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
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/28—Sensitising or activating

Definitions

• Solid compositions dilutable to optically clear sensitizing solutions for rendering surfaces receptive to the deposition of an adherent electroless metal comprise a metal complex consisting of (a) a precious metal selected from a group consisting of the precious metals of the fifth and sixth periods of Groups VIII and I-B of the Periodic Table of Elements, (b) a Group IV metal of the Periodic Table of Elements Which is capable of two valence states and (c) an anion capable of forming a stable moiety with both valence states of the Group IV metal, in which the molar ratio ot (a) to (b) to (c) is from about 121:3 to 1:6:24.
• the solutions can be prepared by diluting the solid compositions. Controlled excesses of (b) and (c) and hydrogen ion and wetting agents enhance the solubility of the powdered product and stability of the diluted solutions. Processes for rendering surfaces receptive to the deposition of an electroless metal, e.g., copper, nickel, cobalt, palladium, gold and silver, are also provided.
• an electroless metal e.g., copper, nickel, cobalt, palladium, gold and silver
• the subject matter of the present invention relates to new and useful precious metal sensitizing compositions. More particularly, the invention relates to solid compositions comprising a precious metal complex, and to solutions prepared therefrom. The solutions are used to render surfaces of a substrate catalytic to the reception of an electroless metal.
• the plural bath process while readily effecting sensitization, deposits on metals a flash coating of the precious metal from the sensitizing bath.
• the precious metal so flash coated from the sensitizing bath disrupts the balance of the bath.
• the addition of the precious metal bearing solution to the bath is required.
• flash coating of precious metal normally leads to a low grade of adhesion, thereby materially affecting the bond and peel strength of an electroless metal deposit.
• Another object of the present invention is to provide new and useful solid compositions which are dilutable to true solutions and methods for sensitizing substrates using them which substantially obviate the problem of nonadherent precious metal flash coatings.
• Yet another object of the invention is to provide solid compositions and methods for sensitizing substrates with a precious metal which involve using very dilute treating solutions and thereby materially diminishing production costs.
• compositions which contain a relatively large excess of component (b) it is preferred to use a large excess of component (c) to solubilize the complex.
• this will be introduced in the form of 01- or Bror SnC1 and preferably as I-ICl. Extremely large excesses of this component do not seem to be detrimental to sensitizing activity. As to HCl, this seems to serve a two-fold purpose: it provides both a large excess of Cl" ion and also H+ ions, both assisting in the solubilization of the powdered product.
• component (c) e.g., sodium chloride
• component (b) is stannous chloride or a similar hydrolyzable composition which forms a basic salt, e.g., Sn(OH)Cl
• acid will be added to prevent hydrolysis of the Group IV metal.
• High concentrations of acid are preferretd, as will be explained hereinafter.
• optically-clear sensitizing solutions which have been prepared by diluting the solid compositions with an acid or a mixture of water and an acid, until the concentration of component (a) has been reduced to a concentration of from about 00003 gram/ liter to about 1.5 grams per liter.
• Another feature of the invention is a process to prepare the concentrate comprising heating an aqueous mixture of the components (a), (b) and (c) at a temperature of from about 80 C. to about the boiling point until formation of the complex is complete, and then concentrating the mixture until a friable, solid product is obtained.
• Still another feature is a process to prepare the concentrate which comprises mixing an aqueous solution of components (a) and (c) with an aqueous solution of components (b) and (c) and heating the mixture at from 80 C. to its boiling point, and then concentrating the mixture until a friable, solid product is obtained.
• the present invention further relates to an improved process for rendering surfaces receptive to the deposition of an adherent electroless metal, as well as a process for electrolessly depositing a metal on a substrate which has been sensitized with the sensitizing solutions of the present invention.
• An additional embodiment of the invention relates to particular acidic precious metal solutions for rendering surfaces receptive to the deposition of electroless copper, nickel, cobalt, palladium, gold or silver, and especially to copper or nickel.
• the invention consists of the novel methods, processes, steps and improvements shown and described.
