EP0815292B1 - Process for the selective or partial electrolytic metallization of surfaces of substrates made from non-conducting materials - Google Patents

Abstract

The invention concerns a process for the selective or partial electrolytic metallization of surfaces of substrates made from electrically non-conducting materials which for the purpose of the coating process are secured to plastic-coated holding elements. The proposed process involves the following steps: a) preliminary treatment of the surfaces with an etching solution containing chromium (VI) oxide; followed immediately by b) treatment of the surfaces with a colloidal acidic solution of palladium-/zinc compounds, care being taken to prevent prior contact with adsorption-promoting solutions; c) treatment of the surfaces with a solution containing a soluble metal compound capable of being reduced by zinc (II) compounds, an alkali or alkaline earth metal hydroxide, and a complex forming agent for the metal in a quantity sufficient at least to prevent precipitation of metal hydroxides; d) treatment of the surfaces with an electrolytic metallization solution. By applying this process, it is possible to ensure that only the surfaces of the work piece are coated with metal, not the holding elements or, where applicable, non-conductive plastic layers applied to parts of the work pieces. In addition, the process facilitates direct electrolytic metallization even of large plastic surfaces without prior currentless metallization.

Description

The invention relates to a method for selective or partial electrolytic Metallizing surfaces of molded plastic parts made of electrically non-conductive Materials which are coated with plastics for the following treatment Holding elements are attached.

Various methods are known for coating non-conductor surfaces. In wet chemical processes, the surfaces to be metallized after a suitable pretreatment either catalyzed first and then electroless and then optionally metallized or directly electrolytically metallized.

There have been processes according to the first variant with electroless metallization However, it was found to be disadvantageous because the process control of the electroless metallization bath is difficult to treat the waste water from this Bath complex and expensive and the process due to the low deposition speed the metallization bath is long and therefore also expensive.

In particular for the metal coating of plastic parts, for example for sanitary fittings and for the automotive industry, as well as of parts that as Housings for electrical shielded against electromagnetic radiation Devices are used, the electroless metallization processes are problematic. In the treatment of such molded parts in general relatively large volume of treatment solutions from a treatment bath in the next dragged off, as they have a shape through which the treatment solution is exhausted when the parts are lifted out of the baths. There Electroless metallization baths are usually toxic and only formaldehyde contain complex removers that are difficult to remove in their treatment large amounts of these baths are lost and have to be expensive to be disposed of.

A number of metallization processes have therefore been developed with which the non-conductive surfaces without electroless metallization directly with metal can be coated. However, such methods are particularly described for the metallization of the borehole walls in printed circuit boards. The direct electrolytic metallization in borehole metallization is opposite a metal coating of other plastic parts, such as Sanitary fittings or with three-dimensional in comparison to plates Contour, but much easier, because smaller areas can be metallized are. The distances of the non-conductive to be overcome in the metallization Sustrat surface is shorter in the case of borehole metallization on printed circuit boards and therefore easier to reach.

EP 0 298 298 A2 describes a method for electrolytic metallization described a non-conductor in which the non-conductor surface to be metallized is coated with a metal chalcogenide. The metal chalcogenide is obtained by treating the surfaces with a palladium colloid Tin compounds as a protective colloid, and subsequent treatment with a soluble metal chalcogenide compound, preferably a metal sulfide, educated.

A similar process is disclosed in US-A-49 19 768. There describes a method in which the non-conductor surface is initially coated with a tin (II) salt is treated, then with a dissolved sulfide and then with a solution containing hydrochloric acid and a palladium salt. Subsequently the pretreated surface is metallized.

EP 0 320 601 A2 describes a method for metallizing non-conductors, in which the non-conductor surfaces first with a permanganate solution are treated, referring to this insoluble manganese dioxide forms. The manganese dioxide layer is then treated with a chalcogen compound, preferably containing sulfur compounds Solution converted. A metal layer can then be deposited electrolytically become.

With the methods mentioned, a chalcogenide layer can be sufficient high electrical conductivity by means of a special pretreatment for subsequent metallization of drill holes in printed circuit boards become. However, the conductivity of such a layer is not sufficient for that Metallization of large-area non-conductive substrates, because there too large bridged non-conductive paths from the contact points of the power supply Need to become. When metallizing, the chalcogenide layer formed in destroyed near the contact points.

