Patent Publication Number: US-2016230285-A1

Title: Plating apparatus and sensing device using same

Description:
TECHNICAL FIELD 
     The present invention relates to a plating apparatus for applying electrolytic plating or electroless plating on the face of a plated object, and a sensing device using the same. 
     BACKGROUND ART 
     In recent years, a plating technology has been applied to various technical fields such as a semiconductor wiring technique. Further, in order to determine plating conditions at the time of producing plated products, plating tests may be performed before starting the production, such as with a small-sized plating apparatus. 
     For example, Patent Document 1 discloses an electroplating testing apparatus including: a tank which has at least a bottom plate and a side plate, and is injected with a plating solution; and a cathode and anode plates which are horizontally placed so as to face each other in the plating solution in the tank, wherein one of the cathode and anode plates as a plated object is placed below the other, an opening is formed in the side plate of the tank for inserting the cathode and anode plates respectively into the tank, and a shield plate is detachably arranged in the tank for shielding the opening. The side plate of the tank includes a plurality of grooves for retaining at least one of the cathode and anode plates in a horizontal state, so as to allow adjusting the gap between the cathode and anode plates. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document  1 : Japanese Patent Application Publication No. 2006-299367 (claims 1-3, FIG. 1) 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, the plating apparatus described in Patent. Document 1 needs to have the opening and the grooves in the side plate of the tank as well as the tank for accommodating the cathode and anode plates, causing the structure to be larger in size and to be complex, and a manufacturing cost and a material cost to increase accordingly. Therefore, a simpler and more compact plating apparatus has been required. 
     Moreover, in the research and development of a plated object in recent years, a plating apparatus has been required that allows for observing production process of a plated object during plating, such as with a high performance microscope (e.g. Raman microscope). 
     The present invention has been made in view of the above problems, and provides, as a primary subject, a plating apparatus that is simpler and can be easily made smaller in size than before and a sensing device using the same. 
     Further, the present invention provides, as a secondary subject, a plating apparatus that allows for observing a production process of a plated object. 
     Means to Solve the Problems 
     To solve the problems above, a plating apparatus according to the present invention includes: a holding member ( 2 ) that holds a plated object (W) specified as a cathode; a spacer ( 4 ) that is stacked on the holding member ( 2 ) via a first seal member ( 3 ) in an annular shape surrounding the plated object (W), and has a through portion ( 45 ) from which the plated object (W) is exposed and which stores a plating solution; and an anode member ( 6 ) that is stacked on the spacer ( 4 ) via a second seal member ( 5 ) in an annular shape surrounding the through portion ( 45 ), and has an anode layer ( 62 ) arranged to face the plated object (W) which is exposed from the through portion ( 45 ). 
     According to the structure, a plating apparatus ( 1 ) can be easily formed by simply stacking the holding member ( 2 ) to hold the plated object (W), the spacer ( 4 ) having the through portion ( 45 ) to store the plating solution and the anode member ( 6 ) having an anode via the first and second seal members ( 3 ,  5 ). Therefore, the plating apparatus ( 1 ) can be simpler and smaller in size as compared with the plating apparatus described in Patent Document 1, for example, because the tank having a complex structure is not necessary. Further, in the present invention, a distance between the cathode and the anode can be easily adjusted by exchanging the spacer ( 4 ) with one having different thickness. 
     Further, the spacer ( 4 ) includes a spacer body ( 41 ) made of an insulator and an anode-side conductive layer ( 43 ) arranged on a face, which faces the anode member ( 6 ), of the spacer body ( 41 ), the anode member ( 6 ) includes an anode member body ( 61 ) made of an insulator and an anode layer ( 62 ) specified as the anode arranged on a face, which faces the spacer ( 4 ), of the anode member body ( 61 ), the anode-side conductive layer ( 43 ) is connected inside the second seal member ( 5 ) to the anode layer ( 62 ), and the anode-side conductive layer ( 43 ) is connected outside the second seal member ( 5 ) to a power supply (PW). 
     According to the structure, the anode-side conductive layer  43  is connected inside the second seal member ( 5 ) to the anode layer ( 62 ), and the anode-side conductive layer ( 43 ) is connected outside the second seal member ( 5 ) to the power supply (PW), allowing for supplying electricity to the anode layer ( 62 ) while maintaining between the spacer ( 4 ) and the anode member ( 6 ) in watertight. 
     Further, the anode member body ( 61 ) preferably includes a light transmissive window ( 64 ) for observing the plated object (W) exposed from the through portion ( 45 ), and the anode layer ( 62 ) is preferably formed around the window ( 64 ). 
     The structure allows for observing the plating itself produced on the plated object (W), via the window ( 64 ) during plating. 
     Furthermore, the window ( 64 ) preferably has a thickness (t 1 ) smaller than that of other portions of the anode member body ( 61 ). 
