Classifications

• • 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
  • C23C18/1601—Process or apparatus
  • C23C18/1617—Purification and regeneration of coating baths
• • 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
  • C23C18/38—Coating with copper
  • C23C18/40—Coating with copper using reducing agents
  • C23C18/405—Formaldehyde

Definitions

• Cupric nitrate About 1 to saturation.
• Formaldehyde methanol reaction product comprising primarily CH OCH -OCH About 1-s0. Formalin About 15-75. Methanol, concentrated About 1-83.
• the formaldehyde-methanol reaction product comprising primarily the pleasant smelling methylal, i.e.
• This invention relates to electroless copper plating and more particularly to a new and improved method for replenishing depleted or exhausted chemical reduction copper plating baths without having to remove a material amount of liquid plating solution from the bath prior to, during or after the replenishment, except for those amounts of liquid bath solution removed by drag out and evaporation, and for considerably reducing the odor of formaldehyde in the concentrate solution and in the plating bath solution. Additionally this invention is concerned with new and improved concentrate solutions for replenishing depleted or exhausted chemical reduction copper plating baths or from mixing together with another concentrate composition and water in making up new plating baths.
• the substantially no bail-out, formaldehyde odorreducing method of the present invention for replenishing depleted or spent electroless alkaline aqueous copper plating baths involves adding to the depleted alkaline plating bath solution comprising cupric nitrate, formaldehyde and a complexing agent for the cupric ions a replenisher concentrate solution containing the following constituents in proportions within the proportion ranges hereafter specified:
• Cupric nitrate About 1 to saturation. Formalin About 15-75. Methanol, concentrated About 1-84.
• a formaldehyde-methanol reaction product comprising primarily methylal, i.e. CH --OCH OCH
• the formalin specified immediately supra and elsewhere herein is an aqueous formaldehyde solution ordinarily of 37% formaldehyde concentration and is readily obtained in commerce.
• the formaldehyde-methanol reaction product comprising primarily is present in the concentrate solution in an amount which is sufficient to reduce considerably the irritating formaldehyde odor of the electroless, i.e. chemical reduction, alkaline copper plating bath containing formaldehyde as reducing agent.
• the formaldehyde-methanol reaction product comprising primarily CH -O-CH O-CH is formed in situ in the replenisher concentrate solution or other concentrate solution herein by bringing together or admixing the concentrated methanol and formalin in the presence of the cupric nitrate usually at room temperature and for at least a time suflicient to obtain the formaldehyde-methanol reaction product, such reaction time being 1 hour or more.
• the replenishment of the depleted electroless copper plating baths in accordance with this invention constitutes a considerable improvement by reasons of: (1) little or no bail-out of plating bath solution required due to the relatively small replenishment volume required for bath replenishment; (2) usually total elimination of a detectable odor of formaldehyde in the plating bath and concentrate solution, and at most only a nonobjectionable low odor of formaldehyde in both the plating bath and concentrate solution; (3) requiring only relatively small or minimum replenishment volume in at least the preferred embodiment for replenishing the depleted plating bath; (4) loss of valuable plating chemicals avoided due to elimination of the bail-out requirement; and (5) no shut-down of the automatic plating line required for bail-out'of plating bath.
• the time of the reaction between the formaldehyde and methanol in the presence of the cupric nitrate to form the formaldehyde-methanol reaction product containing primarily the pleasant smelling methylal is 1 hour or more as is disclosed supra and may extend for several days, for instance to about 14 days.
• the reaction temperature for such reaction is usually room temperature or normal temperature. However, elevated temperatures above room temperature can be employed for the reaction although the elevated temperatures are not preferred. Thus the reaction temperature can be in the range of room temperature to about 120 F.
• the pH of the reaction solution is on the acid side of pH 7, i.e. below 7, and preferably the pH is in the range of about 1.5 to about 2.5. Maintenance of pH is effected, if required, by addition of small amounts of dilute nitric acid or sulfuric acid solution.
• formaldehyde-methanol reaction product as comprising primarily the CH OCH -OCH i.e. methylal, means that the formaldehyde-methanol reaction product contains in excess of 50% by weight of the methylal, i.e. CH OCH -OCH
• the formaldehyde-methanol reaction product may also contain a minor or small amount of the compounds CH OCH OH and CH O (CI-I 0 H wherein n is a positive integer of 1 or more, the two lastmentioned compounds when present being in lesser amount than the methylal.
