US3399268A - Chemical metallization and products produced thereby - Google Patents

Description

Aug. 27, 1968 F. w. SCHNEBLE; JR.. ET 3,399,268

CHEMICAL METALLIZATION AND PRODUCTS PRODUCED THEREB'Y Original Filed Aug. 22, 1962 FlG.-l FIG.- 2

FIG."3

V J I L ,0

W I: I %A INVENTORS FREDER W. SCHNE E, JR JOHN McCORMA RUDOLPH J. ZEBL ISKY JOHN DUFF W! A ON JOSEPH POLIC T United States Patent fice 3,399,268 CHEMICAL METALLIZATION AND PRODUCTS PRODUCED THEREBY Frederick W. Schneble, Jr., Oyster Bay, John'F. Mc- Cormack, Roslyn Heights, Rudolph J. Zeblisky, Hauppague, John D. Williamson, Miller Place, and Joseph Polichette, South Farmingdale, N.Y., assignors, by mesne assignments, to Photocircuits Corporation, Glen Cove, N.Y., a corporation of New York Continuation of application Ser. No. 404,302, Oct. 16, 1964, which is a division of application Ser. No. 218,656, Aug. 22, 1962, now Patent No. 3,259,559. This application June 7, 1966, SenNo. 555,918

The portion of the term of the patent subsequent to June 25, 1980, has been disclaimed 18 Claims. (Cl. 174-685) ABSTRACT THE DISCLOSURE The invention is directed to novel articles of manufacture comprising an agent catalytic to the reception of electroless metal which catalytic agent is dispersed throughout an insulating material, said insulating material forming a coating for a suitable substrate and/or comprising the substrate itself and having tenaciously adhered to said coating or substrate a conducting metal layer and/or a bright, ductile, electrolessly deposited metal.

This invention relates to novel and improved methods for metallizing insulating supports and to the products which result from such methods.

More particularly, the present invention relates to imposing by chemical means strongly adherent and rugged deposits of metal on insulating supports and to the products which result from such methods.

Although applicable whenever it is desired to strongly adhere a metal coating to an insulating base, as for example, for decorative efifect, or to make electrical conductors of a wide variety of shapes and configurations, the procedures for metallization disclosed herein are particularly useful for making printed circuits from cheap, low-grade, readily available electrical insulating base materials or base materials coated with electrical insulation materials,

This application is a continuation application of US. application Ser. No. 404,302, filed Oct. 16, 1964 and now abandoned, which application is a divisional application of US. application Ser. No. 218,656, filed Aug. 22, 1962, now U.S.P. 3,259,559, and is a continuation-in-part of co-pending applications Ser. No. 785,703, filed Jan. 8, 1959, now abandoned; Ser. No. 33 ,361, filed May 31, 1960 now U.S.P. 3,146,125; and Ser. No. 26,401, filed May 3, 1960 now U.S.P. 3,095,309.

It is a primary object of the present invention to provide improved chemical methods for imposing a uniform, rugged, firmly adherent, non-porous, bright and ductile deposit of copper on an insulating surface.

Another object of the invention is to provide chemical methods for imposing such a deposit of copper on irregularly shaped, complex, or curved insulating surfaces.

Still another object of this invention is to provide improved chemical methods for imposing a rugged and adherent conductor pattern on cheap, readily available insulating base materials A further object of this invention is to provide improved printed circuits which are rugged and durable, and which can withstand rough mechanical handling and heat shock.

Another object of this invention is to provide methods for making improved printed circuits in which the sup- 3,399,268 Patented Aug. 27, 1968 port for the circuits has improved insulating properties. An additional object of this invention is to transform cheap, insulating base materials into commercially attractive electrical conductive components by chemical means.

Other objects and advantages of the invention will be set forth in part herein and in part will be obvious herefrom or may be learned by practice with the invention, the same being realized'and attained by means of the steps, instrumentalities and combinations pointed out in the appended claims.

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.

The accompanying drawings referred to herein and constituting a part hereof, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. Although the invention will be described with particular reference to printed circuits, and although fabrication of printed circuits constitutes a primary and preferred application, it should be understood that the in vention is not limited to printed circuits but is applicable to metallizing insulating surfaces broadly.

Heretofore, it has been suggested to manufacture printed circuits by printing on an insulating backing a design of the circuit by means of various inks containing receptive particles and then electrolessly depositing a conductive material on the receptive particles.

Two main problems have been encountered in such a procedure. The first problem concerns the adhesion between the receptive particles and the base. Techniques previously described include seeding a base material with aqueous acidic solutions of precious metal ions such as palladium chloride. For example, the insulating material may be immersed in a bath comprising an aqueous acidic solution of stannous chloride and palladium chloride to render selected areas of the insulating material sensitive to the reception of an electroless metal deposit. Such sensitization baths, however, have many disadvantages. First and foremost, the adhesion between the precious metal deposit and the subsequently electrolessly deposited metal has been found to be tenuous. As a result, when the resulting circuits are subjected to rugged mechanical handling, or heat shock, such as by dip soldering, there is a tendency for the conductive layer to crack or pop free of the base, thereby disrupting the circuit. Additionally, such treating solutions are ponderous and expensive to employ, and must be carefully regulated if good results are to be achieved.

The second problem encountered in metallizing insulating bases by the technique under discussion resides in the electroless metal bath. Heretofore, a wide variety of electroless metal plating bath processes have been proposed for the deposition of thin layers of metal upon insulating surfaces, ceramics, plastics, and other materials. In general, none of these have been useful to any substantial degree for the electroless deposition of copper on metal surfaces. The prior art baths have produced copper deposits which are brittle, break under vibration and bending, and otherwise exhibit p'oor ductility, although many of the baths are commercially useful within recognized limits. Additionally, the deposits produced by most prior electroless copper depositing baths do not produce copper deposits which are bright. Rather, the

- deposits from conventional baths ordinarily exhibit a dull surface'of poor color. Frequently, the prior art baths yield a muddy layer of copper. Additionally, the baths of the prior art processes are often subject to instability, and impurities rapidly accumulate in the baths, the bath finally reaching a condition such that it spontaneously decomposes, throwing out copper as a useless precipitate.

' These and other disadvantages of the prior art are over-.

come by the present invention.

According to this invention, a process for metallizing insulating sufaces has been discovered which comprises providing an insulating base material with adhesively bound, finely divided, solid particles of an agent catalytic to the reception of electroless deposited metal, and then subjecting the resulting base material to a new and improved electroless copper bath to be disclosed.

