CA1181715A - Composition and process for high speed bright silver plating - Google Patents
Composition and process for high speed bright silver platingInfo
- Publication number
- CA1181715A CA1181715A CA000388152A CA388152A CA1181715A CA 1181715 A CA1181715 A CA 1181715A CA 000388152 A CA000388152 A CA 000388152A CA 388152 A CA388152 A CA 388152A CA 1181715 A CA1181715 A CA 1181715A
- Authority
- CA
- Canada
- Prior art keywords
- bath
- silver
- alkali metal
- electroplating bath
- antimony
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 229910052709 silver Inorganic materials 0.000 title claims abstract description 38
- 239000004332 silver Substances 0.000 title claims abstract description 38
- 239000000203 mixture Substances 0.000 title claims abstract description 8
- 238000000034 method Methods 0.000 title claims abstract description 5
- 238000007747 plating Methods 0.000 title description 9
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 28
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052787 antimony Inorganic materials 0.000 claims abstract description 19
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 claims abstract description 19
- -1 alkali metal silver cyanide Chemical class 0.000 claims abstract description 17
- 150000001340 alkali metals Chemical class 0.000 claims abstract description 15
- 229940000207 selenious acid Drugs 0.000 claims abstract description 11
- MCAHWIHFGHIESP-UHFFFAOYSA-N selenous acid Chemical compound O[Se](O)=O MCAHWIHFGHIESP-UHFFFAOYSA-N 0.000 claims abstract description 11
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000004327 boric acid Substances 0.000 claims abstract description 9
- 229940098221 silver cyanide Drugs 0.000 claims abstract description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims abstract description 4
- 238000004519 manufacturing process Methods 0.000 claims abstract description 3
- 150000003839 salts Chemical class 0.000 claims abstract description 3
- 229940082569 selenite Drugs 0.000 claims abstract description 3
- MCAHWIHFGHIESP-UHFFFAOYSA-L selenite(2-) Chemical compound [O-][Se]([O-])=O MCAHWIHFGHIESP-UHFFFAOYSA-L 0.000 claims abstract description 3
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 claims description 23
- 238000009713 electroplating Methods 0.000 claims description 23
- 239000011669 selenium Substances 0.000 claims description 21
- 229910052711 selenium Inorganic materials 0.000 claims description 21
- 235000010338 boric acid Nutrition 0.000 claims description 10
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 claims description 7
- 235000015165 citric acid Nutrition 0.000 claims description 7
- 239000002659 electrodeposit Substances 0.000 claims description 6
- HKSGQTYSSZOJOA-UHFFFAOYSA-N potassium argentocyanide Chemical compound [K+].[Ag+].N#[C-].N#[C-] HKSGQTYSSZOJOA-UHFFFAOYSA-N 0.000 claims description 6
- 239000001508 potassium citrate Substances 0.000 claims description 6
- 229960002635 potassium citrate Drugs 0.000 claims description 6
- QEEAPRPFLLJWCF-UHFFFAOYSA-K potassium citrate (anhydrous) Chemical compound [K+].[K+].[K+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O QEEAPRPFLLJWCF-UHFFFAOYSA-K 0.000 claims description 6
- 235000011082 potassium citrates Nutrition 0.000 claims description 6
- 150000003863 ammonium salts Chemical class 0.000 claims description 5
- 229940065287 selenium compound Drugs 0.000 claims description 5
- 230000000694 effects Effects 0.000 claims description 4
- IIQJBVZYLIIMND-UHFFFAOYSA-J potassium;antimony(3+);2,3-dihydroxybutanedioate Chemical group [K+].[Sb+3].[O-]C(=O)C(O)C(O)C([O-])=O.[O-]C(=O)C(O)C(O)C([O-])=O IIQJBVZYLIIMND-UHFFFAOYSA-J 0.000 claims description 4
- 150000003343 selenium compounds Chemical class 0.000 claims description 4
- 229960003975 potassium Drugs 0.000 claims description 3
- 229910052700 potassium Inorganic materials 0.000 claims description 3
- 239000011591 potassium Substances 0.000 claims description 3
- LFAGQMCIGQNPJG-UHFFFAOYSA-N silver cyanide Chemical compound [Ag+].N#[C-] LFAGQMCIGQNPJG-UHFFFAOYSA-N 0.000 claims description 3
- 239000000758 substrate Substances 0.000 claims description 3
- 125000005619 boric acid group Chemical class 0.000 claims description 2
- 230000003139 buffering effect Effects 0.000 claims description 2
- 150000001875 compounds Chemical class 0.000 claims description 2
