Abstract:
An object of the present invention is to solve a problem in filling of a blind via or a through-hole with a conventionally used plating solution for tin or tin alloy plating where the filling itself cannot be achieved well, or even if the filling itself could be achieved, it takes an extremely long time. The electroplating solution for tin or tin alloy capable of solving the problem includes the following components (a) and (b):
       (a) a carboxyl group-containing compound, and   (b) a carbonyl group-containing compound,   a content of the component (a) being 1.3 g/L or more, and a content of the component (b) being 0.3 g/L or more.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electroplating solution for tin or tin alloy and a method for filling a blind via or a through-hole using the same, and a method for manufacturing an electronic circuit board. 
       BACKGROUND ART 
       [0002]    Up to date, copper plating has been used in three-dimensional packaging of semiconductor or a filling process of a blind via or a through-hole in a printed wiring board, and a solder ball or a tin alloy has been used in a packaging process. 
         [0003]    However, since different metal species are used in the filling process and the packaging process, there was a problem of complexity in the conventional processes. 
         [0004]    Then, if in the filling process of a blind via or a through-hole, tin or a tin alloy could be used in the same manner as in the packaging process, the packaging process could be omitted. Actually, a technique for applying tin or a tin alloy in the filling process of a blind via or a through-hole is reported for the time being (see PTL 1). 
       CITATION LIST 
     Patent Literature 
       [0005]    PTL 1: JP-A-2012-87393 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    However, in using a conventionally reported plating solution for tin or tin alloy plating to fill a blind via or a through-hole, the problem was that the filling itself cannot be actually achieved well; or that even if the filling itself could be achieved, it takes an extremely long time. 
       Solution to Problem 
       [0007]    In order to solve the foregoing problem, the present inventors made extensive and intensive investigations. As a result, it has been found that by including a specified concentration of a specified compound in a conventionally known plating solution for tin or tin alloy plating, a blind via or a through-hole can be highly reliably filled in a short time, leading to accomplishment of the present invention. 
         [0008]    Specifically, the present invention is concerned with an electroplating solution for tin or tin alloy containing the following components (a) and (b): 
         [0009]    (a) a carboxyl group-containing compound, and 
         [0010]    (b) a carbonyl group-containing compound, 
         [0011]    a content of the component (a) being 1.3 g/L or more, and a content of the component (b) being 0.3 g/L or more. 
         [0012]    In addition, the present invention is concerned with a plating filling method of a blind via or a through-hole including subjecting a material having a blind via or a through-hole to electroplating with the above-described electroplating solution for tin or tin alloy. 
         [0013]    Furthermore, the present invention is concerned with a method for manufacturing an electronic circuit board including a process of subjecting a board having a blind via or a through-hole to plating filling, the method including carrying out the plating filling by the above-described plating filling method of a blind via or a through-hole. 
       Advantageous Effects of Invention 
       [0014]    By subjecting a material having a blind via or a through-hole to electroplating with the electroplating solution for tin or tin alloy of the present invention, the blind via or through-hole can be highly reliably filled in a short time. 
         [0015]    In addition, the electroplating solution for tin or tin alloy of the present invention can be utilized for three-dimensional packaging of semiconductor or a filling process of a blind via or a through-hole in a printed wiring board, or the formation of a through-silicon via. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  shows a photograph of a cross section of a board after electroplating in Example 2 ((a) shows a board electroplated with an electroplating solution of Comparative Product 1 at 0.075 A/dm 2  for 15 minutes, and (b) shows a board electroplated with an electroplating solution of Example Product 1 at 0.075 A/dm 2  for 20 minutes). 
