NL7906856A - PROCESS FOR STREAMLESSLY COOPING A COPPER COATING WITH IMPROVED COATING SPEED. - Google Patents

Description

τ>? VG 8369 _______________________

Method for electroless deposition of a copper plating with an improved plating rate.

De-energized, e.g. Autocatalytic metal deposition solutions for forming metal layers on non-metallic or metallic substrates without the need for an external electron supply are well known. Such solutions differ from electroplating baths, which require an external source of electrons, and they are also different from so-called displacement metal plating and metal mirroring methods, where the deposited metal is only a few millionths of an inch. C2.5 cm] thick.

A lack of previous copper electroless deposition methods was that the coating solution was initially unstable or became unstable after a short period of operation and had to be discarded thereafter. Such solutions also tended to provide electroless copper coatings that were dark in color and tended to flake off the substrate on which the deposition had occurred.

To overcome these drawbacks, a number of compounds have been proposed as stabilizing agents to extend the useful life of the electroless metal deposition solutions and to improve the quality of the copper plating. These agents include 2-mercapto-benzothiazole (U.S. Patent 3,222,195], 2,5-dimer-capto-3,4,4-thiodiazoo and 8-mercaptopurine (U.S. Patent 3,436,233], o-phenanthroline (U.S. Patent 7906856) * * - 2 - 3,615,735), 1-phenyl-5-mercaptotetrazoal (U.S. Pat. No. 3,804,638), 2,2'-dipyridyl and 2- (2-pyridyl) -benzimidasole (U.S. Patent 4,002,786 ) and benzothiazole thioether polyethylene glycol (U.S. Patent 5 3,843,373).

Still other stabilizers are described in U.S. Patent 3,257,215, e.g. thiazoles, isothiazoles and thiozines, in U.S. Pat. No. 3,793,038, e.g. benzotriazole, diazooi, imidazole, pyrimidine 10 and others, and in U.S. Pat. No. 3,377,174, e.g.

2,2'-dichinoline, 2,9-dimethylphenanthroline and 4.7-diphenyl-1,10-phenanthroline.

U.S. Pat. No. 3,708,329 discloses that the addition of a heterocyclic aromatic nitrogen compound having up to 3 rings, with a hydroxyl group bonded to one of the rings, results in a marked increase in the stability of electroless copper plating solutions without adversely affecting the coating speed. See also Schoenberg, Journal of the Electrochemical 20 Society, 118, 1571 (1971). Although Schoenberg speaks in U.S. Pat. No. 3,708,329 to improve coating rates, the fastest bath described by Schoenberg has a coating rate at room temperature of only 3.8 microns / hour. However, even this slow speed is higher than any long-term speed disclosed in any of the above-referenced patents. The fastest long-term coating rate described for electroless copper coating solutions currently available commercially, e.g. Dynachem DC-920 and MacDermid 30 9027, is 5 μm / h. U.S. Patent 3,377,174 discloses a short term coating rate of 0.5 microns in a 5 minute period.

So far it was considered necessary to operate 7906856 J without current? To run copper coating solutions at a slow rate, e.g. less than about 6 micrometers / hour, to provide a good quality copper deposit, i.e., a coherent, structurally stable, thin film of Cu, adhering to the surface to be coated. Experience in the art has further been that higher coating rates resulted in the production of a poor quality copper deposit, e.g. a deposit that flakes or tends to flake off the surface or that is non-oherent.

As used in the present application, by "adhesive copper cladding" is meant an electroless copper cladding, which can be stripped from a coated insulating substrate in the form of a thin, integral film, so that after stripping the structural integrity or consistency. if a film is preserved without crumbling.

As used in the present application, by "non-adhesive copper cladding" is meant an electroless formed copper cladding that flakes or tends to flake off the coated substrate.

The object of the invention is to increase the speed at which the copper can be deposited without current.

A further object of the invention is to provide methods and compositions for increasing the velocity for electroless forming an adhesive copper cladding.

Another object of the invention is to provide solutions for electroless deposition of copper at high coating rates.

Yet another object of the invention is to provide materials and methods for electrolessing adhesive copper coatings at high rates which have hitherto not been achievable.

7906856 - £ * - 4 -

Other and further objects of the invention will become apparent from the description below and from the examples.

According to the invention, it has been found that these and other purposes can be achieved by the method of increasing the rate at which adhesive copper can be deposited from a solution for electroless deposition of copper having a pH above 10, which is thereby characterized in that the solution incorporates an agent which causes depolarisation of the anodic partial reaction of the solution or the cathodic partial reaction of the solution or both reactions, and the solution is operated at a pH above the peak coating rate-pH of the solution without the depolarizing agent present to deposit electroless copper at a rate greater than the coating rate of the solution without it. said agent at the same pH and temperature.

In general, the depolarizing agent is most preferably capable of depolarizing at least 20% and at most 100% or between about 35% and 90% of the anodic partial reaction or the cathodic partial reaction of the solution, or both, to provide. In other words the depolarizing agent should be able to accelerate at least 20% and at most 100% or between about 30% and 90% the cathodic partial reaction or the anodic partial reaction of the solution, or both.

The increase in the rate at which adhesive copper can be deposited from a particular electroless copper solution by carrying out the present process will vary within wide limits depending on the composition used and the desired quality of the copper plating.

Generally, by performing the present method, the speed increases by at least 300% or more depending on 7906856

/ I

- 5 - the composition of the solution. However, speed increases of up to 1 or 1.5 orders of magnitude are possible, e.g. 10 times [1000%] or even 50 times [5000%]. Achieving such speed increases was unexpected and surprising.