When'the catalytic compositions and the electroless depositing baths described herein are employed in the manner and in the sequence to be described, there is produced onthe base material a dense, uniform, ductile, bright, conductive copper deposit which is firmly. and tenaciously adhered to the. base material or substrate. I a 'It is the combination of the catalyticcomposition to the electroless copper depositing baths disclosed herein that leads to the production of new and unexpectedly improved coatings of copper on an insulating base.

When the catalytic composition and the electroless copper depositing baths disclosed are employed in making printed .circuits, manyadvantages over the conventional commercial procedures are obtained. According to this process, copper is applied only where desired. No etching is required, and no copper is thrown away. The process is readily adaptable to mass production techniques, and miniaturized circiuts having firmly adherent conductive patterns are obtained. Additionally, the copper deposit forming the conductive pattern is ductile and bright, and its thickness can be controlled to close limits. The fact that the copper deposit is ductile is highly significant. Because of its ductility, the conductor pattern is strongly resistant to both mechanical and thermal shock and can readily withstand both rough mechanical handling and soldering, including dip soldering. Heretofore, so far as applicants are aware, it has not been possible to deposit a ductile copper layer using electroless techniques. Additionally, the process is economical and requires a minimum amount of control. Further, the copper deposit can be applied on practically any base material, regardless of size, shape or configuration, and can be subsequently readily coated or reinforced with other metals by electroless dip techniques or other procedures to impart special characteristics or properties to the circuits as a whole, or portions thereof.

A limiting factor in the production of printed circuits by the conventional print and etch technique is that the thickness of the foil, ordinarily produced by rolling copper, has a lower limit of about 0.7 to 1.3 mils. Frequently, for special purposes, it is desirable to have a conductor pattern which is less than 0.7 mil., i.e., in the order of about 0.1 mil. or even lower. With the techniques described herein, uniform layers of ductile copper having a thickness of less than 1.3 mils, or in the order of about 0.1 :mil to 7 mils, or even less, may readily be achieved.

The catalytic compositions forming a part of the present invention comprise an adhesive resin base having dispersed throughout finely divided particles of an agent which is receptive to electrolessly deposited copper.

The receptive agents dispersed throughout the resin base are cheap, readily available, particulate, finely divided metal or metal oxides, such as titanium, aluminum, copper, iron, cobalt, zinc, titanous oxide, copper oxide, and mixtures of the foregoing.

Particularly good results are achieved when the receptive agent is cuprous oxide and this material is preferred for use. Cuprous oxide is itself an exceptionally good insulator of electricity. Additionally, when reduced, as by treatment with an acid, the cuprous oxide may be changed to metallic copper to initially form the conducting portion of the desired printed circuit design which may then be further built up by electroless deposition by immersion or otherwise treating with the electroless copper depositing baths to be disclosed.

The'cataly tic compositions of the present invention may take a variety of forms.

For example, the insulating base members contemplated for use are most frequently formed of resinous material. When this is the case, the active agent disclosed herein, and especially'copper oxide, in finely divided, form, may be incorporated into the resin b ymilling, calendering,"or' other conventional methods after which the resin is set to form thebase. 4

Alternatively, thin film or' strip or unpolymerized resin having particles of the active agent suspended therein 'rnight belaminated to 21v resinous insulated base and 'cured' thereon. In this embodiment, the insulating base could be ;a resin impregnated laminate vof paper or cloth sheets orFiberglas.

In the preferred embodiment an ink comprising an adhesive resinous material having dispersed therein finely divided particles of the catalytic agent is printed on the surface of an insulating support andcured thereon.

Regardless of the manner in which it is incorporated in or on the base material, the catalytic agent is present in a finely divided form and preferably passes 200 mesh, US. Standard Sieve Series. Ordinarily from a small fraction of 1% to about of the active agent is admixed with adhesive resinous material to form the catalytic composition, but this concentration will depend to a large extent upon the materials used, and upon the time in which the catalytic compositions are allowed to remain in the electroless plating bath.

The resins into which the particles of the active material are dispersed preferably comprise, in combination, a thermosetting resin and a flexible adhesive resin. Typical of the thermosetting resins may be mentioned oil soluble phenolic type resins, such as fusible copolymers of phenol, resorcinol, a cresol, or a xylenol with an aldehyde or with furfural. Also may be mentioned the polyester resins, which are well known in the art and are prepared by reacting dicarboxylic compounds with dihydric alcohols, for example, by the reaction of phthalic or maleic anhydride with' mono-, di-, or polyethylene glycols. The polyester resins are ordinarily dissolved in styrene monomer and cross-linked by reaction with the styrene. As the thermosetting resin may also be mentioned epoxy resins, such as the reaction product of epichlorohydrin with bisphenol A. 7

Typical of the flexible adhesive resins are the epoxy resins, polyvinyl acetal resins, polyvinyl alcohol, polyvinyl acetate, and the like. Also as the adhesive-resin may be mentioned chlorinated rubber and butadiene acrylonitrile copolymers.

Theadhesive resins of the type described have appended thereto polar groups, such as nitrile, epoxide, acetal, and hydroxyl groups. Such adhesive resins copolymerize with and plasticize the thermosetting resins, and impart good adhesive characteristics through the action of the polar groups.

The thermosetting resin portion of the composition is required in order to afford resistance to heat upon soldering, and also to protect against decomposition when subjected to the electroless copper bath. A thermosetting resin alone, however, will not ordinarily have adequate tackiness or sufficient flexibility to resist heat shock; and

. would have negligent resistance to peeling of long conductor patterns from the surface. Admixture of adhesive resins such as those disclosed overcome the deficiencies of the thermosetting resins, and together, the thermosetting and adhesive resins provide an especially suitable composition for carrying the catalytic agents and for adhesively binding them to the base.

Particularly suitable for use as the adhesive resin for certain substrates is a combination of a phenolic type resin and an epoxy resin. The most common epoxy resins for use in the resinous composition are copolymers of epichlorohydrin (l-chloro-2,3-epoxy propane) with bisphenol A (2,'2,-p-hyd'roxy phen'yl propane) which have melting points within the range of 20 F. to 375 F. and molecular weights of about 350'to l5,000. 1

Although epichlorohydrinis the 'most important organic epoxide "employed in the formation of the epoxy resins, other epoxides such as,- for example,..1,2,3,4-dipeoxy butane .may be used. Similarly, epoxy resins derived from phenols other than bisphenol A are suitable for use. Such resins include, for.example, thereaction product of epichlorohydrin'with' resorcinol, with phenols derived from cashew. nut.oils, with hydroquinone, with 1,5.-dihydroxy vnaphthalene or with 2,2,5,5-tetrabis-(4- hydroxy phenyl) hexane. Phenolic intermediates of the resol type, hydrazines and sulfonamides, such as, for example, -2,4-toluene disulfonamide, may also be used for reaction with an organic epoxide to produce epoxy resins suitable for use. Aliphatic epoxy resins are also suitable. Such resins are, for example, the reaction product of epichlorohydrin with glycerol, withethylene glycol or with pentaerythritol. i