           [0017]      FIG. 2  shows a photograph of a cross section of a board after electroplating in Example 3 ((a) to (d) show boards electroplated with an electroplating solution of Comparative Product 2 at 0.05 A/dm 2  after a lapse of 15 minutes, 30 minutes, 60 minutes, and 90 minutes, respectively). 
           [0018]      FIG. 3  shows a photograph of a cross section of a board after electroplating in Example 3 ((a) to (e) show boards electroplated with an electroplating solution of Example Product 1 at 0.05 A/dm 2  after a lapse of 15 minutes, 30 minutes, 60 minutes, 90 minutes, and 120 minutes, respectively). 
           [0019]      FIG. 4  shows a photograph of a cross section of a board after electroplating in Example 6 ((a) to (c) show boards electroplated with an electroplating solution of Example Product 2 at 1 .5 A/dm 2  after a lapse of 15 minutes, 25 minutes, and 35 minutes, respectively). 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0020]    The carboxyl group-containing compound as the component (a) to be contained in the electroplating solution for tin or tin alloy of the present invention (hereinafter referred to “plating solution of the present invention”) is not particularly limited so long as it is a compound having a carboxyl group; however, examples thereof include methacrylic acid, acrylic acid, crotonic acid, propylene-1,2-dicarboxylic acid, ethacrylic acid, methyl acrylate, methyl methacrylate, and the like. Of these, methacrylic acid and acrylic acid are preferred. In addition, these carboxyl group-containing compounds can be used singly or in combination of two kinds thereof. 
         [0021]    A content of the carboxyl group-containing compound as the component (a) in the plating solution of the present invention is 1.3 g/L or more, and preferably 1.3 to 2.5 g/L. 
         [0022]    The carbonyl group-containing compound as the component (b) to be contained in the plating solution of the present invention is not particularly limited so long as it is a compound having a carbonyl group; however, examples thereof include benzalacetone, naphthaldehyde, chlorobenzaldehyde, phthalaldehyde, salicylaldehyde, chloronaphthaldehyde, methoxybenzaldehyde, vanillin, and the like. Of these, benzalacetone, naphthaldehyde, and chlorobenzaldehyde are preferred. In addition, these carbonyl group-containing compounds can be used singly or in combination of two kinds thereof. The carbonyl group-containing compound is contained in the plating solution of the present invention, preferably with a solvent, such as methanol, isopropyl alcohol, and the like. 
         [0023]    A content of the carbonyl group-containing compound as the component (b) in the plating solution of the present invention is 0.3 g/L or more, and preferably 0.3 to 1.0 g/L. 
         [0024]    In the plating solution of the present invention, though a molar ratio of the component (a) to the component (b) is not particularly limited, it is preferably 10 or less, and more preferably 2 to 9. 
         [0025]    The conventionally known electroplating solution for tin or tin alloy serving as a base of the plating solution of the present invention is not particularly limited. However, examples thereof include those containing a tin ion; a metal ion for alloys, such as a silver ion, a gold ion, a copper ion, a lead ion, an antimony ion, an indium ion, a bismuth ion, and the like; and an acid capable of rendering a bath acidic and stabilizing it, such as sulfuric acid, methanesulfonic acid, fluoroboric acid, phenolsulfonic acid, sulfamic acid, pyrophosphoric acid, and the like. Examples of a more specific electroplating bath for tin or tin alloy include a sulfuric acid bath, a methanesulfonic acid bath, a fluoroboric acid bath, and the like. Of these, a sulfuric acid bath and a methanesulfonic acid bath are preferred. 
         [0026]    In the plating solution of the present invention, a known nonionic, cationic, or anionic surfactant, an antioxidant, such as catechol, resorcinol, catecholsulfonic acid, etc., and the like may be further added to the conventionally known electroplating solution for tin or tin alloy. 
         [0027]    Preferred embodiments of the plating solution of the present invention are hereunder described. 
       &lt;Electroplating Solution for Tin&gt; 
       [0028]    Stannous methanesulfonate (as tin) : 25 to 150 g/L, preferably 70 to 125 g/L 
         [0029]    Methanesulfonic acid: 10 to 180 g/L, preferably 15 to 120 g/L 
         [0030]    Polyoxyethylene laurylamine: 0.1 to 8 g/L, preferably 3 to 6 g/L 
         [0031]    Catechol: 0.1 to 5 g/L, preferably 0.5 to 2 g/L 
         [0032]    Methacrylic acid: 0.2 to 4 g/L, preferably 1.3 to 2.5 g/L 
         [0033]    1-Naphthaldehyde: 0.05 to 1.5 g/L, preferably 0.3 to 1.0 g/L 
         [0034]    Methanol: 0.7 to 25 g/L, preferably 3.5 to 17 g/L 
       &lt;Electroplating Solution for Tin Alloy&gt; 
