U.S. patent application number 10/274634 was filed with the patent office on 2004-04-22 for pulse reverse electrolysis of acidic copper electroplating solutions.
Invention is credited to Crary, Michael Ray, Herdman, Roderick Dennis, Long, Ernest.
Application Number | 20040074775 10/274634 |
Document ID | / |
Family ID | 32093089 |
Filed Date | 2004-04-22 |
United States Patent
Application |
20040074775 |
Kind Code |
A1 |
Herdman, Roderick Dennis ;
et al. |
April 22, 2004 |
Pulse reverse electrolysis of acidic copper electroplating
solutions
Abstract
Pulse reverse electrolysis of acid copper solutions is used for
applying copper to decorative articles, such as aluminium alloy
automotive wheels and plastic parts for automotive use. The
benefits include an improved thickness distribution of the copper
electrodeposited on the plated article, reduced metal waste,
reduced plating times and increased production capacity.
Inventors: |
Herdman, Roderick Dennis;
(Staffordshire, GB) ; Crary, Michael Ray; (San
Clemente, CA) ; Long, Ernest; (Coventry, GB) |
Correspondence
Address: |
Jennifer A. Calcagni
Carmody & Torrance LLP
P.O. Box 1110
50 Leavenworth Street
Waterbury
CT
06721-1110
US
|
Family ID: |
32093089 |
Appl. No.: |
10/274634 |
Filed: |
October 21, 2002 |
Current U.S.
Class: |
205/103 ;
205/120; 205/296 |
Current CPC
Class: |
C25D 5/611 20200801;
C25D 3/38 20130101; C25D 5/627 20200801; C25D 5/18 20130101 |
Class at
Publication: |
205/103 ;
205/120; 205/296 |
International
Class: |
C25D 005/18; C25D
003/38 |
Claims
What is claimed is:
1. A method of plating decorative articles in an acidic copper
electroplating bath comprising the steps of: (a) suspending said
decorative article in an plating bath comprising copper ions,
counter ions, and chloride ions; and (b) plating said decorative
article for a period of time with pulse-reverse current to produce
a desired thickness of copper on at least one surface of said
decorative article.
2. The method according to claim 1, wherein the counter ion is
sulfate.
3. The method according to claim 1, wherein the electroplating bath
contains copper ions at a concentration of about 10-50 g/l.
4. The method according to claim 1, wherein the electroplating bath
comprises sulphuric acid at a concentration of about 50-250
ml/l.
5. The method according to claim 4, wherein the electroplating bath
comprises sulphuric acid at a concentration of about 100-150
ml/l.
6. The method according to claim 1, wherein the electroplating bath
comprises chloride ions at a concentration of about 10-500
mg/l.
7. The method according to claim 6, wherein the electroplating bath
comprises chloride ions at a concentration of about 50-150
mg/l.
8. The method according to claim 1, wherein the plating bath
further comprises a polyether and a divalent sulphur compound.
9. The method according to claim 8, wherein the polyether is
present at a concentration of about 50-5000 mg/l.
10. The method according to claim 9, wherein the polyether is
present at a concentration of about 300 mg/l.
11. The method according to claim 8, wherein the polyether has a
molecular weight between 500 and 100,000.
12. The method according to claim 11, wherein the polyether is
polyethyleneglycol.
13. The method according to claim 11, wherein the polyether is an
ethylene oxide/propylene oxide co-polymer.
14. The method according to claim 8, wherein the divalent sulphur
compound is present in the plating bath at a concentration of about
1-150 mg/l.
15. The method according to claim 14, wherein the divalent sulphur
compound is present in the plating bath at a concentration of about
30-50 mg/l.
16. The method according to claim 8, wherein the divalent sulphur
compound is mercaptopropanesulphonic acid or an alkali metal salt
thereof.
17. The method according to claim 8, wherein the divalent sulphur
compound is bis-(propane-3-sulphonic acid)disulphide or an alkali
metal salt thereof.
18. The method according to claim 8, wherein the divalent sulphur
compound is bis-(ethane-2-sulphuric acid)disulphide or an alkali
metal salt thereof.