Likewise, the rate at which adhesive copper can be deposited over a long period of time from a particular electroless copper deposition solution by practicing the present process will vary within a wide range, again depending on the composition being applied. the quality of the desired copper cladding. When the additive is present, the present solutions are characterized by a coating speed at room temperature of greater than 7 micrometers / hour and usually greater than 9 microns / hour, or between 9 and 25 microns / hour and higher. Increased temperature allows for speeds of up to 70 micrometers / hour or even higher. Again, reaching such speeds was unexpected and surprising. In addition, such speeds can be achieved for periods of time ranging up to 8 hours and more. Typical operating times of e.g. 5 minutes to e.g. 8 hours. With a proper supplement, the solutions can be used continuously for long periods of time, e.g. weeks. It should be noted that the high coating rates of the solutions usually do not require a long continuous coating period.

The electroless formation of a copper cladding according to the invention will result in many process advantages, such as shorter cladding times and, in connection with this, an increased production capacity. Compared to conventional engineering methods, the methods and compositions of the invention require less equipment, lower investment costs and less energy. In contrast to the conventional technical methods, the present method is particularly suitable for use in automatic coating systems with relatively short residence times.

The electroless solution of copper coatings according to the invention contains copper ions, a copper ion complexing agent, a reducing agent and a pH adjusting agent and is characterized by a coating rate which first increases the coating rate and a allows peak coating rate to pass and then decreases as a function of pH, with the increase in coating rate occurring above pH 10 and usually above pH 11. The process of the invention includes: CA] operating the solution for electroless copper deposition in the presence of at least one accelerating or depolarizing agent; and (B) adjusting the pH of the copper electroless deposition solution in the presence of accelerating or depolarizing agent at a pH higher than the pH of the peak coating rate of the solution without said agent is present to deposit electroless copper at a rate greater than the coating rate of the solution without the accelerant at the same pH and temperature.

Preferably, the accelerating or depolarizing agent is selected from compounds containing a delocalized pi bond, such as 25 Ca] heterocyclic aromatic nitrogen and sulfur compounds;

Cb] non-aromatic nitrogen compounds with at least one delocalized pi bond;

Cc] aromatic amines, and Cd] mixtures thereof.

The terms "depolarizing agent" and "accelerating agent" can be used interchangeably.

The preferred depolarizing or accelerating agents of the invention 7906856 4 * 7 have a free electron pair on the nitrogen atom adjacent the pi bond.

The heterocyclic aromatic nitrogen compound CA) Ca), e.g. are selected from pyridines, e.g. pyridine, cyano-5 pyridine, chloropyridine, vinylpyridine, aminopyridine, 2-pyrazole-C4.3-c) -pyridine, 3-v-triazoal-C4.5-b) -pyridine, 2,2'-di-pyridyl-picolines , and such; pyridazine, pyrimidines, e.g., γ-diazine, 2-hydroxypyrimidine, 2-oxy-6-aminopyrimidine (Ccytosine), and the like pryzines; triazine, tetrazinein indoles, e.g. indole, tryptamine, tryptafan, 2,3-indolinedione, indoline, and the like purines, e.g. 6-aminopurine Cadenine), phenanthrolines, e.g. o-phenanthroline; quinolines, e.g. 8-hydroxyquinoline; azoles, e.g. pyrrole, dibenzopyrrole, pyrroline, and the like diazoles, e.g. 1,2-pryzole, 1,3-imidazole, and the like triazoles, e.g. pyrrodiazole, benzotriazole, diphenyl triazole, isotriazole, and the like tetrazoles, and benzodiazoles, e.g. indazole, benzimidazole, and the like.

Also included are mercapto derivatives and thia derivatives of any of the foregoing compounds, such as mercapto-pyridines, mercaptopyrimidines, thiazoles, thiazoline, thiazolidine, mercaptothiazoles, imidazole thiols, mercaptoimidazole, mercaptopurines, mercaptochinazolinones, thiodiazoles, thiodiazoles, thiodiazoles , and such.

The non-aromatic nitrogen compound, CAJCb), e.g. are selected from urea compounds, guanidines and derivatives thereof.

Preferably, the aromatic amine, CA) Cc) is selected from p-nitrobenzylamine, anilines, phenylenediamines and mixture thereof.

Preferably, the polarizing or accelerating agent will be present in a small effective amount, e.g.

3 usually at least about 0.0001 to about 2.5 g / dm, 790 6 8 56 3 - s - 8 - more especially about 0.0005 to 1.5 g / dm and preferably 3 about 0.001 to about 0 .5 g / dm. In general, the amount of depolarizing or accelerating agent used will depend on the particular agent used and on the composition of the solution.

According to another aspect of the invention, the electroless metal deposition solution may also contain, in addition to copper ions, ions of a metal or metals selected from the transition metals, preferably Group VIII, and preferably cobalt 10 and / or nickel . These can be added in the form of metal salts, e.g. halides or sulfates, optionally with a suitable complexing agent, e.g. a tartrate. Generally, amounts of from about 0.005 to about 30% by weight of the group of VIIII metal, based on the weight of the copper salt, are used.

The copper ions are usually made available in the form of a water-soluble copper salt. The choice of. the salt is essentially a matter of cost. Copper sulfate is often preferred, but copper halides, e.g. chlo-ride and bromide, copper nitrate, copper acetate, as well as other commercially available copper organic and inorganic salts, may also be used. Although water-soluble metal salts are preferred, usually water-insoluble compounds, such as copper oxide or copper hydroxide, can be used because they are solubilized by the complexing agent or by means in the coating solution.

