NL8302344A - METHOD FOR ELECTRICAL COATING OF NON-METALLIC SURFACES. - Google Patents

Description

r * S 5229-7 Ned * P & c

Short designation: Method for electrically coating non-metallic surfaces.

The present invention relates to the metallization of non-conductors. It also relates to the manufacture of printed circuit board plates with metallized wall openings, hereinafter referred to herein as printed circuit board plates with coated bore holes.

In particular, the invention relates to methods of electrically coating insulating surfaces and to the composition of the coating solutions used for this purpose. Non-metallic surfaces are usually metallized by first making the affected surface catalytically susceptible to non-electrically formed metal deposits and then exposing the surface so catalyzed to a bath of a coating solution of the kind which does not have an external source of electricity and this for sufficient time to form a metal layer, for example of copper or nickel, with the desired thickness. This first layer is usually provided with further metal deposits, which are formed by conventional electrical coating methods. According to known methods for the manufacture of printed circuit boards with coated boreholes, this principle of metallization and variations thereof is used to metallize the walls of the openings. In the variation, which is based on a two-sided copper-clad laminate as a base material, a panel of a suitable size is first provided with the required bores, after which the walls of the openings are catalytically susceptible by immersion in a known catalyst solution. Then, a metal deposit, usually of copper, is formed by exposure to a bath with a solution, which gives metal deposits without an external source of electricity, commonly known as non-electrical plating baths, for a sufficient time to a thickness of, for example, 0.5 to 2 , 5 firn.

This first conductive metal layer is further coated using conventional electrical coating methods.

The representative catalyst solutions used in the above-described method have been used in this industry for many years and have developed to a relatively high degree of stability.

Surfaces that have been catalytically treated with such solutions promote the formation of non-electrically formed metal deposits by oxidation of suitable components present in the non-electric coating bath, this mechanism acting as an internal source of electrons which should be used in the coating reaction to reduce metal ions from complexes to metal.

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Operating non-electrical metal coating solutions requires relatively careful monitoring of the various components and replenishment of spent materials by controlled chemical feed. Furthermore, these coating solutions tend to deposit relatively arbitrarily, thereby forming metal - for example, copper deposits - on the walls and bottom of vessels used to operate such coating baths. This requires frequent interruption of the coating operation, removal of the coating solution from the vessel and cleaning of the walls and bottom of the vessel by an etching operation.

Non-electrical metal plating is therefore relatively expensive and complex and requires well-trained operators.

Despite these significant shortcomings, non-electrical deposition of a first metal layer has hitherto been an integral part of all processes used for metallizing non-metal. odd surfaces, including such processes, used in the manufacture of printed circuit boards.

U.S. Pat. No. 3,099,608 discloses the use of a palladium tin chloride colloid to form a substantially non-conductive form of colloidal or semicolloidal particles on the walls of an aperture provided for the manufacture of plates for printed wiring used laminate; and for electroplating to copper-core the walls of the bores.

However, the method of U.S. Pat. No. 3,099,608 has serious drawbacks and has proved unsuitable for practical application.

The colloidal suspension of palladium tin chloride has an unacceptably short life. It can only be used for approx. 9 days due to the coalugation of the suspension and it is also quite expensive due to its high palladium content. Furthermore, in the method of U.S. Pat. No. 3,099,608, significantly more copper is deposited on the surface than on the walls of punctures, and therefore this method is unacceptable for commercial use.

United States Patent 3,099,608 is based on the use of a "thin, barely visible particle film" of "semicolloidal palladium" deposited on the surface to be coated, which film has "considerable resistance", and on the proposition "that since it palladium is naturally both a catalytic metal and a conductive metal, it has the potential to perform simultaneously and combined activating and conducting functions "(column 4, lines 53-56) and further that" after the 40 electrical coating operation has started at a conductor, which is apparently activated by the catalytic properties of the palladium and the electrical deposition process advances directly on the film of conductor particles "(column 4, lines 62-66). In column 5, lines 2-7, it is stated that "since the deposition of collodial palladium in the bores 5 was an extremely poor conductor to serve as a basis for the electrical plating operation, compared to the deposited graphite, something otherwise, promote electrical deposition, ie a catalyst must have assisted in the coating reaction ". Despite the fact that the inventor's remark dates from 1959 and therefore dates from the same time as the use of graphite for the metallization of non-conductors and the first application for the "non-electrical coating technology with inoculum" for the metallization of plastic parts and for the production of coated puncture plates (PTH), this did not lead to a method of any practical use. Considering the significant initial difficulties with the graft non-electrical coating technology and its development, and further the properties of continued complexity of operating, controlling and maintaining a non-electrical plating bath compared to the relatively simple electrical plating process In fact, it is particularly surprising that the observations of the inventors of U.S. Pat. No. 3,099,608 had no effect, as far as the technological development of the latter two deeds is concerned. The reason is that these observations do not lead to a teaching that the average expert can use. In the absence of this teaching, the inventors' observations could only be duplicated using their "conductor solution" and the copper pyrophosphate electrical coating bath that existed at the time.

It is believed that the inventors of U.S. Pat. No. 3,099,608 have not recognized the importance of the composition of the copper electrical coating bath. For example, among the prior art pyrophosphate electrical coating baths in use at the time of the filing of the U.S. patent, the simplest did not provide copper of sufficient quality for printed circuit boards; the more complex bath type gave a sufficient quality of the copper, but inhibited the action of the process suggested in U.S. Pat. No. 3,099,608. Therefore, the industry found the observations made by the inventors and described in U.S. Pat. No. 3,099,608 to be of no practical significance. The "grafting non-electrical copper plating", whether or not followed by electrical plating, was therefore accepted as 8302344

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1 - 4 - the only technically available approach for metalizing non-metallic surfaces.

