CA1036534A - Method and composition for producing bright palladium electrodepositions - Google Patents
Method and composition for producing bright palladium electrodepositionsInfo
- Publication number
- CA1036534A CA1036534A CA217,526A CA217526A CA1036534A CA 1036534 A CA1036534 A CA 1036534A CA 217526 A CA217526 A CA 217526A CA 1036534 A CA1036534 A CA 1036534A
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- Canada
- Prior art keywords
- per liter
- bath
- palladium
- mole per
- gram mole
- Prior art date
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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
- C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
Abstract
ABSTRACT
A composition for producing adherent deposits of palladium from cya-nide-free bath uses small amounts of cobalt or nickel or the combination there-of as the brightener. The bath employs as an electrolyte alkali metal and ammoni-um sulfates, sulfamates, phosphates, nitrates, nitrites and mixtures thereof.
Preferably, the brightener concentration is 0.004-0.02 gram mole per liter nickel or 0.002-0.04 gram mole per liter cobalt, or the combination thereof.
Cetyltrimethylammonium bromide is an optional component for the bath which is maintained at a pH of 7.5-11.0 and at a temperature of 28°-80° Centigrade.
For barrel plating, the current density is 0.05-0.5 amperes per square decimeterand for rack plating the current density is 0.2-2.0 amperes per square decimeter.
A composition for producing adherent deposits of palladium from cya-nide-free bath uses small amounts of cobalt or nickel or the combination there-of as the brightener. The bath employs as an electrolyte alkali metal and ammoni-um sulfates, sulfamates, phosphates, nitrates, nitrites and mixtures thereof.
Preferably, the brightener concentration is 0.004-0.02 gram mole per liter nickel or 0.002-0.04 gram mole per liter cobalt, or the combination thereof.
Cetyltrimethylammonium bromide is an optional component for the bath which is maintained at a pH of 7.5-11.0 and at a temperature of 28°-80° Centigrade.
For barrel plating, the current density is 0.05-0.5 amperes per square decimeterand for rack plating the current density is 0.2-2.0 amperes per square decimeter.
Description
~Q;~65:~4 The' present invention~relates to compositions for the' electrodeposi~ - .
tion of palladium for a cyanide-free'bath-and to methods of electroplating palladium ' ,- .
using such baths'. .:~
' Various compositions have.been proposed for the' deposition of . . ~ .
palladium and various electrolytes' have been utilize'd to provide sufficient conduc~
tivity in such compositions. As is true with many of the noble metals, cyanide ' ;~;
electrolytes have enjoyed' considerable commercial application, and it is the ; .' desire to control pollution problerns which have created' an increasing trend toward the' substitution of other electrolytes'. . .
` ! ' , .
10 . As is true with many of the' noble metals, small amounts of brighten- '. ' ers are highly de~irable to effect optimum specWar brightness in the electrodepo- ::
sit.: .~lthough some brighteners will produce specular brightness j the:re is ~ome-times a ten'dency for the' brightener'itself to reduce' the' ductilit~r of the' deposit o:r to reduce the adhesion to the substrate.
It is an object of the' present invention to provide a novel 'composition ..
for the' electrodeposition of palladium in bright, highly adherent coatings upon . various types'.of conductive substrates.
It is also an obje¢t to provide such' composition which' is operable over ;
a wide range of :current density and at ambient to low elevated temperatures . ' .
20: Another object is to provide a method'for'the electroplating of palla- .
.... .
dium which: is relatively trouble-free and relatively insensitive to minor variations ~' .
in operating conditions and which'.will produce bright, highly adherent electro-deposits of palladium. ' It has now been found that the' orégoing and related objec-ts may he ' ., obtained in an aqueous bath .for the' electroplating of palladium which consists essentially of 0 . 02-0 . 25' gram mole per liter' oE palladium ion; 0 . 9-3 . 6 'gram moles' .
per'liter of a soluble electrolyte :selectéd' from the' group consisting of alkali metàl and ammonium sulfates', sulfamates, phosphates, nitrates', nitrites and mixtures' . ''.
--2-- . : .
, .
~365~4 thereof; and a soluble metallic brightener selected from the group consist-ing of 0. 002. -0. 04 gram mole per liter of cobalt ion, 0. 004-0. 02 gram mole per liter of nickel ion and mixtures thereof providing 0. 003-0. 068 gram mole per liter of the metal ions combined. The weight ratio of pal-ladium to cobalt, when cobalt is present, should be within the range of 10-50 and preferably 10-33. The weight ratio of palladium to nickel when nickel is present should be within the range 7. 6-19. 2 and preferably 7. 5-12. 8. The bath :may contain up to 6xlO gram mole per liter of cetyltri-methylammonium bromide, and the p~I thereof is adjusted to be within the range o:E 7. 5-11. 0.
The preferred soluble electrolyte is a ~ulfate saltl and potassium sulate has becn ~ownd hlghly advantageous. Th~ pr~e:rred compos:lt:lon~
employ cetyltrimethylammonium bromide in an amount of at least 3x10-5 gram mole per liter. The palladium ion is desirably present in the amount of 0. 05-0.1 gram mole per liter; the ammonium hydroxide is preferably present in an amount of 1. 4-2.1 gram moles per liter; and the electrolyte is desirably present in an amount of 0. 2-0. 4 gram mole per liter; this pre-ferred bath composition is desirably utilized at a pH of 8. 5-9. 5. `
In the method of electroplating, a workpiece having a conductive .;
surface is immersed in the aqueous bath described hereinbe:Eore while the temperature is maintained at 2680 Centigrade. A potential is applied -;
across the workpiece and anode inert to the bath so as to provide a current density oE 0. 05-2, 0 amperes per square decimeter, and the anode to cath-ode surface ratio is maintained at about 1. 0-5. 0:1. 0. A;Eter application of :
the potential Ior a period of time st~ficient to develop the desired thickness of palladium depo~it, the workpiece is removed :Erom the bath, In barrel plating, the current density is maintained at about 0. 05-0. 5 amperes per s~are decimeter and in rack plating the current density is maintained at ,~( -3-~a :
3653~ ~
about 0. 2-2. 0 amperes per square decimeter. The preferred baths are -operated at a temperature of 46-52 Centigrade under conditions of vigorous agitation. . .
