Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/38—Coating with copper
  • C23C18/40—Coating with copper using reducing agents
  • C23C18/405—Formaldehyde
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/1601—Process or apparatus
  • C23C18/1633—Process of electroless plating
  • C23C18/1635—Composition of the substrate
  • C23C18/1639—Substrates other than metallic, e.g. inorganic or organic or non-conductive
  • C23C18/1641—Organic substrates, e.g. resin, plastic
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/2006—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30
  • C23C18/2026—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30 by radiant energy
  • C23C18/204—Radiation, e.g. UV, laser
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/38—Coating with copper
  • C23C18/40—Coating with copper using reducing agents

Definitions

• the present invention relates generally to electroless copper plating solutions capable of producing ductile copper deposits and methods for producing ductile copper plating deposits by electroless copper plating.
• Electroless copper plating baths are widely used in metallization industries for depositing copper on various types of substrates. For example, in the manufacture of printed circuit boards, electroless copper baths are used to deposit copper on walls of through-holes and circuit paths as a base for subsequent electrolytic copper plating. Electroless copper plating is also used in the decorative plastics industry to deposit copper on non-conductive surfaces as a base for further plating of copper, nickel, gold, silver and other metals.
• Electroless copper baths generally contain water-soluble divalent copper compounds, chelating agents or complexing agents, reducing agents, and various other additives to make the bath more stable, adjust the plating rate and brighten the copper deposit.
• electroless copper plating solutions can be used to deposit copper on printed circuit boards, chip carriers and semiconductor wafers as well as any other circuit carriers and interconnect devices.
• the copper plating solutions can be used in printed circuit boards and chip carriers, and also for semiconductor wafers, to plate surfaces, trenches, blind micro vias, through hole vias (through holes) and similar structures with copper, and can be used to deposit of copper on surfaces, in trenches, blind-micro-vias, through-hole-vias, and comparable structures in printed circuit boards, chips, carriers, wafers and various other interconnect devices.
• through hole vias or “through holes”, as used in the present invention, encompasses all kinds of through hole vias and includes so-called “through silicon vias” in silicon wafers.
• Electroless copper deposits plated over the walls of through-holes, vias, interconnects, etc. provides conductivity between surfaces of a board and/or between circuit layers.
• the deposit In additive circuit manufacture, in addition to providing conductivity between surfaces and/or circuit layers, the deposit also serves as the conductor lines.
• Electroless copper is significantly less ductile than other forms of copper (i.e. such electrolytically deposited copper).
• electroless copper deposits typically possess an elongations of about 0.5 to 3.5 percent while electrolytic copper, as used in the manufacture of through-hole printed circuit boards, typically possesses an elongate in the range of from about 6 to 15 percent.
• electroless copper plating solutions that can produce a more ductile deposit for use in the manufacture of printed circuit boards and other similar substrates.
• U.S. Pat. No. 4,695,505 to Dutkewych describes an electroless copper deposit having an elongation capability of at least 10% by including a minor amount of a source of nickel ions and cyanide and/or ferrocyanide in the plating solution.
• Dutkewych suggests that with an adequate concentration of cyanide ions, an increase in elongation capability is realized when the nickel content is as low as about 5 ppm.
• Dutkewych requires that the composition contain cyanide ions in order to achieve the desired result which is not desirable from an environmental standpoint.
• EDTA ethylenediaminetetraacetic acid
• the present invention relates generally to an electroless copper plating solution comprising:
• G optionally, but preferably an additional stabilizer
• the present invention also relates generally to a method of producing a ductile copper deposit on a substrate using the electroless copper plating solution described herein.
• the inventors of the present invention have discovered an improved electroless copper electroless plating solution that can produce a ductile deposit on an underlying substrate.
• the electroless copper deposit exhibits high elongation and high tensile strength.
• the electroless copper plating solution described herein is able to produce a deposit exhibiting such high elongation and high tensile strength without the use of undesirable additives.