The phenolic type resin maybe a copolymer of a phenol, resorcinol, a cresol or a xylenol with an aldehyde or with furfural. Thus, it may be a copolymer of phenol or a substituted phenol with formaldehyde or a formaldehyde-yielding material, suchas, paraformaldehyde or hexamethylene tetra-amine, The phenolic resin is preferably of the oil soluble type. As examples of thermosetting phenolic type resins which may be used may be mentioned copolymers of formaldehyde with p-cresol, p-ethyl phenol, p-tert butyl phenol, p-tert amyl phenol, p-tert octyl phenol, p-phenyl phenol, di-isobutyl phenol, or a bisphenol, such as 4,4-isopropylidene diphenol or 2,2- bis (p-hydroxy phenyl) propane. It may be of the modified type, such as, for example, one which has been modified with copal or rosin to cause it to be oil soluble.

The phenolic type resins are, themselves, curing agents for the epoxy resins, and even those which are, themselves, permanently fusible form a tough, adherent film in combination with an epoxy resin which is probably the result of a cross-linking between the epoxy resin and the phenolic type resin. However, the resinous compositions may contain an additional curing agent. This curing agent maybe another resin, such as, for example, a polyamide resin or a melamine-formaldehyde resin, or it may be, for example, a dibasic acid, such as, for example, phthalic anhydride, an amine, such as, for example triethanolamine, diethylene triamine or metaphenylene diamine, or an amide, such as, for example, dicyandiamide.

When using a thermosetting type of phenolic resin, a curing agent for the phenolic, such as, for example, one of the'amines mentioned hereinabove as 'a curing agent for epoxy resin may be employed. 7

The active. agent it should be clear, is incorporated into the resinous compositions in such a way that the agent is dispersed throughout the resin, and present in the resin, jupon solidification, at numerous individual sites. Because of this dispersion, the particles of the receptive agents are not in contact with one another and accordingly, the catalytic compositions disclosed herein are non-conducting. Of course, when the active agent is itself non-conducting, such as cuprous oxide, or titanous oxide, this factor is not important. When metals such as copper, iron, and so forth, are employed as the active agent, however, the dispersion of the active particles throughout the resin becomes important. Were conducting particlesto be incorporated into the catalytic compositions in such a manner that they were in intimate contact with one another, it would be impossible to prepare printed circuits from such compositions using the socalled reverse, method. In this method, the catalytic composition would be adhered to the over-all surface of the base material or the base material would itself constitute' the catalytic composition, and selected portions thereof would then be masked, leaving exposed the conductor pattern. The base would then be immersed in the electroless copper bath to deposit copper on the exposed areas. Were the catalytic composition employed conductive, leakage would occur between the lines of the conductor pattern through the catalytic composition. Obviously, such a situation could not be tolerated.

When large amounts of the active agent are employed, as compared to the resin, relatively small amounts of resin bind the uppermost or surface particles of the active agent. Accordingly, electroless copper can readily deposit on the active agent on the surface. When small amounts of the active agent are employed in comparison to. the resin, e.g., 0.25 to 10% by weight, it may be that the active agent at the surface of the catalytic composition will be completely coated by the resinous material. In this situation, it may be necessary to abrade the surface ,so that the particles will be exposed to the electroless plating bath. If, in this situation no abrasion is used, it will be necessary to expose the surface to theelectroless plating bath for several hours before the initial copper deposit will form.

When copper oxide is used, it is preferable to activate the cuprous oxide by treatment with an acid, to convert at least a portion of the cuprous oxide particles at the surface of the ink to copper. Preferred for use is sulfuric acid. Other reducing agents which are acceptable include aqueous solutions of phosphoric acid, acetic acid, sulfuric acid, hydrofluoric acid, dithionates, hypophosphites, and the like. Nitric acid may also be used but it is not quite as desirable as the others since it dissolves the copper formed at a rather high rate. Alkaline formaldehyde solutions including the electroless copper baths disclosed herein will also reduce the cuprous oxide. 7

Among the wide variety of adhesives which may be used when it is desired to prepare the catalytic compositions in the form of inks are those compositions disclosed in US. Patent Nos. 2,532,374 and 2,758,953. In this embodiment, the receptive agent, as will be clear, is imparted into the adhesive base in such a way that the receptive agent is dispersed throughout the base medium, and present in the base medium at numerous individual sites.

Typical examples of catalytic inks suitable for use in printing conductor patterns on an insulating base are given below:

EXAMPLE 1 Xylene 50 Diacetone alcohol 75 Parlon l0 cps. 50 Phenol-formaldehyde (oil soluble) 10 Butadiene-acrylonitrile rubber 20 Cab-O-Sil 3 Cuprous oxide 70 Example 2 Butadiene acrylonitrile rubber 15.5 Diacetone alcohol 72 Nitromethane 72 Phenol-formaldehyde resin (oil soluble) 7.5 Cab-O-Sil 4 Ethanol 3 Parlon 10 cps. 10 Xylene 50 Cuprous oxide Example 3 Butadiene acrylonitrile rubber 15.5 Diacetone alcohol 50 Nitromethane 50 Phenol-formaldehyde resin (oil soluble) 7.5 Parlon 10 cps. 3 Toluene 20 Cab-O-Sil 3 Ethanol 3 Cuprous oxide 60 EXAMPLE 4 Butadiene acrylonitrile rubber 15.5 Diacetone alcohol 50 Nitromethane 50 Phenol-formaldehyde resin (oil soluble) 7.5 Cab-O-Sil 3 Ethanol 3 Cu'p'rous oxide 60 EXAMPLE 5 Toluene 50 Diacetone alcohol 50 Butadiene acrylonitrile rubber 10.5 Phenol-formaldehyde resin (oil soluble) 7.5 Parlon cps. 5 Ethane-1-..; 5 Cab-O-Sil 6 Cuprous oxide 50 EXAMPLE 6 Epoxy resin Butadiene acrylonitrile rubber 15 Diacetone alcohol 50 Toluene 50 Phenol-formaldehyde resin (oil soluble) 11 Cuprous oxide 60 In the above examples, Parlon is a chlorinated rubber from Hercules Powder Company. The epoxy resin of Example 6 is DER 332, sold by Dow Chemical Company, and is the reaction product of epichlorohydrin and bisphenol A. It has an epoxy equivalent of 173 to 179', an average molecular weight of 340* to 350 and a viscosity, at 25 C. of 3600 to 6400. Cab-O-Sil is a trade name for silica aerogel.