As has been indicated hereinbe~ore, the compositions OI the present invention essentially comprise an aqueous solution of palladium ion, an . . `
electro-~ ~ .
3a ~(~36S3~
lyte, a brightener selected' from the group consisting of cobalt ion, nickel ion or the combination thereof, and 'ammonium hydroxide sufficient to provide a pH of about 7 . 5-11. 0 . A desirable optional additive is cetyltrimethylammonium bro-mide .
Turning first in detail to the' palladium ion, it may be' introduced' as any soluble compound having a non-interering anion. Thus, the' palladium may be introduced as palladiùm sulfate, palladium chloride, palladiùm nitrate, or as a palladium complex such as di`aminepalladium hydroxide, ' dichlorodiaminepalladi- ;
um or tetraminepalladium chloride.' The'`amount of palladium in the bath may :
broadly range from 0.02' 0.25:gram mole per'liter'and is preferably within the' range oE 0 . 05-0 .10 gram mole per liter'.
As indicated` hereinbefore, the electrolyte may 'be' providecl `by any one or mixture o alkali metal: and ammonium suleates, sulfamates, phosp'hate~', ;;
nitrates'and nitrites'. Of the various electrolytes, the' alkali metal and ammonium ~' sulfates have proven to bé' most advantageously employed'; postassium sulfate is preferred`. The` concentration of the' electrolyte salt may vary from as little as O .1 'gram mole per:liter:to as much' as O . 7 'grani mole per liter'. Preferably, the`
concentration of the` electrolyte salt is within the' range of 0 . 2-0. '4 gram mole per liter .
20' Ammorlium hydroxide is advantageously used' to re~gulate the' pH of the'bath and is present in an amount of 0.9-3.6 gr'am moles per`liter'calculated' ~
as ammonium hydroxide exclusive of water'. For the` preferred compositions, ; ';
the''ammonium hydroxide is present in an 'amount o-f 1.'4-2.1 gram mole per'liter. `
Dllost desirably, the``ammonium hydroxide i`s added' as a high'ly concentrated '' aqueous solution 129%' by weight) in order to minimize' dilution, although less concentrated compositions may also be' `èmployed` if the` water introduced the:rèby is entered' into the' calculations as to concentration of the` remaining ions .
In the` event that it is desired` to adjust the' pH downwardly (i.e ., ''`, ''`
~36~4 to make it more acid), an acid having non-interfering anion should be' employed~ ~ -Most conveniently, thiS is :sulfuric acid, although nitric acid, hydrochloric acid ~ ~ ' and sulfamic acid may be' employed'.
As has been:indicated heretofore, the brightener'is a metal ion se-lected' from the group consisting of' cobalt, nickel 'and the' combination thereof .
As such, the metal ions may be' introduced in the' form of any soluble compound . .' which' will not introduce an interfering anion. For the preferred' sulfate baths, ';
these metal ions are introduced' as sulfate salts . However', they' may also be' in-troduced as chloride or nitrate salts and as complexes.such: as di'aminecobalt ' 10' chloride, hex'aminecobalt chloride,:hex'aminecobalt nitrate, aquapentaminecobalt chloride,'diaquatetraminenickel'nitrate, he'x'aminenickel'nitrate and hexaminenic-kel 'chloride . ' ' .
When' co'balt is u~ed alone as t'he''brightener', it i~ prosent in an amount of 0 . 002' 0, 04'. gram mole per liter and preferably 0 . 003-0 . 02 gram mole '.
per'liter . When' nickel is used' alone as the' brightener, it is present in an amount .;
~;~ , o . ~ol/ . o~
F~ ( of o . 00'40 . 0~ \gram mole per' liter' and preferably 0 . 010-0 . 015 gram mole per :
liter'. When' bhe' two metal ions are .used' in combination with .each' other, the' ' total 'amount thereof should provide about 0 . 5-4 . 0 'grams per' liter of metàl ion or -' ~.-.. ..
about 0 . '003 '0 . 068 gram mole per:liter' of lons c'ombined . Preferably ~ the' metal : . -. . .
ions combined:equal 0.8-2.~'grams per'liter or'about 0.005 0.03'4'gram molè per . .
liter', . .
The' ratio of palladium ion'to :cobalt or nickel ion must be' fairly closely controlled' in order'to obtain stress-free' deposits . The' weight'ratio of :
palladium to cobalt should adjusted' to .within the' range of 10-50 and preferably 10=33 . The' palladlum to nickel 'metal: welght 'ratio. sho'uld be'. adjusted to within the' range 7, 5-19'. 2 and preferably 7 . 5-12 . 8 .
Cetylbrimethylammonium bromide is an optional but desirable additive to e:Efectively eliminate gas pitting in .the' palladium deposit . The 'amount of " ':
this additive should be' closely controlled' since' excessive 'amounts will produce ;
--5-- ~ . :
1~3~
excessive foaming and interfere with the plating operation, As a result, the' maximum amount which~ should be' employed' is abo'ut 6x10~4 gram mole per' liter or 0 . 2 gram per liter. Preferably, the maximum concentration is less than 0 . 06 -'' gram per liter. An amount of as little as 2.7x10-5 gram mole per liter and :;
preferably 8x10~5 gram mole per'liter (0 . Ol' and 0 . '03 gram per liter' respectively) .;
will produce highly advantageous results.
The'pH of the'bath is maintained'within the range of 7.5-ll.0 and preferably within the' range of 8.5-9.5. As indicated hereinbefore, the' pH may be adjusted' by the addition of 'ammonium hydroxide or by the' use o~ a suitable ':':
acid providing a non-interfering anion such' as sulfuric acid.