US-A-39 84 290 discloses a method in which the borehole walls a circuit board first in a solution containing the connection of one nobler metal than copper, is treated, whereby a metal layer on the copper surfaces of the circuit board and the non-conductor surfaces. Subsequently, the metal layer from the copper surfaces again removed, and then the metal layer on the non-conductive surfaces and electrolytically metallized the copper surfaces.

Another method for direct electrolytic metallization is in DE 33 23 476 C2. The non-metallic objects to be metallized are first with a solution containing a noble metal, for example treated with a palladium activator stabilized with tin compounds and then electrolytically coated in a metallization bath. Suitable organic additives are contained in the metallization bath, with which a preferred metal deposition on the previous process step Formed metal layers promoted on the non-conductive areas becomes.

In the document DE 37 41 459 C1 there is a process for the production of plated-through holes Printed circuit boards by direct electrolytic metal deposition disclosed catalytically activated surfaces of the base material, in which the Surfaces before electrolytic plating with a solution that has a or several nitrogen-containing organic compounds, for example polyvinylpyrrolidone, 2,2,6,6-tetramethyl-4-piperidone, pyridinium propylsulfobetaine or contains a polymeric, polyquaternary ammonium chloride, pretreated become.

EP 0 456 982 A1 describes a method for the electrolytic metallization of a Disclosed substrate, in which the substrate surfaces first, for example catalyzed in a solution containing a palladium colloid solution stabilized with tin compounds are then the tin compounds in a known manner are removed from the substrate surface, the one used for this Solution additionally contains the connection of a metal that is more noble than tin and the surfaces are subsequently electrolytically metallized.

Even with this method it is only possible to drill hole walls in printed circuit boards to metallize, since the conductivity of the layer formed is insufficient, to metallize even larger non-conductive surfaces.

A completely different method is described in WO 89/08375 A1. The procedure also serves for the production of plated-through circuit boards. However becomes a first conductive layer for subsequent electrolytic Metallize from conductive polymers formed by the non-conductive surfaces are first treated with a permanganate solution so that manganese dioxide, the printed circuit board after rinsing off excess treatment solution in a solution, containing a monomer from the group of pyrroles, furans or thiophenes, is immersed and then the substrate with an acidic solution Is brought into contact, resulting from the liquid film containing the monomer forms a conductive polymer layer on the borehole walls. This can then be directly electrolytically metallized.

In the German laid-open specification 39 07 789 A1 there is a process for the deposition an electrically conductive layer on an electrically non-conductive Surface specified, in which the surface is initially an electrical conductive base layer, which is characterized by an electroless chemical polymerization at least one conductive polymer is produced on the surface, is generated and then another electrically conductive layer, for example another conductive polymer layer or a metal layer, is deposited. This process can also be used for substrates with larger sizes non-conductive surfaces can be directly electrolytically metallized if the the aforementioned procedure is repeated several times. However, this is not practical because it leads to extremely long process times.

In addition, the conductive polymer layers formed on the surfaces have A sufficiently high conductivity only a short time after their manufacture on. After that, it quickly falls off, so that large-area metallization is not possible anyway.

EP 0 616 053 A1 describes a method for the direct metallization of non-conductive Surfaces disclosed, in which the surfaces first with a Cleaner / conditioning solution, then with an activator solution, for example a palladium colloid solution, stabilized with tin compounds, and then treated with a solution containing compounds of a metal, which is nobler than tin, as well as an alkali hydroxide and a complexing agent. Thereafter, the surfaces can be in a containing a reducing agent Solution treated and finally metallized.

With the known methods there is usually only a direct electrolytic metallization small areas, e.g. B. borehole walls of printed circuit boards possible; metallizing large plastic surfaces fails in most cases the lack of metallizability of the layers on the non-conductive Surfaces are formed.

