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Patent 1036534 Summary

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(12) Patent: (11) CA 1036534
(21) Application Number: 217526
(54) English Title: METHOD AND COMPOSITION FOR PRODUCING BRIGHT PALLADIUM ELECTRODEPOSITIONS
(54) French Title: METHODE ET COMPOSE POUR L'OBTENTION D'ELECTRODEPOSITIONS BRILLANTES AU PALLADIUM
Status: Expired
Bibliographic Data
(52) Canadian Patent Classification (CPC):
  • 204/29.5
(51) International Patent Classification (IPC):
  • C25D 3/50 (2006.01)
(72) Inventors :
  • ZOBBI, ROBERT G. (Not Available)
  • SKOMOROSKI, ROBERT M. (Not Available)
(73) Owners :
  • AMERICAN CHEMICAL AND REFINING COMPANY (Not Available)
(71) Applicants :
(74) Agent:
(74) Associate agent:
(45) Issued: 1978-08-15
(22) Filed Date:
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data: None

Abstracts

English 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.


Claims

Note: Claims are shown in the official language in which they were submitted.



The embodiment of the invention in which an exclusive property or
privilege is claimed are defined as follows:
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

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

11

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.

12


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.

13

Description

Note: Descriptions are shown in the official language in which they were submitted.


~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 ' .


--6--

~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. ~ .

'~ '. '
~ ,..




''~'~'' "

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Administrative Status

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Administrative Status

Title Date
Forecasted Issue Date 1978-08-15
(45) Issued 1978-08-15
Expired 1995-08-15

Abandonment History

There is no abandonment history.

Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
AMERICAN CHEMICAL AND REFINING COMPANY
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Drawings 1994-05-16 1 12
Claims 1994-05-16 4 163
Abstract 1994-05-16 1 36
Cover Page 1994-05-16 1 23
Description 1994-05-16 9 444