging condition of the roller stand body 120. In the arrangement of plural roller stand bodies 120, the roller stand bodies 120 of 10-12 numbers arranged in transport direction of thin plate board W are forming one unit, and the height of each roller 116 is different from the others. For example, there is no roller which is same height H as roller 116 a of center area (at predetermined height: for example, at higher position over 50 mm from lower end of the platy work). There is no roller which is some height as the others. This is for the reason that linear unevenness of plating is not to be formed on thin plate board W by contacting with roller 116 at same height, and the plating film thickness on the surface of thin plate board W is not to be getting thinner by forming electrical shadows of the roller 116 at same height part.
However, the rollers on lower part of the roller stand bodies 120, below 50 mm from top face of lower board shielding plate 108, are allowed to be positioned at same height. The bottom roller 116 b of the roller stand bodies 120 is arranged at below 50 mm, especially below 20, from top face of lower board shielding plate 108. This is for the reason that, the lower end of thin plate board W is raised, if the thin plate board W loses erectness by jet flow of plating liquids as shown in FIG. 23. As the bottom roller is arranged as closer as possible to the lower end of the thin plate board W, it is prevented that the lower end of the thin plate board W deviates from clearance formed by lower board shielding plate 108.
As mentioned previously, the roller stand body 120 is formed standing on the lower board shielding plate 108, and moves up and down with the lower board shielding plate 108 integrally. Therefore, the positional relationship between lower board shielding plate 108 and bottom roller 116 b of roller stand body 120, or deviation preventing member 122 a doesn't change if the height is adjusted based on size of the thin plate board W. The simple structure makes it possible to be operated against various sized thin plate board W in the same way.
Thus, the restrict roller 304 in this embodiment regulates five elements to improve quality of electroplating, and the arrangement of roller 116 is determined. That is, the arrangement of roller 116 is determined for (i) keeping upright condition of the thin plate board W, (ii) reducing current shield effect by roller 116, iii), keeping effect of plating jet flow by spouter iv) preventing incomplete transport occurring from that the thin plate board W intrude between roller stand body 120, v) preventing from causing abrasion by roller 116.
Concretely, to establish the above (i) the roller 116 is arranged at least one per predetermined unit area (e.g. 100 mm×100 mm) basically. Further, a distance between roller 116 and thin plate board W is determined as range 1-5 mm (below 5 mm) and a interval between vertical rollers 116 is determined as range 50-100 mm (below 100 mm) to restrict vertical deflection of the thin plate board W more effectively. To establish the above (ii), a interval between vertical rollers 116 is determined as range 50-100 mm (over 50 mm), and the rollers 116 placed over predetermined height differs the vertical position mutually between the roller stand bodies 120 of 10-12 numbers. To establish the above (iii), intervals L3 between roller stand body 120 are wider than the other intervals at the position where sparger 106 is placed. To establish the above (iv), the rollers on lower part of the roller stand bodies 120 are allowed to be positioned at same height, and deviation preventing member 122 a is placed where the roller stand bodies 120 are arranged spacing the above intervals L3, and the roller stand body 120 where sparger 106 is not placed is spaced Interval L2 which is smaller than diameter of the roller 116. Lastly, to establish the above (iv), the securing member 116 g secures as spacing clearance from upper end of top roller 116 and thin plate board W is determined as range 1-5 mm (over 1 mm).
Although each combination of them can be selected accordingly, it is desirable to be provided entirely.
FIG. 17 shows the structure of spouter 302 excluding positive electrode 301, restrict roller 304 and shielding means 303. As shown in FIG. 17, spouter 302 spouts treatment liquids by sparger 106 toward the thin plate board W.
Plating liquids spouted from sparger 106, is discharged from the treatment tank main body 100 through drain 200 or overflow tank 202, and returns to eductor box 204 by circulation pump 208 through the pipe 210 after filtering by barrier filter 209, and returns to sparger 106 again as circulating after equalizing pressure of plating liquids in eductor box 204.
Plural eductor boxes 204 are arranged on the bottom of the treatment tank main body 100 along transporting direction of the thin plate board W. As shown in FIG. 17, eductor boxes 204 are bolted on the bottom plate of the treatment tank main body 100 as height adjustable. On the side plate of eductor box 204, connecting hole is formed and pipe 210 is connected for transferring liquids. Also, support member 204 a is attached to the eductor box 204, which prevents that it becomes impossible to equalize pressure of plating liquids by changing shape based on pressure of plating liquids transferred from circulation pump 208.
