GB2040969A

GB2040969A - Conditioning of Polyamides for Electroless Plating

Info

Publication number: GB2040969A
Application number: GB7938564A
Authority: GB
Original assignee: Crown City Plating Co
Current assignee: Crown City Plating Co
Priority date: 1978-12-19
Filing date: 1979-11-07
Publication date: 1980-09-03
Also published as: CA1143260A; IT7928067A0; DE2946343A1; DE2946343C2; JPS55112238A; FR2444691B1; GB2040969B; JPS633950B2; IT1164546B; FR2444691A1

Abstract

Polyamide substrates are preconditioned for electroless plating by contact with an alkaline aqueous solution having a pH of at least about 10 and etched with an acid solution. The acid solution is preferably an aqueous solution of an organic acid containing at least two carbon atoms, particularly an acetic acid compound, such as trichloroacetic acid.

Description

SPECIFICATION Conditioning of Polyamides for Electroless Plating Background of the Invention The present invention relates to electroless plating of polyamides, in particular, to providing a surface uniformly receptive to metals which catalyze electroless deposition of nickel and copper.

The benefits of electroless plated, non-conductive articles, particularly plastic articles, are well known. In the finished product, the desirable charadteristics of the plastic and the metal are combined to offer thereby the technical and aesthetic advantages of each.

Polymeric substrates are conventionally plated by preconditioning the surface by contact with an aqueous solution of at least one organic compound active for conditioning the surface of the plastic, etching with a strong oxidizing acid or base, seeding the surface with a noble metal catalyst, e.g., a palladium chloride solution, then immersing the seeded surface in an autocatalytic electroless solution where an initial coating of a conductive metal, e.g., copper or nickel, is established by chemical deposition. The metal deposit acts as a buss to allow a thicker coating of metal to be built up electrolytically.

Attempts to adapt conventional procedures for electroless plating of polymers to polyamides by us has resulted in a failure to achieve a uniform adherent coat of metal. Having found conventional electroless plating procedures ineffective, a quest was initiated to discover a procedure to enable uniform coating of polyamides with electroless deposited metals.

Summary of the invention It has now been found that electroless plating of polyamides, particularly filled polyamides, can be enhanced by first contacting the polyamide substrate with an aqueous alkaline solution having a pH of at least about 10, preferably a solution of at least one alkali metal hydroxide in which the alkali metal hydroxide content is from about 2 percent by weight to solution saturation, more preferably from about 10 to about 50 percent by weight. The alkaline solution is maintained at a temperature from about 1 500F to the lesser of the boiling point of the solution and the softening point of the plastic. Contact is for a time sufficient to enable etching by an acid solution.

The substrate is then contacted with an acid etch at ambient temperature or above. The concentration of the acid is sufficient to render the polyamide surface uniformly receptive to seeding by a metal catalyst. A preferred acid solution is a solution comprising at least one organic acid containing from two carbon atoms to about 10 carbon atoms and having a solubility in water of at least about 3 percent by weight of solution.

The presently preferred acid solutions are solutions comprising at least one acetic acid compound of the formula:

wherein each X is independently selected from the group consisting of hydrogen, hydroxyl and halogen.

Contact with the acid etch may be directly followed by seeding the surface with a metal electroless plating catalyst which are solutions of metal ions or suspensions of metal particles.

Following seeding and activation of the metal catalyst by conventional means, the surface can be uniformly plated with electroless copper or nickel.

Etching may be followed by rinsing debris from the surface of the substrate with an acid to alkaline rinse solution.

In carrying out the process of this invention in its preferred embodiment, an alkali metal hydroxide solution is used as the conditioner and is preferably employed at a temperature from about 1 70 to about 2000F at contact times ranging from about 0.5 to about 20 minutes or more, depending on temperature and caustic concentration. No damage has been found from prolonged contact.

Contact time in the aqueous acid solution etch is normally from about 10 seconds to 1 5 minutes at room temperature. When, as is presently preferred, a solution of an acetic acid compound is employed for etching the substrate, concentration is normally at least about 3 percent by weight up to solution saturation, preferably from about 5 to about 60 percent by weight.