     This structure allows for, for example, arranging a microscope used for observation closer to the cathode. Consequently, the plated object (W) during plating can be suitably observed. 
     Moreover, the thickness (t 1 ) of the window ( 64 ) is preferably in a range of 0.05 mm≦t1≦2 mm. 
     Since the structure allows for suitably restraining refraction and scattering of light which is transmitted through the window ( 64 ), the plated object (W) during plating can be suitably observed in a state where the influence caused by the window ( 64 ) is reduced. 
     Still moreover, the anode member body ( 61 ) preferably has a tapered portion ( 64   a ) around the window (W) which declines toward the window ( 64 ). 
     According to the structure, the anode member body ( 61 ) has the tapered portion ( 64   a ) around the window ( 64 ) that declines toward the window ( 64 ), which prevents the microscope (M) from contacting the anode member ( 6 ), for example, when the microscope (M) is used for observing the plated object (W). 
     Still moreover, the thickness (t 2 ) of the spacer ( 4 ) is preferably in a range of 0.05 mm≦t2≦1 mm. 
     According to the structure, the thickness (depth) of the plating solution stored in the through portion ( 45 ) is small, to allow for observing the plated object (W) even if the plating solution is colored. Further, by shortening the distance between electrodes remarkably, a steep diffusion gradient of ion concentration can be obtained. 
     Still moreover, the spacer ( 4 ) preferably includes a cathode-side conductive layer ( 42 ) arranged on a face, which faces the holding member ( 2 ), of the spacer body ( 41 ), the cathode-side conductive layer ( 42 ) is connected inside the first seal member ( 3 ) to the plated object (W), and the cathode-side conductive layer ( 42 ) is connected outside the first seal member ( 3 ) to the power supply (PW). 
     The structure allows for supplying electricity to the plated object (W) while maintains between the spacer ( 4 ) and the holding member ( 2 ) in watertight. 
     Still moreover, the spacer ( 4 ) preferably includes a reference electrode conductive layer ( 44 ) insulated from the anode-side conductive layer ( 43 ) on a face, which faces the anode member ( 6 ), of the spacer body ( 41 ), and the anode member ( 6 ) preferably includes a reference electrode layer ( 63 ) insulated from the anode layer ( 62 ) on a face, which faces the spacer ( 4 ), of the anode member body ( 61 ), the reference electrode conductive layer ( 44 ) is connected inside the second seal member ( 5 ) to the reference electrode layer ( 63 ), and the reference electrode conductive layer ( 44 ) is connected outside the second seal member ( 5 ) to the measuring device. 
     According to the structure, the electric potential of the anode can be measured using the the reference electrode layer ( 63 ) while the spacer ( 4 ) and the anode member ( 6 ) can be maintained in watertight. 
     Still moreover, the holding member ( 2 ) or the anode member ( 6 ) preferably includes a plating solution supply passage ( 27 ) through which a plating solution is supplied to the through portion ( 45 ), and the holding member ( 2 ) or the anode member ( 6 ) preferably includes a plating solution discharge passage ( 26 ) through which the plating solution is discharged from the through portion ( 45 ). 
     The structure allows the plating solution in the through portion ( 45 ) to be suitably maintained by supplying the solution from the plating solution supply passage ( 27 ) to the through portion ( 45 ) and discharging it from the through portion ( 45 ) to the plating solution discharge passage ( 28 ). 
     Still moreover, in a case where the plating solution is an electroless plating solution, a measuring device instead of the power supply (PW) is preferably connected to measure the electric potential across the anode and the cathode. 
     The structure allows the plating apparatus ( 1 ) according to the present invention to apply the electroless plating and to measure the electric potential across the anode and the cathode. 
     Still moreover, the present invention provides a sensing device using the above-described plating apparatus ( 1 ), wherein the anode-side conductive layer ( 43 ) is constituted with a plurality of anode--side conductive layers ( 43 B) insulated from one another, the anode layer ( 62 ) is constituted with the same number of anode layers ( 62 B) insulated from one another as the anode-side conductive layers ( 43 B), and portions ( 62 Bb) of anode layers ( 62 B) exposed from the through portion ( 45 ) are respectively modified with reaction groups different from one another. 
     The structure allows the plating apparatus ( 1 ) to be used as a sensing device, for example, by modifying different reaction groups to the plurality of anode layers ( 62 B). 
