SE419239B - PROCEDURE FOR PREPARING PLASTIC SURFACE FOR STROMLOS METAL PROVISION - Google Patents

Description

7316722-3 '10 15 20 25' 30 35 Although the invention is not bound by any particular theory, reference is made to Latimer et al., "Reference Book of Inorganic Chemistry", 3rd ed., New York, MacMillan Co., 1951, pages 390-2, which states that the following conditions apply to equilibrium in an alkaline solution: smnof '+ 21120 = Mnoz + znnou' + uon ', _ 1 <= 16.

It follows that the ratio of MnOu2- to MnOu- can be large at high hydroxyl ion concentration.

Thus, there is a theoretical molar ratio of manganate to permanganate as a function of pH.

Surface treatment of plastic sometimes seems to give good adhesion and sometimes poor adhesion under identical treatment conditions. In addition, it has been shown that acidic permanganate solutions are notoriously unstable, have a short service life and decompose rapidly to manganese dioxide.

It has now been discovered that stable, highly active solutions for the treatment of resinous surfaces are obtained if the molar ratio of permanganate ion (MnOu_) to manganese ion (MnOu2_) is kept below about 1.2 and if the preparations are adjusted with pH regulators or buffering agents, e.g. that a pH in the range 4 - 18 is obtained.

The invention is described in more detail in connection with the accompanying drawing.

Pig. 1 is a graph of the bond strength of electrolessly deposited metals as a function of pH.

Pig. 2 is a diagram of the bond strength of electrolessly deposited metals as a function of the activation bath temperature.

Pig. the bond strength of the metal as a function of the permanganate salt concentration in the treatment of resinous surfaces in activation baths according to a diagram showing electrolessly deposited according to the present invention in preparation for metallization.

The invention thus relates to a stable and technically easy-to-handle means for treating a resinous surface in preparation for electroless deposition of an adhesive metal coating. The agent contains water, permanganate ion and manganese ion, the molar ratio of permanganate ion to manganese ion being at most 1.2 and the pH of the agent being in the range H ~ 13. The agent can be controlled and stabilized for a long life by increasing the ratio of permanganate ion to manganese ion. And the pH value is kept within the specified limits.

Any metal salt of permanganic acid which is stable and soluble in water to an extent of at least about 2 g / l can be used, but it is preferred to use eU: permanganate of an alkali metal, e.g. sodium, potassium, lithium or cesium, or of a alk ß-alkali metal, e.g. calcium. Particularly preferred are sodium and potassium permanganate due to their readiness for a reasonable cost and good profitability.

The amount of salt of permanganic acid used in the solution can vary within wide limits, e.g. from 1 or 2 g / l up to the solubility limit of the permanganate in the medium. However, with sodium or potassium permanganate, particularly good results are obtained in the range 1 - 60 g / l. The degree of activation point increase increases up to 60 g / l, but above this level no further increase in the degree of activation can be observed. Below 10 g / l, the activation rate is slightly too low for good production results to be obtained. The pH value can be adjusted by adding acids or bases in such amounts as are required according to the analysis. A convenient analysis method consists of (1) taking out a suitable aliquot and cooling it to the measuring temperature, e.g. 20 - 2500, (2) measures the pH with a suitable conventional instrument, e.g. a pH meter, (3Y adds a pH regulator, reaches the intended level, (4) notes the amount of pH regulator used and (5) adds a proportionate amount of pH regulator to the bath. , that a reaction bath normally decreases in pH due to absorption of carbon dioxide from the air, for example to 11.5. In this case, concentrated potassium hydroxide is added dropwise to the aliquot, until the pH value reaches 12.5. the amount of potassium hydroxide to the main reaction bath.

The second important parameter, namely the ratio of permanganate ion to manganese ion, is also set by measuring the ratio in an aliquot by titration with potassium iodide. The intended amount of permanganate ion is determined by adding a permanganic acid salt, e.g. potassium permanganate, is added to the aliquot, after which the proportional quantity calculated on this basis is added to the bath. In an alternative method of pH adjustment, an aliquot of the bath is taken and its pH is determined to be, for example, 11.0.

Then calcium hydroxide solution is added slowly by burette until calcium carbonate no longer precipitates. The calcium carbonate is removed by filtration. Then a permanganic acid salt is added to increase the content to the intended level, e.g. 40 g / l. The amount of reagents needed to adjust the aliquot is added to the volume of the bath and the amount added is added to the main bath.

It is desirable to analyze the main reaction bath for pH and the ratio of the amounts of permananate to manganese at intervals of about one week.