Thus, U.S. Pat. No. 3,099,608 gives a teaching which leads away from the present invention. To arrive at the present invention, the misunderstanding given by the inventors of U.S. Pat. No. 3,099,608 that the properties of the electrical coating baths were not critical had to be overcome and completely discarded.

According to the present invention, there is disclosed a method for metallizing non-metallic surfaces by electrically coating in a counter-electrode vessel containing an electric coating solution bath, which in ionic form is electrically coatable metal (B), which surfaces are provided with a connection part, which. is located outside the area of the non-metallic, electrically coated surface, which method is characterized? forming (a) a number of metallic sites on these surfaces, which sites contain or consist of a metal (A), the metal (A) being different from the metal (B) to be deposited on the surfaces by electrocoating; and (b) the surfaces, under which at least part of the interface surface is exposed to the solution of the electrical coating bath, which solution has a certain conductivity and further contains one or more components (C), which has preferential deposition of metal (B ) on the metal (A) containing or consisting of metal sites as compared to deposition on surfaces consisting of or formed by the electrically deposited metal type (B); and (c) applies a potential to the terminal surface and the counter electrode sufficient to initiate preferential deposition of metal (B) at the sites containing or consisting of metal (A) for a sufficient time to be substantially uniform. deposition of desired thickness.

In one embodiment, the deposition rate on the metal sites is at least one order of magnitude and preferably two orders of magnitude higher than the deposition rate on the deposited metal.

In another embodiment, the metallic sites (A) 35 and the electrically deposited metal (B) are formed by metals selected from groups 1b or VIII of the Periodic Table of Elements, provided they are not equal.

In yet another embodiment, the above-mentioned component (C) is selected from dyes, surfactants, chelating agents, 8302344 9-5 brighteners or leveling agents.

In yet another embodiment, the metal-plated substrate is exposed to one or more of the following treatments: heat treatment, treatment with a cleansing conditioner and / or treatment with a reducing agent.

The method of the present invention is an improved method of coating non-metallic surfaces on the substrate. More specifically, it is an extremely effective method for coating walls of bores in metal clad laminates.

Ijrardt 10 A particular advantage obtained according to the invention in the manufacture of printed circuit boards with coated bore holes is the integrity of the copper wall of the opening. Since the copper is applied electrically to the substrate of the non-metallic wall of the piercing without a non-electrically formed metal interlayer, the physical properties and adhesion at the interface of copper and plastic, in addition to the adhesion between copper foil and the electrically applied metal, for example the copper deposit, is greatly improved. This is of particular importance in the manufacture of highly reliable printed wiring, such as multi-layers.

In practice, the method of the invention for electrically coating non-metallic surfaces on the substrate comprises the steps of forming separate metallic sites on the surface to be coated, the metallic sites being of a different metal than the electrical metal to be applied, a bonding surface on the substrate provides outside the electrically non-metallic surface to be coated, the surface to be coated and contacts at least a portion of the bonding surface with a solution of an electrical coating bath, which is suitable for coating contains metal of the type to be electrically deposited and a component which allows preferential deposition of the metal to be deposited in the metallic locations over metal deposited from the electrical plating bath, provides a vessel containing the bath of the electrical coating solution with a counter electrode, and a sufficient potential difference.-. between the electrodes 35 formed by the terminal surface and the counter electrode for a sufficient time to initiate and cause preferential deposition on the surface provided with said locations to form a deposit of desired, substantially uniform thickness.

Although the invention is not limited by theoretical considerations, 8302344

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Applicant assumes that the direct electrical coating process described here is based on the following principles: I. (1) Metallic locations applied to non-metallic surfaces are provided with a "bonding surface" (bonding-5 electrode ), which is also applied to the surface, connected by the electrolyte. of the coating bath, which forms a "resistance bath" between the connection surface and the neighboring places; corresponding paths are formed between the involved places.

The higher the density of the metallic places, the faster the uniform metal layer is formed by electrical deposition.

(2) The higher the conductivity time of the electrolyte, the lower the resistance of the "resistance path"; with a theoretical electrolyte of infinite conductivity, all sites would have the same potential as the terminal surface. Conversely, in a theoretical electrolyte with very low conductivity, the resistance between the metallic sites and the bonding surface would be too high for all practical purposes to develop a potential for coating these sites.

20 (3) With practical electrolytes, a voltage drop develops across the resistance path. Thus, based on the above, one can say, (a) the potential difference applied by the voltage source to the counter electrode and the terminal surface should be chosen so that it is not only the voltage drop between the electrodes, including the overvoltage for the deposition compensates for, but also the voltage drop across the resistance path formed by the electrolyte, so that an adequate coating potential is provided at the metal sites; (B) the higher the electrical conductivity, the faster the coating reaction proceeds in these places (and also the more uniform is the thickness); (c) the conductivity of the electrolyte should be chosen as high as is acceptable in terms of the coating operation parameters.

(4) Component (C), which is present in the electrical coating path, causes the formation of an initial electrical deposit, which preferentially grows laterally along the metal-plated surface, as opposed to the vertical 8302344 j * - 7 - growth on the surface of the metal deposited from the coating solution.

The term "conductivity" as used herein is defined as a function of the concentration of the current-conducting material, i.e.

In an acid bath it is believed that the hydrogen ions act as the main current-conducting material.

II. (1) For all practical purposes, it is necessary that the deposit formed by electrical coating is substantially uniform and that its thickness is not substantially a function of the distance from the connection surface. In the case of printed circuit board plates with metallized wall borings, the deposits on the surface and those on the walls of the openings should not exhibit a significantly inadmissible thickness difference.

(2) The problems of non-uniformity also exist for electrical deposition in general. To overcome this, certain additives are used in the coating solution bath, which are known, for example, as leveling agents.

(3) Electric coating baths with pyrophosphate containing such additives give satisfactory results when used in the standard "non-electric coating with grafting" process.