The' temperature of the' bath .should be' within the' range o.E 26-60 Centigrade, and pre:eera'bly 46-52 Cent:igrade.' Although the'bnt:ti may be ' utilize'd without agitation, it is de~irable to employ agitation and vigorous agita- .
tion ha's been Iound extremely beneficial. Filtration i9 highly desirable if pore-free'.adherent deposits. are t'o be' obtained' because the' presence'of any :
solid contaminants will have a profound effect upon'the' quality of the deposit.
Standard filter cartridges:of polypropylene or other'filter media may clesirably ; .
be:employed'for continuous filtration'of the'bath.' '~
The' anode to cathode :surface:area ratio sho'uld be within the' range 20' . of 1.0-5.0:1.0 and preferably 2.0:1Ø'~ For rack'plating, the' current density .
sho'uld be within the' range of 0.. 2-2 . 0 amperes'per' square decimeter and pref~
erably abo'ut 0.5-l.0'amperes per'square decimeter'. For barrel plating, the cur- .' rent density should be' within the' range of 0 . 05-0 . 5 'ampere9 per ~quare decimeter and preferably about 0 . 'l-0 . 3 'amperes: per' square decimeter .
It has been' ound that the' palladium deposits produced b~ the' present .
invention:are relatively stress-free'and can be''employed without further treatment :
for :the' great bulk of 1ntended applications . In some instances:, where the work- "
piece is to be' subjected' to severe mechanical defo~rmation or to heavy wearing ' .
~Q~65;~
and abrasion, it is desirable to heat treat the' workpieces at a temperature of:about 30'0-450. Centigrade for '1/2 to :3 hours in order'to relieve all residual ' internal stresses. The heat treatment may be' conducted' either under vacuùm .
or in an inert gas atmosphere.' ' ;`
Various anodes' which: are inert to the plating bath may be employed' and generally such' anode6' will have: a :surface ' of noble metal, although carbon anodes do have limited' utility . The' preferred' anodes' are platinum-clad tantalum ' `''' although gold-clad tantalum, platinum and palladium electrodes'have all been' em-ployed' effectively. ' 10' Exemplary of the'present invention'are the'following specific examples: .
' 'Example' One ' ~ ' ' A bath is prepared by adding to deionized'water'pallaflium ~ul:t`ate su.E- .
ficient to provide 5 . O gr'ams per liter ' as pallaclium metal, 80 c . c . per ' liter ' of ammanium hydroxide (29~6' by weight 'NEI3) ., 1. 05'. grams per liter:co'balt sul:Eate, : .
50 ~rams per'liter'potassium sulfate and 0.04' grams per'liter'cetylbrimethylammo-nium br'om'ide . ' The' resulting bath has a pH of 8 . 5 'and is introduced' into a plating cell where .the' temperature is maintained' at 44 . 5. Centigrade. ' ' . A potential: of 1. 7 'volts is applied' across a platinum surfaced anode and a Hull.cell panel '3 centimeters by 5 centimeters in dimension, the' anode ' .' 20' to cathode surface:area'ratio being 3;1.' The:current density is determined `~
to be' 0 . '5 "amperes'per s(luare decimeter' and the' current is continued for 20' minutes ~during which' there .is fast agitation of the' plating bath .' The' panel is then: r'emoved' and the' palladium deposit thus formed' is found to have a thickness of 2 . 5 microns and to be' specular bright.: :E;lexing of the' panel 'repeatedly indieates'that the' deposit is highly :adherent . .
' Ex'ample` Two To deionize'd'water:are added'the'various componçnts in 'amounts sufficient to provide 9. 0 grams per'liter'of palladium determined' as the metal, ~7~
~.Q36534 : i lOO.c.c. per liter'of ammonium hydroxide ~29%'by weight'NH3)., 2.63 grams per :':
liter'nickel sulfate, lO'0' grams per'liter potassium sulfate and 0..03' gram per liter cetyltrimethylammonium bromide . ' The' pE of the formulation 'is 7 . 9 and the' temperature is maintained' at 37'. 8 Centigrade . ' ....
A Hull celI panel is used' as the' cathode and a platinum-surfaced ` ' anode is employed'. A potential of 2 .'2 volts is applied' thereacross during fast agitation of the' solution'in the' cell . The' anode to cathode surface' area :ratio is . ; ;' 3:'1 andthe'current density.is 0.5'amperes'per'square decimeter'. ' ,' After plating for 20' minutes, the panel 'is removed' and is found to ., '.
10 . have a specular bright 'palladium deposit of 1. 0 microns thickn'e5s . Ei'lexing the' panel indicates' the' deposit to he' highly :adherent i .
' Ex'am'ple' Thr'ee ,:
To evaluate the' effe,ct of other'e'lectrolyte~, a mixed electrolyte is prepared'using 25'grams per'liter:potassium sulfate,'? grams per'liter'ammo~
nium nitrate and 1 gr'am per:liter ammonium chloride.' The'bath contains palla~
dlum sulfate :suffi,cient to provide 5 grams per'liter:of palladium as metal and ,' '"' 60 c . c . .per' liter: ammonium hydroxide (29% by weight NH3), and 0 . 06~ gram per ~'' liter:cetyltrimethyl'ammonium bromide .:: 'Used as the' brightener is 0 . 46 gram per' - ~ ' liter:cobalt :sulfate .: The pH of this fo'r,mulation 'is 9 . 9 'and the bath is introduced '-. -20. ' into a test barrel plating installation wherein it is maintained' at 49' Centigrade.' The' workpieces:to be plated' are nickel pins about one centimeter in . ~
len'gth :and about 0:. 5 'millimeters in dïameter'. . The' anode to cathode surface area ' ~ ' ratio i~ calculated' at 1: '1 and a potential, of 5, volts is applied' to provide a cu'rrent .: ;" . ',' . density of 0,.2 amperes:per square decimeter'. The'plating operation is continued ; .
for :a period'of 9.0' minutes'.after which: ~he' parts are remoued' and found to have a ': ' specular bright'.depo~it o:E 2.'5 microns thickness. The' deposit is highly adherent , , ' as evidenced by the' lack: of exfoliation'aEter'ben'ding of the' pins through 90' . ::'.. ', . .