In embodiments where buffers are used to adjust the compositions, the buffer substance is generally a salt of a phosphorus, boron, carbonate or bicarbonate compound which is hydrolyzed in the aqueous medium to form a weakly acidic or basic reacting substance, which partly serves to maintain the required ratio between permanganate ion and manganese ion, partly helps to keep the pH within the intended range. In preferred embodiments, a phosphate buffer, a borate buffer or a buffer containing carbon dioxide, a carbonic acid derivative or gaseous carbon dioxide is used as the buffer substance. In particularly suitable embodiments, the buffer substance is phosphoric acid or a salt thereof, e.g. potassium phosphate, monobasic potassium phosphate, dibasic potassium phosphate, potassium peroxide diphosphate, potassium pyrophosphate or potassium polyphosphate or an analogous sodium salt, or boric acid or a salt thereof, e.g. potassium borate, biborate, metaborate or orthoborate or an analogous sodium salt. The amount of pH regulator or buffering agent required varies depending on the desired pH in the range of 4 to 13 and on the type of reaction, acidic or basic, which is induced in the aqueous medium. When using dissolved salts, amounts similar to those applicable to the permanganate salt are used for simplicity. From about 2 to about 60 g / l of phosphate, carbonate, monobasic phosphate, dibasic phosphate or peroxydiphosphate or borate of an alkali metal are used. such as fluorinated hydrocarbons, may be incorporated into the treatment agent. 10 15 20 25 30 35 '7316722-3 Times and temperatures for carrying out the treatment operation may vary. In general, higher temperature promotes activation in a shorter time. Typically, treatment times of 30 to 2 hours or even longer can be used at temperatures from about 20 to about 100 ° C. However, best results are obtained between about H0 and about 70 ° C and for times which may vary between about 2 and about 20 minutes. The treatment contact can be achieved by laying, dipping, spraying and similar methods, which are usually used for treating resinous surfaces.

In the present context, the term "resinous body" refers to plastic material, e.g. shaped articles, laminates and resin coated articles, which are resinous throughout or at least have a resinous outer surface.

For treatment according to the invention, objects with a resinous surface are preferably used, which have been pretreated so that it is temporarily polarized and wettable. Among such treatments, dipping or spraying of the resin layer by a suitable means, e.g. dimethylformamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, ketones, halogenated hydrocarbons or mixtures thereof, and subsequent rinsing in water or a mixture of ethyl acetate and trichloroethylene and the like. This treatment results in a temporarily polarized wettable surface, which is particularly well suited for treatment with the present permanganate solutions in preparation for performing metallization with high final bond strength. This procedure is described in U.S. Patent Application 106 and in several of the embodiments set forth below.

According to the invention, an object is preferably also used, the surface of which is provided with an adhesive resinous layer, in which fine particles of oxidizable and degradable artificial or natural rubber are homogeneously distributed. Such materials are disclosed in U.S. Patent No. 3,625,758.

In the case of certain substrates, e.g. of an acrylonitrile butadiene-styrene resin, it is advisable to carry out a pretreatment by dipping a strong solution of sulfuric acid, nitric acid, phosphoric acid, toluenesulfonic acid, a strong amine and the like.

With such pretreatments, exceptionally good adhesion is achieved without blistering. Surprisingly, these advantages are not achieved on the same substrate, if instead the pretreatment is carried out with a strong solution of hydrochloric acid or sodium hydroxide.

It will be appreciated that if the surface itself is not susceptible to electroless deposition of metal, for example because there is no catalyst in the resin body after the pre-treatment, e.g. copper oxide, which can promote the activation of bonding centers according to the present invention, one must introduce an operation step in which the activated surface is made catalytic for receiving electrolessly deposited metal, before it is brought into contact with the metallization bath. There are many different known ways to make the surface catalytic. Among these are methods in which, for example, the body is first dipped in a stannous ion-containing solution and then the body thus treated is dipped in an acidic solution containing ions of a noble metal, e.g. palladium or platinum. One can also use uniform baths for the same purpose, for example dispersions of colloidal palladium and tin ions, as described in U.S. Pat. No. 3,011,920, or preferably soluble complexes of noble metals, stannous ions and anions, as described in U.S. Pat. 677 938.

The fart body thus activated (and if necessary catalyzed) is then metallized by electroless deposition, for example deposition of a nickel layer from a conventional acidic nickel hydrophosphite bath at a moderate temperature, e.g. 50 - SDOC, or from an alkaline nickel bath at about 20 - 35 ° C.