- WUUHFRRPHJEEKV-UHFFFAOYSA-N tripotassium borate Chemical compound [K+].[K+].[K+].[O-]B([O-])[O-] WUUHFRRPHJEEKV-UHFFFAOYSA-N 0.000 claims description 2
- PXRKCOCTEMYUEG-UHFFFAOYSA-N 5-aminoisoindole-1,3-dione Chemical class NC1=CC=C2C(=O)NC(=O)C2=C1 PXRKCOCTEMYUEG-UHFFFAOYSA-N 0.000 claims 2
- 150000001412 amines Chemical class 0.000 claims 1
- 235000002639 sodium chloride Nutrition 0.000 claims 1
- 239000002253 acid Substances 0.000 abstract description 6
- 150000007513 acids Chemical class 0.000 abstract description 4
- 229910052751 metal Inorganic materials 0.000 abstract description 2
- 239000002184 metal Substances 0.000 abstract description 2
- 239000003513 alkali Substances 0.000 abstract 1
- 235000011649 selenium Nutrition 0.000 description 16
- 229940091258 selenium supplement Drugs 0.000 description 16
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 4
- 238000009472 formulation Methods 0.000 description 4
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 2
- 229910000881 Cu alloy Inorganic materials 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 150000001450 anions Chemical class 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 description 1
- 229910003597 H2SeO3 Inorganic materials 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- GOEMFERYUOQIHS-UHFFFAOYSA-N [NH4+].[SeH-] Chemical compound [NH4+].[SeH-] GOEMFERYUOQIHS-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 229940075103 antimony Drugs 0.000 description 1
- 229940058905 antimony compound for treatment of leishmaniasis and trypanosomiasis Drugs 0.000 description 1
- 150000001463 antimony compounds Chemical class 0.000 description 1
- 229910000410 antimony oxide Inorganic materials 0.000 description 1
- AUJJPYKPIQVRDH-UHFFFAOYSA-N antimony potassium Chemical compound [K].[Sb] AUJJPYKPIQVRDH-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- IBGIKQMUVKJVCW-UHFFFAOYSA-N diazanium;selenite Chemical compound [NH4+].[NH4+].[O-][Se]([O-])=O IBGIKQMUVKJVCW-UHFFFAOYSA-N 0.000 description 1
- RNGFNLJMTFPHBS-UHFFFAOYSA-L dipotassium;selenite Chemical compound [K+].[K+].[O-][Se]([O-])=O RNGFNLJMTFPHBS-UHFFFAOYSA-L 0.000 description 1
- 238000004070 electrodeposition Methods 0.000 description 1
- 229940037395 electrolytes Drugs 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- VTRUBDSFZJNXHI-UHFFFAOYSA-N oxoantimony Chemical compound [Sb]=O VTRUBDSFZJNXHI-UHFFFAOYSA-N 0.000 description 1
- NNFCIKHAZHQZJG-UHFFFAOYSA-N potassium cyanide Chemical compound [K+].N#[C-] NNFCIKHAZHQZJG-UHFFFAOYSA-N 0.000 description 1
- 150000003346 selenoethers Chemical class 0.000 description 1
- NGBNXJUWQPLNGM-UHFFFAOYSA-N silver;azane Chemical compound N.[Ag+] NGBNXJUWQPLNGM-UHFFFAOYSA-N 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/56—Electroplating: Baths therefor from solutions of alloys
- C25D3/64—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of silver
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/46—Electroplating: Baths therefor from solutions of silver
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electroplating And Plating Baths Therefor (AREA)
- Cosmetics (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An electrolytic bath for the production of mirror bright silver deposits comprising an alkali metal silver cyanide as the source of silver; boric acid, citric acid, alkali or ammonium metal salts of such acids, as well as mixtures thereof;
selenious acid or alkali metal selenite; and, in certain preferred baths, antimony in the form Or an alkali metal carboxylic acid salt. The bath is designed to be operated at high current densities of from 200 to 5000 ASF, i.e. about 20 to 500 ASD. The process of utilizing such an electrolytic bath is also disclosed and claimed.
An electrolytic bath for the production of mirror bright silver deposits comprising an alkali metal silver cyanide as the source of silver; boric acid, citric acid, alkali or ammonium metal salts of such acids, as well as mixtures thereof;
selenious acid or alkali metal selenite; and, in certain preferred baths, antimony in the form Or an alkali metal carboxylic acid salt. The bath is designed to be operated at high current densities of from 200 to 5000 ASF, i.e. about 20 to 500 ASD. The process of utilizing such an electrolytic bath is also disclosed and claimed.