Thus it can be seen: from' the foregoing detailed specification and ex- '` ,' ' ''`': . .
-8~ .,, . :,.
~.~3~;53~
amples that the baths of the present invention :provide bright, highly adherent electrodeposits on various types of conductive substrates. They are operable -`.
over a wide range of current density :and at ambient to low elevated temperatures, The plating operation is relatively trouble-free and relatively insensitive to minor variations in operating conditions and will yield deposits which are sub- .
~tantially ~ree from internal stresses. ~ .
'~ '. ' ~ ,..
''~'~'' "
tion of palladium for a cyanide-free'bath-and to methods of electroplating palladium ' ,- .
using such baths'. .:~
' Various compositions have.been proposed for the' deposition of . . ~ .
palladium and various electrolytes' have been utilize'd to provide sufficient conduc~
tivity in such compositions. As is true with many of the noble metals, cyanide ' ;~;
electrolytes have enjoyed' considerable commercial application, and it is the ; .' desire to control pollution problerns which have created' an increasing trend toward the' substitution of other electrolytes'. . .
` ! ' , .
10 . As is true with many of the' noble metals, small amounts of brighten- '. ' ers are highly de~irable to effect optimum specWar brightness in the electrodepo- ::
sit.: .~lthough some brighteners will produce specular brightness j the:re is ~ome-times a ten'dency for the' brightener'itself to reduce' the' ductilit~r of the' deposit o:r to reduce the adhesion to the substrate.
It is an object of the' present invention to provide a novel 'composition ..
for the' electrodeposition of palladium in bright, highly adherent coatings upon . various types'.of conductive substrates.
It is also an obje¢t to provide such' composition which' is operable over ;
a wide range of :current density and at ambient to low elevated temperatures . ' .
20: Another object is to provide a method'for'the electroplating of palla- .
.... .
dium which: is relatively trouble-free and relatively insensitive to minor variations ~' .
in operating conditions and which'.will produce bright, highly adherent electro-deposits of palladium. ' It has now been found that the' orégoing and related objec-ts may he ' ., obtained in an aqueous bath .for the' electroplating of palladium which consists essentially of 0 . 02-0 . 25' gram mole per liter' oE palladium ion; 0 . 9-3 . 6 'gram moles' .
per'liter of a soluble electrolyte :selectéd' from the' group consisting of alkali metàl and ammonium sulfates', sulfamates, phosphates, nitrates', nitrites and mixtures' . ''.
--2-- . : .
, .
~365~4 thereof; and a soluble metallic brightener selected from the group consist-ing of 0. 002. -0. 04 gram mole per liter of cobalt ion, 0. 004-0. 02 gram mole per liter of nickel ion and mixtures thereof providing 0. 003-0. 068 gram mole per liter of the metal ions combined. The weight ratio of pal-ladium to cobalt, when cobalt is present, should be within the range of 10-50 and preferably 10-33. The weight ratio of palladium to nickel when nickel is present should be within the range 7. 6-19. 2 and preferably 7. 5-12. 8. The bath :may contain up to 6xlO gram mole per liter of cetyltri-methylammonium bromide, and the p~I thereof is adjusted to be within the range o:E 7. 5-11. 0.
The preferred soluble electrolyte is a ~ulfate saltl and potassium sulate has becn ~ownd hlghly advantageous. Th~ pr~e:rred compos:lt:lon~
employ cetyltrimethylammonium bromide in an amount of at least 3x10-5 gram mole per liter. The palladium ion is desirably present in the amount of 0. 05-0.1 gram mole per liter; the ammonium hydroxide is preferably present in an amount of 1. 4-2.1 gram moles per liter; and the electrolyte is desirably present in an amount of 0. 2-0. 4 gram mole per liter; this pre-ferred bath composition is desirably utilized at a pH of 8. 5-9. 5. `
In the method of electroplating, a workpiece having a conductive .;
surface is immersed in the aqueous bath described hereinbe:Eore while the temperature is maintained at 2680 Centigrade. A potential is applied -;
across the workpiece and anode inert to the bath so as to provide a current density oE 0. 05-2, 0 amperes per square decimeter, and the anode to cath-ode surface ratio is maintained at about 1. 0-5. 0:1. 0. A;Eter application of :
the potential Ior a period of time st~ficient to develop the desired thickness of palladium depo~it, the workpiece is removed :Erom the bath, In barrel plating, the current density is maintained at about 0. 05-0. 5 amperes per s~are decimeter and in rack plating the current density is maintained at ,~( -3-~a :
3653~ ~
about 0. 2-2. 0 amperes per square decimeter. The preferred baths are -operated at a temperature of 46-52 Centigrade under conditions of vigorous agitation. . .
As has been indicated hereinbe~ore, the compositions OI the present invention essentially comprise an aqueous solution of palladium ion, an . . `
electro-~ ~ .
3a ~(~36S3~
lyte, a brightener selected' from the group consisting of cobalt ion, nickel ion or the combination thereof, and 'ammonium hydroxide sufficient to provide a pH of about 7 . 5-11. 0 . A desirable optional additive is cetyltrimethylammonium bro-mide .
Turning first in detail to the' palladium ion, it may be' introduced' as any soluble compound having a non-interering anion. Thus, the' palladium may be introduced as palladiùm sulfate, palladium chloride, palladiùm nitrate, or as a palladium complex such as di`aminepalladium hydroxide, ' dichlorodiaminepalladi- ;
um or tetraminepalladium chloride.' The'`amount of palladium in the bath may :
broadly range from 0.02' 0.25:gram mole per'liter'and is preferably within the' range oE 0 . 05-0 .10 gram mole per liter'.