19. The method according to claim 1, wherein the plating bath
further comprises an element selected from the group consisting of
brighteners and levellers.
20. The method according to claim 8, wherein the plating bath
further comprises an element selected from the group consisting of
brighteners and levellers.
21. The method according to claim 1, wherein the pulse plating
regime consists of alternating cathodic and anodic pulses.
22. The method according to claim 21, wherein the cathodic pulse
time is 5-100 ms.
23. The method according to claim 21 wherein the anodic pulse time
is 0.1-10 ms.
24. The method according to claim 21, wherein the pulse plating
regime further comprises a final cathodic period of extended
time.
25. The method according to claim 24, wherein the final cathodic
pulse is up to 1 hour.
26. The method according to claim 1, wherein the average applied
current density is 0.5-5.0 A/dm.sup.2.
27. The method according to claim 26, wherein the current density
during the anodic pulse is between 1 and 5 times the current
density during the cathodic pulse.
28. The method according to claim 1, wherein the thickness ratio of
the copper deposited is less than 2.5:1.
29. A decorative substrate produced in accordance with the process
of claim 1.
30. The decorative substrate of claim 29, wherein a subsequent
coating is applied over the copper layer.
31 An aluminium alloy wheel produced in accordance with the process
of claim 1.
32. The aluminium alloy wheel of claim 31, wherein a subsequent
coating is applied over the copper layer.
33. A plastic substrate produced in accordance with the process of
claim 1.
34. The plastic substrate of claim 33, wherein a subsequent coating
is applied over the copper layer.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the use of pulse reverse plating
to deposit copper from acid solutions onto decorative substrates,
to produce a more even distribution of the copper deposit.
BACKGROUND OF THE INVENTION
[0002] The plating of copper from acid solutions is well known,
with numerous industrial applications. In most applications the
articles to be plated are suspended in the electrolyte, a technique
hereafter called rack plating.
[0003] One of these applications is plating aluminium alloy
automobile wheels, whereby the aluminium alloy surface is cleaned
and degreased prior to immersion in a zincate solution, which
leaves a thin zinc coating on the alloy surface. Because of the
acidic nature of the copper plating solution, the zincate film
would be destroyed upon immersion. To avoid destruction of the
zincate film, a thin nickel coating is normally electrodeposited
from a mildly acidic bath onto the zincate film, and then copper is
subsequently deposited onto the nickel by electroplating from the
highly acidic copper solution. The zincate/nickel treatment
facilitates the plating of the copper onto aluminium alloy
substrates, which cannot be electroplated directly. In the specific
example of aluminium alloy automobile wheels, it is common practice
to deposit a relatively thick copper film, which is usually
subjected to a polishing operation prior to electrodeposition of
the final nickel and chromium finish.
[0004] The deposition of copper serves two purposes: (1) it can
have levelling properties and thus can be used to hide blemishes in
the cast aluminium wheel, and (2) it is soft and easily polished.
Polishing of the copper surface leaves a smooth finish that looks
attractive when the final finish is applied. In addition, polishing
the surface spreads the soft copper and effectively seals any pores
in the copper deposit, thus improving the corrosion resistance of
the deposit.
[0005] One of the drawbacks of the current technique is that a
minimum thickness of copper must be deposited onto the aluminium
base to ensure that no areas of the copper deposit are removed
completely during the polishing operation, and to provide adequate
protection of the aluminium during subsequent processing stages.
However, due to the nature of the electrolyte and additives used in
the acidic copper plating stage, the distribution of the copper
plate is generally uneven. To achieve the required minimum
thickness in recesses, excess copper is plated onto the more
exposed areas of the wheel, which is very wasteful and costly for
the plater.
[0006] Another application for copper deposition is electroplating
onto plastic substrates, which is very common in the automotive
industry. Generally in these applications, the plastic substrate is
pre-treated to allow it to accept a thin nickel deposit that is
deposited by electroless means. Once the thin layer of nickel
renders the plastic component electrically conductive, a
substantial layer of copper is applied before the final finish of
nickel and chromium is applied. A minimum copper thickness is
normally specified by the end-user of the plated part, for example
the automotive manufacturer. Due to the poor distribution of copper
metal deposited from conventional decorative electrolytes,
achieving this minimum copper thickness in the recesses of
complex-shaped parts results in excessive amounts of copper
deposited on the exposed areas. Again, this results in wasted
copper for the plater and can also result in other problems such as
treeing or burning of the deposit, or rejects due to failure on
dimensional tolerances. Treeing and burning are familiar terms well
known to those skilled in the electroplating art and describe
faults in the plated deposit that can occur on exposed areas of an
electroplated article.
