Classifications

• • 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

Definitions

• the present invention relates to a method for the electrolytic deposition of a mat or half-glossy copper layer from an acid electrolyte.
• Acid copper electrolytes are used for the surface coating of substrates in a manifold manner, in order to form a functional or decorative coating on the substrate surfaces.
• the metallization method to be used as well as the electrolyte to be used depends on the type and nature of the substrate to be metallized. Thus, both metallic and non conductive substrates can be provided with corresponding surface layers.
• the electrolyte and method to be used have to meet special requirements with respect to the stability and the deposition velocity.
• the above mentioned products are for example often metallized in high-speed pull-through devices. They are commonly referred to as “stretch products” because they are stretched or bended during service and therefore the coating must be ductile and well adhered.
• stretch products In order to obtain a sufficient metallization of the substrate surfaces in spite of a short contact time (high throughput rate), one has to plate up with high current densities.
• the invention is directed to a process for the electrolytic deposition of a mat or half-glossy copper layer from an acidic electrolytic comprising contacting an elongate substrate selected from the group consisting of wire, tube, band, and ribbon with an aqueous acidic electrolytic solution comprising copper ions and an alkyl sulfonic acid by pulling the substrate through the electrolytic solution wherein a first segment of the substrate is in contact with the aqueous acidic electrolytic solution while a second segment of the substrate is not in contact with the aqueous acidic electrolytic solution; and passing a current at a density of at least about 10 A/dm 2 between an anode in contact with said electrolytic solution and a cathode comprising said substrate.
• the invention is directed to an electrolyte or combination of electrolytes for use in preparation of electrolytic solutions that function as plating baths for electrodeposition of copper, said electrolyte or combination of electrolytes comprising, on an anhydrous basis, between about 18 wt. % and about 40 wt. % copper and between about 22 wt. % and about 58 wt. % methane sulfonic acid.
• the invention is also directed to a process for the electrolytic deposition of a mat or half-glossy copper layer on a substrate comprising reducing copper ions from an acid electrolytic solution onto said substrate at a current efficiency of at least about 75% and a current density between approximately 40 and 100 A/dm 2 as determined with reference to the area of the substrate being plated.
• the substrate is contacted with an aqueous acidic electrolytic solution comprising copper ions and an alkylsulfonic acid.
• the solution is also in contact with an anode, and a current is passed through the solution at a density of at least about 10 A/dm 2 between the anode and a cathode comprising the substrate to be plated.
• the invention has special applicability to a process in which the substrate is moved relative to the electrolytic solution as current is passed between the anode and the cathode, and more particularly to the plating of high-speed pull-through products such as wires, tubes, tape, connector material and metallized plastic wires.
• pull-through refers to a process in which the substrate is a relatively elongate continuous substrate which is continuously or intermittently pulled in its axial or tangential direction through the electrolytic solution as current is passed between the moving substrate and the anode in contact with the electrolytic solution, i.e., the plating bath. At any one moment, a segment of the substrate is immersed in the electrolyte and other segments of the substrate are not immersed in the electrolyte.
• incorporation of an alkyl sulfonic acid permits plating at relatively high current densities which are required for plating at high speeds.
• incorporation of a surfactant may further contribute to achievement of high current density without sacrifice of coating quality.
• the specific bath components facilitate current densities of at least about 10 A/dm2 (ASD), such as between approximately 10 and 100 ASD.
• the plating baths and processes of the invention are capable of current densities of greater than 20 ASD, such as between about 20 and about 100 ASD.
• high productivity is achievable at current densities in the range above 40 A/dm 2 , and more particularly at current densities above about 50 A/dm 2 , above about 60 A/dm 2 , above about 70 A/dm2, or above about 80 A/dm 2 .
• the process of the invention may provide current densities as much as two to three times higher than those conventionally practiced on comparable substrates.
• the invention involves plating speeds suitable for substrate travel rates of at least about 0.5 meter/second.
• the pull rates are more typically at least about 0.8 meter/sec., preferably at least about 5 meters/second, and most typically between about 5 and about 20 meters/second.
• the pull rate is most typically between about 2 and about 50 meters/minute.
• high productivity is achieved at travel velocities in the range above about 10 meters/second, more particularly above about 12 meters/second, 14 meters per second, 16 meters/second, or 18 meters/second.
• productivity is ultimately determined by the dwell time in the bath rather than the relative velocity of substrate to bath.