As indicated` hereinbefore, the electrolyte may 'be' providecl `by any one or mixture o alkali metal: and ammonium suleates, sulfamates, phosp'hate~', ;;
nitrates'and nitrites'. Of the various electrolytes, the' alkali metal and ammonium ~' sulfates have proven to bé' most advantageously employed'; postassium sulfate is preferred`. The` concentration of the' electrolyte salt may vary from as little as O .1 'gram mole per:liter:to as much' as O . 7 'grani mole per liter'. Preferably, the`
concentration of the` electrolyte salt is within the' range of 0 . 2-0. '4 gram mole per liter .
20' Ammorlium hydroxide is advantageously used' to re~gulate the' pH of the'bath and is present in an amount of 0.9-3.6 gr'am moles per`liter'calculated' ~
as ammonium hydroxide exclusive of water'. For the` preferred compositions, ; ';
the''ammonium hydroxide is present in an 'amount o-f 1.'4-2.1 gram mole per'liter. `
Dllost desirably, the``ammonium hydroxide i`s added' as a high'ly concentrated '' aqueous solution 129%' by weight) in order to minimize' dilution, although less concentrated compositions may also be' `èmployed` if the` water introduced the:rèby is entered' into the' calculations as to concentration of the` remaining ions .
In the` event that it is desired` to adjust the' pH downwardly (i.e ., ''`, ''`
~36~4 to make it more acid), an acid having non-interfering anion should be' employed~ ~ -Most conveniently, thiS is :sulfuric acid, although nitric acid, hydrochloric acid ~ ~ ' and sulfamic acid may be' employed'.
As has been:indicated heretofore, the brightener'is a metal ion se-lected' from the group consisting of' cobalt, nickel 'and the' combination thereof .
As such, the metal ions may be' introduced in the' form of any soluble compound . .' which' will not introduce an interfering anion. For the preferred' sulfate baths, ';
these metal ions are introduced' as sulfate salts . However', they' may also be' in-troduced as chloride or nitrate salts and as complexes.such: as di'aminecobalt ' 10' chloride, hex'aminecobalt chloride,:hex'aminecobalt nitrate, aquapentaminecobalt chloride,'diaquatetraminenickel'nitrate, he'x'aminenickel'nitrate and hexaminenic-kel 'chloride . ' ' .
When' co'balt is u~ed alone as t'he''brightener', it i~ prosent in an amount of 0 . 002' 0, 04'. gram mole per liter and preferably 0 . 003-0 . 02 gram mole '.
per'liter . When' nickel is used' alone as the' brightener, it is present in an amount .;
~;~ , o . ~ol/ . o~
F~ ( of o . 00'40 . 0~ \gram mole per' liter' and preferably 0 . 010-0 . 015 gram mole per :
liter'. When' bhe' two metal ions are .used' in combination with .each' other, the' ' total 'amount thereof should provide about 0 . 5-4 . 0 'grams per' liter of metàl ion or -' ~.-.. ..
about 0 . '003 '0 . 068 gram mole per:liter' of lons c'ombined . Preferably ~ the' metal : . -. . .
ions combined:equal 0.8-2.~'grams per'liter or'about 0.005 0.03'4'gram molè per . .
liter', . .
The' ratio of palladium ion'to :cobalt or nickel ion must be' fairly closely controlled' in order'to obtain stress-free' deposits . The' weight'ratio of :
palladium to cobalt should adjusted' to .within the' range of 10-50 and preferably 10=33 . The' palladlum to nickel 'metal: welght 'ratio. sho'uld be'. adjusted to within the' range 7, 5-19'. 2 and preferably 7 . 5-12 . 8 .
Cetylbrimethylammonium bromide is an optional but desirable additive to e:Efectively eliminate gas pitting in .the' palladium deposit . The 'amount of " ':
this additive should be' closely controlled' since' excessive 'amounts will produce ;
--5-- ~ . :
1~3~
excessive foaming and interfere with the plating operation, As a result, the' maximum amount which~ should be' employed' is abo'ut 6x10~4 gram mole per' liter or 0 . 2 gram per liter. Preferably, the maximum concentration is less than 0 . 06 -'' gram per liter. An amount of as little as 2.7x10-5 gram mole per liter and :;
preferably 8x10~5 gram mole per'liter (0 . Ol' and 0 . '03 gram per liter' respectively) .;
will produce highly advantageous results.
The'pH of the'bath is maintained'within the range of 7.5-ll.0 and preferably within the' range of 8.5-9.5. As indicated hereinbefore, the' pH may be adjusted' by the addition of 'ammonium hydroxide or by the' use o~ a suitable ':':
acid providing a non-interfering anion such' as sulfuric acid.
The' temperature of the' bath .should be' within the' range o.E 26-60 Centigrade, and pre:eera'bly 46-52 Cent:igrade.' Although the'bnt:ti may be ' utilize'd without agitation, it is de~irable to employ agitation and vigorous agita- .
tion ha's been Iound extremely beneficial. Filtration i9 highly desirable if pore-free'.adherent deposits. are t'o be' obtained' because the' presence'of any :
solid contaminants will have a profound effect upon'the' quality of the deposit.
Standard filter cartridges:of polypropylene or other'filter media may clesirably ; .
be:employed'for continuous filtration'of the'bath.' '~
The' anode to cathode :surface:area ratio sho'uld be within the' range 20' . of 1.0-5.0:1.0 and preferably 2.0:1Ø'~ For rack'plating, the' current density .
sho'uld be within the' range of 0.. 2-2 . 0 amperes'per' square decimeter and pref~
erably abo'ut 0.5-l.0'amperes per'square decimeter'. For barrel plating, the cur- .' rent density should be' within the' range of 0 . 05-0 . 5 'ampere9 per ~quare decimeter and preferably about 0 . 'l-0 . 3 'amperes: per' square decimeter .