       [0035]    Stannous methanesulfonate (as tin) : 25 to 150 g/L, preferably 70 to 125 g/L 
         [0036]    Lead methanesulfonate (as lead): 0.1 to 50 g/L, preferably 1 to 30 g/L 
         [0037]    Methanesulfonic acid: 10 to 180 g/L, preferably 15 to 120 g/L 
         [0038]    Polyoxyethylene laurylamine: 0.1 to 8 g/L, preferably 3 to 6 g/L 
         [0039]    Catechol: 0.1 to 5 g/L, preferably 0.5 to 2 g/L 
         [0040]    Methacrylic acid: 0.2 to 4 g/L, preferably 1.3 to 2.5 g/L 
         [0041]    1-Naphthaldehyde: 0.05 to 1.5 g/L, preferably 0.3 to 1.0 g/L 
         [0042]    Methanol: 0.7 to 25 g/L, preferably 3.5 to 17 g/L 
         [0043]    The plating solution of the present invention is able to undergo electroplating on a material to be plated by a conventionally known method. The method of the electroplating with the plating solution of the present invention is not particularly limited. For example, the material to be plated is subjected to a pretreatment, such as alkaline degreasing, a hydrophilization treatment, acid activation, etc., and the resultant is dipped in the plating solution of the present invention. 
         [0044]    Conditions of the electroplating with the plating solution of the present invention is not particularly limited, and usual conditions for electroplating of tin or a tin alloy may be adopted. For example, the electroplating may be performed by using tin as an anode at a bath temperature of 10 to 40° C. at a cathode electrode current density of 0.2 to 3 A/dm 2 . In addition, it is preferred to perform stirring by using a paddle or the like during the electroplating. 
         [0045]    The material to be plated, which can be subjected to electroplating with the plating solution of the present invention, is not particularly limited. Examples thereof include those having a surface made of a metal, such as copper, nickel, brass, etc., a resin, such as ABS, a polyimide, an epoxy resin, etc., or the like. 
         [0046]    The plating solution of the present invention can be applied to electroplating on the above-described usual material to be plated. Nevertheless, it is particularly preferred to use the plating solution of the present invention for subjecting a material having a blind via or a through-hole to electroplating, thereby filling the blind via or through-hole with tin or a tin alloy. 
         [0047]    In the case of using for filling a blind via, a molar ratio of the component (a) to the component (b) in the plating solution of the present invention is set to 10 or less, and preferably 2 to 9. In the case of using for filling a through-hole, a molar ratio of the component (a) to the component (b) in the plating solution of the present invention is set to 10 or less, and preferably 3.5 to 10. 
         [0048]    In the case of filling a blind via or a through-hole with tin or a tin alloy by using the plating solution of the present invention, conditions of the electroplating are not particularly limited. For example, the electroplating may be performed by using tin as an anode at a bath temperature of 10 to 40° C. at a cathode electrode current density of 0.01 to 2.5 A/dm 2 . In addition, in order to shorten a plating time, the current density during the electroplating may be made relatively higher than that at the start of electroplating. A method of making the current density during the electroplating relatively higher than that at the start of electroplating is not particularly limited. For example, the current density during the electroplating may be increased in a stepwise fashion after a lapse of a prescribed time from the start of electroplating, or in a linear fashion from the start of electroplating. 
         [0049]    The plating solution of the present invention capable of filling a blind via or a through-hole with tin or a tin alloy as described above can be utilized for a filling process including a process of performing plating filling on a board having a blind via or a through-hole, for example, three-dimensional packaging of semiconductor or a filling process of a via or a through-hole in a printed wiring board, and a method for manufacturing an electronic circuit board, such as the formation of a through-silicon via, etc. 
       Examples 
       [0050]    The present invention is hereunder described in detail by reference to Examples, but the invention is not limited to these Examples at all. 
       Example 1 
     Preparation of Electroplating Solution for Tin 
       [0051]    An electroplating solution for tin having the following composition was prepared by mixing Components 1 to 5 and 7 and then mixing Component 6. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 All of the units are g/L 
               
