DE1950983A1 - Aqueous, alkaline bath for the chemical metallization of non-conductive materials - Google Patents

Description

Aqueous, alkaline bath for the chemical metallization of high-power conductor materials

The present invention relates to stable, at room temperature with a sufficient deposition rate, Electroless nickel and / or cobalt baths working in an alkaline medium to produce a Ni (Co) -P or Ni (Go) -B conductive layer on plastic surfaces.

In the current state of the art, the manufacture of a device is resistant to mechanical and thermal loads Sufficiently stable composite material, the metal layer of which is firmly connected to the plastic, is preferred possible on certain ABS graft polymers. It is well known that plastics do not conduct electricity; to be able to galvanize a plastic part, it is therefore necessary to make its surface conductive as soon as possible, i.e. with a metal layer, albeit a thin one to prove. The thin layer of metal that conducts electricity further galvanic layer structure made, the decorative plastic electroplating comprises 4 work steps;

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1) the roughening of the plastic surface;

2) activating the plastic surface j

3) chemical metallization, i.e. the production of a conductive material for electrical current, with the plastic surface firmly bonded metal layer;

4) the actual electroplating.

Metallization baths that work without external current are therefore required to produce the conductive layer. Here, the nickel conductive layers win over the copper-Ie it stratify more and more in importance. Yortell for the nickel conductive layers can be cited;

1) the high stability of the sealed baths as well as the relative high reduction yield

2) the increase in the throughput rate, due to the shorter dwell time in the electroless nickel bath, which means that the process can be carried out conveniently in the machine.

(Foreign) electroless nickel! Bathrooms _f containing the reducing agent sodium and for the production of a thin (about 1 / um), the electricity-conducting metal layer on art st off surfaces serve Bind known "These baths contain a winding salt, complexing agents, buffering agents , Stabilizers and, as a reducing agent, sodium hypophosphite. They work in the weakly acidic range (pH 4-5) at temperatures of 50-70 ^° C. Ni-P layers are deposited from these baths.

Electroless nickel baths for producing a conductive layer on plastic surfaces, which work with F-dialkylborasanem as a reducing agent, are also known. These baths also work at temperatures of 5 ° - 60 ° C in the weakly acidic pH range. In addition to a reducing agent, they also contain a gel salt, complexing agent,

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Buffer substances and stabilizers. Be separated Nickel-boron coatings. These coatings are air-resistant, storable, have good electrical conductivity and In contrast to the Ni-P layers, they can be further processed by electroplating directly in acidic bright copper baths.

The processes mentioned work on the so-called "drive through principle", which is known to allow acrylonitrile-butadiene-styrene plastics to be metallized without the plastic-coated frames on which the acrylonitrile-butadiene-styrene parts are attached accepting chemically deposited metal. The "drive through principle" differs from the conventional process - the SnClp / PdClp activation - through a new type of activation based on palladium salts, in which the objects to be metallized are treated with a palladium salt solution and then with a reducing agent. Chemical nickel plating, the reducing agent N-Methylborazan or N-Dimethylborazan included (German Patent 1,214,969) also work at lower temperatures than 5O ⁰ C, but these baths contain relatively large amounts of ammonia as a complexing agent and are therefore in practice because of the bad smell and their relative instability are not used.

The working temperature of the required in practice electroless Hickel baths of at least 50 ° C for the production of a Ni conductive layer on ABS plastics according to the The drive-through principle is a disadvantage of the baths previously introduced in technology (see Kunststoff-Rundschau 16, (1969), 8, 477/480).

The present application relates to aqueous, alkaline, Baths operating at ambient temperature for the chemical deposition of essentially nickel and / or cobalt

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existing coatings, which in a known manner Niekel- and / or cobalt salt, complexing agents, buffer substances, stabilizers and, as a reducing agent, sodium hypophosphite and / or contain hydrogen boride compounds, characterized in that the baths have a pH from about 7 to 10 and glycolic acid and / or lactic acid or their alkali and / or ammonium salts contain.

It has surprisingly been found that when glycolic acid or lactic acid is added to the commercially available electroless nickel baths which work in the weakly acidic range and which contain sodium hypophosphite or hydrogen boron compounds as reducing agents and the pH value is set to the alkaline range, stable, at ambient temperature - Approx. +15 ⁰ C to +45 ⁰ C with sufficient deposition rate working nickel and / or cobalt baths can be obtained. This is all the more surprising as it is known from German Patent Nos. 1,135,261 and 1,198,167 that glycolic acid or its water-soluble salts are known as complexing agents for acidic nickel baths operating at higher temperatures on the basis of sodium hypophosphite and hydrogen boride compounds. In this connection, the German patent specification 1,198,167 expressly refers to the stabilizing effect of glycolate. This statement is clearly contrary to the present invention, because when heated the baths of the invention to temperatures from 50 to 70 ⁰ O is already an uncontrollable Ni deposition (mirroring) to the container walls instead.

It is very surprising that in the presence of glycolic acid or lactic acid in the nickel plating bath, such a large one There is a difference between the alkaline and acidic areas of work.