(4) Additive-type copper pyrophosphate baths which were available at the time rendered the method proposed in U.S. Pat. No. 3,099,608 ineffective. The reason for this is that the commonly used additives adhere to the metal of the type to be deposited (copper) as well as to the palladium of the metallic sites or even preferentially adhere to the latter and thus the coating process at those sites. disturb or obstruct. In light of U.S. Pat. No. 3,099,608, it is surprising that the Applicant has obtained satisfactory results in both uniform thickness and superior quality of the metal deposition by using bath compositions containing one or more components which preferentially adhere to the metal type to be deposited and thereby reduce the coating action on those surfaces as compared to the coating action on the metallic sites of another suitable metal, for example palladium, although they preferentially adhere to the metal of the metallic sites bonding and coating action at those locations 3302344

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- 8 - increase compared to the surface area of the metal type coated.

The above-described problems in using the grafting non-electrical coating process, in addition to the inactive method described in U.S. Patent 3,099,608, are completely overcome by the present invention.

As is apparent from the theoretical mechanism above, the applied potential must be sufficient to electrically deposit the metal to be deposited at the individual sites at a rate greater than that on the deposited metal. In practice, this potential is determined by known and accepted electrochemical methods.

One of these methods includes measurements of the relationships between amperage and potential for electrically depositing a metal on different substrates in the absence and in the presence of component (C). In the potential range applicable to standard electrical plating solutions (for example, for a plating solution with copper sulfate and sulfuric acid about 0 to -200 mV versus a saturated calomel electrode and for a plating solution with copper pyrophosphate about -300 to - 1000 mV against a saturated calomel electrode), the coating speed on various substrates provided with metallic sites appears to be higher when the coating solution contains component (C), compared to the coating speed on other substrates with surfaces of the metal, which must be deposited.

Adsorbent components (component (C)) of the electrical coating solution can be selected on the basis of the current density proton curves obtained with an electrode made of the electrically deposited metal, for example copper, and with an electrode made of the metal used to form the metallic places (e.g. palladium). Amperage potential curves 30 are recorded using the triple electrode system comprising the test electrode, the counter electrode and the reference electrode. Electrode polarization can be performed by applying a linearly-changing potential and recording the current (voltametric method) or by applying a constant current and drawing the potential at 35 (galvanostatic method). A description of the three-. electrode system and the voltametric and galvanostatic methods are given in "Modern Electrochemistry" by J. O'M. Bockris and A.K.N.Reddy, published by Plenum Publ. Corp., New York, NY, 1970, pages 891-893 and 1019-1026.

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A rapid method of selecting the bath composition for the method of the present invention uses current-potential curves to determine the difference delta (E) ^, which is defined by delta (E) ^ = E - E ', where E and E "potentials at the current density i are respectively of the metal of the electrically deposited metal and the electrode of the metal used to form the metallic sites (see FIG. 1). The current density i lies in the range from 30 to 50% of the peak current density

i (figure 1). At the current density selected in this way, the P

The electrode, which is made of the metal used to form the metallic places, is not covered to a significant degree by the coating metal at the potential E 2. In the galvanostatic method, the density of the radiation i is also chosen in such a way that there is no significant coverage of the electrode made of the metal used to form the metallic sites with the coating metal.

The method of selecting the adsorptive components consists of the following steps: (1) Current-potential (iv) curves are recorded for both types of test electrodes, ie of the metal for the electrical deposition (eg copper) and the metal (palladium) used to form the metallic places; (2) A current density i is selected in the range of 30 to 50% of the peak current density; (3) The potentials A E "^ for the selected current density are read from the current potential curves (i-v); (4) The difference between the potentials dela (E) E1E" ^; (5) Adsorptive components which cause a high delta (E) value, being preferred components, i.e. a high value difference delta (E) bath is a preferred bath.

The same method and the same criterion are used to choose the preferred concentration of the adsorptive components. Another fast method for choosing the bath composition for the method according to the invention also applies current-potential curves, but in that case the function delta (E) is determined, this function being defined as delta (E), = E '. . - E ", where E 'and E" are the deposition dep dep dep dep dep potentials (ie, the potentials extrapolated to zero current from the current potential curves) for the metal to be deposited on it from the electrical to be deposited metal fabricated substrate for the metal 40 used to form the metallic sites (Figure 2).

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The experimental method is the same for this technique as for the previously described method. E 'and E ", however, are calculated by dep dep extrapolating the current-potential curves to current zero and then reading the values for E and E" ^ ep. In this method, a bath-composition having a high delta ( E) value a preferred bath composition. Concentrations of adsorptive components, which cause a high delta (Ε) ββρ value, are the preferred concentrations for these components. All of these rapid methods of selecting the constant flow coating bath composition can be modified for use in other metal coating methods, such as pulsed coating, fast galvanostatic or potentiostatic coating. In addition to the above-described rapid methods of selecting the bath composition for the method of the invention, other methods may also be used (described in "Modern Electrochemistry," p. 1017 ff.).

Therefore, any component that causes the coating speed on the metal sites to be higher than on the metal to be coated, as described above, is covered by the invention.

According to an embodiment of the present invention, the component (C) causes preferential deposition by preferentially adhering to a surface of the metal type (B) compared to the surface of the metal type (A), thus causing the coating reaction on metal (B) formed surfaces are significantly inhibited or reduced without significantly interfering with the coating reaction on surfaces formed by the on-site metal type (A).

According to another embodiment, component (C) preferentially adheres to the metal type (A) present at said locations, the bonded component (C) reducing the span and thus accelerating the coating reaction compared to the reaction on metal type surfaces ( B).