The copper ion complexing agent is selected from compounds commonly used for this purpose, such as Rochelle salts, the sodium Cmono, di, tri and tetrasodium salts of ethylenediaminetetraacetic acid Chierna sometimes referred to as " ΕΠΤΑ "], diethylenediamine pentaacetic acid, nitriloacetic acid and its alkali salts, gluconic acid, glucoic acid 790 6 8 56 * 9 - sodium triethanolamine, diethylaminoethanol and glucono-acetone, eg modified ethylenediamine acetates, eg N-hydroxyethyl ethylene diamine triacetate, phosphonates, e.g. ethylenediamine tetraethylene phosphonic acid] and hexamethylenediamine-5 tetra (methylene phosphonic acid).

Preferably, the complexing agent is of the alkanolamine type. Examples are NNN'.N'-tetrakis- (2-hydroxy-propylethylenediamine (hereinafter sometimes referred to as "Quadrol"), triethanolamine, ethylene nitrilotetraethanol, nitrilitri-2-pro-10 panal, tetrahydraxyethylenediamine and N-hydroxyethyl-N.N '.N'-

Ctrihydroxypropylethylene diamine. These are commercially available or can be prepared by known methods.

The reducing agent is selected from e.g. formaldehyde and formaldehyde precursors or derivatives, e.g. paraformaldehyde, trioxane, dimethylhydantoin, glyoxal, and the like boranes; borohydride; hydroxylamines; hydrazines and hypophosphite.

The pH can be controlled using a pH adjuster, preferably a water-soluble alkali metal or alkaline earth metal hydroxide, e.g. magnesium hydroxide, calcium hydroxide, potassium hydroxide, sodium hydroxide, and the like. Among them, sodium hydroxide is preferred, mainly because of the cost. During the process, the pH is recorded and, if necessary, increased or decreased by the addition of appropriate amounts of the pH adjusting agent.

It may be desirable to use a small, effective amount of a wetting agent or 3 'wetting agents, preferably in amounts less than 5 g / dm.

Examples of such commercially available surfactants are Pluronic P85, BASF-Wyandotte Carp., A non-ionic block copolymer of ethylene oxide and propyl RTFr] lene oxide, and Gafac 'RE B1Q, GAF Corp., an anionic phosphate ester. .

7906856 - 10 -

The concentrations of the various constituents in the electroless copper plating solution which can be used therein can vary within wide limits, as follows: 5 Copper salt 0.002 - 1.20 mol of reducing agent 0.03 - 3.00 moles cupric ion complexing agent 0.5 - 20 times the number of moles of Cu alKali metal hydroxide sufficient to provide a pH of 10 - 14 and preferably 11 - 14, measured at room temperature water sufficient for Mon- 3 15 Ken of 1 dm.

When non-aqueous solvents are used in place of water, they are preferably selected from e.g. dimethyl formamide, dimethyl sulfoxide and acetylacetate.

More particularly, the coating baths of the invention include: a soluble cuprous salt, preferably cupric sulfate 0.002-0.4 mole of alkali metal hydroxide, preferably sodium hydroxide, to provide pH 11.2-13.7, measured at room temperature formaldehyde (reducing agent) 0.06 - 0.50 moles cupric ion complexing agent 0.002 - 2.00 moles water sufficient to make 1 dm ^

In practice, concentrated solutions or compositions can be prepared for later dilution to working compositions as described herein.

7906856 ί * - 11 -

It will be understood that if the baths are used in the coating, the cupric salt, the reducing agent and the cu-ion complexing agent and the depolarizing agent and other compounds present in the fresh coating solution 5 may be replenished from time to time. .

During the operation of the bath, the pH of the solution and the presence of the depolarizing agent in the solution will be recorded and adjusted as indicated in the description. The depolarizing compound will be added in an amount of at least 0.0001, at 3 preferably at least 0.0005 and at most 2.5 g / dm. In the presence of the depolarizing agent, the pH of the solution will be adjusted in the desired manner to obtain a faster coating rate compared to the solution without the accelerator at the same pH.

When using the baths, the surface to be coated is preferably free from grease and other contaminants.

When a non-metallic surface is to be coated, the surface to be coated is first treated by conventional methods to render it susceptible to electroless deposition of copper.

In case a metal surface, such as copper foil, is to be treated, the surface is preferably degreased and treated to free the surface of any oxide present.

For inert metals, e.g. stainless steel, improved deposition is obtained when the metal foil is dipped in a palladium chloride / hydrochloric acid solution for about 1 minute before being exposed to the coating solution.

Following the pretreatment and / or sensitization, the surface to be coated is dipped or otherwise exposed to the autocatalytic copper baths, e.g. by spraying or sprinkling 7906856 * - 12, then leaving the surface to be coated in the bath until a copper deposit of the desired thickness is built up. In practice, the substrate or object to be coated can be stationary and the solution to be moved in contact therewith, or, alternatively, the solution or "offset" or part to be coated can be continuously advanced through a vessel or rather a reservoir containing the coating solution or a spray curtain of the coating solution.

Generally, the electroless metal deposition solution is prepared by adding the complexing agent to an aqueous solution of the copper salt or salts to form a water-soluble complex or chelate of the copper cation. The complexing agent can be added as a base, salt or other water-soluble derivative. The other ingredients are then dissolved in the solution in any desired order.

