CA2210883A1 - Method of selective or partial electrolytic plating of surfaces of substrates comprising non-conductive material - Google Patents

Abstract

The invention relates to a method of selective or partial electrolytic metallisation of surfaces of substrates made of electrically non-conductive materials, which are secured for metallisation on holding members coated with plastics.
The method comprises the steps:
a) pre-treating the surfaces by means of an etching solution containing chrome (Vl) oxide, b) then treating the surfaces with a colloidal acidic solution of palladium/tin compounds, avoiding previous contact with adsorption-promoting solutions, c) treating the surfaces with a solution containing a soluble metal compound which can be reduced by means of tin (ll) compounds, an alkali or earth alkali metal hydroxide and a complex former for the metal in a quantity at least preventing the precipitation of metal hydroxides, d) treating the surfaces with a solution for electrolytic metallisation.

By means of the method it is possible that only the workpiece surfaces are metallised, but not the holding members or non-conductive plastics layers partially applied if necessary to the workpieces. Further, with this method large-area plastic surfaces may also be directly electrolytically metallised without previous electroless metallisation.

Description

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Method of Selective or Partial electrolytic Plating of Surfaces of Substrates comprising non-conductive Material . .
Specification:
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The invention relates to a method of selective or partial electrolytic metallisation of surfaces of substrates made of electrically non-conductive materials, which are secured on holding members coated with plastics for subsequent treatment.
Various methods are known of coating non-conductive surfaces. In wet chemical methods, the surfaces to be metallised are, after an appropriate preliminary treatment, either firstly catalysed and then metallised in a electroless manner and thereafter if necessary metallised electrolytically, or 15 are directly electrolytically metallised.

Methods according to the first variant with electroless metallisation have however proved disadvantageous, as process management of the electroless metallising bath is difficult, treatment of the waste water from 20 this bath is complex and expensive, and the process is lengthy and thus likewise expensive due to the low deposition speed of the metallising bath.

Especially for metal coating of plastic parts, for example for sanitary fittingsand for the automobile industry, and of parts which are used as casings for 25 electrical appliances which are screened against electromagnetic radiation, the electroless metallising methods are problematic. In treatment of such . CA 02210883 1997-07-18 moulded parts, generally relatively large volumes of the treatment solutions are carried over from one treatment bath into the next, as these have a shape by means of which the treatment solution is transported out of the baths when the parts are lifted out. As electroless metallising baths 5 normally contain considerable quantities of toxic formaldehyde and complex formers which are only removable with difficulty, in their treatment large quantities of these baths are lost and must be disposed of in a complicated manner.
. .

10 For this reason a series of metallising rnethods was developed, by means of which the non-conductive surfaces could be directly coated with metal without electroless metallisation. Such methods however are especially described for metallising the walls of boreholes in printed circuit boards.
Direct electrolytic metallisation in metallisation of boreholes is however 15 considerably simpler compared to metal coating of other plastics parts such for example as sanitary fittings, or of distinct three-dimensional contour contrary to panels, as smaller surfaces require to be metallised. The areas of the non-conductive substrate surface to be overcome during metallisation is shorter in the case of metallisation of boreholes on printed circuit boards, 20 and therefore may be achieved more easily.

There is described in EP 0 298 298 A2 a method for electrolytic metallisation of a non-conductor, in which the non-conductive surface to be metallised is coated with a metallic chalcogenide. The metal chalcogenide is 25 formed by treating the surfaces with a palladium colloid containing tin compounds as a protective coiloid, and subsequent treatment with a soluble metal chalcogenide compound, preferably a metal sulphide.

A similar method is disclosed in the publication US-A-49 19 768. Here a 30 method is described in which the non-conductive surface is firstly treated with a tin (Il) salt, then with a dissolved sulphide and thereafter with a solution containing hydrochloric acid and a palladium sait. The pre-treated surface is then electrolytically metallised.

EP 0 320 601 A2 describes a method for metallising non-conductors, in 5 which the non-conductive surfaces are firstly treated with a permanganate solution, an insoluble manganese dioxide forming on said surfaces. The manganese dioxide layer is then converted by treatment with a solution containing chalcogen compounds, preferably sulphur compounds.
Thereafter a metal layer can be electrolytically deposited.

