Abstract:
A partial plating device includes a drum jig which has a plurality of positioning pins provided on the outer peripheral surface thereof, and which feeds a metal member around the outer periphery thereof by engaging the metal member with the positioning pins; a rotating shaft which rotatably supports the drum jig, a jet unit that supplies plating liquid to the metal member, and a brake unit that reduces the circumferential speed of the drum jig, and which is fitted to the rotating shaft. A plating device and a partial plating method in which plating is not carried out on the first region of a metal member on the carrying-in side of the drum jig, but in which plating is carried out on the second region of a metal member on the carrying-out side.

Description:
This application claims priority from Japanese Patent Application Numbers JP2011-229476 (filed on Oct. 19, 2011) and JP2012-068705 (filed on Mar. 26, 2012), the content of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a partial plating apparatus being configured to partially plate a metal member made of copper (Cu), a Cu alloy, iron (Fe), an Fe alloy, or the like, and capable of reducing variations in the thickness of plated films. 
     BACKGROUND ART 
     A partial plating apparatus using a cylindrical jig (drum jig) is known as a partial plating apparatus for partially plating an elongated metal member.  FIG. 10  is a top view schematically showing a drum jig  201  of a conventional partial plating apparatus  200 . 
     The plating apparatus  200  with the drum jig is an apparatus configured to perform plating by a continuous feed method. Specifically, an elongated metal member  202  which is to be plated is wound around an outer circumferential surface of the drum jig  201 . Then, while the metal member  202  is moving, a plating solution is supplied from about the center of the drum jig  201  to the surface of the metal member  202 , as indicated by the broken-line arrows, through opening portions (not shown) provided in the outer circumferential surface of the drum jig. Since portions other than the opening portions are masked by the drum jig, the plating material is not deposited on those other portions. Thereby, the metal member can be partially plated. Such a plating method is called spot plating. 
     In such a partial plating apparatus, multiple positioning pins  203  are provided on the outer circumferential surface of the drum jig  201 . By causing these positioning pins  203  to engage with guide holes (not shown) provided in the metal member  202  and moving the metal member  202  at a predetermined velocity, the drum jig  201  rotates. Although seven positioning pins  203  are shown to provide an overview, eight or more positioning pins  203 , for example, are actually provided (the same is true hereinbelow). 
     The drum jig  201  is supported by a rotary shaft  204  while being able to rotate around the rotary shaft  204 , and unless an external force for driving the drum jig  201  is applied thereto, the drum jig  201  rotates at the same circumferential velocity as the moving velocity of the metal member  202 , as indicated by the thin-line arrows. 
     There is also known a partial plating apparatus configured to press an inner circumferential surface of a drum jig rotating along with the movement of a metal member and to change the circumferential velocity of the drum jig by adjusting this pressing force (refer to, for example, patent document 1). 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Patent Application Publication No. 2009-242859 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     Plating processing performed with the conventional partial plating apparatus shown in  FIG. 10  causes a problem where there are noticeable variations in the distribution of the plated-film thickness on a plated product. 
       FIG. 11  shows diagrams illustrating a relation between the drum jig  201  of the partial plating apparatus  200  and the metal member  202  in  FIG. 10 . Specifically,  FIGS. 11A and 11B  are top views,  FIG. 11C  is a spread-out top view of  FIG. 11B , and  FIG. 11D  is an enlarged diagram of a portion in  FIG. 11C  circled by a broken line. 
     First,  FIGS. 11A and 11B  are diagrams illustrating positional relations between the positioning pins  203  of the drum jig  201  and the guide holes of the metal member  202  engaging therewith respectively. The metal member  202  is an elongated member whose length is, for example, ten times or more larger than its width. In  FIGS. 11A and 11B , the width of the metal member  202  is along a depth direction, and the length thereof is along a left-right direction. Here,  FIGS. 11A and 11B  show the guide holes h 1  to h 10  in a plan view so that their shapes can be seen (viewed on a main surface of the metal member  202 ), and show positions of engagement between the positioning pins and the corresponding guide holes h 1  to h 10 . Note that the guide holes h 1  to h 10  are collectively referred to as guide holes h hereinbelow when they do not need to be discriminated from one another. 
     The metal member  202  is a thin plate which is elongated as described above and has a thickness of, for example, no more than about 0.8 mm. The drum jig  201  and the metal member  202  are designed so that a spacing distance (pitch) p1′ between every adjacent ones of the positioning pins  203  may coincide with a spacing distance (pitch) p2′ between every adjacent ones of the guide holes h of the metal member  202 . However, a certain clearance is necessary between the guide hole h and the positioning pin  203 , and also considering that the drum jig  201  is cylindrical, it is practically impossible, in view of processing accuracy, to make the positioning pins  203  and the guide holes h completely coincide with each other. 
     To be more specific, the difference per pitch between the pitch p1′ of the positioning pins  203  and the pitch p2′ of the guide holes h which is allowed to make them completely coincide with each other (called a pitch difference between the guide hole and the positioning pin) is equal to or beyond the processing-accuracy limit for the drum jig  201 . Hence, the jig cannot be manufactured within this pitch difference. In addition, since the drum jig  201  expands during plating processing due to the temperature of a plating solution, this factor needs to be considered at the design phase. This makes it even more impossible to keep the pitch difference within the allowable range. 
     For example, since the drum jig  201  is designed to aim the pitch p1′=the pitch p2′ and manufactured with a±tolerance, the pitch relation may result in the pitch p1′&lt;the pitch p2′ or the pitch p1′&gt;the pitch p2′. 
     For these reasons, there occurs a pitch difference between the guide holes and the positioning pins. Repetition of accumulation and cancellation of this pitch difference during a manufacture process leads to a problem of variations in the distribution of the plated-film thickness. 
     Referring to  FIG. 11A , the metal member  202  is moving from an entry point I side to an exit point O side, as indicated by the arrows. With a distance between the head of the metal member  202  to be plated and the exit point O being L1, if the pitch p1′ of the positioning pins  203  of the drum jig  201  is slightly smaller than the pitch p2′ of the guide holes h of the metal member  202  (if p1′&lt;p2′ as a result), the positioning pins  203  engage with the respective guide holes h 1  to h 7  of the metal member  202 , as shown in  FIG. 11A . 