Instead of electroless nickel plating, electroless copper plating can be carried out in a conventional copper deposition bath, which together with a cupion ion reducing agent contains a complexing agent and other conventional constituents. A suitable pre-copper bath may, for example, contain 30 g / l of copper sulphate pentahydrate, 150 g / l of Rochelle salt, 1 ml / l of wetting agent, 30 mg / l of sodium cyanide and 15 ml / l of formaldehyde (37%) and sodium hydroxide in an amount sufficient to to give pH 13.

Other suitable electroless metallization baths are described in U.S. Pat. Nos. 3 HMS 350, 3 H37 507, 3 H33 828 and 3,625,758.

Preferably, although not necessarily, the treatment with the described agent for promoting the activation of bonding centers is followed by a treatment with another agent for "neutralization" of the permanganate before catalysis and electroless metal deposition. This agent appears to help remove any excess permanganate from the resin surface and prevents dilution and other possible effects, caused by residual strong oxidizing agents, on the following steps and treatment baths in the process. As a neutralizing agent, stannous ion can be used, e.g. such as is formed in an acidified stannous chloride bath. Also suitable are bisulfite ion, hydroxylamine, sugar or virtually any water-soluble compound which can be oxidized by permanganate. All that is required for the desired neutralizing effect to be achieved is that the permanganate-treated substrate is kept for a short time in an aqueous solution of the neutralizing agent, e.g. at a concentration of between 2 and 100 g / l, and then thoroughly rinsed with water, before carrying out the next step.

It has been observed that particularly good adhesion is obtained if the metallization bath is arranged in a known manner for slow deposition of metal. A suitable approach is to start the precipitation in a slow-working bath and then transfer the treatment object to a bath for rapid electroless precipitation. This ensures that the delay in this step is kept down.

An object of the invention is also to provide a regeneration process for removing organic substances and producing permanganate by disproportionation of manganate.

This process consists of (a) bubbling carbon dioxide into the composition to be renewed to lower its pH from 12.5 to between 11 and 11.5 (the disproportionation is more easily carried out within this pH range), (b) then the composition heats to and maintains at 80 - IUÛOF for approximately 15 minutes (during this time organic residues and the manganese ion ion to permanganate ion and manganese dioxide are destroyed), (c) allowing the composition to cool, for example to 20 - HSOC, and adding a carbonate precipitant, e.g. calcium hydroxide or oxide, slowly to raise the pH again to 12.5 (carbonate precipitates) (d) filters the composition to free it from manganese dioxide and carbonate and (e) after analysis and appropriate additives of permanganate obtain a regenerated composition.

The following examples illustrate the process of the present invention and the objects metallized by the process.

Example 1 This example illustrates the use of an activation bath, in which the pH and the ratio of permanganate to manganate are adjusted by means of a strong base.

An epoxy resin glass laminate having a resin-rich surface of epoxide-phenol-nitrile rubber is metallized in the following manner. a) The surface is cleaned and rinsed with water. b) The laminate is kept for 2 minutes at about 6000 with gentle stirring in an aqueous solution containing H0 g / l potassium permanganate and potassium hydroxide to pH 12.5. c) The surface is rinsed in stagnant (non-running) water; d) The surface is neutralized for 5 minutes at 20 - 25 ° C in an aqueous solution of 50 g / l hydroxylamine hydrochloride and 20 ml / l conc. hydrochloric acid (37%). e) Surface deppee 2 min at 20 - 2s ° C in laps, containing 300 ml / l 37% hydrochloric acid. f) Rinse the surface with running water at a temperature of 20 - 25 ° C; g) The surface is dipped for 10 minutes in a sensitizing solution of 1 g / l palladium chloride, 60 g / l stannous chloride and 100 ml / l 37%. hydrochloric acid in water, which solution contains a complex of palladium chloride and stannous chloride (U.S. Pat. No. 3,672,938). The surface is rinsed with water. i) The surface is dipped at 55 ° C in a bath for electroless copper, e.g. according to U.S. Pat. No. 3,672,986 (Example 7), for about 50 hours for electroless application of an approximately 0.025 mm thick flexible copper coating. j) The surface is rinsed with water and air dried. The metal layer thus applied is tested for adhesion by measuring its peeling strength according to a standard procedure. High values of peeling strength are obtained, namely above 1.8 and all the way up to 2.2 kp / cm with an average value of 1.9 kp / cm for 6 samples. Example 2 The procedure of Example 1 is repeated with a compression plate of a butadiene-acrylonitrile] styrene graft polymer containing minor amounts of stabilizers, plasticizer and pigment ("Cycolac EP 3530", prepared from Borg Warner Corporation Marbon Chemical Division), and the process begins with a pretreatment step, consisting of dipping in 80% sulfuric acid at 23 ° C for a period of 3 - 10 minutes. Dipping in the activation solution with pH 12.5 is performed for 10 minutes at 23 ° C. Excellent bond strengths and blow-free metallization layers are obtained.