In conducting the process of the invention, the article may be treated by contacting the article in an aqueous solution of an organic solvent for the polyamide, prior to or following contact with the alkaline solution. Alternatively, the organic solvent can be contained in the alkaline solution. The solvent in its solution is normally employed in a concentration up to about 2 percent by weight, preferably up to about 1 percent by weight. Ethylene glycol, phenolic compounds such as chlorophenol, cresols and salts thereof are presently preferred. As indicated, solvent may be contained in its own bath or included in the alkaline solution so long as the organic solvent is not hydrolyzed or degraded. The solvent serves to soften plastic to aid attack by the alkaline conditioner or acid etch.

As indicated, the substrate after etching may be further processed to remove the debris of etching by contact with acidic to basic wash.

Detailed Description According to the present invention, there is provided a process which enables uniform electroless deposition of metals onto polyamide substrates.

In particular, the processes of the present invention are directed to improvements in electroless plating of filled and unfilled polyamides such as Nylon 6 and Nylon 6,6.

In its broadest aspects, the invention is directed to conditioning the surface of a polyamide substrate with an aqueous alkaline solution having a pH of at least about 10 to render the surface receptive to attack by an acid etch.

Although solutions of alkali hydroxide are preferably employed, there may also be used alkaline compounds such as sodium metasilicate, trisodium phosphate, sodium carbonate and the like, used alone, in admixture and/or in combination with an alkali metal hydroxide.

When a conditioning solution of at least one alkali metal hydroxide is employed, the solution has an alkali metal hydroxide content of from about 2 percent by weight of solution to solution saturation, preferably about 10 to about 50 percent by weight.

The alkali conditioning solutions are, as presently employed,maintained at a tempeature from about 1 50"F to the lesser of the boiling point of the solution and the softening temperature of the polyamide.

Contact is for a time sufficient to render the substrate receptive to attack by the acid etch; and after rinsing, is followed by contact of the polyamide substance with an acid etch solution. The preferred acid solutions are solutions comprising at least one soluble organic acid containing at least two carbon atoms, and contact is for a time sufficient to render the surface receptive to a metal catalyst. The metal catalyst may be in the form of a solution of functional metal ions or as a dispersion of metal particles. It is presently preferred that the organic acid be an acetic acid compound as defined below.

As part of the process measures, water rinsing with deionized water is performed for good housekeeping between each step. The substrate may be treated with a dilute solution of solvent for the polyamide to soften the surface of the polyamide to promote conditioning and/or etch. Contact with the solvent may be prior to or after contact with the alkaline solution or contained in the alkaline solution. It is presently preferred to contact the substrate with the solvent following contact with the alkaline solution. If desired, a solution of the solvent may be employed prior to and following contact with the alkaline conditioner. The solvent softens the surface of the substrate to promote conditioning or etching. The solvent for the polyamide may be contained in a separate bath or part of the alkaline solution.

In addition, the substrates may be contacted with an acidic to basic solution subsequent to etch to remove debris present on the surface of the substrate.

The procedure of contact with the aqueous alkaline solution prior to contact with an acid etch is critical to the process of the invention and the reverse of steps normally conducted in electroless plating operations.

While reception of electroless plating onto the surface of any polyamide may be enhanced, the polyamides to be normally treated are filled polyamides as are conventionally used in molding operations. Typical of such materials are filled Nylon 6, Nylon 6,6 and the like.

The first essential step of the process is contacting the polyamide substrate with an aqueous alkaline solution. The presently preferred solutions are solutions of at least one alkali metal hydroxide, such as sodium and/or potassium hydroxide, present in a concentration from about 3 percent by weight of solution to solution saturation, preferably from about 10 to about 50 percent by weight.

Solution temperature is maintained from about 1 50"F to the lesser of the boiling point of the solution and the softening temperature of the polyamide substrate, preferably from a temperature of about 170 to about 2000F.