     From the exit point O side of the drum jig  201  to the entry point I side of the drum jig  201 , the engagement positions of the positioning pins  203  in the guide holes h of the metal member  202  are shifted more and more forward in the travelling direction (toward the exit point O for the metal member  202 ), each by the amount of the pitch difference. Meanwhile, as the metal member  202  moves from the entry point I side to the exit point O side as indicated by the arrows, the drum jig  201  rotates about the rotary shaft  204  due to a frictional force acting between the drum jig  201  and the metal member  202 . In other words, in this case, the drum jig  201  rotates in the moving direction of the metal member  202  at a circumferential velocity v1′ which is equivalent to a moving velocity v2′ of the metal member  202 . 
     Referring to  FIG. 11B , as the metal member  202  further moves on making the distance between the head of the metal member  202  and the exit point O L2 (L1&lt;L2), the guide hole h 4 , for example, of the metal member  202  engages with the endmost positioning pin  203  at the exit point O side, and the guide holes h 8  to h 10  newly engage with their corresponding positioning pins  203 . 
     As shown in  FIG. 11B , even after the guide holes h 1  to h 3  separate from the drum jig  201 , the drum jig  201  keeps rotating due to the frictional force acting between itself and the metal member  202  and therefore rotates at the same circumferential velocity v1′ as the moving velocity v2′ of the metal member  202 . Thus, the positional relations between the positioning pins and the guide holes shown in  FIG. 11A  are maintained. Then, at the guide hole h 8 , the pitch differences from the guide hole h 4  to the guide hole h 8  are accumulated (this is called an accumulated pitch difference hereinbelow). 
     Thus, as shown in  FIGS. 11C and 11D , at the guide hole h 8  for example, the positioning pin  203  comes into contact with an end portion of the guide hole h 8  by exceeding the clearance between the guide hole h 8  and the positioning pin  203 . As a result, the metal member  202  slightly separates from the drum jig  201  (see  FIG. 11D ). 
     In other words, when the guide hole h and the positioning pin  203  come into contact with each other due to the accumulation pitch difference therebetween, separating the metal member  202  from the drum jig  201 , the distribution of the plated-film thickness is locally low. Then, there occurs a problem where, when the accumulation and cancellation of the pitch difference are repeated, a single metal member has large variations in its plated-film thickness. 
     This also depends on the area of each plated portion (spot). Specifically, even when the partial plating apparatus shown in  FIG. 10 , i.e., the continuous-feed partial plating apparatus is used for plating, the variations in the plated-film thickness are not problematic if the area of each plated portion is rather large. 
     In recent years, however, with a size reduction in various electronic devices and their components, the area of each plated portion (spot) of a plated product is reduced more and more (e.g., 5 mm×5 mm or less). With this, the problem of the variations in the plated-film thickness is more noticeable than before. 
     To overcome this problem, it is conceivable to cancel out the pitch difference between the guide hole h of the metal member  202  and the positioning pin  203  of the drum jig  201 . 
     For example, Patent Document 1 discloses a technique for pressing a rubber roller against a drum jig (cylindrical drum) and adjusting this pressing force to adjust the circumferential velocity of the drum jig. 
     However, it is extremely difficult to control the moving velocity of the metal member and the circumferential velocity of the drum jig independently. 
     Specifically, in the technique described in Patent Document 1, the rubber roller is pressed against the drum jig which is being rotated at a constant velocity by a motor, and the circumferential velocity of the drum is controlled by controlling the strength of the pressing force. 
     Assume, for example as general numerical values, that the length of the metal member  202  is 2000 m, the clearance between the guide hole h and the positioning pin  203  is 0.5 mm, and the moving velocity of the metal member is 2 m/min. Then, an allowable error in the circumferential velocity of the drum jig  201  is 0.5 μm/min. 
     Thus, the circumferential velocity of the drum jig being rotated by the motor needs to be independently controlled so that the error will not exceed the above range, and to do this, for example, means for monitoring the clearance and feeding back or the like is necessary. Specifically, Patent Document 1 controls the circumferential velocity by monitoring the clearance by use of a laser, image processing, or the like so that the error will not exceed the allowable range and feeding back the monitor result. 
     However, a structure needing such feedback means has problems such as involving complicated control and increasing equipment costs. 
     Mean for Solving the Problems 
     The present invention has been made in view of the above problems which are to be solved by, firstly, providing a partial plating apparatus including: a drum jig having a plurality of positioning pins arranged on an outer circumferential portion thereof so that a metal member engages with the positioning pins to be transported along the outer circumferential portion; a rotary shaft configured to support the drum jig such that the drum jig is rotatable; a jet portion configured to supply a plating solution to the metal member; and a brake unit attached to the rotary shaft and configured to reduce a circumferential velocity of the drum jig. 
     In this way, the present invention manufactures the drum jig such that the pitch of the positioning pins may be slightly smaller than the pitch of the guide holes, provides the rotary shaft supporting the drum jig with the brake unit configured to slow down the drum jig, and thereby cancels out the accumulation pitch difference between the guide hole of the metal member and the positioning pin of the drum jig. The brake unit causes the drum jig to move (slide) in an opposite direction relative to the metal member within the clearance between the guide hole and the positioning pin, and thereby the accumulated pitch difference is cancelled. 
     Secondly, the above problems are solved by providing a partial plating method for performing partial plating on a metal member transported along an outer circumferential portion of a drum jig of a partial plating apparatus. In this method, part of the outer circumferential portion of the drum jig is a contact region where the drum jig is in contact with the metal member and which has a first region and a second region, the first region extending over a predetermined distance from an end portion of the contact region on a side where the metal member enters, the second region extending from an end portion of the first region to an end portion of the contact region on a side where the metal member exits, the metal member is not plated in the first region, and the metal member is plated in the second region. 
     In this way, the present invention reduces variations in the thickness of plated films by performing plating only in the second half of the contact region. 
     Advantageous Effects of Invention 
     According to the partial plating apparatus of the present invention, firstly, is provided a continuous-feed partial plating apparatus using a drum jig capable of reducing variations in the distribution of the film thicknesses on a plated product. 
     In the partial plating apparatus, the brake unit is provided at the rotary shaft supporting the drum jig such that the drum jig is rotatable, and applies a load to the rotary shaft to make the circumferential velocity of the drum jig lower than the moving velocity of the metal member. Thereby, the accumulated pitch difference between the guide hole of the metal member and the positioning pin of the drum jig which is created during the plating processing is continually cancelled, reducing variations in the thickness of the plated films. 