For the large-scale application of direct electrolytic metallization of plastic parts that are heavily structured such. B. combs, or three-dimensional are formed with substantial extension into the third dimension, e.g. B. Coffee pots, telephone receivers, water pipe fittings, the work pieces to be attached to supporting frames used in the metallization process must not be coated because this metallic layer causes production problems leads. Otherwise, the metal layers must be removed from the supporting frames after coating the workpieces. This means an additional effort for the stripping associated with the consumption of chemicals. Moreover, the productivity of the metallization plant in this case less, because the racks before re-loading must first be demetallized with workpieces.

The present invention is therefore based on the problem, the disadvantages to avoid the prior art and a method for selective or partial electrolytic metallization of surfaces of substrates (plastic molded parts) Made of electrically non-conductive materials on the outside with plastic coated holding elements, for example support frames, are attached Find.

The problem is solved by the method according to claim 1. Preferred embodiments the invention are specified in the subclaims.

a) Auswählen von Polyvinylchlorid für die Kunststoffbeschichtung der Halteelemente,

b) Vorbehandeln der Kunststoffformteile mittels einer Chrom-(VI)-oxid enthaltenden Ätzlösung,

c) anschließend Behandeln der Kunststoffformteile mit einer kolloidalen sauren Lösung von Palladium/Zinnverbindungen, unter Vermeidung eines vorherigen Kontaktes des Materials für die Halteelemente mit adsorptionsfördernden Lösungen,

d) Behandeln der Kunststoffformteile mit einer Lösung, enthaltend eine mittels Zinn-(ll)-Verbindungen reduzierbare lösliche Metallverbindung, ein Alkali- oder Erdalkalimetallhydroxid und einen Komplexbildner für das Metall in einer mindestens die Ausfällung von Metallhydroxiden verhindernden Menge,

e) elektrolytisches Metallisieren der Kunststoffformteile.

The process according to the invention comprises the process steps:

a) selection of polyvinyl chloride for the plastic coating of the holding elements,

b) pretreating the plastic molded parts by means of an etching solution containing chromium (VI) oxide,

c) then treating the plastic molded parts with a colloidal acid solution of palladium / tin compounds, avoiding prior contact of the material for the holding elements with adsorption-promoting solutions,

d) treating the plastic molded parts with a solution comprising a soluble metal compound which can be reduced by means of tin (II) compounds, an alkali metal or alkaline earth metal hydroxide and a complexing agent for the metal in an amount which at least prevents the precipitation of metal hydroxides,

e) electrolytic metallization of the molded plastic parts.

The substrate surfaces can be between some or all process steps be rinsed.

According to the prior art, adsorption-promoting solutions are in particular So-called conditioning solutions used in the manufacture of printed circuit boards used. These are usually aqueous solutions in which in particular Polyelectrolytes, such as polycationic polymers, with a molecular weight above 10,000 g / mol are included. After treating the non-conductive surfaces with such a conditioning solution not only those that are to be metallized, as desired Plastic surfaces coated with metal, but also - unnecessarily - The holding elements coated on the outside with plastics.

With the method according to the invention, however, it is not necessary to Free the holding elements from the metal after use, as the substrates not be brought into contact with a conditioning solution. Rather, the holding elements after metallizing the substrate surfaces and removing the metallized substrates without further treatment be immediately returned to the production cycle and immediately for the metallization of further non-conductive substrates become. Should be on the contact tips / metal tips during the Metallization has deposited metals, they must be removed from time to time, to avoid contact problems and contamination of the bathroom.

No additional cleaning and etching steps are required to demetallize the frame parts located away from the contact tips. This also reduces the effort for wastewater disposal. In addition, fewer chemicals are used. The productivity of the metallization system is also increased, since a larger number of substrates to be metallized can be treated with a given number of holding elements.
However, it is a prerequisite that, before the substrates are treated with the activator, they do not come into contact with agents that promote adsorption of the colloidal particles.
In addition to the solutions known to the person skilled in the art, particular attention must be paid here to any contaminated rinsing water, in particular if circulating water is used in the factory.
Carryover from conditioning baths of parallel manufacturing plants into this water cycle should be avoided, as should the entry of agents that can act like the adsorption-promoting polyelectrolytes. Therefore, the parallel use of racks is not useful either for the manufacture of printed circuit boards or for the purpose according to the invention.