Contact time may vary from about 0.5 to 20 minutes or more, depending upon temperature and the alkaline compound concentration, although it has been found that prolonged immersions will not damage the substrate. The object is to condition the surface of the substrate to make it receptive to attack by the acid etch.

Following water rinsing to remove the alkaline conditioning solution, the article is passed to an acid etch, preferably one based on organic acids containing from 2 to about 10 carbon atoms and having a water solubility of at least about 3 percent by weight of solution. The presently preferred etch is one comprising from about 5 percent by weight to about 65 percent by weight of solution and more preferably, from about 10 to about 25 percent by weight of solution of at least one acetic compound of the formula:

where each X is independently hydroxyl, hydrogen or halogen with halogen preferred.

Contact is at ambient or room temperature although elevated temperatures may be employed.

Contact times range from about 10 seconds to 1 5 minutes or more and are for a time sufficient to etch the surface of the polyamide to a degree that it becomes uniformly receptive to seeding by a metal catalyst.

Among the acetic acid compounds which may be used there may be mentioned trichloracetic acid, acetic acid, hydroxyacetic acid, dichloracetic acid, chloracetic acid, fluoracetic acid, difluoracetic acid, trifluoracetic acid, bromacetic acid, dibromacetic acid and the like. Trichloroacetic acid is presently preferred.

Optionally, there may be employed as part of the process, contact with an organic solvent for the polyamide. The solvent may be in a separate bath used preceding and/or following the alkaline conditioning solution or included in the alkaline conditioning solution. The organic solvent softens the surface of the substrate to aid attack by the conditioning and/or etching solutions. Typically, concentration of the solvent in its solution is up to about 2 percent by weight, preferably up to about 1 percent by weight. A wide variety of solvents for polyamides may be used. The presently preferred solvents are ethylene glycol, chlorophenol, cresols and salts thereof. If employed in the alkaline conditioner as its solution, the solvent should not be hydrolyzed or degraded by the alkaline batch.

In addition, subsequent to contact with the acid etch, the substrate may be brought into contact with an acid to alkaline solution of either an organic or inorganic acid or base to cleanse the surface of debris, i.e., filler and/or degradated resin. Such solutions are normally maintained at room temperature, although elevated temperatures may be employed. Although solutions used as the conditioner may be employed, solutions having an acidic or alkaline compound in concentration in the range up to about 20 percent by weight, preferably up to about 10 percent by weight may also be employed. Functional acids include hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, formic acid, acetic acid and the like. As indicated, there may also be used as a convenience to minimize the number of baths involved, the alkaline solution used for conditioning the substrate.Alternative solutions include such as solutions of borax, ammonium bifluoride and the like. The concentration is that which will enhance surface finish without detracting from the ability of etched surface to accept a metal catalyst.

Whether or not the cleansing treatment is employed, the article is rinsed in water, usually deionized water, and seeded with a metal electroless plating catalyst.

The electroless plating catalysts employed may be noble metal or non-noble metal based. Nonnoble metal catalysts are described in U.S. Patent 3,958,048 to the same assignee as this application and incorporated herein by referencing.

A noble metal catalyst in an aqueous medium is presently preferred. By a "noble metal catalyst contained in an aqueous medium" there is meant an ionic solution or colloidal suspension of the free metals. Colloidal suspensions are preferred. The noble metals include gold, platinum and palladium, with palladium preferred.

A suitable ionic bath is one containing palladium chloride in a concentration of about 0.2 grams per liter solution and 3 ml of concentrated hydrochloric acid per liter of solution. Following seeding, the palladium can be reduced to the free metal state by immersion in a bath of a reducing agent such as dimethyl amine borane.

Colloidal suspensions of noble metals are described in U.S. Patent 3,011,920 to C. R. Shipley, Jr., incorporated herein by reference. Such suspensions are colloidal in nature in which the noble metal colloid is maintained in suspension by a protective colloid, i.e., stannic acid colloids. Following seeding, the colloid is removed by immersion in an acidic or alkaline accelerator solution to remove the protective colloid and expose the absorbed noble metal.