     The load applied by the brake unit to the rotary shaft is maintained to be larger than a force with which the drum jig moves (slides) in a direction opposite from the travelling direction of the metal member with which the drum jig is in contact, but not larger than a force causing deformation of the metal member. 
     Thereby, the accumulated pitch difference between the guide hole and the positioning pin created while one elongated metal member is processed is continually cancelled (not accumulated), allowing every positioning pin to be within the clearance between the positioning pin and its corresponding guide hole. 
     The drum jig of the embodiments herein is configured not to control its own rotation, but to rotate along with the movement of the metal member, and is slowed down by the brake unit. In other words, without additional feedback means or clearance monitoring means, engagement between the guide hole and the positioning pin can be ensured over the entire metal member only by maintaining the load applied by the brake unit to the rotary shaft to be within a predetermined range. Thus, the circumferential velocity of the drum jig does not need to be controlled, and the equipment is simple and requires low costs. 
     Further, the pitch of the positioning pins of the drum jig is designed to be smaller than the pitch of the guide holes of the metal member, and the brake unit reduces the circumferential velocity of the drum jig relative to the moving velocity of the metal member during the plating processing. Thereby, when the metal member enters the drum jig, the position pin is located forward (toward the exit side), in the travelling direction, of the center of the corresponding guide hole, and when metal member exits the drum jig, the positioning pin is located rearward (toward the entry side) of the center of the guide hole. Thus, biting at the entry and the exit can be reduced. 
     Secondly, at the contact region where the drum jig and the metal member are in contact with each other, the metal member is not plated in the first region on the metal-member entry side, and the metal member is plated in the second region on the metal-member exit side. With such a structure, the distribution of the film thickness can be evened out furthermore. 
     Since reduction in film thickness occurs noticeably in the first half of the contact region, the plating processing is performed not in this first half, but only in the second half extending from the middle area (second region). Thus, counter electrodes (anodes) are provided only in the second region, or a jet portion configured to eject a plating solution only to the second region is employed. Thereby, the film-thickness distribution can be evened out furthermore. 
     Thirdly, according to the partial plating method of the present invention, the metal member is plated not in the first half (the first region) of the drum jig, but only in the second region. For this reason, variations in the distribution of the plated-film thickness can be reduced, compared to a plating method which performs plating on the entire contact region. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a top view illustrating a partial plating apparatus according to a first embodiment of the present invention, and  FIG. 1B  is a sectional view thereof. 
         FIG. 2A  is a top view illustrating the partial plating apparatus according to the first embodiment of the present invention,  FIG. 2B  is a side view thereof, and  FIG. 2C  is a sectional view thereof. 
         FIG. 3A  is a top view illustrating the partial plating apparatus according to the first embodiment of the present invention,  FIG. 3B  is a spread-out top view thereof,  FIG. 3C  is an enlarged top view thereof, and  3 D is an enlarged top view thereof. 
         FIG. 4A  is a characteristics chart showing a comparison between plated-film thickness variations of the partial plating apparatus according to the first embodiment of the present invention and plated-film thickness variations of a partial plating apparatus having a conventional structure, and  FIG. 4B  is a comparison table therefor. 
         FIG. 5A  is a top view of a partial plating apparatus according to a second embodiment of the present invention, and  FIG. 5B  is a schematic top view showing how a metal member is transported by a drum jig. 
         FIG. 6  is a perspective view illustrating the partial plating apparatus according to the second embodiment of the present invention. 
         FIG. 7A  is a top view illustrating the partial plating apparatus of the first embodiment of the present invention,  FIG. 7B  is a spread-out top view thereof, and  FIG. 7C  is a top view illustrating the partial plating apparatus according to the second embodiment of the present invention. 
         FIG. 8A  is a characteristics chart showing a comparison between plated-film thickness variations of the partial plating apparatus according to the second embodiment of the present invention and plated-film thickness variations of the partial plating apparatus according to the first embodiment, and  FIG. 8B  is a comparison table thereof. 
         FIG. 9  is a top view illustrating a partial plating apparatus according to a third embodiment of the present invention. 
         FIG. 10  is a top view illustrating the conventional structure. 
         FIG. 11A  is a top view illustrating the conventional structure,  FIG. 11B  is a top view thereof,  FIG. 11C  is a spread-out top view thereof, and  FIG. 11D  is an enlarged top view thereof. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention are described with reference to  FIGS. 1 to 9 . First, a first embodiment of the present invention is described with reference to  FIGS. 1 to 4 . 
       FIG. 1  shows schematic diagrams illustrating the structure of a partial plating apparatus  10  of the first embodiment. Specifically,  FIG. 1A  is a top view thereof also showing its underlayer (internal) structure transparently, and  FIG. 1B  is a sectional view taken along line a-a in FIG. A. 
     Referring to  FIG. 1 , the partial plating apparatus  10  has a drum jig  1 , a rotary shaft  2 , a jet portion  8 , and a brake unit  15 . 
     The drum jig  1  is a jig configured to bring a metal member (not shown here) being a member to be plated, into a close contact with an outer circumferential portion thereof and transport the metal member along with the outer circumferential portion. The drum jig  1  is rotatable about the rotary shaft  2 , but there is no driving means for rotating the drum jig  1 . In other words, when the metal member moves at a predetermined velocity, the drum jig  1  rotates at a predetermined circumferential velocity v1 in the same direction as the metal member travels, e.g., the arrowed direction in  FIG. 1A . For example, a drum diameter φ of the drum jig  1  is preferably 200 mm to 500 mm. When the drum diameter φ is smaller than 200 mm, productivity might be lowered since it is hard to wind the metal member (although it depends on the thickness of the metal member), or the plating time is shortened to decrease a so-called line speed. When the drum diameter φ is larger than 500 mm, problems such as the following arise: difficulty of manufacturing (processing) the partial plating apparatus, larger influence by the eccentricity of the drum jig  1 , and increase in initial costs. On the outer circumferential portion of the drum jig  1 , multiple positioning pins (not shown here) are arranged such that they are spaced away from each other at equal distances (pitch). 