The method according to the invention can be carried out within a wide temperature range. E.g. can temperatures between 15 ° C and the boiling point, e.g. 100 ° C, are used and temperatures between 20 and 8 ° C are preferred. It is noted that clear, adhesive copper coatings are obtained with good coating rates even at room temperature, e.g. at 25 ° C.

Applications according to the invention include high-speed application of conductive metal layers or conventional non-conductors for static elimination purposes, or insulating cable for coaxial cable formation or on copper mirror glass.

The rapid deposition rates obtainable by the practice of the invention allow the formation of metal layers by electroless deposition at rates comparable to those obtained by conventional electroforming copper techniques and electroless nickel techniques.

The invention is particularly suitable for the manufacture of printed circuits and for the metallization of plastic objects.

The copper layer can be bumped to a desired thickness by electroless metal deposition or by electroplating with copper or combinations of metals such as copper, nickel and chromium.

When formaldehyde is the reducing agent, the currentless copper deposition reaction can be represented as divided into two partial reactions: Λ. CH 0 + 2 OH * -} HCOO "+ 1/2 H2 + H2Q + le" C. Cu + 2e -> Cu

Without wishing to be bound by theory, in analogy to electroplating, the "A" partial reaction is the anodic reaction and the "C" partial reaction is a cathodic reaction. When the electroless copper plated surface is rendered anodic in an electrolysis cell, the rate of the anodic reaction will increase with an increase in the current density.

As the current density increases, the potential or polarization of the surface becomes more positive. When the electroless copper deposition solution is modified by adding an accelerating or depolarizing agent according to the invention, the polarization resulting from a given current density is less than the polarization obtained from the coating solution without the accelerating agent. This difference in potential or depolarization is a measure of the acceleration of the anodic reaction.

Polarization measurements can be performed by standard galvanostatic electrochemical techniques, in which a predetermined current is passed through the solution from the anode to the cathode. When the cathode is the test electrode, the current passing between the anode and the cathode will induce polarization of the test electrode, the anode. The polarization is the difference of the potential between the test electrode and a reference electrode, e.g. saturated calomel electrode, when current is passed and when no current is passed, e.g., at equilibrium.

With reference to Fig. 1, depolarization D indicates the decrease in polarization B, at current density i, brought about by the presence of an accelerator according to the invention. The depolarization rate expresses the same effect in terms of percentages. When D is zero, there is no acceleration based on depolarization. Larger values of D correspond to larger accelerations.

Analogously, with regard to cathodic polarization, when a surface to be coated in a strawless copper solution is made the negative electrode of an electrolytic cell, it will provide the means for measuring the cathodic reaction. In an analogous manner, depolarization of the cathodic reaction by an accelerator is a measure of the acceleration of the cathodic reaction.

The acceleration effects of the agents on the anodic or cathodic reactions appear to vary with the ligand or complexing agent for the copper ions.

Using electroless coating solutions of the compositions below, the depolarization percentages achieved by a number of accelerators were measured as indicated herein.

7906856 4 - 15 -

Bath compositions for Tables A and B Tartrate ligand bath 3

Rochelle salt 54.3 g / dm 3 3 formaldehyde [37% solution] 10 cm / dm 5 CuS04.5H20 18.0 g / dm3

Rochelle salt: Copper (mol ratio) 5.0: 1 pH 12.8 temperature 25 C _ + _ 1 atmosphere argon passed through 3 10 accelerator 0.001 g / dm

Quadro1 ligand bath ^ R.N.N'.N'-tetrakis- (2-hydroxypropyl) -3 ethylenediamine-y "34 g / dm 3 3 15 formaldehyde (37% sol) 10 cm / dm

CuSO4.5H20 18.0 g / dm3

Quadrol: copper (molar ratio) 1.6: 1 pH 12.8 temperature 25 ° C + 1 ° 20 atmosphere argon passed 3 accelerator 0.001 g / dm EDTA ligand bath 3 EDTA, disodium salt 43.3 g / dm 3 25 formaldehyde (37% sol.) 10 cm / g

CuSO4.5H2Q 18.0 g / dm3

Na2EDTA: copper (mol ratio) 1.6: 1 pH 12.8 temperature 25 ° C + 1 ° 30 atmosphere argon passed through 3 accelerator 0.001 g / dm

When measuring the depolarization rate, the galvanostatic current was made available by a constant current supplying DC source and the resulting polarization 7906856 - IB - potential was recorded on an X.Y recorder. The test results are shown in Table A.

As shown in Table A, these agents can selectively accelerate the cathodic partial reaction, or simultaneously accelerate the anodic and the cathodic partial reactions.

Table A

Anodic and cathodic percentage depolarization

Ligand Accelerator Percentage depolarization _

Anodic Cathodic 10 _ _ _____ _ NNN'.N'-tetrakis- (2-cytosine 79 28 hydroxypropylethylene adenine 82 31 diamine benzotriazole 72 27 sodium 2-mer-captobenzothiazole 79 37 pyridine 70 20 guanidine 0 49 EDTA cytosine 78 56 20 guanidine 0 52 tartrate cytosine 0 35 guanidine 0 35

Cathodic and anodic depolarization caused by the presence of an accelerator may be additive, as shown in Table B. The gravimetric acceleration factor A is defined as the ratio between the velocity of the electroless metal coating in the presence of the additive and the velocity in the absence of the additive.

The percent depolarization measurements in Table 0 were made using the same electroless metal deposition solutions and the same device as used in obtaining the values of Table A.

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7906856 - 18 -

As noted in Table B, the incorporation of cytosine under appropriate pH control caused an increase in the coating rate from ISO to 250% depending on the ligand present in the electroless copper plating solution. Such results were surprising and could not be predicted.