It has been' ound that the' palladium deposits produced b~ the' present .
invention:are relatively stress-free'and can be''employed without further treatment :
for :the' great bulk of 1ntended applications . In some instances:, where the work- "
piece is to be' subjected' to severe mechanical defo~rmation or to heavy wearing ' .
~Q~65;~
and abrasion, it is desirable to heat treat the' workpieces at a temperature of:about 30'0-450. Centigrade for '1/2 to :3 hours in order'to relieve all residual ' internal stresses. The heat treatment may be' conducted' either under vacuùm .
or in an inert gas atmosphere.' ' ;`
Various anodes' which: are inert to the plating bath may be employed' and generally such' anode6' will have: a :surface ' of noble metal, although carbon anodes do have limited' utility . The' preferred' anodes' are platinum-clad tantalum ' `''' although gold-clad tantalum, platinum and palladium electrodes'have all been' em-ployed' effectively. ' 10' Exemplary of the'present invention'are the'following specific examples: .
' 'Example' One ' ~ ' ' A bath is prepared by adding to deionized'water'pallaflium ~ul:t`ate su.E- .
ficient to provide 5 . O gr'ams per liter ' as pallaclium metal, 80 c . c . per ' liter ' of ammanium hydroxide (29~6' by weight 'NEI3) ., 1. 05'. grams per liter:co'balt sul:Eate, : .
50 ~rams per'liter'potassium sulfate and 0.04' grams per'liter'cetylbrimethylammo-nium br'om'ide . ' The' resulting bath has a pH of 8 . 5 'and is introduced' into a plating cell where .the' temperature is maintained' at 44 . 5. Centigrade. ' ' . A potential: of 1. 7 'volts is applied' across a platinum surfaced anode and a Hull.cell panel '3 centimeters by 5 centimeters in dimension, the' anode ' .' 20' to cathode surface:area'ratio being 3;1.' The:current density is determined `~
to be' 0 . '5 "amperes'per s(luare decimeter' and the' current is continued for 20' minutes ~during which' there .is fast agitation of the' plating bath .' The' panel is then: r'emoved' and the' palladium deposit thus formed' is found to have a thickness of 2 . 5 microns and to be' specular bright.: :E;lexing of the' panel 'repeatedly indieates'that the' deposit is highly :adherent . .
' Ex'ample` Two To deionize'd'water:are added'the'various componçnts in 'amounts sufficient to provide 9. 0 grams per'liter'of palladium determined' as the metal, ~7~
~.Q36534 : i lOO.c.c. per liter'of ammonium hydroxide ~29%'by weight'NH3)., 2.63 grams per :':
liter'nickel sulfate, lO'0' grams per'liter potassium sulfate and 0..03' gram per liter cetyltrimethylammonium bromide . ' The' pE of the formulation 'is 7 . 9 and the' temperature is maintained' at 37'. 8 Centigrade . ' ....
A Hull celI panel is used' as the' cathode and a platinum-surfaced ` ' anode is employed'. A potential of 2 .'2 volts is applied' thereacross during fast agitation of the' solution'in the' cell . The' anode to cathode surface' area :ratio is . ; ;' 3:'1 andthe'current density.is 0.5'amperes'per'square decimeter'. ' ,' After plating for 20' minutes, the panel 'is removed' and is found to ., '.
10 . have a specular bright 'palladium deposit of 1. 0 microns thickn'e5s . Ei'lexing the' panel indicates' the' deposit to he' highly :adherent i .
' Ex'am'ple' Thr'ee ,:
To evaluate the' effe,ct of other'e'lectrolyte~, a mixed electrolyte is prepared'using 25'grams per'liter:potassium sulfate,'? grams per'liter'ammo~
nium nitrate and 1 gr'am per:liter ammonium chloride.' The'bath contains palla~
dlum sulfate :suffi,cient to provide 5 grams per'liter:of palladium as metal and ,' '"' 60 c . c . .per' liter: ammonium hydroxide (29% by weight NH3), and 0 . 06~ gram per ~'' liter:cetyltrimethyl'ammonium bromide .:: 'Used as the' brightener is 0 . 46 gram per' - ~ ' liter:cobalt :sulfate .: The pH of this fo'r,mulation 'is 9 . 9 'and the bath is introduced '-. -20. ' into a test barrel plating installation wherein it is maintained' at 49' Centigrade.' The' workpieces:to be plated' are nickel pins about one centimeter in . ~
len'gth :and about 0:. 5 'millimeters in dïameter'. . The' anode to cathode surface area ' ~ ' ratio i~ calculated' at 1: '1 and a potential, of 5, volts is applied' to provide a cu'rrent .: ;" . ',' . density of 0,.2 amperes:per square decimeter'. The'plating operation is continued ; .
for :a period'of 9.0' minutes'.after which: ~he' parts are remoued' and found to have a ': ' specular bright'.depo~it o:E 2.'5 microns thickness. The' deposit is highly adherent , , ' as evidenced by the' lack: of exfoliation'aEter'ben'ding of the' pins through 90' . ::'.. ', . .
Thus it can be seen: from' the foregoing detailed specification and ex- '` ,' ' ''`': . .
-8~ .,, . :,.
~.~3~;53~
amples that the baths of the present invention :provide bright, highly adherent electrodeposits on various types of conductive substrates. They are operable -`.
over a wide range of current density :and at ambient to low elevated temperatures, The plating operation is relatively trouble-free and relatively insensitive to minor variations in operating conditions and will yield deposits which are sub- .
~tantially ~ree from internal stresses. ~ .
'~ '. ' ~ ,..