As shown in FIG. 17, spargers 106 is formed by attaching plural jet nozzles 106 a for spraying plating liquids to nozzle tube 106 b with spacing predetermined intervals. The nozzle tube 106 b is stood on eductor box 204, and eductor box 204 and lower end of nozzle tube 106 b are connected through connecting hole for transferring liquids. On the other hand, upper end of the sparger 106 is fit in hole formed on the nozzle fixing member which is attached along transporting direction of the thin plate board W. Therefore, jet flow of plating liquids against the thin plate board W is constant, as the sparger 106 is prevented from leaning (tumbling) to the opposite side of the thin plate board W or from vibrating by spouting pressure when spouting plating liquids.
As shown in FIG. 17, jet nozzle 106 a of spargers 106 are arranged at alternate height between right side and left side of the thin plate board W. This is to make difference in jet pressure of plating liquids on the thin plate board W and to realize flow transferring inside thorough-hole formed on the thin plate board W.
FIG. 18 shows the structure of shielding means 303 excluding positive electrode 301 and a portion of spouter 302. As shown in FIG. 18, shielding means 303 is comprised of upper board shielding plates 109, upper electrode shielding plate 113, lower board shielding plates 108, and lower electrode shielding plate 112 having a rolling mechanism, plate 110 and support connecting member 216 for connecting lower board shielding plates 108 and lower electrode shielding plate 112 integrally, height adjuster 220 for elevating lower board shielding plates 108 and lower electrode shielding plate 112 integrally, and guide table 214 for guiding lower electrode shielding plate 112 when adjusting height, and pole 155.
As shown in FIG. 18, upper board shielding plates 109 and upper electrode shielding plate 113 are attached to nozzle fixing member 212. The upper board shielding plates 109 and the upper electrode shielding plate 113 are height adjustable up and down in drawing respectively, because of having long hole of up and down direction in drawing and bolting on nozzle fixing member 212 through the long hole.
In this way, upper board shielding plates 109 and upper electrode shielding plate 113 are used at the same time, because it is desirable to shield currency effectively at minute area such as 1-5 mm from edge of the thin plate board W. By using upper board shielding plates 109, current concentration on upper end of the thin plate board W is controlled locally. The upper electrode shielding plate 113 controls currency, that upper board shielding plates 109 couldn't control adequately, not to detour around upper end of the thin plate board W.
Also, as shown in FIG. 18, shielding plate of the thin plate board W's lower end having the lower board shielding plates 108 and the lower electrode shielding plate 112 to prevent from current concentration on the thin plate board W's lower end in this embodiment. The reason using lower board shielding plates 108 and lower electrode shielding plate 112 at the same time is same as the above-mentioned reason of upper board shielding plates 109 and upper electrode shielding plate 113.
The overlap L60 of shielding plates 108, 109, 112, 113 from edge of the thin plate board W (overlapping length between thin plate board W and shielding plate shown in FIG. 21: hereinafter referred to as overlap level) is set the smaller, the closer to the thin plate board W. For instance, lower board shielding plate 108, which is more closer to the thin plate board W, is set overlap level smaller than lower electrode shielding.
It is desirable that distance L50 (FIG. 22) of board shielding plates 108, 109 from the thin plate board W is range 1-50 mm. Therefore, it is possible to prevent from occurring current concentration on the edge of the platy work W effectively without reducing amount of energization required in plating (without reducing plating effectiveness).
Concretely, the upper board shielding plates 109 is overlapped 1-15 mm (10 mm in this embodiment) against upper end of the thin plate board W. The upper electrode shielding plate 113 is overlapped 10-60 mm (50 mm in this embodiment) against upper end of the thin plate board W. Also, the upper board shielding plates 109 (tip of L shaped bottom) is arranged 25 mm distance from the thin plate board W.
On the other hand, the lower board shielding plates 108 is overlapped 1-10 mm (5 mm in this embodiment) against lower end of the thin plate board W. The lower electrode shielding plate 112 is overlapped 50-75 mm (65 mm in this embodiment) against lower end of the thin plate board W. Also, the lower board shielding plates 108 is arranged 4 mm distance from the thin plate board W.