• the bath itself may be subject to some movement relative to the cell in which the operation is conducted, e.g., in a direction partially or entirely parallel to the travel of the substrate.
• the velocity of the moving substrate can be expressed with reference to a plating vessel wherein the wire is submerged within the plating bath and current is applied, or more specifically relative to a a fixed locus of points within the vessel that is parallel or tangential to the path on which the substrate passes through the vessel.
• the aforesaid minimum velocity and range of velocity are applicable by this measurement as well.
• the typical submerged length of substrate subjected to electrolytic deposition conditions at the aforesaid current densities within the bath is typically between about 60 and about 300 meters.
• deposition velocities are typically in the range of about 4 to about 22 microns per minute for wire, and between about 1 and about 7 microns per minute for other pull through products.
• Residence time is typically in the range between about 5 and about 25 seconds in the region of the bath wherein current is passed between the anode and cathode.
• productivity of the process is a direct function of the residence time and thus of the length of substrate within the region of the bath wherein current is passed from anode to substrate.
• the maximum submerged length of the substrate may be limited by the current density distribution within the plating bath, by the electrical resistance of the substrate, or by the elongation of the substrate as produced by the tensile stress that is produced by the substrate's own weight (less buoyancy).
• the method is preferably carried out in a temperature range comprised between 22 and 60° C; for example, between 45 and 55° C. If the temperature is too high or too low, the plating may not be uniform.
• These process conditions are suitable for the deposition of copper layers having a sufficient thickness and solidity in high-speed pull-through devices such as plastic tubing which had previously received a thin Cu coating by an immersion/electroless Cu process, and the present invention is applied to increase the Cu thickness.
• the thickness of copper plated in accordance with this invention may range up to about 50 microns.
• the aims of the invention are achieved by use of a copper bearing electrolytic solution, which contains an alkyl sulfonic acid.
• the alkyl sulfonic acid is preferably methane sulfonic acid.
• the alkyl sulfonic acid is preferably included in a concentration of at least about 50 ml/L, typically 50 to about 130 ml/L. For some applications, the concentration is at least about 70 ml/L, at least about 80 ml/L or at least about 90 ml/L.
• the alkyl sulfonic acid concentration is preferably less than about 110 ml/L, such as about 90 ml/L.
• the purpose of the alkyl sulfonic acid i.e., the manner in which it is believed to function to permit substantially increased current densities, is that the alkyl sulfonic acid is compatible with a much higher Cu ion concentration than is sulfuric and other typical acids. If the alkyl sulfonic acid content is too low, there is a conductivity deficit. If the alkyl sulfonic acid content is too high, there can be burning with high current densities. Also, if too high, evolution of hydrogen can increase above acceptable levels.
• the weight of solid alkyl sulfonic acid to be introduced can be determined from the volumes specified above, applying the appropriate density, which in the case of methane sulfonic acid is approximately 1.48 at 18° C. Densities of other alkyl sulfonic acids are available from the literature, and the above expressed volumetric ratios can readily be converted to weight ratios by anyone skilled in the art.
• the acid component of the electrolyte consists essentially of methane sulfonic acid, in that sulfuric acid and other acid components are substantially excluded.
• the electrolytic solution comprises a source of copper ions which is copper in form of sulphates, nitrates, halogenides, or carboxylates thereof.
• a preferred copper compound source of copper ions is Cu(HSO 3 CH 3 ) 2 .
• the copper source is preferably included in a concentration which will provide copper ions in a concentration of at least about 40 g/L, typically between about 40 and about 90 g/L.
• the copper ion concentration is preferably at least about 75 g/L. In certain embodiments, this concentration is less than about 90 g/L, such as about 75 g/L.
• the electrolytic solution also comprises a sufficient quantity of a nonionic surfactant, for example a surfactant derived from an alkylene oxide such as ethylene oxide.
• a nonionic surfactant for example a surfactant derived from an alkylene oxide such as ethylene oxide.
• the nonionic surfactant comprises an alkoxylated aromatic such as, for example, 2-naptholethoxylate[2-(2-naphthyloxy)-ethanol], such as is available from BASF under the trade name Lugalvan.
• the ethoxylate is normally included in a concentration of, for example, at least about 10 g/L.
• the ethoxylate is preferably in a concentration which is less than about 30 g/L, to assure deposition of a satisfactorily uniform copper plating.
• the nonionic surfactant concentration may not exceed, e.g., about 10 g/L.
• the primary criteria are bath compatibility and whether it functions as a basic inhibitor of Cu deposition.
