JP6180518B2 - Method for metallizing non-conductive plastic surfaces - Google Patents

Description

TECHNICAL FIELD The present invention relates to pretreatment of non-conductive plastic surfaces prior to metallization and is applicable in various industries where decorative coatings or functional metal coatings of plastic parts are required. Can be done. The pretreatment is performed in a solution containing no hexavalent chromium.

Background of the Invention After the conventional non-conductive plastic surface pretreatment method, electroless metallization, mainly electroless nickel plating or copper plating, consisting of etching the surface in a solution containing hexavalent chromium, is performed. Then, activating an ionic or colloidal solution of the palladium compound and reducing in a sodium hypophosphite solution (in most cases) or adsorbed on the plastic surface, respectively, of palladium ions or colloidal palladium particles Either in an acidic solution (usually hydrochloric acid).

  Etching during the pretreatment step of the non-conductive substrate surface is hydrophilic because the surface becomes hydrophilic in other stages of the process in aqueous solution with a sufficient amount of adsorbed palladium salt. In order to ensure proper bonding of the metal coating to the non-conductive plastic surface. Subsequent activation by reduction or promotion is performed to initiate electroless deposition of the metal on the plastic. Thereafter, electroless plating with the metal in the metallization solution is performed via an autocatalytic reaction in which the metal deposited on the surface acts as a catalyst for further deposition. Metallic nickel and copper are mainly used for this electroless plating.

  Thereafter, electrolytic plating or galvanic plating may be performed on the first metal layer. Various metals can be applied, such as chromium, nickel, copper, and brass, or other alloys of the aforementioned metals.

  The main drawback of the conventional method relates to the carcinogenicity of chromic acid in the etching solution. In addition, metals deposited during the electroless deposition process, such as nickel, also cover a portion of the plastisol-insulated rack, resulting in electrochemical metal loss in subsequent metal plating solutions. This is undesirable.

  Various methods for solving this problem have been proposed in the prior art.

US Patent Application No. 2005 / 0199587A1 discloses a method for etching a non-conductive plastic surface in an acidic solution containing 20-70 g / l potassium permanganate. A suitable KMnO ₄ concentration in the above solution is close to 50 g / l. When the concentration is less than 20 g / l, the solution is not effective and the upper limit of the concentration is determined by the solubility of potassium permanganate. After the etching, activation in a palladium salt solution containing an amine and reduction treatment in, for example, a borohydride, hypophosphite or hydrazine solution are performed.

  However, this method has substantial drawbacks. In etching solutions with high permanganate concentrations (about 50 g / l recommended, phosphoric acid about 48% v / v), this decomposes very quickly, especially at high temperatures. The recommended temperature is 100 ° F., ie 37 ° C. The test shows that at this temperature the solution becomes ineffective after 4-6 hours, i.e. the plastic surface is no longer hydrophilic and some parts remain uncoated during metallization; Bonding with plastic is very weak. Often there is a need to prepare solutions with a new portion of permanganate, which is not cheap. In addition, insoluble permanganate decomposition products are formed, contaminating the metallized surface.

  Furthermore, etching in a permanganate solution activates the surface of the plastisol insulation of the rack because it is coated with the product of the etching reaction, namely manganese dioxide. This stimulates the adsorption of palladium compounds with plastisols, which are prone to metallization in solutions of electroless metal deposits. The formation of manganese dioxide on the surface is characteristic of a permanganate etch solution of any composition. Therefore, a very important task of the present invention is to avoid rack metallization and to avoid the loss of metal obtained in subsequent metallization steps.

Lithuania patent application number LT2008-082 also relates to pretreatment of non-conductive plastic surfaces prior to plating. For example, polyimide is added at a concentration between 13 mol / L (about 75% by volume) and 17 mol / L (about 90% by volume) using an oxidizing solution of 0.005M to 0.2M sulfuric acid. A pretreatment composition for etching for 1-2 minutes at a temperature of 80 ° C. is disclosed, wherein the oxidizing agent may be KMnO ₄ , HClO ₄ , V ₂ O ₅ , KClO ₃ . In the case of chlorate (ClO ₃ ⁻ , M = 83.5 g / mol), this corresponds to a concentration between 0.4 and 16.7 g / l.

