GB2154251A - Sensitizing nonconductive substrates prior to electroless plating - Google Patents

Abstract

The substrate is sensitized by contacting it with an aqueous solution containing an effective amount of a bath soluble and compatible organic amine sensitizing agent of the structural formula: <IMAGE> wherein X, Y, Z, R1, R2, a, b and c are as defined in the specification eg. N-(3-chloro-2-hydroxypropyl)trimethyl ammonium chloride or (2,3-epoxy propyl)trimethy ammonium chloride. The sensitizing solution provides for an improvement in the coverage and adhesion of electroless platings on difficult-to-plate nonconductive substrates and provides for further advantages in flexibilty and waste disposal treatment over that provided by prior art sensitizers such as ethylenediamine.

Description

SPECIFICATION Treating nonconductive substrates prior to plating The present invention is broadly applicable to an improved composition and process for pretreating nonconductive substrates to render them receptive to a subsequent electroless metal plating step. More specifically, the present invention is directed to an improved sensitizing solution and process for pretreating certain nonconductive substrates to enhance their subsequent activation rendering them receptive to an electroless plating step providing a uniform and adherent metal deposit.

Avariety of compositions and processes have heretofore been used or proposed for use in applying metallic platings to all or selected portions of the surfaces of nonconductive substrates such as polymeric plastic parts. Typical of such plating processes are those described in United States Patent Numbers 3,622,370, 3,961,109, 3,962,497 and 4,204,013 to which reference is made for further background details to the process of the present invention. In accordance with such prior art processes, nonconductive substrates are conventionally subjected to a plurality of sequential pretreatment steps which generally include a cleaning step followed by a mechanical or chemical etching of the surface thereof to create the desired degree of roughness thereby enhancing the mechanical bond of the electroless metal plate subsequently applied thereto.The etched substrate is usually subjected to an activation treatment such as employing a tin-palladium complex containing solution whereafter the substrate is accelerated and after water rinsing, is subjected to a conventional electroless plating such as a copper or nickel electroless plating step. While the foregoing pretreatment sequence has been found eminently suitable for use in connection with a variety of nonconductive substrates including polymeric materials such as acrylonitrile-butadiene-styrene (ABS), polyaryl ethers, nylon, and the like, it has been found that certain nonconductive substrates such as glass, ceramics and modified polyphenylene oxide polymers cannot be adequately activated and the resultant electroless metal plate is nonuniform and/or discontinuous and is also characterized by very low metal to substrate adhesion. To overcome this problem in connection with such certain nonconductive substrates, it has heretofore been proposed to employ a "sensitizing" step prior to the activation step conventionally employing aqueous solutions containing ethylene diamine (EDA). It is in this context that the word "sensitizing" is used in this specification.While such sensitizing treatments have substantially improved the uniformity of the subsequent electroless metal plate and its adhesion to the substrate, EDA is somewhat corrosive and also causes waste treatment problems in discharging effluents because of its powerful complexing characteristics preventing appreciable precipitation of contaminating metal ions such as chromium, copper, nickel or the like by addition of alkaline substances prior to discharge.

The present invention overcomes many of the problems and disadvantages associated with such prior art sensitizing solutions and processes by employing a class of compounds which can be used in relatively lower concentrations to achieve the requisite sensitizing of the substrate prior to activation, which are less corrosive, which provide for improved adhesion of the subsequent electroless metal plate on the substrate, which are versatile in use and which facilitate waste treatment of effluents to precipitate contaminating metal ions.

The benefits and advantages of the present invention in accordance with the process aspects thereof are attained by sensitizing a cleaned and etched nonconductive substrate prior to activation by contacting the etched substrate with an aqueous solution containing a controlled amount effective to sensitize the substrate of a bath soluble and compatible organic amine sensitizing agent of the structural formula:

wherein:: each of X and Y independently represents -z, -Cl, -Br, -1,-OH or X andY taken together represents -O- or -S-; Z represents

AD represents Cl-, Br-, l-, OH-, SO4= or BF4-; each of R1, R2 and F3 independently represents H, or a (C1 -C4) alkyl, (C1-C4) alkenyl, (Ca-C4) alkynyl or (C-C4) hydroxyalkyl group; R4 represents an aryl or aralkyl group of up to 10 carbon atoms or R3;; F5 represents an R1 substituent or a carboxy or sulpho radical; a is O or 1; bisOor1; and c is an integer of from 1 to 5; or a mixture thereof.