Another advantage of the method is that the surfaces of the metallizing substrates can also be partially metallized by Parts of the surfaces are covered with a suitable material. There this material also when carrying out the method according to the invention is not coated, a subsequent removal of the material is very easily possible without selective treatment if necessary Removal of the metal deposited there the metal layers on the damage metallized substrate.

The method is particularly electrical for three-dimensionally structured non-conductive molded parts, their enveloping surface, that is the smallest possible surface an envelope of an object, is significantly smaller than its surface, for example for plastic parts for the sanitary area, automobile construction, or suitable for electrically shielded housings, because their disadvantage, the Exploiting treatment solutions from the baths is often only in practice unsatisfactory can be avoided. Through direct electrolytic metallization in the method according to the invention without preceding electroless Metallization drops smaller amounts of toxic and complexing agents Sewage on than with conventional processes for plastic metallization.

The method according to the invention is therefore less expensive overall, less complex and environmentally friendly than the state of the art known methods.

Under circumstances known to those skilled in the art, it may be necessary, depending on substrate to be metallized, before starting the method according to the invention first in an organic solvent, such as one Diethylene glycol or ethylene glycol derivative, dimethylformamide or others polar or non-polar solvents to swell the substrate. These solvents can also be used in a mixture with water. Especially preferred treatment agents additionally contain alkalizing agents, such as for example alkali hydroxides or tetraalkylammonium hydroxides. The solutions can vary depending on the type of substrate to be treated at room temperature or used at an elevated temperature.

According to the invention in process step a) the surfaces to be metallized pretreated in an etching solution containing chromium (VI) oxide. This is usually the case a solution containing chromic acid, which also contains sulfuric acid may contain. Solutions containing 360 g of chromium (VI) oxide and Contain 360 g of concentrated sulfuric acid in one liter of water. The solution is used for the treatment at a temperature of, for example, 60 ° C heated up. Depending on the non-conductive substrate to be metallized, the Treatment time from 2 to 16 minutes.

After a rinsing treatment, adhering to the substrate surfaces Chromium (VI) compounds reduced to chromium (III) compounds. For this purpose, preferably an acidic aqueous solution of sodium hydrogen sulfite be used. However, other reducing agents, such as hydroxylamine.

After a further rinsing treatment, the substrate can be dissolved 300 ml / l of concentrated hydrochloric acid or another mineral acid, such as concentrated sulfuric acid, are treated in aqueous solution. This treatment is useful to the activator solution with which the substrate subsequently treated, not continuously by rinse water dilute. Since the activator also contains tin compounds in addition to palladium, the mineral acid treatment solution can also add these tin compounds contain. This will partially compensate for the carryover losses. The treatment time in this pre-immersion solution can vary widely can be varied. It is only important that the surfaces of the substrate are complete be wetted. Any bath temperature can be set.

The success of the process is probably due to the fact that the adsorption of palladium particles from a colloid solution is used to make the non-conductive surface with a large number of palladium particles too occupy. Because the palladium particles come from a colloidal solution after adsorption, surround it with a protective colloid cover that covers the electrical Prevents conductivity of the deposited palladium layer.

The activator usually consists of a mineral acid and preferably hydrochloric acid aqueous solution of a palladium colloid. The palladium content in the Solution can range from about 50 mg / l to about 500 mg / l solution, in particular between about 150 mg / l and 250 mg / l solution. A palladium salt is used to make the colloid. In addition tin (II) salt is added to the solution, which in the reaction of the tin (II) salt is partially oxidized with palladium salt to tin (IV) compounds. The Tin content of the solution can range from 2 g / l to 50 g / l, preferably between 10 g / l and 25 g / l solution. The colloid solutions are described in US-A-30 11 920 and US-A-36 82 671 Method made.

When using hydrochloric acid as mineral acid, the concentration range is the hydrochloric acid between 2 wt .-% and 30 wt .-%, preferably between 5 wt% and 15 wt% in water. Have galvanization attempts shown that the activator should be strongly hydrochloric acid. With hydrochloric acid content below 0.5 mol / l solution, there is no longer enough palladium from the activator adsorbed on the surface to allow rapid metal growth during to achieve the metallization.