  Examples are given in Table 2 in this application containing 7 mol / l (about 50% by volume) sulfuric acid and 0.2 mol / L (16.7 g / L) chlorate. Such high concentrations of chlorate have been shown to result in undesirable rapid pretreatment solution degradation.

DETAILED DESCRIPTION OF THE INVENTION Accordingly, the present invention thus far has described the metallization of articles made from non-conductive plastics in an environmentally safe manner, with sufficient process reliability of subsequently applied metal layers. This is based on a problem that could not be achieved with adhesive strength.

  Accordingly, an object of the present invention is to find an etching solution for pretreatment of a non-conductive plastic surface of an article that is non-toxic but provides sufficient adhesion strength of a metal layer applied to the plastic surface.

In the case of etching of a plastic surface as a method for treating a plastic surface in the present application, the subject is etching of a plastic with an inorganic acid solution having an oxidizing agent, activation with a palladium salt solution, and treatment with either a reducing or accelerating solution. Before electroless plating consisting of 0.2 to 15.0 g / l of soluble chlorate (based on KClO ₃ , M = 122.55, i.e. 0.005% in 50-80% v / v sulfuric acid. This is achieved using an etching solution comprising 0016 mol / l to 0.12 mol / l). Etching is preferably performed at room temperature (15-28 ° C., preferably 20-25 ° C.), but can also be performed at high temperatures up to 40 ° C. or 50 ° C. under conditions where the stability of the solution is controlled. The pretreatment solution may optionally contain up to 20 g / l of another oxidant at a standard oxidation potential over chlorate.

  The etching time varies depending on the substrate material and its shape and can be determined by routine experimentation. Generally this is between 1 and 20 minutes, preferably no longer than 10 minutes.

  The source of chlorate ions can be any water-soluble salt. Usually used are sodium chlorate and potassium chlorate.

  The concentration of chlorate ions in the etching solution is between 0.0016 mol / l and 0.12 mol / l, or preferably up to 0.03 mol / l, or even more preferably up to 0.04 mol / l. Range. Preferred ranges are between 0.003 mol / l and 0.08 mol / l or between 0.01 mol / l and 0.06 mol / l or between 0.004 mol / l and 0.04 mol / l. Between.

  The concentration of sulfuric acid ranges between 50 and 80% by volume, preferably between 55 and 70% by volume, and even more preferably between 60 and 65% by volume.

  In some cases, phosphoric acid as an additional acid may be included in the etching solution. The concentration of phosphoric acid typically ranges between 10 and 40% by volume, preferably between 15 and 25% or 30% by volume. Surprisingly, the adhesion of the plated metal layer can be further increased if phosphoric acid is further used.

  A mixture of between 60 and 65% by volume sulfuric acid and 20 to 30% by volume phosphoric acid is particularly preferred.

  Prior to electroless metallization of the plastic surface, including treatment of the plastic in an inorganic acid solution to which an oxidant has been added, activation in a palladium salt solution, and reduction or promotion of the solution. A surface pretreatment method comprising 0.02 to 15.0 g / l of soluble chlorate (eg 0.5 to 5 g / l of soluble chlorine in 50-80% v / v sulfuric acid at room temperature) The method according to claim 1, wherein the plastic surface is etched with an acid salt solution and subjected to an additional treatment prior to activation with a palladium compound solution and treatment with a reducing / promoting solution in an alkali metal hydroxide solution.

  The etching solution can optionally contain 2 to 20 g / l of additional oxidant having a standard oxidation potential above chlorate ions.