             
          
           
               
                   
                   
                 Compar- 
                   
                 Compar- 
               
               
                   
                   
                 ative 
                 Example 
                 ative 
               
               
                   
                 Component 
                 Product 1 
                 Product 1 
                 Product 2 
               
               
                   
                   
               
             
          
           
               
                 1 
                 Tin * 1   
                 100 
                 100 
                 100 
               
               
                 2 
                 Methanesulfonic acid 
                 17 
                 17 
                 17 
               
               
                 3 
                 Polyoxyethylene laurylamine 
                 4 
                 4 
                 4 
               
               
                 4 
                 Catechol 
                 1 
                 1 
                 1 
               
               
                 5 
                 Methacrylic acid 
                 2.0 
                 2.0 
                 0.8 
               
               
                 6 
                 1-Naphthaldehyde 
                 0.1 
                 0.75 
                 0.75 
               
               
                 7 
                 Methanol 
                 1.7 
                 12.6 
                 12.6 
               
               
                   
               
               
                 * 1  Amount of tin in tin sulfonate 
               
             
          
         
       
     
       Example 2 
     Filling of Blind Via by Tin Electroplating 
       [0052]    A silicon wafer board having a blind via whose aspect ratio is 6 (10φ×60D) was washed with water and subjected to a pretreatment. The pretreated board was dipped in each of the electroplating solutions for tin as prepared in Example 1 (Comparative Product 1 and Example Product 1) for one minute and subjected to electroplating at a current density of 0.075 A/dm 2  for a prescribed time (15 minutes for Comparative Product 1 and 20 minutes for Example Product 1) . A filled state of the via was observed from a cross section of the board after electroplating ( FIG. 1 ). 
         [0053]    In Comparative Product 1, deposition was not confirmed and a void was observed in the via bottom portion, whereas in Example Product 1, preferential deposition from the via bottom portion was confirmed. 
       Example 3 
     Filling of Blind Via by Tin Electroplating 
       [0054]    After pretreatment of the same board as that used in Example 2, the resulting board was dipped in each of the electroplating solutions for tin as prepared in Example 1 (Example Product 1 and Comparative Product 2) and subjected to electroplating at a current density of 0.05 A/dm 2  for a prescribed time (15 minutes, 30 minutes, 60 minutes, 90 minutes, and 120 minutes (only in Example Product 1), respectively). A filled state of the via was observed from a cross section of the board after electroplating ( FIGS. 2 and 3 ). 
         [0055]    In Comparative Product 2, filling within the via did not proceed even after plating for 90 minutes, whereas in Example Product 1, the deposition amount increased with a lapse of the plating time and the filling could be achieved to an extent of almost 100% in plating for 120 minutes. 
       Example 4 
     Filling of Blind Via by Tin Electroplating 
       [0056]    After pretreatment of the same board as that used in Example 2, the resulting board was dipped in the electroplating solution for tin as prepared in Example 1 (Example Product 1) and subjected to electroplating first at a current density of 0.075 A/dm 2  for 20 minutes, then at 0.15 A/dm 2  for 10 minutes, and finally at 0.3 A/dm 2  for 10 minutes. 
         [0057]    The electroplating achieved complete filling of the blind via in 40 minutes. By increasing the current density in a stepwise fashion, the filling time of the blind via was shortened by about 65% as compared with the case of setting the current density at a fixed level. 
       Example 5 
     Preparation of Electroplating Solution for Tin 
       [0058]    An electroplating solution for tin having the following composition was prepared by mixing Components 1 to 5 and 7 and then mixing Component 6. 
         [0000]    
       
         
               
               
             
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 All of the units are g/L 
                   
               
             
          
           
               
                   
                 Example 
               
               
                   
                 Product 2 
               
               
                   
                   
               
             
          
           
               
                 1 
                 Tin * 1   
                 100 
               
               
                 2 
                 Methanesulfonic acid 
                 100 
               
               
                 3 
                 Polyoxyethylene laurylamine 
                 4 
               
               
                 4 
                 Catechol 
                 1 
               
               
                 5 
                 Methacrylic acid 
                 2.0 
               
               
                 6 
                 1-Naphthaldehyde 
                 0.5 
               
               
                 7 
                 Methanol 
                 8.4 
               
               
                   
               
               
                 * 1  Amount of tin in tin sulfonate 
               
             
          
         
       