• the term “about” refers to a measurable value such as a parameter, an amount, a temporal duration, and the like and is meant to include variations of +/ ⁇ 15% or less, preferably variations of +/ ⁇ 10% or less, more preferably variations of +/ ⁇ 5% or less, even more preferably variations of +/ ⁇ 1% or less, and still more preferably variations of +/ ⁇ 0.1% or less of and from the particularly recited value, in so far as such variations are appropriate to perform in the invention described herein. Furthermore, it is also to be understood that the value to which the modifier “about” refers is itself specifically disclosed herein.
• spatially relative terms such as “beneath”, “below”, “lower”, “above”, “upper” and the like, are used for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It is further understood that the terms “front” and “back” are not intended to be limiting and are intended to be interchangeable where appropriate.
• the term “substantially-free” or “essentially-free” if not otherwise defined herein for a particular element or compound means that a given element or compound is not detectable by ordinary analytical means that are well known to those skilled in the art of metal plating for bath analysis. Such methods typically include atomic absorption spectrometry, titration, UV-Vis analysis, secondary ion mass spectrometry, and other commonly available analytically methods.
• composition and “bath” are used interchangeably throughout this specification.
• alkyl unless otherwise described in the specification as having substituent groups, means an organic chemical group composed of only carbon and hydrogen and having a general formula: C n H 2n+1 .
• the term “average” is equivalent to the mean value of a sample. All amounts are percent by weight, unless otherwise noted. All numerical ranges are inclusive and combinable in any order except where it is logical that such numerical ranges are constrained to add up to 100%.
• the present invention relates generally to an electroless copper coating composition and a method of using the same to provide a copper deposit exhibiting desired physical properties of high elongation and high tensile strength that are much improved over standard electroless copper coatings currently in the market.
• the process is applicable in molded interconnect device (MID) applications where it is highly desirable that stray plating does not occur and that there should be good adhesion to the substrate.
• MID molded interconnect device
• the electroless copper compositions described herein are also applicable in other processes including, for example, standard circuit board production and interconnect substrate production.
• the copper deposit produced has an elongation of greater that about 10%, more preferably greater than about 12%, even more preferably greater than about 14%, and even more preferably, greater than about 15% with a tensile strength of greater than about 30,000 psi, more preferably greater than about 40,000 psi, and even more preferably greater than about 50,000 psi as measured using ASTM E-345.
• adhesion to the MID substrate is capable of passing industry standard tape tests according to IPC-TM-650-IPC Test Methods.
• electroless copper plating deposits produced by the methods described herein also exhibit minimal, and preferably no stray plating on MID substrates.
• the electroless copper composition comprises:
• G optionally, but preferably an additional stabilizer
• the electroless copper composition described herein is an aqueous solution, meaning that the primary solvent of the solution is water.
• additional liquids that are miscible with water, including alcohols and other polar organic liquids may also be added to the composition and would be usable in the compositions described herein.
• the source of copper ions may be any suitable copper salt, including copper chloride, copper sulfate, copper nitrate, copper oxide, and combinations of the foregoing.
• the source of copper ions is copper sulfate.
• the source of copper ions is copper chloride.
• the concentration of the Cu ion is generally in the range of about 0.1 to about 10 g/L, more preferably about 0.5 to about 4 g/L, and even more preferably, in the range of about 2 to about 4 g/L.
• chelators or chelating agents include tartaric acid and salts thereof, citric acid and salts thereof, malic acid and salts thereof, acetic acids and salts thereof and other similar compounds.
• the chelator is a salt of tartaric acid, such as a salt of tartaric acid containing one or both of sodium and potassium.
• the tartaric acid salt comprises sodium potassium tartrate.
• the electroless copper composition of the present invention be at least substantially free of EDTA, more preferably that the bath does not contain EDTA in any measurable amount. That is, because of the very high affinity of EDTA for any metal ions, even small residual amounts of EDTA can complex with metal ions, making it more difficult to treat the resulting waste stream.
• EDTA ethylenediaminetetraacetic acid
• the molar ratio of the complexing agents, related to the total molar amount of all complexing agents, to copper ions is in the range of 1:1 to 10:1, preferably 1:1 to 8:1, more preferably 1:1 to about 4:1.
• a molar ratio of 1:1 to 4:1 of complexing agent(s) to copper ions means about 1 to 4 equivalents of complexing agent(s) related to copper.