In addition to the classes of compounds specifically mentioned herein, many other classes of depolarizing compounds are known in electrochemical engineering.

It will be clear that such compounds are also suitable for use according to the invention. »

The method of the invention is further illustrated by the following examples, which should not be construed as a limitation.

In the examples, the coating rates were determined using either a "gravimetric" or a "burnout" ("bum-out" J test).

In the gravimetric technique, a stainless steel foil, length 5 cm and width 3 cm, was first cleaned and then sensitized by immersion in a palladium chloride / hydrochloric acid solution for 1 minute, followed by a wash with water. The film was then dipped in the coating bath for about 15 minutes, rinsed and dried at 100 ° C for about 20 minutes, weighed and then treated with nitric acid to etch off all the deposited copper.

The film was then rinsed, dried and weighed again.

The thickness of the copper cladding was calculated from the weight of the amount of copper applied and the known surface dimensions of the film.

In the burn-out test, a 1.6 mm thick copper clad epoxy glass insulating laminate and a multiple non-copper cladding through 1.0 mm diameter holes was cleaned with an aqueous solution of a basic 7906856 3 - 19 - detergent with a concentration of 45 g / dra in water and a temperature of 50 ° C to remove surface dirt and then washed with water. The copper clad surface was then cleaned with a 10% aqueous solution of sodium persulfate and washed with water. Subsequently, the laminate was successively contacted with 10% sulfuric acid, washed with water and contacted with 30% hydrochloric acid. The walls of the holes were then sensitized for electroless deposition of copper by contacting with a palladium chloride / tin chloride sensitizing solution commercially available at room temperature for 5 minutes. After contacting with the sensitizing solution, the laminate was washed with water and contacted with a 5% by volume fluoroboric acid solution, which also contained 4 g / dm N- (2-hydroxyethyl) -15 ethylenediamine triacetic acid, to remove the excess tin salt and, again, washed with water. The laminate was then dipped in a electroless copper plating solution as defined below for 15-30 minutes to deposit 2-4 micrometers of copper. In particular, the laminate was dipped in a coating solution for 15 minutes in the case of bath A or 30 minutes in the case of bath B and bath C. After coating, washing and drying, the maximum electric current was then bearing capacity of the copper according to the deposit measured using the breakdown test described below. In summary, current is applied across one or more of the copper clad through holes in the laminate at a constant, increasing rate of 3 amps / second, starting from 0, until the maximum current carrying capacity of the conductive copper is in the through holes. At this point, the integrity of the copper in the through holes is destroyed, "" burned out, "and the current value on burning out 7906856 - 20 - is determined by an ammeter. The value of the "burn-out" current corresponds to the copper thickness on the wall of the through holes according to the relationship "burn-out thickness 5 copper thickness * 0.2 x ^ t-dimethyl-

The coating rate is determined in micrometers per hour from the copper thickness and the immersion time. In the examples, "burnout test values are indicated by the designation" BO ". All values, which are not indicated as such in the examples, were obtained using the" gravimetric "technique.

Example I

This example illustrates the use of pyridine, a heterocyclic aromatic nitrogen compound, as a means of increasing the copper plating rate in a bath of the following composition:

Bath A

N.N.N'.N'-tetrakis- (2-hydroxypropyl) - 3 20 ethylenediamine 34 g / dm

CuSO .5H 0 18 g / dm3 ^ ^ 3 3 formaldehyde (37% sol.) 20 cm / dm

RTM

humectant (Pluranic P-85, 3 BASF-Wyandotte Co.] 0.001 g / dm

Sodium hydroxide to the desired pH

3 3

Bath A, to which 0.1 g / dm (100 mg / dm] pyridine was added, was operated at 25 ° C. The effect of the presence of pyridine and its inter-regulation with pH on the copper coating rate is evidenced by the coating speed values in the table and Figure 2. For comparison, the coating speed was also determined for bath A without pyridine and these values are also shown in the table below and in Figure 2.

7906856

Bath A * Bath A + Pyridine pH Coating Rate pH Coating Rate (ym / hr) (ym / hr) - 21 - 12.4 9.5 ** (BO) 12.4 10.7 (BO) 5 13.1 6.3 13 , 1 14.2 **

x comparison test xx peak coating rate Example II

The procedure of Example X was repeated, except that 14.3 g of copper acetate was used instead of CuS0..5H-0 and 3 µg of 0.05 g / dm 2-mercaptopyridine (a heterocyclic aromatic nitrogen compound) instead of the accelerator used. The results are shown in the table below:

X

15 Bath A Bath A + 2-mercaptopyridine pH Coating Rate pH Coating Rate (ym / hr) (ym / hr) 12.4 9.5 (BO) 12.4 12.5 (BD) 12, a 6.7 12.8 14, 0 20 x comparison test

xx peak coating rate Example III

This example illustrates the effect of the combination of two coating speed enhancers of the invention, 2-mercaptobenzothiazole sodium salt and 2-hydroxypyridine, which are heterocyclic aromatic nitrogen compounds. Using these two agents in combination in bath A, the coating procedure of Example I was repeated, and the results are shown in the table below: 7906856-2-2-mercaptothiazole sodium salt (g / dm3) 0 * 0.002 * 0 ** 0 ** 0.002 0.002 2-hydroxypyridine

Cg / dm3]. 0 0 0.001 0.005 0.001 0.005 pH 13.3 13.3 13.0 13.0 .13.3 13.3 coating rate (µm / hour). 5.8 11.7 7.9 11.5 12.3 13.3 '(BO) x control experiment in that no accelerator 10 was used.

xx control experiment in that only one of the two accelerators was present

The combination of 2-hydroxypyridine and 2-mercaptobenzothiazole provided a faster coating rate than either of the two separate compounds, and the copper coating was clear and glossy. When only 2-mercaptobenzothiazole was used, a more stable bath was obtained compared to the control without either compound, but the deposited coating layer was not as clear and glossy as desired. On the other hand, the use of 2-hydroxypyridine only resulted in a copper deposit that was clear and glossy compared to the control bath containing 2-mercaptobenzothiazole or the control bath containing neither compound.