To prepare the coating compositions or inks disclosed in Examples 1 to 6, the resins are dissolved in the solvents and milled with the pigments on a three roll mill.

The viscosity of compositions having the formulae of Examples 1 to 6 will ordinarily vary between about 5 and 100 poises at C.

The catalytic inks may be applied to the panel in my convenient manner. For example, when a direct process for making printed circuits is employed, the circuit pattern of the ink may be imposed on the insulating base by screen printing or offset printing techniques. When the reverse process is employed, the insulating base may be coated with the catalytic ink, as by dipping, spraying, calendering, and the like, and then portions thereof masked to leave exposed the conductor pattern. When the catalytic inks are used to produce plated through holes, the ink may be drawn into the holes by vacuum. Alternatively, the pierced panels may be dipped into the inks, and then vibrated to remove excess ink from the holes.

After treatment of the panel with the catalytic ink, the adhesive base of the ink may be partially or fully cured by heating, thereby firmly bonding the adhesive ink with its contained receptive agent to the insulating base member.

The insulating base materials used to make the printed circuits must be able to withstand the temperatures which will be encountered in processing and in use. Preferable for use as insulating base materials are sheets of ceramic, phenol-formaldehyde, melamine-urea, vinyl acetate-chloride copolymer, rubber, epoxy resin polymers, epoxy impregnated Fiberglas, and the like.

After curing, the catalxtic ink may be lightly abraded by rubbing its surface with steel wool, sand paper or other abrasive material so that the receptive particles which make up the active sites are exposed. As indicated hereinabove, this step is not always necessary and depends to a large extent upon the exact nature of the adhesive composition employed in the ink and upon the concentration of the receptive particles in the ink.

Electroless plating baths preferred for use in the present invention consist essentially of a soluble copper s'alt (e.g., copper sulfate, cupric chloride, cupric nitrate, copper gluconate, cupric acetate, "and the like) g a complexing agent for the cupric ions (e.g., Rochelle salts;-ethylene diamine tetraacetic acid and its sodium salt; nitrolotriacetic acid and salts thereof; N-hydroxyethylethylenediamine triacetate; triethanolamine; sugar, including sucrose, dextrose, lactose, levulose or maltose; mannitol; sorbitol gluconic acid and the like); an alkali or alkaline earthmetal hydroxide, such as sodium. or potassium hydroxide; an active reducing agent such as formaldehyde; and a small amount of a complexing agent forcuprous ion, suchnas cyanide salts, e.g., sodium and potassium cyanide, acrylonitrile, lactonitrile, glyconitrile; thiourea, allyl alcohol, and ethylene. Preferred for use as the com plexing agent for cuprous ion are the cyanide salts, such as sodium and potassium cyanide, acrylonitrile, lactonitrile, and glyconitrile. t The quantities of the various ingredients in the bath are subject to wide variation, within-certainranges which may be defined-as follows: Y

Copper salt from 0.5 g. to saturated solution (0.002 to .15 mol. or more).

Alkali metal hydroxide to give pH 10.5 to 14.

Formaldehyde 0.06 to 3.4 mol.

Complexing agent for cupric ion 0.5 to 2.5 times moles of copper. Y

Complexing agent for cuprous ion (0.00002 mol. to

0.06 mol.).

Water-sufficient to make 1 liter.

The ratio of the copper salt to the complexing agent for cupric ion should be such that there are from 0.5 to 2.5 as many moles of cupric complexing agent as of copper, e.g., 5 grams of CuSO 5H O requires from 2.5 to 8.5 grams of Rochelle salts.

Sodium hydroxide and sodium cyanide are preferred over the corresponding more costly potassium and other alkali metal salts, which are of greater molecular weight.

Rochelle salts, the sodium salts (mono-, di-, tri-, and tetrasodium salts) of ethylenediaminetetraacetic acid, nitriltriacetic acid and its alkali salts, gluconic acid, gluconates, and triethanolamine are preferred as cupric ion complexing agents, but commercially available glucono-fi-lactone and modified-ethylenediamineacetates are also useful, and in certain instances give even better results than the pure sodium ethylenediaminetetraacetates. One such material is N-hydroxyethylethylenediaminetriacetate.

Cupric sulfate is preferred as the copper salt, but other soluble copper salts may be used, such as the nitrate, chloride and acetate.

In considering the general formulae for the electroless copper baths and the specific working formulae which are set forth below, it should be understood, that as the baths are used up in plating, the' cupric salt, and the formaldehyde reducing agent may be replenished from time to time, and also that it may be advisable to monitor the pH and cuprous iOn complexing agent content of the bath, and to adjust these to their optimum value as the bath is used.

The baths are ordinarily used at slightly elevated temperatures, such as from 35 to 65 C. although many of them may be used at even higher temperatures. As the temperature is increased, it is usual to find that the rate of plating is increased, and that the ductility ofthe deposit is increased to a slight extent, but the temperature is not highly critical, and within the usual operating range, excellent deposits are produced which exhibit greatly improved properties over those obtained with conventional baths.

With electroless copper plating baths used herein, the efiiciencyof copper recovered by electroless deposition from the bath often exceeds whichis much greater The cuprous ion complexing agent in the bath is anim? portant 'featureand serves to prevent or minimize the formation of cuprous oxide in the bath, and also appears to inhibit the formation of resulting hydrogen in the electroless deposited metal. Without the cuprous ion complexing agent, e.g., cyanide and the like, the bath has been found to be unsatisfactory as astable plating solution, and the electroless copper deposit has been found to be smudgy and of a poor appearance on the surface opposite the adhering base. Additionally, it has been discovered that without the cuprous ion complexing agent, a ductile deposit of electroless copper is not obtained. I

The baths to be described herein will ordinarily deposit a coating of electroless copper of a thickness of about 1 mil., withinbetween about 10 and 100 hours, depending on the composition, pH, temperature, and related factors.

Examples of the electroless copper depositing baths suitable for use will now be described.

EXAMPLE 7 Moles/l. Copper sulfate 0.03 Sodium hydroxide 0.125 Sodium cyanide 0.0004 Formaldehyde 0.08 Tetrasodium ethylenediaminetetraacetate 0.036 Water Remainder This bath is preferably operated'at a temperature v of about 55 C., and will deposit a coating of ductile electr o less cop'perabout 1 mil. thick in about 51 hours. 1

Other examples of suitable baths are as follows:

This bath is preferably operated at a temperature of about 56 C., and will deposit a coating of ductile electroless copper about 1 mil. thick in about 21 hours.