According to a preferred embodiment of the invention, the conductivity of the electrical coating solution in the bath and the voltage applied to the connection surface and the counter-electrode are chosen sufficiently high to achieve a deposition rate on the surface of the metal type (A) sites, which is at least one order ί and preferably two orders of magnitude higher than the deposition rate on the surface of the metal type (B). It has been found that the maximum conductivity suitable for the process of the invention for all practical purposes is as high as allowable over the other coating operation parameters.

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It has also been found that the voltage applied to the electrodes should be chosen so that it condenses the voltage drop across the resistive bath formed by the plating solution from the bath between the starting surface and the metal sites containing the metal (A) or 5 therefrom exist and between such neighboring places.

In addition, it is preferable that this potential be selected at the highest allowable value relative to the other coating parameters.

Metal (A) in addition to metal (B) may be selected from groups 10 lb or VIII of the Periodic Table of Elements, provided they are different.

Preferably, the metals (A) and (B) are selected such that metal (A) has a lower coating potential than metal (B) under the conditions provided by the coating operation.

The metal (A) is preferably selected from palladium, platinum, silver and gold, with palladium being most preferred.

Metal (B) is preferably selected from copper and nickel.

The preferred solutions for the electrical coating bath are acidic.

Component (C) can be selected from dyes, surfactants, gelling agents, brighteners and leveling agents which preferentially adhere to surfaces containing or consisting of metal (B) and act by reducing or inhibiting the coating reaction and / or depolarizing agents which preferentially adhere to metal (A) surfaces and the coating reaction enhances that surface.

Suitable dyes are, for example, those selected from Victoria Pure Blue F80, methylene blue, methyl violet, acid blue 161, alcian blue 8GK and other N-heterocyclic compounds, triphenylmethane type dyes and aromatic amines, imines and diazo compounds, including of amines, imines and diazo compounds with fused ring system. Suitable surfactants include non-ionic surfactants such as alkylphenoxy polyethoxyethanols, eg octylphenoxy polyethoxyethanol and fluorocarbon type nonionic surfactants such as Zonyl FSN (registered trademark).

Among the many surfactants, including wetting agents and water-soluble organic compounds, which have been proposed for use in electrical coating solutions, are surfactants and polymers containing polyoxyethylene groups. Compounds 8302344 - * - 12 - which on the one hand contain only four and on the other hand themselves a million oxyethylene groups, have been found to be effective. A preferred group of these compounds comprises oxyethylene polymers having only twenty on the one hand and even one hundred and fifty oxyethylene groups on the other. Preference is also given to block copolymers of polyoxyethylene and polyoxypropylene. Among these preferred block polymers are those containing 7-250 oxyethylene groups. In general, it has been found that when these polyoxyethylene compounds are added to a solution of an electric coating bath, in particular an acid solution of an electric coating bath, the growth of the electrically deposited metal (B) on the non-conductor surfaces, which are provided with the metallic places (A) strongly increase. Most often, these polyoxyethylene compounds are used in the solutions of the electrical coating bath at a concentration of 0.1 to 1.0 g / l. The optimal concentration depends on the composition of the electric coating bath solution and on the selected polyoxyethylene compound. In some cases, an amount of less than 0.1 g / l or more than 1.0 g / l may be preferred.

Examples of representative gelling agents are riboflavin, 2.4.6- (2-pyridyl) s-triazine and the pyrophosphate anion.

N-heterocyclic compounds, triphenylmethane dyes, thiourea and thiourea derivatives may be mentioned as suitable brighteners and leveling agents. Among the suitable thiourea derivatives to be used are tetramethylthiuram disulfate and allyl thiourea. Suitable examples of commercial products are Electro-Brite PC-667 (registered trademark) and Copper Gleam PC (registered trademark). Other suitable additives include saccharin and derivatives of o-benzaldehyde-sulfonic acid, which are particularly suitable in solutions for a Watt nickel plating bath.

According to the preferred embodiment of the invention, metal sites are formed by treating the surface concerned with a solution containing the metal (A) as a compound or complex, for example, as a metal halide, such as palladium tin chloride, a double metal halide.

In forming metallic locations of the metal (A), it has been found advantageous to expose the surface to a reducing agent after treatment with this solution.

In the case where the compound used to form the sites contains tin, it has further been found to be advantageous to remove the tin compound from the surface provided with the desired sites. This will be 8302344 * f

Ut · - 13 - carried out with a tin-removing solvent, for example a dilute aqueous solution of fluoroboric acid or strongly basic solutions, which allow the formation of soluble alkali metal stannites.

In order to achieve an improved storage life for the surfaces provided with said locations, it has proved advantageous to subject the surface treated with the metal-providing solution to a heat treatment, for example at a temperature of 65 to 120 ° C. for 10 minutes or more. It has been found that surfaces treated in this way can be stored for a long time, for example 9 months, without detriment, immediately after removal from the inserting solution. After prolonged storage, it is advantageous to expose the provided surface to an acidic solution, for example, to one molar sulfuric acid for 15-20 minutes.

Suitable reducing agents as mentioned above can be selected from sodium borohydride, formaldehyde, dimethylamine borane or hydroxylamine.

It has also been found to be advantageous to pre-treat the non-metallic surface before entering the metallic sites by exposing it to a cleaning and conditioning agent, for example an aqueous solution, containing a mixture of nonionic and cationic wetting agents. contains. Such cleaning and conditioning agents are widely used in the field of printed wiring and plastics coating.

Figure 1 is a graphical representation showing the current-voltage relationship that determines the difference delta (E). = E '.- Ë ".

1 11 25 Figure 2 is a graphical representation showing the current-voltage relationship, which determines the difference delta (E), = E * - E ".

dep dep dep

Figure 3 is a series of photos showing, in chronological order, an electrical deposit produced by the method of the invention.

Figures 1 and 2 have already been explained in more detail above.

Figure 3 is a series of photos (a) to (f) taken at different times after the start of an electrical deposition carried out in accordance with the present invention.

