Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/18—Electroplating using modulated, pulsed or reversing current
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/38—Electroplating: Baths therefor from solutions of copper
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/02—Electroplating of selected surface areas
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
  • H05K3/42—Plated through-holes or plated via connections
  • H05K3/423—Plated through-holes or plated via connections characterised by electroplating method
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/14—Related to the order of processing steps
  • H05K2203/1476—Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning

Definitions

• the present invention relates to a method for plating a small diameter hole with copper.
• the ordinary plating method has a problem in reliability because the plating thickness in the center of the through hole or the bottom of the via becomes extremely thin.
• long-term mounting to increase the thickness of the interior causes additional costs, costs, and the opening is blocked, causing new problems.
• a PPR (Periodic Pulse Reverse) plating method for example, Japanese Patent Application Laid-Open No. 2000-68651
• a method of performing special stirring have been proposed.
• the use of pulses in (ms) units has the following issues.
• the reverse electrolysis current density is required to be 1 to 5 times the positive electrolysis current density. Therefore, a large power supply is required.
• the pulse effect does not reach the center of the substrate, so it is not practical o
• an object of the present invention is to eliminate the need for a high-precision, large-capacity pulsed power supply, thereby reducing equipment costs and, at the same time, providing copper plating in a small-diameter hole, which allows good plating in the small-diameter hole. To provide a way.
• a method for plating a small-diameter hole with copper has a small-diameter hole using a copper sulfate plating solution containing copper sulfate, sulfuric acid, chloride ions, sulfur compounds, and a surfactant.
• copper Me per way method in small holes applying by Ri copper plated to PPR method in diameter halls of the plated material the reverse electrolysis carried out at 0.
• the polarization resistance in the small-diameter hole during positive electrolysis is reduced from that near the entrance of the small-diameter hole. It is characterized by forming a copper-plated film with a uniform thickness in the small-diameter hole while keeping it low.
• the first half reverse electrolysis is performed at a high current density
• the second half reverse electrolysis is performed.
• Two-stage reverse electrolysis which is performed at a lower current density than in the first half, is more suitable.
• the positive electrolysis is performed for several tens to several hundred seconds, and the reverse electrolysis is performed for several seconds to several tens of seconds.
• a copper sulfate plating solution having a low electric resistance and a high copper concentration, with a sulfuric acid concentration of 150 to 250 g Zl and a copper sulfate concentration of 130 to 200 g / 1.
• sulfuric acid concentration 150 to 250 g Zl
• copper sulfate concentration 130 to 200 g / 1.
• Is Raniwa, 2 0 0 g l before and after the sulfuric acid concentration copper sulfate plated solution was 1 5 0 g Z 1 before and after the copper sulfate concentration is suitable in stability.
• the inside of the small diameter hole can be filled with copper plating.
• Figure 1 is a graph showing the relationship between sulfuric acid concentration and plating solution resistance.
• Fig. 2 is a graph showing the relationship between the concentration of sulfuric acid and the concentration of saturated copper sulfate.
• Fig. 3 is a graph showing the relationship between the reverse electrolytic potential and the magnitude of the polarization resistance during positive electrolysis.
• FIG. 4 is a schematic diagram showing a current waveform in one embodiment of the present invention.
• FIG. 5 is a cross-sectional photograph of the through hole of Example 1.
• FIG. 6 is a cross-sectional photograph of the through hole of Example 2.
• FIG. 7 is a cross-sectional photograph of the through hole of Example 3.
• FIG. 8 is a cross-sectional photograph of the through hole of Example 4.
• FIG. 9 is a cross-sectional photograph of the through hole of Comparative Example 1.
• FIG. 10 is a cross-sectional photograph of the through hole of Comparative Example 2.
• composition of the copper sulfate plating solution is as follows: copper sulfate as a copper source, sulfuric acid for conductivity adjustment, chlorine ion (chloride) as a suppressor and a surfactant, and a plating accelerator. Consists of functional sulfur compounds.
• FIG. 1 is a graph showing the relationship between the sulfuric acid concentration, the copper sulfate concentration, and the electrical resistance of the plating solution, and is a comparison when the electrical resistance of 5% sulfuric acid is set to 1.