By the way, the effect of shield currency changes, if the setting of overlapping level between board shielding plate and electrode shielding plate has changed. Therefore, as the above-mentioned, lower board shielding plates 108 and lower electrode shielding plate 112 are adjustable of height by height adjuster 220 integrally not to change the overlap level between board shielding plate and electrode shielding plate, even if the size of the thin plate board W has changed.
In FIG. 18, lower board shielding plates 108 is attached on the plate 110, and the plate 110 is connected to the lower electrode shielding plate 112 through support connecting member 216, and lower board shielding plates 108 and lower electrode shielding plate 112 are formed integrally. Furthermore, the support connecting member 216 is also fixed on upper face of the lower board shielding plates 108 for preventing deflection of plate 110.
As shown in FIG. 18, guide table 214 for guiding lower electrode shielding plate 112 is attached on the bottom plate of the treatment tank main body 100 as housing the above eductor box 204 on its downward. Poll 155 is stood upside of guide table 214, and its upper end is bolted on nozzle fixing member 212. The lower electrode shielding plate 112 is bolted (not illustrated) movably up and down through vertical long hole against guide table 214, and rolling mechanism 150 arranged on lower electrode shielding plate 112 fits in pole 155 movably up and down through roller 150 a. In this way, as the lower electrode shielding plate 112 is guided by guide table 214 and poll 155, lower board shielding plates 108 and lower electrode shielding plate 112 and roller stand body 120 are guided integrally when adjusting height by height adjuster 220.
In FIG. 18, height adjuster 220 is comprised of driving motor 220 a, pulley 220 b, connecting wire 220 c, driving belt 220 d, and one end of the connecting wire 220 c is fixed to pulley 220 b and other end is connected to support connecting member. As wire 220 c is rolled up by pulley 220 b based on driving of driving motor 220 a, lower board shielding plates 108 and lower electrode shielding plate 112 and roller stand body 120 are rises integrally.
FIG. 19 shows view of support connecting member 216 from thin plate board W's side. As shown in FIG. 19, connecting wire 220 c is connected on the support connecting member through wire joint 218.
FIG. 20 shows the structure of positive electrode 102. Furthermore, 100 c is a cap for dropping hole 100 b. Positive electrode 102 comprising 301 has an anode case 102 a for housing plating metallic material like copper ball, and grip 102 d is formed on side face of the anode case 102 a, and hook 102 e is formed on lower part of the grip 102 a for attaching anode case 102 a to power supply rail 224 shown in FIG. 1. The upper end of the grip 102 d reaches almost height of opening area 102 b. Also, four guide bars 102 c are attached at even intervals on the opening area 102 b (two bars are impossible to see because of overlapping in the back direction of drawing). The upper end of guide bars 102 c are extended until dropping hole 100 b for dropping metallic material which is formed on the floor 100 a of the treatment tank main body 100.
It is needed to supply the anode case 102 a with metallic material when keeping on plating task. It is prevented that metallic material drops into the treatment tank main body 100 without housing in anode case 102 a for existing of guide bar 102 c when dropping in dropping hole 100 b.
Also, it is needed to maintain by taking up the anode case 102 a when keeping on plating task. By the way, as metallic material is often supplied excessively to avoid lacking of metallic material (dropping metallic material as brimming from dropping hole 100 b), metallic material is prevented from dropping into the treatment tank main body 100 by fitting guide tube in dropping hole 100 b formerly. However, it was difficult to get rid of metallic material supplied excessively when using guide tube, and it takes a lot of trouble to remove the anode case 102 a in maintenance. It becomes easy to remove the anode case 102 a in maintenance, as metallic material supplied excessively from dropping hole 100 b is removed easily by using guide bars 102 c.
2. Board Dipping Device
The plating tank 2 in the embodiment described above has the board dipping device for dipping the thin plate board W at dipping spot 2 a (FIG. 15). Referring to FIG. 13, the structure of board dipping device will be described as follows. Furthermore, FIG. 13A shows cross-section of board dipping device 600 indicating a condition when a board has fallen at (x)-position shown in FIG. 14. FIG. 13B shows plane view of the board dipping device 600 shown in FIG. 13A from upside.
As shown in FIG. 13A, the board dipping device 600 is comprised of treatment tank main body 60 which holds plating liquids for dipping the thin plate board W, board guide 62 for guiding the thin plate board W when falling into the treatment tank main body 60, and air-bubbling tube 68 which is generator of liquid current arranged outside the said board guide 62.