     EFFECT OF THE INVENTION 
     The present invention can provide a plating apparatus which is simpler and can be easily made smaller in size than before, and a sensing device using the same. Further, the present invention can provide a plating apparatus that allows for observing a production process of a plated object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a plating apparatus according to a first embodiment; 
         FIG. 2  is an exploded perspective view of the plating apparatus according to the first embodiment; 
         FIG. 3  is an exploded cross-sectional view taken along a III-III line in  FIG. 1 ; 
         FIG. 4  is an exploded cross-sectional view taken along a IV-IV line in  FIG. 1 ; 
         FIG. 5  is an assembled cross-sectional view taken along the III-III line in  FIG. 1 ; 
         FIG. 6A  is a plan view of a holding member and  FIG. 6B  is a cross-sectional view taken along a VIb-VIb line in  FIG. 6A ; 
         FIG. 7A  is a plan view of a spacer and  FIG. 7B  is a bottom view of the spacer; 
         FIG. 8A  is a plan view of an anode member,  FIG. 8B  is a cross-sectional view taken along a VIIIb-VIIIb line in  FIG. 8B , and  FIG. 8C  is a bottom view of the anode member; 
         FIG. 9  is an exploded cross-sectional view of a plating apparatus according to a second embodiment; 
         FIG. 10  is a plan view of the spacer in a sensing device using the plating apparatus; and 
         FIG. 11  is a bottom view of an anode member in the sensing device using the plating apparatus. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     Next, a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the first embodiment, a description will be given of an exemplary case of applying electrolytic plating on a plated object W. It is noted that a direction will be indicated in the description based on the “front-back”, “up-down” and “right-left” directions shown by arrows in  FIG. 1 . 
     A plating apparatus  1  according to the first embodiment is a thin plating apparatus formed in a simple stacked structure. The plating apparatus  1  has an advantage to allow for observing a production of a plated object and a reaction at a solid/liquid interface during plating, for example, using a special microscope such as a Raman microscope. 
     As shown in  FIGS. 1 and 2 , the plating apparatus  1  is an apparatus for plating the plated object W, and includes as main components a holding member  2   a,  a first seal member  3 , a spacer  4 , a second seal member  5  and an anode member  6 , in order from the bottom. Further, the plating apparatus  1  includes a cathode-side conducting member  7  and an insulating member  8  below the holding member  2 . Still further, the plating apparatus  1  includes an anode-side conducting member  9  above the anode member  6 . 
     As shown in  FIG. 2 , the plated object W is an object on which plating is applied, and is formed of a thin plate member having a square shape, for example, in a plan view. The plated object W is not particularly limited to, and can be various electronic components such as a circuit board, a semiconductor chip and a device package. Also, the plated object W can be a test piece such as made of a mere metal plate. As shown in  FIG. 3 , in the first embodiment, the plated object W includes an insulating substrate W 1  and a plated layer W 2  that is stacked on the insulating substrate W 1 . The plated layer W 2  is connected to the negative pole of a power supply PW to function as a cathode. 
     As shown in  FIGS. 1 to 6B  (in particular  FIGS. 6A, 6B ), the holding member  2  is a member for holding the plated object W. The holding member  2  is formed with, for example, an insulator such as PEEK resin (Poly Ether Ether Ketone). The holding member  2  includes a rectangular bottom wall  21  in a plan view and a sidewall  22  extending upward from four sides of the bottom wall  21 . As shown in  FIGS. 1 and 2 , a space surrounded by the side wall  22  accommodates the plated object W, the first seal member  3 , the spacer  4 , the second seal member  5 , and the anode member  6 . 
     A recess  23  for mounting the plated object W is formed in the central portion of the upper face of the bottom wall  21 . Further, a concave groove  24  in an annular shape for mounting the first seal member  3  is formed on the upper face of the bottom wall  21  so as to surround the recess  23 . 
     Further, the bottom wall  21  includes, outside the concave groove  24 , a plurality of probe insertion holes  25  (eight in the first embodiment) for inserting probes P described later. 
     Still further, the bottom wall  21  includes a plating solution supply passage  27  which supplies the plating solution through a through portion  45  of the spacer  4  described later, and a plating solution discharge passage  28  which discharges the plating solution through the through portion  45 . In the first embodiment, an opening  27   a  at the inlet side of the plating solution supply passage  27  is formed at the distal end of a cylinder  27   c  protruding from the right side of the bottom wall  21 , and an opening  27   b  at the outlet side of the plating solution supply passage  27  is formed on the upper face of the bottom wall  21  and inside the annular concave groove  24  on the front side of the recess  23 . Also, an opening  28   a  at the inlet side of the plating solution discharge passage  28  is formed on the upper face of the bottom wall  21  and inside the annular concave groove  24  on the back side of the recess  23 , and an opening  28   b  at the outlet side of the plating solution discharge passage  28  is formed at the distal end of a cylinder  28   c  protruding from the left side of the bottom wall  21 . The cylinders  27   c ,  28   c  are covered with caps  27   d ,  28   d , respectively. The caps  27   d ,  28   d  prevent plating solution flow pipes (not shown) connected to the cylinders  27   c ,  28   c  from falling off. 