Although less preferred, there may also be employed a seeding method which involves contacting the etched article with a sensitizing solution containing stannous chloride followed by immersion in an activator solution such as a palladium chloride solution where the ionic palladium is reduced to the free metal on the surface of the substrate.

Suitably activated, the article may be electrolessly plated by conventional means. Electroless copper and nickel formulations, such as those described in U.S. Patents 3,011,920 and 3,874,072 incorporated herein by reference, may be employed. Electroless copper solutions are typically based on a soluble copper salt, such as copper sulfate, a complexing agent for the cupric ion such as Rochelle salt, an alkali hydroxide for adjustment of pH, a carbonate radical as a buffer and a reducing agent for the cupric ion such as formaldehyde.

Following electroless plating, the substrate may be electrolytically plated by conventional means, with nickel, gold, silver, chromium and the like to provide the desired finish on the article. It has been observed that adhesion will increase with age of the plate.

In the following Examples and Controls where the article or substrate was contacted with an alkali hydroxide solution, the bath was about 35 percent weight to volume sodium hydroxide solution maintained at 2000F. Where contacted with a hydrochloric acid solution, the solution was a 28.5 percent (volume by volume) of concentrated hydrochloric acid in water. The solution of trichloracetic acid (TCA solution) employed was a 20 percent by weight to volume aqueous solution maintained at room temperature. Seeding of the etched substrate was with a ,proprietary colloidal tin-palladium catalyst as described in U.S. Patent 3,011,920 at an acid molarity of about 1.7.An alkaline accelerator was used to expose the palladium metal The catalyst was maintained at about 1 200F and the accelerator at about 1 050F. The electroless copper solution employed was Cuposit(TM PM-990 manufactured and sold by the Shipley Company. The electroless copper solution was maintained at ambient temperature.

Following electroless plating, the article was electrolytically plated when possible. In this operation, the substrate was rinsed in deionized water, soaked in an alkaline cleaner, then passed to a reverse current cleaner, an acid dip, bright acid copper and nickel electrolytic plating solutions and finally to a chromium plating solution.

Some plated articles were subjected to cycle testing to determine adhesion performance under thermal stress conditions. In this test the plated article was maintained at a temperature of at least 1 800F for 1 hour, then cooled to room temperature and maintained at room temperature for 30 minutes then cooled to -200F and maintained at that temperature for 1 hour.

Example 1 A plating grade of filled Nylon 6,6 known as Vydyne(TM) RP-260, manufactured and sold by the Monsanto Company, was immersed for 10 minutes in the alkali hydroxide solution then water rinsed and immersed for 1 minute in the TCA solution. The article was then rinsed in water, catalyzed, rinsed, electrolessly plated with copper and electrolytically plated. Initial plate adhesion ranged from 1.0 to 1.5 Ib/in with an average of 1.3 Ib/in. The cycle test was successful.

Control 1 The procedures of Example 1 was reversed in that the article was immersed in the TCA solution prior to contact with the alkali hydroxide solution. This resulted in skip plating and blistering of the electroless plate.

Control 2 Control 1 was repreated except that immersion time in the TCA solution was increased to 5 minutes. The electrolessly deposited plate blistered.

Control 3 Example 1 was repeated except that immersion in the TCA solution was omitted. This also resulted in blistering of the electroless plate.

Example 2 Example 1 was repeated except that the article after contact with the TCA solution was reimmersed in the caustic solution for 10 minutes to cleanse the surface. There was obtained uniform coverage of the electroless and electrolytic plate. Initial adhesion ranged from 1.5 to 1.8 Ib/in with an average of 1.7 Ib/in. The cycle test was successful.

Example 3 Example 1 was repeated except that immersion in the TCA solution was for 2 minutes followed by immersion in a hydrochloric acid solution for 1 minute. The article uniformly plated with electroless copper and was electrolytically plated. Initial adhesion of the plate ranged from 1.3 to 1.8 Ib/in with an average of 1.5 Ib/in. The cycle test was successful.