By means of the methods named, a chalcogenide layer of sufficiently high electrical conductivity can in fact be formed by means of a special pre-treatment for subsequent metallisation of boreholes in printed circuit boards. However, the conductivity of such a layer is insufficient for 15 metallising large-area non-conductive substrates, as there non-conductive paths which are too great must be bridged over from the contact points of the current supply. In metallisation, the chalcogenide layer is destroyed in the vicinity of the contacting points.

In US-A-39 84 290 a method is disclosed in which the borehole walls of a printed circuit board are firstly treated in a solution containing a compound of a metal more noble than copper, a metal coating forming on the copper surfaces of the printed circuit board and on the non-conductive surfaces.
Thereafter the metal coating is again removed from the copper surfaces, and then the metal coating on the non-conductive surfaces, and the copper surfaces, are electrolytically metallised.

A further method of direct electrolytic metallisation is described in DE 33 23 476 C2. The non-metallic articles to be metallised are firstly treated with a solution containing a noble metal, for example with a palladium activator stabilised by tin compounds, and is then electrolytically coated in .

a metallising bath. The metallising bath contains appropriate organic additives, by means of which preferred metal deposition is promoted on the metal coatings formed in the preceding process step, on the non-conductive areas.

There is disclosed in the publication DE 37 41 459 C1 a method of manufacturing through-contacted printed circuit boards by direct electrolytic metal deposition on catalytically activated surfaces of the base material, in which the surfaces are pre-treated, before electrolytic metallisation, with a 10 solution containing one or more organic Gornpounds containing nitrogen, for example polyvinyl pyrrolidone, 2,2,6,6-tetramethyl-4-piperidone, pyridinium propyl sulphobetain or a polymeric, polyquaternary ammonium chloride.

In EP 0 456 982 A1 there is disciosed a method of electrolytic metaliisation 15 of a substrate, in which the substrates are firstly catalysed for example in a solution containing a palladium colloidal solution stabilised with tin compounds, then in a known way the tin compounds are removed from the substrate surface, the solution used for this purpose in addition containing the compound of a metal which is nobler than tin, and the surfaces are then 20 electrolytically metallised.

Even with this method also it is only possible to metallise borehole walls in printed circuit boards, as the conductivity of the layer formed is insufficient to metallise larger non-conductive surfaces.
An entirely different method is described in W0 89/08375 A1. The methodlikewise serves to manufacture through-contact printed circuit boards.
However, a first conductive layer is formed for subsequent electrolytic metallisation from conductive polymers, the non-conductive surfaces firstly 30 being treated with a permanganate solution, so that manganese dioxide precipitates on the treated areas, the printed circuit board, after excess treatment liquid has been rinsed off, being immersed in a solution containing a monomer from the group of the pyrroles, furanes or thiophenes, and the substrate is then brought into contact with an acidic solution, a conductive polymer layer forming from the liquid film containing 5 the monomer on the borehole walls. This can then be directly electrolytically metallised.

In the German disclosure document 39 07 789 A1 a method of deposition of an electrically conductive layer on an electrically non-conductive surface 10 is indicated, in which there is firstly produced on the surface an electrically conductive base layer, produced by an electroless chemical polymerisation from at least one conductive polymer on the surface, and then a further electrically conductive layer, for example a further conductive polymer layer or a metal layer, is deposited. By means of this method even substrates 15 with larger non-conductive surfaces can be directly electrolytically metallised, if the abovenamed method procedure is repeated several times.
This is however not practicable, as it leads to extraordinarily long process times.

20 In addition, the conductive polymer layers formed on the surfaces have a sufficiently high conductivity only a short time after their manufacture.
Thereafter this deteriorates rapidly, so that large-area metallisation is still not possible.

In EP 0 616 0~3 A1 there is disclosed a method for direct metallisation of non-conductive surfaces, in which the surfaces are firstly treated with a cleaner/conditioner solution, thereafter with an activator solution, for example a palladium colloidal solution, stabilised with tin compounds, and are then treated with a solution which contains compounds of a metal which is more noble than tin, as well as an alkali hydroxide and a complex former. Thereafter the surfaces can be treated in a solution containing a reducing agent, and can finally be electrolytically metallised.

By means of the known methods, usualiy only direct electrolytic metallisation of small surfaces, e.g. borehole walls of printed circuit boards, 5 is possible; metallisation of large plastics surface fails in most cases due to the lack of capacity for metallisation of the layers which are formed on the non-conductive surfaces.