Description
3L7~i Although the electrodeposition oE silver from a variety of plating baths has been disclosed in the art, there is still a need for baths capable of functioning e Lectively for high speed ~rignt silver plating.
~he present invention relates to new and improved electroplating haths, utili~ing an alkali metal silver cyanide as ~he source of the silv~r, for high speed silver plating.
More particula ly, the invention pertains to particular electro-plating baths wnerein mirror bright silver plating is achieved at current densities up to 5000 ASF.
As is well kno~n in the art, silver cyanide plating baths have been employed for many years. ~any efforta also have jbeen made to develop noncyanid~ or low cyanide silver plating ,baths. See, for example, U.S. Patents 4,155,817 (Fletcher~
and 4,024,031 (Lerner); where the latter patent is directed lto an ele_troplating bath with a low silver content, which is essentially at a neutral pH and operates substantially without 'free cyanides.
The patent to Fletch~r (No. 4,155,817) also contains a dstailed description of the silver plating; and when this is considered along with disclosures in the prior art cited in this patent as well as in the Lerner patent, one obtains an excellent bac~.ground in the historical silver plating art as well as the numProus endeavors to develop improved electropla~ing baths for a variety of commercial advantages such as high speed deposition and high quality, bright silver deposits.
':
`'''~ :
7~
The pa-tent to Fletcher discloses, inter alia, the use of a divalent (-2) selenium complex together wi-th an elec-trolyte bath having a free cyanide content of less than 1.5 g/l. the use of alkali metal selenium compounds as brighte ners is also dislcosed in U.S. Patent No. 2,613,179 (Wolfson) and U.S. Patent No. ~,121,982 (Fletcher). Wolfson discloses, inter alia, that the use o-f a selenite of an alkali metal together with alkali metal cyanides and nitrates results in the formation of a high speed bright silver deposit because of 10 the presence of nitrate (100-150 g/l) and potassium selenite up to 1.0 g/l. Wolfson states that the presence of the nitra-tes permits him to plate up to 100 ASF (10 ASD) and that without the nitrates this current density could not be achieved.
Another relevant patent for the present purposes is U.S. Patent No. 2,735,808 (Greenspan) which teaches that the use of a glycerol complex and potassium cyanide are necessary to obtain bright silver deposits from an electroplating, which is tartrate-free. Greenspan states that his baths must be tartrate-free when using the glycerol complex of antimony.
Furthermore, in U.SO Patent No. 2,777,810 (Ostrow) there is a disclosure that divalent (-2) selenium compound in the presence of antimony compounds and free cyanide gives bright deposits up to 100 AS~.
It should be further noted that when divalent or hexavalent selenium compounds are used, either by themselves or in combination with antimony, they do not give bright deposits over the wide current density range, i.e. 200 to 5000 ASF.
l7~
~ IO~
The present invention relates to a particular elec-troplating bath for producing mirror bright silver deposits.
More particularly selenium, or combinations of selenium and antimony, are added as additives. The selenium component may be any bath soluble selenium compound in which the selenium is tetravalent, i.e., has a valence of 4, and in which the anions and/or cations associated with the tetravalent selenium do not have an adverse effect on either the electroplating bath or the silver electrodeposit produced~ Generally, it is added as either selenious acid or as an alkali metal or ammo-nium selenite. Similarly, the antimony component may be any bath soluble compound or complex of antimony in which the anions and/or cations associated with the antimony do not have an adverse effect on either the electroplating bath or the silver electrodeposit produced~ Desirably, the antimony component is employed in the form o~ its complex with an alkali metal carboxylic acid salt~ With selenium or both antimony and selenium present a mirror bright silver deposit results.
The source of silver is an alkali metal or ammonium or amine silver cyanide. Other essential components are boric acid or citric acid, or the alkali metal or ammonium salts of such acids. Generally, for operations at current densi-ties above about 500 ASF., both boric and citric acids are employed: and most preferably the acids are utilized in the form of their alkali metal salts.
In general, the electroplating bath is substantially free of free cyanide. It is ~ormulated to have a pH within the range of about 7.0 to about 9.0, and it will be operated within a temperature range of about 20 to about 80C and at a high current density of up to about 5000 A~F.
7:~
The silver will be present in the bath in an amount which is at least sufficient to produce a smooth electrodeposit of silver on the substrate. The citrate and borate will be present in amounts which are at least sufficient, either alone or in combination, to effect buffering of the bath to maintain it within the desired operable pH range. The selenium or sele-nium and antimony will be present in amounts which are at least sufficient to produce a bright electrodeposit of silver~
~ NVENTION
As previously set forth, the goal of the present invention is to provide an electroplating bath, which can be operated at high speed up to 5000 ASF to produce a mirror bright silver deposit on various substrates or workpieces such as copper alloys, nickel alloys, and the like.