[0007] Therefore it would be advantageous for a process to provide
for a greatly improved distribution of the copper deposit over the
surface of the plated articles. This can increase production
capacity by reducing the processing time required to achieve the
minimum thickness of copper. In addition, it can reduce the amount
of copper wasted, and also reduce the possibility of rejects
because of dimensional tolerance, burning or treeing of the copper
deposit.
[0008] Other applications where a more even distribution of a
copper deposit is advantageous are also contemplated by the present
invention.
[0009] The use of pulse reverse plating techniques to deposit
copper from acidic solutions is well-known within the electronics
industry, for plating copper from acidic solutions onto printed
circuit boards and other substrates. U.S. Pat. No. 6,319,384, to
Taylor et al., the subject matter of which is herein incorporated
by reference in its entirety, discloses a method for the
electrodeposition of copper onto a semiconductor substrate, wherein
the acidic copper plating bath is substantially devoid of
brighteners and and/or levellers.
[0010] The basic chemistry of the additives used for electronics
applications, and their performance under pulse reverse current
plating conditions as compared to direct current conditions is
explained by T. Pearson, "Effect of Pulsed Current On The
Electrodeposition of Chromium and Copper", PhD thesis, Aston
University, United Kingdom, 1989, the subject matter of which is
herein incorporated by reference in it is entirety. The additives
are broadly similar to those used in general rack plating
applications, and broadly comprise a sulphopropyl sulphide and a
polyalkylene glycol that operate in conjunction with chloride ion.
The use of pulse reverse current with these additives results in an
electrochemical effect that causes an improved metal distribution.
It is this effect that is utilised to plate copper into the holes
on circuit boards. These holes are typically 0.5 mm diameter and
2-3 mm deep. The effective current density in these holes is
extremely low and outside of the normal range expected in a general
rack plating applications such as plating of alloy wheels.
[0011] Unfortunately, this distribution effect can be destroyed by
other additives. For this reason, plating bath compositions
formulated for printed circuit board applications are generally
very simple and do not provide a fully bright and levelled copper
deposit. Conversely, in general rack plating applications, it is
the appearance of the copper deposit that is of prime importance.
Because pulse plating is not used, the effect of further levellers
and brightening agents on this distribution effect is
inconsequential.
[0012] The base composition of the electrolyte used for electronics
applications is also different from that used in a typical rack
plating application. Typically, a plating bath used for
electronic/circuit board applications will contain 75 g/l of copper
sulphate pentahydrate, 115 ml/l of concentrated sulphuric acid, 40
mg/l of chloride ion, and proprietary additives (a "low-metal/high
acid bath"). In contrast, a bath used for general-purpose rack
plating typically contains 220 g/l of copper sulphate pentahydrate,
35 ml/l of concentrated sulphuric acid, 80 mg/l of chloride ion and
proprietary additives (a "high-metal/low acid" bath).
[0013] The inventors have surprisingly found that the pulse reverse
current plating techniques used for printed circuit boards can
translate very well to the application of plating copper in general
rack plating applications including the aforementioned aluminium
alloy automobile wheels and plastic substrates. This is surprising
in that the current density range is very different from that
applied to printed circuit boards. The inventors have found that
the use of pulse reverse current plating in general rack plating
applications causes less waste of copper as compared to
conventional baths in various applications where articles are
plated to a minimum thickness.
[0014] When plating alloy wheels the use of pulse reverse plating
in conjunction with an electronic-type electrolyte formulation, and
an additive system optimised for pulse reverse electrolysis,
results in a much improved distribution of copper deposit on the
wheel. This has two distinct advantages to the plater: (1) there is
less excess copper deposited on the exposed areas of the wheel, and
(2) the recessed areas of the wheel can be plated to the minimum
thickness in less time than in previous applications, thereby
increasing production capacity.
