CA1225501A - Aqueous electroless nickel plating bath and process - Google Patents
Aqueous electroless nickel plating bath and processInfo
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- CA1225501A CA1225501A CA000458433A CA458433A CA1225501A CA 1225501 A CA1225501 A CA 1225501A CA 000458433 A CA000458433 A CA 000458433A CA 458433 A CA458433 A CA 458433A CA 1225501 A CA1225501 A CA 1225501A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
- C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
- C23C18/36—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents using hypophosphites
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- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Materials Engineering (AREA)
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- Organic Chemistry (AREA)
- Chemically Coating (AREA)
- Electroplating And Plating Baths Therefor (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An improved aqueous electroless nickel plating bath and process for chemically depositing nickel on a substrate comprising an aqueous solution containing nickel ions, hypophosphite ions, a complexing agent, preferably a buffering agent and a wetting agent, and a small but effective amount of a sulfonium betaine compound sufficient to control the rate of nickel deposition and the concentration of phosphorus in the nickel deposit, preferably, in further combination with supplemental organic and/or inorganic rate stabilizers. The invention further contemplates a process for rejuvenating an electroless nickel bath which has been rendered inoperative due to the presence of excessive concentrations of supplemental stabilizing agents by the addition of a controlled effective amount of a sulfonium betaine compound sufficient to restore the bath to an operative plating condition.
An improved aqueous electroless nickel plating bath and process for chemically depositing nickel on a substrate comprising an aqueous solution containing nickel ions, hypophosphite ions, a complexing agent, preferably a buffering agent and a wetting agent, and a small but effective amount of a sulfonium betaine compound sufficient to control the rate of nickel deposition and the concentration of phosphorus in the nickel deposit, preferably, in further combination with supplemental organic and/or inorganic rate stabilizers. The invention further contemplates a process for rejuvenating an electroless nickel bath which has been rendered inoperative due to the presence of excessive concentrations of supplemental stabilizing agents by the addition of a controlled effective amount of a sulfonium betaine compound sufficient to restore the bath to an operative plating condition.
Description
"` ~22S501 Back~round of the Invention The present invention broadly relates to the autocatalytic chemical deposition o~ nickel, and more particularly, to an improved aqueous electroless nicXel plating bath and process for depositing nickel on a sub-strate.
A variety of nickel containing aqueous solu-tions have heretofore been used or proposed for use for chemically depositing nickel on a substrate incorporating various additive components for controlling the rate of nickel deposition and for promoting stability of the bath after prolonged usage. Among such compositions are those such as disclosed in United States Patents No. 2,762,723;
A variety of nickel containing aqueous solu-tions have heretofore been used or proposed for use for chemically depositing nickel on a substrate incorporating various additive components for controlling the rate of nickel deposition and for promoting stability of the bath after prolonged usage. Among such compositions are those such as disclosed in United States Patents No. 2,762,723;
2,822,293, and 3,489,576. In addition to a controlled concentration of nickel ions, such prior art electroless nickel plating baths conventionally employ hypophosphite anions for reducing the nickel cation to the metallic state and the hypophosphite anions are in turn oxidized to phosphite anions and other deg~adation products some of which combine with other nickel ions present in the solu-tion forming a finely particulated dispersion producing a random chemical reduction of the other nickel ions present - in the bath cau~ing the resultant nickel deposit on the substrate to become progressively coarse, rough and some-times porous. The presence of such .I`
~ ~225501 fine-sized dispersed particulate matter also promotes instability of the chemical balance of the bath ultimately resulting in a deoompositian thereof ne oe ssitating discarding the bath and repla ~.e~.t.
For these and other reasons, various additive agents as described in the aforementioned United States patents have heretofore been employed or proposed for use to stabilize the bath and to further oontrol the rate of nickel deposition on a substrate being plated. In such electroless nickel plating baths emplc~ing hypcphosphite ions as the reducing agent, the nickel deposit actually ccmprises an alloy of nickel and phosphorus with the phosphorus content usually ranging from about 2 to about 15 percent by weight. The physical and chemical prcperties of such nickel-phosphorus alloy deposits are related to the percentage of the phosphorus present and in turn, the percentage of phosphorus in the deposit is influenced by a number of factors including the bath operating temperature, the operating pH, the hypophosphite ion conoentration, the nickel ion concentration, the phosphite ion and hypophosphite degradation product concentration as well as the total chemical composition of the bath including additive agents.
In end uses of electroless nickel plated articles, those applications requiring maximum deposit hardness or nickel deposits which are nonmagnetic, it is normally necessary to provide nickel alloy deposits with a relatively high peroentage of phosphorus such as 9 percent by weight or greater. However, there are numerous other applications for electroless nickel-phosphorus alloys in which a lower percentage of phosphorus is desirable and i2:~55(1 1 an Aerospace Material Specification, P~IS2405A provides for nickel-phosphorus alloy deposits in which the phosphorus content is to be held to a minimum and, in any event, shall not exceed 8 percent by weight.
Prior art compositions and processes for producing nickel-phosphorus alloy deposits having low percentages of phosphorus have been found susceptible to producing bath instability, a shortening of the operating life of the kath and/or have caused increased difficulty to control the bath because of the relatively narrcw concentration ranges of some of the bath constituents. For example, the addition of thiourea to an electroless nickel bath has been found effective to reduce the phosphorus content in the resultant nickel deposit. Hcwever, at a concentration of between 2.5 and 3 parts per million t33 to 40 micro mol per liter), thiourea causes such bath formulations to cease plating. It has been reported that the critical narrow concentration limits of thiourea in an electroless nickel plating bath to provide satisfactory operation renders this additive agent impractical for commercial plating installations because analysis and replenishment of such baths to maintain proper co~position parameters is difficult, time consuming and cost intensive.
Alternative sulfur-containing organic additive agents have been praposed for stabilizing and/or increasing the deposition rate of nickel from electroless nickel plating baths such as described in United States Patents Nos. 2,762,723 and
~ ~225501 fine-sized dispersed particulate matter also promotes instability of the chemical balance of the bath ultimately resulting in a deoompositian thereof ne oe ssitating discarding the bath and repla ~.e~.t.
For these and other reasons, various additive agents as described in the aforementioned United States patents have heretofore been employed or proposed for use to stabilize the bath and to further oontrol the rate of nickel deposition on a substrate being plated. In such electroless nickel plating baths emplc~ing hypcphosphite ions as the reducing agent, the nickel deposit actually ccmprises an alloy of nickel and phosphorus with the phosphorus content usually ranging from about 2 to about 15 percent by weight. The physical and chemical prcperties of such nickel-phosphorus alloy deposits are related to the percentage of the phosphorus present and in turn, the percentage of phosphorus in the deposit is influenced by a number of factors including the bath operating temperature, the operating pH, the hypophosphite ion conoentration, the nickel ion concentration, the phosphite ion and hypophosphite degradation product concentration as well as the total chemical composition of the bath including additive agents.
In end uses of electroless nickel plated articles, those applications requiring maximum deposit hardness or nickel deposits which are nonmagnetic, it is normally necessary to provide nickel alloy deposits with a relatively high peroentage of phosphorus such as 9 percent by weight or greater. However, there are numerous other applications for electroless nickel-phosphorus alloys in which a lower percentage of phosphorus is desirable and i2:~55(1 1 an Aerospace Material Specification, P~IS2405A provides for nickel-phosphorus alloy deposits in which the phosphorus content is to be held to a minimum and, in any event, shall not exceed 8 percent by weight.
Prior art compositions and processes for producing nickel-phosphorus alloy deposits having low percentages of phosphorus have been found susceptible to producing bath instability, a shortening of the operating life of the kath and/or have caused increased difficulty to control the bath because of the relatively narrcw concentration ranges of some of the bath constituents. For example, the addition of thiourea to an electroless nickel bath has been found effective to reduce the phosphorus content in the resultant nickel deposit. Hcwever, at a concentration of between 2.5 and 3 parts per million t33 to 40 micro mol per liter), thiourea causes such bath formulations to cease plating. It has been reported that the critical narrow concentration limits of thiourea in an electroless nickel plating bath to provide satisfactory operation renders this additive agent impractical for commercial plating installations because analysis and replenishment of such baths to maintain proper co~position parameters is difficult, time consuming and cost intensive.
Alternative sulfur-containing organic additive agents have been praposed for stabilizing and/or increasing the deposition rate of nickel from electroless nickel plating baths such as described in United States Patents Nos. 2,762,723 and
3,489,576. Such alternative additive materials have also been found oommercially impractical because of a very narrow useful 122550~
concentration range and moreover, many of such sulfur-containing organic compounds do not produce a nickel-phosphorus alloy deposit in which the phosphorus content is belcw about 8 percent by weight.
Prior art compositions and processes for pro*ucing nickel-phosphorus alloy deposits of relatively high phosphorus contents have also been subject to the disadvantages of requiring relatively rigid control of the concentration of the bath constituents detracting from the ease of control, maintenance and replenishment of such baths to maintain optimum operating performance. The use of stabilizing agents for prcviding increased bath stability has occasioned in prior art compositions a condition of over stabilization whereby a cessation of plating occurs. In such instan oe s, it has been necessary to discard the bath and prepare a new operating bath which constitutes a costly and tinE-consuming operation.
me present invention provides for an improved electroless nickel plating bath and process for depositing a nickel-phosphorus alloy of relatively low phosphorus oontent incorporating an additive agent which can satisfactorily be employed over a relatively broad cperating concentration range while at the same time increasing the rate of deposition of the nickel by as much as 30 percent or mDre. The present invention ~urther provides for an improved electroless nickel plating bath and process suitable for use in depositing nickel-phosphorus platings of relatively high phosphorus content providing for greater latitude in variations in the bath constituents thereby achieving simpler oontrol and facilitating maintenan oe and repl d shment of the bath. The present invention further contempLates a method for rej wenating or resboring an electroless nickel plating bath which has been rendered inoperative due to o~er stabilization thereof by inclusion of organic and/or inorganic stabilizi~g agents in excessive amounts by the addition of an additive agent of the present invention wherehy satisfactory operation of the bath is restored.