As shown in FIG. 13A, the board guide 62 is comprised of lower guide plate 62 a arranged parallel spacing predetermined distance t, upper guide plate 62 b which is arranged like taper as widening toward upside vertically and having slit 62 c of cutout, and current plate 62 d for preventing liquid current which is occurred by air-bubbling from spreading and weakening. Also, the board guide 62, as shown in FIG. 13A, is arranged as projecting the tip 62 e of upper board guide 62 b from fluid level and dipping the said slit 62 c into plating liquids. FIG. 7 shows perspective view of board guide 62.
The air-bubbling tube 68, which is generator of liquid current, discharges air upward based on air supply though pipe 66 shown in FIG. 13A. Therefore, upward flow occurs as circumjacent plating liquids of uprising air uprises and the plating liquids sectioned by current plate 62 d flows from downside of current plate 62 d. Further, the uprisen plating liquids run through slit 62 c, and forms down flow between lower guide plates 62 a. Thus, it becomes possible to guide and dip the thin plate board W along the board guide 62 smoothly. Further, as an experimental result, it was more effective to guide smoothly when arranging air-bubbling tube 68 at middle depth area in the treatment tank main body 60 than arranging at same height as slit 62 c or at lower area of current plate 62 d. Also, as an experimental result, it was more effective to guide the thin plate board W smoothly when forming slit 62 c on upper guide 62 b than forming it on lower guide 62 a.
The structure as the above-mentioned makes it easy to guide the thin plate board W smoothly because of generated liquid flow by generator arranged outside the board guide 62, as the board guide 62 is projecting the tip 62 e of upper board guide 62 b from fluid level and dipping the said slit 62 c into plating liquids.
Further, as shown in FIG. 13, the board dipping device is placed at dipping spot of board in the plating tank 2, and the air-bubbling tube 68 is used as a generator of liquid current. However, it is possible to use jet nozzle 64 as a generator of liquid current as shown in FIG. 6A when it is desirable to enhance treatment effectiveness on though-hole of the thin plate board W and inside via hole, and when an acid-wash clean treatment is performed in pre-treatment tank 1 where bubbling should be avoided. In this case, jet flow is discharged nearly in a horizontal direction toward slit 62 c from jet nozzle 64. Therefore, it becomes possible to guide and dip the thin plate board W along the board guide 62 smoothly, as flow is generated which passes through slit 62 c and directs downward between lower guides 62 b.
As an experimental result, it was more effective to guide the thin plate board W smoothly when discharging a jet flow toward upper part R of slit as shown in FIG. 8 than discharging directly toward the slit. In FIG. 8, the jet flow is discharged upwardly to the level plane.
As shown in FIG. 6B, jet nozzle 64 is arranged at even intervals in a transporting direction of the transport hanger 15 (E-direction). As shown in FIG. 6A, it is arranged fixedly at same height as cutout 62 c of the board guide 62.
Also, on the fluid level, it is possible to blow off by setting an air blower arranged outside the board guide 62, before discharged air through air-bubbling tube 68 forms bubbles on the fluid level. It is realized by arranging the air blower as its air discharge direction faces in a direction opposite to board guide. Therefore, it becomes possible to achieve a enough effect based on treatment liquids by preventing the thin plate board W from acquiring bubbles on the surface.
Although, it is applied to plating tank in the embodiment described above, it is possible to apply to the other treatment tank like washing.
3. The Structure of the Surface Treatment Device and the Transport Hanger
As shown in FIG. 14 and FIG. 15, the surface treatment device 300 is the surface treatment device of so-called pusher type, and having guide rails 10-13 for transporting the transport hanger 15 which is holding the platy work such as a printed board, and arranged such that along these guide rails 10-13, the pre-treatment tank 1 of each type for processing before plating, plating tank 2 for electroplating, recovery tank 3 and water-washing tank 4 for processing after plating, unload section 5 for unloading the platy work, exfoliate tank 6 for separating plating films (hanger restoring process), water-washing tank 7 for water-washing the transport hanger 15 after separating, and load section 8 for loading a board.
Rise-and- fall guide rails 10, 12 shown in FIG. 15 are guide rails which rise and fall when loading or unloading the board W (such as printed board), and when dipping the board W into various type of tanks (e.g., plating tank 2, recovery tank 3 and water-washing tank 4, etc.). Fixed guide rails 11, 13 are guide rails fixed respectively for transporting the transport hanger 15 which has fallen into plating tank 2, exfoliate tank 6.