     As shown in  FIGS. 2 to 5 , the first seal member  3  is an elastic member which seals between the holding member  2  and the spacer  4  and is constituted by an O-ring having an annular shape, for example, in a plan view. The first seal member  3  is mounted in the concave groove  24  of the bottom wall  21 . The first seal member  3  is arranged to surround the plated object W. Also, the first seal member  3  is arranged to surround the through portion  45  of the spacer  4  (described later). 
     As shown in  FIGS. 2 to 5 and 7A, 7B  (in particular FIGS,  7 A,  7 B), the spacer  4  is a member which maintains the distance between the plated object W and an anode (described later) at a predetermined distance. In the first embodiment, the spacer  4  is formed of a thin plate member having a square shape, for example, in a plan view. The spacer  4  includes a. spacer body  41  made of an insulator, a cathode-side conductive layer  42  arranged on the face, which faces the holding member  2 , of the spacer body  41 , an anode-side conductive layer  43  and a reference electrode conductive, layer  44  arranged on the face, which faces the anode member  6 , of the spacer body  41 , and the through portion  45  formed through at the central portion of the spacer  4 . 
     The spacer body  41  is a portion which insulates the cathode-side conductive layer  42  from the anode-side conductive layer  43 , and is formed of, for example, an insulator such as borosilicate glass. 
     The cathode-side conductive layer  42  is a conductive layer which supplies electricity to the plated object W, and is formed of, for example, a metal material such as platinum. The cathode-side conductive layer  42  is formed by the technique such as sputtering or vacuum evaporation. The cathode-side conductive layer  42  is connected inside the first seal member  3  to the plated object W, and is connected outside the first seal member  3  to the negative pole of the power supply PW via the probes P and the cathode-side conducting member  7  (see  FIGS. 1 and 5 ). 
     The anode-side conductive layer  43  is a conductive layer which supplies electricity to an anode layer  62  (described later), and is formed of, for example, a metal material such as platinum. The anode-side conductive layer  43  is formed by the technique such as sputtering or vacuum evaporation. The anode-side conductive layer  43  is connected inside the second seal member  5  to the anode layer  62  (described later), and is connected outside the second seal member  5  to the positive pole of the power supply PW via the probes P and the anode-side conducting member  9  (see  FIGS. 1 and 5 ). 
     The reference electrode conductive layer  44  is a conductive layer which is electrically connected to a reference electrode layer  63  (described later), and is formed of, for example, a metal material such as platinum. The reference electrode conductive layer  44  is formed by the technique such as sputtering or vacuum evaporation. Portions without the conductive layer are provided at both sides of the reference electrode conductive layer  44  (more specifically, between the the reference electrode conductive layer  44  and the anode-side conductive layer  43 ) and are insulated from the anode-side conductive layer  43 . The reference electrode conductive layer  44  is connected inside the second seal member  5  to the reference electrode layer  63  (described later), and is connected outside the second seal member  5  to a measuring device (not shown) via the probes P (described later). 
     The through portion  45  is an opening from which a portion of the plated object W is exposed and which stores the plating solution, and is formed through in the up-down. direction substantially at the central portion of the spacer  4 . The through portion  45  is formed substantially in an elongated diamond shape in a plan view where the length in the front-back direction is longer than that in the right-left direction. The opening  27   b  at the outlet side of the plating solution supply passage  27  is exposed in the vicinity of the end portion at the front side of the through portion  45  (see  FIG. 2 ). Also, the opening  28   a  at the inlet side of the plating solution discharge passage  28  is exposed in the vicinity of the end portion at the back side of the through portion  45  (see  FIG. 2 ). Thus, the plating solution which has flowed from the opening  27   b  into the through portion  45  flows from the front to the back inside the through portion  45  to finally flow out from the opening  28   a.    
     The thickness t 2  of the spacer  4  is not particularly limited to, but is preferable in the range of 0.05 mm≦t2≦1 mm, and is more preferable in the range of 0.10 mm≦t2≦0.20 mm. In the first embodiment, the spacer  4  is formed to have the thickness t 2  of approximately 0.10 mm. Making the thickness t 2  of the spacer  4  very thin allows for observing the plated object W through a window  64  (described later), even when the plating solution is not so transparent. 
     It is noted that a plurality of different spacers  4  having a different thickness t 2  may be prepared in advance to be exchanged depending on applications. For example, if the plating solution is very transparent, a spacer  4  having a relatively thicker thickness t 2  can be used. In the first embodiment, the spacer  4  having an extremely thin thickness t 2  of about 0.10 mm allows for observing the reaction at the solid/liquid interface in more detail. 
     As shown in  FIGS. 2 to 5 , the second seal member  5  is a resilient member for sealing between the spacer  4  and the anode member  6 , and is formed of an O-ring having an annular shape, for example, in a plan view. The second seal member  5  is mounted in a concave groove  65  formed in the lower face of the anode member  6 . The second seal member  5  is arranged to surround the through portion  45  of the spacer  4 . Further, the second seal member  5  is arranged to surround the window  64  of the anode member  6 . 