Alkali metal chlorate and sulfuric acid form a yellow compound and the normal oxidation potential in H ₂ SO ₄ solution medium is sufficient for reaction with the plastic surface at room temperature. Because of this reaction, the plastic surface becomes hydrophilic and adsorbs a sufficiently strong palladium compound. The yellow reaction product between chlorate and sulfuric acid is a catalyst poison for the palladium catalyst. During etching, this penetrates the surface layer of the plastisol insulation of the rack and prevents electroless metal deposition on the plastisol in the electroless metallization solution; the metallization process occurring on the conductive plastic surface is unaffected .

During dissolution of 1-2 g / l sodium chlorate or potassium + 5-10 g / l of a second strong oxidant, for example NaBiO ₃ , the etching properties are kept at room temperature for several days, without the solution being adjusted Can be used. If only sodium / potassium chlorate is included in the solution, the etch characteristics persist for much shorter times (up to 24 hours).

  An important characteristic feature of the proposed method that makes it different from permanganate etching is the very high adhesion value between the coating and the plastic (often over 1.2-1.3 kg / cm) Is obtained. These values vary depending on the etching solution composition, the etching time (there is an optimum etching time for each composition), and the composition of the activation solution. Usually, when using an actual activation solution, the adhesion value obtained is higher than that obtained with a colloidal activation solution.

The etching solution can be prepared as follows:
700 ml concentrated sulfuric acid is mixed with 300 ml deionized water. Allow the solution to cool. Next, 2 g potassium chlorate + 10 g sodium perchlorate is dissolved in the solution. The solution can be used immediately. A second acidifying agent, sodium perchlorate, which is stronger than potassium chlorate, is optional. This extends the life of the composition, but does not require subsequent good adhesion of the plated metal layer.

  If the amount of water used to prepare the solution exceeds 50% by volume compared to sulfuric acid, the yellow plastic-oxidized compound will not form between the chlorate ions and the sulfuric acid molecules, so the water content of the solution The rate should preferably not exceed 50% by volume.

  When the amount of water used in the preparation of the solution is less than 20% by volume compared to sulfuric acid, the plastic surface decomposes during etching due to too high sulfuric acid concentration, and thus chemical nickel coating and plastic Adhesion between is not obtained.

  If the amount of potassium chlorate dissolved in the solution is less than 0.5 g / l, this concentration is unacceptable because the etching process is performed for more than 15 minutes.

  If the amount of potassium chlorate dissolved in the solution exceeds 5.0 g / l, over-etching may be seen after a minimum etching time, ie 2-3 minutes, which is due to the high concentration of chloric acid. Neither salt is acceptable, resulting in much weaker adhesive strength. However, depending on the substrate material, concentrations as high as 15 g / l are acceptable and may provide sufficient adhesion.

The object of the present invention is further achieved by the following method according to the present invention:
A method of metallizing a non-conductive plastic surface of an article comprising the following steps:
A) etching the plastic surface with the above etching solution comprising a source of chlorate ions that results in a chlorate ion concentration of 0.0016-0.12 mol / l in 50-80% v / v sulfuric acid;
B) treating a plastic surface with a solution of a metal colloid or a solution of a metal compound, wherein the metal is a group I transition metal of the periodic table of elements and a group VIII transition of the periodic table of elements The method comprising the steps of: C) metallizing a plastic surface with a metallization solution.

  An article in the context of the present invention is understood to mean an article made from at least one non-conductive plastic or coated with at least one layer of at least one non-conductive plastic. Thus, the article has at least one electrically non-conductive plastic surface. Plastic surface is understood in the context of the present invention to mean the surface of the article.

  The processing steps of the present invention are performed in the order described, but do not necessarily move immediately. Further processing steps and, in each case, an additional rinsing step, preferably with water, can be carried out between these steps.

  The plastic surface is made from at least one electrically non-conductive plastic. In one embodiment of the invention, the at least one electrically non-conductive plastic comprises acrylonitrile-butadiene-styrene copolymer (ABS copolymer), polyamide (PA), polycarbonate (PC) and at least one further polymer. Selected from the group comprising a mixture of a plurality of ABS copolymers.