Example IV

The procedure of Example I was repeated, except that p-nitrobenzylamine hydrochloride, an aromatic amine, was used as the coating speed accelerator in bath A, in an amount of 0.1 g / dm. The results 30 are shown in the table below: 7906856 * ï

Bath A * _ Bath A * p-Nitrobenzvlamine-HCl pH Coating Rate pH B Coating Rate (ym / hr) (ym / hr) - 23 - 12.4 9.5 (BO) 12.4 IQ, 5 (BO) 5 12.9 6 , 3 12.9 11.8 CBO)

* comparative test ** peak coating rate Example V

The procedure of Example I was repeated, except that 3 2.2'-dipyridyl, in an amount of 0.005 g / dm, was used as the coating accelerator in bath A. The results are as follows:

Bath A * _ Bath A * 2.2'-dipyridyl pH Coating Rate pH Coating Rate (ym / hr) (ym / hr) 12.4 9.5 CBO) 12.4 10.3 CBO) 12.7 7.0 12.7 11. 0 ** CBO) x comparison test

xx peak coating rate Example VI

This example illustrates the effect of the increase in temperature on the coating rate in the method of the invention.

Using the method of Example I, the coating rate of copper in bath A, which also contained 2-mercapto-benzothiazole, was measured at 26 ° C, 38 ° C and 70 ° C. The results are shown in the table below: 2-mercaptobenzothiazole sodium salt Cg / dm3) 0.002 0.002 0.002 30 pH (measured at room temperature) 13.2 13.2 13.2 temperature C ° C) 25 38 70 coating speed (µm / hour) 13.0 19.3 65 7 CBO)

The copper clad, formed at elevated temperatures, 7906856 * * * 24 - has a reduced internal stress. At 70 ° C, the bath was modified by lowering the formaldehyde concentration from 3 to 12 um / dm. It is to be noted that the fact that the 65 µm / h coating rate obtained with the 70 ° C bath is extraordinary.

It is also noted that a 13.3 µm / h coating rate was obtained in the bath, which was operated at 3S ° C. Example VII

This example illustrates the effect of using a group of VIIII metal in combination with an accelerator for increasing the coating speed of the invention.

The procedure of Example I was repeated using plating baths for electroless deposition of copper of the composition shown in Table C. As can be seen from the data in the table, the presence of a group increases

VlII metal further the coating rate of the copper electroless plating solutions of the present invention.

Running baths in the presence of the additives indicated herein remarkably increases coating rates compared to the control bath. In addition, the additives contained in the solutions of Examples I - VII provide an adhesive copper coating which is substantially free of tension, while the control bath without the additives provided a lesser quality copper coating.

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- 26 -

Example VIII

This example illustrates the use of cytosine, a coating rate accelerator of the invention, to increase the coating rate of copper in a bath of the following composition:

Bath B

tetrasodium ethylenediamine- 3 tetraacetate dihydrate 138 g / dm CUSCL.5H Q 14.7 g / dm3 ^ ^ 3 3 IQ formaldehyde (37% sol. 3 30 cm / dm

NaOH to pH

Using the coating rate determination method described above, a 3 x 5 cm stainless steel foil was catalyzed for an electroless metal deposition and electrolessly coated with copper 3 at 25 ° C in bath B, containing 0.004 g / dm (4 mg / dm °) cytosine was added.

The effect of the presence of cytosine and change in pH on the copper coating rate is shown in the Table and in Figure 3. For comparative purposes, the effect of the change in pH on the copper plating rate in bath B without cytosine is also indicated.

Bath B * Bath B * Cytosine pH Coating Rate pH Coating Rate 25 ym / h ym / h 12.4. 5.3 ** 12.4 9.3 12.75 4.5 12.75 10.4 **

x Control test xx peak coating rate 30 Example IX

The procedure of Example VIII was repeated, except that 2-mercaptobenzothiazole, in an amount of 0.005 g / dm, was used as the coating speed accelerator. The results are shown in the table below: 7906856

X

Bad S_ Bad B + 2-nnercaptobenzothiazole pH Coating rate pH Coating rate

Cym / hour] (ym / hour) - 27 - 12.4 5.3 12.4 11.0 ** 5 13.1 3.5 13.1 7.3

x control test xx peak coating rate Example X.

The procedure of Example VIII was repeated, except that 2-mercaptopyrimidine, in the amount of 0.003 g / dm, was used as the accelerant. The results are shown in Figure 4 and in the table below:

Bath B * _ Bath B + 2-mercaptopyrimidine pH Coating Rate pH Coating Rate

Cym / hr] Cym / hr) 12.4 5.3 ** 12.4 5.3 13.0 3.5 13.0 3.8 ** x control xx peak coating rate.

Example XI

The procedure of Example VIII was repeated, except that guanidine hydrochloride, a non-aromatic nitrogen compound, was used as the coating speed accelerating agent (in an amount of 0.005 g / dm (5 mg / dm)).