For industrial large-scale application of direct electrolytic metallisation of 10 plastics parts which are intensely structured, such for example as combs or articles designed with a substantial extension in the third dimension, e.g.
coffee pots, telephone handsets, water pipe fittings, the workpieces must be secured on support frames, which may not be coated during the metallising process, because this metallic layer leads to disruption of 15 production. Otherwise the metal layers must be again removed from the support frames after the workpieces have been coated. This entails an additional outlay for removal of coatings, in conjunction with the consumption of chemicals. Moreover, in this case the productivity of the metallisation installation is lower, as the frames must first be demetallised 20 before being again loaded with workpieces.

Therefore the problem underlying the present invention is to avoid the disadvantages of prior art and to find a method for selective or partial electrolytic metallisation of surfaces of substrates made of electrically non-25 conductive materials, which are secured on holding members, for examplesupport frames, which are externally covered with plastics.

This ,~roblem is solved by claims 1, 7 and 8. Preferred embodiments of the invention are indicated in the secondary claims.
The method according to the invention comprises the following process . CA 02210883 1997-07-18 steps:

a) pre-treating the surfaces by means of an etching solution containing chrome (Vl) oxide, b) then treating the surfaces with a colloidal acidic solution of palladium/tin compounds, avoiding previous contact with adsorption-promoting solutions, :
10 c) treating the surfaces with a sol~tion containing a soluble metal compound which can be reduced by means of tin (Il) compounds, an alkali or earth alkali metal hydroxide and a complex former for the metal in a quantity at least preventing the precipitation of metal hydroxides, 15 d) treating the surfaces with a solution for electrolytic metallisation.

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

20 According to prior art, particularly in the production of printed circuit boards, so-called conditioning solutions are used as adsorption-promoting solutions. These are usually aqueous solutions, containing in particular polyelectrolytes such for example as polycationic polymers, with a molecular weight of above 10,000 g/Mol. After treatment of the non-25 conductive surfaces with such a conditioning solution, not only the plasticssurfaces to be metallised as desired are coated with metal, but also, superfluously, the holding members externally covered with plastics.

By means of the method according to the invention on the other hand it is 30 not necessary to remove metal again from the holding members after use, as the substrates are not brought into contact with a conditioning solution.

~ CA 02210883 1997-07-18 .

Rather, the holding members, after metallisation of the substrate surfaces and removal of the metallised substrates, are directly returned without further treatment to the production circuit, and are loaded with further non-conductive substrates for direct metallisation. Should metals have been 5 deposited on the contact points/metal points during metallisation, these should be removed from time to time, in order to avoid contact problems and impurities in the bath.

No additional cleaning and etching steps are necessary for demetallising the 10 frame parts Iying beneath the contact points. In this way the outlay for disposal of waste water is reduced also. Moreover, fewer chemicals are consumed. The productivity of the metallising installation is also increased, as with a given number of existing holding members, a larger number of substrates to be metallised can be treated.

A prerequisite is however that, before treatment of the substrates with the activator, said substrates should in no way come into contact with agents which promote adsorption of the colloidal particles.

20 In addition to the solutions known to the person skilled in the art, note should above all be taken here of any contaminated rinsing water, particularly when circuit water is used in the factory.

Carry-over from conditioning baths of parallel manufacturing installations 25 into this water circuit is to be avoided, as is the introduction of agents which can act in the same way as the adsorption-promoting polyelectrolytes. Therefore the parallel use of frames both for production of printed circuit boards as well as for the purpose according to the invention is not meaningful.
A further advantage of the method resides in the fact that the surfaces of the substrates to be metallised can also be partly metallised, parts of the surfaces being covered by a suitable material. As this material also is not coated during execution of the method according to the invention, subsequent removal of the material is extremely easy to carry out, without 5 damaging the metal coatings on the metallised substrate during any necessary treatment for selective removal of the metal deposited at that point.