• cupric nitrate takes up or absorbs most, if not all, of the free water in the replenisher and other concentrate of this invention resulting in the concentrates being anhydrous or substantially anhydrous. And this is believed to occur even though H O may be added to the formulation.
• the formaldehyde-methanol reaction product is usually added to the electroless or chemical reduction copper plating bath to be replenished as a constituent of the relatively high cupric ion content, replenisher concentrate solution.
• the replenisher concentrate solution also contains, in addition to the cupric nitrate and formaldehydemeth'anol reaction product, unreacted formaldehyde and unreacted methanol.
• the concentrate solution of this invention in its broader aspects, comprises the following constituents within the proportion ranges set forth below:
• Cupric nitrate About 1 tosaturation. Formalin About l5-7S. Methanol, concentrated About 1-84.
• formaldehyde-methanol reaction product comprising primarily the methylal
• the formaldehyde-methanol reaction product comprising primarily the methylal is prepared or formed in a'tu in the concentrate solution under the reaction conditions previously disclosed herein, and such formaldehyde-methanol reaction product is ordinarily present in the concentrate solution herein in amount of about 150% by weight of the concentrate solution.
• the concentrated methanol and formalin are brought together or admixed in the presence of the cupric nitrate in any sequence and in any suitable vessel or container, in the formation of the formaldehyde-methanol reaction product.
• the concentrated methanol can be added to the formalin and cupric nitrate, the formalin added to the concentrated methanol and cupric nitrate, the concentrated methanol added to the formalin followed by the addition of the cupric nitrate to the resulting admixture, the formalin added to the concentrated methanol followed by the addition of the cupric nitrate to the resulting admixture, or such materials can be admixed in any other sequence. Additional agitating or mixing besides that obtained merely by adding the one or more materials to the other is not required but may be effected, if desired.
• the formaldehyde-methanol reaction product comprises primarily methylal, i.e. CH OCH O--OH
• the methylal is obtained only when formaldehyde and concentrated methanol are brought together or mixed in the presence of the cupric nitrate, the nitrate anions of the cupric nitrate apparently catalyzing the reaction.
• the reactions for the formation of the methylal are set forth in the following equations:
• the formaldehyde-methanol reaction product which comprises primarily methylal as hereinbefore disclosed, be pre-formed prior to introduction into the depleted chemical reduction copper plating bath inasmuch as no formaldehyde-methanol reaction product is formed in the plating bath solution per se or, if formed, is not formed therein in sufficient quantity to mask or reduce the formaldehyde odor of the plating bath to an unobjectionable low level.
• the relatively large quantity of water present in the plating bath solution which is a dilute solution, as contrasted with the relatively small amount of water or no Water present in the replenisher concentrate solution of this invention, which is a concentrated solution, wherein the formaldehyde-methanol reaction product is usually formed.
• the concentrate solution of this invention hereafter specified will usually contain the following constituents in the proportions within the proportion ranges hereafter specified:
• Cupric nitrate About 1-30.
• Formaldehyde-methanol reaction product comprising primarily CH OOH OCH About 1-25.
• Formalin about 15-75.
• Methanol, concentrated about 1-83.
• Formalin is an aqueous solution of 37% formaldehyde concentration readily obtainable in commerce.
• the concentrated methanol is of 90-100% methanol concentration.
• the concentrate solution of this invention is usually added to the depleted plating bath to replenish its constituents in combination with another replenisher concentrate solution, which is usually separately added to the depleted bath, in a volume ratio of the invention concentrate solution to the other replenisher concentrate solution within the volume ratio range of about 11% to about 1:2 respectively.
• the last-mentioned replenisher concentrate will usually contain the following constituents within the proportion ranges hereinafter specified:
• the other replenisher concentrate solution which is mixed together with the cupric nitrate-and formaldehydemethanol reaction product-containing concentrate solution of this invention and water in making up a new chemical reduction copper plating solution, will usually contain the following constituents within the proportion ranges specified:
• a complexing agent such as Rochelle salt