25 The results are shown in Figure 5 and in the table below:

Bath B * _ Bath B * guanidine-HCl pH Coating Rate pH Coating Rate

Cym / hr] Cym / hr] 30 12.4 5.3 ** 12.4 8.0 12.72 4.4 12.72 10.5 x Control xx Peak Coating Rate 7906856 * '' * - 28 -

Referring to Examples VIII-XI, it is noted that operating in the presence of the additives results in a marked increase in the coating speed of the solution, compared to the cantral solution, which does not contain additives.

Example XII

This example illustrates a particularly effective composition for practicing the invention and the results to be obtained therefrom: copper sulfate 18 g / dm

Quadrol 37 g / dm RTM 3

Pluronic Ρ-Θ5 C humectant) 1 mg / dm 3 2-mercaptobenzothiazole 1.5 mg / dm

NiS04.6H20 0.61 g / dm3 15 Rochelle salt 1.0 g / dm3 3 3 formaldehyde 12.0 cm / dm

NaOH 37.0 g / dm3 3 4-hydroxypyridine 40.0 mg / dm pH 13.15 [measured at 25 ° C]

temperature 70 ° C

speed 32 µm / hour ductility 2 bends bath stability very good It is noted that in addition to a higher speed the bath according to example XII provides copper with a high ductility.

Example XIII

This example further illustrates the coating rate 30 that can be achieved according to the invention: 3 copper sulfate 18 g / dm

Quadrol 34 g / dm 3 3 formaldehyde 15 cm / dm 7906856 3 * * - 29 - RTM 3

Pluronic P-85 (wetting agent) 1 mg / dm 2-mercaptobenzothiazole 1.5 mg / dm pH 13.2 3 4-hydroxypyridine 40 mg / dm 3 5 polyoxy-coagulant 1 mg / dm rate 72 ym / h

temperature 70 ° C

Example XIV

This example illustrates the invention using a highly concentrated solution. With such a highly concentrated bath, the need for frequent batch or continuous replacement is reduced or eliminated.

Bath C.

N .N .N '. N'-tetrakis-C2-hydroxypropyl] - 3 15 ethylenediamine 65.4 g / dm (0.22 mol / dm3l

CuSCL.5H 0 50 g / dm3 (0.20 mol / dm3] ^ ^ 3 3 3 formaldehyde (37% sol.) 20 cm / dm (0.28 mol / dm]

RTM

humectant (Pluronic P-85, 20 BASF-Wyandotte Co.] 0.001 g / dm3 3 3 sodium hydroxide 3.9 g / dm (9.1 mol / dm] pH 13.2

temperature 25 ° C

In Example XIV, the coating speed gravimetric test was performed using a copper plate instead of a stainless steel plate. For comparison, a dilute bath A according to Example I was used, using the same type of copper plates as deposition substrate. The results are shown below: 3 30 Bad Cytosine (mg / dm) Coating Rate (ym / h) A 0 3.6 C 0 4.0 C 5 7.9 7906856 * * - 30 - C 10 9.8 C 15 10 , C 20 11.3 C 40 9.1 5 Given the concentration of the coating solution, the coating rates obtained with the cytosine were surprising These rates obtained in this example illustrate the effectiveness of the present process in highly concentrated coating solutions, prior art has previously required dilute solutions 3, eg solutions containing less than 0.1 mol / dm copper salt 3 and usually about 0.06 mol / dm. Copper electroless deposition solutions may be used at a concentration of greater than 0.1 moles of copper-15 salt to provide coating rates greater than 7 microns / hour A comparison of bath A with bath C also shows, that in these baths without the presence of cytosine increasing the copper concentration in the bath C18 3 3 g / dm CuSO 2. St 2 O in bath A against 50 g / dm of the same salt in 20 bath C) has no significant effect on the coating rate.

Rather, it is the presence of the cytosine, as well as the control of the pH, which results in the increase of the coating rate.

In addition to the above embodiments, reference is made to copper electroless deposition methods of the invention, wherein the accelerator is 2-mer captobenzothiazole in combination with imidazole or 4-hydroxypyridine, leading to clear copper deposits in compared to those cases where no accelerant or 2-mercapto-30 benzothiazole was used alone, and methods where the accelerant consists of pyridine in combination with 2-mer captobenzothiazole, leading to stability improvements compared to pyridine alone, as well as brighter 790 6 8 56 - 31 - Copper deposits compared to 2-mercaptobenzothia sole alone.

Particularly advantageously, the coating rate accelerating agent is selected from 2-mercaptobenzothiazole, 4-hydroxy-5-pyridine, 2-mercaptopyridine, aminopyrazine, pyrido (2.3.b) pyrazine, cytosine, guanidine hydrochloride, pyridine, 2-hydro-xypyridine , para-nitrobenzylamine hydrochloride, imidazole and mixtures thereof.

Due to the high rate of copper deposition from the solutions prepared according to the invention, frequent replenishment may be necessary when using dilute solutions. Surprisingly, it is possible to practice the invention using highly concentrated coating solutions. See e.g. example XIV.

Generally, as the depolarizing agent, any agent may be used which, when added to the solution, is at least a 20% and preferably at least a 30% depolarization of the anodic partial reaction or the cathodic partial reaction of the solution, or both, provided.

To illustrate the use of the invention in the manufacture of printed circuits, for the electroless metal deposition, a copper clad epoxy glass laminate is pierced to provide a plurality of through holes. The surface and holes were cleaned with a basic cleaning solution at a concentration of 45 g / dm and a temperature of 50 ° C, and then washed with water. The copper-coated surface was then cleaned with a 10% aqueous solution of sodium persulfate and the surface rinsed with water. The laminate was successively contacted with 10% sulfuric acid, washed with water and contacted with 30% hydrochloric acid.