  In a preferred embodiment of the invention, the electrically nonconductive plastic is an ABS copolymer or a mixture of an ABS copolymer and at least one further polymer. The at least one further polymer is more preferably polycarbonate (PC), which means that ABS / PC mixtures are particularly preferred.

  The etching solution of the present invention preferably contains no chromium or chromium compounds; the etching solution contains neither chromium (III) ions nor chromium (VI) ions. Thus, the etching solution of the present invention does not contain chromium or chromium compounds; the etching solution does not contain chromium (III) ions and chromium (VI) ions.

In a further preferred embodiment of the invention, the following further processing steps:
Ai) The step of treating the plastic surface in a solution containing an alkaline solution is performed between step A) and step B).

  The further processing step Ai) is also called neutralization. Any alkaline source can be used, and an aqueous solution of sodium hydroxide is preferred.

In yet another embodiment of the invention, the following further processing steps:
Ai) A step of treating the plastic surface in a solution containing a chlorate ion reducing agent and optionally a second oxidizing agent is performed between step A) and step B).

  The further processing step Ai) is also called reduction treatment. This reduction treatment reduces chlorate ions and optionally a second oxidant that adheres to the plastic surface and facilitates the removal of such ions. The reducing agent is selected from the group comprising, for example, hydroxylammonium sulfate, hydroxylammonium chloride and hydrogen peroxide.

  The method of the present invention further comprises a treatment step B) in which the plastic surface is treated with a solution of metal colloid or a solution of metal compound.

  The metal or metal compound of the metal colloid is selected from the group comprising a Group I transition metal of the Periodic Table of Elements (PTE) and a Group VIII transition metal of the PTE.

  The PTE Group VIII transition metal is selected from the group comprising palladium, platinum, iridium, rhodium, and mixtures of two or more of these metals. The PTE Group I transition metals are selected from the group comprising gold, silver and mixtures of these metals.

  The preferred metal in the metal colloid is palladium. The metal colloid is stabilized with a protective colloid. The protective colloid is selected from the group comprising metal protective colloids, organic protective colloids and other protective colloids. Preferred as the metal protective colloid is tin ion. The organic protective colloid is selected from the group comprising polyvinyl alcohol, polyvinyl pyrrolidone and gelatin, preferably polyvinyl alcohol.

In a preferred embodiment of the invention, the metal colloid solution in process step B) is an activator solution with palladium / tin colloid. This colloidal solution is obtained from a palladium salt, a tin (II) salt and an inorganic acid. A preferred palladium salt is palladium chloride. A preferred tin (II) salt is tin (II) chloride. The inorganic acid can be composed of hydrochloric acid or sulfuric acid, preferably hydrochloric acid. The colloidal solution is formed by reducing palladium chloride to palladium using tin (II) chloride. The conversion of palladium chloride to colloid is complete, so the colloidal solution no longer contains palladium chloride. The concentration of palladium is 5 mg / l to 100 mg / l, preferably 20 mg / l to 50 mg / l, more preferably 30 mg / l to 45 mg / l based on Pd ²⁺ . The concentration of tin (II) chloride is from 0.5 g / l to 10 g / l, preferably from 1 g / l to 5 g / l, more preferably from 2 g / l to 4 g / l, based on Sn ²⁺ . The concentration of hydrochloric acid is 100 ml / l to 300 ml / l (37% by weight HCl). Further, the palladium / tin colloidal solution further comprises tin (IV) ions that form through oxidation of tin (II) ions. The temperature of the colloidal solution during process step B) is 20 ° C to 50 ° C, preferably 35 ° C to 45 ° C. The treatment time with the activator solution is 0.5 minutes to 10 minutes, preferably 2 minutes to 5 minutes, and more preferably 3 minutes to 5 minutes.