• the present invention provides a significant improvement over the known sensitization techniques and compositions in that a procedure and composition is provided which will cause conductive and non-conductive materials to be so sensitized simultaneously that efficient and uniform deposition of an adhering electroless metal thereon may be readily effective; thus permitting, by way of illustration, copper plating of the non-metallic surfaces of the side Walls of the apertures defined in a plastic base material, as well as the concomrnitant adherent electroless deposition of copper on pre-formed copper surfaces on the plastic base.
• Illustrative of the conductive and nonconductive, metallic and non-metallic surfaces which can be plated uniformly with adherent electroless metal by use of the sensitizing solutions and techniques of the present invention are plastic surfaces and surfaces of metallic copper, iron, nickel, cobalt, silver, gold and alloys thereof, such as brass, sterling silver and the like.
• the present invention can be employed to render a surface catalytic to the reception of such metals as copper, nickel, palladium, cobalt, silver, gold and the like.
• a further advantage of the present invention is that sensitization as taught herein leads to practically complete avoidance of the deposition of a flash coating of precious metal from the sensitizing bath.
• a flash coating of precious metal normally leads to a low grade of adhesion. Also, avoidance of such deposition economically conserves the precious metal.
• the sensitizing solution can be directly incorporated in a plastic base at the time of its manufacture. This can be achieved by utilizing an organic sensitizing solution employing a solvent such as cyclohexanone, a highly viscous paste like composition. Alternatively, the solution can be reduced to a solid form by employing a counter ion and directly incorporating such solid in a plastic base at the time of manufacture. Therefore, the advent of the present invention provides for the preparation of presensitized plastic substrates.
• the most notable advantage occasioned by the advent of the present invention resides in the fact that such solutions possess a sensitizing activity at dilute levels.
• a complex is formed between the metals and the anion.
• the preferred palladium-tin-chloride solid complex of this invention is acid soluble. It is optically clear in dilute solution. It is filterable through ultra-membranes through which colloidal sensitizers will not pass. It has an ultraviolet absorption peak in 'aqueous acidic solution at 295-310 m and 320 m
• Solid compositions comprising the complex according to this invention may be diluted to levels of concentration which can easily and reproducibly be directly formulated into active sensitizing solutions.
• the invention makes available stable sensitizing solutions comprising significantly lower concentrations of precious metal than can be produced by other known methods, excluding, of course, the methods of copending applications Ser. No. 9,060, filed Feb. 5, 1970 and Ser. No. 801,167, filed Feb. 20, 1969*.
• the treating or sensitization procedure whichis an embodiment of this invention is an intermediate step between pretreatment or cleaning of the surfaces upon which the metal is to be electrolessly deposited and the actual deposition of the metal.
• the treatment to be afforded the surface to be plated depends upon the cleanliness of the material to be treated and associated factors.
• the first step in the procedure for effecting deposition of adherent electroless metal is to clean thoroughly the article or panel upon which plating is to occur. This is desirably accomplished by scrubbing the panel with pumice or the like to remove he avy soils; rinsing with water; and subsequent removal of soil due to organic substances from the panel and apertures defined therein with a suitable alkali cleaning composition.
• a typical alkaline cleaner composition is as follows:
• Oxides are removed from copper panel surfaces and apertures by application of a light etching solution such as a 25 percent solution of ammonium persulfate in water as is described in Bulletin No. 86 of the Becco Chemical Division of the Food Machinery and Chemical Corporation, Buffalo, NY.
• the surface oxides also may be removed by application of the cupric chloride etchant solution described by Black in US. Pat. No. 2,908,557. This treatment should not exceed 2 to 3 minutes.
• the treatment period and temperature are significant, particularly where the panel surfaces are formed of a conductive metal, in that elevated temperatures and extended periods of time beyond those described may result in removal not only of the oxide materials but of the conductive metal, such as cupper foil, forming the surfaces of the panel.
• the panel is rinsed thoroughly after this step with water to remove all semblance of etching compounds. Care should be taken to avoid the formation of further oxide film during rinsing or as a result of air oxidation.