After the activator treatment, the substrate is rinsed again.

In the process, the reduction ability of the tin (II) compounds is used, order in the subsequent treatment step from a metal, preferably Solution containing copper ions the ions to metal, preferably to metallic copper, and in this way between the To deposit palladium particles of metal, for example copper. Moreover the disruptive tin (II) / tin (IV) layer is removed in this way.

In a special embodiment, this solution is used as a metal compound used a copper compound. However, for example, silver Gold, palladium and other precious metals are suitable. As copper compounds come all compounds that are particularly soluble in aqueous media, for example Salts such as copper sulfate and copper acetate. The concentration of the metal is in the range of 0.1 g / l to 50 g / l aqueous solution and preferably adjusted from 0.5 g / l to 15 g / l solution.

The solution containing metal ions is preferably alkaline. The solution contains an alkali or alkaline earth metal hydroxide and also a complexing agent for the metal. Lithium hydroxide, in particular, has been found to be the alkali metal hydroxide turned out to be cheap. However, other hydroxides are basically such as sodium, potassium, magnesium, calcium or barium hydroxide suitable. Their concentration is in the range from 0.1 mol / l to 3 mol / l aqueous solution, preferably in the range of 0.5 mol / liter to 1.5 mol / liter Solution.

The complexing agent also contained serves to the metal in the alkaline Keep solution solved. Therefore, this must be sufficiently large Have complexation constants for the metal and are present in an amount, to at least prevent the precipitation of metal hydroxides. As suitable complexing agents have in particular compounds such as ethanolamine, Ethylenediaminetetraacetic acid and its salts, tartaric acid and its Salts, citric acid and their salts as well as N, N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine, proven.

The operating temperature of the solution containing the metal ions can be as a whole practical range, but preferably in the range of 30 ° C to 65 ° C and in a preferred embodiment between 50 ° C and 60 ° C can be set.

After treatment with the solution containing metal ions, the substrate rinsed again.

The first reduction of the metal ions can be done by a further reduction step get supported. To do this, add another solution to the substrate contacted that contains reducing agents. Basically everyone comes Reductants into consideration. However, boron / hydrogen compounds have been found found to be the cheapest. For example, sodium borohydride in particular in an alkaline solution or dimethylamine borane in an alkaline or weakly acidic solution well suited to the conductivity of the to further improve the metal layer produced, so that in particular large areas non-conductive substrate surfaces can be metallized well.

The substrate is then rinsed again to remove residues of the reducing agent completely removed from the substrate surface.

After this treatment, the extremely thin layer shows a sufficient high electrical conductivity for the subsequent electrolytic metallization on. All electrodepositable metals can be used on the after Process pretreated substrate surface without further electroless metallization be directly put down. For example, copper Nickel, palladium and other precious metals are suitable. Can on these metals other metals are deposited. It is also possible that to partially cover the first metal layer with dielectric layers in order to make decorative To produce effects or functional properties.

Such dielectric layers can also be placed in front of any of the above Treatment steps applied to the surface of the substrate to prevent metallization at this point.

In particular, bodies made of acrylonitrile / butadiene / styrene copolymers are used as substrates or their mixtures metallized with other non-conductive materials. With chromium (VI) ions containing pretreatment solutions substrates made of polyvinyl chloride in particular are hardly attacked. Therefore, holding elements, such as support frames, are used in electrolytic Metallizing plastics coated with this material, to avoid their metallization during the electrolytic treatment.

The substrates are treated with the treatment solutions by immersion, spraying, Contacted gushes or splashes.

The following examples serve to explain the invention:

Example 1:

1. Die Teile wurden zum Anätzen in ein auf 65 °C erwärmtes Bad aus 360 g/l Chrom(VI)-oxid und 360 g/Liter konzentrierte Schwefelsäure in wäßriger Lösung eingetaucht.

2. Nach sechs Minuten wurde die überschüssige Säure von den Formteiloberflächen abgewaschen und mit einer Lösung aus Natriumhydrogensulfit behandelt, wobei eventuell an den Formteiloberflächen noch anhaftende Chrom(VI)-lonen reduziert wurden.