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The process according to the invention is used to convert the known acidic nickel and / or cobalt baths to at ambient temperature operated baths to produce a conductive layer, preferably glycolic acid, and also lactic acid and the alkali and / or ammonium salts of these acids, are suitable. These are short chain oxycarboxylic acids the known baths in concentrations of 1-4 mol, preferably of 2 mol, per mol of M and / or Go salt added. The baths work in a pH range of 7-10, preferably at pH 8-8.5. Adjusting the pH value can be done with alkali hydroxide or ammonium hydroxide, where aqueous alkali metal hydroxide solution, preferably in the case of oi trathalt igen Baths is used. The stabilizers known for hypophosphite and borohydride baths are used for stabilization such as lead, tellurium, zinc ions, which are described in the US patent 2,762,723 listed 3-containing compounds or the stabilizers known from British patent specification 945 018 suitable. The reducing agents used are preferably sodium hypophosphite or boron-hydrogen compounds such as N-dimethylborazane or N-diethy! borazan is used.

Not only the electroless nickel-plating baths available on the market, but also betx'ebene known from the literature According to the method according to the invention, baths can be operated at ambient temperature.

It can, for example, the method described in electroplating J58, 1967, no. 10, page 721, designated by the trade name "Metalyt D", which is suitable for metallization of ABS plastic surfaces and works normally at 6O ⁰ G, operated at normal femperatur be added to the nickel-plating bath glycolic or lactic acid and further the pH of the bath to a weak

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alkaline value, preferably to a pH of 8-9, is adjusted. In the same way can not only powered by hypophosphite, but also with borazane Switch the baths to a working method at fifbrmal temperature.

An advantage of the method according to the invention is that the deposited Mi-B or fflfi-P conductive layers have better conductivity than the conductive layers deposited from commercial baths with the same dwell time in the (externally) electroless nickel plating bath. It has been found that the lower P or B content of the conductive layer is irrelevant for this phenomenon. A conductive layer deposited from a borazane bath contains approx. 3 $> boron, while conductive layers with boron contents below 1 $ were obtained from the baths used according to the invention. In the case of the deposited Ni-B-Iisite layers, it is particularly noteworthy that the galvanic reinforcement of the conductive layer recommended by the corresponding electroplating specialist companies is no longer necessary. With well-distributed contacts in the subsequent galvanic copper or nickel bath, you can start up with the corresponding current density, without having to worry about burning points and thus interrupting the current at the contact points.

Another major advantage of the invention Process is that the consumption of reducing agent in the Vemiekelungsbäder working at low temperature can be reduced significantly. This is siaamal due to the fact that almost a pure nickel class aait low boron or phosphorus content and deposited on the other hand, there is the undesirable skin reaction caused by hydrolysis For example, the borohydride is strongly reduced by the lowering of the temperature and the pH value recovery rank.

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In the baths according to the invention, the drive-through principle is used. In contrast to the at 50-70 ⁰ C working acidic electroless Vernickelungs baths was found need to be that the palladium salt-containing activator solution is not heated. All baths with the exception of the pickling bath therefore work at room temperature; as a result, the method according to the invention has a considerable economic advantage over the known method. The adhesive strength of the galvanic coatings is not impaired. Furthermore, all tested, decoratively processed ABS plastic parts have passed the cold / heat test over three cycles without errors (+80 ⁰ O and -30 ° G _t see Galvanotechnik £ 8, 1968, No. 3, p. 228 - 229),

The cold-working electroless can also be used to manufacture printed circuits using the additive process Metal baths can be used. This metallization process can be carried out entirely at room temperature, because in the production of printed circuits with Nibodur, the roughening solution is already at room temperature works (see Transactions of the Institute of Metal Finishing 1968, VoI, 46, pp. 194-198).

The following examples are intended to explain the process according to the invention in more detail:

example 1

Circular discs (d = 10 cm) made of an ABS graft polymer (trade name: Novodur P 20 M) were attached to a provided with contact points for conducting current carefully insulated frame of copper and stained initially in a chrome-sulfuric acid pickling bath 5 minutes at 60 ⁰ C. .

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It was then immersed in 18 # hydrochloric acid to remove chromium (VI) compounds and rinsed well. For activation, the Proben3 were warm minutes in a Sun ⁰ C, aqueous palladium chloride solution of concentration 100 mg PdClg / IIId, with H ₂ SO. had been adjusted to a pH of 2.2, immersed, then rinsed briefly in cold water and then immersed for 1 minute in an aqueous reducing agent solution at room temperature with a content of 500 mg / liter N-diethylborazane. For metallization, the samples were then immersed in a nickel salt-Z-borohydride bath at 28-35 ° C. for 5 minutes. The bath containing 30 g / liter NiCl ₂ . 6 H ₂ O, 20 g / liter sodium succinate, 20 g / liter sodium acetate and 3 ml / liter N-diethylborazane as well as 50 ml / liter alcohol, 40 g / liter glycolic acid, 65% and 45 ml 25% , aqueous ammonia solution added. The pH of the bath was 8.5. The electrolessly deposited nickel conductive layer contained less than 1% boron. The chemically deposited nickel layer had good electrical conductivity and could, for example, be further processed directly by electroplating in acidic zinc copper baths. When the experiment was repeated, the activation with palladium chloride solution was carried out at room temperature, ie at 20 ^° C. The adhesion test, which was carried out on the basis of DIN 40 805 (peel test), showed no difference between cold and warm activated ABS plastics in the bath composition given above.