''~'~'' "
Claims (16)
1. In an aqueous bath for the electroplating of palladium, the combination consisting essentially of:
A. 0.02-0.25 gram mole per liter of palladium ion;
B. 0.9-3.6 gram moles per liter of ammonium hydroxide;
C. 0.1-0.7 gram mole per liter of a soluble electrolyte selected from the group consisting of alkali metal and ammonium sulfates, sulfamates, phosphates, nitrates, nitrites and mixtures thereof;
D. a soluble metallic brightener selected from the group consist-ing of 0.002-0.04 gram mole per liter of cobalt ion, 0.004-0.02 gram mole per liter of nickel ion and mixtures thereof providing 0.007-0.068 gram mole per liter of metal ions, the weight ratio of palladium to cobalt when cobalt is present being within the range of 10-50 and the weight ratio of palladium to nickel when nickel is present being within the range of 7.5-19.2; and E. up to 6x10-4 gram mole per liter of cetyltrimethylammonium bromide;
said bath having a pH of 7.5-11Ø
A. 0.02-0.25 gram mole per liter of palladium ion;
B. 0.9-3.6 gram moles per liter of ammonium hydroxide;
C. 0.1-0.7 gram mole per liter of a soluble electrolyte selected from the group consisting of alkali metal and ammonium sulfates, sulfamates, phosphates, nitrates, nitrites and mixtures thereof;
D. a soluble metallic brightener selected from the group consist-ing of 0.002-0.04 gram mole per liter of cobalt ion, 0.004-0.02 gram mole per liter of nickel ion and mixtures thereof providing 0.007-0.068 gram mole per liter of metal ions, the weight ratio of palladium to cobalt when cobalt is present being within the range of 10-50 and the weight ratio of palladium to nickel when nickel is present being within the range of 7.5-19.2; and E. up to 6x10-4 gram mole per liter of cetyltrimethylammonium bromide;
said bath having a pH of 7.5-11Ø
2. The bath in accordance with Claim 1 wherein said soluble electrolyte is a sulfate salt.
3. The bath in accordance with Claim 2 wherein said soluble salt is potassium sulfate.
4. The bath in accordance with Claim 1 wherein said cetyltri-methylammonium bromide is present in an amount of at least 3x10-5 gram mole per liter.
5. The bath in accordance with Claim 1 wherein said soluble metalic brightener is a mixture of nickel and cobalt ions.
6. The bath in accordance with Claim 1 wherein said palladium ion is present in an amount of 0.05-0.1 gram mole per liter, said am-monium hydroxide is present in an amount of 1.4-2.1 gram moles per liter, said electrolyte is present in an amount of 0.2-0.4 gram mole per liter, and wherein said bath has a pH of 8.5-9.5.
7. The bath in accordance with Claim 6 wherein said electrolyte is a sulfate salt and wherein said cetyltrimethylammonium bromide is present in an amount of at least 3x10-5 gram per liter.
8. In the method of electroplating palladium deposits upon a work-piece, the steps comprising:
A. immersing a workpiece having a conductive surface in an aqueous bath consisting essentially of:
1. 0.02-0.25 gram mole per liter of palladium ion;
2Ø9-3.6 gram moles per liter of ammonium hydroxide;
3. 0.1-0.7 gram mole per liter of a soluble electrolyte se-lected from the group consisting of alkali metal and ammo-nium sulfates, sulfamates, phosphates, nitrates, nitrites and mixtures thereof;
4. a soluble metalic brightener selected from the group con-sisting of 0.002-0.04 gram mole per liter of cobalt ion, 0.004-0.02 gram mole per liter of nickel ion and mixtures thereof providing 0.003-0.068 gram mole per liter of metal ions, the weight ratio of palladium to cobalt when cobalt is present being within the range 10-50 and the weight ratio of palladium to nickel when nickel is present being within the range of 7.5-19.2; and 5. up to 6x10-4 gram mole per liter of cetyltrimethylammo-nium bromide;
said bath having a pH of 7.5-11.0;
B. maintaining the temperature of said bath at 26°-60° Centigrade;
C. applying a potential across said workpiece and an anode inert to said bath, said potential providing a current density of 0.05-2.0 amperes per square decimeter and the anode to cathode surface ratio being 1.0-5.0:1.0; and D. removing said workpiece from said bath upon deposition of the desired thickness of palladium upon the surface thereof.
A. immersing a workpiece having a conductive surface in an aqueous bath consisting essentially of:
1. 0.02-0.25 gram mole per liter of palladium ion;
2Ø9-3.6 gram moles per liter of ammonium hydroxide;
3. 0.1-0.7 gram mole per liter of a soluble electrolyte se-lected from the group consisting of alkali metal and ammo-nium sulfates, sulfamates, phosphates, nitrates, nitrites and mixtures thereof;
4. a soluble metalic brightener selected from the group con-sisting of 0.002-0.04 gram mole per liter of cobalt ion, 0.004-0.02 gram mole per liter of nickel ion and mixtures thereof providing 0.003-0.068 gram mole per liter of metal ions, the weight ratio of palladium to cobalt when cobalt is present being within the range 10-50 and the weight ratio of palladium to nickel when nickel is present being within the range of 7.5-19.2; and 5. up to 6x10-4 gram mole per liter of cetyltrimethylammo-nium bromide;
said bath having a pH of 7.5-11.0;
B. maintaining the temperature of said bath at 26°-60° Centigrade;
C. applying a potential across said workpiece and an anode inert to said bath, said potential providing a current density of 0.05-2.0 amperes per square decimeter and the anode to cathode surface ratio being 1.0-5.0:1.0; and D. removing said workpiece from said bath upon deposition of the desired thickness of palladium upon the surface thereof.
9. The method in accordance with Claim 8 wherein said solution, workpiece and anodes are placed in contact within a barrel plating installa-tion and wherein the current density is maintained at about 0.05-0.5 amperes per square decimeter.
10. The method in accordance with Claim 8 wherein said solution, a workpiece and anodes are placed in contact within a rack plating installa-tion and wherein the current density is maintained at about 0.2-2.0 amperes per square decimeter.