After pretreatment, the non-copper clad holes were catalyzed for electroless deposition in a standard manner using a palladium / tin salt catalyst, 7906856 - 32 - washed briefly with water, treated with a 5% fluoroboric acid solution to remove excess tin salt, and washed again with water · The epoxy glass laminate was now ready for treatment by the method of the invention.

The catalyzed epoxy glass laminate was dipped in a plating bath for electroless deposition of copper (any bath as described above) for depositing 2-4 micrometers of copper.

After an initial deposition of copper, e.g. 2-4 microns, portions of the copper plating were covered with

RTM

a masking material, e.g. Riston 310, a dry film photo reserve, which is commercially available, copper was applied to the unmasked surfaces by a conventional electrocoating process, after which electroplating applied a tin-15 lead alloy (an etching reserve). The mask was stripped off using a mild base, e.g. 4-15% solution of NaOH, and the background copper in the previously masked areas was etched away, e.g. using ammonia-free CuC2. The product was an epoxy glass laminate with a pattern of copper conductors on the surface, and copper interconnects in the through holes, all coated with tin-lead.

t 7906856

Claims (20)

2. Process according to claim 1, characterized in that the agent effects at least a 20% depolarization of the anodic partial reaction of the solution. A method according to claim 1, characterized in that the agent processes at least a 20% depolarization of the cathodic partial reaction of the solution. 4. A method according to claim 1, characterized in that the presence of the agents effects at least a 20% depolarization of both the anodic and the cathodic partial reaction of the solution. 5. A method according to claim 1, characterized in that an adhesive, non-stressing deposit of copper can be obtained from a coating bath for electroless deposition of Copper containing copper ions, a copper ion complexing agent, a reducing agent and a pH adjuster and developing a coating rate which increases first and passes a peak coating rate and then decreases as a function of the pH above 10, characterized in that 790 6 8 56 - 34 - CA) in the electroless coating solution deposition of copper an accelerator is included which contains a de-localized p 1 bond selected from Ca) heterocyclic aromatic nitrogen and sulfur compounds; Cb) non-aromatic nitrogen compounds with at least one delocalized pi bond, Cc) aromatic amines, and Cd) mixtures of the above compounds, and 10 CB) the electroless copper plating solution operates in the presence of the accelerant at a pH greater than the peak coating rate pH of the solution without the agent present, to deposit electroless copper at a rate greater than the coating rate of the solution, without the agent and at the same pH and same temperature, 6. Process according to claims 1 to 5, characterized in that the accelerating agent is selected from 2-mercaptobenzothia sole, 4-hydroxypyridine, 2-mercaptopyridine, aminopyrazine, pyidoC2.3.b) pyrazine, cytosine, guanidine. hydrochloride, pyridine, 2-hydroxypyridine, para-nitrobenzylamine hydrochloride, imidazole and mixtures thereof. A method according to claim 5, characterized in that the accelerating agent is present in an amount of at least 3 0.0001 g / dm of the electroless metal coating solution. A method according to claim 5, characterized in that the accelerating agent is present in an amount of up to about 2.5 g / dm. A method according to claims 1-8, characterized in that the accelerating agent contains a free electron pair on the nitrogen atom adjacent to a pi bond. Method according to claims 1-9, characterized in that 7906856 A - 35 - contains the electroless metal deposition coating solution of at least one metal selected from group VIII of the Periodic Table of Elements. A method according to claim 10, characterized in that the 5 metal ions are present in an amount of about 0.005 to 30% by weight, based on the weight of the copper salt. 12. Process according to claims 1-11, characterized in that the reducing agent is selected from formaldehyde and precursors or derivatives thereof, boranes, borohydrides, hydroxylamines, hydrazines and hypophosphite. Process according to claims 1-11, characterized in that the pH-adjusting agent is an alkali metal hydroxide or an alkaline earth metal hydroxide. Coating solution for electroless deposition of copper containing copper ions, a copper ion complexing agent, a reducing agent and at least one depolarizing agent and a pH adjusting agent for maintaining such a solution above pH 11, characterized by a coating rate of at least 7 micrometers / hour and higher than the coating rate of the solution without the depolarizing agent. Copper electroless plating solution according to claim 14, characterized in that the solution contains a depolarizing agent containing a delocalized pi bond and selected from Ca} heterocyclic aromatic nitrogen and sulfur compounds Cb) non-aroratic nitrogen compounds with at least one delocalized pi bond Cc} aromatic amines and Cd} mixtures of the above compounds. 30 1B. Coating solution for electroless deposition of copper according to claims 13 to 14, characterized in that they can electroless form an adhesive copper coating at room temperature at a rate of at least 9 micrometers / hour. 7306856 ♦ Ί - 36 - Solution according to claim 16, characterized in that the depolarizing agent increases the anodic partial reaction of the solution by at least 20%. Solution according to claim 16, characterized in that the depolarizing agent increases the cathodic partial reaction of the solution by at least 20%. Solution according to claim 16, characterized in that the depolarizing agent increases both the cathodic and anodic partial reaction of the solutions by at least 20%. Coating solution for electroless deposition of Ko per according to claim 14 with a pH above 10 and a concentration 3 of Copper salt above 0.1 mol / dm, Copper-coated substrates obtained using a coating solution according to claims 14-20. 7906856