The source of the silver in the bath is desirably an alkali metal or ammonium silver cyanideO Although ammo-nium, potassium, sodium, and lithium silver cyanides may be employed, the most preferred feed is potassium silver cyanide.
It will be further understood that for most purposes of the present invention wherever the use of an alkali metal is pres-cribed, potassium is especially preferred unless otherwise indicated.
The amount of silver, derived from the potassium silver cyanide, generally ranges from about 20 to 120 g/l, preferably from about 30 to 100 g/l.
The citric acid or its alkali metal or ammonium salt, preferably potassium citrate, is employed in amounts generally ranginy from about 50 to 200 g/l, preferably 75 to 140 g/l.
. ~ _ s The boric acid or its alkali metal or ammonium salt, which for operations at current densities above about 500 ASF, is employed not in place of the citric acid or its alkali metal salt but rather iTl conjunction with the citric acid, is utilized in amounts generally ranginy frorn about 10 to 50 g/l, preferably 20 -to 40 g/l. Again, the preferred boric acid component is its potassium metal salt, namely po-tassium borate.
The selenium component is desirably selenious acid (H2SeC3) or an alkali metal or ammonium selenium salt wherein the valence is 4 (i.e. tetravalent) rather than divalent as prescribed in the prior art teaching described above. The selenium component is utilized in the bath in amounts generally ranging from about 2.0 to 5 g/l, and preferably about 2.5 to 5 g/l. In forming the alkali metal salt, the selenious acid is merely neutralized with an alkali metal material such as the hydroxide. Thus, for example, potassium hydroxide may be readily employed to neutralize the selenious acid. Based on selenium metal alone, the bath will generally contain 1 to 3 g/l, and preferably 1.5 to 3 g~l.
For certair~ purposes of this invention an antimony component is also employed in the bath to ensure the deposi-tion of mirror bright silver depositsO Preferably the antimony is used in the form of an alkali metal carboxilic acid complex, and most preferably as potassium antimony tartrate. Other complexes that could be employed ln the present invention include the antimony potassium glycera-te, antimony oxide dissolved in other carboxilic acids, and the like. The amount of antimony metal used in the bath will ranqe from about 0,5 to 2.5 g/l, preferably 1.0 to 1.5 g/l.
It is an important feature of the present invention that the resulting electroplating bath be substantially free of free cyanide, which is another distinction between the present invention and the known baths of the prior art. By substantially free of cyanide one means a cyanide ion content of less than ak~ut, 1.5 g/l, and preferably less than about 0.25 g/l. Furthermore, the electroplating bath is also free of nitrate ions.
A preerred bath composition according to the present invention is set forth below:
~ 9~ Concentration, q~l Silver as potassium silver cyanide 30-100 Potassium Citrate 75-140 Potassium Borate 20- 40 H2SeO3 [neutralized with KOHJ 2- 5 Antimony ras potassium antimony tartrate] 1-1.5 7~
The pH of the bath may range from about 7.0 to 9.0 preferabl~ 7.5 to 8.5, while the temperature is maintained with the range of 20 to 80C, preferably about 40 to 70C.
As described above, the current density may be relatively high, .io e. up to 5000 ASE'. Although the current density employed may be as low as 100, in order to ensure the pro-duction of mirror bright silver deposits, the densities will generally range from about 200 to 5000 ASF, i~e. about 20 to 530 A/dm ~ASD).
The invention will be more fully understood by reference to the following illustrative embodiments.
EXAMPLE I
An electrolytic bath was prepared having the following formulation:
.Silver as potassium silver cyanide - 60 g~l Potassium citrate - 100 ~/1 Boric Acid - 30 g/l Selenium as Selenious acid - 2.0 g/l This electrolyte a-t 70C deposited mirror bright plates when selectively plated at current densities between 1000 to 4000 ASF on copper alloy~ The pH of the bath was 8.
The use of the same formulation given in Example I, but operated at 50C, resulted in mirror bright deposits between 400 and 1500 ASF~
7~
EXAM~LE 3 The same formulation given in Example I, but operated at 30C, plated selectively mirror bright deposits between 200 and 400 ASF.
The procedure of Example 3 is repeated except that the potassium citrate is omitted from the bath and similar results are obtained.
The procedure of Example 3 is repeated except that the bGric acid is omitted from the bath and similar results are obtained.