The concentration of the sensitizing agent can range from about 1 to about 50 grams per litre (gil) with concentrations of about 2 to about 10 g/l being more usual. It is also contemplated that the solution can contain EDA in combination with the organic amine sensitizing agent of the present invention in amounts up to about 90 percent by weight of the total sensitizing agent present.

The sensitizing solution further contains hydroxyl ions to provide a pH within the range of about 7 to about 11 with a pH of about 8 to about 10 being more usual. The nonconductive etched substrate is contacted with the solution which is controlled at a temperature of about 600 to about 180"F (16" to 82DC), for a period of time generally ranging from about 15 seconds up to about 10 minutes or more, whereafter the sensitized substrate is water rinsed and thereafter transferred to the activation step in accordance with conventional practice. While the use of a wetting agent is not necessary in the practice of the present invention, small amounts of compatible wetting agents can be employed in certain instances to further enhance wettability of the substrate being sensitized.Agitation of the solution is optional and satisfactory results are usually obtained by simply immersing the substrate in the solution.

Additional benefits and advantages of the present invention will become apparent upon a reading of the following description of the preferred embodiments taken in conjunction with the specific examples provided.

The present invention is particularly applicable for the pretreatment of nonconductive substrates of the type which are not adequately catalyzed employing the conventional pretreatment cycle to achieve a subsequent uniform and adherent electroless metal plate. Among such nonconductive substrates are glass, certain ceramics and modified polyphenylene oxide polymers which in the absence of a sensitizing treatment, do not absorb or adsorb a sufficient quantity of catalyst on the surfaces thereof during the activation step to enable satisfactory plating thereof upon subsequent immersion in an electroless plating solution.

The sensitizing solution of the present invention contains as its essential constituent, a bath soluble and compatible organic amine of the structural formula given above.

Preferred sensitizing agents include: those in which each of X and Y independently represent -OH, -Cl, -Br, -I or -OH orX and Ytaken together represent -0-; those in which each of R1, R2, F3and R4 independently represents a hydrogen atom or a (C1-C4) alkyl group; those in which Z represents (R3)2R4.A; those in which Ae represents Cl-, Br-, or I-; andlorthose in which a, band care all equal to 1.

Particularly preferred organic amine sensitizing agents suitable for use in the practice of the present invention corresponding to the generic structural formula include N-(3-chloro-2-hydroxypropyl) trimethyl ammonium chloride or its epoxy form (2,3-epoxy propyl) trimethyl ammonium chloride and the hydrolyzation product of the epoxy form 2,3-dihydroxy propyl trimethyl ammonium chloride.

The foregoing sensitizing agent or mixtures thereof may be present in an amount of from about 1 up to about 50 girl, preferably from about 2 to about 10 g/l with concentrations of about 5 g/l being optimum. While concentrations of the sensitizing agent above 50 g/l can be employed, no appreciable benefits are achieved at such higher concentrations and the use of such higher concentrations is undesirable for economic considerations. Additionally, the use of such higher concentrations also increases waste treatment of the rinse effluents due to a complexing of metallic contaminating ions therein.

It is also contemplated that a portion of the organic amine sensitizing agent can be replaced with ethylene diamine (EDA) which can be employed in amounts up to about 90 percent by weight of the total sensitizing agent present, with concentrations of about 20 percent to about 80 percent by weight being preferred. When the organic amine sensitizing agent of the present invention is employed in combination with EDA, the concentration of the organic amine of the present invention can range from about 1 to about 40 gll with concentrations of about 3 to about 15 g/l being preferred and with a concentration of about 5 gil being particularly satisfactory.A particularly satisfactory composition comprises a sensitizing solution containing about 5 g/l of the organic amine of the present invention in combination with about 10 gil of EDA.

The operating bath is controlled at a pH ranging from about neutral (pH 7) up to about 11, preferably at a pH of about 8 to about 10, and with a pH of about 9 being particularly satisfactory. Appropriate adjustment and maintenance of pH of the solution can be achieved by the addition of an alkali metal hydroxide or ammonium hydroxide, of which sodium hydroxide is typical.