     The rotary shaft  2  is supported by a support column  7  and thereby fixed to a base plate  21 . One end of the rotary shaft  2  (the upper end in  FIG. 1B ) is fixed to the drum jig  1  which is thereby rotatably supported. The other end (the lower end in  FIG. 1B ) is attached to the brake unit  15 . 
     The brake unit  15  is attached to a lower end portion of the rotary shaft  2  which is located below the base plate  21 , and applies a predetermined load to the drum jig  1 . Thereby, the circumferential velocity v1 of the drum jig  1  being plated is reduced to be lower than the moving velocity of the metal member. 
     The brake unit  15  applies the load by pressing the rotary shaft  2  from its outer side (outer circumference), and employs a braking method capable of linearly controlling a pressure parameter in a low-load region. The pressure parameter is, for example, air pressure. 
     More specifically, the brake unit  15  employs a disk brake method which puts a brake by using an air pressure. The load is controlled with the air pressure maintained constant by, for example, a compressor and a regulator, and the load is maintained almost constant while a single metal member is being plated. 
     An appropriate value is selected for the load by changing an air pressure to be fed into the brake unit  15 , according to the material, plate thickness, and width of the metal member, the tension of the metal member (a pulling force exerted on the metal member in the plating processing line), the drum diameter φ and weight of the drum jig  1 , an angle at which the metal member is wound around the drum jig  1 , and the like. 
     For example, a small load is set when the metal member has a small plate thickness or is made of a material which easily causes deformation of the guide holes h. Further, a large load is set in cases such as where the metal member is made of a material causing a large frictional force to act between the metal member and the drum jig  1  (hard to slip) or has a large tension so that a large frictional force acts between the metal member and the drum jig  1 . 
     Note that the brake method of the brake unit  15  is not limited to this example as long as it is a method capable of linearly controlling the pressure parameter in the low-load region. 
     The jet portion  8  supplies a plating solution (indicated by hatching) to the metal member via the drum jig  1 . The plating solution is accommodated in a supply tank (not shown) outside a process tank  23 , and drawn from the supply tank with a pump or the like (not shown) to the jet portion  8  through piping  25 , as indicated by the upward arrow. The plating-solution supply tank is provided with a heater, a temperature sensor, an adjustor, and the like to keep the temperature of the plating solution to be constant. Further, the pump includes an inverter for controlling the flow rate, and controls the flow rate. The jet portion  8  collects the plating solution ejected to the metal member into the supply tank through the piping  25 , as indicated by the downward arrow. 
     A liquid protection dam  24  is provided around an outer circumference of the jet portion  8 , and the drum jig  1  is placed on an upper portion of an inner circumferential portion of the liquid protection dam  24  and covers the jet portion  8 . Support rollers  4  support movement of the metal member wound around the drum jig  1 . 
     Counter electrodes (anodes)  9  are provided at a plating-solution ejection vent of the jet portion  8 . The jet portion  8  has, for example, a substantially semi-circular shape in the plan view of  FIG. 1A , and the anodes  9 , too, have a substantially semi-circular shape along the shape of the jet portion  8 . 
     The drum jig  1  is further described with reference to  FIG. 2 .  FIG. 2A  is a schematic top view showing a state where a metal member  11  is wound around the drum jig  1  shown in  FIG. 1A ,  FIG. 2B  is a side view showing the state from an S-direction point of view in  FIG. 2A , and  FIG. 2C  is a diagram showing part of a section taken along line b-b in  FIG. 2A . 
     Multiple positioning pins  6  are arranged on the outer circumferential portion of the drum jig  1  at equal spacing distances (pitch p1). Although only seven positioning pins  6  are arranged herein to give an overview, eight or more positioning pins  6 , for example, are actually arranged on the outer circumferential portion of the drum jig  1 . 
     The metal member  11  engages with the positioning pins  6  and is thereby transported along the outer circumferential portion of the drum jig  1  from an entry point I to an exit point O as indicated by the arrows. The drum jig  1  of this embodiment rotates along with the movement of the metal member  11 . 
     As indicated by the broken-line arrows, a plating solution is supplied to the metal member  11  from the jet portion  8  provided inside the drum jig  1 . 
     Referring to  FIG. 2B , the positioning pins  6  are provided on the outer circumferential surface of the drum jig  1 . The multiple positioning pins  6  are arranged in the circumferential direction. The metal member  11  is also provided with multiple guide holes h which correspond to the positioning pins  6 . The guide holes h are spaced away from one another at equal spacing distances (pitch p2). 
     The guide holes h of the metal member  11  engage with the positioning pins  6 , and the metal member  11  is pulled in the arrowed direction. Thereby, the metal member  11  is brought into a close contact with part of the outer circumferential portion of the drum jig  1 , and a frictional force acting therebetween causes the drum jig  1  to rotate. 
     In this embodiment, the metal member  11  is transported along the outer circumferential portion of the drum jig  1  with its width W direction (Y direction in  FIG. 2B ) being vertical. The width W direction is a direction orthogonal to a long-side direction (X direction) of the elongated metal member  11 . 
     The rotation of the drum jig  1  is not controlled by any driving means such as a motor. Instead, when the metal member  11  moves, the drum jig  1  rotates in the travelling direction of the metal member  11  (in the same direction as far as a surface thereof in contact with the metal member  11  is concerned). However, the average circumferential velocity v1 of the drum jig  1  is reduced by the brake unit  15  to be lower than the moving velocity v2 of the metal member (see  FIG. 1A ). To be more specific, the brake unit  15  gives the rotary shaft  2  a load which is larger than a force with which the metal member  11  and the drum jig  1  in contact with each other move (slide) in opposite directions, but not larger than a force causing deformation of the metal member  11 . 
     In this way, the drum jig  1  which rotates at the circumferential velocity equivalent to the moving velocity of the metal member  11  when no load is applied thereto can be slowed down. By setting a lower limit of the load of the brake unit  15  within the above range, the drum jig  1  rotates slightly more slowly than the metal member  11  and slides on the metal member  11 , and thus the metal member  11  and the drum jig  1  move in relatively opposite directions (i.e., they slide on each other). 
     As an example, when the metal member  11  which is made of a Cu (copper) alloy and is 0.2 mm thick and 30 mm wide is moved under a tension of 4 kgf, a load to be given by the brake unit  15  is set to about 4 kgf. In this case, supposing that the pitch p2 of the guide holes h is 10 mm/pitch and a pitch difference between one guide hole h and a corresponding positioning pin  6  is, for example, 0.003 mm, the average velocity v1 of the drum jig  1  is reduced by 0.03% relative to the moving velocity v2 of the metal member  11 . 