An electrolytic bath was prepared having the follo-wing formulation:
Silver as potassium silver cyanide - 80 g/l Potassium citrate - 75 g/l Boric acid - 20 g/l Selenium as selenious acid -2.0 g/l Antimony as potassium antimony tartrate -1.5 g/l This electrolyte when operated at 60C selectively plated mirror bright silver deposits from 1000 to 5000 ASF.
The above data demonstrates that the electrolytic baths of the present invention give outstanding silver deposits.
By way of comparison, it was found that when the selenious acid or salt of the illustrative embodiment was substituted with a selenide (where the selenium is divalent) or selenate (where the selenium is hexavalent) the thus fo~med electro-lytes did not give mirror bright or bright silver deposits when plated selectively at a current density of over 500 ASF.
ri While certain Eeatures of the present invention have been illustrated above, it will be understood that the invention is obviously subject to variations and modiiications without departiny from the broader aspects of the invention.
~he present invention relates to new and improved electroplating haths, utili~ing an alkali metal silver cyanide as ~he source of the silv~r, for high speed silver plating.
More particula ly, the invention pertains to particular electro-plating baths wnerein mirror bright silver plating is achieved at current densities up to 5000 ASF.
As is well kno~n in the art, silver cyanide plating baths have been employed for many years. ~any efforta also have jbeen made to develop noncyanid~ or low cyanide silver plating ,baths. See, for example, U.S. Patents 4,155,817 (Fletcher~
and 4,024,031 (Lerner); where the latter patent is directed lto an ele_troplating bath with a low silver content, which is essentially at a neutral pH and operates substantially without 'free cyanides.
The patent to Fletch~r (No. 4,155,817) also contains a dstailed description of the silver plating; and when this is considered along with disclosures in the prior art cited in this patent as well as in the Lerner patent, one obtains an excellent bac~.ground in the historical silver plating art as well as the numProus endeavors to develop improved electropla~ing baths for a variety of commercial advantages such as high speed deposition and high quality, bright silver deposits.
':
`'''~ :
7~
The pa-tent to Fletcher discloses, inter alia, the use of a divalent (-2) selenium complex together wi-th an elec-trolyte bath having a free cyanide content of less than 1.5 g/l. the use of alkali metal selenium compounds as brighte ners is also dislcosed in U.S. Patent No. 2,613,179 (Wolfson) and U.S. Patent No. ~,121,982 (Fletcher). Wolfson discloses, inter alia, that the use o-f a selenite of an alkali metal together with alkali metal cyanides and nitrates results in the formation of a high speed bright silver deposit because of 10 the presence of nitrate (100-150 g/l) and potassium selenite up to 1.0 g/l. Wolfson states that the presence of the nitra-tes permits him to plate up to 100 ASF (10 ASD) and that without the nitrates this current density could not be achieved.
Another relevant patent for the present purposes is U.S. Patent No. 2,735,808 (Greenspan) which teaches that the use of a glycerol complex and potassium cyanide are necessary to obtain bright silver deposits from an electroplating, which is tartrate-free. Greenspan states that his baths must be tartrate-free when using the glycerol complex of antimony.
Furthermore, in U.SO Patent No. 2,777,810 (Ostrow) there is a disclosure that divalent (-2) selenium compound in the presence of antimony compounds and free cyanide gives bright deposits up to 100 AS~.
It should be further noted that when divalent or hexavalent selenium compounds are used, either by themselves or in combination with antimony, they do not give bright deposits over the wide current density range, i.e. 200 to 5000 ASF.
l7~
~ IO~
The present invention relates to a particular elec-troplating bath for producing mirror bright silver deposits.
More particularly selenium, or combinations of selenium and antimony, are added as additives. The selenium component may be any bath soluble selenium compound in which the selenium is tetravalent, i.e., has a valence of 4, and in which the anions and/or cations associated with the tetravalent selenium do not have an adverse effect on either the electroplating bath or the silver electrodeposit produced~ Generally, it is added as either selenious acid or as an alkali metal or ammo-nium selenite. Similarly, the antimony component may be any bath soluble compound or complex of antimony in which the anions and/or cations associated with the antimony do not have an adverse effect on either the electroplating bath or the silver electrodeposit produced~ Desirably, the antimony component is employed in the form o~ its complex with an alkali metal carboxylic acid salt~ With selenium or both antimony and selenium present a mirror bright silver deposit results.
The source of silver is an alkali metal or ammonium or amine silver cyanide. Other essential components are boric acid or citric acid, or the alkali metal or ammonium salts of such acids. Generally, for operations at current densi-ties above about 500 ASF., both boric and citric acids are employed: and most preferably the acids are utilized in the form of their alkali metal salts.