     As shown in  FIGS. 1 to 5 and 8A to 8C  (in particular,  FIGS. 8A to 8C ), the anode member  6  mainly includes: an anode member body  61 ; the anode layer  62  and the reference electrode layer  63  provided on the face, which faces the holding member  2 , of the anode member body  61 ; the window  64  formed in the central portion of the anode member body  61 ; and the concave groove  65  formed in the face, which faces the holding member  2 , of the anode member body  61 . The anode member  6  covers the through portion  45  of the spacer  4  from above. 
     The anode member body  61  is a plate-like member having a rectangular shape in a plan view. The anode member body  61  is made of an insulating material, such as transparent (light transmissive) quartz glass. 
     The anode layer  62  is an anode portion which is electrically connected to the positive pole of the power supply PW, and is formed between the window  64  and the concave groove  65  described later on the face, which faces the holding member  2 , of the anode member body  61 . That is, the anode layer  62  is formed around the window  64 . The anode layer  62  is, for example, formed of a metal material such as platinum. The anode layer  62  is formed by the technique such as sputtering or vacuum evaporation. The anode layer  62  is connected inside the second seal member  5  to the anode-side conductive layer  43 . 
     The reference electrode layer  63  is a portion to be a reference electrode which is electrically connected to the measuring device (not shown). The reference electrode layer  63  is arranged at a position facing the reference electrode conductive layer  44 . The reference electrode layer  63  is, for example, formed of a metal material such as platinum. The reference electrode layer  63  is formed by the technique such as sputtering or vacuum evaporation. Portions without the conductive layer are provided at both sides of the reference electrode layer  63  (more specifically, between the reference electrode layer  63  and the anode-side layer  62 ) and are insulated from the anode-side layer  62 . The reference electrode layer  63  is connected inside the second seal member  5  to the reference electrode conductive layer  44 . The reference electrode layer  63  allows for measuring electric potential of the anode (anode layer  62 ) as a working electrode. 
     The window  64  is a transparent observation window for observing (or monitoring) the plated object W. The window  64  is arranged at the central portion of the anode member body  61 , and formed in a circular shape in a plan view. The window  64  is formed of quartz glass which is the same material as, for instance, the anode member body  61 . The thickness t 1  of the window  64  is thinner than that of other portions of the anode member body  61  (for example, the outer peripheral portion of the anode member body  61 ). The thickness t 1  of the window  64  is preferably in the range of 0.05≦mm t1≦2 mm, and even more preferably in the range of 0.10 mm≦t1≦0.20 mm. In the first embodiment, the window  64  is formed to have the thickness t 1  of approximately 0.13 mm. Making the thickness t 1  extremely thin allows for, when the plated object is observed with a microscope, reducing refraction and scattering of light transmitted through the window  64 , to allow for observing the plated object precisely. 
     A tapered portion  64   a  in a truncated cone shape is arranged around the window  64 , the portion  64   a  declining toward. the window  64 . When the microscope is set on the window  64 , the tapered portion  64   a  reduces interference between the microscope and the anode member body  61 . In other words, the tapered portion  64   a  around the window  64  allows a larger microscope in size to be arranged closer to the window  64 . 
     The concave groove  65  is an annular groove for mounting the second seal member  5  and is formed on the lower face of the anode member body  61 . The concave groove  65  is formed to surround the window  64 . The concave groove  65  reduces the positional displacement of the second seal member  5  and has a function to facilitate the anode layer  62  to contact the anode-side conductive layer  43 . 
     Further, the anode member  6  includes a plurality of probe insertion holes  66  (eight in the first embodiment) outside the concave groove  65  for inserting the probes P (described later). One of the probe insertion holes  66 A is formed at a position corresponding to the reference electrode conductive layer  44  (see  FIG. 7A ). 
     As shown in  FIGS. 1 to 5 , the cathode-side conducting member  7  is a member which supplies a current to the plated object W as a cathode. The cathode-side conducting member  7  is made of a metal plate having a rectangular shape in a plan view and is stacked on the lower side of the holding member  2 . The cathode-side conducting member  7  has a plurality of probe mount holes  71  through which respective probes P are mounted. Further, the cathode-side conducting member  7  is connected to the negative pole of the power supply PW (not shown) via a protrusion  72  protruding on the left side face. Thus, the negative pole of the power supply PW is electrically connected to the plated object W via the cathode-side conducting member  7 , the probes P and the cathode-side conductive layer  42 . 