Summary of the Invention The benefits and advantages of the present invention are achieved in acoordan oe with the composition aspects thereof by an acueous electroless nickel plating bath oontaining nickel ions, hypcphosphite ions, and an, am~unt of a sulfonium betaine ccmpaund sufficient to control the rate of nickel deposition and the con oe ntration of phosphorus in the nickel deposit. m e sulfonium betaine compound corresponds to the structural formula:
,,, Rl~
C-S-(CHR)--S03e Wherein:
P~ and R4 are the sa~e or different and are H, Cl-C6 alkyl radicals, Cl-C6 hydroxy alkyl radicals, R is the same or different and is H or aH, and - n is an integer of f.~l 1 to S, as well as mixtures thereof.
~2~55~1 m e oonoentration of nickel ions generally ranges from abcut 1 to about 15 grams per liter (g/l), the h~xqphosphite ions range from about 2 to a~out 40 g/l and the sulfonium betaLne cc~pound can range from about 1 up to about 200 micro mol per liter. The bath in order to prc~ide satisfactory prolonged commercial operation further incorporates a cc~plexing agent usually present in an amount up to about 200 g/l for ccmplexing the nickel ions present as well as to solubilize the hypophosphite degradation products formed during prolonged usage of the bath. The electroless bath desirably further contains a buffering agent generally present in amounts up to about 30 g/l, a wetting agent to minimize surfa oe pitting, usually present in an amount up to a~out 1 g/l and hydrogen or hydroxyl ions to provide a bath on the acid or aIkaline side as may be desired. Optionally, but preferably, the bath further ~ ~loys in combination with the sulfonium betaine compound at least one supplemental organic or inorganic stabilizer agent of the various types heretofore known which can be employed in amounts up to that level at which the rate of deposition of nickel is undesirably impaired.
In accordance with the process aspects of the present invention, a low phosphorus-nickel alloy is deposited on a metallic or non~metallic substrate by contacting the cleaned and suitably prepared substrate with the electroless nickel bath at a temperature generally ranging from about 40C up to boiling for a period of as little as 1 minute up to several hours or even days to prcvide a nickel-phosphorus alloy deposit of the desired thickness. During the deposition process, agitation of the bath ., ~2SS~l is preferred, emplcying mild air or other forms of mechanical agitation. The bath is also preferably subjec~ed to periodic or continuous filtration to re~ove solid contamunants. The bath is periodically and/or oontinuously replenished for maintaining the bath constituents within the desirable operating concentrations and at the appropriate pH level.
The present invention further contemplates a process for effecting rejuvenati~n of an electroless nickel bath which has been rendered inoperative due to an over stabilization thereof by organic and/or inorganic stabilizing agents by the addition of a controlled effective amDunt of a sulfonium betaine compound to restore operation the.reof.
Additional benefits and advantages of the present invention will be~a.~ apparent upon a reading of the Description of the Preferred Embodiments taken in conjunction with the accompanying examples.
.
Description of the Preferred Embodiments The aqueous electroless nickel plating baths of the present invention can be cperated over a broad pH range including the acid side and the aLkaline side at a pH of from about 4 up to about 10. For an a~idic bath, the pH can generally range from about 4 up to abcut 7 with a pH of about 4.3 to about 5.2 being preferred. For an aLkaline bath, the pH can range from about 7 up to about 10 with a pH range of from about 8 to about 9 being preferred. Since the bath has a tendency to become more acidic during its operation due to the formation of hydrcgen ions, the pH
~ 12Z55(~1 is periodically or continuously adjusted by addinq bath soluble and oo~patible aIkal~le substances such as alkali metal and ammonium hydroxides, carbonates and bicarbonates. Stability of the cperating pH is also provided by the addition of various buffer compounds such as acetic acid, propionic acid, boric acid or the like in amounts up to about 30 g/l with amounts of about 4 to about 12 g/l being typical.
The nickel ions are introduced into the bath employing various bath soluble and compatihle nickel salts such as nickel sulfate hexahydrate, nickel chloride, nickel acetate, and the like to provide an operating nickel ion concentration ranging from about 1 up to about 15 g/l with concentrations of from about 3 to about 9 g/l being preferred and with a concentration of about 5 to about 8 g/l being opti~num. The hypophosphite reducing ions are introduced by hypophosphorous acid, sodium or potassium hypophosphite, as well as other bath soluble and compatible salts thereof to provide a hypophosphite ion concentration of about 2 up to about 40 g/l, preferably c~bout 12 to 25 g/l with a con oe ntration of cibout 15 to about 20 g/l being optimum. The specific concentration of the nickel ions and hypophosphite ions employed will vary within the aforementioned ranges depending upon the relative concentration of these two constituents in the bath, the particular operating conditions of the bath and the types and concentrations of other bath components present.
In order to provide a commercially satisfactory plating bath of reasonable longevity and operating performance, it is conventional preferred practice to incorporate a complexing agent .` 1~2SSOl or mixture of oomplexing agents in amDunts sufficient to ~ul~lex the nickel ions present in the bath and to further solubilize the hypophcsphite degradation products formed during usage ~of the bath. The oomplexing of the nickel ions present in the bath retards the formation of nickel orthc~hosphite which is of relatively low solubility and tends to form insoluble suspensoids which not only act as catalytic nuclei promoting bath decomposition but also result in the formation of coarse or rough undesirable nickel deposits. Generally, the cc~plexing agents are employed in amounts up to about 200 g/l with amounts of about 15 to about 75 g/l being preferred while amDunts of about 20 to abcut 40 g/l are typical. Complexing or chelating agents of the various types described in the aforementioned United States patents, the teachings of which are incorporated herein by reference, can be satisfactorily employed for this purpose and the particular selection of such c~nplexing agent or nNLYture of complexing agents will be dependent to some extent on the operating bath pH to prc~ide complexors of maximum stability under such specific pH
conditions. Typical of such cc~plexing agents are the acid as well as aIkali metal and anmDnium salts of glycolic acid, lactic acid, malic acid, glycine, citric acid, acetic acid, tartaric acid, succinic acid, and the like. While aIkaline earth metal salts can also be employed to some extent, the tendency of such alkaline earth metals to fonm insoluble precipitates with the bath constituents renders them less desirable and for this reason are preferably excluded. It will also be appreciated, that certain complexing agents such as acetic acid, for example, also act as a "-` 12Z~5~31 buffering agent and the appropriate concentration of such additive oomponents can be cptimized for any bath oomposition in consideration of their dual-functioning properties.
In a~ition to the foregoing constituents, the bath further includes as an essential constituent, a plating rate and phosphorus controlling agent present in an amcunt effective to enhan oe the rate of deposition of the nickel-phosphorus allcy and to provide an alloy deposit generally containing less than ab~ut 8 per oe nt by weight phosphorus. Ihe additive agent comprises a sul.onium betaine oompound corresponding to tke structural formLla:
Rl~
~3~C-S- (CHR)--S03e R?N
~herein:
P~, R2, ~ and R4 are the same or different and are H, Cl-C6 alkyl radicals, Cl-C6 hydroxy al~yl radicals, R is the same or different and is H or OH, and n is an integer of fro~ 1 to 5, as well as mixtures thereof.
A sulfonium betaine ocmpound oorresponding to the foregoing structural formula which has ~een found particularly satisfactory comprises 3-S-isokhiuronium propane sulfonate. Ihis ~,yound corresponds to tke foregoing structural formula in which `-` lZZ5501 Rl, R2~ R3 and R4 are hydrogen and n is 3. Alternative satisfactory ~sulfonium betaine compounds which can be emplc~d include N,N'-dimethyl-3-S-isothiuronium propane sulfonate, N,N'-diethyl-3-S-isothiuronium propane sulfonate, N,N'-di~ydroxymethyl-3-S-isothiuronium propane sulfonate, N,N'-diisopropy1-3-S-isothiuronium propane sulfonate, N,N,N',N'-tetramethyl-3-S-isothiuronium propane sulfonate, N,N,N'-trimethyl-3-S-isothiuronium propane sulfonate, 2-S-isothiuronium ethane sulfonate, 3-S-isothiuronium propane-2-ol sulfonate and the like. These additive compounds are extremely effective even in relatively l~ow concentrations such as about 1 micro mol per liter to oon oe ntrations as high as about 200 micro mol per liter. The foregoing broad range of operating concentrations provides for a substantial simplification of analysis and control of the operating bath under c~~ rcial operating conditions providing significant advantages over prior art additiv~ ccmpounds of the types heretofore kncwn. The sulfonium betaine oompound in accordance with a preferred practice is employed in acidic baths at a concertration of about 10 to about 150 micro mol per liter with a concentration of about 20 to about 120 micro mDl per liter being typical. In aLkaline baths, the sulfonium betaine compound is preferably employed at a con oe ntration of about 1 to about 50 micro mol per liter with a concentration of about 2 to about 25 micro mol per liter being typical.
In accordance with a further preferred practice of the present invention, the sulfonium betaine compound is e~ployed in .
;50~
combination with other conventional inorganic and/or organic stabilizing agents of the types heretofore kncwn including lead ions, cadmlum ions, tin ions, bi~muth ions, antim~ny ions and zinc ions which can conveniently be introduced in the fonm of bath soluble and compatible salts including halides, acetates, sulfates, and the like. Plternatively, otner stabilizing agents can be employed including cyanide ions, thiocyanate ions, and the like which typically can be used in amounts of from about 1 up to about 20 p~m. Lead ions can be employed in amounts usually up to about 2 ppm; cadmium ions in an amount up to about 10 ppm;
antimony and tin ions can be employed in an amount up to about 100 ppm. m e specific concentration of such supplemental stabilizing agent or mixtures of supplemental stabilizing agents is limited by such con oe ntrations at which the rate of nickel deposition is inhibited to an undesirable magnitude rendering the bath commercially impractical.
The bath may additionally employ one or a mixture of suitable wetting agents of any of the various types heretofore known which are soluble and compatible with the other bath aonstituents. The use of such wetting agents is desirable to prevent pitting of the nickel alloy deposit and can usually be employed in amounts up to about 1 g/l.
In acaordance with the pro oe ss aspects of the present invention,-a substrate to be plated is contacted with the bath solutian at a temperature of at least about 40C up to boiling.