In general, the electroplating bath is substantially free of free cyanide. It is ~ormulated to have a pH within the range of about 7.0 to about 9.0, and it will be operated within a temperature range of about 20 to about 80C and at a high current density of up to about 5000 A~F.
7:~
The silver will be present in the bath in an amount which is at least sufficient to produce a smooth electrodeposit of silver on the substrate. The citrate and borate will be present in amounts which are at least sufficient, either alone or in combination, to effect buffering of the bath to maintain it within the desired operable pH range. The selenium or sele-nium and antimony will be present in amounts which are at least sufficient to produce a bright electrodeposit of silver~
~ NVENTION
As previously set forth, the goal of the present invention is to provide an electroplating bath, which can be operated at high speed up to 5000 ASF to produce a mirror bright silver deposit on various substrates or workpieces such as copper alloys, nickel alloys, and the like.
The source of the silver in the bath is desirably an alkali metal or ammonium silver cyanideO Although ammo-nium, potassium, sodium, and lithium silver cyanides may be employed, the most preferred feed is potassium silver cyanide.
It will be further understood that for most purposes of the present invention wherever the use of an alkali metal is pres-cribed, potassium is especially preferred unless otherwise indicated.
The amount of silver, derived from the potassium silver cyanide, generally ranges from about 20 to 120 g/l, preferably from about 30 to 100 g/l.
The citric acid or its alkali metal or ammonium salt, preferably potassium citrate, is employed in amounts generally ranginy from about 50 to 200 g/l, preferably 75 to 140 g/l.
. ~ _ s The boric acid or its alkali metal or ammonium salt, which for operations at current densities above about 500 ASF, is employed not in place of the citric acid or its alkali metal salt but rather iTl conjunction with the citric acid, is utilized in amounts generally ranginy frorn about 10 to 50 g/l, preferably 20 -to 40 g/l. Again, the preferred boric acid component is its potassium metal salt, namely po-tassium borate.
The selenium component is desirably selenious acid (H2SeC3) or an alkali metal or ammonium selenium salt wherein the valence is 4 (i.e. tetravalent) rather than divalent as prescribed in the prior art teaching described above. The selenium component is utilized in the bath in amounts generally ranging from about 2.0 to 5 g/l, and preferably about 2.5 to 5 g/l. In forming the alkali metal salt, the selenious acid is merely neutralized with an alkali metal material such as the hydroxide. Thus, for example, potassium hydroxide may be readily employed to neutralize the selenious acid. Based on selenium metal alone, the bath will generally contain 1 to 3 g/l, and preferably 1.5 to 3 g~l.
For certair~ purposes of this invention an antimony component is also employed in the bath to ensure the deposi-tion of mirror bright silver depositsO Preferably the antimony is used in the form of an alkali metal carboxilic acid complex, and most preferably as potassium antimony tartrate. Other complexes that could be employed ln the present invention include the antimony potassium glycera-te, antimony oxide dissolved in other carboxilic acids, and the like. The amount of antimony metal used in the bath will ranqe from about 0,5 to 2.5 g/l, preferably 1.0 to 1.5 g/l.
It is an important feature of the present invention that the resulting electroplating bath be substantially free of free cyanide, which is another distinction between the present invention and the known baths of the prior art. By substantially free of cyanide one means a cyanide ion content of less than ak~ut, 1.5 g/l, and preferably less than about 0.25 g/l. Furthermore, the electroplating bath is also free of nitrate ions.
A preerred bath composition according to the present invention is set forth below:
~ 9~ Concentration, q~l Silver as potassium silver cyanide 30-100 Potassium Citrate 75-140 Potassium Borate 20- 40 H2SeO3 [neutralized with KOHJ 2- 5 Antimony ras potassium antimony tartrate] 1-1.5 7~
The pH of the bath may range from about 7.0 to 9.0 preferabl~ 7.5 to 8.5, while the temperature is maintained with the range of 20 to 80C, preferably about 40 to 70C.
As described above, the current density may be relatively high, .io e. up to 5000 ASE'. Although the current density employed may be as low as 100, in order to ensure the pro-duction of mirror bright silver deposits, the densities will generally range from about 200 to 5000 ASF, i~e. about 20 to 530 A/dm ~ASD).
The invention will be more fully understood by reference to the following illustrative embodiments.