The use of a wetting agent or surfactant in the operating solution has not been found necessary but can be optionally employed in certain instances to increase the wettability of the substrate with the solution.

Generally, any bath soluble and compatible wetting agent can be employed in amounts up to about 5 g/l with concentrations of at least about 0.05 g/l being typical when used. The particular concentration of the wetting agent in the operating bath, when employed, will vary depending upon the specific type and the activity of the wetting agent used.

The sensitizing solution can be applied to a cleaned and etched nonconductive substrate by immersion, flooding or the like of which immersion is typical. While agitation can be employed to enhance surface contact, agitation ordinarily is not necessary to achieve satisfactory sensitization of the substrate. The duration of contact of the substrate with the sensitizing solution can range from as low as about 15 seconds up to about 10 minutes or longer, with times ranging from about 60 seconds to about 5 minutes being typical and adequate.

The operating solution may be controlled at a temperature ranging from about 60"F up to about 1800F (16 to 82"C) with temperatures of about 80" to about 130"F (27 to 54"C) being preferred. A particularly satisfactory temperature is about 1 000F (38"C) for most substrates.At temperatures below about 600F (1 6"C), some effectiveness may be lost in the sensitizing of the substrate whereas at temperatures generally above about 1800F (82"C) adverse effects can occur in connection with certain nonconductive substrates such as polymeric materials susceptible to warping at such high temperatures. Accordingly, the operating solution is preferably controlled within a range of about 800 to about 1300F (27" to 540C).

In accordance with the practice of the present invention, the nonconductive substrate is subjected to a conventional pretreatment prior to the electroless plating step such as described in United States Patent Number 4,204,013, the teachings of which are incorporated herein by reference. The parts to be plated are generally subjected to a cleaning treatment to remove any surface contamination which may include an organic solvent treatment in some instances to render the substrate such as polymeric substrates hydrophilic during a subsequent chemical etching step. The cleaning is usually performed employing an aqueous alkali soak solution followed by contact in an organic solvent medium which may comprise either a single-phase system or an aqueous-organic solvent emulsion.

Solvents have been used to condition ABS and polyphenylene oxide plastics in the decorative plating on plastics industry for many years as an optical means of promoting more efficient etching, and consequently acquiring enhanced plateability and adhesion characteristics. However, predonditioning is mandatory to effectively plate some plastics that require EMI shielding. For example, in the case of polycarbonate, solvent conditioning causes the plastic to become receptive to mineral acid etching which renders the plastic hydrophilic and creates bonding sites for subsequent electroless metal deposition. Solvent conditioning can also be used to reflow the surface skin of a plastic, such as foamed polystyrene, so that its surface has good cohesive strength. Mechanical abrasion can be used to condition most plastics that require conditioning.But chemical conditioning is preferred over more labour intensive mechanical abrasion techniques which are less cost effective and more difficult to automate.

The cleaned part is thereafter thoroughly water rinsed and is next subjected to an etching to provide surface roughness which enhances the mechanical bond of the substrate to the electroless metal plate. In the case of nonconductive substrates such as ceramic or glass, for example, the etching can be performed mechanically such as by abrading or sandblasting. In the case of glass, etching can also be effected by employing a hydrofluoric acid etching solution. For polymeric materials, a chemical etching is usually employed by subjecting the part to contact with an aqueous acid solution containing hexavalent chromium ions and acid such as sulphuric acid.The particular concentration of the etching solution, the temperature and duration of treatment will vary depending upon the particular type of nonconductive substrate being treated and, accordingly, the chemical etching can be performed in accordance with the procedures well known and practised in the art.

Following the etching step, the etched nonconductive substrate is usually rinsed and preferably is subjected to a neutralization step when a chromic acid etching solution has been employed to effect a reduction of any residual contaminating hexavalent chromium ions to the trivalent state. A typical neutralization treatment is described in United States Patent Number 3,962,497, the teachings of which are also incorporated herein by reference. Following neutralization, if employed, the substrate is again water rinsed and is then subjected to the sensitizing step in accordance with the practice of the present invention.