Electroless nickel baths of an acidic type are preferably employed at a temperature of from about 70 to about 95C with a temperature " ~ZZ55C~:l of about 80 to a~out 90C bein~ optimum. Electroless nickel baths on the alkaline side are generally operated within the broad operating range but at a correspondingly lower temperature than the acid-type bath sin oe pH and bath temperature are inte..~lated in that the rate of nic~el deposition increases as the pH
increases but the stability of the bath increases as the pH of the bath decreases while the rate of deposition of nickel increases as the temperature increases but with a corresponding decrease in bath stability.
me duration of contact of the electroless nickel solution with a substrate being plated is a function dependent entirely on the desired thickness of the nickel-phosphorus alloy desired. Typically, the contact time can range frcm as little as about 1 minute to several hours or even several days.
Conventionally, a plating deposit of about 0.2 up to about 1.5 mils is a normal thickness for many commercial applications. When wear resistance is desired, such deposits can be applied at a thickness of about 3 to about 5 mils such as on valves, pipes, dies and the like. m icknesses of up to about 0.25 inch can also be achieved by a correspondingly longer contact time as may be desired.
During the deposition of the nickel alloy plate, it is preferred to employ mild agitation such as mild air agitation, mechanical agitation, bath circulation by pumping, as well as by bar~el plating in which the rotation of the immersed barrel imparts agitation to the batn. It is also preferred to subject the bath to a periodic or continuous filtration treatment to ~ZZS5~1 . ,~
reduce the level of contam~nants therein. Replenishment of the constituents in the bath is also performed on a periodic or continuous basis to maintain the con oe ntration, particularly of the nickel icns, hypaphosphite ions, and p~ level within the desired limits.
The substrate to be plated is subjected to a prellminary surfa oe preparation in accordan oe with oonventional practioe to provide a clean and catalytically active surface. In the case of substrates which Q nnot be directly coated employ mg the electroless nickel bath because of their non-catalytic nature relative to the chemistry of the bath, the substrates can be preliminarily subjected to an electrolytic plating of nickel or such other metal which is catalytic whereby the substrate surfa oe is re oe ptive or made receptive to chemical deposition of nickel fron the electroless bath.
In acc~rdan oe with a further process aspect of the present invention, electroless nickel plating baths which have been rendered inoperative for depositing a nickel-phosphorus alloy deposit on a substrate due to the use of an excessive amount of inorganic and/or organic stabilizing agents, can be restored to effective operation by the addition thereto of a sulfonium betaine ccr~x~m d as hereinbefore defined as ~ell as mixtures thereof in an amount effective to restore satisfactory operation. The concentration of the sulfonium betaine compound employed for effec,ting rejuvenation can range within the limits as hereinbefore specified with ooncentrations of from about 20 to about 120 micro mol per liter being typical for acidic-type baths and with .~
-, ~Z25SOl con oe ntrations of about 2 to about 25 micro mol pPr liter being typical for alkaline-type baths. m e sulfonium betaine oompound is added bo the bath in the presen oe of agitation to effect a substantially unifonm distribution thereof.
In order to further illustrate the present invention, the following examples are p m vided. It will be understood that the examples are provided for illustrative purposes and are not intended bo be lLmdting of the soope of the present Lnvention as herein described and as set forth in the subjoined claims.
E~MPLE 1 Three 500 milliliter electroless nickel plating baths were prepared oontaining 27 g/l of nickel sulfate hexahydrate (equivalent to 6 g/l nickel ions); 24 g/l of sodium hypophosphite mDnohydrate (equivalent to 14.7 g/l hypophosphite ions); 14 g/l malic acid; 9 g/l a oe t~c acid; and the pH of each bath was adjusted to about 5 using ammonium hydroxide. A separate stabilizing agent of the types heretofore employed was added to each bath in acoordan oe with the tabulation as set forth in Table 1.
~E 1 Rate of Depo- Percent P
Stabilizer Gonc., mq/l sition, mil/hr. in Deposit Lead ions 0.5 0.68 9.4 Thicurea 3.0 1.1 6.2 ` T ~ roprionic 3.0 1.3 9.6 Acid ~2Z5501 The lead ion oon oe ntration as set forth in Table 1 is equivalent to 2.4 micro mols/l; the ooncentration of the thiourea stabilizer is equivalent to 39.4 micro mDls/l; the con oe ntration oS the thiodiproprionic acid stabilizer is equivalent to 16.8 micro mDls/l.
The temperature of each sample plating bath was adjusted to about 88 to about 90C. Cleaned stainless steel panels (39 cm2 area) were immersed in each bath and were prelLminarily electroplated for 30 seconds while cathodically charged to initiate chemical deposition on the stainless steel. Thereafter, electroless deposition of the nickel-phosphorus alloy was oontinued for a total of 60 minutes. The resultant nickel-phosphorus alloy deposits were separated from the stainless steel substrates and the foils were measured for thickness and were analyzed for phosphorus content. The rate of deposition in terms of mils per hour and the percentage phosphorus in the nickel alloy deposit are set forth in Table 1, The data as set forth in Table 1 clearly demonstrates that both thiourea and thiodiproprionic acid are effective in increasing the rate of deposition of the nickel alloy deposit in co~earison to the bath sample in which lead ions are the only stabilizer. However, while both thiourea and thiodiproprionic acid are thio compounds, only the thiourea stabilizer lowers the percentage of phosphorus in the nickel alloy deposit. The phosphorus content in the nickel alloy deposit when employing lead ions or thiodiproprionic acid stabilizers is in exoe ss of 9 percent by weight.
';
lZ2S501 A series of 500 milliliter electroless nichel plating baths was prepared containing 27 g/l nickel sulfate hexahydrate;
30 g/l sodium hypophosphite monohydrate (equivalent to 18.4 g/l hypcphosphite ions); 26 g/l lactic acid; 9 g/l acetic acid; and the pH was adiusted to about 4.9 employing amm~nium hydroxide. Tb each bath sample a controlled amLunt of a thiourea stabilizing agent or a sulfonium ~etaine compound oo~prising 3-S-isothiuronium propane sulfonate was added in accordance with the concentrations as set forth in Table 2. One sample bath was devoid of any stabilizing agent to serve as a control.
~AELE 2 Con oe ntration, Rate of Depo- Percent P
Stabilizermicromols/l sition, mil/hr. in Deposit None - 0.80 ~ 9.90 m iourea 13.1 1.00 6.67 m iourea 26.3 1.25 6.76 Thiourea 39.4 1.10 6.83 Thiourea 52.6 1.02 6.49 m iourea 65.7 1.03 6.46 Thiourea 78.9 zero 3-S-iso- 6.3 1.10 8.22 thiuronium propane 31.6 1.10 7.36 sulfonate " 63.2 1.23 6.36 94 9 ~.00 6.29 " 110.7 1.12 5.95 " 126.5 1.02 5.42 n 142.4 1.05 5.34 " 158.2 zero Cleaned stainless steel test panels were plated in accordan oe with the procedure descri~ed in Example 1 employing a bath operating temperature of about 88 to about 90C for a period of 60 minutes following an initial 30 second electrolytic deposition on each test panel to initiate deposition. The ~ lZZ55(~1 resulting nickel-phosphorus alloy deposit produced from each bath sample was remcved as a foil from the test panel and the foils were measured with a dial micrometer to determine the deposition rate and were also analyzed for the percentage of phosphorus in the deposit. The results are also set forth in Table 2.
As will be apparent from the data set forth in Table 2, both the thiourea stabilizing agent and the sulfonium betaine compound additiv~ provide an increase in the rate of deposition of the nickel-phosphorus deposit in oomparison to the same bath devoid of any stabilizing additive agent. Hbwever, it will be noted that the useful operating range of the sulfonium betaine compourd is m~re than twice that of the thiourea stabilizing agent providing for substantial simplicity in the maintenance and control of the plating bath during commercial operation.
Furthermore, the percentage of phosphorus in the deposit obtained from the baths employing the sulfonium betaine compound in a~rdance with the practi oe of the present invention attains a value of m~re than 17 percent less than that obtained employing the thiourea stabilizing agent.
A six liter electroless nickel plating bath was prepared oontaining 27 g/l nickel sulfate hexahydrate; 30 g/l sodium hypophosphite monohydrate; 35 g/l lactic acid; 1.5 g/l succinic acid; 0.5 g/l tartaric acid; 1 mg/l lead ions and 1 mg/l cadmium ions in further oombination with 60 to 130 micro mols/1 of a sulfonium betaine oompound oomprising 3-S-isothiuronium propane J.22S5(~1 sulfonate. The bath was adjusted and maintained at a pH of about
concentration range and moreover, many of such sulfur-containing organic compounds do not produce a nickel-phosphorus alloy deposit in which the phosphorus content is belcw about 8 percent by weight.
Prior art compositions and processes for pro*ucing nickel-phosphorus alloy deposits of relatively high phosphorus contents have also been subject to the disadvantages of requiring relatively rigid control of the concentration of the bath constituents detracting from the ease of control, maintenance and replenishment of such baths to maintain optimum operating performance. The use of stabilizing agents for prcviding increased bath stability has occasioned in prior art compositions a condition of over stabilization whereby a cessation of plating occurs. In such instan oe s, it has been necessary to discard the bath and prepare a new operating bath which constitutes a costly and tinE-consuming operation.
me present invention provides for an improved electroless nickel plating bath and process for depositing a nickel-phosphorus alloy of relatively low phosphorus oontent incorporating an additive agent which can satisfactorily be employed over a relatively broad cperating concentration range while at the same time increasing the rate of deposition of the nickel by as much as 30 percent or mDre. The present invention ~urther provides for an improved electroless nickel plating bath and process suitable for use in depositing nickel-phosphorus platings of relatively high phosphorus content providing for greater latitude in variations in the bath constituents thereby achieving simpler oontrol and facilitating maintenan oe and repl d shment of the bath. The present invention further contempLates a method for rej wenating or resboring an electroless nickel plating bath which has been rendered inoperative due to o~er stabilization thereof by inclusion of organic and/or inorganic stabilizi~g agents in excessive amounts by the addition of an additive agent of the present invention wherehy satisfactory operation of the bath is restored.