• the source of alkalinity may be any suitable source of alkalinity and is used in an amount sufficient to adjust the solution pH to between about 11.0 and 14.0, more preferably between about 12.0 and about 13.0.
• the source of alkalinity is a hydroxide, such as sodium hydroxide or potassium hydroxide.
• the amount needed to achieve the desired pH may be within the range of about 1 to 15 g/L, more preferably about 5 to about 10 g/L.
• the reducing agent may be any suitable reducing agent that aids in reducing the copper ions in order to obtain metallic copper for plating.
• Reducing agents include, but are not limited to, aldehydes, such as, formaldehyde, formaldehyde precursors, formaldehyde derivatives, such as paraformaldehyde, borohydrides, such sodium borohydride, substituted borohydrides, boranes, such as dimethylamine borane (DMAB), saccharides, such as grape sugar (glucose), glucose, sorbitol, cellulose, cane sugar, mannitol and gluconolactone, hypophosphite and salts thereof, such as sodium hypophosphite, hydroquinone, catechol, resorcinol, quinol, pyrogallol, hydroxyquinol, phloroglucinol, guaiacol, gallic acid, glyoxylic acid, 3,4-dihydroxybenzoic acid,
• the reducing agents are chosen from formaldehyde, formaldehyde derivatives, formaldehyde precursors, borohydrides and hypophosphite and salts thereof, hydroquinone, catechol, resorcinol, and gallic acid. More preferably, the reducing agents are chosen from formaldehyde, formaldehyde derivatives, formaldehyde precursors, and sodium hypophosphite. Most preferably, the reducing agent is formaldehyde.
• the concentration of the reducing agent in the copper plating bath is preferably within the range of about 1 g/L to about 15 g/L, more preferably about 2 g/L to about 10 g/L, and even more preferably about 3 g/L to about 8 g/L.
• the electroless copper plating bath of the present invention should contain nickel metal ions in a sufficient amount to aid in increasing e the elongation of the copper deposit to above 10% elongation.
• Any source of nickel ions can be used in the practice of the invention.
• the source of nickel ions is nickel sulfate.
• the nickel ions are preferably present in the electroless copper plating bath of the invention in an amount between about 0.005 g/L to about 2 g/L nickel, more preferably between about 0.01 g/L to about 1.0 g/L, even more preferably between about 0.02 and about 0.04 g/L.
• Ni ions are of great benefit to the physical properties and rate of the deposit.
• this benefit at low nickel ion concentrations can only be realized if the solution is essentially free of EDTA and cyanide or cyanide derivatives.
• Lower Ni metal ion concentration has a desirable cost and environmental benefit.
• the electroless copper plating baths described herein also include a dipyridyl as a stabilizing agent.
• the dipyridyl comprises 2,2′-dipyridyl.
• the concentration of the dipyridyl is typically within the range of about 0.001 g/L to about 0.05 g/L more preferably about 0.002 to about 0.05 g/L, most preferably about 0.003 to about 0.015 g/L.
• the electroless copper plating bath of the invention includes a combination of nickel metal ions and 2,2′-dipyridyl, the combination of which has been found to produce an electroless copper plating deposit that exhibits the desired ductility (% elongation) and tensile strength described herein.
• the electroless copper plating solution may also comprise an additional stabilizing agent to further aid in stabilizing the plating solution against unwanted outplating (i.e., unwanted and/or uncontrolled deposition of copper, for example on the bottom of a reaction vessel or on other surfaces) in the bulk solution.
• This stabilizing function can be accomplished, for example, by substances that act as catalyst poison (e.g., sulfur or other chalcogenide containing compounds) or by compounds forming copper(I)-complexes, thus inhibiting the formation of copper(I)oxide.
• Suitable stabilizers include any stabilizer that is free of CN groups.
• the stabilizer is an organic compound containing divalent sulfur.
• suitable stabilizing agents include, but are not limited to, dithiobiuret, diethyldithiocarbamate, ammonium (or sodium or potassium) pyrrolidinethiocarbamate, thiomalic acid, and other similar compounds.
• any cyanide-free stabilizing agent or mixtures thereof that are capable of preventing decomposition of the copper electroless plating bath would be known to those skilled in the art and are usable in the compositions described herein.