• the panel may be inserted in an acid solution comprising, for example, 1020 percent by weight of hydrochloric acid in water for a period of from 2 to 5 minutes, and from this bath the panel is placed in the sensitization or treating solution of the present invention.
• a sanding operation with a fine abrasive can also be used to remove oxides.
• the sensitizing solution prepared by diluting the solid composition comprises an acidic aqueous solution of a metal complex as defined above consisting of (a) a precious metal, (b) a Group IV metal and (c) an anion. It is optically-clear, i.e. non-colloidal.
• a precious metal e.g. palladium, platinum, gold, rhodium, osmium, iridium and mixtures of these metals.
• the inorganic and organic acid salts of these metals, and of the Group IV metals such as the chlorides, bromides, fluorides, fiuoborates, iodides, nitrates, sulfates and acetates of stannous tin, titanium and germanium among others may be used.
• Other acid salts of the precious metals and Group IV metals will readily suggest themselves to those skilled in the art.
• the salts are preferably soluble in water, or in organic or inorganic acid aqueous solutions.
• the chloride is preferred, both for the precious metal, and the Group IV metal compound.
• the preferred precious metals and Group IV metal are palladium or platinum, particularly palladium, and stannous tin.
• the precious metal concentration should be from at least about 0.0003 to about 1.5 grams/liter of solution. While the higher end of this range causes sensitization to be completed in very abbreviated periods of time, e.g. ten seconds, the lower end of this range is normally more economic.
• the bath can be prepared directly or by diluting a concentrate.
• the solid composition as defined above are diluted with an aqueous solution of suitable acid. If a dry power acid, e.g., citric acid, is included in the composition, water alone can be used.
• the solid compositions are prepared by heating the salts of the precious metals and a Group IV metal salt in an aqueous solution of suitable acid as will be described hereinafter and evaporating substantially to dryness.
• suitable acid e.g., hydrochloric acid, hydrofluoric acid, sulfuric acid, citric acid, acetic acid and the like.
• the anion of the inorganic acid corresponds to the anion of the salt of the precious metal, or to the anion of the Group IV metal salt.
• the anion of the acid should preferably correspond to the common anion of the salts. Where the anion of the precious metal differs from that of the Group IV metal salt, the anion of the acid preferably corresponds to the anion of the precious metal salt.
• acids having anions which differ from the anions of the precious metal salts or of the Group IV metal salt may also be used.
• the hydride anion, I-I- can be part of the complex.
• Preferred anions are Cland SnC1
• concentration of the acid in the sensitizing solutions depends upon the strength of the acid employed. The concentration of the acid should be at least sufiicient to prevent hydrolysis of the Group IV metal, at the final concentration.
• a suitable lower limit is 0.001 normal.
• At the upper end of the concentration of the acid may be as high as 15 normal, or even higher.
• the concentration of the acid in the sensitizing solution generally varies between about 0.02 and 7.5 normal.
• the concentration of the acid in the sensitizing solution approaches the upper limit given hereinabove.
• the concentration of acid in the sensitizing solution should, of course, also be high enough to solubilize the salts of the precious metals and the Group IV metal and also be high enough to render the solution suitable for use as a sensitizer for the material being treated. Care should be used in selecting the acid concentration to insure that the specimen being treated is not adversely attacked or corroded by the treating solution.
• the Group IV metal ion concentrtaion may vary widely but must be maintained in excess of a stoichiometric amount based on the amount of precious metal ions present in the sensitizing solution. Normally a large excess of, for example, stannous chloride, is maintained to allow for air oxidation of the stannous ion. Illustratively, concentrations of as high as 50 grams per liter of stannous chloride are not detrimental to the effectiveness of the sensitizing activity of the diluted solutions.
• the sensitizing solutions of the present invention may contain additional agents to stabilize the solution, e.g., against the effects of atmospheric oxidation.
• agents will include the use of additional quantities of the Group IV metal, as for example, additional stannous chloride may be added to a palladium-stannous chloride sensitizing solution, as well as compounds, such as organic hydroxy compounds (01s), dihydroxy compounds (diols) and polyhydroxy compounds (polyols), the fiuorinated hydrocarbon wetting agents and hydrogen fluoride.