3. Nach einem weiteren Spülschritt wurde das Formteil kurz in ein Bad aus 300 ml konzentrierte Salzsäure pro Liter wäßrige Lösung eingetaucht und

4. dann eine Minute lang in einen Aktivator, der aus

300 ml konzentrierter Salzsäure,

250 mg Palladium (eingesetzt als Palladium(ll)-chlorid),

17 g Zinn(ll)-chlorid

pro Liter wäßriger Lösung

bestand.

5. Nach dem anschließenden Spülen der Formteiloberflächen wurden diese mit einer Lösung aus

25 g Lithiumhydroxid,

20 g Natriumhydroxid,

4 g Kupfersulfat,

15 g Weinsäure

pro Liter wäßriger Lösung

eine Minute lang bei 60 °C behandelt, wobei auf den Oberflächen adsorbierte Zinnverbindungen vermutlich gegen Kupfer ausgetauscht wurden.

6. Zur Metallisierung wurde das Formteil samt Gestell anschließend in ein handelsübliches schwefelsaures Kupfermetallisierungsbad eingetaucht.

A suitable metal frame was coated with a plastic based on polyvinyl chloride (Tegumit, product from Atotech Deutschland GmbH, Berlin, Germany). After the metallic contact tips of the frame, which were initially isolated by the coating process, were exposed, molded parts / hand shower head) made of the plastic, acrylonitrile / butadiene / styrene (ABS) copolymer, were attached to these tips. The arrangement has now been dealt with in turn in the following solutions:

1. The parts were immersed for etching in a bath of 360 g / l chromium (VI) oxide and 360 g / liter concentrated sulfuric acid heated to 65 ° C. in aqueous solution.

2. After six minutes, the excess acid was washed off the molded part surfaces and treated with a solution of sodium hydrogen sulfite, chromium (VI) ions still adhering to the molded part surfaces being reduced.

3. After a further rinsing step, the molding was briefly immersed in a bath of 300 ml of concentrated hydrochloric acid per liter of aqueous solution and

4. then for a minute in an activator that comes out

300 ml concentrated hydrochloric acid,

250 mg palladium (used as palladium (II) chloride),

17 g of stannous chloride

per liter of aqueous solution

duration.

5. After the subsequent rinsing of the molded part surfaces, they were washed out with a solution

25 g lithium hydroxide,

20 g sodium hydroxide,

4 g copper sulfate,

15 g tartaric acid

per liter of aqueous solution

treated for one minute at 60 ° C, whereby tin compounds adsorbed on the surfaces were probably exchanged for copper.

6. For the metallization, the molded part including the frame was then immersed in a commercially available sulfuric acid copper metallization bath.

A uniformly shiny copper layer was deposited exclusively on the ABS molded parts within one hour at a current density of 2 A / dm ² . No copper deposits were found on the supports covered with polyvinyl chloride. The metal layers had an adhesive strength of more than 1 N / mm in the peel test according to the DE standard DIN.

Example 2:

The process described in Example 1 was repeated, but in process step 6 with a nickel bath (Watts type) instead of the sulfuric acid Copper bath. The same result was obtained with regard to the selectivity of the process as well as the adhesive strength of the deposited metal layer reached.

Example 3:

An ABS sample was partially coated with a polyester layer and then treated as described in Example 1.
The polyester layer was not metallized.

Example 4:

A molded part (telephone housing), which in a so-called two-shot process in the injection molding process partially made of ABS-containing plastic (Cycoloy C1100 from General Electric Plastics, Ruesselsheim, Germany) and partly from a polyamide (Noryl GTX924 from General Electric Plastics) was treated as described in Example 1. Only the ABS-containing plastic was covered with metal, while the Polyamide surface was completely metal-free.

Example 5:

Analogously to Example 1, a frame with attached ABS molded parts was immersed in a solution heated to 45 ° C. for two minutes before conditioning after process step 3 (pre-immersion) to condition the ABS surfaces
1 g of the polymer Luresin KNU (product from BASF, Ludwigshafen, Germany) per liter of aqueous solution
contained. After this treatment step, both the ABS surfaces and the tegumite surface of the frame were metallized.