  In a further embodiment of the invention, a solution of the metal compound is used instead of the metal colloid in process step B). The solution of the metal compound used is a solution containing an acid and a metal salt. The metal of the metal salt is composed of one or more of the PTE Group I and Group VIII transition metals listed above. The metal salt may be a palladium salt, preferably palladium chloride, palladium sulfate or palladium acetate, or a silver salt, preferably silver acetate. The acid is preferably hydrochloric acid. Alternatively, it is also possible to use metal complexes, for example palladium complex salts, for example salts of palladium-aminopyridine complexes. The metal compound in process step B) is present in a concentration of 40 mg / l to 80 mg / l based on the metal. The solution of the metal compound can be used at a temperature of 25 ° C to 70 ° C, preferably 25 ° C. The treatment time with the metal compound solution is 0.5 minutes to 10 minutes, preferably 2 minutes to 6 minutes, and more preferably 3 minutes to 5 minutes.

Between step A) and step B) the following further processing steps:
Aii) A step of treating the plastic surface in an aqueous acidic solution can be performed.

  Preference is given to carrying out process step Aii) between process step Ai) and process step B). In the process according to the invention, if process step Ai) is followed by rack protection, process step Aii) is more preferably carried out between rack protection and process step B).

  The treatment of the plastic surface in process step Aii) is also referred to as the previous soaking, and the aqueous acidic solution used is referred to as the previous soaking solution. The previous immersion solution has the same composition as the colloidal solution of process step B) without the presence of the metal in the colloid and its protective colloid. When using the palladium / tin colloidal solution of process step B), if the colloidal solution also contains hydrochloric acid, the previous soaking solution contains exclusively hydrochloric acid. In the case of previous immersion, a simple immersion in the previous immersion solution at ambient temperature is sufficient. Without rinsing the plastic surfaces, they are further treated directly with the colloidal solution of process step B) after treatment in the previous soaking solution.

  Processing step Aii) is preferably carried out when processing step B) comprises treatment of the plastic surface with a solution of metal colloids. Processing step Aii) can also be carried out when processing step B) involves treatment of the plastic surface with a solution of a metal compound.

  After treatment of the plastic surface with metal colloids or metal compounds in treatment step B), these can be rinsed.

In a further embodiment of the invention, the following further processing steps:
Bi) Treatment of the plastic surface in an aqueous acidic solution and Bii) Electroless metallization of the plastic surface in the metallization solution are carried out between treatment step B) and treatment step C).

This embodiment is shown schematically in Table 1.

  These further process steps Bi) and Bii) are utilized when the article is to be metallized by an electroless metallization process, i.e. the first metal layer is applied to the plastic surface by an electroless process. Should be.

  When the activation in process step B) is carried out using metal colloids, the plastic surface is an accelerator in process step Bi) in order to remove colloidal components in the colloid solution, for example protective colloids, from the plastic surface. Treated with solution. When the colloid in the colloidal solution in process step B) is a palladium / tin colloid, the accelerator solution used is preferably an aqueous acid solution. The acid is selected from the group comprising, for example, sulfuric acid, hydrochloric acid, citric acid and tetrafluoroboric acid. In the case of palladium / tin colloids, the accelerator solution serves to remove tin compounds that serve as protective colloids.

Alternatively, in process step Bi), the reducing agent treatment is performed in process step B) when a solution of the metal compound is used in place of the active metal colloid. Therefore, the reducing agent solution used for this purpose contains hydrochloric acid and tin (II) chloride when the metal compound solution is a hydrochloric acid solution of palladium chloride or an acidic solution of silver salt. The reducing agent solution may also contain another reducing agent, such as NaH ₂ PO ₂ or further boron or borohydride, such as alkali metal borane, or alkaline earth metal borane or dimethylaminoborane. Preference is given to using NaH ₂ PO ₂ in the reducing agent solution.

  After promotion or treatment with a reducing agent solution in treatment step Bi), the plastic surface can first be rinsed.

  Processing step Bi) and optionally one or more rinsing steps are followed by processing step Bii) in which the plastic surface is electroless metallized. Electroless nickel plating, for example, includes, among other things, nickel sulfate, hypophosphorous acid, eg, sodium hypophosphite, and organic complexing agents and pH adjusters (eg, buffering agents) as reducing agents, among others. This is achieved using a nickel bath. The reducing agent used may likewise be dimethylaminoborane or a mixture of hypophosphite and dimethylaminoborane.