Example 2

Plastic parts made of ABS graft polymer were manufactured according to the in Example 1 described pretreatment in the baths listed in the table with the specified residence times and

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Temperatures were then chemically metallized the parts rinsed in water, pickled in 10 # sulfuric acid and after rinsing in a bright copper bath galvanically copper-plated at 4 amperes / dm. It became copper applied with a layer thickness of 10 μm. After copper plating, the parts were rinsed in running water, Pickled in 10% sulfuric acid, rinsed again in running water and known in a semi-gloss nickel bath Composition at 5 Ampdre / dm with a layer thickness of 10 / um nickel-plated. Then it was in a high-gloss nickel bath 5 / um bright nickel at one current strength

2
applied from 5 amperes / dm. A number of parts were chrome-plated with a layer thickness of approx. 0.3 μm. The decoratively machined parts were stored in the air for 48 hours and subjected to a temperature change test. The thermal shock test consisted of heating the parts in a drying cabinet at +80 ⁰ G over a period of 105 minutes an intermediate storage for 15 minutes at room temperature and cooling to -30 0 over a period of 105 minutes. This temperature change was carried out three times. The parts showed no change, in particular no settling of the deposited metal layers.

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Bath no, bath composition 1 2 34 56 78 9 10

* "Nickel Chloride *» Nickel Sulphate ui cobalt chloride cobalt sulfate Sodium citrate Sodium acetate glycoic acid (65% Lactic acid sodium hyd rox i d,

20% aqueous solution

Ammonium hydroxide 25% aqueous solution O Wetting agent Genapol X / 080 I

Sodium hypophosph11

Q N-diethy I borazan C ₀ isopropanol ⁰ ^ N-dimethyI borazan -j pH value ^ temperature -J dwell time

30th 9/1 5 30th 9/1 5 30th 9/1 ¹ mg - - - - 15 g / l 15 g / l - 5 g / l - - - ° c - ⁰ C - 30 g / l - - 30 g / l - - 10 g / l - - min - min 9/1
/ I - 30 g / l 30 g / l - 15 g / l 15 g / l - - - - - - - - - - - - 10 g / l 15th 9 /! 15th 9/1 15th 9/1 5 15 g / l 15 g / l - 15 g / l - - 20 g / l - 5 9/1 5 9/1 5 9/1 I ⁰ C 5 g / l 5 g / l 15 g / l 40 g / l 20 g / l 30 g / l - 20 g / l 40 9/1 40 9/1 40 9/1 min 40 g / l 40 g / l 40 g / l - 40 g / l - 30 g / l 15 g / l - - - - - - - - 40 g / l - - I. - 65 ml / l - - - - 35ml / I - - 22ml / I I. 45 ml / l - 45ml / I 45ml / l 35ml / I 35ml / I 50 mg 30ml / l 33ml / I 50 mg • 50 mg 50 mg 50 50 mg 50 mg 50 mg - 50 mg 50 mg - 50 mg 10 9/1 10 9/1 - - - - 4 g / l
50ml / l - - 3 g / l
50ml / l - 3
50ml - 3 9/1
50ml / l - 4 g / l
50ml / l - - 3 g / l
50ml / l - - - 3 g / l - 3 g / l 8.5 - 3 g / l 8.0, - 8th, 8th, 8th, 8.5 8.5 8.5 30 ⁰ C 8.0 8.0 27 ⁰ C 8.5 30th 30th 3C 3O ⁰ C 3O ⁰ C 25 ° C 8 min 25 ⁰ C 25 ° C 5 min 28 ° C "£ 6th 6th 5 5 min 5 min 5 min 5 min 5 min 5 min C * ¹
O
CD
CXJ
Ca)

Claims (3)

Claims 1. Aqueous, alkaline baths operating at ambient temperature for the chemical deposition of essentially Nickel and / or cobalt existing coatings, which in a known manner nickel and / or cobalt salt, complexing agents, Buffer substances, stabilizers and, as reducing agents, sodium hypophosphite and / or hydrogen boron compounds contain, characterized in that the baths have a pH of about 7 to 10 and glycolic acid and / or Contain lactic acid or its alkali and / or ammonium salts. 2. Baths according to claim 1, characterized in that the molar ratio of glycolic acid or lactic acid to Nickel or cobalt salt is approximately 1: 1 to 4: 1, preferably 2: 1. 3. Baths according to any one of claims 1 or 2, characterized in that the pH is about 8.0 bie 8.5. Le A 12 558 10 9 817/1736