Referring to FIG. 9, the structure of the transport hanger 15 will be described.
As shown in FIG. 9, the transport hanger 15 has treating-object holding member 47 with plural clamps 48 for holding the treating-object W, slide member 35 which contact slidably with guide rails such as fixed guide rail 11, and connecting members 44 for connecting such members. Copper and brass are used for the material of the slide member 35 and connecting members 44.
The width L0 of treating-object holding member 47 is calculated based on the width W0 of platy work W and clamping margin W1. For example, if clamping margin W1 exists on both sides of platy work W (width W0) as shown in FIG. 9, the width L0 of treating-object holding member 47 is calculated by formula: L0=W0−2×W1.
As shown in FIG. 10, a bearing 36 which has the gear 40 adjusting together with chain belt 39 (comprising the fixed guide rail transporter 19 in FIG. 7) of one-way clutch type is fixed on the slide member 35. Therefore, the gear 40 which adjusts together with chain belt 39 on the fixed guide rail 11, 13 can rotate only in B-direction shown in FIG. 9 when feeding forward.
The pusher contacting face 37 shown in FIG. 9 is a part contacted by the pusher 16, 21 (FIG. 11) of intermittent transporter 17, 22 which is transport means of the transport hanger 15
The nail-hooking part 32 of FIG. 10 is a part contacted by the transport nail 30 (FIG. 12) of positioning transporter 18 for transporting the transport hanger 15. These transporters of the transport hanger 15 will be described as follows.
4. Each Transporter for the Transport Hanger
The transport hanger 15 shown in FIG. 9 is transferred by intermittent transporter 17, 22, positioning transporter 18, 23, fixed guide rail transporter 19, 24, and letting-off transporter 20, 25 in the surface treatment device 300 as follows.
First, intermittent transporter 17, 22 which is attached on top of the rise-and- fall guide rails 10, 12 transport the transport hanger 15 pitch by pitch that is respectively placed at (c)-(f),(h)-(k) intermittently by using the pusher 16 a-d, 21 a-d (FIG. 11). FIG. 11 shows plane view of intermittent transporter 17 on the rise-and-fall guide rail 10.
The positioning transporter 18 shown in FIG. 15 is arranged along the fixed guide rail 11. And the transport hanger 15 (FIG. 15), which has fallen into dipping spot 2 a (board dipping position) at (x)-position where is upside of the plating tank 2, is transferred to the fixed guide rail 11 and fed forward until (b)-position. And, the distance between platy work W (thin plate board W) and the fore one placed at (a)-position (left side in FIG. 15) in the plating tank 2 is adjusted to predetermined width L1 (e.g. L1=5 mm).
FIG. 12 shows the structure of positioning transporter 18. The positioning transporter 18 shown in FIG. 12 is movable back and forth in X, Y-direction along rail which is arranged separately from the fixed guide rail 11, and having a transport nail 30 biased in Z-direction by spring in the condition shown FIG. 12A. Therefore, when transporting the transport hanger 15, firstly pass through the nail-hooking part shown in FIG. 10 by shrinking the spring (condition shown in FIG. 12B). After that, the transport hanger 15 is transferred to C-direction shown in FIG. 14, as the positioning transporter 18 moves in the opposite direction (Y-direction of FIG. 12C) and the transport nail 30 hooks the nail-hooking part 32 of transport hanger 15. At this time, the moving speed of the positioning transporter 18 is needed to be faster than moving speed of the fixed guide rail transporter 19 (i.e. the moving speed of the chain belt 39) as to catch up a foregoing transport hanger 15 that the fixed guide rail transporter 19 is transporting. Also, the structure and the movement of positioning transporter 23 of exfoliate tank 6's side are same as positioning transporter 18 of plating tank 2's side shown in FIG. 12.
The fixed guide rail transporter 19, 24 transports the transport hanger 15 to C-direction of FIG. 14 which is fed forward by the positioning transporter 18, 23, with keeping predetermined distance (L1 of FIG. 15).
The letting-off transporters 20, 25 transfer the transport hanger 15, which is transported by the fixed guide rail transporter 19, 24 until (g), (o), to (h), (f) position of the rise-and- fall guide rails 10, 12 respectively (FIG. 14). Also, the structure and the movement of letting-off transporter 20, 25 are same as positioning transporter 18 shown in FIG. 12.
5. The Other Embodiment
Also, in the embodiment described above, although the upper (lower) board shielding plate and the upper (lower) electrode shielding plate are used as two shielding plates against the thin plate board W, it is possible to add a further shielding plate between board shielding plate and electrode shielding plate.
Also, in the embodiment described above, although the upper board shielding plate and the upper electrode shielding plate move up and down independently, it is possible to let them move up and down integrally.