EXAMPLE 9 Moles/l. Copper sulfate 0.02 NaOH 0.125 NaCN 0.0002

HCHO 0.47 Rochelle salt 0.0425 Water Remainder EXAMPLE l- Moles/l Copper sulfate 0.04 NaOH 0.19

NaCN 0.0002

Rochelle salt 0.0425 HCHO 0.47 Water Remainder EXAMPLE 11 Moles/l. Copper sulfate 0.04 NaOH 0.19 NaCN 0.0006 HCHO 0.47 Rochelle salt 0.0425 Water Remainder 10 EXAMPLE 12 Moles/l. Copper sulfate 0.04 Sodium hydroxide 0.19 NaCN 0.0002 HCHO 0.47 Rochelle salt 0.064 Water Remainder EXAMPLE 13 Moles/l. Copper sulfate 0.02 NaOH 0.125 NaCN 0.0002 HCHO 0.40 Sodium citrate 0.051 Water Remainder EXAMPLE 14 v v v Moles/l. Copper sulfate 0.02 NaOH 0.05 NaCN 0.0002 HCHO 0.1 Trisodium N-hydroxy ethylenediaminetriacetate 0.024 Water Remainder The following examples are illustrative of the improved methods of :making printed circuits according to the teachings contained herein.

EXAMPLE 15 An insulating base is formed by uniformly mixing grams of Ciba 6005 which is the reaction product of bisphenol A and epichlorohydrin which has a viscosity of 4500 centipoises and an epoxy equivalent of and adding to it an equal weight of cuprous oxide which passes 200 mesh and milling with the pulverulent copper oxide particles for 1 to 2 minutes, which makes for a mixture which is relatively uniform. This uniform mixture is ready for immediate use or may be set aside for later use. It has an amine hardener, in this case 70 grams of diethylene triamine blended with it by constant turning, cutting and rubbing for about 2 minutes. It is then transferred to a mold by means of which it is given the shape desired. Heat may be applied to speed setting of the epoxy resin loaded with cuprous oxide particles so that the reaction is complete in a period of about one hour.

One surface of the insulating base thus formed is pro-' vided with a resist, portions of which have been removed, said portions masking out the circuit design which it is desired to form. An aqueous solution of 30 Baum sulfuric acid is then applied to the resist covered surface. The strength of the acid is not particularly critical and acid strengths of from 5 to 40 Baum have proven quite acceptable. The acid is allowed to remain in contact with the resist covered surface for 10 minutes. Contact of from 5 to 15 minutes is the usual period of time in which the cuprous oxide particles which are unprotected by the resist are reacted upon by the acid and converted to metallic copper. The acid is then removed by a thorough rinsing and the insulating base is then immersed in the electroless copper bath of Example 7 for about 51 hours. A uniform, adherent, bright, ductile cop per deposit about 0.001 inch thick was built up during this period of time. The deposit was tenaciously adhered to the base and could only be removed by scraping. The deposit could be readily soldered, both by dipping in a hot solder bath, and by hand soldering.

EXAMPLE 16 Since only the surface portion of the insulating base is acted upon during the contact with the acid it has proven desirable in some cases to take a cuprous oxide loaded resin and coat the surface of an insulating support with a lamina of such a composition and cure it thereon. A coating of epoxy resin-cuprous oxide as described in Example is applied to a clean urea-formaldehyde resin support to a depth of about of an inch and cured thereon. This depth may be varied on either side of that used here but of an inch is the most useful for any practical purpose. After curing this lamina thereby bonding it to the insulating base substance, the other steps of the process, i.e., masking, developing with acid and electrolessly plating, are carried out as in Example 15, and comparable results are obtained.

EXAMPLE 17 per deposits on the lateral sides surrounding the holes' as. well as on the circuit design. As will readily be apprech ated, this technique affords an extremely simple and facile method of making printed circuits with plated through holes.

The cuprous oxide loaded base of Example 15 also permits formation of printed circuits in a solid block of insulating material, as will be clear from the following examples.

EXAMPLE 18 A cylindrical block of cuprous oxide loaded resin was prepared following the procedure of Example 15. The surfaces of the cylindrical block are then covered completely with a resist. Holes are then drilled into the cylindrical block to form a pattern of interconnecting channels. Drilling the holes exposes the catalytic agent at myriad individual sites on the walls defining the holes. The cylindrical block is then treated with acid and immersed in the electroless copper bath, as described in Example 15. An adherent uniform, bright, ductile copper deposit is thereby formed on the lateral walls of the holes to form a printed circuit which is entirely encased in the cylindrical block.

If desired, of course, a circuit pattern could also be imposed on the exterior surfaces of the block. The conducting pattern on the surface could connect or not connect with the circuit in the interior of the block.

The importance of such a technique in forming microminiature circuits will readily be apparent to those skilled in the art.

In Examples 17 and 18, the solid block of material used to form the printed circuit could of course be any geometrical shape, such as spherical, tetragonal, hexaonal and the like.

EXAMPLE 19 Parts Phenol-formaldehyde resin (alcohol soluble) 60 Polyvinyl butyral resin 40 Ethanol 100 Cuprous oxide (powder, pass 200 mesh) 150 Powdered silica (methyl isobutyl ketone), sufficient to adjust viscosity to about 200 poises.

The resin-based ink circuit thus outlined is cured, bonding it to the resin insulating base. The cuprous oxide particles are reduced to metallic copper by means of contacting the cured resin-based ink containing cuprous ox- 1'2 ide particles with an acid and building up the circuit in the same manner as in Example 15.

If plated through holes are desired, these may be achieved by piercing the insulating base support prior to or following printing, and coating the lateral walls surrounding the holes with the catalytic ink, and curing. The panel is then treated with the acid an d then ,with the electroless copper bath to deposit copper on the con: ductor pattern andon'the lateral walls surrounding the holes. i V

. EXAMPLE 20 An adhesive containing a small amount of copper oxide (Cu O) is prepared as follows: j Y

Partsbyweight Butadiene-acrylonitrile copolymer 1 23- Phenol-formaldehyde resin 2 10 Zirconium silicate 107 Silica (20) 4 Cuprous oxide 0.5 Isophorone Xylene 31 1 Medium high acrylonltrlle content.

Combination of 5 parts oil soluble, heat reactive, solid resin, M.P. 144-162" F. and 5 ble, heat reactive. solid resin.

The rubber is dissolved in part of the solvents and the phenolic resin'dissolved separately in the rest of the solvents. The two solutions, cuprous oxide and the pigments are blended in a three roll paint mill. The circuit design is screen printed with the resulting ink on an epoxy-impregnated Fiberglas laminate and cured. The cured print of the circuit is immersed in 20 Baum sulfuric acid solution for 10 minutes. It is then removed, Washed free of sulfuric acid and immersed in the electroless plating bath described hereinabove. Again, plated through holes may be formed, if desired, using the procedure of Example 19.