• the electrolytic solution comprises a sufficient quantity of an aromatic condensation polymer comprising sulfonated aromatic repeating units such as naphthalene sulfonic acid for the purpose of further facilitating the achievement of high current densities.
• an aromatic condensation polymer comprising sulfonated aromatic repeating units such as naphthalene sulfonic acid for the purpose of further facilitating the achievement of high current densities.
• naphthalene condensation product has the general formula I:
• n is an integer number greater than 1.
• the polymer may be prepared by condensation of naphthol with formaldehyde which generates methylene linking groups, or by condensation of ⁇ -napthol or 1-naphtol-4-sulfonic acid with a dicarboxylic acid such as maleic anhydride.
• a suitable such condensation product is available from BASF.
• the naphthalene condensation product is included in a concentration of at least about 0.001 g/L.
• the naphthalene condensation product is in a concentration which is less than about 1 g/L, for example, such as about 0.1 g/L. If the naphthalene condensation content is too high, the deposit can be uneven.
• the primary criterion to be considered is stability in high current density baths.
• the electrolytic solution also contains halogenide ions, such as chloride, bromide, and iodide.
• halogenide ions such as chloride, bromide, and iodide.
• the purpose of the halogenide ions is to enhance the appearance of the coating.
• the halide ion concentration is at least about 40 mg/L.
• the halogenide ions are preferably in a concentration which is, for example, less than about 100 mg/L, such as about 50 mg/L. If the halogenide content is too low or too high, the deposition may not be uniform.
• the electrolytic solution can additionally comprise typical process materials, such as leveling agents and surface-active agents, also combinations thereof, as they are known in literature.
• the invention is further directed to an electrolyte or combination of electrolytes for use in preparation of electrolytic solutions that function as plating baths for electrodeposition of copper.
• Such electrolyte or combination of electrolyte comprises between 18 wt. % and about 40 wt. % copper and between about 22 wt. % and about 58 wt. % methane sulfonic acid.
• such electrolyte or combination further comprises between about 2 wt. % and about 13 wt. % of a naphtholethoxylate anion surfactant, and more preferably further comprises a condensation polymer of naphthol bearing ring-substituted sulfonic acid groups.
• the electrolyte or combination may further comprise between about 0.02 wt. % and about 0.04 wt. % halide ions.
• the electrolyte can be supplied as a pre-packaged combination which can be directly introduced into water to provide an electrolytic solution which may serve as the plating bath for use in the method of the invention.
• the combination may be provided as a supply or kit comprising separately packaged components, or with some components pre-mixed but others separately packaged.
• composition of an aqueous electrolytic solution for the deposition of copper in a pull-through device copper: 40 to 90 g/l, preferably 75 g/l methane sulfonic acid: 50 to 130 ml/l, preferably 90 ml/l halogenide ions: 40 to 100 mg/l, preferably 50 mg/l 2-naphtolethoxylate: 5 to 30 g/l, preferably 10 g/l Naphthalene condensation: 0.001 to 1 g/l, preferably 0.1 g/l
• the electrolyte comprises chloride as halogenide ion.
• a 1 mm diameter wire is plated with copper in a pull-through continuous electrolytic coating under ambient temperature conditions at a line velocity of 600 m/min., a current density of 80 A/dm 2 , and a residence time of 10 seconds.
• Submerged length of the wire is 100 meters.
• a uniform copper coating having a thickness of 3 ⁇ m is obtained on the wire.
• Example 2 shows typical process conditions for the method according to the invention.
• a 1 mm diameter wire is electroplated under the process conditions described below for the deposition of mat or half-glossy copper layers on a substrate from an electrolyte according to the invention:
• Substrate Brass Temperature: 25° C.
• Current density 10 A/dm 2
• Pull-through velocity 50 m/min
• Layer thickness of the deposited copper layer 5 ⁇ m
• a 1 mm diameter wire substrate is coated in a pull through device under the conditions of Example 2 in a methane sulfonic acid (MSA) bath and a comparative sulfuric acid bath.
• the baths have the following compositions:
• Example 2 Using the same bath compositions described in Example 3, laboratory plating experiments were conducted under the temperature and current density conditions generally described in Example 2. Comparisons were made of the elongation characteristics of the wire coated in the bath of the invention vs. that coated in the conventional sufuric acid bath. In this context, “elongation” means the maximum stretching of the wire that can be tolerated without damage to the copper coating.

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• Electroplating And Plating Baths Therefor (AREA)
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• 2004
  • 2004-08-28 DE DE102004041701A patent/DE102004041701A1/de not_active Withdrawn
• 2005
  • 2005-08-23 ES ES05018241T patent/ES2402688T3/es active Active
  • 2005-08-23 EP EP05018241A patent/EP1630258B1/de active Active
  • 2005-08-24 JP JP2005243009A patent/JP4283256B2/ja active Active
  • 2005-08-26 CN CN200510092292.7A patent/CN1740399A/zh active Pending
  • 2005-08-29 US US11/214,421 patent/US20060049058A1/en not_active Abandoned

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