Summary of the Invention The benefits and advantages of the present invention are achieved in acoordan oe with the composition aspects thereof by an acueous electroless nickel plating bath oontaining nickel ions, hypcphosphite ions, and an, am~unt of a sulfonium betaine ccmpaund sufficient to control the rate of nickel deposition and the con oe ntration of phosphorus in the nickel deposit. m e sulfonium betaine compound corresponds to the structural formula:
,,, Rl~
C-S-(CHR)--S03e Wherein:
P~ and R4 are the sa~e or different and are H, Cl-C6 alkyl radicals, Cl-C6 hydroxy alkyl radicals, R is the same or different and is H or aH, and - n is an integer of f.~l 1 to S, as well as mixtures thereof.
~2~55~1 m e oonoentration of nickel ions generally ranges from abcut 1 to about 15 grams per liter (g/l), the h~xqphosphite ions range from about 2 to a~out 40 g/l and the sulfonium betaLne cc~pound can range from about 1 up to about 200 micro mol per liter. The bath in order to prc~ide satisfactory prolonged commercial operation further incorporates a cc~plexing agent usually present in an amount up to about 200 g/l for ccmplexing the nickel ions present as well as to solubilize the hypophosphite degradation products formed during prolonged usage of the bath. The electroless bath desirably further contains a buffering agent generally present in amounts up to about 30 g/l, a wetting agent to minimize surfa oe pitting, usually present in an amount up to a~out 1 g/l and hydrogen or hydroxyl ions to provide a bath on the acid or aIkaline side as may be desired. Optionally, but preferably, the bath further ~ ~loys in combination with the sulfonium betaine compound at least one supplemental organic or inorganic stabilizer agent of the various types heretofore known which can be employed in amounts up to that level at which the rate of deposition of nickel is undesirably impaired.
In accordance with the process aspects of the present invention, a low phosphorus-nickel alloy is deposited on a metallic or non~metallic substrate by contacting the cleaned and suitably prepared substrate with the electroless nickel bath at a temperature generally ranging from about 40C up to boiling for a period of as little as 1 minute up to several hours or even days to prcvide a nickel-phosphorus alloy deposit of the desired thickness. During the deposition process, agitation of the bath ., ~2SS~l is preferred, emplcying mild air or other forms of mechanical agitation. The bath is also preferably subjec~ed to periodic or continuous filtration to re~ove solid contamunants. The bath is periodically and/or oontinuously replenished for maintaining the bath constituents within the desirable operating concentrations and at the appropriate pH level.
The present invention further contemplates a process for effecting rejuvenati~n of an electroless nickel bath which has been rendered inoperative due to an over stabilization thereof by organic and/or inorganic stabilizing agents by the addition of a controlled effective amDunt of a sulfonium betaine compound to restore operation the.reof.
Additional benefits and advantages of the present invention will be~a.~ apparent upon a reading of the Description of the Preferred Embodiments taken in conjunction with the accompanying examples.
.
Description of the Preferred Embodiments The aqueous electroless nickel plating baths of the present invention can be cperated over a broad pH range including the acid side and the aLkaline side at a pH of from about 4 up to about 10. For an a~idic bath, the pH can generally range from about 4 up to abcut 7 with a pH of about 4.3 to about 5.2 being preferred. For an aLkaline bath, the pH can range from about 7 up to about 10 with a pH range of from about 8 to about 9 being preferred. Since the bath has a tendency to become more acidic during its operation due to the formation of hydrcgen ions, the pH
~ 12Z55(~1 is periodically or continuously adjusted by addinq bath soluble and oo~patible aIkal~le substances such as alkali metal and ammonium hydroxides, carbonates and bicarbonates. Stability of the cperating pH is also provided by the addition of various buffer compounds such as acetic acid, propionic acid, boric acid or the like in amounts up to about 30 g/l with amounts of about 4 to about 12 g/l being typical.
The nickel ions are introduced into the bath employing various bath soluble and compatihle nickel salts such as nickel sulfate hexahydrate, nickel chloride, nickel acetate, and the like to provide an operating nickel ion concentration ranging from about 1 up to about 15 g/l with concentrations of from about 3 to about 9 g/l being preferred and with a concentration of about 5 to about 8 g/l being opti~num. The hypophosphite reducing ions are introduced by hypophosphorous acid, sodium or potassium hypophosphite, as well as other bath soluble and compatible salts thereof to provide a hypophosphite ion concentration of about 2 up to about 40 g/l, preferably c~bout 12 to 25 g/l with a con oe ntration of cibout 15 to about 20 g/l being optimum. The specific concentration of the nickel ions and hypophosphite ions employed will vary within the aforementioned ranges depending upon the relative concentration of these two constituents in the bath, the particular operating conditions of the bath and the types and concentrations of other bath components present.
In order to provide a commercially satisfactory plating bath of reasonable longevity and operating performance, it is conventional preferred practice to incorporate a complexing agent .` 1~2SSOl or mixture of oomplexing agents in amDunts sufficient to ~ul~lex the nickel ions present in the bath and to further solubilize the hypophcsphite degradation products formed during usage ~of the bath. The oomplexing of the nickel ions present in the bath retards the formation of nickel orthc~hosphite which is of relatively low solubility and tends to form insoluble suspensoids which not only act as catalytic nuclei promoting bath decomposition but also result in the formation of coarse or rough undesirable nickel deposits. Generally, the cc~plexing agents are employed in amounts up to about 200 g/l with amounts of about 15 to about 75 g/l being preferred while amDunts of about 20 to abcut 40 g/l are typical. Complexing or chelating agents of the various types described in the aforementioned United States patents, the teachings of which are incorporated herein by reference, can be satisfactorily employed for this purpose and the particular selection of such c~nplexing agent or nNLYture of complexing agents will be dependent to some extent on the operating bath pH to prc~ide complexors of maximum stability under such specific pH
conditions. Typical of such cc~plexing agents are the acid as well as aIkali metal and anmDnium salts of glycolic acid, lactic acid, malic acid, glycine, citric acid, acetic acid, tartaric acid, succinic acid, and the like. While aIkaline earth metal salts can also be employed to some extent, the tendency of such alkaline earth metals to fonm insoluble precipitates with the bath constituents renders them less desirable and for this reason are preferably excluded. It will also be appreciated, that certain complexing agents such as acetic acid, for example, also act as a "-` 12Z~5~31 buffering agent and the appropriate concentration of such additive oomponents can be cptimized for any bath oomposition in consideration of their dual-functioning properties.
In a~ition to the foregoing constituents, the bath further includes as an essential constituent, a plating rate and phosphorus controlling agent present in an amcunt effective to enhan oe the rate of deposition of the nickel-phosphorus allcy and to provide an alloy deposit generally containing less than ab~ut 8 per oe nt by weight phosphorus. Ihe additive agent comprises a sul.onium betaine oompound corresponding to tke structural formLla:
Rl~
~3~C-S- (CHR)--S03e R?N
~herein:
P~, R2, ~ and R4 are the same or different and are H, Cl-C6 alkyl radicals, Cl-C6 hydroxy al~yl radicals, R is the same or different and is H or OH, and n is an integer of fro~ 1 to 5, as well as mixtures thereof.
A sulfonium betaine ocmpound oorresponding to the foregoing structural formula which has ~een found particularly satisfactory comprises 3-S-isokhiuronium propane sulfonate. Ihis ~,yound corresponds to tke foregoing structural formula in which `-` lZZ5501 Rl, R2~ R3 and R4 are hydrogen and n is 3. Alternative satisfactory ~sulfonium betaine compounds which can be emplc~d include N,N'-dimethyl-3-S-isothiuronium propane sulfonate, N,N'-diethyl-3-S-isothiuronium propane sulfonate, N,N'-di~ydroxymethyl-3-S-isothiuronium propane sulfonate, N,N'-diisopropy1-3-S-isothiuronium propane sulfonate, N,N,N',N'-tetramethyl-3-S-isothiuronium propane sulfonate, N,N,N'-trimethyl-3-S-isothiuronium propane sulfonate, 2-S-isothiuronium ethane sulfonate, 3-S-isothiuronium propane-2-ol sulfonate and the like. These additive compounds are extremely effective even in relatively l~ow concentrations such as about 1 micro mol per liter to oon oe ntrations as high as about 200 micro mol per liter. The foregoing broad range of operating concentrations provides for a substantial simplification of analysis and control of the operating bath under c~~ rcial operating conditions providing significant advantages over prior art additiv~ ccmpounds of the types heretofore kncwn. The sulfonium betaine oompound in accordance with a preferred practice is employed in acidic baths at a concertration of about 10 to about 150 micro mol per liter with a concentration of about 20 to about 120 micro mDl per liter being typical. In aLkaline baths, the sulfonium betaine compound is preferably employed at a con oe ntration of about 1 to about 50 micro mol per liter with a concentration of about 2 to about 25 micro mol per liter being typical.
In accordance with a further preferred practice of the present invention, the sulfonium betaine compound is e~ployed in .
;50~
combination with other conventional inorganic and/or organic stabilizing agents of the types heretofore kncwn including lead ions, cadmlum ions, tin ions, bi~muth ions, antim~ny ions and zinc ions which can conveniently be introduced in the fonm of bath soluble and compatible salts including halides, acetates, sulfates, and the like. Plternatively, otner stabilizing agents can be employed including cyanide ions, thiocyanate ions, and the like which typically can be used in amounts of from about 1 up to about 20 p~m. Lead ions can be employed in amounts usually up to about 2 ppm; cadmium ions in an amount up to about 10 ppm;
antimony and tin ions can be employed in an amount up to about 100 ppm. m e specific concentration of such supplemental stabilizing agent or mixtures of supplemental stabilizing agents is limited by such con oe ntrations at which the rate of nickel deposition is inhibited to an undesirable magnitude rendering the bath commercially impractical.
The bath may additionally employ one or a mixture of suitable wetting agents of any of the various types heretofore known which are soluble and compatible with the other bath aonstituents. The use of such wetting agents is desirable to prevent pitting of the nickel alloy deposit and can usually be employed in amounts up to about 1 g/l.
In acaordance with the pro oe ss aspects of the present invention,-a substrate to be plated is contacted with the bath solutian at a temperature of at least about 40C up to boiling.