EXAMPLE 21 The epoxy resin, cuprous oxide and pigments are blended together in a three roll paint mill, and the polyamide resin was warmed until readily workable and blended with the mixture from the mill by constant turning, cutting and rubbing for 5 minutes. The mix was cast in a mold and cured at 250 F. for 45 minutes. The fabrication of the printed circuit was carried out as in Example 1.

, EXAMPLE 22 Examples 15 to 21 are repeated with comparable results using finely divided particles of titanium, aluminum, copper, iron, cobalt, zinc and titanous oxide as the catalytic agent. With these agents, the acid treatment was not necessary. Best results were achieved when the catalytic composition was slightly abraded prior to exposure to the electroless copper bath.

EXAMPLE 23 Holes are drilled in a cylindrical block of acrylic resin having a diameter of 4 inch and a height of 1 inch. The holes are drilled at various angles and various direcparts alcohol soluble, oil so1u-.

tions so that they interconnect each other at selected positions, as shown, for example, in FIGURE 4.

v The holes are cleaned by treating with a mild alkaline cleaner, and then the holes are coated with the catalytic ink of Example 1. Residual ink is removed from the surface of the cylinder. The cylinder is then treated with acidand immersed in the electroless copper depositing bath.An adherent, bright, ductile copper deposit is formed on lateral walls surrounding the holes to form a printed circuit completely encapsulated with the cylinder of acrylic resin.

The particular amounts of catalytic agent shown as specific examples herein are operable, although the preferredamounts for obtaining a rapid electroless deposition while using a reasonable amount of catalytic agent is between and 20% by WeightLThe initial copper deposition obtained with these amounts occurs within about 2 to 10 minutes after immersion in the electroless plating bath.-

The following figures are included to illustrate the. major embodiments of the catalytic compositions disclosed herein. 7

FIGURE 1 shows an insulatnig base 1 which has randomly distributed throughout it particles of cuprous oxide 2; FIGURE 2 shows an insulating support 3 to which there has been laminated an insulating base 1 in which there is randomly distributed particles of cuprous oxide 2; 1 FIGURE 3 shows an insulating support 3 having applied on its surface particles of cuprous oxide 1 in the form of filler in an adhesive ink 4; FIGURES 4, 4a and 4b show an embodiment of a printed circuit in which the printed circuit pattern 6 is formed in holes'bored into a solid mass of an insulating material 8, as described in Example 24; and

. FIGURE 4 is an isometric view of the circuit and FIGURE 4a is a cross sectional View showing how the interconnecting circuit pattern 6 comprising the electroless copper deposit 10 runs through the insulating ma terial 8. FIGURE 4b is an enlarged cross sectional view of the conducting pattern of FIGURE 4a and depicts how the electroless deposited copper 10 is adhered to thecatalytic composition 12 which in turn is bondedto the lateral wall of insulating material 8 defining the apertlll'e 6. 1

,The FIGURES 1 to 3 show intermediate products resulting from the carrying out of the methods described in the. corresponding examples in the specification in that FIGURE 1 corresponds to Example 15, FIGURE 2 corresponds to Example 16 and FIGURE 3 corresponds to Example 19. FIGURES 4, 4a and 4b are schematic illustrations of the printed circuit produced according to the teachings of Example 23.

, As is, clear from the foregoing examples, the base materials on which the metal is deposited are capable of wide variation in composition and configuration. Among base materials to which the catalytic composition may be adhered may be mentioned impregnated laminates of paper or cloth, or even fiberglas. The resin impregnant for such laminates include phenolics, epoxies, polyesters, and the like. When impregnated laminates are used, it is desirable to pre-coat the laminates with a smooth plastic film prior to adhering the catalytic composition. As is also clear from the foregoing examples, the base materials may include molded plastic, such'as molded epoxy resin, polyester resin, epoxy resin, and the like. The base materials may even have incorporated therein the active agent for reception of the electroless copper deposit, as is clear from Example 15. In this embodiment, it is not necessary to separately adhere the catalytic composition to the base material, since the base material, itself forms the blank from which printed circuitsmay be made directly.

Still other possible base materials include lightweight synthetic materials well known to the building trade, such as wallboard, Masonite, Transite, and the like. Also may be mentioned anodized aluminum which has been sealed in a manner well known in the art to render the anodized coating insulating.

Also suitable for use as the base material are plastic coated metals, such as aluminum, anodized aluminum or steel coated with a resin. Such plastic coated metals are well known in the art, and are commercially available. They may be prepared either by dip coating, spray coating, or flame coating metal, substrates with a resin. Preferably, however, since smooth surfaces are desired, such metal resin coated laminates are prepared by fluidized bed techniques which are now well known in the art and described, for example, in U .8. Patent 3,028,251.

Suitable compositions for use in fluidized bed coating of a metal substrate with an insulating coating of a plastic material comprise a mixture of fusible epoxy resin and a fusible phenolic type resin. The compositions are in the form of free-flowing powders, which are fusible at an elevated temperature below the temperature at which the resin will be decomposed during the formation of the coating by fusion. Compositions in which the epoxy resin varies from about 10 to about based upon the total weight of the two resins, are preferred. The coating composition may contain other types of resins in addition to epoxy resin and phenolic resin, such as, for example, a polyester resin, a polyamide resin, a melamine formaldehyde resin or a natural resin, such as copal or rosin.

In the fluidized bed coating technique, finely divided solid particles of the resin composition are fluidized in a stream of gas, such as air, and a pre-heated article to be coated immersed in the fluidized bed for suitable periods of time. Following removal from the bed, the coated article is heated to fuse the coating. The particles of resin in the fluidized bed will ordinarly range in size from about 5 to 600 mesh, US. Standard Sieve Series.

The following examples illustrate methods of forming printed circuits using plastic coated metal base materials.

EXAMPLE 24 Fifty parts, by weight, of an epoxy resin formed by the reaction of bisphenol A with epichlorohydrin and characterized by an epoxide equivalent (grams of resin containing one gram equivalent of epoxide) within the range of 1550 to 2000, an equivalent weight or 190, a melting point of 127 C. to 133 C. and a particle size less than 40 mesh, fifty parts, by weight, of a phenolic resin produced by the reaction of phenol with formaldehyde and characterized by a softening point of F. to 220 F., a specific gravity of 1.2 and a particle size less than 40 mesh and two parts, by weight, of powdered silica having a particle size ranging from 1 micron to 7 microns were dry blended together.