  Alternatively, an electrolytic copper bath for electroless copper plating, typically a copper salt, such as copper sulfate or copper hypophosphite, and a reducing agent such as formaldehyde or hypophosphite, such as an alkali metal or ammonium It is possible to use an electroless copper bath containing a salt or hypophosphorous acid and one or more complexing agents, for example tartaric acid and also a pH adjusting agent, for example sodium hydroxide.

  The surface thus rendered conductive can then be further metallized by electrolysis to obtain a functional or decorative surface.

  Step C) of the method according to the invention is the metallization of the plastic surface with a metallization solution. The metallization in process step C) can be carried out by electrolysis. In the case of electrolytic metallization, any desired metal deposition bath can be used, for example a deposit of nickel, copper, silver, gold, tin, zinc, iron, lead or alloys thereof. Such deposition baths are well known to those skilled in the art. Watt nickel baths are commonly used as bright nickel baths, which contain nickel sulfate, nickel chloride and boric acid, as well as saccharin as an additive. Examples of compositions used as bright copper baths are those containing organic sulfur compounds, such as organic sulfides or disulfides, as additives, in which copper sulfate, sulfuric acid, sodium chloride and sulfur are in a low oxidation state. .

  The effect of metallization of the plastic surface in process step C) is that the plastic surface is coated with a metal, which metal is selected from the metals listed above for the deposition bath.

In a further embodiment of the invention, after process step C), the following further process steps:
Ci) Storage of the metallized plastic surface at an elevated temperature is carried out.

  In all electroplating processes where the nonconductor is coated with metal by wet chemical means, the adhesion between the metal and the plastic substrate is increased during the first period after application of the metal layer. This treatment is complete after about 3 days at room temperature. This can be greatly facilitated by storage at elevated temperatures. This treatment is complete after about 1 hour at 80 ° C. The initial low bond strength is believed to be due to a thin water layer at the interface between the metal and the non-conductive substrate that prevents the generation of electrostatic forces.

  The method according to the invention thus makes it possible to achieve metallization of the electrically non-conductive plastic surface of the article with good process reliability and excellent adhesion strength of the subsequently applied metal layer. The adhesion strength of the metal layer applied to the plastic surface reaches a value up to 2.7 N / mm (corresponding to approximately 2.7 kg / cm, 1 kg / cm = 0.98 N / mm) or higher. Thus, the achieved adhesion strength is also better than that obtained by the prior art after etching the plastic surface with chromium sulfate (see Examples 2 and 3).

  In general, adhesion values greater than 0.8 N / mm are required for industrial applications and for plating non-complex shaped objects. In general, the higher the adhesion, the better the stability of the deposit.

  Furthermore, not only a flat plastic surface is metallized with high adhesion strength by the method according to the invention; instead, a non-uniformly shaped plastic surface, for example a showerhead, is also a uniform and strongly bonded metal coating Is given.

  The treatment of the plastic surface by the method according to the invention is preferably carried out by continuously immersing the article in the solution in a container in which the respective treatment is carried out in a conventional dipping method. In this case, the article can be immersed in the solution, either fixed in a rack or housed in a drum. Fixing to a rack is preferred. Alternatively, the article is called a conveyor plant and can be processed, for example, by lying on a tray and being continuously conveyed horizontally through the plant.

Examples The examples described below are intended to illustrate the invention in detail.