Figure 3a is a photograph taken after 1 minute of deposition in a solution of an electrical coating bath used in the method of the invention. The substrate is a copper clad laminate, which is provided with palladium metal spots on the walls of the bores. The metal that is deposited is copper.

Figure 3b is a photo of the same substrate taken after 2 minutes of 8302344 -14- + * electrical deposition.

Figure 3c is a photo of the same substrate taken after 3 minutes of electrical deposition.

Figure 3d is a photo of the same substrate taken after 4 minutes of electrical deposition.

Figure 3e is a photo of the same substrate, taken after 5 minutes of electrical deposition.

Figure 3f is a photo of the same substrate taken after 20 minutes of electrical deposition.

As indicated by way of example with this series of photographs, the metal deposit formed on the surface of the wall of the bore is uniform and continuous.

EXAMPLE I

This example describes metallization of the walls of apertures drilled in panels cut from sheets of copper-faced insulating base material on both sides of the type used in the manufacture of printed circuit boards. They have a thickness of 1.6 mm and they are known as FR-4 epoxy glass material.

The apertured panels were treated with a solution containing a cationic surfactant, a nonionic surfactant and an alkanolamine and adjusted to a pH below 4, thereby cleaning the surfaces of the aperture walls and were conditioned for the following beta steps.

The panels were then immersed in a 1% aqueous sulfuric acid solution for 5 minutes, rinsed with water, treated with sodium persulfate solution (120 g / l with a pH below 2) for 45 seconds at 40 ° C to obtain the copper surface. deoxidize and rinse again with water.

The panels were then treated for 5 minutes in a solution containing 5 g / l stannous chloride, 225 g / l sodium chloride and enough hydrochloric acid to obtain a pH below 0.5. After this step, the panels were exposed to a palladium tin chloride solution at 55 ° C for 5 minutes with continuous agitation. The palladium tin chloride solution was formulated as described in Example III of Dutch patent 165 790 and diluted to a palladium concentration of 210 mg / l by mixing with an aqueous solution containing 3.5 mole sodium chloride and 0.08 mole stannous chloride. After dipping in this palladium tin chloride solution, the panels were rinsed with water, heat-treated in an oven at 100 ° C for 60 minutes, and then brushed off.

Before the electrical coating, the copper surfaces were deoxidized 8302344-15 by dipping for 5 seconds in a solution of sodium persulfate. Some of the panels thus prepared were electrically coated in a coating solution containing 0.3 moles of copper sulfate, 1.8 moles of sulfuric acid and 1.3 nmoles of 2 hydrochloric acid. The current density was 3.5 A / dm.

After 5 minutes of electrical coating, only 10% of the entire wall was covered. After one hour of electrical coating, the panels were removed and the openings examined. Copper was formed partially downwardly along the walls of the opening, leaving a large area around the center of the center surface of the wall of the opening free of copper.

A second series of the panels so prepared were electrically coated after 5 g / l of nonionic surfactant, octylphenoxy polyethyl ethanol, was added to the copper electric coating solution. After less than 5 minutes of coating, the walls of the opening were found to be completely covered with a continuous cavity-free copper metal film.

EXAMPLE II

Further panels prepared according to the method of Example 4 were electrically coated in a copper plating solution, which was the same as in Example 1, except that it contained 5 g / l methyl violet instead of the nonionic surfactant used in Example I and that the coating potential was set according to the invention. After 5 minutes of electrical coating, the walls of the openings were covered with a full continuous film of copper-25 metal.

EXAMPLE III

The procedure of Example II was repeated, except that the methyl violet was replaced with methylene blue. Again after 5 minutes of electrical coating, the walls of the openings were covered with a full continuous copper film.

EXAMPLE IV

The procedure of Example I was repeated, except that the copper electrical plating bath was replaced with a Watts nickel electrical plating bath solution. The Watts nickel bath 35 consisted of 300 g / l nickel sulfate, 30 g / l nickel chloride and 30 g / l boric acid.

Even after prolonged coating times, only an incomplete coating was observed on the walls of the openings. Saccharin was added to the Watt nickel bath and another panel was subjected to the coating operation. A complete continuous film of electrically deposited nickel quickly covered the walls 40 of the openings.

3302344

- 16 - EXAMPLE V

The procedure of Example IV was repeated, except that the Watts nickel bath contained 20 ml / l Lectro-Nic 10-03 (registered trademark), a compound containing an o-benzaldehyde sulfonic acid. A complete continuous film of electrically deposited nickel on the walls of the openings was obtained.

EXAMPLE VI

The procedure of Example IV was repeated, except that Copper Gleam PC (registered trademark), a material used as a brightener for copper sulfate / sulfuric acid electrical coating baths, comprising a triphenylmethane dye, was added to the Watts nickel bath. v was added. A complete continuous film of electrically deposited nickel is obtained on the walls of the openings.

EXAMPLE VII

This example describes the manufacture of a printed circuit board using the metallization methods of the invention.

Copper-clad ER-4 or CEM-3 grade insulating plates of printed circuit base materials were cut into appropriately sized panels, the holes required for the through-bore connections were drilled, and the copper surfaces of the panels were freed from appendages. Thereafter, the panels were successively treated as in Example 1 in a cleaning and conditioning solution, a sulfuric acid solution, a rinsing solution, a sodium persulfate solution, another rinsing solution, a SnCl 2 and NaCl-containing solution, and a palladium tin chloride solution. The panels were then rinsed, heat-treated at 120 ° C in an oven for 20 minutes and brushed off. The panels thus treated can be stored in this state or processed immediately without interrupting the process.

For further processing, the panels were provided with a resistance mask for the coating, which was formed according to known photographic printing processes, screen printing processes or other suitable processes and thereafter for. 45 seconds in a commercial alkaline cleaning solution subjected to a 2 reverse current electric cleaning process at 3 A / dm, rinsed and treated for 5 seconds with sodium persulfate (as described above) and rinsed again.