Electroless nickel baths of an acidic type are preferably employed at a temperature of from about 70 to about 95C with a temperature " ~ZZ55C~:l of about 80 to a~out 90C bein~ optimum. Electroless nickel baths on the alkaline side are generally operated within the broad operating range but at a correspondingly lower temperature than the acid-type bath sin oe pH and bath temperature are inte..~lated in that the rate of nic~el deposition increases as the pH
increases but the stability of the bath increases as the pH of the bath decreases while the rate of deposition of nickel increases as the temperature increases but with a corresponding decrease in bath stability.
me duration of contact of the electroless nickel solution with a substrate being plated is a function dependent entirely on the desired thickness of the nickel-phosphorus alloy desired. Typically, the contact time can range frcm as little as about 1 minute to several hours or even several days.
Conventionally, a plating deposit of about 0.2 up to about 1.5 mils is a normal thickness for many commercial applications. When wear resistance is desired, such deposits can be applied at a thickness of about 3 to about 5 mils such as on valves, pipes, dies and the like. m icknesses of up to about 0.25 inch can also be achieved by a correspondingly longer contact time as may be desired.
During the deposition of the nickel alloy plate, it is preferred to employ mild agitation such as mild air agitation, mechanical agitation, bath circulation by pumping, as well as by bar~el plating in which the rotation of the immersed barrel imparts agitation to the batn. It is also preferred to subject the bath to a periodic or continuous filtration treatment to ~ZZS5~1 . ,~
reduce the level of contam~nants therein. Replenishment of the constituents in the bath is also performed on a periodic or continuous basis to maintain the con oe ntration, particularly of the nickel icns, hypaphosphite ions, and p~ level within the desired limits.
The substrate to be plated is subjected to a prellminary surfa oe preparation in accordan oe with oonventional practioe to provide a clean and catalytically active surface. In the case of substrates which Q nnot be directly coated employ mg the electroless nickel bath because of their non-catalytic nature relative to the chemistry of the bath, the substrates can be preliminarily subjected to an electrolytic plating of nickel or such other metal which is catalytic whereby the substrate surfa oe is re oe ptive or made receptive to chemical deposition of nickel fron the electroless bath.
In acc~rdan oe with a further process aspect of the present invention, electroless nickel plating baths which have been rendered inoperative for depositing a nickel-phosphorus alloy deposit on a substrate due to the use of an excessive amount of inorganic and/or organic stabilizing agents, can be restored to effective operation by the addition thereto of a sulfonium betaine ccr~x~m d as hereinbefore defined as ~ell as mixtures thereof in an amount effective to restore satisfactory operation. The concentration of the sulfonium betaine compound employed for effec,ting rejuvenation can range within the limits as hereinbefore specified with ooncentrations of from about 20 to about 120 micro mol per liter being typical for acidic-type baths and with .~
-, ~Z25SOl con oe ntrations of about 2 to about 25 micro mol pPr liter being typical for alkaline-type baths. m e sulfonium betaine oompound is added bo the bath in the presen oe of agitation to effect a substantially unifonm distribution thereof.
In order to further illustrate the present invention, the following examples are p m vided. It will be understood that the examples are provided for illustrative purposes and are not intended bo be lLmdting of the soope of the present Lnvention as herein described and as set forth in the subjoined claims.
E~MPLE 1 Three 500 milliliter electroless nickel plating baths were prepared oontaining 27 g/l of nickel sulfate hexahydrate (equivalent to 6 g/l nickel ions); 24 g/l of sodium hypophosphite mDnohydrate (equivalent to 14.7 g/l hypophosphite ions); 14 g/l malic acid; 9 g/l a oe t~c acid; and the pH of each bath was adjusted to about 5 using ammonium hydroxide. A separate stabilizing agent of the types heretofore employed was added to each bath in acoordan oe with the tabulation as set forth in Table 1.
~E 1 Rate of Depo- Percent P
Stabilizer Gonc., mq/l sition, mil/hr. in Deposit Lead ions 0.5 0.68 9.4 Thicurea 3.0 1.1 6.2 ` T ~ roprionic 3.0 1.3 9.6 Acid ~2Z5501 The lead ion oon oe ntration as set forth in Table 1 is equivalent to 2.4 micro mols/l; the ooncentration of the thiourea stabilizer is equivalent to 39.4 micro mDls/l; the con oe ntration oS the thiodiproprionic acid stabilizer is equivalent to 16.8 micro mDls/l.
The temperature of each sample plating bath was adjusted to about 88 to about 90C. Cleaned stainless steel panels (39 cm2 area) were immersed in each bath and were prelLminarily electroplated for 30 seconds while cathodically charged to initiate chemical deposition on the stainless steel. Thereafter, electroless deposition of the nickel-phosphorus alloy was oontinued for a total of 60 minutes. The resultant nickel-phosphorus alloy deposits were separated from the stainless steel substrates and the foils were measured for thickness and were analyzed for phosphorus content. The rate of deposition in terms of mils per hour and the percentage phosphorus in the nickel alloy deposit are set forth in Table 1, The data as set forth in Table 1 clearly demonstrates that both thiourea and thiodiproprionic acid are effective in increasing the rate of deposition of the nickel alloy deposit in co~earison to the bath sample in which lead ions are the only stabilizer. However, while both thiourea and thiodiproprionic acid are thio compounds, only the thiourea stabilizer lowers the percentage of phosphorus in the nickel alloy deposit. The phosphorus content in the nickel alloy deposit when employing lead ions or thiodiproprionic acid stabilizers is in exoe ss of 9 percent by weight.
';
lZ2S501 A series of 500 milliliter electroless nichel plating baths was prepared containing 27 g/l nickel sulfate hexahydrate;
30 g/l sodium hypophosphite monohydrate (equivalent to 18.4 g/l hypcphosphite ions); 26 g/l lactic acid; 9 g/l acetic acid; and the pH was adiusted to about 4.9 employing amm~nium hydroxide. Tb each bath sample a controlled amLunt of a thiourea stabilizing agent or a sulfonium ~etaine compound oo~prising 3-S-isothiuronium propane sulfonate was added in accordance with the concentrations as set forth in Table 2. One sample bath was devoid of any stabilizing agent to serve as a control.
~AELE 2 Con oe ntration, Rate of Depo- Percent P
Stabilizermicromols/l sition, mil/hr. in Deposit None - 0.80 ~ 9.90 m iourea 13.1 1.00 6.67 m iourea 26.3 1.25 6.76 Thiourea 39.4 1.10 6.83 Thiourea 52.6 1.02 6.49 m iourea 65.7 1.03 6.46 Thiourea 78.9 zero 3-S-iso- 6.3 1.10 8.22 thiuronium propane 31.6 1.10 7.36 sulfonate " 63.2 1.23 6.36 94 9 ~.00 6.29 " 110.7 1.12 5.95 " 126.5 1.02 5.42 n 142.4 1.05 5.34 " 158.2 zero Cleaned stainless steel test panels were plated in accordan oe with the procedure descri~ed in Example 1 employing a bath operating temperature of about 88 to about 90C for a period of 60 minutes following an initial 30 second electrolytic deposition on each test panel to initiate deposition. The ~ lZZ55(~1 resulting nickel-phosphorus alloy deposit produced from each bath sample was remcved as a foil from the test panel and the foils were measured with a dial micrometer to determine the deposition rate and were also analyzed for the percentage of phosphorus in the deposit. The results are also set forth in Table 2.
As will be apparent from the data set forth in Table 2, both the thiourea stabilizing agent and the sulfonium betaine compound additiv~ provide an increase in the rate of deposition of the nickel-phosphorus deposit in oomparison to the same bath devoid of any stabilizing additive agent. Hbwever, it will be noted that the useful operating range of the sulfonium betaine compourd is m~re than twice that of the thiourea stabilizing agent providing for substantial simplicity in the maintenance and control of the plating bath during commercial operation.
Furthermore, the percentage of phosphorus in the deposit obtained from the baths employing the sulfonium betaine compound in a~rdance with the practi oe of the present invention attains a value of m~re than 17 percent less than that obtained employing the thiourea stabilizing agent.
A six liter electroless nickel plating bath was prepared oontaining 27 g/l nickel sulfate hexahydrate; 30 g/l sodium hypophosphite monohydrate; 35 g/l lactic acid; 1.5 g/l succinic acid; 0.5 g/l tartaric acid; 1 mg/l lead ions and 1 mg/l cadmium ions in further oombination with 60 to 130 micro mols/1 of a sulfonium betaine oompound oomprising 3-S-isothiuronium propane J.22S5(~1 sulfonate. The bath was adjusted and maintained at a pH of about
4.2 to about 5.2 employing a~mDnium hydroxide and at a te~perature ranging from abcut 85 to about 95C for a prolonged test. The bath was periodically replenished to maintain the nickel and hypophosphite ion oon oe ntration substantially constant for more tihm 8 bath turnovers. A bath "turnc~er" or bath cycle is defined as a plating duration when all of the original nickel metal content in the bath has been consu~ed and has been replenished by subsequent additions. Generally, the useful operating life of electroless nickel plating baths in accordance with prior art practice ranges from about 6 to about 10 turnovers before the bath must be discarded.
At various times during the operating life of the bath, test panels were plated in the bath in accordance with the procedure as set forth in Example 1 and the nickel-phosphorus alloy deposits were analyzed for percentage of phosphorus as well as the deposition rate of the nickel alloy deposit. me results obtained are set forth in Table 3.
Bath Eath Bath Temp. Deposition Per oe nt P
TurnoverspH C Rate mils/hr. in ~eposit 6.4 4.6 95C O.S0 3.5 7.8 4.8 95C 0.48 2.8 8.1 4.2 85C 0.22 3.2 The data as set forth in Table 3 clearly demDnstrate the very low per oe ntages of phosphorus in the nickel alloy deposit lZ2~SOi which are obtainable employing an electroless nickel plating bath prepared in acoordan oe with the present invention employ m g concentrations and operating conditions typical of those employed commercially. It is anticipated from prior testing that if only lead ions and cadmium ions had been employed as stabilizer agents without the presen oe of the sulfonium betaine ~ uund, the nickel alloy deposit would have contained in excess of about 9 to 10 percent phosphorus particularly when operating at a pH of ~bout 4.2. In oontrast, the use of the sulfonium betaine compound provided nickel alloy deposits which were well und~r 4 percent by weight phcsphorus. It will be further noted, that the bath of Example 3 is simple to control because of the relatively broad effective operating range of con oe ntration permissible by the 3-S-isothiuronium propane sulfonate additive compound.