Example 6:

1. bei Raumtemperatur fünf Minuten lang in eine Lösung aus

700 g Diethylenglykolethyletheracetat

pro Liter Wasser

zum Anquellen getaucht und

2. anschließend 6 Minuten lang bei 70 °C in einer Lösung aus

380 g CrO₃

380 g konzentrierte Schwefelsäure

20 g Cr₂O₃

0,1 g Fluortensid (FC 95 von 3M Corp., USA)

pro Liter wäßriger Lösung

zum Anätzen behandelt.

3. Nach dem Abspülen der überschüssigen Ätzlösung wurden noch anhaftende Chrom (Vl) - Reste in einer Lösung aus

40 g Natriumbisulfit

pro Liter wäßriger Lösung

entfernt.

4. Das Formteil wurde nun drei Minuten lang bei 35 °C in einer Lösung aus

150 ml konzentrierte Schwefelsäure,

220 mg Palladiumkolloid,

30 g Zinn(ll)-chlorid

pro Liter wäßriger Lösung

aktiviert,

5. abgespült, eine Minute lang bei 60 °C in einer Lösung aus

4 g Kupfersulfat,

150 g Weinsäure,

20 g Natriumhydroxid,

20 g Lithiumhydroxid Hydrat

pro Liter wäßriger Lösung

behandelt.

6. Anschließend wurde nach Spülen das Formteil mit einem handelsüblichen Kupfermetallisierungselektrolyten (Cupracid HT der Firma Atotech Deutschland GmbH) dekorativ beschichtet. Das Formteil war nach 7 Minuten vollständig mit Kupfer bedeckt. Die Kupferschicht wurde nach Prüfung in demselben Bad 45 Minuten lang weiterbehandelt, wobei sich eine Schicht von 25 µm Dicke abschied.

A molded part (car grille) made of polycarbonate (Lexan BE from General Electric Plastics) was

1. in a solution at room temperature for five minutes

700 g of diethylene glycol ethyl ether acetate

per liter of water

dipped to swell and

2. then in a solution at 70 ° C for 6 minutes

380 g CrO ₃

380 g concentrated sulfuric acid

20 g Cr ₂ O ₃

0.1 g fluorosurfactant (FC 95 from 3M Corp., USA)

per liter of aqueous solution

treated for etching.

3. After the excess etching solution had been rinsed off, any chromium (VI) residues still remaining were removed in a solution

40 g sodium bisulfite

per liter of aqueous solution

away.

4. The molded part was then in a solution at 35 ° C for three minutes

150 ml concentrated sulfuric acid,

220 mg palladium colloid,

30 g of stannous chloride

per liter of aqueous solution

activated,

5. rinsed out in a solution at 60 ° C for one minute

4 g copper sulfate,

150 g tartaric acid,

20 g sodium hydroxide,

20 g lithium hydroxide hydrate

per liter of aqueous solution

treated.

6. After rinsing, the molded part was then decoratively coated with a commercially available copper metallization electrolyte (Cupracid HT from Atotech Deutschland GmbH). The molded part was completely covered with copper after 7 minutes. After testing in the same bath, the copper layer was further treated for 45 minutes, with a layer of 25 μm thickness separating.

Example 7:

Analogous to the experiment described in Example 1, ABS molded parts were treated.

The surface conductivity of the layer formed before the metallization was measured. After the treated molded part has been rinsed and dried, a resistance measurement with two measuring electrodes took place, which were at a distance of 1 cm were pressed onto the treated surface of the molded part.

The lateral progression of the copper layer was also determined.

A surface conductivity of approximately 50 pSiemens (µS) was measured. A metallized surface formed on the molded parts, the Metallization front within 1.5 minutes by 9 cm from the contact point had removed the molded part.

Fig. 1 shows the conductivity in µS and the growth of the metal front in cm after 1.5 minutes (process step 6) the concentration of hydrochloric acid (mol / l) in the activator (process step 4). The empirical values indicate that the conductivity is almost increasing linearly with the acid concentration, while the metal deposition rate, after a steep rise above a minimum concentration cannot be increased in proportion to the concentration.