EXAMPLE I
An electrolytic bath was prepared having the following formulation:
.Silver as potassium silver cyanide - 60 g~l Potassium citrate - 100 ~/1 Boric Acid - 30 g/l Selenium as Selenious acid - 2.0 g/l This electrolyte a-t 70C deposited mirror bright plates when selectively plated at current densities between 1000 to 4000 ASF on copper alloy~ The pH of the bath was 8.
The use of the same formulation given in Example I, but operated at 50C, resulted in mirror bright deposits between 400 and 1500 ASF~
7~
EXAM~LE 3 The same formulation given in Example I, but operated at 30C, plated selectively mirror bright deposits between 200 and 400 ASF.
The procedure of Example 3 is repeated except that the potassium citrate is omitted from the bath and similar results are obtained.
The procedure of Example 3 is repeated except that the bGric acid is omitted from the bath and similar results are obtained.
An electrolytic bath was prepared having the follo-wing formulation:
Silver as potassium silver cyanide - 80 g/l Potassium citrate - 75 g/l Boric acid - 20 g/l Selenium as selenious acid -2.0 g/l Antimony as potassium antimony tartrate -1.5 g/l This electrolyte when operated at 60C selectively plated mirror bright silver deposits from 1000 to 5000 ASF.
The above data demonstrates that the electrolytic baths of the present invention give outstanding silver deposits.
By way of comparison, it was found that when the selenious acid or salt of the illustrative embodiment was substituted with a selenide (where the selenium is divalent) or selenate (where the selenium is hexavalent) the thus fo~med electro-lytes did not give mirror bright or bright silver deposits when plated selectively at a current density of over 500 ASF.
ri While certain Eeatures of the present invention have been illustrated above, it will be understood that the invention is obviously subject to variations and modiiications without departiny from the broader aspects of the invention.
Claims (13)
1. An aqueous, stable electroplating bath suitable for high speed production of mirror bright silver deposits at high current densities of up to about 5000 ASF, said aqueous bath being substantially free of free cyanide and comprising the following components:
a. an alkali metal, ammonium or amine silver cya-nide;
b. a component selected from the group consisting of citric acid, boric acid, alkali metal salts of citric or boric acid, ammonium salts of citric or boric acid, and mixtures thereof, and c. a bath soluble selenium compound in which the selenium has a valence of 4;
the silver being present in the bath in an amount which is at least sufficient to produce a smooth electrodeposit of silver, the citric and boric acids or salts thereof being pre-sent in amounts which are at least sufficient, either alone or in combination, to effect buffering of the bath to main-tain it within a predetermined pH range and the selenium being present in an amount which is at least sufficient to produce a bright electrodeposit of silver.
a. an alkali metal, ammonium or amine silver cya-nide;
b. a component selected from the group consisting of citric acid, boric acid, alkali metal salts of citric or boric acid, ammonium salts of citric or boric acid, and mixtures thereof, and c. a bath soluble selenium compound in which the selenium has a valence of 4;
the silver being present in the bath in an amount which is at least sufficient to produce a smooth electrodeposit of silver, the citric and boric acids or salts thereof being pre-sent in amounts which are at least sufficient, either alone or in combination, to effect buffering of the bath to main-tain it within a predetermined pH range and the selenium being present in an amount which is at least sufficient to produce a bright electrodeposit of silver.
2. The electroplating bath of Claim 1 wherein the selenium component is selected from the group consisting of selenious acid, and the alkali metal and ammonium salts of selenious acid.
3. The electroplating bath of Claim 1, wherein the bath also contains a bath soluble compound or complex of antimony.
4. The electroplating bath of Claim 2, wherein the bath also contains antimony in the form of an alkali metal carboxylic acid complex thereof.