• FIG. 2 is a graph showing the relationship between the sulfuric acid concentration and the saturated copper sulfate concentration.
• the sulfuric acid concentration is preferably at least 150 g Zl in order to obtain a plating solution having a low electric resistance.
• the sulfuric acid concentration is preferably set to 250 gZl or less.
• the area below the straight line in Fig. 2 is the area that can be used as a copper plating solution.
• sulfuric acid concentration 150 to 250 g Zl
• the copper sulfate concentration is approximately Can be dissolved within the range of 130 to 200 g / l.
• the plating solution can be used stably while maintaining a high copper concentration. It is best to adjust the concentration of copper sulfate before and after and around 150 g. Note that the “before and after” means about ⁇ 5%.
• chloride ion source examples include hydrochloric acid, sodium chloride, potassium chloride, and ammonium chloride. These may be used alone or in combination.
• the amount of chlorine ion added can be used in the range of 10 to 200 mgZl as chloride ion, but is preferably around 3 SmgZ1.
• the sulfur compound is not particularly limited. However, 3-mercapto-1 sodium monopropanesulfonate or 2-sodium sodium mercaptoethanesulfonate, bis- (3-sulfopropyl) disulfido disodium Sulfur compounds such as chromium can be used alone or in combination.
• the surfactant is not particularly limited, a surfactant such as polyethylene glycol and polypropylene glycol can be used alone or in combination.
• the addition amount of the surfactant can be used in the range of several mgZ1 to 1 OgZ1.
• Surfactants when present with chlorine, increase the polarization resistance at the cathode.
• a sulfur compound functions as a promoter by lowering the polarization resistance at the cathode.
• the polarization resistance of the cathode surface depends on the balance between the amounts of these additives adsorbed.
• sulfur compounds are adsorbed on the surface of the adherend, and have a strong effect of lowering the polarization resistance of the adsorbed surface. Therefore, controlling the amount of sulfur compound adsorbed leads to control of polarization resistance.
• the surface of the large-diameter hole to be high and the polarization resistance in the small-diameter hole to be low a plating film with a uniform thickness is formed as a whole.
• reverse electrolysis is performed to remove the sulfur compounds adsorbed on the surface side of the adherend and near the entrance of the small-diameter hole, thereby causing a difference in polarization resistance during positive electrolysis as described above. So that you can hold it.
• the electrical resistance of the plating system is defined as the sum of the polarization resistance and the electrical resistance of the plating solution.
• the electric resistance of the plating solution is made sufficiently smaller than the polarization resistance, the electric resistance of the plating system, and hence the current value inversely proportional thereto, depends on the magnitude of the polarization resistance.
• the electric resistance of the plating solution is suppressed to make it easier to control the polarization resistance.
• the polarization resistance R c is
• R c IV SCE- V.
• FIG. 3 is a graph showing the magnitude of the polarization resistance when reverse electrolysis was performed on the wiring substrate at various potentials for 10 seconds and then positive electrolysis was performed.
• the polarization resistance indicates the polarization resistance on the surface of the object (wiring board).
• the polarization resistance in the small hole is naturally lower than the polarization resistance of the surface.
• the magnitude of the polarization resistance cannot be measured in the small-diameter hole of the object, but the effect of reverse electrolysis is almost ineffective in the small-diameter hole. Except that it hardly occurs. Therefore, the polarization resistance during the positive electrolysis in the small-diameter hole is maintained at a low level, and accordingly, the current flows into the small-diameter hole, and even in the small-diameter hole, the plating positive rotation is improved. .
• the setting of the current density during reverse electrolysis, the reverse electrolysis time, the current density during positive electrolysis, and the electrolysis time may be performed while measuring the plating thickness according to the target adherend.
• FIG. 4 schematically shows a current waveform of PPR plating in the present embodiment.
• Current density during optimal reverse electrolysis 0. 1 ⁇ 0. 5 AZ dm 2, the optimal electrolysis time is 1 to about 1 0 seconds.
• the effect is improved by performing the reverse electrolysis in two stages for the following reasons. That is, in the reverse electrolysis in the first half (first stage), the peeling action on the outside of the through hole is strong, and the peeling action on the inside of the through hole is weak. In the reverse electrolysis in the second half (second stage), the potential for peeling is extremely weak, so that peeling occurs slightly outside the through-hole, but there is almost no peeling action inside, and rather adsorption of sulfur compounds occurs. It is thought to proceed.