     On the outer circumferential portion of the drum jig  1 , multiple opening portions  3  are arranged along the circumferential direction of the column. A material for the drum jig  1  is a resin with low thermal expansion, and is, for example, a heat-resistant vinyl chloride resin, a polyphenylene sulfide (PPS) resin, a polyetheretherketone (PEEK) resin, or the like. 
     Referring to  FIG. 2C , the plating solution is supplied to the metal member  11  from the ejection vent (slit portion  8 S) of the jet portion  8 , as indicated by the broken-line arrow, through the opening portions  3  provided in the drum jig  1 . The counter electrodes (anodes)  9  are provided inside the drum jig  1  to face the metal member  11 . For example, the counter electrodes  9  are provided at an upper portion and a lower portion of the slit portion  8 S, respectively. A voltage is applied between the metal member  11  and the counter electrodes  9  to produce currents via the plating solution. 
     By passing currents through the plating solution, plated films  12  are formed on the metal member  11 . More specifically, the plated films  12  each having the shape of the opening portion  3  are formed by spot plating on the metal member  11  in such a manner as to form a line, for example, in the long-side direction of the metal member  11 . The plated film  12  is, for example, a gold (Au) plated film whose four sides are each, for example, 5 mm or less long. Prior to the spot plating of Au, base plating of nickel (Ni), an Ni alloy, Cu, a Cu alloy, or the like may be performed on the metal member  11  (see  FIG. 2B ). 
     In this embodiment, the drum jig  1  and a mask for forming the plated films are integrated with each other. To be more specific, when a plating solution is ejected from the jet portion  8  to the metal member  11  as indicated by the arrow through the opening portions, the area excluding the opening portions  3  is covered by the drum jig  1 , and portions of the drum jig  1  around the opening portions  3  act as a mask for forming the plated films. 
     Note that the present invention is not limited to this, and may be configured such that a resin mask member having the opening portions  3  is wound around the outer circumferential portion of the drum jig  1 . In this case, the drum jig  1  has a structure such as the following. Specifically, the drum jig  1  is provided with a slit running along the circumference of the outer circumferential portion thereof, for example, so that the plating solution can be supplied from the jet portion  8 , and the mask member is provided on the outer circumferential portion such that the opening portions  3  thereof coincide with the slit. 
     In contrast to this structure, the drum jig  1  in this embodiment serves also as a mask. Thus, mask misalignment can be prevented. 
     Next, with reference to  FIG. 3 , a description is given of a relation that the metal member  11  and the drum jig  1  have to each other while the partial plating apparatus  10  is performing its plating processing. 
       FIGS. 3A and 3B  are diagrams illustrating a positional relation between each positioning pin  6  of the drum jig  1  and the guide hole h of the metal member  11  engaging with this positioning pin  6 . The guide holes h in  FIG. 3A  are depicted as described earlier. Specifically, the guide holes h (h 4  to h 10  here) are actually provided to penetrate through two main surfaces (front and back surfaces) of the metal member  11 , each main surface being formed by sides extending in the width W direction and sides extending in the length L direction. However, the guide holes h 4  to h 10  are shown here in a plan view (as in  FIG. 3B ) so that their shapes and the positions of engagement between them and the corresponding positioning pins can be seen. Further,  FIG. 3A  also provides a plan view (plan view seen from the main surface side of the metal member  11 ) for each of the guide holes h 4  and h 10  to show the clearance between the guide hole h and the positioning pin  6 . 
       FIG. 3B  is a top view in which the drum jig  1  and the metal member  11  in  FIG. 3A  are spread out linearly.  FIGS. 3C and 3D  are enlarged top view of the guide holes h 10  and h 4 , respectively, circled by the broken lines in  FIG. 3B . 
     Referring to  FIGS. 3A and 3B , the guide holes h of the metal member  11  and the positioning pins  6  of the drum jig  1  engage with each other, and the metal member  11  is transported, thereby rotating the drum jig  1 . The positioning pins  6  are formed on the drum jig  1  along the circumference thereof and protrude by an amount equal to the plate thickness of the metal member  11 . The diameter of each positioning pin  6  (e.g., 1.0 mm) has a certain clearance with respect to the diameter of each guide hole h (e.g., 1.5 mm). In this embodiment, the drum jig  1  is designed and manufactured with a minus tolerance so that the pitch p1 of the positioning pins may be smaller than the pitch p2 of the guide holes h. 
       FIG. 3  shows a relation that the drum jig  1  and the metal member  11  have when the distance between the head of the metal member  11  to be plated and the exit point O is L2 (i.e., corresponding to the state in  FIG. 11B ). 
     In this embodiment as well, the positioning pins  6  engage with the respective guide holes h at different positions as shown in  FIG. 3 . 
     For example, in the state shown in  FIG. 3 , the endmost positioning pin  6  of the drum jig  1  on the exit point O side engages with the guide hole h 4  such that it is in contact with an end portion of the guide hole h 4  on a rear B side (the entry point I side). As described earlier, the drum jig  1  is designed such that the pitch p1 of the positioning pins  6  is several micrometers smaller than the pitch p2 of the guide holes. This is a value which ensures that the positioning pin engages with the guide hole h on its end portion on the entry point I side. Thus, as the positioning pins are located closer to the entry point I side, the engagement positions of the positioning pins are closer to a front F side, and the engagement is ensured even on the entry point I side. In other words, in this state, an end portion of the guide hole h 5  is not in contact with the positioning pin  6 . 
     In this embodiment, at the same time that the guide hole h 4  exits by the movement of the metal member  11 , the brake unit  15  puts a brake put on the drum jig  1 , causing the drum jig  1  and the metal member  11  to slide on each other by an amount equal to a pitch difference per pitch (several micrometers) until the positioning pin  6  comes into contact with the end portion of the guide hole h 5 . In other words, while the metal member  11  moves, the endmost positioning pin  6  of the drum jig  1  on the exit point O side is always in contact with the end portion of the corresponding hole h on the rear B side. 