The method is particularly suitable for three-dimensionally structured 10 electrically non-conductive moulded partsr whose enveloping surface, i.e.
the smallest possible area of an envelope of an object, is considerably smaller than its surface, for example for plastics parts for the sanitary area, automobile construction, or for housings to be electrically screened, as their disadvantage of transporting the treatment solutions out of the baths can in 15 practice only be avoided to an unsatisfactory degree. By means of direct electrolytic metallisation in the method according to the invention without preceding electroless metallisation, smaller quantitfes of toxic waste water containing compiex formers occur than with previous methods of metallisation of plastics.
Therefore the method according to the invention is in all more cost-effective, less complex and more environmentally friendly than methods known from prior art.

25 Under circumstances known to the expert it can be necessary, depending on the substrate to be metallised, firstly, before the start of the method according to the invention, to swell the substrate in an organic solvent, such for example as a diethyiene glycol or ethylene glycol derivate, dimethylformamide or in other polar or non-polar solvents. These solvents 30 can aiso be used in mixture with water. Particularly preferred treatment agents have additional added alkalisation agents such as for example . CA 02210883 1997-07-18 .

alkalihydroxides or tetraalkyl ammonium hydroxides. Depending on the type of substrate to be treated, the solutions can be used at ambient temperature or at an increased temperature.

5 According to the invention, in process step a), the surfaces to be metallised are pre-treated in an etching solution. This normally involves a solution containing chromic acid, which can in addition also contain sulphuric acid.
Solutions preferred are those which contain 360 g chrome (Vl) oxide and 360 g concentrated sulphuric acid in a litre of water. The solution is heated 10 for the treatment-to a temperature for example of 60~C. According to the non-conductive substrate to be metallised, the treatment time comes to between 2 and 16 minutes.

For specific substrate materials, permanganate solutions may be used 15 instead of solutions containing chromic acid, for example those containing 100 g/l to 150 g/l sodium permanganate and 30 g/l to 60/l sodium hydroxide in aqueous solution.

After a rinsing treatment, chrome (Vl) compounds adhering to the substrate 20 surfaces are reduced to chrome (Ill) compounds. In a permanganate treatment, manganese oxide deposits are likew;se reductively removed. For this purpose for example an acidic aqueous solution of sodium hydrogen sulphite can be used. However all other reduction agents, such for example as hydroxylamine, are suitable.
After a further rinsing treatment, the substrate can be treated in a solution of 300 ml/l concentrated hydrochloric acid or another mineral acid, such for example as concentrated sulphuric acid, in aqueous solution. This treatment is useful in order to avoid the continuous dilution by rinsing water of the 30 activator solution with which the substrate is then treated. As the activator contains also tin compounds as well as palladium compounds, the mineral . CA 02210883 1997-07-18 acid treatment solution can additionally also contain these tin compounds.
In this way the carry-over losses are partly compensated for. The treatment time in this preliminary immersion solution can be varied within wide limits.
The only important factor is that the surfaces of the substrate are entirely 5 wetted. Any bath temperatures can be selected.

The success of the method is presumably based on the fact that the adsorption of palladiurn particles from a colloidal solution is used to cover the non-conductive su*ace with a large number of palladium particles. As 10 the palladium par~icles originate from a colloidal solution, these after adsorption are surrounded by a protective colloidal envelope, which prevents the electrical conductivity of the deposited palladium layer.

The activator normally consists of a mineral acid and preferably 15 hydrochloric aqueous solution of a palladium colloid. The palladium content in the solution can be adjusted in a range from about 50 mg/l to about 500 mg/l solution, particularly between about 150 mg/l and 250 mg/l. A
palladium salt is used to produce the colloid. In addition tin (Il) salt is added to the solution, which is partly oxidised into tin ~IV) compounds during the 20 reaction of the tin (Il) salt with palladium salt. The tin content of the solution can be adjusted in a range from 2 g/l to 50 g/l solution, preferably between 10 g/l and 25 9/1 solution. The colloidal solutions are produced according to the method described in US-A-30 11 920 and US-A-36 82 671 .
When hydrochloric acid is used as a mineral acid, the concentration range of the hydrochloric acid lies between 2% by weight and 30% by weight, preferably between 5% by weight and 15% by weight in water.
Electroplating experiments have shown that the activator must be intensely 30 hydrochloric. With hydrochloric acid contents of beneath 0.5 Mol/l solution, sufficient palladium is no longer adsorbed from the activator on the surface CA 022l0883 l997-07-l8 to achieve a rapid metal growth during metallisation.

After the activator treatment, the substrate is again rinsed.