The sensitizing step has been found particularly satisfactory and necessary for pretreating polymeric substrates composed of modified polyphenylene oxide, polystyrene, polycarbonate, and polypropylene as well as nonconductive substrates including glass and ceramics. Following sensitizing, the part is again water rinsed and is next activated in an aqueous acid solution containing a tin-palladium complex of the various types well known in the art including those described in U. S. Patent Number 3,011,920 and U.S. Patent Number 3,532,518, the substance of which is incorporated herein by reference.

Following activation, the activated part is usually subjected to one or a series of water rinses whereafter it is subjected to an acceleration treatment in an aqueous solution typically containing a substituted alkyl amine, a mineral acid and a suitable reducing agent such as taught in United States Patent Number 4,204,013. Following acceleration, the part is again cold water rinsed and thereafter is subjected to an electroless plating step to apply a continuous and adherent metallic plating such as copper, nickel or cobalt over all or selected surface areas thereof.

It will be appreciated that when only selected areas of the nonconductive substrate are to receive a metallic plate, a suitable stop-off coating is applied to those areas following the cleaning step which are not to be plated. For this purpose, any of the commercially available stop-off compositions can be employed.

Following the electroless plating step, the part having the metal plate thereon can be subjected, if desired, to further conventional electroplating steps to provide a plural metallic plate on all or selected portions of the surfaces thereof in accordance with electrolytes of the various types known in the art.

While the sensitizing step in accordance with the practice of the present invention is only required with certain nonconductive substrates which cannot be satisfactorily plated without the use of such a sensitizing step, a further important feature of the present invention resides in the fact that, when such readily platable plastics were passed through the sensitizing solution, no adverse effect has been noticed on their subsequent electroless plating characteristics. This is particularly important when employing automatic processing lines wherein a variety of different nonconductive substrates are processed including some which do not require the sensitizing treatment.

In order to further illustrate the present invention, the following specific examples are provided. It will be understood that these examples are provided for illustrative purposes and are not intended to be limiting of the scope of the invention as herein described and as set forth in the claims.

Example 1 Aseries ofnonconductivetest panels of a nominal sizeof3" by about4" by 1110 (7.6cm x 10.2 cm x 0.25 cm) thick were subjected to a conventional pretreatment without employing a sensitizing step and subsequently were copper plated in an electroless copper solution. The test panels comprised a flame-retarded, foamed, modified polyphenylene oxide polymer commercially available under the designation Noryl PN-235 from General Electric Company. (The word "Noryl" is a trade mark).

After appropriate cleaning, the test panels are chemically etched in an aqueous acid solution containing 356 gll chromic acid, 412 g/l sulphuric acid and 0.02 g/l of a perfluorinated proprietary wetting agent commercially available under the designation FC-98 from Minnesota Mining & Manufacturing Company.

The panels are immersed for a period of about 5 minutes at 140"F (60"C) whereafterthey are water rinsed for 2 minutes at 140"F (60"C). The rinsed panels thereafter are neutralised in an aqueous solution containing 18 g/l hydrochloric acid, 3 g/l hydroxyl amine sulphate for a period of 5 minutes at 120"F (49"C) followed by a water rinse at 70"F (21"C) for a period of 1 minute.The panels are then activated for a period of 5 minutes at 1100F (43"C) in an aqueous acid solution containing 0.77 g/l palladium, 9 g/l tin chloride, 35.2 gil hydrochloric acid and 192 gll sodium chloride. The test panels are thereafter water rinsed for 1 minute at 70"F (21"C) and are subjected to an acceleration treatment for 1 minute at 750F (24"C) in a 5 percent by volume aqueous solution of fluoboric acid followed by a water rinse for 1 minute at 70"F (21"C).

The rinsed panels are thereafter subjected to an electroless copper plating for a period of 10 minutes at 140"F (60"C) employing an electroless copper solution containing 40 g/l ethylene diamine tetra-acetic acid tetra sodium salt, 4.2 g/l cupric chloride, 3 g/l formaldehyde, 10 mg/I sodium cyanide, and hydroxyl ions to provide a pH of about 12.2. The temperature of the solution is maintained at about 140"F (60"C) in the presence of air agitation.

An inspection of the test panels was made following the electroless copper plating step and an examination revealed that only about 50 percent of the surface area of each panel was plated with copper metal.