Control 4 In this test Example 1 was repeated except that the Vydyne article was immersed in the hydrochloric acid solution for 1 minute, rinsed, then immersed for 1 minute in the TCA solution and again for one minute in the hydrochloric acid solution. Small blisters developed in the electroless plating operation with extensive blistering occurring in the reverse current cleaning step preceding electrolytic plating such that the article could not be electrolytically plated.

Control 5 An article molded of Vydyne(TM RP-260 was immersed in the hydrochloric acid solution for 1 minute, rinsed for 1 minute in the TCA solution, followed by 10 minutes in the caustic solution but at a reduced temperature of 1600 F. The electroless plate exhibited small blisters with large blistering occurring in the reverse current cleaner.

Example 4 An article molded of VydynelTM) RP-260 was immersed for 10 minutes in the caustic solution, rinsed, immersed for 1 minute in the TCA solution and for 5 minutes in a cleaner which was a 50 percent volume by volume solution of glacial acetic acid in water at room temperature. The article accepted the electroless and the electrolytic plates. Initial adhesion averaged 1.2 Ibs/in.

Example 5 An article molded of Capron(TM) XPN-1 030, a filled Nylon 6 manufactured and sold by Allied Chemical Corporation, was immersed in the caustic solution for 10 minutes, rinsed, then immersed in a 10 percent volume by volume solution of dichloracetic acid for 5 minutes. The article accepted uniform electroless and electrolytic plates.

Example 6 Example 5 was repeated except that immersion in the dichloracetic solution was for 2 minutes at 1200 F. The same results were obtained.

Example 7 An article molded of Vydyne(TM) RP-260, following immersion in the alkali hydroxide solution as described in Example 1, was immersed for 1 5 seconds in a 90 percent aqueous acetic acid solution at room temperature. The etched article accepted an adherent deposit of electroless copper, then adherent electrolytic plates of copper, nickel and chrome.

Example 8 The procedure of Example 1, was repeated except that the trichloracetic acid concentration was reduced to 10 percent by weight to volume. Immersion was for 1 minute. The etched article accepted uniform adherent deposit of electroless copper, an electrolytic plate of copper, nickel then chrome.

Example 9 The procedure of Example 8, was repeated except that the polyamide substrate was Capran XPN-1 030. The results were equally successful.

Example 10 A substrate molded Minlon(TM) 11 -C-40, a nylon manufactured and sold by DuPont, was immersed in a 2 percent by volume solution of cresylic acid in a 5 percent by weight volume aqueous solution of sodium hydroxide, maintained at 1300for 5 minutes, then immersed in the alkali hydroxide solution maintained at 2000F for 10 minutes and for 1 minute in a 15 percent weight by volume aqueous solution of trichloracetic acid. The etched article accepted upon catalysation a uniform electroless plate of copper and an electrolytic plate of copper, nickel then chrome and passed the cycle test. Adhesion ranged from 2 to 3 pounds per inch.

Example 11 There was employed an unfilled nylon substrate formed of Capron(TM) 8202 F-Type 6 manufactured and sold by Allied Chemical Corporation. The .substrate was contacted with the caustic solution for 5 minutes at 2000F, then with the TCA solution for 1 minute at ambient temperature, followed by re-contact with the caustic solution for 5 minutes. The etched substrate accepted uniform electroless and electrolytic plates.

Controls 7 to 9 In tests on Vydyne where contact with the alkali hydroxide solution was used for 5 to 10 minutes contact, failures occurred in the organic solutions and conditions identified below.

Test Solution Control (Conc., Temp., Contact time) Nature of Failure 7 Dichloropropanol (15% v/v, Massive blistering 1 500F, 1.5 min) in cycle test 8 Dichloropropanol (15% v/v, Blistered severely 1 500 F, 1.5 min) in reverse current 9 Formic acid (45% v/v, Blistered in pre-plate R.T., 1 min)

Claims

1. A process for electroless plating of polyamide substrate wherein the substrate is etched with an acid prior to electroless plating, the improvement which comprises conditioning the substrate prior to etch by contact with an aqueous alkaline conditioning solution having a pH of at least about 10 and maintained at a temperature of from about 1 500F to the lesser of the boiling point of the solution and the softening temperature of the polyamide substrate for a time sufficient to enhance acid etch of the polyamide substrate.