Example 8

Example 7 was repeated and the samples were examined depending on different parameters.
The growth of the metal front on the substrate surface, starting from the cathode, was measured. The results are shown in the tables below and shown graphically in the figures. 15 cm long and 6 cm wide sheets of ABS were treated as samples according to the invention, then contacted on one narrow side and copper-plated.
Table 1 shows the spread of the metal front of two samples up to a metallization time of 2.5 minutes at a galvanizing voltage of 0.6 volts.
Table 2 shows the calculated growth rate (cm / min) from a large number of samples metallized at different electroplating voltages at different times since the start of metallization.
It is striking that the maximum growth rate is reached about 2 minutes after the start of the coating and then remains approximately constant. These table values have been transferred in Figure 2.
Table 3 and Figure 2 show that the growth rate is dependent on the bath temperature during the treatment according to process step c) in claim 1 and step 5 in examples 1 and 8, respectively.
With residence times in this bath (Cu-LINK) of 1 to 10 min at temperatures of 27 ° C, 45 ° C, 60 ° C, there are different metallization times in the electrolytic copper bath for the 15 x 6 cm size samples used. With a low and / or short dwell time, a low conductivity is set on the substrate, which results in correspondingly long metallization times.
On the other hand, it can be seen that between about 45 ° C and 60 ° C bath temperature with the same residence time there is hardly any difference in the coating time and thus the average growth rate. On the other hand, if the residence time in the Cu-LINK bath is extended, the deposition rate in the metallization bath can be increased or the residence time there shortened. Time [min] Sample 1 Path [cm] sample 2 Average 0 0 0 0 ½ <0.5 0.7 ~ 0.5 1 2.8 2.5 2.7 1½ 6.5 7.5 7.0 2nd 8.5 10th 9.3 2½ 12.5 10th 11.3 Time [min] Electroplating voltage [V] 0.45 0.60 0.80 1.00 0 0 0 0 0 ½ 0.4 2.2 2.5 0.8 1 2.6 2.8 4.3 7.7 1½ 2.0 3.8 5.5 9.0 2nd 2.4 3.9 5.7 9.5 2½ 2.6 4.2 5.1 3rd 2.6 3.8 3½ 3.4 3.8 4th 3.0 4½ 3.0 5 3.0 Time [min] Temperature [° C] 27 45 60 1 10.0 9.0 3rd 8.0 10.0 5 6.0 5.5 7 6.0 5.2 5.5 10th 5.0 4.0 3.2

Claims (7)

1. Method of selectively electrolytically metallising moulded plastics material parts from electrically non-conductive materials, which are secured, for the following treatment, on retaining elements which are coated with plastics material and are not to be metallised, including the method steps:

   a) selecting polyvinyl chloride for coating the retaining elements with plastics material;

   b) pretreating the moulded plastics material parts by means of an etching solution containing chromium (VI) oxide;

   c) subsequently treating the moulded plastics material parts with a colloidal acidic solution of palladium/tin compounds, so as to avoid prior contact between the material for the retaining elements and adsorption-promoting solutions;

   d) treating the moulded plastics material parts with a solution, containing a soluble metal compound, which is reducible by means of tin (II) compounds, an alkaline-metal or alkaline-earth metal hydroxide and a complex former for the metal in a quantity which prevents at least the precipitation of metal hydroxides; and

   e) electrolytically metallising the moulded plastics material parts.
2. Method according to claim 1, characterised in that the moulded plastics material parts are partially metallised when, prior to the method being accomplished, parts of the surfaces of the moulded plastics material parts are covered with a material selected from the group consisting of polyvinyl chloride, polyester or polyamide.
3. Method according to one of the preceding claims, characterised in that the moulded plastics material parts are rinsed between some or all of the method steps.
4. Method according to one of the preceding claims, characterised by a copper compound as the soluble metal compound.
5. Method according to one of the preceding claims, characterised by lithium hydroxide as the alkali hydroxide.
6. Method according to one of the preceding claims, characterised by tartaric acid and/or tartrate as the complex former.
7. Method according to one of the preceding claims, characterised in that moulded plastics material parts of materials formed from acrylonitrile/ butadiene/styrene copolymers or their mixtures with other non-conductive materials or formed from polycarbonate are metallised.

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