Example 2 The process as described in Example 1 was repeated employing similar test panels but a sensitizing treatment was interposed following water rinsing after the neutralization step and prior to the activation step. Sensitizing of the panels was performed for a period of 5 minutes at a solution temperature of 110"F (43"C) by immersion in a solution containing 50 g/l of (2,3-epoxy propyl) trimethyl ammonium chloride. The panels were thereafter water rinsed at 70"F (21"C) for 1 minute followed by the activation and electroless copper plating steps as described in Example 1.

Following the electroless copper plating step, an inspection of the panels revealed that 100 percent of the surface area of each panel was plated with copper metal.

Example 3 The pretreatment and electroless copper plating sequence as described in Example 1 commencing with the activation step was repeated employing a glass test panel. Following the electroless copper plating step, an inspection of the test panel revealed that no copper plate at all was on the surface of the glass panel.

Example 4 A glass test panel was processed through the same pretreating sequence and electroless copper plating step as described in Example 2 commencing with the sensitization step. Following the electroless copper plating step, an inspection of the panel revealed that 100 percent of the surface area thereof was plated with copper metal.

Examples 5-8 A series of comparative tests was conducted employing two different types of test panels. The first set comprised a flame retarded foamed modified polyphenylene oxide polymer of the same type as employed in the prior Examples commercially available underthe designation Noryl FN-215 from General Electric Company. The second set of panels comprised a solid flame retarded polymer designated as Noryl PN-190 also available from General Electric Company. The panels were subjected to the same pretreatment sequence employing the same solutions as previously described in Example 1 with the exception that a sensitizing solution was employed containing 50 gil of a sensitizing agent of the type as set forth in Table 1.

The treating sequence comprised a chemical etching for 1 minute at 1 55 F (68"C); water rinsing for 2 minutes at 70 F (21"C); neutralisation for 5 minutes at 120"F (49"C); water rinsing for 1 minute at 70"F (21"C); sensitising for 3 minutes at 1 250F (52"C); water rinsing for 1 minute at 70"F (21 C); activation for 5 minutes at 110"F (43"C); water rinsing for 1 minute at 70"F (21"C); acceleration for 1 minute at 75"F (24"C);; water rinsing for 1 minute at 70"F (21"C); electroless copper plating for 10 minutes at 140"F (60"C).

The resultant test panels were thereafter subjected to analysis for adhesion of the metal plate in accordance with the "Standard Method of Text for the Peel Strength of Metal Plastics" ASEP TP-200. The comparative adhesion expressed in pounds per inch and newtons per metre are set forth in Table 1 after a delay of two days following plating as well as a delay of one week following plating.

TABLE 1 Example Adhesion (Ib/in) Adhesion (Nlm) After After After After No. Plastic Sensitizer, 50 gil 2 days 1 week 2 days 1 week 5 Noryl PN-190 ethylenediamine 0.8 0.8 140 140 6 Noryl PN-190 (2,3-epoxy propyl) 1.3 2.5 228 438 trimethyl ammonium chloride 7 Noryl FN-215 ethylenediamine 2.0 4.5 350 788 8 Noryl FN-215 (2,3-epoxypropyl 3.5 7.0 613 1226 trimethyl ammonium chloride It is apparent from the data as set forth in Table 1, that the test panel according to Example 6 possessed superior adhesion both after 2 days as well as after 1 week in comparison to the test panel of Example 5 employing EDA in accordance with conventional practice.Similarly, the adhesion results of test panel 8 employing an organic amine sensitizing agent of the present invention provided for improved adhesion in comparison to the panels of Example 7 employing EDA as the sole sensitizing agent.

Examples 9- 12 A series of comparative tests were conducted employing different types and combinations of sensitizing agents utilizing polymeric test panels comprised of a plastic under the designation Noryl PN-235 available from General Electric Company. The test panels were subjected to a pretreatment sequence and electroless copper plating sequence employing the same solutions as described in Example 1 but further including a sensitizing treatment employing a solution containing the sensitizing agent at the concentration set forth in Table 2.The pretreatment and plating sequence comprised etching the test panels for 6 minutes at 155"F (68"C); water rinsing for 2 minutes at 700F (21"C); neutralising 2 minutes at 80"F (27"C); water rinsing for 1 minute at 70 F 21 C); sensitising 3 minutes at 80 F (27 C); water rinsing for 1 minuteat70 F(21 C); activation for 2 minutes at 900F (32"C); water rinsing for 1 minute at 70"F (21"C); accelerating 1 minute at 75"F (24"C); water rinsing 1 minute at 70"F (21"C); and electroless copper plating for 10 minutes at 140"F (60"C).