2. A process as claimed in Claim 1 in which the polyamide substrate is contacted with the conditioning solution for a period of from about 0.5 to about 20 minutes.

3. A process as claimed in Claim 1 in which the polyamide substrate is contacted, prior to contact with the conditioning solution, with a dilute aqueous solution of an organic solvent for the polyamide for a time sufficient to soften the surface of the polyamide substrate.

4. A process as claimed in Claim 1 in which the polyamide substrate is contacted following contact with the conditioning solution, with a dilute aqueous solution of an organic solvent for the polyamide for a time sufficient to soften the surface of the polyamide substrate.

5. A process as claimed in Claim 1 in which the conditioning solution contains an organic solvent for the polyamide.

6. A process for preparing the surface of polyamide substrates for electroless plating which comprises: (a) forming a conditioned polyamide substrate for etching by contacting the polyamide substrate with an aqueous alkaline conditioning solution having a pH of at least about 10 and maintained at a temperature from about 1 500F to the lesser of the boiling point of the solution and the softening temperature of the polyamide substrate for a time sufficient to render the substrate receptive to etch by an organic acid;; (b) etching the conditioned polyamide substrate by contacting the conditioned polyamide substrate with an aqueous etch solution comprising at least one water soluble organic acid containing from 2 to about 10 carbon atoms in the molecule and present in the aqueous solution in a concentration of at least about 3 percent by weight of the solution and sufficient to render the conditioned polyamide substrate substantially uniformly receptive to a metal electroless plating catalyst.

7. A process as claimed in Claim 6 in which the polyamide substrate is cleansed prior to contact with the metal catalyst by contact with an aqueous acidic or basic cleansing solution.

8. A process as claimed in Claim 6 in which the polyamide substrate is contacted, prior to contact with the conditioning solution, with a dilute aqueous solution of an organic solvent for the polyamide for a time sufficient to soften the surface of the polyamide substrate.

9. A process as claimed in Claim 6 in which the polyamide substrate is contacted following contact with the conditioning solution, with a dilute aqueous solution of an organic solvent for the polyamide for a time sufficient to soften the surface of the polyamide substrate.

10. A process as claimed in Claim 6 in which the conditioning solution contains an organic solvent for the polyamide.

11. A process for preparing the surface of polyamide substrates for electroless plating which comprises: (a) forming a conditioned polyamide substrate for etching by contacting the polyamide substrate with an aqueous conditioning solution of at least one alkali metal hydroxide in which the alkali metal hydroxide concentration of the solution is from about 2 percent by weight of the solution to solution saturation and maintained at a temperature of from about 1 500F to the lesser of the boiling point of the solution and the softening temperature of the poiyamide surface for a time sufficient to render surface polyamide substrate receptive to etch by an acetic acid compound;; (b) etching the conditioned polyamide substrate by contacting the conditioned polyamide substrate with an aqueous acid etch solution comprising at least one acetic acid compound having the formula:

wherein each X in independently selected from the group consisting of hydrogen, hydroxyi and halogen and in which the acetic acid compound concentration is sufficient to render the conditioned polyamide substrate receptive to a metal electroless plating catalyst.

12. A process as claimed in Claim 11 in which the polyamide substrate is cleansed prior to contact with the metal catalyst by contact with an aqueous acidic or basic cleansing solution.

1 3. A process as claimed in Claim 11 in which the polyamide substrate is contacted, prior to contact with the conditioning solution, with a dilute aqueous solution of an organic solvent for the polyamide for a time sufficient to soften the surface of the polyamide substrate.