The following examples illustrate the use of baths in which the ratio of permanganate to manganate and pH are adjusted with buffering substances.

Example 3 A molded plate of butadiene-acrylonitrile-styrene graft polymer ("Cycolac EP 3530") is metallized in the following manner. (a) The surface is cleaned for 5 minutes at 70 ° C in water containing 50 g / l trisodium phosphate. (b) Rinse the surface with water. (c) Dip the plate for 5 minutes at about 20-25 ° C with gentle stirring in an aqueous solution containing 200 ml / l of methyl ethyl ketone and 1 ml / l of nonionic wetting agent ("Triton X-100", Rohm & Haas Co.). (d) Activation of binding centers is promoted by dipping for 10 minutes at 7000 in solution 3 according to Table I. (e) The plate is rinsed in stagnant water. (f) The plate is optionally neutralized for 5 minutes at 20 DEG-25 DEG C. in an aqueous solution containing 30 g / l of stannous chloride dihydrate and 330 ml / l of 37%. hydrochloric acid.

Sensitization and metallization are then performed by the method of Example 1, steps e - j.

The metallized plate is tested for adhesion by measuring the peeling strength in the usual way. A high peeling strength of 1.3 - 1.8 kp / cm (width of the torn metal strip) is obtained. Example H The procedure of Example 3 is repeated with the change that solution 4 according to Table I was used in step d. After electroless metal deposition, strongly bonded metal layers are obtained. Example s The procedure of Example 3 is repeated with the change that solution 5 according to Table I was used in step d. After electroless metal deposition, strongly bonded metal layers are obtained.

Example 6 The procedure of Example 3 is repeated with the change that solution 6 according to Table I was used in step d. After electroless metal deposition, strongly bonded metal layers are obtained.

Example 7 The procedure of Example 3 is repeated with the change that solution 7 according to Table I was used in step d. After electroless metal deposition, strongly bonded metal layers are obtained.

Example 8 The procedure of Example 3 is repeated with the change that solution 8 according to Table I was used in step d. After gg electroless metal deposition, itarically bonded metal layers are obtained.

Table I Composition of activation bath (components in grams) Solution g 3 g g = - = 1 '_a_ KMn0p _ H0 U0 UU H0 40 40 25 K fl zpou ao - - - - - K2HP04 - 40 - 30 -. ~ K3POu - - H0 - - - 1 <2 C03 - - - - - uo - K3B03 - - - - - 40 30 Water 'to (ml) 1000 1000 1000 1000 1000 1000 pH 7 k, 2 8.9 11.6 12.5 11.0 10-12 * Sufficient KOH is included to reach pH 12.5. A series of activation solutions, containing one R / 1 potassium permanganate and 30 g / l dipotassium hydrogen phosphate were prepared and adjusted to different pH values in the range 11 to 13. Activated surfaces were treated with the general the procedure of Example 1, but using 7000 activation bath temperature and 15 min dipping time. The neutralization bath contained 50 g / l of hydroxylamine hydrochloride and 20 ml / l of 37% hydrochloric acid. After metallization, the peeling strengths were determined in kp / cm, and the results are graphically illustrated in Fig. 1. The upper curve shows data from activation of a certain type of resin layer, and the lower curve shows data from activation of another type of resin layer, namely a binder avepoxide-phenol-nitrile rubber. These data show that high scaling strengths are obtained and that a particularly favorable maximum is obtained at pH values between 12 and 12.5.

Similarly, the effect of temperature on the peeling strength was determined by preparing an activating bath containing 40 g / l potassium permanganate and 30 g / l dipotassium hydrogen phosphate and adjusting to pH 12.5 with potassium hydroxide.

The general procedure of Example 1 was applied with an activation time of 15 minutes and the temperature of the activation bath was varied in the range of 60 to 80 ° C. The results are graphically illustrated in Fig. 2. The upper curve represents data from activation of a resin layer of a certain type, and the lower curve indicates data from activation of a resin layer of another type. In addition, the effect of the permanganate concentration on the peeling strength was determined by preparing an activating bath containing 30 g / l dipotassium hydrogen phosphate, adjusted to pH 12.5 with potassium hydroxide, after which the permanganate concentration was varied in the range of 20 to 50 g / l. These baths were used in the procedure of Example 1 with an activation time of 15 minutes, and the activation bath temperature was maintained at 7000. These data are graphically represented in Fig. 3. The upper curve shows data from activation of a certain type of resin layer. and the lower curve shows data from activation of a second type of resin layer, namely a binder of epoxy plastic, phenolic plastic and nitrile rubber.