Then, the panels were electrically coated for 5 minutes at a potential, 2 giving a current density of about 3 A / dm using a bath containing the following materials.

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Copper sulfate 75 g / 1

Sulfuric acid 190 g / 1

Chloride ion 70 ppm

Electro-Brite (registered trademark) (PC-567) 5 ml / 1

The resulting panels were rinsed and further electrically coated with copper in a bath for 2 minutes at 3 A / dm

Copper sulfate 75 g / 1

Sulfuric acid 190 g / 1 Λ Chloride ion 50 ppm 10

Copper Gleam PC (registered trademark) 5 ml / 1

In other tests, the panels were not electrically coated according to the above 2 coating steps, but in one operation for 2 about 45 minutes at 3 A / dm in the bath with the first electric coating solution described above. Thereafter, the panels were rinsed and printed circuit boards according to the known steps of 2 solder coating at 2 A / dm for 18 minutes, rinsing, removal of the resistance mask, etching with ammonia copper chloride solution, solder melting, applying a solder mask and cutting the wiring board to size.

EXAMPLE VIII

A copper clad panel was treated according to example VII

through to the step of exposing the panel to a palladium tin chloride solution. This step was followed by rinsing and then dipping in 5% fluoroboric acid solution, which is a solvent for the tin component of the palladium tin chloride sites deposited on the walls of the openings. Then, the panel was coated at 3 A / dm in a bath with an electrical copper plating solution formulated according to the present invention and containing:

Copper sulfate 75 g / 1

Sulfuric acid 190 g / 1

Chloride ion 50 ppm

Copper Gleam PC (registered trademark) 5 ml / 1 35

After depositing a 35 µm thick copper layer, the panel was rinsed, dried and a positive photoresist etching mask was applied by known method, covering the desired wiring pattern including the coated bores. The copper not protected by the mask was removed by etching and then the resistance mask was removed 8302344 * V-18 - by standard methods to form a finished printed circuit board.

EXAMPLE IX

This example describes the manufacture of a printed circuit board of the Hague type cattle. A known method has been used to form a multilayer assembly by combining individual layers of circuit patterns on insulating supports and forming them into a laminate. After perforations were made and the tags removed from the copper layers, which were part of the walls of the openings, the laminate was further processed as described in Example VII or VIII.

EXAMPLE X

This example describes the manufacture of a printed circuit board using an uncovered laminate, which does not have a copper foil on its surface (s).

The surfaces of the panel were provided with an adhesive layer and with openings to be metallized and this layer was treated according to the method of Dutch patent 164,178 to make it microporous and hydrophilic. The panel was attached to an electrical coating apparatus to provide a conductive edge which formed a suitable bonding surface and subjected to the filaments described in Example 8 to form the desired printed wiring pattern.

EXAMPLE XI

Copper-clad FR-4 epoxy glass laminate panels were apertured, cleaned and treated as described in Example 1 through treatment with a palladium tin chloride solution. After these steps, the panels were rinsed, dried and immersed in one of the following reducing agents (dissolved in 1.5 mole aqueous solution of sodium hydroxide): sodium borohydride; hydroxyl amine. Both panels were electrically coated for 2 minutes according to the invention in the bath of the copper electric plating solution of Example VIII and complete continuous copper films were obtained on the walls of the openings.

EXAMPLE XII

The procedure of Example XI was repeated, except that the palladium tin chloride solution was replaced with an aqueous solution containing a mixture of potassium hexachloroplatinate (IV) and stannous chloride. As a reducing agent, a 1 g / l solution of sodium - 8302344 - 19 - borohydride was used. The walls of the openings were electrically covered with a continuous copper film in less than 5 minutes according to the present invention.

EXAMPLE XIII

The procedure of Example VIII was repeated, except that the bath of copper sulfate and sulfuric acid was replaced by an electric coating bath of copper pyrophosphate. The copper pyrophosphate bath had the following composition:

Copper 32 g / 1 10 Pyrophosphate Anion 245 g / 1

Ammonia 225 g / 1

Temperature 52 ° C

In this solution, the pyrophosphate anion fulfilled the function of the 2 component (C). After 5 minutes in electrical plating at 4.5 A / dm, there was complete coverage of the walls of the openings with copper.

When the procedure was repeated with another panel in the same coating bath after adding 1 ml / l of the commonly used brightener for copper pyrophosphate solutions for coating baths, namely a dimercapto-thiadiazole compound (PY61H (registered trademark)), the walls of the openings were not lined. The dimercaptothiadiazole is strongly adsorbed on the surface of the metal sites of palladium and prevents deposition at these sites.

EXAMPLE XIV

The procedure of Example VII was repeated, except that after the treatment with palladium tin chloride solution and rinsing, the copper-coated panels were immersed for 30 seconds in a solution containing fluoroboric acid (100 ml / l) without drying and hydroxyethylenediamine triacetic acid (4 g / l), then rinsed and electrically coated according to the invention in an electric coating solution bath, which was the same as in Example 1, except that as the nonionic surfactant Pluronic F-127 (registered trademark), a block copolymer of epoxypropane and epoxyethane, was present in the solution as component (C) at a concentration of 0.2 g / l. After 5 minutes of electrical coating at a potential providing a current density of 3.8 A'dm 35, the walls of the openings were found to be covered with a full continuous copper film.

EXAMPLE XV

In the tests A to O below, the procedure of example XIV was repeated, in tests A and B the same and in examples 8302344

* V

C-0 other surfactants were used as component (C), while the concentrations, flow densities and coating times were used as indicated below. In all cases, after the electrical coating treatment, the result was a complete, void-free, continuous copper film covering the walls of the openings.