[0015] To the best of the inventors' knowledge this technique has
not previously been suggested or applied for use in conventional
rack plating plants, possibly because the use of pulse reverse
current causes the deposit to become dull in high current density
regions on the plated article. However, in the case of alloy
automobile wheels, it is usual for the copper deposit to be
polished and this negative effect is no longer a factor.
Alternatively, the copper plating stage may consist of a period of
pulse reverse electrolysis followed by a period of direct current
electrolysis to leave the final deposit brighter than if pulse
reverse electrolysis only had been applied.
[0016] Additionally, the low current density regions of an article
plated with pulse reverse electrolysis retain a bright appearance
when suitable proprietary additives are used, thus leaving a bright
appearance across the whole item.
[0017] Therefore as demonstrated by the examples below, the use of
the pulse reverse current technique is ideally suited to
applications where a more even distribution of the copper deposit
is desirable, for example when plating to a minimum thickness
specification, such as for alloy wheels or when plating plastic
parts for automotive use.
SUMMARY OF THE INVENTION
[0018] The use of pulse reverse plating to deposit copper can be
used for a method of plating decorative articles in an acidic
copper electroplating bath comprising the steps of:
[0019] (a) suspending the decorative article in an plating bath
comprising copper ions, counter ions, and chloride ions; and
[0020] (b) plating the decorative article for a period of time with
pulse-reverse current to produce a desired thickness of copper on
at least one surface of said decorative article.
[0021] In a preferred embodiment, the acid copper-plating bath
further comprises a polyether and a divalent sulphur compound.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The present invention utilizes pulse-reverse current for
plating decorative articles with copper in an acidic copper plating
bath to produce a desired thickness of copper on the surfaces of
the decorative articles. The present invention is particularly
useful for plating a more uniform thickness of copper onto
aluminium alloy wheels and plastic parts for automotive use.
[0023] The acidic copper plating bath of the invention generally
comprises copper ions, a source of counter ions, and chloride ions.
Other additives may also be added to the bath to improve the copper
deposit.
[0024] Copper ions are present in the plating bath at a
concentration of about 10 to 50 g/l. Copper sulphate pentahydrate
is an example of a copper compound that is useful in the baths of
the present invention, although other copper compounds would also
be known to one skilled in the art. The plating bath generally
comprises copper sulphate pentahydrate at a concentration of about
50 to 100 g/l, preferably about 75 g/l.
[0025] The source of counter ions in the plating bath is generally
sulphate ions or methanesulphonate/methanesulphonic acid. A
preferred source of sulphate ions is sulphuric acid. The counter
ion is present in the plating bath at a concentration of about
50-250 ml/l, preferably about 100-150 ml/l, and most preferably
about 115 ml/l.
[0026] Chloride ions are present in the plating bath at a
concentration of about 10-500 mg/l, preferably about 50-150
mg/l.
[0027] In a preferred embodiment, the plating bath of the present
invention further comprises a polyether and a divalent sulphur
compound.
[0028] The polyether is generally present in the plating bath at a
concentration of about 50-5,000 mg/l, preferably about 300 mg/l.
The polyether generally has a molecular weight of between 500 and
100,000. Preferred polyethers include polyethylene glycol and an
ethylene oxide/propylene oxide co-polymer.
[0029] The divalent sulphur compound is generally present in the
plating bath at a concentration of about 1-150 mg/l, preferably
about 30-50 mg/l. Preferred divalent sulphur compounds include
mercatopropanesulponic acid or an alkali metal salt thereof,
bis-(propane-3-sulphonic acid)disulphide or an alkali metal salt
thereof, and bis-(ethane-2-sulphuric acid)disulphide or an alkali
metal salt thereof.
[0030] Commercially available levelling compounds and brighteners
may also be added to the plating bath compositions of the instant
invention. The brighteners and levellers are added to enhance the
visual performance of the deposit produced from the plating
bath.