     Referring to  FIG. 11B  showing the conventional structure, when no brake is put on the drum jig  201 , the drum jig  201  rotates at the circumferential velocity equivalent to the moving velocity of the metal member  202 . In this case, even after the guide hole h 4  exits by the movement of the metal member  202 , the drum jig  201  and the metal member  202  do not slide on each other; therefore, the guide hole h 5  does not come into contact with the positioning pin  203 . More specifically, as the metal member  202  moves, the engagement positions of the positioning pins  203  are shifted more and more toward the front F side (the exit point O side) of the guide holes h. Further, as the metal member  202  moves on, the pitch differences are accumulated, and consequently, the endmost positioning pin  203  on the entry point I side comes into contact with the front F side of the guide hole h, separating the metal member  202  from the drum jig  201  ( FIG. 11D ). 
     In this embodiment, the brake unit (not shown in  FIG. 3 ) applies a load to the rotary shaft  2  to make the average circumferential velocity v1 of the drum jig  1  lower than the moving velocity v2 of the metal member  11 . Moreover, the load applied by the brake unit to the rotary shaft  2  is a load larger than a force with which the metal member  11  and the drum jig  1  in contact with each other move in the opposite directions (one being a direction indicated by the broken-line arrow) (i.e., they slide on each other) but not larger than a force causing deformation of the metal member  11 . 
     Thereby, the metal member  11  and the drum jig  1  can be slid in the relatively opposite directions (one being the direction indicated by the broken-line arrow) within the clearance between the positioning pin  6  and the guide hole h (e.g., about 0.5 mm). Consequently, the accumulated pitch differences between them can be cancelled. 
     Specifically, the positioning pins  6  can be ensured to engage with the guide holes h 8  and h 10  with which they conventionally fail to engage. 
     In this way, the accumulated pitch difference between the guide holes h and the positioning pins  6  is cancelled continually while the elongated metal member  11  is being plated, and therefore does not exceed the clearance between them. Thus, variations in the thickness of the plated films formed by spot plating can be reduced. 
     Further, in this embodiment, since the pitch p1 of the positioning pins  6  is smaller than the pitch p2 of the guide holes h, biting (deformation) can be prevented in the guide hole h closest to the entry point I of the drum jig  1  and the guide hole h closest to the exit point O of the drum jig  1 . 
     Referring to  FIGS. 3A, 3C, and 3D , when a load is applied by the brake unit to the drum jig  1 , the engagement position of the positioning pin  6  in the guide hole h 10  closest to the entry point I is shifted from the center of the guide hole h 10  toward the front side F in the travelling direction, making the clearance on the rear side B large ( FIG. 3C ). 
     Similarly, the engagement position of the positioning pin  6  in the guide hole h 4  closest to the exit point O is shifted toward the rear side B in the travelling direction, making the clearance on the front F side large ( FIG. 3D ). 
     In this embodiment, this state is maintained from the head to the tail of the metal member  11 . Thereby, biting on the guide holes h at the entry point I and the exit point O can be prevented. 
     Although the brake unit  15  is constantly applying a certain load to the drum jig  1 , the drum jig  1  and the metal member  11  do not necessarily slide on each other all the time. 
     For example, in  FIG. 3A , the guide hole h 4  closest to the exit point O is in contact with the positioning pin at its rear side, and in this case, a relation 
     (a static frictional force acting between the drum jig  1  and the metal member  11 )+(a force with which the guide hole h closest to the exit point O pushes the positioning pin  6 )&gt;(load applied by the brake unit  15 ) holds true. Thus, the drum jig  1  and the metal member  11  move at the same velocity, and do not slide on each other. 
     In contrast, at the moment when the metal member  11  moves on to cause the positioning pin  6  to exit the guide hole h 4  closest to the exit point O and make the next guide hole h 5  the one closest to the exit point O, 
     (a static frictional force acting between the drum jig  1  and the metal member  11 )&lt;(load applied by the brake unit  15 ) 
     holds true (since h 5  and the positioning pin are not in contact at this point). Thus, the drum jig  1  and the metal member  11  slide on each other, slowing down the drum jig  1 . 
     Then, at the moment when the positioning pin  6  comes into contact with the rear side of the guide hole h 5 , a relation 
     (a static frictional force acting between the drum jig  1  and the metal member  11 )+(a force with which the guide hole h closest to the exit point O pushes the positioning pin  6 )&gt;(a load applied by the brake unit  15 ) 
     holds true again, and the drum jig  1  and the metal member  11  move at the same velocity. 
     In other words, while the drum jig  1  and the metal member  11  move at the same velocity, the drum jig  1  slows down instantaneously every time the positioning pin  6  exits the guide hole h. Each sliding distance is equals to a pitch difference per pitch. 
       FIG. 4  shows a comparison between results of plating performed using the partial plating apparatus  10  of this embodiment and results of plating performed using a partial plating apparatus  200 , shown in  FIG. 5 , having a conventional structure. 
     In  FIG. 4A , the vertical axis denotes the thickness [μm] of plated films (Au), and the horizontal axis denotes the serial numbers of the plated spots (150 spots). The solid line represents the spot plating by the partial plating apparatus  10  of this embodiment, and the broken line presents the spot plating by the partial plating apparatus  200  having the conventional structure ( FIG. 10 ). Both apparatuses performed plating processing at the same current density, and the plated-film thickness of each plated spot was measured at a center portion thereof. 
     As is clear from this graph, the partial plating apparatus  10  of this embodiment clearly achieved reduction in the variations in the plated-film thickness, compared to the conventional one. 
     Specifically, referring to the comparison table in  FIG. 4B , the range (Range) between the maximum value and the minimum value of the plated-film thicknesses is reduced from the conventional value 0.21 μm to 0.14 μm. Moreover, the standard deviation (σ) is 0.022 in this embodiment while that for the conventional apparatus is 0.049. As can be seen from this result, the film-thickness variations were drastically reduced. 
     Next, a second embodiment of the present invention is described with reference to  FIGS. 5 to 8 . In the second embodiment, a region on the metal member  11  for performing plating processing is narrowed relative to that in the first embodiment. Note that components which are the same as those in the first embodiment are denoted by the same reference numerals used in the first embodiment, and are not described again here. 
       FIG. 5  shows schematic diagrams of a partial plating apparatus  20 . Specifically,  FIG. 5A  is a top view corresponding to  FIG. 1A ,  FIG. 5B  is a schematic top view (corresponding to  FIG. 2A ) showing a state where a metal member  11  is transported on a drum jig  1 . 