     
       Example 6 
     Filling of Via by Tin Electroplating 
       [0059]    A printed wiring board having a blind via whose aspect ratio is 0.57 (70φ×40D) was subjected to an alkaline degreasing treatment at 40° C. for one minute and then subjected to a pretreatment by an acid activation treatment at room temperature for 10 seconds. The pretreated board was dipped in the electroplating solution for tin as prepared in Example 5 (Example Product 2) and subjected to electroplating at a current density of 1.5 A/dm 2  for a prescribed time (15 minutes, 25 minutes, and 35 minutes, respectively) . A filled state of the via was observed from a cross section of the board after electroplating ( FIG. 4 ). 
         [0060]    Deposition from the bottom portion of the via was confirmed after the start of plating; the inside of the via was substantially filled in 25 minutes; and complete filling of the via and deposition on the surface were confirmed in 35 minutes. In addition, it was also confirmed that a thickness of the deposited film on the surface after filling the via can be arbitrarily controlled. 
       Example 7 
     Preparation of Electroplating Solution for Tin 
       [0061]    An electroplating solution for tin having the following composition was prepared by mixing Components 1 to 5 and 8 and then mixing Component 6 or 7. 
         [0000]    
       
         
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 All of the units are g/L 
                   
               
             
          
           
               
                   
                 Example 
                 Example 
               
               
                   
                 Product 3 
                 Product 4 
               
               
                   
                   
               
             
          
           
               
                 1 
                 Tin * 1   
                 100 
                 100 
               
               
                 2 
                 Methanesulfonic acid 
                 17 
                 17 
               
               
                 3 
                 Polyoxyethylene laurylamine 
                 4 
                 4 
               
               
                 4 
                 Catechol 
                 1 
                 1 
               
               
                 5 
                 Methacrylic acid 
                 1.5 
                 1.5 
               
               
                 6 
                 1-Naphthaldehyde 
                 1.0 
                 — 
               
               
                 7 
                 Benzaldehyde 
                 — 
                 1.0 
               
               
                 8 
                 Methanol 
                 16.8 
                 16.8 
               
               
                   
               
               
                 * 1  Amount of tin in tin sulfonate 
               
             
          
         
       
     
       Example 8 
     Filling of Via by Tin Electroplating 
       [0062]    After pretreatment of a blind silicon wafer board having a blind via whose aspect ratio is 5 (20φ×100D) , the resulting board was dipped in each of the electroplating solutions for tin as prepared in Example 7 (Example Product 3 and Example Product 4) and subjected to electroplating at a current density of 0.2 A/dm 2  until the blind via was filled. 
         [0063]    By the electroplating with the electroplating solution of Example Product 3, the via was completely filled in 100 minutes. By the electroplating with the electroplating solution of Example Product 4, the via was completely filled in 110 minutes. 
       Example 9 
     Preparation of Electroplating Solution for Tin Alloy: 
       [0064]    An electroplating solution for tin alloy having the following composition was prepared by mixing Components 1 to 6 and 8 and then mixing Component 7. 
         [0000]    
       
         
               
               
             
               
               
             
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 All of the units are g/L 
                   
               
             
          
           
               
                   
                 Example 
               
               
                   
                 Product 5 
               
               
                   
                   
               
             
          
           
               
                 1 
                 Tin * 1   
                 100 
               
               
                 2 
                 Lead * 2   
                 10 
               
               
                 3 
                 Methanesulfonic acid 
                 100 
               
               
                 4 
                 Polyoxyethylene laurylamine 
                 4 
               
               
                 5 
                 Catechol 
                 1 
               
               
                 6 
                 Methacrylic acid 
                 2.0 
               
               
                 7 
                 1-Naphthaldehyde 
                 0.5 
               
               
                 8 
                 Methanol 
                 8.4 
               
               
                   
               
               
                 * 1  Amount of tin in tin sulfonate 
               
               
                 * 2  Amount of lead in lead methanesulfonate 
               
             
          
         
       
     
       Example 10 
     Filling of Blind Via by Tin Alloy Electroplating 
       [0065]    After pretreatment of the same board as that used in Example 6, the resulting board was dipped in the electroplating solution for tin alloy as prepared in Example 9 (Example Product 5) and subjected to electroplating at a current density of 1.5 A/dm 2  for 30 minutes. 
         [0066]    The electroplating achieved complete filling of the blind via. Incidentally, as a result of fluorescent X-ray analysis of the metal filled in the blind via, it was found to be an alloy made of 87% of tin and 13% of lead. 
       INDUSTRIAL APPLICABILITY 
       [0067]    According to the present invention, a blind via or a through-hole can be filled with tin or a tin alloy. For that reason, the present invention can be utilized for three-dimensional packaging of semiconductor or a filling process of a blind via or a through-hole in a printed wiring board, or the formation of a through-silicon via.