The resultant copper plated test panels were subjected to an adhesion test in accordance with the test panels of Examples 5-8 employing test method ASEP TP-200. The results are set forth in Table 2.

TABLE 2 Adhesion after 1 week Example No. Sensitizer (Ibs/in) KNlm) 9 5g/l 2,3-dihydroxy propyl 6.8 1191 trimethyl ammonium chloride 10 50 g/l ethylenediamine 5.5 963 11 lOg/lethylenediamine 7.1 1243 12 5 gel 2,3-dihydroxypropyl 9.0 1576 trimethyl ammonium chloride + 10 g/l ethylenediamine As noted in Table 2, the test panel of Example 9 containing only 5 g/l of an organic amine sensitizing agent in accordance with the present invention provided for substantially superior adhesion in comparison to the use of 50 g/l of EDA according to Example 10 which is conventional prior art practice.Example 12 is illustrative of the use of a combination of the organic amine sensitizing agents of the present invention in further combination with relatively low concentrations of EDA. The results as provided by Example 12 show a significant improvement in the adhesion of the plate after a period of 1 week following plating. Example 11 was run at the same time as Example 12, which was at a different time from Examples 9 and 10. Example 11 is therefore only comparable with Example 12 and not with Examples 9 and 10.

Example 13 In order to demonstrate the improved waste treatment of effluents derived from water rinsing of sensitized test panels, a comparative test was conducted employing EDA relative to 2,3-dihydroxy propyl trimethyl ammonium chloride. A typical EDA sensitizing solution was prepared containing 50 gll EDA which was diluted one-hundred fold to simulate a waste stream containing a net concentration of EDA of about 0.5 gull.

The diluted solution was of a pH of about 8.5. To the diluted solution 12.5 ppm chromium ions, 30.4 ppm copper ions and 20.1 ppm nickel ions were intentionally added as contaminating metal ions. Upon simulating a waste treatment of the solution, caustic soda was added to raise the pH to about 10 and following precipitation, the residual contaminating metal ion concentration in the treated solution was measured. It was found that the treated solution contained 2.6 ppm chromium ions, 28.4 ppm copper ions and about 19.2 ppm nickel ions. From the foregoing, it is apparent that substantially all of the copper and nickel ions were retained in the simulated rinse effluent while an 80 percent reduction in the chromium ion content was effected.

For comparative purposes, a sensitizing solution in accordance with the present invention was prepared containing 5 gll of 2,3-dihydroxy propyl trimethyl ammonium chloride in accordance with the conventional operating bath concentration which subsequently was diluted one-hundred fold to simulate a typical rinse effluent having a net concentration of the organic amine sensitizing agent of about 0.05 gull. To the diluted solution the same contaminating metal ions were intentionally introduced to provide a chromium ion concentration of about 12.5 ppm, a copper ion concentration of about 29.5 ppm and a nickel ion concentration of about 19.5 ppm. The contaminated solution was thereafter increased in pH from 9 to a pH of about 10 by the addition of sodium hydroxide and following precipitation, the residual contaminating ions present in the treated solution were analyzed. It was found that all of the chromium and nickel ions had been precipitated while the copper ion concentration was dramatically reduced from 29.5 to only 6.2 ppm.

While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope of fair meaning of the claims.

Claims (27)

1. A process for sensitizing a substrate comprising contacting the substrate with an aqueous solution containing an effective amount of a bath soluble and compatible organic amine sensitizing agent of the structural formula:

wherein: each of X and Y independently represents -Z,-CI, -Br, -I, -OH orX and Ytaken together represent -0or -S-; Z represents

Ab represents Cl-.Br-, l-, OH-, SO4= or BF4; each of R1, R2 and R3 independently represents H, or a (C-C4) alkyl, (C-C4) alkenyl, (C1-C4) alkynyl or (C-C4) hydroxyalkyl group; R4 represents an aryl or aralkyl of up to 10 carbon atoms or R3; R5 represents an R1 substituent of a carboxy or sulpho radical; aisOor1; b is O or 1; and c is an integer of from 1 to 5; our a mixture thereof.