Example 1
ABS (acrylonitrile-butadiene-styrene copolymer) and PC / ABS (mixture of 45% polycarbonate and 55% acrylonitrile butadiene styrene copolymer) contain 50 g / l KMnO _{4 according} to US Patent Application No. 2005 / 0199587A1 In a 45% v / v phosphoric acid solution at 37 ° C. for 5 minutes (in the case of ABS) or 15 minutes (PC / ABS), or 50-80% with 0.5-5.0 g / l KClO ₃ Etch in v / v sulfuric acid solution and add oxidizing agent at 20 ° C. for 1-12 minutes. During etching, the plastic is immersed in a room temperature neutralization solution containing 10 g / l NaOH for 1-2 minutes, followed by an actual solution of palladium compound (5 minutes at 20 ° C.) or a colloidal solution (2 at 35 ° C.). Min) (the colloidal solution is a branded solution of DOW Chemical Company (“DOW”)). The concentration of PdCl ₂ in the real solution is 0.1 g / l and the pH of the solution is 2.7. Upon activation in real Pd solution, the plastic is kept at 60 ° C. in a solution containing 20 g / l sodium hypophosphite at pH 9 for 5 minutes. Upon activation in a branded colloidal solution, the plastic is treated for 2 minutes at 40 ° C. with a branded accelerated solution of DOW. The plastic is then nickel plated using DOW's Niposit-PM nickel plating process. The quality of the coating is evaluated based on factors such as fully / incompletely plated plastic surfaces, plated or unplated plastisol insulating racks, and electroless nickel-plastic bond strength. To evaluate adhesion, the Ni plating is thickened in a galvanic copper bath and the force required to peel a 1 cm width from the plastic is measured (kg / cm). In the case of the ABS test piece, the etching time in the permanganate solution was 5 minutes, and in the case of the PC / ABS test piece, it was 15 minutes. The etching time in the chlorate solution was 5 minutes for all specimens. The conditions of plastic pretreatment for metallization and the results of metallization (electroless nickel plating) are shown in Table 2 below.

  For specimens 1-4, the plastisol insulation of the rack is partially coated with electroless nickel in the case of etching based on permanganic acid, while the insulation remains clean in the case of etching based on chlorate. It shows that there is. Furthermore, the value of adhesion between the Ni coating and ABS is significantly higher than in the case of chlorate etching for both ionic and colloidal activation solutions.

  The same result is seen in the case of electroless nickel plating of PC / ABS (test pieces 5-8) in the chlorate etching process, the plastisol insulation is not coated at all and the adhesion value is particularly ionic Significantly higher when active solution is used.

If the KClO ₃ concentration in the etching solution is lower than 0.5 g / l, the ABS is not coated with electroless nickel or is incompletely coated (test piece 9). If the KClO ₃ concentration is above 5 g / l (test piece 10), over-etching occurs after 5 minutes of etching and thus the adhesion value of the coating is significantly low (not enough for practical applications). Similar results are obtained in the case of PC / ABS metallization when the recommended KClO ₃ concentration value is exceeded (specimens 11 and 12).

If the H ₂ SO ₄ concentration in the etching solution is lower than 50% v / v, the etchant is not sufficiently effective, so the plastic is not covered at all by electroless nickel or is incompletely coated. (Test piece 13). If the H ₂ SO ₄ concentration is higher than 80% v / v (test specimen 14), over-etching of the plastic occurs and the adhesion between the chemical nickel coating and the plastic is insufficient.

Example 2
A disk of ABS plastic (Novodur P2MC manufactured by Ineos) circular substrate having a diameter of 7 cm was fixed to a stainless steel wire. The substrate was immersed in various pretreatment etching solutions according to the invention as defined in Table 4 for 4 minutes at a temperature of 22 ° C. (The process sequence is shown in Table 3). The substrate was then rinsed with running water for about 1 minute. Subsequent to rinsing, after neutralization (treatment step Ai)) and simple immersion in a solution of 300 ml / l 36% hydrochloric acid (treatment step Aii)), the substrate is colloidal activator based on palladium colloid ( Activated in Adhemax Aktivator NA (100 ppm palladium) from Atotech for 3 minutes at 40 ° C. (treatment step B).