     Referring to  FIGS. 5A and 5B , as described earlier, the metal member  11  is transported along an outer circumferential portion of the drum jig  1 . Hereinbelow, a portion of the outer circumference of the drum jig  1  which is in contact with the metal member  11  is called and described as a contact region RC. 
     In a top view of the drum jig  1  (where the diameter of the drum jig  1  can be seen in a plan view and the shape of the drum jig  1  is visible as being substantially circular), the contact region RC of this embodiment is a region in contact with the metal member  11  over substantially the semi-circumference of the drum jig  1 , and is a region extending from their first contact point IP on an entry side I for the metal member  11  (an entry-side end portion) to an exit-side end portion OP where they come out of the contact on an exit side O. Although the contact region RC extends over substantially the semi-circumference as an example, the contact region RC may be a region larger than this (exceeding the semi-circumference). Further, since the drum jig  1  and the metal member  11  move with time, the contact region RC is not a particular (fixed) region of the drum jig  1  and the metal member  11 , but is a region where any portion of the outer circumference of the drum jig  1  and any portion of the metal member  11  come into contact while the drum jig  1  and the metal member  11  are moving (rotating) relative to each other. 
     In this embodiment, for convenience of illustration, the contact region RC is divided into a first region R 1  and a second region R 2 . The first region R 1  is a region of the contact region RC extending from the entry-side end portion IP of the metal member  11  (a start point of the contact region RC) to a position shifted therefrom forward in the travelling direction of the metal member  11  by a predetermined distance (a first arc r 1 ). The second region R 2  is a region extending from an end portion of the first region R 1  to the exit-side end portion OP of the metal member  11  (an end point of the contact region RC). Then, the partial plating apparatus  20  has a structure in which the metal member  11  is not plated in the first region R 1 , and the metal plate is plated in the second region R 2 . 
     Specifically, in the top view (plan view) in  FIG. 5 , a jet portion  82  has a fan shape whose arc is smaller than the ark r of the semicircle of the drum jig  1  (the contact region RC), and anodes  92  also have a similar fan shape. The jet portion  82  and the anodes  92  are arranged such that their arcs are along the arc (a second arc r 2 ) of the second region R 2 . 
       FIG. 6  is a perspective view seen in an SS-direction point of view in  FIG. 5A . 
     The jet portion  82  ejects a plating solution from an ejection vent (slit portion  8 S) shown in  FIG. 6 . In this embodiment, the anodes  92  are fan-shaped, and for example, the plate-shaped anodes  92  are arranged at an upper portion and a lower portion of the slit portion  8 S. The structure described above allows the metal member  11  not to be plated in the first region R 1  and to be plated in the second region R 2  (see  FIG. 5B ). 
     The reason for narrowing the region for plating the metal member  11  is described with reference to  FIG. 7 .  FIG. 7A  is a top view corresponding to  FIG. 2A , illustrating an overview of the partial plating apparatus  10  of the first embodiment.  FIG. 7B  is an enlarged view of a portion circled by the broken line in  FIG. 7A , and  FIG. 7C  is a top view illustrating an overview of the partial plating apparatus  20  of the second embodiment. 
     Referring to  FIG. 7A , the metal member  11  moves while their guide holes engage with positioning pins  6  of the drum jig  1 , as already described. The entry-side end portion IP of the contact region RC is a portion where the metal member  11  first comes into contact with the drum jig  1 , and at this position, a force exerted by the metal member  11  on the drum jig  1  is 0 (zero). 
     In this state, if the positioning pin  6  comes into contact with a side wall (inner wall) of the corresponding guide hole at the entry-side end portion IP, a frictional force produced therebetween might lift the metal member  11  slightly away from the outer circumferential surface of the drum jig  1  (the contact between the positioning pin  6  and the guide hole keeps the positioning pin  6  from entering all the way through the guide hole) (see the portion circled by the broken line in  FIG. 7A  and  FIG. 7B ). 
     Further, also in a case where the positioning pin  6  comes into contact with a side wall (inner wall) of the corresponding guide hole in the immediate vicinity of the entry-side end portion IP, if the force exerted by the metal member  11  on the drum jig  1  is negligibly small relative to the frictional force acting between the positioning pin  6  and the guide hole h, the metal member  11  might be similarly lifted away from the outer circumferential surface of the drum jig  1 . 
     The force exerted by the metal member  11  on the drum jig  1  is maximum at a middle portion CP between the entry-side end portion IP and the exit-side end portion OP of the contact region RC (at the peak portion in  FIG. 7A ). In other words, the force exerted by the metal member  11  on the drum jig  1  is minimum (zero) at the entry-side end portion IP, and becomes larger and larger toward the middle point CP. 
     Thus, in the first region R 1  which starts from the entry-side end portion IP as described earlier, the force exerted by the metal member  11  on the drum jig  1  is smaller than the frictional force between the positioning pin  6  and the guide hole. Thus, if the metal member  11  is lifted away from the drum jig  1 , this lifted state may continue. On the other hand, when the force exerted by the metal member  11  on the drum jig  1  gradually increases toward the middle point CP as the drum jig  1  rotates, and exceeds the frictional force between the guide hole and the positioning pin  6 , the guide hole and the positioning pin  6  engage with each other, cancelling the state where the metal member  11  is lifted away from the drum jig  1 . 
     To be more specific, looking at the overall contact region RC, in the first half of the contact region RC starting from the entry-side end portion IP (the first region R 1 ), the drum jig  1  may rotate with the metal member  11  being partly lifted from the drum jig  1 , as shown in the broken-line circle in  FIG. 7A . If the metal member  11  is plated in this state by being supplied with a plating solution from the jet portion  8 , variations in the thickness of the plated films occur, leading to a problem where the distribution of the thickness of plated films on the metal member  11  becomes uneven as a whole. 
     Thus, as shown in  FIG. 7C , in the partial plating apparatus  20  of the second embodiment, the plating processing is performed in the second region R 2  where the force exerted by the metal member  11  on the drum jig  1  exceeds the frictional force between the positioning pin  6  and the guide hole, and the metal member  11  is no longer lifted from the drum jig  1 . Thereby, the distribution of the thickness in the plated films can be evened. 