• One result of the addition of such compounds to the sensitizing solution is the inhibition of oxidation of the Group IV metals and the subsequent reduction of the precious metals.
• the stabilizers if solid, can be compounded with the solid sensitizer or they can be co-deposited therewith by mixing solutions and evaporating the solvents.
• stabilizing ingredients to the complex is an embodiment of this invention which improves the stability of the solution and avoids formation of undesirable sludges on surfaces, e.g.,
• the nature of the stabilizing ingredient is not particularly critical. It should be soluble at least in an amount great enough to provide the desired stabilization effect. Evidence of effective stabilization is easily observed in comparison with control baths, i.e., those without the stabilizing ingredient present. These latter baths over a period of one week or so will be seen to deposit a film of metallic compound or to precipitate such a compound. On the other hand, baths to which an effective amount of the stabilizing ingredient has been added will remain clear and be stable and storable for periods of at least two weeks and even longer. In any event, the minimum amount will vary somewhat from compound to compound but is easy to determine routinely. There is no apparent reason to limit the quantity of the stabilizing ingredient to the minimum effective amount and often substantially more will be used, the choice being primarily dictated by economic considerations.
• the stabilizing ingredient need not be completely water soluble, although for ease of formulation a high degree of water solubility is desirable.
• the hydroxy compounds which can be used most efliciently would be of relatively low molecular weight, polysubstituted with hydroxy groups or containing at least one hydroxy group and other functional groups such as sulfonic acid groups, phosphate groups, amino groups, halogens, carboxyl groups and the like, which tend to enhance solubility in polar media.
• the solubilizing group can be organic or inorganic, anionic, cationic, nonionic, amphoteric and water soluble.
• the wetting agents should be active in acidic solutions and have good thermal stability. Especially preferred are those wherein Z is anionic.
• a preferred species has the following spectrum of solubilities in acid media, in grams/ 1000 grams of solution: 12 /2% hydrochloric acid, 1; 37% hydrochloric acid, 0.1; 12 /2% nitric acid, 1; 70% nitric acid, 5; 12 /2% phosphoric acid, 1; 85% phosphoric acid, 1; l2 /2% sulfuric acid, and 97% sulfuric acid, 0.5.
• Another preferred species has the folowing solubility spectrum: 12 /2% hydrochloric acid, 10; 12 /2% nitric acid, 20; and 12 /2% sulfuric acid, 10.
• Particularly useful fluorinated hydrocarbon wetting agents of this type are sold under the trade name Fluorad by the Minnesota Mining and Manufacturing Company, St. Paul, Minn.
• the preferred species, described above, are designated Fluorad FC-9S and FC98, respectively.
• Preferred hydroxyl-containing stabilizing ingredients are open chain aliphatic mono-01s, diols or polyols of from about 1 to about 12 carbon atoms, e.g., methanol, ethanol, iso-propanol, ethylene glycol, propylene glycol, 1,4-butane diol, glycerol, glucose, sucrose, and the like; and closed chain aliphatic or aromatic monoor dicarboxylic mono-01s, diols or polyols of from about 6 to 12 carbon atoms, e.g., cyclohexanol, cyclohexanediol, inositol, phenol, fi-naphthol, resorcinol, sorbitol, hydroquinone, pyrogallol, phloroglucinol, naphthoresorcinol, and the like.
• these stabilizing ingredients have a water solubility of at least greater than about 4% by weight, especially those in the aromatic family.
• Particularly preferred stabilizing ingredients of this type are isopropanol, ethylene glycol, glycerol, resorcinol, sorbitol, hydroquinone, pyrogallol and phloroglucinol. These can generally be employed at an appropriate concentration in the range of from about 2 to about 50% by weight in the final mixture.
• the aromatic compounds will be employed at 2 to 7 Wt. percent and the aliphatic compounds will be used in concentrations of from about 4 to 50 wt. percent, although higher and lower amounts can be formulated, as mentioned above.