Test Capillary Active Concurrent-Current-Coating 2 _ medium g / l unit A / dm time, minutes A Pluronic F-127 0.2 3.8 5 B Pluronic F-127 0.2 5.92 3 10 C Carbowax 1540 0.3 3.8 5 D Carbowax 1540 0.3 5.92 3 E Pluronic F-68 1.0 3.8 5 F Pluronic F-68 1.0 5.92 3 G Pluronic L-42 1.0 3 .8 5 15 H Polyox WSR 80 1.0 3.8 15 I Carbowax 4000 0.5 3.8 15 J Olin 10G 0.5 3.8 15 K Olin 6G 0.5 3.8 15 L Carbowax 20M 0, 5 3.8 15 20 M Pluronic L-64 0.5 3.8 15 N Tergitol Min Foam IX 0.5 3.8 15 0 Carbowax 600 1.0 3.8 15

All surfactants mentioned are registered trademarks. Pluronic is the brand for a range of block copolymers of polyoxyethylene and polyoxypropylene. Pluronic F-127 has a polyoxypropylene base of about 70 oxypropylene units, to which are bonded two polyoxyethylene chains containing a total of about 300 oxyethylene groups.

In Pluronic F-68, the polyoxypropylene portion contains about 160 units. Pluronic L-42 has about 20 oxypropylene units and 15 oxyethylene units.

Polyox WSR 80 is a polyoxyethylene compound with an average molecular weight of 200,000.

Olin 6G and Olin 10G are alkylphenylpolyoxyethylene compounds with 6 and 10 oxyethylene groups, respectively.

Tergitol Min. Foam IX is a polyoxypropylene-polyoxyethylene compound 35 of a linear alcohol.

EXAMPLE XVI

The procedure of Example XIV was repeated, except that the electrical coating solution of the bath was a nickel bath solution, as follows: 8302344 - * - 21 -

NiSO 4 .6H 2 O 195 g / 1

NiCl2.6H20 175 g / 1 H3B03 40 g / 1 PH 1.5

5 Temperature 46 ° C

The nonionic surfactant added as component (C) to this solution was Carbowax 1540 at a concentration of 0.1 g / l.

2

After 15 minutes in electrical coating at a potential providing 3.8 A / dm, the walls of the openings were covered with a full-length, continuous nickel film.

EXAMPLE XVII

To more fully demonstrate the suitability of polyoxyethylene groups in the practice of the process of the invention, sodium r-lauryl sulfate, an anionic surfactant, is widely used in the electrical coating industry and is recommended for use in acidic copper sulfate solutions for electrical coatings baths, examined as follows. The procedure of Example XIV was repeated, except that in one copper plating bath with copper 1.0 g / l sodium lauryl sulfate (Duponol C, registered trademark) as surfactant was added instead of Pluronic F-127 ( registered trademark) and in a second and third solution for an electrical coating bath 1.0 g / 1 ammonium polyether sulfate and 1.0 g / 1 ammonium lauryl polyether sulfate (Sipon E and Sipon A, registered trademarks) were used instead of Pluronic F-127 (registered trade-25 brand). After a coating time of 5 minutes, the two electric coating solution baths containing polyether sulfate and polyether lauryl sulfate, respectively, had yielded continuous copper films covering the walls of the openings, while even after 15 minutes electric coating in the bath solution containing lauryl sulfate, the walls of the 30 openings were not covered.

This experiment demonstrates that a simple linear anionic surfactant, lauryl sulfate, was ineffective for the purposes of the invention. When the surfactant was selected according to the teachings of the present invention, such as by changing the lauryl sulfate structure with the polyether group, the agent became active as a component (C).

EXAMPLE XVIII

The procedure of Example VIII was repeated, except that substituted thiourea compounds were used instead of Copper Gleam PC (registered trademark). In one solution for the copper 8302344® * 22 electric coating bath, 5 mg / l of tetramethylthiouram disulfide was used, and in the second solution 0.8 g / l of allyl thiourea as component (C). After 15 minutes in electrical coating at a potential giving 2 3.8 A / dm, the walls of the openings of printed circuit boards were in both cases coated with a continuous copper film. Numerous modifications are of course possible within the scope of the invention.

8302344

Claims (38)