5 In the method, the reduction capacity of the tin (Il) compounds is used in order in the subsequent treatmen~ step, from a solution containing metal, preferably copper ions, to reduce the ions to metal, preferably to metallic copper, and in this way to deposit metal, for example copper, between the palladium particles. Moreover, in this way the disruptive tin (Il)/tin (IV) layer 10 is removed.

In a special embodiment, a copper compound is used as a metal compound in this solution. However, silver, gold, palladium and other noble metals for example are also suitable. All compounds, especially soluble in aqueous 15 media, for example salts, such as copper suiphate and copper acetate, are considered as copper compounds. The concentration of the metal is adjusted in a range from 0.1 g/l to 50 g/l aqueous solution and preferably from 0.5 g/l to 15 s3/l solution.

20 The solution containing metal ions is preferably alkaline. The solution contains an alkaline or earth alkali metal hydroxide and further a complex former for the metal. Lithium hydroxide has proved particularly favourable as an alkali metal hydroxide. However, basically also other hydroxides, such for example as sodium, potassium, magnesium, calcium or barium 25 hydroxides, are suitable. Their concentration lies in a range from 0.1 Mol/l to 3 Mol/l aqueous solution, preferably in a range from 0.5 Mol/litre to 1.5 Mol/litre solution.

The complex former also contained serves to keep the metal dissolved in 30 the alkaline solution. Therefore the said complex former must have a sufficien~ly large complex formation constant for the metal, and be present ' CA 02210883 1997-07-18 .

in a quantity at least sufficient to prevent the precipitation of metal hydroxides. In particular compounds such as ethanolamine, ethylene diamine tetracetic acid and their salts, tartaric acid and its salts, citric acid and its saits and N,N,N',N'-tetrakis-(2-hydroxypropyl)-ethylene diamine, 5 have proved particularly suitable as complex formers.

The operational temperature of the solution containing the metal ions can be adjusted in the overall practicable range, preferably however in the range from 30~C to 65~C arid, in a preferred embodiment, between 50~C and 10 60~C. - .

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

15 The first reduction of the metal ions can be reinforced by a further reduction stage. For this purpose the substrate is brought into contact with a further solution which contains reducing agents. Basically, all reducing agents can be considered. However, boron/hydrogen compounds have proved most favourable. For example, in particular sodium borohydride in an 20 alkaline solution or dimethylaminoborane in an alkaline or weakly acidic solution are well suited further to improve the conductivity of the metal layer produced, so that in particular large-area non-conductive substrate surfaces can be efficiently metallised.

25 The substrate is again rinsed in order totally to remove residues of the reducing agent from the substrate surface.

After this treatment, the extremely thin layer has a sufficiently high electrical conductivity for the subsequent electrolytic metallisation. All 30 electrolytically depositable metals can be directly precipitated on the substrate surface pre-treated according to the method, without further .

.

electroless metallisation. For example copper, nickel, palladium and other noble metals are suitable for this purpose. Further metals can be deposited on these metals. In addition it is also possible partly to cover the first metallayer with dielectric layers, in order to bring about decorative effects or 5 functional properties.

Such dielectric layers can also be applied to the surface of the substrate before each of the treatment steps described above, in order to suppress metallisation at this polnt.

As substrates, in particular bodies of acrylonitrile/butadiene/styrol-copolymers or their mixtures with other non-conductive materials can be metallised. Substrates in particular comprising polyvinyl chloride are scarcely attacked by pre-treatment solutions containing chrome (Vl) ions.
15 Therefore for example holding members such as support frames can be covered with this material during the electrolytic metallisation of plastics, inorder to avoid their metallisation during the electrolytic treatment.

The substrates are brought into contact with the treatment solutions by 20 immersion, spraying, splashing or squirting.

The following examples serve to explain the invention:

25 Example 1:

A suitable metal frame was coated with a plastic based on polyvinyl chloride (Tegumit, product of the Company Atotech Deutschland GmbH, Berlin, Germany). After uncovering the metallic contact points of the frame 30 at first insulated by the coating procedure, moulded parts (manual shower head) of the plastic acrylonitril/butadiene/styrol-(A8S)-copolymer to be metallised, were secured to these points. The arran~ement was then treated in sequence in the following solutions:

1. The parts were immersed in a bath heated to 65~C comprising 360 g/l chrome (Vl) oxide and 360 g/litre concentrated sulphuric acid in aqueous solution, for initial etching.