     The insulating member  8  is a member which insulates the cathode-side conducting member  7  from a face (for example, the floor) on which the plating apparatus  1  is placed. The insulating member  8  is made of an insulating material such as PEEK resin (Poly Ether Ether Ketone). The insulating member  8  is made of a plate member having a square shape in a plan view and covers the lower face of the cathode-side conducting member  7 . 
     The anode-side conducting member  9  is a member which supplies a current to the anode layer  62 . The anode-side conducting member  9  is made of a metal plate having an annular shape in a plan view and is stacked on the upper side of the anode member  6 . The anode-side conducting member  9  has an opening  91  at the center through which the window  64  is exposed. The anode-side conducting member  9  has a plurality of probe mount holes  92  through which the respective probes P are mounted. Further, the anode-side conducting member  9  is connected to the positive pole of the power supply PW (not shown) via a protrusion  93  protruding from the front side face. Thus, the positive pole of the power supply PW is electrically connected to the anode layer  62  via the anode-side conducting member  9 , the probes P and the anode-side conductive layer  43 . 
     The Probes P are metal members which electrically connect the cathode-side conducting member  7  with the cathode-side conductive layer  42 , and, the anode-side conducting member  9  with the anode-side conductive layer  43 , respectively. As shown in  FIG. 3 , each probe P includes a cylinder Pi having a bottomed cylindrical shape and a piston P 2  which is provided retractably in the cylinder P 1 . The cylinders P 1  are fitted into the probe mount holes  71 ,  92  and are inserted into the probe insertion holes  25 ,  66 , in a state that the pistons P 2  are directed to the cathode-side conductive layer  42  or the anode-side conductive layer  43 . The piston P 2  is biased in the protruding direction by a spring (not shown) accommodated in the cylinder P 1  to be in contact with the cathode-side conductive layer  42  or the anode-side conductive layer  43 . 
     It is noted that, though not shown, one of the eight probes P on the anode side arranged at a position corresponding to the reference electrode conductive layer  44  has a cylinder P 1  surrounded with an insulator to be insulated from the anode-side conducting member  9 . The probe P corresponding to the reference electrode conductive layer  44  is connected to the measuring device (not shown), and its piston P 2  is in contact with the reference electrode conductive layer  44 . The reference electrode conductive layer  44  is connected inside the second seal member  5  to the reference electrode layer  63 . Accordingly, electric potential of the reference electrode layer  63  can be measured with the measuring device. 
     As shown in  FIG. 4 , the holding member  2 , the spacer  4 , the anode member  6 , the cathode-side conducting member  7 , the insulating member  8  and the anode-side conducting member  9  have a plurality of bolt insertion holes  26 ,  46 ,  67 ,  73 ,  81 ,  94  (eight in the first embodiment, except for the anode-side conducting member  9  which has only four holes  94 ) for inserting bolts B (see  FIG. 1 ) which fasten the respective members in a stacked state. Female screws are formed on the inner peripheral face of the bolt insertion holes  81  in the insulation member  8  for screwing with the bolts B (see  FIG. 1 ). 
     The plating apparatus  1  according to the first embodiment is basically formed as described above. Next, usage and advantageous effects of the plating apparatus  1  will be described with reference to  FIGS. 1 to 8C  (especially  FIG. 5 ). 
     As shown in  FIG. 5 , the plating apparatus  1  according to the first embodiment includes the holding member  2  which holds the plated object W, the spacer  4  having the through portion  45 , and the anode member  6  having the anode layer  62 , all of which being stacked via the first seal member  3  and the second seal member  5 . Thus, while the plated object W faces the anode layer  62  via the through portion  45 , the through portion  45  is closed in watertight so that the plating solution can be stored. Therefore, the plating apparatus  1  can be formed easily by simply stacking the respective members. A tank having a complex structure is not necessary compared with, for example, the plating apparatus described in Patent Document 1, and this allows the plating apparatus  1  to be simplified and reduced in size. Further, the plating apparatus  1  according to the first embodiment may have a plurality of spacers  4  having a different thickness t 2  prepared in advance, so that the distance between the plated object W and the anode layer  62  can be adjusted easily by exchanging the spacers depending on plating conditions and test conditions. 
     Further, the plating apparatus  1  according to the first embodiment includes the anode-side conductive layer  43  connected inside the second seal member  5  to the anode layer  62  and the anode-side conductive layer  43  connected outside the second seal member  5  to the positive pole of the power supply PW via the probes P and the anode-side conducting member  9 , allowing for supplying electricity to the anode layer  62  while maintaining between the spacer  4  and the anode member  6  in watertight. 
     Further, the anode member body  61  includes the window  64  having a light transmitting property for observing the plated object W which is exposed from the through portion  45 , and the anode layer  62  is formed around the window  64 . Therefore, as shown in  FIG. 5 , the plated object W during plating can be observed (or monitored) through the window  64 , such as a Raman microscope M. 