A 500 milliliter electroless nickel plating bath was ,orepared using 27 g/l of nickel sulfate hexahydrate (equivalent to 6 g/l of nickel ions); 30 g/l of sodium hypophosphite monohydrate (equivalent to 18.4 g/l of hypophosphite ions); 31 g/l of lactic acid; 2 g/l of malic acid; 0.6 g/l of citric acid; 0.00237 g/l of cadmium a oe tate dihydrate (equivalent to 1 mg/l of cadmium ions) and sufficient ammonium hydroxide to produce a bath pH of about 5Ø Tb the ~ath was then added 0.176 g/l of antimony potassium tartrate trihydrate; -Sb2K2C8H4012-3H20- (equivalent to 64 mg/l of antimony ions). ~en this plating bath was heated to 90C, and a cleaned steel panel (80 cm2 surfa oe area) was immersed in the `` lZ2550~;
bath, it was found that a deposit of nickel could not be obtained because the bath was over stabilized with antimony and cadmium ions.
To the foregoing bath, 8 mg/l (40.4 micro mol/l) of 3-S-isothiuronium propane sulfonate was added. When this bath was heated to 90C and a steel panel ~ 80 cm2 surfa oe area) was immersed in it, an excellent nickel deposit was obtained. The nickel deposition rate was about 1.3 mil/hr. for a thirty minute deposit. The deposit was analyzed and contained 7.95 percent by weight phosphorus.
This example demonstrates that the sulfonium betaine ocmpounds of this invention can also rejuvenate an otherwise over stabilized electroless nickel plating bath to restore it to satisfactory operation condition.
Four 500 ml electroless nickel plating baths were prepared using 27 g/l nickel sulfate hexahydrate, 30 g/l sodium hypophosphite, 31 g/l lactic acid, 2 g/l malic acid and sufficient ammcnium hydroxide to provide a bath pH of about 5Ø Each bath additionally oontained 2 mg/l of lead ions and 3 mg/l of cadmium ions to stabilize the bath and brighten the nickel alloy deposits.
m e lead and cadmium ions were added as the acetate salts. TD
these four baths, various oonoentrations of 3-S-isothiuronium propane sulfonate were added and were thereafter heated to between 85 and 90C. Stainless steel panels (80 cm2 surfa oe area), previously given a 15 second Watts nickel strike to insure plating 225;5~1 on the stainless steel and easy subsequent remc~al of the deposits for analysis, were then plated for 30 minutes. The plating results are summarized in Table 4.
T~LE 4 Concentration of 3-S-isothiuronium propane sulfonate neposition Percent by wt. P
(micro mol/liter Rate ~mil/hr.) in ~eposit Zero No deposit No deposit 20.2 1.0 7.0 40.4 1.0 5.2 60.6 0.9 3.8 The bath that did not contain the sulfonium betaine compound did not produce an electroless nickel deposit because the bath was over stabilized with lead and cadmium. Additions of the sulfonium betaine overcame the excessive concentration of metallic stabilizers, and satisfactory deposits were obtained with good rates of deposition. This example further demonstrates that increasing the concentration of the sulfonium betai~e may decrease the percentage of phosphorus in the deposit so that the desired amDunt of phosphorus can be obtained by controlling the concentration of sulfonium betaine in the plating bath.
Five 500 ml electroless nickel plating baths were prepared using the bath formulation as listed in Example 5. In place of the lead, however, 16 mg/l of antimony (added as antimony ~50I
.
potassium tartrate) were employed as a metallic stabilizer while the cadmium ion ~added as the acetate salt) oonoe ntration was 1 mg/l. Four of the baths additionally oontained various conoentrations of 3-S-isothiuronium prcQane sulfonate.
Nickel-phosphorus alloy deposits were obtained using the procedure outlined in Example 5 so that deposition rate and phosphorus oontent oould be medsured. Table 5 summarizes the results of these tests.
Concentration of 3-S-isothiuronium proFane sulfonate Deposition Percent by wt. P
(micro mDl/liter) Rate (mil/hr.) in Deposit Zero l.0 10.6 20.2 1.0 7.16 40.4 l.0 6.69 60.6 ~.0 6.82 80.8 No deposit No deposit The above data demDnstrates that when 3-S-isothiuronium propane sulfanate is used in combination with antimDny rather than lead as the metallic stabilizer, the phosphorus oontent of the resulting electroless nickel deposits does not continue to decrease with increasing ooncentrations of the sulfonium betaine, but rather remains fairly constant at about 7 percent. miS
feature is advantageous in commercial practice as wide variations in sulfonium betaine ooncentration do not result in appreciable changes in the phosphorus aontent of the nickel-alloy deposit.
-EX oe ssive amounts of the sulfonium betaine compound can over stabilize the bath and should normally be avoided. me actual concentration that prevents nickel deposition varies, depending cn the basic bath composition as well as the ooncentration and kinds of other metal ions present in the bath.
E~U~LE 7 An aqueous acidic electroless nickel plating bath is prepared containing the following oonstituents:
Constituent g/l NiS04 6H2 27 NaH2P02 2 Malic acid 15 Lactic acid 10 Citric acid o.s Sblll 0.010 Pb++ 0.0005 Cd++ 0.001 3-S-isothiuronium 0.005 propane sulfonate NH40H - to give pH 4.6 - 5.2 The bath is operated at a temperature of about 75 to about 95C.
The concentrations of the various bath components may be varied up or down by at least 25 percent without seriously impairing the efficacy of the system. Likewise, simple substitutions can be made. For example, scdium hydroxide may be .
lZZ~
used in place of amm~nium hydroxide if an ammonia free bath is desired b~cause of environmental considerations. Potassium hypophosphite may be used in place of sodium hypophosphite.
Sodium, pokassium, ammDnium and si~llar salts of the oomplexor acids may be used rather than the paren~ acids. Likewise, the metallic stabilizers may be added as the salt of any bath compatible anion, such as acetate, tartrate, propionate, etc.
A 500 ml alkaline electroless nickel bath was prepared containing 26 g/l nickel chloride hexahydrate (equivalent to 6.4 g/1 of nickel ions), 15 g/l of sodium hypophosphite (equivalent to ~.2 g/l of hypophosphite ions), 50 g/l of ammcnium chloride, 60 g/l of diammonium hydrogen citrate, and 0.003 g/l of 3-S-isothiuronium propane sulfonate ~equivalent to 15 micro mol/l). The pH was adjusted to 8.5 and the bath was operated at a temperature of 80 to 85C.
A test panel oomprising a nonconductive polymeric material was subjected to a conventional pretreatment to render the polymeric substrate receptive to a ~subsequent electroless nickel plating. Suc-h pretreatment as well known in the art includ~es cleaning, etching, neutralization, and subseouent activation employing an aqueous acidic solution containing a tir.-palladium oomplex to foDm active sites on the substrate generally followed by an accelerating treatment. The resultant pretreated polymeric test panel was immersed in the alkaline bath for a pnriod of 30 minutes. An inspection of the plated test 0~
panel revealed a r.ickel alloy deposit containing about 3 percent by weight phosphorus. The rate of deposition was about 0.2 mil per hour. While t~is deposition rate is oomparatively low cor~xLn~d to mDst acidic electroless nickel plating kaths, it is generally adequate for many applications such as plating on plastics, glass and other nonmetallic substrates.
It was also observed that further additions of the sulfonium betaine compound to the alkaline bath caused a cessation in the deposition of the nickel alloy deposit when the concentration attained about 25 micro mol per liter. The maximum permissible concentration of the sulfonium betaine oompound in such aLkaline electroless nickel baths will vary depending upon the specific chemistry of the bath and the types and concentrations of other constituents present. Generally, the l~Pful cperating ooncentration range of the sulfonium betaine co~pound is lower for alkaline electroless nickel plating baths than for acidic electroless nickel plating baths.
EXAMoeLE 9 A series of electroless nickel plating baths is prepared containing nickel ions in a concentration ranging from about 1 up to about 15 gtl; hypophosphite ions in a concentration ranging fram about 2 up to about 40 g/l; ccmplexing agents present in amounts up to about 200 g/l including glycolic acid, lactic acid, malic acid, glycine, citric acid, acetic acid, tartaric acid, succinic acid as well as the bath soluble and oompatible salts and mixtures thereof; a bath soluble and ccmpatible wetting agent in ~Z255~1 amounts up to about 1 g/l; stabilizing metal ions including lead, cadmium, tin, bis~uth, antimcny, zinc and mixtures thereof in conoentrations up to about 100 ppm; other stabilizing agents including cyanide, thiocyanate and simiLar well known stabilizing ions in anounts up to abcut 2D ppm; and one or a mQxture of sulfonium betaine compounds including 3-S-isothiuranium propane sulfonate, N,N'-dimethyl-3-S-isothiuronium propane sulfonate, N,N'-diethyl-3-S-isothiuronium propane sulfonate, N,N'-dihydroxymethyl-3-S-iscthiuronium propane sulfonate, N,N'~diisapropy1-3-S-isothiuranium propane sulfonate, N,N,N',N'-tetr~.~thyl-3-S-isothiuronium prapane sulfonate, N,N,N'-trimethyl-3-S-isothiuronium propane sulfonate, 2-S-isothiuronium ethane sulfonate, 3-S-isothiuronium propane-2-ol sulfonate as well as mixtures thereof in con oe ntrations ranging from about 1 up to about 200 micro mol per liter and hydrogen or hydroxyl ions to provide a bath pH ranging from about 4 to about 7 on the acid side and fram about 7 to about 10 on the alkaline side. The specific constituents were varied within the foregoing ranges to provide for cptimum deposition of the nickel-phosphorus alloy in accordan oe with the intended deposit desired.
Test panels were plated in the series of baths maintained at temperatures ranging fram about 40 up to boiling for time periods as short as about 1 mQnute to times of several days to achieve the desired deposit thickness. Many of the baths were operated employing mild agitation.
Satisfactory nickel alloy deposits were obtained.
~2Z~
While it will be apparent that the preferred embodi~ents of the invention disclosed are well calculated to fulfill the objects above stat~d, it will be appreciated that the invention is susceptible to modification, variation and change withDut departing from the proper soope or fair meaning of the subjoined claims.
At various times during the operating life of the bath, test panels were plated in the bath in accordance with the procedure as set forth in Example 1 and the nickel-phosphorus alloy deposits were analyzed for percentage of phosphorus as well as the deposition rate of the nickel alloy deposit. me results obtained are set forth in Table 3.