14. A process as claimed in Claim 11 in which the polyamide substrate is contacted following contact with the conditioning solution, with a dilute aqueous solution of an organic solvent for the polyamide for a time sufficient to soften the surface of the polyamide substrate.

1 5. A process as claimed in Claim 11 in which the conditioning solution contains an organic solvent for the polyamide.

1 6. A process as claimed in Claim 1 5 in which the organic solvent is an alkali soluble organic snlvAnt.

17. A process as claimed in Claim 11 in which the polyamide substrate is formed of a filled polyamide.

18. A process as claimed in Claim 11 in which the total alkali metal hydroxide content of the conditioning solution is from about 10 to about 50 percent by weight of the solution.

19. A process as claimed in Claim 11 in which the conditioning solution is maintained at a temperature from about 170 to about 2000F.

20. A process as claimed in Claim 11 in which the contact time in the conditioning solution is from about 0.5 to about 20 minutes.

21. A process as claimed in Claim 11 in which the total acetic acid compound concentration of the etch solution is from about 3 percent by weight to solution saturation.

22. A process as claimed in Claim 11 in which the total acetic acid compound concentration of the etch solution is from about 5 to about 60 percent by weight of the solution.

23. A process as claimed in Claim 11 in which the polyamide substrate is contacted with the etch solution for a period of from about 10 seconds to about 1 5 minutes.

24. A process as claimed in Claim 11 in which the acetic acid compound is trichloracetic acid.

25. A process as claimed in Claim 11 in which the acetic acid compound is dichloracetic acid.

26. A process as claimed in Claim 11 in which the acetic acid compound is acetic acid.

27. A process for preparing the surface of polyamide substrates for electroless plating which comprises: (a) forming a conditioned polyamide substrate by contacting the polyamide substrate with an aqueous conditioning solution of at least one alkali metal hydroxide in which the total alkali metal hydroxide concentration is from about 10 percent by weight of the solution to solution saturation and maintained at a temperature of from about 1 500F to the lesser of the boiling point of the solution and the softening temperature of the polyamide surface for a period of from about 0.5 to about 20 minutes;; (b) forming an etched polyamide substrate by contacting the conditioned polyamide substrate with an aqueous etch solution comprising at least one acetic acid compound selected from the group consisting of trichloracetic acid, dichloracetic acid and acetic acid in which the acetic acid compound concentration is sufficient to render the conditioned polyamide substrate receptive to a metal electroless plating catalyst.

28. A process as claimed in Claim 27 in which the polyamide substrate is cleansed prior to contact with the metal catalyst by contact with an aqueous acidic or basic cleansing solution.

29. A process as claimed in Claim 27 in which the polyamide substrate is contacted, prior to contact with the conditioning solution, with a dilute aqueous solution of an organic solvent for the polyamide for a time sufficient to soften the surface of the polyamide substrate.

30. A process as claimed in Claim 27 in which the polyamide substrate is contacted following contact with the conditioning solution, with a dilute aqueous solution of an organic solvent for the polyamide for a time sufficient to soften the surface of the polyamide substrate.

31. A process as claimed in Claim 27 in which the conditioning solution contains an organic solvent for the polyamide.

32. A process as claimed in Claim 31 in which the organic solvent is alkali soluble.

33. A process as claimed in Claim 27 in which the polyamide substrate is formed of a filled polyamide.

34. A process as claimed in Claim 27 in which the total alkali metal hydroxide content of the conditioning solution is from 10 to about 50 percent by weight of the solution.

35. A process as claimed in Claim 27 in which the conditioning solution is maintained at a temperature from about 1 70 to about 2000F.

36. A process as claimed in Claim 27 in which the total acetic acid compound concentration of the etch solution is from about 5 percent by weight of the solution to solution saturation.

37. A process as claimed in Claim 27 in which the total acetic acid compound concentration of the etch solution is from about 5 to about 60 percent by weight of the solution.

38. A process as claimed in Claim 27 in which the polyamide substrate is contacted with the etch solution for a period of from about 10 seconds to about 1 5 minutes.