     Still further, in the first embodiment, the thickness t 1  of the window  64  set to be very thin, for example, to 0.13 mm can suitably reduce the refraction and scattering of light transmitted through the window  64  to allow for improving observation accuracy with the Raman microscope M. 
     Yet further, the anode member  6  includes a tapered portion  64   a  and the anode-side conducting member  9  includes the opening  91 , to allow the Raman microscope M to be arranged close to the window  64 , such as with the anode member  6  and the anode-side conducting member  9  being prevented from interfering with the Raman microscope M. 
     In addition, in the first embodiment, the thickness t 2  of the spacers  4  is set to be very thin, for example, to 0.10 mm. Therefore, the thickness (depth) of the plating solution stored in the through portion  45  is reduced, to allow for observing the plated object W, even if, for example, the plating solution is colored. Further, in the first embodiment, the thickness t 2  of the spacer  4  is set to be extremely thin, approximately 0.10 mm, to allow for observing the reaction at the solid/liquid interface in more detail. 
     Besides, the plating apparatus  1  according to the first embodiment includes the cathode-side conductive layer  42  connected inside the first seal member  3  to the plated object W and the cathode-side conductive layer  42  connected outside the first seal member  3  to the power supply PW via the probes B, to allow for supplying electricity to the plated object W while maintaining between the spacer  4  and the holding member  2  in watertight. 
     Moreover, since the holding member  2  includes the plating solution supply passage  27  which supplies the plating solution to the through portion  45  and the plating solution discharge passage  28  which discharges the plating solution from the through portion  45 , the plating solution is supplied through the plating solution supply passage  27  to the through portion  45  and is discharged from the through portion  45  through the plating solution discharge passage  28 , to allow the plating solution in the through portion  45  to be maintained. in a suitable condition. 
     Next, a plating apparatus  1 A according to a second embodiment will be described with reference to  FIG. 9 . In the description, the same components as those in the first. embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. 
     As shown in  FIG. 9 , the plating apparatus  1 A according to the second embodiment is mainly different from the plating apparatus of the first embodiment described above in that the probes P directly contact the lower face of a plated object WA and a spacer  4 A does not have the cathode-side conductive layer  42 . 
     The plated object WA used in the plating apparatus  1 A according to the second embodiment is a member of which lower face (back face), which faces the holding member  2 A, is electrically connected to the upper face (front face) which is to be applied with plating, and is formed of a simple metal plate, for example. 
     The holding member  2 A includes an annular concave groove  23   a  in the bottom face of the recess  23  on which the plated object WA is mounted. Further, probe insertion holes  23   b  into which the probes P are inserted are formed through inside the concave groove  23   a  in the bottom face of the recess  23 . It is noted that probe mount holes  74  to be fitted with the probes P are formed through in the cathode-side conducting member  7  at positions corresponding to the probe insertion holes  23   b.    
     A third seal member  10  is arranged between the holding member  2 A and the plated object WA. The third seal member  10  is mounted along the concave groove  23   a . The third seal member  10  can maintain between the holding member  2 A and the plated object WA in watertight, to prevent the plating solution from leaking through the probe insertion holes  23   b  and the probe mount holes  74 . 
     A spacer  4 A includes the spacer body  41  and the anode-side conductive layer  43 , but does not include the cathode-side conductive layer  42  (see  FIG. 3 ). This is because the probes P are in direct contact with the lower face of the plated object WA. 
     In the plating apparatus  1 A according to the second embodiment, the probes P are in direct contact with the lower face of the plated object WA and the cathode-side conductive layer  42  of the spacer  4 A is eliminated, to allow for simplifying the structure of the plating apparatus  1 . 
     The present embodiment has been described in detail with reference to the drawings as above, but the present invention is not limited thereto and can be appropriately modified without departing from the spirit of the present invention. 
     For example, in the first embodiment, the window  64  is arranged in the anode member  6 , but the present invention is not limited thereto, and when the observation is not conducted with the microscope, the window  64  may not be arranged. 
     Further, in the first embodiment, the anode member body  61  and the window  64  are made of the same material (for example, quartz glass), but the present invention is not limited thereto, and for example, the anode member  61  may be formed with a material different from that of the window  64 . In this case, the window  64  may be formed with a light transmissive material and the anode member body  61  may he formed with an opaque material. 
     Still further, in the first embodiment, the reference electrode layer  63  is arranged on the lower face of the anode member body  61  and the reference electrode conductive layer  44  is arranged on the face, which faces the anode member  6  of the spacer  4 , but the present invention is not limited thereto, and the reference electrode layer  63  and the reference electrode conductive layer  44  may be omitted. 