Bath Eath Bath Temp. Deposition Per oe nt P
TurnoverspH C Rate mils/hr. in ~eposit 6.4 4.6 95C O.S0 3.5 7.8 4.8 95C 0.48 2.8 8.1 4.2 85C 0.22 3.2 The data as set forth in Table 3 clearly demDnstrate the very low per oe ntages of phosphorus in the nickel alloy deposit lZ2~SOi which are obtainable employing an electroless nickel plating bath prepared in acoordan oe with the present invention employ m g concentrations and operating conditions typical of those employed commercially. It is anticipated from prior testing that if only lead ions and cadmium ions had been employed as stabilizer agents without the presen oe of the sulfonium betaine ~ uund, the nickel alloy deposit would have contained in excess of about 9 to 10 percent phosphorus particularly when operating at a pH of ~bout 4.2. In oontrast, the use of the sulfonium betaine compound provided nickel alloy deposits which were well und~r 4 percent by weight phcsphorus. It will be further noted, that the bath of Example 3 is simple to control because of the relatively broad effective operating range of con oe ntration permissible by the 3-S-isothiuronium propane sulfonate additive compound.
A 500 milliliter electroless nickel plating bath was ,orepared using 27 g/l of nickel sulfate hexahydrate (equivalent to 6 g/l of nickel ions); 30 g/l of sodium hypophosphite monohydrate (equivalent to 18.4 g/l of hypophosphite ions); 31 g/l of lactic acid; 2 g/l of malic acid; 0.6 g/l of citric acid; 0.00237 g/l of cadmium a oe tate dihydrate (equivalent to 1 mg/l of cadmium ions) and sufficient ammonium hydroxide to produce a bath pH of about 5Ø Tb the ~ath was then added 0.176 g/l of antimony potassium tartrate trihydrate; -Sb2K2C8H4012-3H20- (equivalent to 64 mg/l of antimony ions). ~en this plating bath was heated to 90C, and a cleaned steel panel (80 cm2 surfa oe area) was immersed in the `` lZ2550~;
bath, it was found that a deposit of nickel could not be obtained because the bath was over stabilized with antimony and cadmium ions.
To the foregoing bath, 8 mg/l (40.4 micro mol/l) of 3-S-isothiuronium propane sulfonate was added. When this bath was heated to 90C and a steel panel ~ 80 cm2 surfa oe area) was immersed in it, an excellent nickel deposit was obtained. The nickel deposition rate was about 1.3 mil/hr. for a thirty minute deposit. The deposit was analyzed and contained 7.95 percent by weight phosphorus.
This example demonstrates that the sulfonium betaine ocmpounds of this invention can also rejuvenate an otherwise over stabilized electroless nickel plating bath to restore it to satisfactory operation condition.
Four 500 ml electroless nickel plating baths were prepared using 27 g/l nickel sulfate hexahydrate, 30 g/l sodium hypophosphite, 31 g/l lactic acid, 2 g/l malic acid and sufficient ammcnium hydroxide to provide a bath pH of about 5Ø Each bath additionally oontained 2 mg/l of lead ions and 3 mg/l of cadmium ions to stabilize the bath and brighten the nickel alloy deposits.
m e lead and cadmium ions were added as the acetate salts. TD
these four baths, various oonoentrations of 3-S-isothiuronium propane sulfonate were added and were thereafter heated to between 85 and 90C. Stainless steel panels (80 cm2 surfa oe area), previously given a 15 second Watts nickel strike to insure plating 225;5~1 on the stainless steel and easy subsequent remc~al of the deposits for analysis, were then plated for 30 minutes. The plating results are summarized in Table 4.
T~LE 4 Concentration of 3-S-isothiuronium propane sulfonate neposition Percent by wt. P
(micro mol/liter Rate ~mil/hr.) in ~eposit Zero No deposit No deposit 20.2 1.0 7.0 40.4 1.0 5.2 60.6 0.9 3.8 The bath that did not contain the sulfonium betaine compound did not produce an electroless nickel deposit because the bath was over stabilized with lead and cadmium. Additions of the sulfonium betaine overcame the excessive concentration of metallic stabilizers, and satisfactory deposits were obtained with good rates of deposition. This example further demonstrates that increasing the concentration of the sulfonium betai~e may decrease the percentage of phosphorus in the deposit so that the desired amDunt of phosphorus can be obtained by controlling the concentration of sulfonium betaine in the plating bath.
Five 500 ml electroless nickel plating baths were prepared using the bath formulation as listed in Example 5. In place of the lead, however, 16 mg/l of antimony (added as antimony ~50I
.
potassium tartrate) were employed as a metallic stabilizer while the cadmium ion ~added as the acetate salt) oonoe ntration was 1 mg/l. Four of the baths additionally oontained various conoentrations of 3-S-isothiuronium prcQane sulfonate.
Nickel-phosphorus alloy deposits were obtained using the procedure outlined in Example 5 so that deposition rate and phosphorus oontent oould be medsured. Table 5 summarizes the results of these tests.
Concentration of 3-S-isothiuronium proFane sulfonate Deposition Percent by wt. P
(micro mDl/liter) Rate (mil/hr.) in Deposit Zero l.0 10.6 20.2 1.0 7.16 40.4 l.0 6.69 60.6 ~.0 6.82 80.8 No deposit No deposit The above data demDnstrates that when 3-S-isothiuronium propane sulfanate is used in combination with antimDny rather than lead as the metallic stabilizer, the phosphorus oontent of the resulting electroless nickel deposits does not continue to decrease with increasing ooncentrations of the sulfonium betaine, but rather remains fairly constant at about 7 percent. miS
feature is advantageous in commercial practice as wide variations in sulfonium betaine ooncentration do not result in appreciable changes in the phosphorus aontent of the nickel-alloy deposit.
-EX oe ssive amounts of the sulfonium betaine compound can over stabilize the bath and should normally be avoided. me actual concentration that prevents nickel deposition varies, depending cn the basic bath composition as well as the ooncentration and kinds of other metal ions present in the bath.
E~U~LE 7 An aqueous acidic electroless nickel plating bath is prepared containing the following oonstituents:
Constituent g/l NiS04 6H2 27 NaH2P02 2 Malic acid 15 Lactic acid 10 Citric acid o.s Sblll 0.010 Pb++ 0.0005 Cd++ 0.001 3-S-isothiuronium 0.005 propane sulfonate NH40H - to give pH 4.6 - 5.2 The bath is operated at a temperature of about 75 to about 95C.
The concentrations of the various bath components may be varied up or down by at least 25 percent without seriously impairing the efficacy of the system. Likewise, simple substitutions can be made. For example, scdium hydroxide may be .
lZZ~
used in place of amm~nium hydroxide if an ammonia free bath is desired b~cause of environmental considerations. Potassium hypophosphite may be used in place of sodium hypophosphite.
Sodium, pokassium, ammDnium and si~llar salts of the oomplexor acids may be used rather than the paren~ acids. Likewise, the metallic stabilizers may be added as the salt of any bath compatible anion, such as acetate, tartrate, propionate, etc.
A 500 ml alkaline electroless nickel bath was prepared containing 26 g/l nickel chloride hexahydrate (equivalent to 6.4 g/1 of nickel ions), 15 g/l of sodium hypophosphite (equivalent to ~.2 g/l of hypophosphite ions), 50 g/l of ammcnium chloride, 60 g/l of diammonium hydrogen citrate, and 0.003 g/l of 3-S-isothiuronium propane sulfonate ~equivalent to 15 micro mol/l). The pH was adjusted to 8.5 and the bath was operated at a temperature of 80 to 85C.
A test panel oomprising a nonconductive polymeric material was subjected to a conventional pretreatment to render the polymeric substrate receptive to a ~subsequent electroless nickel plating. Suc-h pretreatment as well known in the art includ~es cleaning, etching, neutralization, and subseouent activation employing an aqueous acidic solution containing a tir.-palladium oomplex to foDm active sites on the substrate generally followed by an accelerating treatment. The resultant pretreated polymeric test panel was immersed in the alkaline bath for a pnriod of 30 minutes. An inspection of the plated test 0~
panel revealed a r.ickel alloy deposit containing about 3 percent by weight phosphorus. The rate of deposition was about 0.2 mil per hour. While t~is deposition rate is oomparatively low cor~xLn~d to mDst acidic electroless nickel plating kaths, it is generally adequate for many applications such as plating on plastics, glass and other nonmetallic substrates.
It was also observed that further additions of the sulfonium betaine compound to the alkaline bath caused a cessation in the deposition of the nickel alloy deposit when the concentration attained about 25 micro mol per liter. The maximum permissible concentration of the sulfonium betaine oompound in such aLkaline electroless nickel baths will vary depending upon the specific chemistry of the bath and the types and concentrations of other constituents present. Generally, the l~Pful cperating ooncentration range of the sulfonium betaine co~pound is lower for alkaline electroless nickel plating baths than for acidic electroless nickel plating baths.
EXAMoeLE 9 A series of electroless nickel plating baths is prepared containing nickel ions in a concentration ranging from about 1 up to about 15 gtl; hypophosphite ions in a concentration ranging fram about 2 up to about 40 g/l; ccmplexing agents present in amounts up to about 200 g/l including glycolic acid, lactic acid, malic acid, glycine, citric acid, acetic acid, tartaric acid, succinic acid as well as the bath soluble and oompatible salts and mixtures thereof; a bath soluble and ccmpatible wetting agent in ~Z255~1 amounts up to about 1 g/l; stabilizing metal ions including lead, cadmium, tin, bis~uth, antimcny, zinc and mixtures thereof in conoentrations up to about 100 ppm; other stabilizing agents including cyanide, thiocyanate and simiLar well known stabilizing ions in anounts up to abcut 2D ppm; and one or a mQxture of sulfonium betaine compounds including 3-S-isothiuranium propane sulfonate, N,N'-dimethyl-3-S-isothiuronium propane sulfonate, N,N'-diethyl-3-S-isothiuronium propane sulfonate, N,N'-dihydroxymethyl-3-S-iscthiuronium propane sulfonate, N,N'~diisapropy1-3-S-isothiuranium propane sulfonate, N,N,N',N'-tetr~.~thyl-3-S-isothiuronium prapane sulfonate, N,N,N'-trimethyl-3-S-isothiuronium propane sulfonate, 2-S-isothiuronium ethane sulfonate, 3-S-isothiuronium propane-2-ol sulfonate as well as mixtures thereof in con oe ntrations ranging from about 1 up to about 200 micro mol per liter and hydrogen or hydroxyl ions to provide a bath pH ranging from about 4 to about 7 on the acid side and fram about 7 to about 10 on the alkaline side. The specific constituents were varied within the foregoing ranges to provide for cptimum deposition of the nickel-phosphorus alloy in accordan oe with the intended deposit desired.