1. A method of metallizing a non-metallic surface by electrically coating in a vessel provided with a counter electrode and containing an electric coating solution bath containing in ionic form an electrically applied metal (B), the surface having a bonding surface located outside the electrically coated non-metallic surface, characterized in that; (a) forming a number of metallic sites on the surface, which sites contain or consist of a metal (A) different from the metal (B) to be electrically deposited on the surface; (b) exposes the surface including at least part of the terminal surface to the solution of. the electric coating bath, which solution has a certain conductivity and further contains one or more components (C), which cause preferential deposition of metal (B) on the metallic places, which contain or consist of metal 15 (A), compared to the deposition on surfaces formed or consisting of the electrically deposited metal (B); and (c) applies a sufficient potential across the terminal portion at the counter electrode to initiate and cause preferential deposition of metal (B) at the sites containing or consisting of metal (A) for a sufficient time to practically uniform deposition of desired thickness. 2. A method according to claim 1, characterized in that component (C) preferentially adheres to a surface of the raetal type (B) compared to the surface of the metal type (A), and thus to the coating reaction by metal (B) significantly inhibits or reduces molded surfaces without significantly interfering with the coating reaction on surfaces formed by the metal type (A) of the metalized sites. A method according to claim 2, characterized in that component (C) 30 increases the span on metal (B) surfaces. Method according to claim 1, characterized in that the component (c) preferentially adheres to the metal type (A) of the metallic places, wherein component (C) the coating reaction on surfaces formed by the metal (A) of these places significantly enhances as compared to 35 the coating reaction on surfaces of the metal type (B). Method according to claim 4, characterized in that the component (C) reduces the span and thus enhances the coating reaction as compared to the coating reaction on surfaces of the metal type (B). Process according to claims 1 to 5, characterized in that the 8302344 - 24 - component (C) is selected from dyes, surfactants, chelating agents, brighteners and leveling agents. Process according to claim 6, characterized in that the dye (methylene blue or methyl violet) is chosen as component (C). Process according to Claim 6, characterized in that the component (C) used is one of the following surfactants: alkyl phenoxy polyethoxyethanols, nonionic fluorocarbon surfactants, polyoxyethylene compounds and block copolymers of polyoxyethylene and polyoxypropylene. Process according to claim 8, characterized in that component (C) is selected from compounds with 4-100,000 oxyethylene groups. Process according to claim 9, characterized in that compound (C) contains 20-50 oxyethylene groups. Process according to claim 8, characterized in that compound 15 (C) is selected from epoxyethane-epoxypropane copolymers containing 10-400 oxyethylene groups. 12. Process according to claim 6, characterized in that the gelling agent (C) used is a gelling agent selected from 2.4.6- (2-pyridyl) s-triria. zine and pyrophosphate anion. Process according to claim 6, characterized in that component (C) contains a brightening agent and / or leveling agent, selected from N-heterocyclic compounds and triphenylmethane dyes, thiourea, thiourea derivatives, such as allythiourea compounds and tetramethylthiouram disulfide, saccharinic acid and derivatives of o-sulphonic acid . 14. Process according to claim 6, characterized in that Electro-Brite PC-667. Is chosen as the component (C). Process according to claim 6, characterized in that the component (C) Copper Gleam PC (S) is chosen. 16. Process according to claims 1-15, characterized in that the conductivity of the solution of the electric coating bath and the potential applied over the connection surface and the counter electrodes is chosen sufficiently high to allow a deposition rate on the surface of the places with reach the metal type (A), which is at least one order and preferably two orders of magnitude higher than the deposition rate on the surface of the metal type (B). Method according to claim 16, characterized in that the conductivity is set to the highest permissible value relative to the other parameters of the coating process. Method according to claim 16, characterized in that the potential is adjusted so that the voltage drop across the resistance path, which is formed by the solution of the coating bath between the bonding surface and the metallic places containing or consisting of metal (A) and offset between such neighboring places. Method according to claim 18, characterized in that the potential is adjusted to the highest permissible value relative to the other parameters of the coating process. 20. Process according to claims 7-19, characterized in that the metal (A) and the metal (B) are selected from groups Ib and VIII of the Periodic System of Elements, wherein metal (A) differs from metal (B). Method according to claims 7-20, characterized in that the metals (A) and (B) are chosen such that the potential for the deposition of metal (B) or metal (A) is less negative than the potential for the deposition of metal (B) by itself under the conditions provided by the coating process. Process according to claim 20 or 21, characterized in that metal (A) is selected from palladium, platinum, silver and gold. Process according to claim 20 or 21, characterized in that metal (B) is selected from copper and nickel. Process according to claims 1-23, characterized in that the metal (A) is used as a compound or complex in solution in the step for the formation of the metallic places. A method according to claim 24, characterized in that the compound is a metal halide or a double metal halide. A method according to claim 25, characterized in that the double metal halide is a palladium + tin chloride. 27. Process according to claims 24-26, characterized in that the solution contains metal (A) and a tin halide and the treated surface is then exposed to a solvent for tin compounds. 28. Process according to claims 1-27, characterized in that the different metal sites of metal (A) are formed by treating the non-metallic surface with a solution containing metal (A) and then the surface with heat or a exposing reducing agent. 29. Process according to claim 28, characterized in that the heat treatment is carried out for at least 10 minutes at a temperature in the range from 65 to 120 ° C. 30. Process according to claim 28, characterized in that the reducing agent selected is sodium borohydride, formaldehyde, dimethylamine borane or hydroxylamine. 8302344 f - 26 - A method according to claims 1-30, characterized in that the deposition of metal (B) is terminated after forming a continuous film of desired thickness of metal (B) over the non-metallic surface and electrolytically one or more metal layers on this film or part 5 of this film. 32. Process according to claim 31, characterized in that at least two solutions of an electric coating bath of different composition are used, the first solution containing components which maximize the deposition rate on metal (A), while the solutions used thereafter The electrical coating bath can be composed in such a way that the properties of the metal deposition involved are optimized. 33. Process according to claims 1-32, characterized in that openings are formed in a copper-clad insulating plate or in a laminate formed by a number of such plates; a negative 15 imaged of a resist layer on the surface of this copper clad sheet or laminate, which layer releases the areas corresponding to a desired conductor pattern, including the walls of the openings, which are provided with the locations of metal (A ); and after the electrical coating step, the layer of the resist material is removed and the metal etched away into the areas covered by the resist layer to form a printed circuit board. 34. A method according to claims 1-32, characterized in that openings are formed in a copper-clad insulating plate or in a laminate formed by a number of such plates and after the electrical coating step a resistance layer with positive image on the surface of the copper-clad sheet or laminate, which resist layer covers the areas corresponding to the desired circuit pattern, including the openings; and etching away the metal not covered by the positive-image resist layer to form a printed circuit board. A method according to claims 1-32, characterized in that an insulating plate is provided with a bonding surface, which is applied outside the surface to be electrically coated with metal (B). A method according to claim 35, characterized in that the connecting surface has a frame-like shape and is arranged in small areas along the edges of the plate. A method according to claim 35 or 36, characterized in that the insulating plate is apertured before forming the metallic locations of metal (A). 8302344 - 27 - A method according to claims 35-37, characterized in that after the formation of the places of metal (A) the surface is provided with a resistive layer with a negative image, which leaves the areas corresponding to the desired conductor pattern including the walls of the 5 openings and then metal (B) electrically depositing to form the circuit pattern of a printed circuit board. 8302344