     Yet further, in the first embodiment, the plating solution supply passage  27  and the plating solution discharge passage  28  are formed in the holding member  2 , but the present invention is not limited thereto, and for example, the plating solution supply passage  27  and the plating solution discharge passage  28  may be formed in the anode member  6 . In addition, one of the the plating solution supply passage  27  and the plating solution discharge passage  28  may be formed in one of the holding member  2  and the anode member  6 , and the other of the plating solution supply passage  27  and the plating liquid discharge passage  28  may be formed in the other of the holding member  2  and the anode member  6 . In a case where exchange (circulation) of the plating solution is not necessary, the plating solution supply passage  27  and the plating solution discharge passage  28  may be omitted. 
     In addition, in the first embodiment, the electrolytic plating is applied by connecting the cathode-side conducting member  7  and the anode-side conducting member  9  to the power supply PW, respectively, but the present invention is not limited thereto, and the cathode-side conducting member  7  and the anode-side conducting member  9  may be connected to the measuring device (not shown) in place of the power supply PW and an electroless plating solution may be supplied as a plating solution to the through portion  45 . This allows the plating apparatus  1  to perform the electroless plating, and allows the measuring device to measure the electric potential of the plated object W and the anode layer  62  during the electroless plating. 
     Next, a sensing device using the above-described plating apparatus will be described with reference to  FIGS. 10 and 11 . 
       FIG. 10  is a plan view of a spacer in the sensing device using the plating apparatus.  FIG. 11  is a bottom view of an anode member in the sensing device using the plating apparatus. 
     Since the sensing device includes the same members as those in the first embodiment except an anode-side conductive layer  43 B of a spacer  4 B and an anode layer  62 B of an anode member  6 B, the anode-side conductive layer  43 B and the anode layer  62 B will be mainly described in the following description, and the other members will not be described. 
     As shown in  FIG. 10 , the spacer  4 B includes a plurality of anode-side conductive layers  43 B (eight in this modification) which are radially arranged on a face which faces the anode member  6 B. Each anode-side conductive layer  43 B is insulated from one another. The outer end  43 Ba of each anode-side conductive layer  43 B is arranged at a position corresponding to the probe insertion hole  66  of the anode member  6 . Further, the inner end  43 Bb of each anode-side conductive layer  43 B is extended to the periphery of the through portion  45 . 
     As shown in  FIG. 11 , the anode member  6 B includes a plurality of anode layers  62 B (eight in this modification) which are radially arranged on a face which faces the spacer  4 B. Each anode layer  62 B is insulated from one another. Each anode layer  62 B is arranged at a position corresponding to the anode-side conductive layer  43 B. The outer end  62 Ba of each anode layer  62 B is extended to the inner periphery of the concave groove  65 , and is in contact with the anode-side conductive layer  43 B once it is assembled. Further, the inner end  62 Bb of each anode layer  62 B is extended to the outer periphery of the window  64  and is exposed from the through portion  45 . 
     The inner ends  62 Bb of anode layers  62 B are modified with eight types of reactive groups, respectively, which are different from one another. The Reactive groups are substances which react to potential substances contained in a reagent supplied to the through portion  45  (see  FIG. 2 ) of the sensing device. An example of the reagent includes liquid containing an electrolyte (e.g. blood, etc.). In addition, an example of reactive group includes a self-assembled monolayer (SAM) with a specific binding receptor. For example, the inner end  62 Bb of each anode layer  62 B is modified with a self-assembled monolayer (SAM) to react with a substance having a metal ion to be sensed or a functional group to be sensed. For example, the inner end  62 Bb of each anode layer  62 B is modified. with aminopropyltriethoxysilane (3-aminopropyltriethoxy silane) to react with Pd ions. 
     The probes P are respectively inserted in the probe insertion holes  66  of the anode member  6 B. The probes P are insulated from one another and are connected to the measuring device (not shown). 
     Such a sensing device can detect a substance contained in the reagent by measuring the change in the electrical potential of the anode layer  62 B with the measuring device at the time of reaction between the reactive group modifying the inner end  62 Bb of the anode layer  62 B and the substances contained in the reagent. For example, the sensing device can be connected to an electrochemical measuring device with the cathode being used as a reference electrode, to allow for checking the variation in the surface electric potential in a two-electrode mode. In addition, it is also possible to measure in a three-electrode mode in which the cathode is set as a counter electrode and one of the eight cathodes is used as the reference electrode. 
     EXPLANATION OF REFERENCES 
       1 : plating apparatus  2 : holding member  27 : plating solution supply passage  28 : plating solution discharge channel  3 : first seal member  4 : spacer  41 : spacer body  42 : cathode-side conductive layer  43 : anode-side conductive layer  44 : reference electrode conductive layer  45 : through portion  5 : second seal member  6 : anode member  61 : anode member body  62 : anode layer  63 : reference electrode layer  64 : window  7 : cathode-side conducting member  8 : insulating member  9 : anode-side conducting member P: probe PW: power supply W: plated object