A pierced and blanked aluminum plate having a thickness of 41 inch, a width of about 3 inches and a length of about 6 inches was heated to a temperature of 400 F. and while at that temperature immersed in a fluidized bed of the dry resin blend for a period of time ranging from A second to 2 seconds. Upon removal from the fluidized bed, the coated panel was maintained at a temperature of about 400 F. for a period of about 15 minutes to cure the coating which had been deposited thereon. Upon curing, the coating on the plate was found to vary from about 2 to 10 mils. in thickness, depending upon the time of contact in the fluidized bed. The coating was semi-gloss transparent and showed the natural color of the aluminum.

The coating extended through the plurality of holes in the panel. These holes had an original diameter of about 50 mils.

The resulting plastic coated aluminum was screen printed with the catalytic ink described in Example 2 to form a conductor pattern. The catalytic ink circuit thus outlined was cured to firmly bond it to the base.

The cuprous oxide particles in the catalytic ink were reduced to metallic copper by immersion in sulfuric acid following the procedure of Example 15. The panel was then immersed in the bath of Example 8 for a period of about 36 hours, thereby building up a printed circuit in the same :manner as in the previous examples.

Following electroless copper deposition, the panel was post cured by heating for about 2 hours at 130 C. In this embodiment, plated through holes may be readily formed by coating the lateral walls surrounding the holes with the catalytic ink prior to acid treatment and immersion in the electroless copper bath.

EXAMPLE 25 Example 24 is repeated with the exception that by weight of cuprous oxide having a'particles size of less than 200 mesh, U.S. Standard Sieve Series, based on the weight of the resin, was incorporated into the resinous composition prior to blending.

A pierced and blanked aluminum plate was anodized and coated with the resulting composition using the technique described in Example 24.

The plastic coating contained particles of cuprous oxide finely dispersed throughout. To form the printed circuit, the surface of the panel was coated with a masking composition which left exposed a conductor pattern and also the lateral walls surrounding the holes. The panel was then immersed in sulfuric acid having the strength of about for about 5 to 15 minutes to reduce at least a portion of the cuprous oxide to copper in the exposed areas of the conductor pattern and in the holes. The panel was then immersed in the electroless copper plating bath of Example 9 for about 75 hours, at the end of which time a firmly adherent, ductile, and bright electroless copper deposit had built up on the conductor pattern and on the lateral walls surrounding the holes.

In this example, the holes in the aluminum panel were coated by the fluidized bed technique, so that the holes actually had cuprous oxide particles adhered to the lateral sides of the holes. The wall surrounding the holes, in other words, following activation of the cuprous oxide with the acid, contained sites catalytic to electroless copper deposition. Accordingly, when the panel was submerged in the electroless copper bath, the Walls surrounding the holes also received a uniform adherent deposit of electroless copper.

As will be clear, the technique described in this example is suitable to make printed circuits on both sides of an insulating panel with plated through holes directly. Heretofore, great difficulty has been experienced in the trade in making plated through holes using electroless deposition techniques. The procedure outlined in Example 25 as well as certain of the other examples contained herein, represents a significant advancement in the art of making plated through holes.

If desired, special properties may be imparted to the copper conducting patterns produced as disclosed herein, as for example by depositing nickel, gold, silver, rhodium, and similar metals on the copper conducting pattern in whole or in part.

Typical nickel baths which may be used to deposit the additional metals are described in Brenner, Metal Finishing, 1954, pp. 68 to 76, and comprise acidic aqueous solutions of a nickel salt, such as nickel chloride; an active chemical reducing agent for the nickel salt, such as a hypophosphite; and a complexing agent, such as carboxylic acid and salts thereof. Suitable electroless gold plating baths which may be used to deposit additional metal are disclosed in U.S. Patent 2,976,181, and contain a slightly water soluble gold salt, such as gold cyanide, a reducing agent for the gold salt, such as the hypophosphite ion, and a chelating or complexing agent, such as sodium and potassium cyanide. The hypophosphite ion may be introduced in the form of hypophosphorous acid and salts thereof, such as sodium, calcium and ammonium salts.

It should be clear from the foregoing examples that when the embodiment using the adhesive resin is employed, printed circuits may be made by employing either the direct or.reverse printing technique. Also, following formation of the conductor pattern, the copper circuit can be dip soldered in whole or in part. If only portionsofthe circuit are to be dip soldered, a permanent or non-permanent solder mask may be used to coat the conductor pat: tern prior to dip soldering. Also, if desired, the conduct ing copper pattern, either in whole or in part, may receive an additional coating of metal, such as gold, silver, rhodium and the like, to impart special properties to the circuit as a whole or designated portions thereof.

It should also be clear fromthe foregoing that com; pleted circuits with plated through .holes can be readily and facilely made according to the techniquesdis'closed herein, including modifications of such techniques which will be obvious to those skilled in the art. 7

The invention in its broader aspects is not limited tothe' specific steps, methods, compositions and improvements shown and described herein, but departures may be made within the scope of the accompanying claims without de parting from the principles of the invention and without sacrificing its chief advantages.

What is claimed:

1. An article of manufacture comprising an insulating resinous base having dispersed throughout said base an agent catalytic to the reception of electroless metal, said insulating resinous base containing at least one hole, .said catalytic agent being exposed at the surface of the wall surrounding said hole and said base on the wall surrounding said hole having strongly adhered thereto a layer of electrolessly deposited metal.

2. An article of manufacture comprising an insulating resinous base having a metal layer adhered to at least one surface thereof and having dispersed throughout said base an agent catalytic to the receptionof electroless metal, said base containing at least one hole, said catalytic agent being exposed at the surface of the wall surrounding said hole, and said base on the wall surrounding said hole having strongly adhered thereto a layer of electrolessly de-, posited metal. I

3. An article of manufacture comprising an insulating resinous base having dispersed throughout saidbase an agent catalytic to the reception of electroless copper, said base containing at least one hole, said catalytic agent being exposed at the surface of the wall surrounding said hole, and said base on the wall surrounding said hole having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper.

4. An article of manufacture comprising an insulating resinous base having ametal layer adhered to at least one surface thereof and having dispersed throughout said base an agent catalytic to the reception of electroless copper, said base containing at least one hole, said catalytic agent being exposed at the surface of the wall surrounding said hole, and said base on the wall surrounding said hole having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper. h

5. An article of manufacture comprising an insulating resinous base having a copper layer adhered to at least one surface thereof and having dispersed throughout said base an agent catalytic to the reception of electroless copper,

said base containing at least one hole, said catalytic agent 1 being exposed at the surface of the wall surrounding said hole, and said base on the wall surrounding said hole having strongly adhered thereto a layer of bright, ductile,

electrolessly deposited copper.