2. After 6 minutes, the superfluous acid was washed off the surfaces of the moulded parts, and they were treated with a solution of sodium hydrogen sulphltè, any chrome (Vl~ ior!s stiU adhering to the surfaces of the moulded parts being reduced.

3. After a further rinsing step, the moulded part was briefly immersed in a bath of 300 ml concentrated hydrochloric acid per litre aqueous solution 1 5 and 4. then for one minute in an activator comprising 300 ml concentrated hydrochloric acid 250 mg palladium (used as palladium (Il) chloride), 17 g tin (Il) chloride per litre of aqueous solution 5. After the following rinsing of the surfaces of the moulded parts, they were treated for one minute at 60~C in a solution of 25 9 lithium hydroxide, 20 g sodium hydroxide 4 g copper sulphate 15 9 tartaric acid per litre of aqueous solution tin compounds adsorbed on the surfaces presumably being exchanged for copper.

6. For metallisation, the moulded part along with the frame was then 5 immersed in a commercially available sulphuric acid copper metallisation bath .

Within one hour at a current density of 2 A/dm2, a uniform brilliant copper layer was deposited exclusively on the ABS moulded parts. No copper 10 deposits were fo~: nd on the support frames covered with polyvinyl chloride.
The metal layers in a peel test according to the German standard DIN had an adhesive strength of more than 1 N/mm.

Example 2:

The method described in Example 1 was repeated, however in process step 6 with a nickel bath (Watts type) instead of the sulfuric acid copper bath.
The same result was achieved as regards selectivity of the method and adhesive strength of the deposited metal layer.
Example 3:

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

Example 4:

30 A moulded part (telephone casing) which had been produced in a so-called two-shot method in the injection moulding process partly from plastic containing ABS (Cycoloy C1100 of the Firm General Electric Plastics, Russelsheim, Germany) and partly of a polyamide (Noryl GTX924 of the Firm General Electric Plastics) was treated as described in Example 1. Only the plastic containing ABS was covered with metal, while the polyamide 5 surface was entirely free of metal.

Example 5:

Similarly to Example i; for comparison a frame with ABS moulded parts 10 secured thereon was immersed before treatment according to method stage 3 (pre-immersion), for two minutes for conditioning of the ABS surfaces in a solution heated to 45~C, which contained 1 g of the polymer Luresin KNU (product of the Firm BASF, Ludwigshafen, 15 Germany) per litre aqueous solution After this treatment step both the ABS surfaces and the Tegumit surface of the frame were metallised.

20 Example 6:

A moulded part (automobile radiator grill) of polycarbonate (Lexan BE of the Firm General Electric Plastics) was 25 1. Immersed for swelling at ambient temperature for 5 minutes in a solution of 700 9 diethylene glycol ethyl ether acetate per litre of water and 2. Then treated for initial etching for 6 minutes at 70~C in a solution containing 380 9 CrO3 380 g concentrated sulphuric acid 20 g Cr203 0.1 g fluorotenside (FC 95 of 3M Corp., USA) per litre aqueous solution .

10 3. After rins;r~g off the excess etching 501ution, chrome (Vl) residues still adhering were removed in a solution of 40 g sodium bisulphite per litre aqueous solution 4. The moulded part was now activated for 3 minutes at 35~C in a solution of 150 ml concentrated sulphuric acid Z20 mg palladium colloid 30 g tin (Il) chloride per litre aqueous solution 5. Rinsed, and treated for 1 minute at 60~C in a solution of 4 g copper sulphate 150 g tartaric acid 20 g sodium hydroxide 20g lithium hydroxide hydrate per litre of aqueous solution 6. Then, after rinsing, the moulded part was provided with a decorative coating with a commercially available copper metallisation electrolyte (Cupracid HT of the Firm Atotech Deutschland GmbH). After 7 minutes, the moulded part was entirely covered with copper. After testing, the copper 5 layer was further treated in the same bath for 45 minutes, and a layer of 25,um thickness was deposited.

Example 7:

10 ABS moulded parts were treated similarly to the experiment described in Example 1.

The surface conductivity of the layer formed was measured before metallisation. After the treated moulded part had been rinsed and dried, 15 resistance measurement was undertaken with two measuring electrodes, which were pressed on to the surface of the treated moulded part at a spacing of 1 cm.