• An especially preferred stabilizer is resorcinol at 20 to 70 grams/liter.
• Illustrative fluorinated hydrocarbon wetting agents have a formula selected from the group consisting of and wherein n is an integer of from 3 through 10, and Z is a hydrophilic group.
• n is an integer of from 3 through 10
• Z is a hydrophilic group.
• surfactants are composed of molecules containing a perfluorinated tail portion and a hydrophilic head portion.
• the fluorocarbon portion of the molecules advantageously contains either 3 or 7 carbon atoms where the surfactant is a perfluorosulfonic acid derivatives.
• the hydrophilic portion of the fluorocarbon surfactants can be any typical hydrophilic group such as hydroxyl, alkali metal or alkaline earth metal substituted hydroxyl, an alkali metal group, an ammonium group, amine groups, substituted amine groups, quaternary ammonium salts amide and substituted amide groups, and the like.
• An illustrative surfactant for this embodiment of the invention has the formula:
• m m s Useful too is hydrogen fluoride itself. This will be employed at l to 10 g./liter of solution and preferably at about 3 g./liter. Conveniently, this latter concentration is made by adding enough 60% aqueous HF to provide 50 mL/liter.
• complexing reaction which occurs between the metals and the anion results in the formation of more than one and possibly several complexes.
• these can be depicted as including complex anions of the formula (MeSn X mixtures thereof, wherein Me is Ru, Rh, Pd, Os, Ir, Pt, Au or a mixture thereof, and X is halogen, i.e., fluorine, chlorine, bromine, or iodine; preferably chlorine or bromine.
• Preferred complexes are those wherein Me is Pd or Pt.
• the concentrations of the components of the complexes are expressed in terms of molar ratio. Therefore, the molar ratio of precious metal to Group IV metal to anion of the complexes of the present invention is from about 1:1:3 to 1:6:24.
• Sensitizing solutions of the instant invention can be prepared from the solid compositions, which may be stored, and shipped and diluted when the sensitizing solution is to be used for electroless plating. When properly prepared, in accordance with the teachings hereof, such diluted solids form true, clear solutions.
• compositions of this invention can be prepared in oneor two-steps:
• an aqueous mixture which contains components (a) (b) and (c), as defined above, in which mixture component (a) is present in a concentration of at least about 1.5 grams/liter, the molar ratios of (a) to (b) to (c) each being, respectively 1: at least 1: at least 3; is heated at a temperature of from about 80 C. to about the boiling point of the mixture until formation of the metal complex is substantially complete, then concentrating, e.g., by evaporation, with or without heat, at atmospheric or reduced pressure or by freeze drying, the mixture until a friable, solid product is obtained.
• an aqueous solution containing a salt of component (a) in a concentration of from about 1.5 grams per liter up to about the limit of solubility of the salt in water at the boiling point and component and an aqueous solution of component (b) and (c), the ratios of (a):(b):(c) each being respectievly, 1: at least about 1: at least about 3, are first prepared.
• the two solutions are mixed together and heated at a temperature of from about 80 C. to about the boiling point of the mixture until formation of the complex is substantially complete, and then concentrating the mixture until a friable, solid product is obtained.
• palladium 4.8 to 100 grams/liter (calculated as metal) can be conveniently used. Depending on the temperature, it is preferred to heat the mixture for from about 20 to 90 minutes, although this is not critical.
• a completely dry product can be made which will be soluble and stable in plain water (as opposed to acid or water and acid) can be prepared by providing:
• a co-mixed dried form of a stabilizer such as a fluorinated hydrocarbon wetting agent or resorcinol
• EXAMPLE 1 A solid composition, dilutable to an optically clear, sensitizing solution is prepared.