     Here, the first region R 1  and the second region R 2  are further described. 
     In visual definitions, the first region R 1  is a region forming a first arc r 1  (indicated by the thick broken line) extending along the outer circumference of the drum jig  1 , and the second region R 2  is a region forming the second arc r 2  (indicated by the solid line) extending along the outer circumference of the drum jig  1 . The length of the arc r 1  is smaller than that of the second arc r 2 . 
     A specific description is given using an example. The length of the first arc r 1  is from one fourth (r 1 =r/4) to one third (r 1 =r/3) of the overall arc r. The first region R 1  is a region forming the first arc r 1  from the entry-side end portion IP in the travelling direction of the metal member  11 . 
     Then, the jet portion  82  and the counter electrodes (anodes)  92  are provided only in the second region R 2 . Specifically, they are each formed into a fan shape in a top view (plan view) to form an arc along the second arc r 2  of the second region R 2 . Thereby, the metal member  11  is subjected to the plating processing only in the second region R 2  of the contact region RC, and this contributes to evening of the thickness of the plated films. 
       FIG. 8  shows a comparison between results of plating processing performed using the partial plating apparatus  20  of the second embodiment shown in  FIG. 6  and results of plating processing performed using the partial plating apparatus  10  of the first embodiment shown in  FIG. 1 . The results for the partial plating apparatus  10  of the first embodiment are the same as those shown in  FIG. 4 . Note that in the partial plating apparatus  20  of the second embodiment, the first region R 1  is formed such that the length of the first arc r 1  is one third of the overall contact region RC, and the jet portion  82  and the counter electrodes  92  which are fan-shaped are provided in the second region R 2 . 
     In  FIG. 8A , the vertical axis denotes the thickness [μm] of plated films (Au), and the horizontal axis denotes the serial numbers of the plated spots (150 spots). The triangular sports represent the spot plating by the partial plating apparatus  20  of the second embodiment, and the circular spots represent the spot plating by the partial plating apparatus  10  of the first embodiment ( FIG. 1 ). The plated-film thickness of each plated spot was measured at a center portion thereof. 
     As is clear from this graph, the partial plating apparatus  20  of the second embodiment achieved reduction in the variations in the plated-film thickness, compared to the partial plating apparatus  10  of the first embodiment. 
     Specifically, referring to the comparison table in  FIG. 8B , the range (Range) between the maximum value and the minimum value of the plated-film thicknesses is reduced from 0.14 μm of the first embodiment to 0.03 μm. Moreover, the standard deviation (σ) of the second embodiment is 0.006 while that for the first embodiment is 0.022. As can be seen from this result, the film-thickness variations were drastically reduced. 
     The target value of the average film thickness (Ave) was set to 0.5 μm for the partial plating apparatus  10  of the first embodiment and to 0.45 μm for the partial plating apparatus  20  of the second embodiment. 
       FIG. 9  is a diagram showing a partial plating apparatus  30  of a third embodiment of the present invention, and is a top view corresponding to  FIG. 1A . The same components as those in the first and second embodiments are denoted by the same reference numerals as those in the first and second embodiments, and are not described again here. 
     A metal member  11  may be plated only in a second region R 2 . To be more specific, a jet portion  8  is formed into a substantially semicircular shape as in the first embodiment, and only counter electrodes  92  may be formed into a fan shape. In this case, even though a plating solution is supplied from the jet portion  8  in the first region R 1 , no plating is performed there since there are no counter electrodes  92  (indicated by the broken-line arrows). The plating is performed only in the second region R 2  (indicated by the solid-line arrows). Thus, the same advantageous effects as those offered by the second embodiment can be obtained. Other configurations are the same as those in the second embodiment. 
     Note that an even distribution may be obtained for the thickness in the plated films even when the length of the first arc r 1  of the first region R 1  is shorter than that in the above-described example (e.g., even when r 1 =r/5). 
     In the partial plating apparatus  20  of this embodiment, the plating could be performed with an even film-thickness distribution by making one third of the overall contact region RC the first region R 1  (see  FIG. 7 ). 
     On the other hand, even if the length of the first arc r 1  extends beyond the middle point CP of the contact region RC, the plated-film thickness distribution is even in the second region R 2 . However, if the first arc r 1  is too long (or the second region R 2  is too small), an area which can be plated is reduced, lowering the productivity. For this reason, it is preferable that the first region R 1  is as small as possible. For this reason, in this embodiment, the first region R 1  is a region in which the length of the first arc r 1  is one third of the overall arc r of the contact region RC. 
     As described above, a partial plating method of this embodiment performs partial plating on the metal member  11  transported along the outer circumferential portion of the drum jig  1  of the partial plating apparatus. Specifically, the metal member  11  is not plated in the first region R 1  of the contact region RC where the metal member  11  is in contact with part of the outer circumferential portion of the drum jig  1 , the first region R 1  extending from the entry-side end portion IP for the metal member  11  to a position away therefrom by a predetermined distance. Then, the metal member  11  is plated in the second region R 2  extending from the end portion of the first region R 1  to the exit-side end portion OP for the metal member  11 . 
     As described above, the film-thickness variations are likely to occur in the first half of the contact region RC after the entry-side end portion IP (the first region R 1 ), and this is also true in the conventional structure. To be more specific, for example, even if a partial plating apparatus does not include the brake unit  15  as the partial plating apparatuses  10  to  30  of the above embodiments do, the film-thickness variations are likely to be poor in the first half of the contact region RC. 
     However, according to the partial plating method of this embodiment, the metal member  11  is plated not in the first half (the first region R 1 ) of the drum jig  1  having a poor film-thickness distribution, but only in the second region R 2 . Hence, variations in the film-thickness distribution can be reduced compared to a plating method performing plating over the entire contact region RC. 
     REFERENCE SIGNS LIST 
     
         
           1  drum jig 
           2  rotary shaft 
           3  opening portion 
           4  support roll 
           5  belt 
           6  positioning pin 
           8 ,  82  jet portion 
           9 ,  92  counter electrode (anode) 
           10 ,  20 ,  30 ,  40 ,  50  partial plating apparatus 
           11  metal member (member to be plated) 
           15  brake unit 
         h, h 1  to h 10  guide hole 
         RC contact region 
         R 1  first region 
         R 2  second region 
         r 1  first arc 
         r 2  second arc