2. A process as claimed in Claim 1, wherein in the structural formula X and Y independently represent -OH, -Cl, -Br, -I, or -OH orX and Ytogether represent -0-.

3. A process as claimed in Claim 1 or 2, wherein in the structural formula, each of R1, R2, R3 and R4 independently represents a hydrogen atom or a (C1-C4) alkyl group.

4. A process as claimed in Claim 1, 2 or 3, wherein in the structural formula Z represents --iBN(R3)zR4.A9.

5. A process as claimed in any one of claims 1 to 4, wherein in the stuctural formula Ae represents CI -, Br-, or 1-.

6. A process as claimed in any one of dims 1 to 5, wherein in the structural formula a, band care all equal to 1.

7. A process as claimed in any one of claims 1 to 6, in which the aqueous solution contains the organic amine in an amount of from 1 to 50 g/l.

8. A process as claimed in any one of claims 1 to 6, in which the aqueous solution contains the organic amine in an amount of from 2 to 10 g/l.

9. A process as claimed in any one of claims 1 to 6, in which the aqueous solution contains the organic amine in an amount of about 5 g/l.

10. A process as claimed in any one of claims 1 to 9, in which the aqueous solution contains ethylenediamine in combination with the organic amine.

11. A process as claimed in claim 10, in which the organic amine is present in an amount of from 1 to 40 g/l and the ethylenediamine is present in an amount up to 90 percent by weight of the combination.

12. A process as claimed in claim 10 in which the organic amine is present in an amount of from 3 to 15 g/l and the ethylenediamine is present in an amount of from 20 percent to 80 percent of the combination.

13. A process as claimed in Claim 10, in which the organic amine is present in an amount of about 5 g/l and the ethylenediamine is present in an amount of about 10 g/l.

14. A process as claimed in any one of claims 1 to 13, in which the temperature of the aqueous solution is kept in the range of from 60 to 1800F (16 to 820C).

15. A process as claimed in any one of claims 1 to 13, in which the temperature of the aqueous solution is kept in the range of from 80" to 1300F (27 to 540C).

16. A process as claimed in any one of claims 1 to 13, in which the temperature of the aqueous solution is kept at about 100 F (38 C).

17. A process as claimed in any one of claims 1 to 16, in which the pH of the aqueous solution is kept within the range of from 7 to 11.

18. A process as claimed in any one of claims 1 to 16, in which the pH of the aqueous solution is kept within the range of from 8 to 10.

19. A process as claimed in any one of claims 1 to 16, in which the pH of the aqueous solution is kept at about 9.

20. A process as claimed in any one of claims 1 to 19, in which the sensitizing agent comprises N-(3-chloro-2-hydroxypropyl) trimethyl ammonium chloride.

21. A process as claimed in any one of claims 1 to 20, in which the organic amine comprises (2,3-epoly propyl) trimethyl ammonium chloride.

22. A process as claimed in any one of claims 1 to 20, in which the organic amine comprises 2,3-dihydroxy propyl trimethyl ammonium chloride.

23. A process for sensitizing a substrate substantially as herein described with reference to any one of Examples 2,4,6,8,9, and 12.

24. A process for pretreating a nonconductive substrate to render the substrate receptive to subsequent electroless metal plating, the process comprising etching a clean substrate, sensitizing the etched substrate by a process as claimed in any one of claims 1 to 23 and then activating and accelerating the sensitized substrate.

25. A substrate which has been subjected to a process as claimed in any one of claims 1 to 24.

26. A process for electroless plating a nonconductive substrate which comprises the steps of providing a cleaned and etched nonconductive substrate, sensitizing the substrate by a process as claimed in any one of claims 1 to 23, rinsing the sensitized substrate, activating the substrate by contacting the surface(s) thereof with an aqueous acidic tin-palladium complex containing solution and thereafter sequentially rinsing, accelerating, rinsing and contacting the substrate with a composition comprising a source of metal to be deposited and a reducing agent to provide a metal plate of the desired thickness thereon.

27. An article having an electroless plated substrate provided by a process as claimed in claim 26.