• a first solution comprising the following ingredients:
• EXAMPLE 3 A solid composition, dilutable to an optically-clear sensitizing solution is prepared in one step. The followingformulation is used:
• Palladium chloride (g.) 62.5 Hydrochloric acid (37%, ml.) 700 Stannous chloride dihydrate (g.) 800 Water to make total (ml.) 1295 Stannous chloride is dissolved in the hydrochloric acid, then the water is added. The palladium chloride is added with agitation. The mixture is heated to C. for 20 minutes, then boiled for .1.5 hours and cooled, The mixture is evaporated to a friable dark solid by the procedure of Example 1 using a steam bath to assist in water removal.
• Palladium chloride (g.) 10 Hydrochloric acid (37%, ml.) 200 Water to make total (ml.) 500 The palladium salt dissolves slowly in the acid-water mixture.
• a second solution is prepared comprising the following ingredients: Stannous chloride dihydrate (g.) 800 Hydrochloric acid (37%, ml.) 500
• the first solution is added to the second with agitation, then the mixture is boiled for 1.5 hours, during which time it changes color from blue or purple, through green, then straw-yellow and, finally, brown.
• 0.8 g. of a fluorocarbon wetting agent (PC-95, 3M Company, St. Paul, Minn.) is added.
• the dark product can be diluted with 12% aqueous hydrochloric acid to obtain a highly active sensitizing solution.
• Example 5 The procedure of Example 1 is repeated, respectively substituting for the palladium chloride, stoichiometricallyequivalent amounts of the following: ruthenium chloride (RuCl rhodium chloride (RhCl3); osmium chloride ('OsCl iridium chloride (IrCl and platinum chloride (PtCl Solid compositions according to this invention are obtained containing, respectively, ruthenium, rhodium, osmium, iridium and platinum.
• a sensitizing solution according to this invention is prepared by taking an appropriate weight of the composition from Example 1, diluting it with a mixture comprising 490 ml. of 37 percent hydrochloric acid and 490 ml. of water. The resulting solution will contain about 0.6 gram/liter of palladium in the form of the palladiumstannous chloride complex of this invention and will have good catalytic activity.
• catalytically active sensitizing solutions are prepared by taking 11 appropriate portions of the compositions of Example 1 and diluting them, respectively, to 1 liter in 1:1 by volume of a mixture of 37% aqueous hydrochloric acid and water.
• the solutions contain, respectively, about 0.0003 gram and 1.5 grams of palladium per liter.
• EXAMPLE 7 The solids of Example are diluted with enough 1:1 mixture by volume of 37% hydrochloric acid and water to provide sensitizing solutions according to this invention containing, respectively, 0.6 and 1.5 grams/liter of ruthenium, rhodium, osmium, iridium and platinum.
• stannous chloride is preferred in the practice of the present invention
• other stannous tin compounds such as, for example, stannous fluoborate and stannous sulfate are also suitable for use in the seeding, i.e., sensitizing compositions described herein and in equivalent concentrations.
• the panel surfaces including any side walls of the apertures defined therein are thereafter thoroughly rinsed with water to entirely remove the sensitizing solution therefrom.
• the panel is then passed through a further bath of lactic acid, suitably diluted, e.g., about 10-20 percent, the passage employing a period of from 10 to 20 seconds, and the panel is again rinsed with water prior to immersion in a suitable electroless plating bath.
• lactic acid suitably diluted, e.g., about 10-20 percent
• electroless plating baths may be used for the deposition of the adherent metal after sensitizing of the plating surface wtih the compositions of the present invention.
• the electroless copper deposition may be followed by electroplating with copper or other metals to build up copper thicknesses of 0.001 to 0.002 inch or greater.
• electroless copper is ordinarily deposited on apertures formed in plas tic insulation sheets which have conductive copper foil laminated on both top and bottom surfaces.
• the circuits are conventionally electroplated with copper or other metals to build up copper thicknesses of 0.001 to 0.002 inch or greater.
• Electroplated copper is required over the electroless copper to form rugged conductive copper on the walls of the aperture approximately 0.001 inch thick or greater.
• the adhesion between the electroless copper and the foil originally laminated to the plastic sheet has been very poor due to a poorly adherent flash coating of precious metal from the catalyzing step.