• the sulfur compound outside the through-hole is reliably peeled off, and in the second-stage reverse electrolysis, the through-hole is maintained while the peeled state outside the through-hole is maintained by a weak peeling action. Adsorption of sulfur compounds inside occurs. As a result, the difference in the adsorption concentration of the sulfur compound between the outside and the inside of the through hole is larger than in the case where the reverse electrolysis is performed in a single step, and a larger polarization resistance difference is generated.
• the inside of the through-hole may be excessively peeled off, and a sufficient polarization resistance difference between the outside and the inside of the through-hole may not be obtained. Even in such a case, the polarization resistance difference can be reliably obtained by performing the second-stage weak reverse electrolysis.
• the current density during positive electrolysis is about 1.5 AZ dm 2 (this is not particularly limited; it may be determined by considering the throwing power of the plating), and the electrolysis time is preferably about 50 to 200 seconds. .
• SPS refers to bis- (3-sulfopropyl) disodium disodium.
• a 0.8 mm thick wiring board having a through hole with an opening diameter of 0.1 mm was subjected to PPR plating under the following conditions.
• the ratio of film thickness: (film thickness at the center of the through hole / film thickness on the substrate surface) X100 was 91.3%.
• a 0.8 mm thick wiring board having a through hole with an opening diameter of 0.15 mm was subjected to PPR plating under the following conditions.
• the film thickness ratio was 101.4%.
• PPR plating was performed on a 0.8 mm thick wiring board having a through horn with an opening diameter of 0.1 mm under the following conditions.
• Positive electrolysis current density 1.5 AZdm 2 , electrolysis time 120 seconds
• Reverse electrolysis 1 current density 0.5 A / dm 2 , electrolysis time 5 seconds
• Reverse electrolysis 2 current density 0.1 A / dm 2 , electrolysis time 5 seconds
• the film thickness ratio was 109.8%.
• a PPR plating was performed on a 0.8 mm thick wiring board having a through hole with an opening diameter of 0.15 mm under the following conditions.
• Reverse electrolysis 1 current density 0. S AZdm 2 , electrolysis time 5 seconds
• Reverse electrolysis 2 current density 0.1 AZdm 2 , electrolysis time 5 seconds
• the film thickness ratio was 10.8%.
• DC plating was performed on a wiring board having a through hole with an opening diameter of 0.1 mm and a thickness of 0.8 mm under the following conditions.
• the film thickness ratio was 53.9%.
• DC plating was performed on a wiring board having a through hole with an opening diameter of 0.15 mm and a thickness of 0.8 mm under the following conditions.
• FIGS. 5 to 10 are cross-sectional photographs (75 ⁇ magnification) of the through holes.
• FIGS. 5, 6, 7, and 8 show the through holes of Examples 1, 2, 3, and 4, respectively, and FIGS. Indicates through holes of Comparative Examples 1 and 2, respectively.
• the film thickness ratio slowing power
• Example 1 to 4 the film thickness ratio (slowing power) was approximately 100%, and a copper-coated film having a uniform thickness was formed on the surface and in the small-diameter holes. Can be.
• the plating thickness inside the small-diameter hole became thicker than the plating thickness on the surface.
• the inside of the small-diameter hole can be filled by plating.
• plating of through holes has been described as an example, but plating in micro blind vias can be performed in the same manner.
• a long-period PPR plating method can be performed in a unit of second, and a high-precision, large-capacity pulse current is not required, so that equipment cost can be reduced.
• the current for plating on the front and back of the substrate can be easily synchronized, and wiring that takes into account the loss due to inductance becomes unnecessary.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Electroplating Methods And Accessories (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Printing Elements For Providing Electric Connections Between Printed Circuits (AREA)

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Publications (1)

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Cited By (7)

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Citations (7)

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• 2002
  • 2002-10-09 CN CNB028031326A patent/CN1283848C/zh not_active Expired - Fee Related
  • 2002-10-09 KR KR10-2003-7006763A patent/KR20040045390A/ko not_active Application Discontinuation
  • 2002-10-09 JP JP2003536491A patent/JP4148895B2/ja not_active Expired - Fee Related
  • 2002-10-09 WO PCT/JP2002/010483 patent/WO2003033775A1/ja active Application Filing
  • 2002-10-09 US US10/416,304 patent/US20040011654A1/en not_active Abandoned
  • 2002-10-15 TW TW091123729A patent/TW561808B/zh not_active IP Right Cessation

Patent Citations (7)

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