Following rinsing, the protective shell of palladium particles was removed at 40 ° C. for 3 minutes (Adhemax ACC1 accelerator from Atotech, process step Bi)). The substrate is then nickel-plated at 45 ° C. for 10 minutes without external current (Atotech Adhemax LFS, process step Bii)), rinsed, and copper plated at room temperature at 3.5 A / dm ² for 70 minutes (Cupracid HT, manufactured by Atotech, Process C)). After rinsing, the panel was stored for 60 minutes at 70 ° C. (processing step Ci)). Thereafter, a metallized plastic substrate strip approximately 1 cm wide was cut using a knife and the metal layer was pulled away from the plastic using a tensile tester (Instron) (ASTM B 533 1985). Reapproved 2009). The adhesive strength shown in Table 4 was obtained.

  From Table 4 it becomes apparent that very high adhesion values are obtained by careful selection of the concentration of chlorate in combination with sulfuric acid.

Specimen No. 1, a low concentration such as potassium chlorate 0.2 g / l ^- the (0.0016 mol / l ClO ₃ of corresponding to the density) is sufficient to obtain good adhesion Show. Maximum values are obtained in the range of about 1.5 g / l potassium chlorate. Therefore, the adhesive strength is reduced. Compositions comprising a mixture of sulfuric acid and phosphoric acid (Table 4, No. 9-No. 16 test specimens generally have the same chlorate ion temperature when compared to etching in solutions containing only sulfuric acid. It should be noted that it exhibits higher adhesion values and is therefore particularly preferred.

Claims (12)

The following steps:
A) etching the plastic surface with an aqueous etching solution;
B) A step of treating a plastic surface with a colloidal metal solution or a metal compound solution, wherein the metal is palladium, platinum, iridium, rhodium, gold, silver or two or more of these metals. And C) metallizing the plastic surface of the electrically non-conductive article comprising the step of metallizing the plastic surface with a metallization solution. The etching solution comprises a source of chlorate ions and 50-80% v / v sulfuric acid that provides a chlorate ion concentration of 0.003 to 0.08 mol / l, and the etch solution comprises: Said method characterized in that it contains no chromium (III) ions and no chromium (VI) ions.   2. Process according to claim 1, characterized in that in process step A) the source of chlorate ions in the etching solution is selected from sodium chlorate and potassium chlorate.   The process according to claim 1 or 2, characterized in that the chlorate ion concentration is in the range between 0.01 and 0.06 mol / l.   The process according to claim 1 or 2, characterized in that the chlorate ion concentration is in the range between 0.004 and 0.04 mol / l. The method according to any one of claims 1 to 4 , characterized in that the sulfate ion concentration is in the range between 60% and 70% by volume. Etching solution, characterized in that it further includes a phosphoric acid A method according to any one of claims 1 to 5. The process according to claim 6 , characterized in that the phosphoric acid concentration is in the range between 10 and 30% by volume. 8. Process according to any one of claims 1 to 7 , characterized in that the metal in process step B) is palladium. The plastic surface is made from at least one electrically non-conductive plastic, and the at least one electrically non-conductive plastic is acrylonitrile-butadiene-styrene copolymer, polyamide, polycarbonate, and acrylonitrile-butadiene-styrene. 9. Process according to any one of claims 1 to 8 , characterized in that it is selected from the group comprising a mixture of a copolymer and at least one further polymer. The following further processing steps:
Ai) treating the plastic surface in a solution comprising a reducing agent selected from the group comprising hydroxylammonium sulfate, hydroxylammonium chloride and hydrogen peroxide , between treatment step A) and treatment step B). which comprises carrying out the method according to any one of claims 1 to 9. The following further processing steps:
Ai) The step of treating the plastic surface in a solution containing a neutralizing agent comprising a source of hydroxide ions is carried out between treatment step A) and treatment step B). 11. The method according to any one of 1 to 10 . The following further processing steps:
Bi) the step of treating the plastic surface in an aqueous acidic solution and Bii) the step of electroless metallization of the plastic surface in the metallization solution are carried out between treatment step B) and treatment step C). It characterized a method according to any one of claims 1 to 11.