• the subsequent electrodeposits fail because of the flash coating and could easily be stripped off merely by the application of pressure sensitive adhesive coated cellophane tape such as Scotch cellophane tape manufactured by the Minnesota Mining and Manufacturing Company. Therefore, prior to the advent of the present invention, in order to achieve adherent coating, the surface of the copper foil had to be mechanically abraded before electroplating to remove all trace of the electroless copper deposits.
• the electroplated copper may be deposited directly and will adhere so strongly that if the plastic base sheet is broken, the copper foil may be bent back and forth on itself until it breaks but no separation is evident between the original laminated foil and the electroplated copper film.
• a solid composition, dilutable to an optically clear, sensitizing solution for rendering a surface receptive to the deposition of an adherent electroless metal which comprises a metal complex consisting essentially of:
• composition as defined in claim 1 which includes, in addition to the amount of component (b) in said complex, a sufficient excess of component (b) to provide from 3 to 100 moles of component (b) per mole of complex in the total composition.
• composition as defined in claim 2 wherein said excess of component (b) provides from 5 to moles of component (b) per mole of complex in the total composition.
• composition as defined in claim 2 which also includes an excess of component (c) over that present in the complex.
• a composition as defined in claim 1 which includes an acid in an amount at least sufiicient to prevent hydrolysis of the Group IV metal when said composition is diluted.
• component (c) is C11 SnCl or a mixture thereof.
• component (c) is Cl, SnCl or a mixture thereof.
• Me is Ru, Rh, Pd, Os, Ir, Pt, Au or a mixture thereof, and X is halogen.
• a process for the preparation of a solid composition as defined in claim 1 which comprises heating an aqueous mixture containing said components (a), (b) and (c), in which mixture component (a) is present in a concentration of at least about 1.5 grams/liter, at a temperature of from about C. to about the boiling point of said mixture, until formation of said metal complex is substantially complete, then concentrating said mixture until a solid product is obtained.
• a process for the preparation of a solid composition as defined in claim 1 which comprises (1) providing an aqueous solution containing a salt of said component (a) in a concentration of from 13 about 1.5 grams per liter up to about the limit of solubility of said salt in water and component (2) providing an aqueous solution of said components (b) and (c), the ratios of components (a):(b'):(c) being 1: at least 1: at least 3; (3) mixing said solutions and heating the mixture at a temperature of from about 80 C. to about the boiling point of said mixture; and
• step (3) (4) concentrating the mixture from step (3) until a solid product is obtained.
• a solid composition as defined in claim 1 which includes, as a stabilizing ingredient, a compound selected from the group consisting of organic mono-01s, diols and polyols and a fluorinated hydrocarbon wetting agent, the amount of said compound in said cmposition being at least sufiicient to prevent separation from diluted solutions thereof of component (a) as a metallic film or precipitate.

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Cited By (22)

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• 1970
  • 1970-06-29 US US50918A patent/US3672923A/en not_active Expired - Lifetime
• 1971
  • 1971-04-20 CA CA110846A patent/CA934902A/en not_active Expired
  • 1971-06-24 AT AT549171A patent/AT314306B/de not_active IP Right Cessation
  • 1971-06-25 GB GB2987471A patent/GB1349666A/en not_active Expired
  • 1971-06-25 CH CH937671A patent/CH571577A5/xx not_active IP Right Cessation
  • 1971-06-28 ES ES392729A patent/ES392729A1/es not_active Expired
  • 1971-06-28 DK DK316171A patent/DK148919C/da not_active IP Right Cessation
  • 1971-06-29 FR FR7123698A patent/FR2100042A5/fr not_active Expired
  • 1971-06-29 JP JP4757771A patent/JPS5515544B1/ja active Pending
  • 1971-06-29 NL NLAANVRAGE7109004,A patent/NL169757C/xx not_active IP Right Cessation
  • 1971-06-29 SE SE7108398A patent/SE427190B/xx unknown
  • 1971-06-30 IT IT51295/71A patent/IT954171B/it active
• 1973
  • 1973-07-20 AT AT643273*1A patent/AT326443B/de active

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