' 6. A printed circuit board comprising an insulating resinous base having a metal layer adhered to at least one" surface thereof, and having dispersed throughout said base an agent catalytic to the reception of electroless metal, said base containing holes at points defining cross-overs be-* tween the top and bottom surfaces of the base, said catalytic agent being exposed at the surface of the walls surrounding said holes, and said base on the walls surrounding said holes havingstrongly adhered theretoa layer of electrolessly deposited metal. v f

7. A printed circuit board comprising: an insulating resinous base having dispersed throughout said base an agentcatalytic-to the reception of electroless copper, said base containing holes at points defining cross-overs between the topand bottom surfaces of the base, said catalytic agent being exposed at the surface of the walls surrounding said holes, and said base on the walls surrounding said holes having strongly adhered"theretoa'layerof bright, ductile, electrolessly deposited copper.

8. A printed circuit board comprising an insulating resinous base having a metal layer adhered to at least one surface thereof and having dispersed throughout said base an agent catalytic to the reception of electroless copper, said base containing holes at points defining cross-overs between the top and bottom surfaces of the base, said catalytic agent being exposed at the surface of the walls surrounding said holes, and said base on the walls surrounding said holes having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper.

9. A printed circuit board comprising an insulating resinous base having a copper layer adhered to at least one surface thereof and having dispersed throughout said base an agent catalytic to the reception of electroless copper, said base containing holes at points defining crossovers between the top and bottom surfaces of the base, said catalytic agent being exposed at the surface of the walls surrounding said holes, and said base on the walls surrounding said holes having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper.

10. A printed circuit board comprising an insulating resinous base having a resinous layer on at least one surface of said base, said base having dispersed throughout said base an agent catalytic to the reception of electroless copper, said resinous layer having dispersed therein an agent catalytic to the reception of electroless copper, said base containing holes at points defining cross-overs between the top and bottom surfaces of the base, said catalytic agent of said resinous base being exposed on the surface of the walls surrounding said holes, and said base on the walls surrounding said holes having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper.

11. A printed circuit board comprising an insulating resinous base having a resinous layer on at least one surface of said base, said base having dispersed throughout said base an agent catalytic to the reception of electroless metal, said resinous layer having dispersed therein an agent catalytic to the reception of electroless metal, said base containing holes at points defining cross-overs between the top and bottom surfaces of the base, said catalytic agent of said resinous layer being exposed on at least a portion of the surface of said layer, said catalytic agent of said resinous base being exposed on the surface of the walls surrounding said holes, said resinous layer on the surface where said catalytic agent is exposed having strongly adhered thereto a layer of electrolessly deposited metal, and said base on the walls surrounding said holes having strongly adhered thereto a layer of electrolessly deposited metal.

12. A printed circuit board comprising an insulating resinous base having a resinous layer on at least one surface of said base, said base having dispersed throughout said base an agent catalytic to the reception of electroless copper, said resinous layer having dispersed therein an agent catalytic to the reception of electroless copper, said base containing holes at points defining cross-overs between the top and bottom surfaces of the base, said catalytic agent of said resinous layer being exposed on at least a portion of the surface of said layer, said catalytic agent of said resinous base being exposed on the surface of the walls surrounding said holes, said resinous layer on the surface where said catalytic agent is exposed having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper, and said base on the walls sur- 18 t rounding said holes having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper. 13. A printed circuit board comprising aninsulating resinous base having a resinous layer on at least one surface of said base, said base having dispersed throughout said base an agent catalytic to the reception of electroless copper, said resinous layer having dispersed therein an agent catalytic to the reception of electroless copper, said resinous layer containing a mask leaving exposed an area outlining a printed circuit pattern, said base containing holes at points defining cross-overs between the top and bottom surfaces of the base, said catalytic agent of said resinous layer being exposed on the surface of said layer forming said pattern, said catalytic agent of said resinous base being exposed on the surface of the walls surrounding said holes, said resinous layer on the surface where said catalytic agent is exposed having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper, and said base on the walls surrounding said holes having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper.

14. A printed circuit board comprising an insulating resinous base having a resinous layer on at least one surface of said base, said layer forming a printed circuit pattern; said base having dispersed throughout said base an agent catalytic to the reception of electroless copper, said resinous layer having dispersed therein an agent catalytic to the reception of electroless copper, said base containing holes at points defining cross-overs between the top and bottom surfaces of the base, said catalytic agent of said resinous layer being exposed on the surface of said pattern, said catalytic agent of said resinous base being exposed on the surface of the walls surrounding said holes, said resinous layer having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper, and said base on the walls surrounding said holes having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper.

15. An article of manufacture comprising an insulating resinous base, having a resinous layer on at least one surface of said base said resinous layer having a copper layer adhered thereto, said resinous layer having dispersed therein an agent catalytic to the reception of electroless copper, and said base having dispersed throughout said base an agent catalytic to the reception of electroless copper.

16. A printed circuit board comprising an insulating resinous base having a resinous layer on at least one surface of said base, said resinous layer having a metal layer adhered thereto, said resinous layer having dispersed therein an agent catalytic to the reception of electroless copper, said base having dispersed throughout said base an agent catalytic to electroless copper, said base containing holes at points defining cross-overs between the top and bottom surfaces of the base, said catalytic agent being exposed at the surface of the walls surrounding said holes, and said base on the walls surrounding said holes having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper.

17. A printed circuit board comprising an insulating resinous base having a resinous layer on at least one surface of said base, said resinous layer having a copper layer adhered thereto, said resinous layer having dispersed therein an agent catalytic to the reception of electroless copper, said base having dispersed throughout said base an agent catalytic to electroless copper, said base containing holes at points defining cross-overs between the top and bottom surfaces of the base, said catalytic agent being exposed at the surface of the walls surrounding said holes, and said base on the walls surrounding said holes having strongly adhered thereto a layer of bright, ductile, electrolessly deposited copper.

18. A three-dimensional article comprising an insulating resinous base having dispersed throughout said base an agent catalytic to the reception of electroless metal, said base having interconnecting internal channels which define circuit patterns, said catalytic agent being exposed on the walls defining thev channels, ands aid base having on the walls defining the channels, where said catalytic agent i sjexpese'd, alayer' of lectrolessly deposited metal strong- 1y adhered the r e t o. I

I References Cited I UNITED STATES PATENTS 2,897,409 7/1959 Gitto 3177-101 2,943,956 j 7/1950 Robinson 1 17l 212 10 3,031,344 4/1962 She: etal. 117-212 3,134,690 5/1964 Eriks s'on 117- 213 3,165,672 1/1965. G ellert 317;100 3,202,591 I 8/1965. Curran. '204--38 3,119,709 I 1/1964 Atkinson -117+-47 2,690,401 9/19 54 Gut zeiteta1. 11747 2,690,403 9/1954 Gutzeit et a1. 117 47 3,171,756 3/1965 Marsha1l 117-212 WILLIAM L; JARyIS,-;Primary Examiner. s

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