11. The method in accordance with Claim 8 wherein the tempera-ture of the bath is maintained at 46°-52° Centigrade and wherein vigorous agitation is employed.
12. The method in accordance with Claim 8 wherein the surface of said anode is a noble metal.
13. The method in accordance with Claim 8 wherein said soluble electrolyte is potassium sulfate.
14. The method in accordance with Claim 8 wherein said palladium ion is present in an amount of 0.05-0.1 gram mole per liter, said ammonium hydroxide is present in an amount 1.4-2.1 gram moles per liter, said electrolyte is present in an amount of 0.2-0.4; gram mole per liter, and wherein said bath has a pH of 8.5-9.5.
15. The method in accordance with Claim 14 wherein said electro-lyte is a sulfate salt and wherein said cetyltrimethylammonium bromide is present in an amount of at least 3x10-5 gram mole per liter.
16. The bath in accordance with Claim 1 wherein the weight ratio of palladium to cobalt when cobalt is present is within the range of 10-33 and the weight ratio of palladium to nickel when nickel is present is within the range of 7.5-12.8.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US435844A US3925170A (en) | 1974-01-23 | 1974-01-23 | Method and composition for producing bright palladium electrodepositions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1036534A true CA1036534A (en) | 1978-08-15 |
Family
ID=23730043
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA217,526A Expired CA1036534A (en) | 1974-01-23 | 1975-01-07 | Method and composition for producing bright palladium electrodepositions |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US3925170A (en) |
| JP (1) | JPS548537B2 (en) |
| CA (1) | CA1036534A (en) |
Families Citing this family (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1495910A (en) * | 1975-10-30 | 1977-12-21 | Ibm | Method and bath for electroplating palladium on an articl |
| US4028064A (en) * | 1976-02-17 | 1977-06-07 | Texas Instruments Incorporated | Beryllium copper plating process |
| US4066517A (en) * | 1976-03-11 | 1978-01-03 | Oxy Metal Industries Corporation | Electrodeposition of palladium |
| US4100039A (en) * | 1976-11-11 | 1978-07-11 | International Business Machines Corporation | Method for plating palladium-nickel alloy |
| US4401527A (en) * | 1979-08-20 | 1983-08-30 | Occidental Chemical Corporation | Process for the electrodeposition of palladium |
| CH649581A5 (en) * | 1979-08-20 | 1985-05-31 | Oxy Metal Industries Corp | AGENT FOR THE ELECTROLYTIC DEPOSITION OF METALLIC PALLADIUM ON A SUBSTRATE. |
| US4297179A (en) * | 1980-09-02 | 1981-10-27 | American Chemical & Refining Company Incorporated | Palladium electroplating bath and process |
| US4297177A (en) * | 1980-09-19 | 1981-10-27 | American Chemical & Refining Company Incorporated | Method and composition for electrodepositing palladium/nickel alloys |
| US4487665A (en) * | 1980-12-17 | 1984-12-11 | Omi International Corporation | Electroplating bath and process for white palladium |
| US4392921A (en) * | 1980-12-17 | 1983-07-12 | Occidental Chemical Corporation | Composition and process for electroplating white palladium |
| US4545868A (en) * | 1981-10-06 | 1985-10-08 | Learonal, Inc. | Palladium plating |
| US4622110A (en) * | 1981-10-06 | 1986-11-11 | Learonal, Inc. | Palladium plating |
| DE3148788C2 (en) * | 1981-12-09 | 1986-08-21 | Siemens AG, 1000 Berlin und 8000 München | Aqueous bath and process for the galvanic deposition of shiny and crack-free palladium layers and process for the production of the bath |
| JPS5967388A (en) * | 1982-09-09 | 1984-04-17 | エンゲルハ−ド・コ−ポレ−シヨン | Palladium plating bath |
| US4468296A (en) * | 1982-12-10 | 1984-08-28 | At&T Bell Laboratories | Process for electroplating palladium |
| US4478692A (en) * | 1982-12-22 | 1984-10-23 | Learonal, Inc. | Electrodeposition of palladium-silver alloys |
| US4778574A (en) * | 1987-09-14 | 1988-10-18 | American Chemical & Refining Company, Inc. | Amine-containing bath for electroplating palladium |
| US5180482A (en) * | 1991-07-22 | 1993-01-19 | At&T Bell Laboratories | Thermal annealing of palladium alloys |
| US5415685A (en) * | 1993-08-16 | 1995-05-16 | Enthone-Omi Inc. | Electroplating bath and process for white palladium |
| FR2807450B1 (en) * | 2000-04-06 | 2002-07-05 | Engelhard Clal Sas | ELECTROLYTIC BATH FOR ELECTROCHEMICAL DEPOSITION OF PALLADIUM OR ITS ALLOYS |
| TWI354716B (en) * | 2007-04-13 | 2011-12-21 | Green Hydrotec Inc | Palladium-containing plating solution and its uses |
| CN101348928B (en) * | 2007-07-20 | 2012-07-04 | 罗门哈斯电子材料有限公司 | High speed method for plating palladium and palladium alloys |
| US20110147225A1 (en) * | 2007-07-20 | 2011-06-23 | Rohm And Haas Electronic Materials Llc | High speed method for plating palladium and palladium alloys |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4733176B1 (en) * | 1967-01-11 | 1972-08-23 |
-
1974
- 1974-01-23 US US435844A patent/US3925170A/en not_active Expired - Lifetime
-
1975
- 1975-01-07 CA CA217,526A patent/CA1036534A/en not_active Expired
- 1975-01-22 JP JP966175A patent/JPS548537B2/ja not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US3925170A (en) | 1975-12-09 |
| USB435844I5 (en) | 1975-01-28 |
| JPS50123532A (en) | 1975-09-29 |
| JPS548537B2 (en) | 1979-04-17 |
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