5. The electroplating bath of Claim 2, wherein the bath contains potassium silver cyanide.
6. The electroplating bath of Claim 2, wherein the bath contains an alkali metal citrate and an alkali metal borate.
7. The electroplating bath of Claim 6, wherein the bath contains potassium citrate and potassium borate.
8. The electroplating bath of Claim 2, wherein the selenium component is selenious acid.
9. The electroplating bath of Claim 2, wherein the selenium component is an alkali metal selenite.
10. The electroplating bath of Claim 4, wherein the antimony is in the form of a potassium carboxylic acid salt complex.
11. The electroplating bath of Claim 10, wherein the antimony complex is potassium antimony tartrate.
12. The electroplating bath of Claim 1, having a pH of from about 7.0 to 9Ø
13. A method of electrodepositing bright silver on a substrate which comprises passing an electric current between a cathode and an anode through an electroplating bath as defined in Claims 1, 2 or 3 at a current density of from about 200 to about 5000 ASF for a period of time sufficient to deposit the desired thickness of silver.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US20580380A | 1980-11-10 | 1980-11-10 | |
| US205,803 | 1980-11-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1181715A true CA1181715A (en) | 1985-01-29 |
Family
ID=22763700
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000388152A Expired CA1181715A (en) | 1980-11-10 | 1981-10-16 | Composition and process for high speed bright silver plating |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPS57110688A (en) |
| BE (1) | BE891078A (en) |
| BR (1) | BR8107252A (en) |
| CA (1) | CA1181715A (en) |
| DE (1) | DE3143225C2 (en) |
| FR (1) | FR2493881B1 (en) |
| GB (1) | GB2086940B (en) |
| HK (1) | HK67086A (en) |
| IT (1) | IT1171647B (en) |
| NL (1) | NL8104883A (en) |
| PT (1) | PT73880B (en) |
| SE (1) | SE8106495L (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5983788A (en) * | 1982-11-04 | 1984-05-15 | Shinko Electric Ind Co Ltd | High-speed silver plating method |
| JPS61195986A (en) * | 1985-02-25 | 1986-08-30 | Nippon Engeruharudo Kk | Lusterless high-velocity silver plating liquid |
| DE4010346A1 (en) * | 1990-03-28 | 1991-10-02 | Siemens Ag | METHOD OF APPLYING SILVER GRAPHITE DISPERSION OVERLAYS |
| ITMI20052435A1 (en) * | 2005-12-21 | 2007-06-22 | F Lli Calegaro Di Luigi Di Francesco Calegaro | METHOD OF SURFACE FINISH OF THE SILVER AND ITS ALLOYS |
| WO2018181190A1 (en) * | 2017-03-31 | 2018-10-04 | メタローテクノロジーズジャパン株式会社 | Electrolytic silver plating solution |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2777810A (en) * | 1956-10-03 | 1957-01-15 | Elechem Corp | Bath for electroplating silver |
| GB1234793A (en) * | 1967-06-26 | 1971-06-09 | Tesla Np | Brightening and hardening additive for electrolytic silvering baths |
| JPS5814519B2 (en) * | 1976-08-11 | 1983-03-19 | 三菱電機株式会社 | Low cyanide high speed electrolytic silver plating solution |
| SU620515A1 (en) * | 1976-10-19 | 1978-08-25 | Всесоюзный Научно-Исследовательский Проектно-Конструкторский Институт Ювелирной Промышленности (Внииювелирпром) | Silver plating electrolyte |
| US4155817A (en) * | 1978-08-11 | 1979-05-22 | American Chemical And Refining Company, Inc. | Low free cyanide high purity silver electroplating bath and method |
-
1981
- 1981-10-16 CA CA000388152A patent/CA1181715A/en not_active Expired
- 1981-10-26 PT PT73880A patent/PT73880B/en unknown
- 1981-10-27 JP JP56171969A patent/JPS57110688A/en active Granted
- 1981-10-28 NL NL8104883A patent/NL8104883A/en not_active Application Discontinuation
- 1981-10-31 DE DE3143225A patent/DE3143225C2/en not_active Expired
- 1981-11-03 SE SE8106495A patent/SE8106495L/en not_active Application Discontinuation
- 1981-11-09 FR FR8120954A patent/FR2493881B1/en not_active Expired
- 1981-11-09 BR BR8107252A patent/BR8107252A/en not_active IP Right Cessation
- 1981-11-09 IT IT49659/81A patent/IT1171647B/en active
- 1981-11-09 GB GB8133721A patent/GB2086940B/en not_active Expired
- 1981-11-10 BE BE0/206513A patent/BE891078A/en not_active IP Right Cessation
-
1986
- 1986-09-11 HK HK670/86A patent/HK67086A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IT8149659A0 (en) | 1981-11-09 |
| JPS57110688A (en) | 1982-07-09 |
| DE3143225C2 (en) | 1983-12-29 |
| GB2086940B (en) | 1984-06-13 |
| PT73880A (en) | 1981-11-01 |
| BR8107252A (en) | 1982-07-27 |
| SE8106495L (en) | 1982-05-11 |
| DE3143225A1 (en) | 1982-06-16 |
| JPH0124230B2 (en) | 1989-05-10 |
| BE891078A (en) | 1982-05-10 |
| FR2493881A1 (en) | 1982-05-14 |
| IT1171647B (en) | 1987-06-10 |
| HK67086A (en) | 1986-09-18 |
| FR2493881B1 (en) | 1986-04-18 |
| NL8104883A (en) | 1982-06-01 |
| PT73880B (en) | 1983-01-25 |
| GB2086940A (en) | 1982-05-19 |
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