Instead of the treatment bath with copper, it is possible to use electrolessly operating treatment baths containing other metals in groups Ib and VIII, e.g. the nickel baths described in 7316722-3 10 15 20 25 30 35 12 Brenner, "Metal Pinishing", Nov 1954, pages 68-76, or the gold baths described in U.S. Pat. No. 2,976,181. well-known cobalt baths, silver baths and other treatment baths are used.

Other modifications are possible within the scope of the invention. Thus, in the activation solutions instead of water alone, a mixture of water and other non-oxidizable solvents can be used, e.g. acetic acid.

Instead of potassium permanganate, you can use sodium or lithium permanganate. Instead of potassium carbonate, potassium hydroxide, etc. the corresponding sodium and lithium compounds can be used.

In some cases, instead of methyl ethyl ketone (Example 1, step c), dimethylformamide, methyl chloride, dimethyl sulfoxide or N-methyl-2-pyrrolidone may be used. In comparison with the known processes mentioned at the outset, the method according to the invention provides an improved means for promoting the activation of bonding centers on resinous surfaces in preparation for bringing them into contact with an electroless working metallization solution.

The stabilized permanganate solutions according to the invention are with respect to surface activity and consequent adhesion fully equivalent to the well-known chromic acid baths according to the state of the art in the field of metallization of plastic objects.

By using the treatment baths according to the invention, one gets rid of the very costly and difficult to master waste management problems, which are associated with the use of chromic acid baths and chromic acid-sulfuric acid baths. The accompanying health risks to which work personnel are exposed when handling the equipment are avoided, and the need for expensive construction materials for tanks and other equipment, e.g. heaters, mixers and exhaust systems.

In addition, permanganate solutions are stable within the indicated pH range H-13 in contrast to the strongly acidic treatment baths proposed by other experts in the field. It has been found, for example, that strongly acidified aqueous solutions of permanganate, e.g. with 2 - 10 g / l calumper manganate and 600 ml / l conc. sulfuric acid or 500 ml of 85% phosphoric acid, undergoes unexpected and rapid decomposition. On the other hand, aqueous solutions of permanganate, which have been made strongly alkaline with strong bases, are admittedly very stable, but they are ineffective as fast-acting activators for the formation of bonding centers and they give low values of adhesion or binding strength. The invention is not limited to special articles, e.g. printed circuit boards.

Claims (6)

7316722-3 lä PATENTKRAV Process for pretreatment of a plastic support plate provided with a rubber adhesive adhesive layer for electroless metal deposition and application of an adhesive metal layer for the production of a printed coupling plate, characterized in that (a) the surface of the support plate is treated with dimethylformamide, dimethylsulfoxide , N-methyl-2-pyrrolidone, a ketone, a halogenated hydrocarbon, a concentrated mineral acid or a strongly basic amine, (b) treating the surface with a treatment solution containing permanganate ion and manganese ion in a ratio of not more than 1.2 and has a pH of 11 - 13, at a temperature of 20 - 10000, preferably H0 - 7000, for a treatment time of 0.5 to 120 minutes, preferably 2 - 20 minutes, and (c) treats the surface with a solution of a reducing agent, e.g. hydroxylamine. Process according to Claim 1, characterized in that the pH of the treatment solution is maintained at 12.5. 3. A method according to claim 1 or 2, characterized in that the ratio of permanganate ion to manganese ion in the treatment solution and its pH value is adjusted by continuous or semi-continuous addition of a pH-regulating substance. 4. A process according to claim 1, 2 or 3, characterized in that the ratio of permanganate ion to manganese ion in the treatment solution and its pH value are adjusted by adding buffer, phosphate, carbonates, borates being preferably used as buffer substances. and mixtures thereof or carbon dioxide. Process according to Claim 2, characterized in that since the pH value of the treatment solution has been lowered to a value of 11.5 by absorption of carbon dioxide from the air, potassium hydroxide is added to the solution until the pH value has been adjusted to 12, 5. Process according to any one of claims 1 to 5, characterized in that a fluorinated hydrocarbon is added to the treatment solution. _ PUBLICATIONS PRESENTED: United Kingdom 1 105 609 (cosf 27/22) us s 141 797 (us-ans)