• the stabilizing agent is also beneficially selected so that it does not significantly impact (i.e., decrease) the % elongation of the deposit.
• the concentration of the additional stabilizer is generally within the range of about 0.000005 g/L to about 0.01 g/L, more preferably about 0.00001 to about 0.0001 g/L, most preferably about 0.00002 g/L to about 0.00008 g/L.
• the electroless copper plating bath also comprises a water-soluble polymer.
• Suitable water-soluble polymers include those having a molecular weight of at least 300 g/mol. While it is not required that the bath composition contain the polymer, in a preferred embodiment, the bath contains the water-soluble polymer.
• One preferred polymer that may be used in the bath of the invention is methoxypolyethylene glycol. In a preferred embodiment, the methoxypolyethylene glycol has a molecular weight of at least 750 g/mol. This is preferred because it has a high enough molecular weight to increase % elongation, but if higher molecular weight methoxypolyethyleneglycol is utilized, the plating rate is slower which is less desirable.
• the concentration of the water-soluble polymer is generally within the range of about 0.01 g/L to about 1 g/L, more preferably about 0.05 to about 0.5 g/L, most preferably about 0.08 to about 0.15 g/L.
• polyethylene glycol i.e., no methoxy
• polyethylene glycol i.e., no methoxy
• other polymers and surfactants that aid in increasing the elongation (or that do not have a detrimental effect) can also be employed.
• Other polymers include, for example:
• Phosphate ester based surfactants preferably moderate to low foaming varieties
• the copper electroless solution should be essentially free of any cyanides, including NaCN, KCN, KFe(CN) 6 , and K2Fe(CN) 6 .
• cyanides including NaCN, KCN, KFe(CN) 6 , and K2Fe(CN) 6 .
• the inventors have found that the presence of cyanide and cyanide derivatives in the bath can lower the elongation of the resulting deposit.
• the electroless copper plating baths described herein also do not require an amino acid in the bath to produce the desired % elongation. That is, to be clear, in one preferred embodiment of the invention, the electroless copper plating bath is free of any amino acid and contrary to certain prior art baths, the present invention does not require the presence of an amino acid to achieve the desired result.
• the present invention also relates generally to an electroless copper plating bath consisting essentially of:
• G optionally, but preferably an additional stabilizer
• the present invention relates generally to an electroless copper plating bath consisting of:
• G optionally, but preferably an additional stabilizer
• the present invention relates generally to a method of electrolessly depositing copper on a substrate, the method comprising the steps of:
• the electroless copper plating solution comprising:
• the substrate may be dipped or immersed in the solution of the invention.
• a whole surface of a substrate may be plated with copper, or only selected portions.
• the copper deposit produced in accordance with the present invention is able to obtain a % elongation of greater than about 10%, more preferably greater than about 12%, even more preferably greater than about 13%, and even greater than about 14%, and even greater than about 15%.
• the tensile strength of the deposit is greater than about 30,000 psi, more preferably greater than about 40,000 psi, most preferably greater than about 50,000 psi.
• the process has a high plating rate at moderate temperatures
• the presence of the Ni ions in the plating bath described herein increases the plating rate above what is obtained in other baths with no Ni ions.
• the rate advantage is especially apparent when comparing to other electroless copper baths that contain bipyridine. Normally bipyridine causes a lower rate in these types of electroless copper baths and the higher the bipyridine concentration the lower the plating rate.
• the use of bipyridine in the recited concentration range has virtually no effect on the plating rate.
• it was observed that the plating rate is higher than if the Ni ions were removed.
• the use of the Ni ions in the electroless copper plating bath of the instant invention provide two benefits (1) a higher plating rate, and (2) improved physical properties of the deposit.
• the ability to obtain a high plating rate at lower temperature allows the bath to be operated at lower temperatures which increases the stability of this and any electroless copper bath.
• the solution is agitated during use, as would be known to those skilled in the art.
• the process is generally carried out for a sufficient time to yield a deposit of the desired thickness required, which depends on the particular application.
• the substitute is a MID or a PCB.