Claims

1. A plating tank for electroplating a platy work, comprising:

a treatment tank main body for holding treatment liquids which is arranged as extending in transporting direction of the platy work;

a positive electrode;

a spouter for spouting the treatment liquids to the said platy work from lateral side of the treatment tank main body;

a restrict roller having a plural of rollers, wherein the rollers are attached rotatably from upper part until lower part of the treatment tank main body and arranged consecutively in transporting direction of the platy work as sandwiching both sides of the platy work on moving inside the treatment tank main body;

a current shield for preventing from occurring current concentration on the end of the platy work.

2. The plating tank according to claim 1, wherein the said restrict roller is comprised of a plural of roller stand bodies which are having plural rollers vertically, and arranged in transporting direction of the said plating work, and interval on the spouting position of the spouter between adjacent roller stand bodies are wider than the other intervals.

3. The plating tank according to claim 1, wherein a deviation preventing member is placed at lower end area of the platy work where the spouting position of the spouter is placed as sandwiching both sides of the platy work on moving.

4. The plating tank according to claim 1, wherein the rollers are arranged at least one per predetermined unit area in a region that the restrict rollers are arranged.

5. The plating tank according to claim 1, wherein the said restrict roller is comprised of a plural of roller stand bodies which are having plural rollers vertically, and arranged in transporting direction of the said plating work, and vertical intervals that the rollers of the restrict roller is arranged are range from 50 mm to 100 mm.

6. The plating tank according to claim 1, wherein the said restrict roller is comprised of a plural of roller stand bodies which are having plural rollers vertically, and arranged in transporting direction of the said plating work, and the rollers placed over predetermined height differs the vertical position mutually between the roller stand bodies.

7. The plating tank according to claim 1, wherein the said current shield is comprised of a upper shielding plate for preventing from occurring current concentration on the upper end of the platy work and/or a lower shielding plate for preventing from occurring current concentration on the lower end of the platy work.

8. The plating tank according to claim 7, wherein the said upper shielding plate and/or the lower shielding plate are comprised of plural shielding plates arranged between the said platy work and the said positive electrode, and its overlap with the platy work is the smaller, the closer to the platy work.

9. The plating tank according to claim 8, wherein the said plurality of shielding plates are formed in a unified manner and able to rise and fall.