Test panels were plated in the series of baths maintained at temperatures ranging fram about 40 up to boiling for time periods as short as about 1 mQnute to times of several days to achieve the desired deposit thickness. Many of the baths were operated employing mild agitation.
Satisfactory nickel alloy deposits were obtained.
~2Z~
While it will be apparent that the preferred embodi~ents of the invention disclosed are well calculated to fulfill the objects above stat~d, it will be appreciated that the invention is susceptible to modification, variation and change withDut departing from the proper soope or fair meaning of the subjoined claims.
Claims (20)
1. An aqueous electroless nickel plating bath rising nickel ions and hypophosphite ions in an amount sufficient to chemically deposit nickel and an amount of a sulfonium betaine compound sufficient to control the rate of nickel deposition and the concentration of phosphorus in the nickel deposit, said sulfonium betaine compound corresponding to the structural formula:
Wherein:
R1, R2, R3 and R4 are the same or different and are H, C1-C6 alkyl radicals, C1-C6 hydroxy alkyl radicals, R is the same or different and is H or OH, and n is an integer of from 1 to 5, as well as mixtures thereof.
Wherein:
R1, R2, R3 and R4 are the same or different and are H, C1-C6 alkyl radicals, C1-C6 hydroxy alkyl radicals, R is the same or different and is H or OH, and n is an integer of from 1 to 5, as well as mixtures thereof.
2. The bath as defined in claim 1 further including a complexing agent present in an amount sufficient to complex said nickel ions present and to solubilize any hypophosphite degradation products present in said bath.
3. The bath as defined in claim 1 having a pH of about 4 to about 10.
4. The bath as defined in claim 1 further including a buffering agent.
5. The bath as defined in claim 1 in which said sulfonium betaine compound is present in an amount of at least about 1 up to about 200 micro mol/l.
6. The bath as defined in claim 1 having a pH of about 4 to about 7 and in which said sulfonium betaine compound is present in an amount of about 20 to about 120 micro mol/l.
7. The bath as defined in claim 1 having a pH of about 7 to about 10 and in which said sulfonium betaine compound is present in an amount of about 2 to about 25 micro mol/1.
8. The bath as defined in claim 1 in which said nickel ions are present in an amount of about 1 to about 15 g/l.
9. The bath as defined in claim 1 in which said hypophosphite ions are present in an amount of about 2 to about 40 g/l.
10. The bath as defined in claim 1 in which said nickel ions are present in an amount of about 1 to about 15 g/l, said hypophosphite ions are present in an amount of about 2 to about 40 g/l, and said sulfonium betaine compound is present in an amount of at least about 1 up to about 200 micro mol/l.
11. The bath as defined in claim 10 further containing a complexing agent present in an amount up to about 200 g/l.
12. The bath as defined in claim 11 further containing a complexing agent present in an amount of about 20 to about 40 g/l.
13. The bath as defined in claim 10 further containing a buffering agent present in an amount up to about 30 g/l.
14. The bath as defined in claim 1 in which said sulfonium betaine compound comprises 3-S-isothiuronium propane sulfonate.
15. The bath as defined in claim 1 in which said sulfonium betaine compound is selected from the group consisting of N,N'-dimethyl-3-S-isothiuronium propane sulfonate, N,N'-diethyl-3-S-isothiuronium propane sulfonate, N,N'-dihydroxymethy1-3-S-isothiuronium propane sulfonate, N,N'-diisopropy1-3-S-isothiuronium propane sulfonate, N,N,N',N'-tetramethyl-3-S-isothiuronium propare sulfonate, N,N,N'-trimethyl-3-S-isothiuronium propane sulfonate, 2-S-isothiuronium ethane sulfonate, 3-S-isothiuronium propane-2-o1 sulfonate and mixtures thereof.
16. The bath as defined in claim 1 further containing a supplemental stabilizer agent selected from the group consisting of lead ions, cadmium ions, tin ions, bismuth ions, antimony ions, zinc ions, cyanide ions, thiocyanate ions, and mixtures thereof present in combination with said sulfonium betaine compound in an amount below that at which the rate of nickel deposition is reduced to an undesirable magnitude.
17. The bath as defined in claim 1 in which said nickel ions are present in an amount of about 1 to about 15 g/l, said hypophosphite ions are present in an amount of about 2 to about 40 g/l, said sulfonium betaine compound is present in an amount of at least about 1 up to about 200 micro mol/l, said bath further including a complexing agent present in an amount up to about 200 g/l, a buffering agent present in an amount up to about 30 g/l and a wetting agent present in an amount up to about 1 g/l.
18. A process for chemically depositing nickel on a substrate which comprises the steps of contacting a substrate to be plated with an electroless nickel bath as defined in claim 1 for a period of time sufficient to deposit nickel on the substrate to the desired thickness.
19. The process as defined in claim 18 in which said electroless nickel bath further contains a supplemental stabilizer agent selected from the group consisting of lead ions, cadmium ions, tin ions, bismuth ions, antimony ions, zinc ions, cyanide ions, thiocyanate ions, and mixtures thereof present in combination with said sulfonium betaine compound in an amount below that at which the rate of nickel deposition is reduced to an undesireable magnitude.
20. A process for rejuvenating an aqueous electroless nickel bath which has been rendered inoperative due to the presence of an excessive concentration of supplemental stabilizing agents therein which comprises the steps of adding to said bath a sulfonium betaine compound corresponding to the structural formula:
Wherein:
R1, R2, R3 and R4 are the same or different and are H, C1-C6 alkyl radicals, C1-C6 hydroxy alkyl radicals, R is the same or different and is H or OH, and n is an integer of from 1 to 5, as well as mixtures thereof;
in an amount sufficient to rejuvenate and restore the plating activity of said bath.
Wherein:
R1, R2, R3 and R4 are the same or different and are H, C1-C6 alkyl radicals, C1-C6 hydroxy alkyl radicals, R is the same or different and is H or OH, and n is an integer of from 1 to 5, as well as mixtures thereof;
in an amount sufficient to rejuvenate and restore the plating activity of said bath.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US583,759 | 1984-03-05 | ||
| US06/583,759 US4483711A (en) | 1983-06-17 | 1984-03-05 | Aqueous electroless nickel plating bath and process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1225501A true CA1225501A (en) | 1987-08-18 |
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ID=24334446
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000458433A Expired CA1225501A (en) | 1984-03-05 | 1984-07-09 | Aqueous electroless nickel plating bath and process |
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| Country | Link |
|---|---|
| JP (1) | JPS6141774A (en) |
| AU (1) | AU555641B2 (en) |
| CA (1) | CA1225501A (en) |
| DE (1) | DE3421646A1 (en) |
| ES (1) | ES8506109A1 (en) |
| FR (1) | FR2560609B1 (en) |
| GB (1) | GB2155041B (en) |
| IT (1) | IT1181810B (en) |
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| US4983428A (en) * | 1988-06-09 | 1991-01-08 | United Technologies Corporation | Ethylenethiourea wear resistant electroless nickel-boron coating compositions |
| ES2027496A6 (en) * | 1989-10-12 | 1992-06-01 | Enthone | Plating aluminium |
| DE102004047423C5 (en) * | 2004-09-28 | 2011-04-21 | AHC-Oberflächentechnik GmbH & Co. OHG | Externally applied Nickel alloy and its use |
| KR101310256B1 (en) | 2011-06-28 | 2013-09-23 | 삼성전기주식회사 | Electroless plated layers of printed circuit board and method for preparing the same |
| EP2551375A1 (en) * | 2011-07-26 | 2013-01-30 | Atotech Deutschland GmbH | Electroless nickel plating bath composition |
| US11685999B2 (en) | 2014-06-02 | 2023-06-27 | Macdermid Acumen, Inc. | Aqueous electroless nickel plating bath and method of using the same |
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| DE1001078B (en) * | 1953-08-13 | 1957-01-17 | Dehydag Gmbh | Galvanic baths for the production of metal coatings |
| US3489576A (en) * | 1966-08-04 | 1970-01-13 | Gen Motors Corp | Chemical nickel plating |
| US3515564A (en) * | 1968-05-27 | 1970-06-02 | Allied Res Prod Inc | Stabilization of electroless plating solutions |
-
1984
- 1984-06-04 AU AU29035/84A patent/AU555641B2/en not_active Ceased
- 1984-06-08 GB GB08414601A patent/GB2155041B/en not_active Expired
- 1984-06-09 DE DE19843421646 patent/DE3421646A1/en active Granted
- 1984-06-18 JP JP12499584A patent/JPS6141774A/en active Granted
- 1984-07-09 CA CA000458433A patent/CA1225501A/en not_active Expired
- 1984-07-10 FR FR8410971A patent/FR2560609B1/en not_active Expired
- 1984-07-27 IT IT48657/84A patent/IT1181810B/en active
- 1984-07-27 ES ES534703A patent/ES8506109A1/en not_active Expired
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| FR2560609B1 (en) | 1987-03-27 |
| AU2903584A (en) | 1985-09-12 |
| GB2155041B (en) | 1987-06-03 |
| GB2155041A (en) | 1985-09-18 |
| IT8448657A0 (en) | 1984-07-27 |
| ES534703A0 (en) | 1985-06-16 |
| ES8506109A1 (en) | 1985-06-16 |
| DE3421646C2 (en) | 1987-01-02 |
| JPH0144790B2 (en) | 1989-09-29 |
| FR2560609A1 (en) | 1985-09-06 |
| AU555641B2 (en) | 1986-10-02 |
| GB8414601D0 (en) | 1984-07-11 |
| JPS6141774A (en) | 1986-02-28 |
| DE3421646A1 (en) | 1985-09-05 |
| IT1181810B (en) | 1987-09-30 |
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