• the electroless deposition of copper according to the process of the invention can particularly be used for the through-plating of holes, surfaces, trenches, blind micro vias in printed circuit boards. Double sided or multilayer boards (rigid or flexible) may also be plated by means of the present invention.
• the process of the invention can be used to provide an electroless copper deposits with a thickness in the range of 0.05 to 10 ⁇ m depending on the substitute.
• Substrates used for printed circuit board manufacture are most frequently epoxy resins or epoxy glass composites. But other substances, notably phenolic resins, polytetrafluoroethylene (PTFE), polyimides polyphenyleneoxides, BT (bismaleintriazine)-resins, cyanate esters and polysulphones can be used.
• phenolic resins polytetrafluoroethylene (PTFE)
• polyimides polyphenyleneoxides
• BT bismaleintriazine-resins
• cyanate esters and polysulphones can be used.
• the process described herein can be used in a plating on plastics process to electrolessly deposit copper on substrates such as ABS
• the electroless plating process is carried out at a temperature in the range of about 20 to about 60° C., more preferably about room temperature (i.e., about 25° C.) to about 55° C., even more preferably about room temperature to about 45° C.
• the plating rate is typically about 3 to 4 ⁇ m/hour at a temperature of about 40° C. Temperature and pH level can affect plating rate and can be adjusted if desired to adjust the plating rate.
• This can be accomplished, for example, by feeding the reaction chemicals with a chemical controller so that the deposition does not fluctuate (i.e., remains substantially constant) while the metal film is being deposited.
• the substrate i.e. the surfaces of the substrate that are to be plated with copper, particularly non-metallic surfaces, may be pretreated to make the substrates more receptive or autocatalytic for copper deposition.
• all or only selected portions of a surface may be pretreated.
• a pretreatment is not necessary in every case and depends on the kind of substrate.
• a catalyzing metal i.e., a noble metal, such as palladium
• the substrate comprises ABS, which has been doped with a copper chromite catalyst.
• the copper chromite catalyst concentrates on the surface and becomes active. Thus, plating only occurs where the material has been ablated and isolated traces of metal deposit onto the substrate. Therefore, no plating resist is required and a full-build electroless copper deposit directly forms the circuit where it was ablated.
• a permanganate etching step is employed, which is a multi-stage process, the steps of which are a swelling step, a permanganate etching step and a reduction step.
• the sweller used in the swelling step is made of a mixture of organic solvents. During this step drill smear and other impurities are removed from the surfaces of the substrate. A high temperature of 60-80° C. promotes the infiltration of the sweller which leads to a swelled surface. Therefore, a stronger attack of the subsequently applied permanganate solution is possible during the permanganate etching step.
• the reduction solution of the reduction step removes the manganese dioxides produced during the permanganate step from the surfaces.
• the reduction solution contains a reducing agent and optionally a conditioner.
• the desmear process may be combined with the above described steps.
• the desmear process may be performed before step a) of the above described pretreatment process or the desmear process may be performed instead of steps a) and b) of the above described pretreatment process.
• the bath constituents are mixed together to form an aqueous electroless copper solution which is then used to deposit electroless copper on an ABS substrate by immersing the ABS substrate into the deposit for 270 minutes to provide an electroless copper deposit of about 13 ⁇ m on the substrates.
• the substrate is one that is first doped with a copper chromite catalyst and laser ablated. Thereafter, % elongation and tensile strength are measured using ASTM E-345 Standard Test Methods of Tension Testing of Metallic Foil IPC-TM-650 IPC Test Method.
• the electroless copper solution was a standard electroless copper solution of MacDermid MID 100TM electroless copper (available from MacDermid Enthone, Inc. Waterbury, Conn.)
• the improved electroless copper plating bath of the present invention is able to produce a ductile copper deposit that exhibits a % elongation that is much higher than the % elongation that is achievable with electroless copper plating solutions of the prior art.
• the improved copper plating bath of the instant invention can produce a ductile copper deposit exhibiting a % elongation of greater than about 12.0%, greater than about 13.0%, greater than about 14.0% and even greater than about 15.0%. This result cannot be achieved with prior art electroless copper plating baths and certainly cannot provide the improved results in the absence of EDTA and CN.

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