The lateral progress of the copper layer was also determined.
A surface conductivity of about 50 ,uSiemens (,uS3 was measured. A
metallised surface formed on the moulded parts, the metallisation front having moved within 1.5 minutes by 9 cm from the contacting point of the moulded part.
Figure 1 shows the conductivity in,uS and the growth of the metal front in cm after 1.5 minutes (process step 6) of metallising time in dependence on the concentration of the hydrochloric acid (Mol/l) in the activator (method step 4). The empirical values show that the conductivity increases almost 30 linearly with the acid concentration, while the metal deposition rate, after a steep rise above a minimum concentration, cannot be increased -proportionately to the concentration.

Example 8:

Example 7 was repeated and the samples investigated in dependence on various parameters.

The growth of the metal front on the substrate surface, proceeding from the cathode, was measured. The results are shown in the following tables and illustrated g;aphically in the Figures. As samples, panels of ABS 15 cm long and 6 cm wide were treated according to the invention, then contacted on a narrow side and copper-plated.

Table 1 shows the propagation of the metal front of two samples up to a metallisation time of 2.5 minutes at an electroplating voltage of 0.6 volts.

Table 2 shows the calculated growth speed (cm/min) from a plurality of samples metallised at various electroplating voltages at various points in time from the beginning of metallisation.
It is notable that about 2 minutes after the start of coating the maximum growth rate has been reached and then remains approximately constant.
These table values have been transferred to Figure 2.

Table 3 and Figure 2 show that the growth rate is dependent on the bath temperature during the treatment according to method step c) in claim 1 or step 5 in Examples 1 and 8.

During holding times in this bath (Cu-LlNK) of 1 to 10 minutes at the temperature 27~C, 45~C, 60~C, different metallisation durations result in the electrolytic copper bath for the samples used, 15 x 6 cm in size. At low CA 022l0883 l997-07-l8 and/or short duration time, a low conductivity is set on the substrate, so that correspondingly long metallisation times result.

On the other hand it is to be recognised that at a bath temperature between 5 about 45~C and 60~C at the same duration time, scarcely any difference exists in the coating duration and thus in the average growth rate. When the duration time in the Cu-LlNK bath is extended, on the other hand, the deposition speed in the metallisation bath can be increased, or the duration time at that point can be shortened.
.

Claims (8)

Claims:

1. Method of selective electrolytic metallisation of moulded plastics parts made of electrically non-conductive materials, which are secured for the subsequent treatment on holding members coated with plastics and not to be metallised, comprising the method steps:
a) Selection of a material for plastics coating of the holding members from the group polyvinyl chloride, polyester or polyamide, b) pre-treating the plastics moulded parts by means of an etching solution containing chrome (Vl) oxide, c) then treating the plastics moulded parts with a colloidal acidic solution of palladium/tin compounds, avoiding previous contact of the material for the holding member with adsorption-promoting solutions, d) treating the plastics moulded parts with a solution containing a soluble metal compound which can be reduced by means of tin (ll) compounds, an alkali or earth alkali metal hydroxide and a complex former for the metal in a quantity at least preventing the precipitation of metal hydroxides, e) electrolytic metallisation of the plastics moulded parts.

2. Method according to claim 1, characterised in that the plastics moulded parts are partially metallised, parts of the surfaces of the plastics moulded parts being covered before execution of the method with a material selected from the group polyvinyl chloride, polyester or polyamide.

3. Method according to one of the preceding claims, characterised in that the moulded plastics parts are rinsed between some or all the method steps.

4. Method according to one of the preceding claims, characterised by a copper compound as a soluble metal compound.

5. Method according to one of the preceding claims, characterised by lithium hydroxide as an alkali hydroxide.

6. Method according to one of the preceding claims, characterised by tartaric acid and/or tartrate as a complex former.

7. Method according to one of the preceding claims, characterised in that plastics moulded parts of materials consisting of acrylonitrile/butadiene/styrol copolymers or their mixtures with other non-conductive materials, or materials consisting of polycarbonate, are metallised .

8. Method of electrolytic metallisation of non-conductive surfaces, characterised by individual or all new features or combinations of disclosed features.