• the exact amounts of these constituents remaining in a depleted bath will of course vary depending on the length of time the bath has been used for plating, the number of articles to be plated put through the bath during that time, and the extent of plating required on different articles.
• the pH of the depleted plating baths is usually in the range of -13, and the pH of the plating baths after replenishing and of the newly made-up plating baths is usually in the range of 10-13, preferably 1212.6.
• the concentrate solution of this invention preferably contains the following constituents within the proportion ranges specified:
• Cupric nitrate About 17-21.
• Formaldehyde-methanol reaction product comprising primarily CH OCH OCH About 5-10.
• Formalin about 60-70.
• Methanol (%-100%) About 5-15.
• the methanol is a concentrated methanol of 90-100% methanol concentration.
• Example I The following concentrate solutions were utilized to replenish a depleted chemical reduction copper plating solution, and also to make-up a new chemical reduction copper plating solution or bath, as indicated and in accordance with the present invention, in the manner hereinafter set forth.
• the Concentrate A Solution is a concentrate of the present invention.
• the Concentrate A Solution set forth immediately supra was prepared by admixing at room temperature the Cu NO -3H O,' the Formalin and the methanol in the proportions, by weight, of 10.0% of the Cu( NO -3H O, 55% of the Formalin and 35% of the methanol.
• the Formalin and methanol were maintained together in admixture in the presence of the cupric nitrate for a reaction time of 14 days to form in situ in the concentrate solution the formaldehyde-methanol reaction product containing primarily the methylal, e.e. CH --O-CH OCH CONC-ENTRA'I E B SOLUTION Percent by Weight H O 84.0 NaOH 5.0 Na CO 1.0 Rochelle Salt 10.0
• the Concentrate B Solution and Concentrate C Solution set forth immediately supra were prepared by admixing the constituents specified at room temperature in the proportions specified.
• the Concentrate A Solution and the chemical reduction copper plating solution contained only a non-objectionable low odor of formaldehyde due to the formaldehyde odor masking effect of the formaldehyde-methanol reaction product.
• Rochelle salt is the preferred cupric ion complexer in the concentrate compositions and plating baths provided by this invention
• other complexing agents are utilizable therein in place of the Rochelle salt such as, for example, ,EDTA or amines.
• Example III Percent by weight Cu(NO -3H O 10.0 Formalin 8.0 Methanol methanol concentration) 28.8 Formaldehyde-methanol reaction product comprising primarily methylal 35.3 H O 17.9
• Example IV Percent by weigh CU(NO3)Z3HZO 5.0 Formalin 17.5 Methanol (95%) 65.0 Formaldehyde-methanol reaction product comprising primarily methylal
• concentration solution set forth immediately supra is prepared by mixing together at room temperature the Cu (NO -3H O, the formalin, and methanol in the pro portions, by weight, of 5% of the Cu(NO -3H O, 25% of the formalin and 70% of the methanol.
• the formalin and methanol are maintained together in the presence of the cupric nitrate for a suflicieat reaction time to form in situ in the solution the formaldehyde-methanol reaction product comprising primarily the methylal.
• Cupric nitrate About 1 to saturation. Formalin About 15-75. Methanol, concentrated About 1-84.
• formaldehyde odor of the electroless copper plating bath solution of a formaldehyde-methanol reaction product comprising primarily CH -O-CH OCH the formaldehyde-methanol reaction product being formed in situ in the concentrate solution as a constituent thereof by bringing together the concentrated methanol and Formalin in the presence of cupric nitrate for a time sufficient to obtain said formaldehyde-methanol reaction product.
• reaction time is in the range of one hour to about fourteen days.
• cupric ion complexing agent in the depleted plating bath is Rochelle salt and the other complexing agent-containing replenisher concentrate contains Rochelle salt as the cupric ion complexing agent, and an alkali metal hydroxide and an alkali metal carbonate as the alkaline material.
• a concentrate solution for use in chemical reduction copper plating solutions comprising the following constituents in proportions within the proportion ranges hereafter specified:
• Cupric nitrate About 1 to saturation. Formalin About 15-75. Methanol, concentrated About 1-84.
• a formaldehyde-methanol reaction product comprising 10 primarily CH -O-CH OCH the formaldehydemethanol reaction product being formed in situ in the concentrate solution as a constituent thereof by bringing together the concentrated methanol and formalin in the presence of the cupric nitrate for a time sufficient to obtain said formaldehyde-methanol reaction product.
• reaction time is in the range of one hour to about fourteen days.

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Cited By (2)

• 1972
  • 1972-02-04 US US00223690A patent/US3736156A/en not_active Expired - Lifetime
  • 1972-07-17 JP JP47070867A patent/JPS4839250A/ja active Pending

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