[0031] The pulse plating regime of the plating bath consists of
alternating cathodic and anodic pulses. The cathodic pulse time is
generally between 5 and 100 ms, and the anodic pulse time is
generally between 0.1 and 10 ms. Optionally, the plating regime may
comprise a final cathodic period of extended time, up to about 1
hour.
[0032] The average applied current density is generally between
0.5-5.0 A/dm.sup.2. The current density during the anodic pulse is
typically between 1 and 5 times the current density during the
cathodic pulse.
EXAMPLES
[0033] The following non-limiting examples demonstrate various
attributes of the instant invention. In the examples, the Hull cell
tests were done with a steel panel in order for the copper deposit
thickness to be measured by X-ray fluorescence (XRF) technique. To
avoid immersion copper deposition on the steel panel, the panels
were first plated with a minimal thickness of copper (approximately
0.1-0.2 .mu.m) from a cyanide copper solution before being
transferred to the Hull cell. All Hull cell tests were carried out
at 25.degree. C. using a "sulfast" copper anode.
[0034] The pulse current regime was 10 ms cathodic, 0.5 ms anodic,
which is a normal pulse regime for printed circuit board
applications.
[0035] Examples 1-5 are illustrative of the prior art and represent
the current technology for general acid copper plating. The
compositions and plating conditions used in these examples are set
forth below in Table 1.
1TABLE 1 Prior art acid copper plating conditions Example 1 Example
2 Example 3 Example 4 Example 5 Copper sulphate 210 g/l 210 g/l 75
g/l 75 g/l 75 g/l pentahydrate Sulfuric acid 32 ml/l 32 ml/l 115
ml/l 115 ml/l 115 ml/l Chloride ion 85 mg/l 85 mg/l 85 mg/l 85 mg/l
75 mg/l Additive Cumac Cumac Cumac Cumac 300 mg/l 8000SL 8000SL
8000SL 8000SL PAG.sup.1 Additive 30 mg/l disodium salt.sup.2 Type
of plating Direct current Pulse reverse Direct current Pulse
reverse Direct current Current 1 amp 1 amp 1 amp 1 amp 1 amp
Plating time 15 minutes 15 minutes 15 minutes 15 minutes 15 minutes
Thickness ratio 6.07:1 6.8:1 4.0:1 3.0:1 4.0:1 .sup.1PAG =
Polyalkylene Glycol .sup.2disodium salt =
bis-(ethane-2-sulphate)disulphide disodium salt
Example 1
[0036] A solution was prepared containing 210 .mu.l copper sulphate
pentahydrate, 32 ml/l sulphuric acid and 85 mg/l of chloride ion.
Proprietary additives (Cumac 8000SL, a MacDermid process for
general rack acid copper plating) were added. A Hull cell panel was
plated at 1 amp for 15 minutes with direct current. The thickness
was measured at points on the panel corresponding to primary
current densities of 2.0 A/dm.sup.2 and 0.1 A/dm.sup.2. The
thickness at 2.0 A/dm.sup.2 was divided by the thickness at 0.1
A/dm.sup.2 to give a thickness ratio 6.07:1. The panel appearance
was bright across the whole range.
Example 2
[0037] A solution was prepared as in example 1 and a Hull cell
panel was plated for 15 minutes using a pulse reverse current
regime with an average current of 1 amp and an anodic:cathodic
current density of approximately 3:1. The thickness ratio was
calculated as before and was 6.8:1. The panel appearance was smooth
matte in high current density areas and bright in low current
density areas.
Example 3
[0038] A solution was prepared containing 75 g/l of copper sulphate
pentahydrate, 115 ml/l of sulphuric acid, 85 mg/l of chloride ion
and Cumac 8000SL additives. A Hull cell panel was plated at 1 amp
for 15 minutes using direct current and the thickness ratio was
calculated as 4.0:1. The deposit was fully bright across the whole
panel.
Example 4
[0039] A solution was prepared as in example 3 and a Hull cell
panel was plated for 15 minutes using a pulse reverse current
regime with an average current of 1 amp and an anodic:cathodic
current density of approximately 2:1. The thickness ratio was
calculated as before and was 3.0:1. The deposit was smooth matte in
high current density areas and bright in low current density
areas.
Example 5
[0040] A solution was prepared containing 75 g/l of copper sulphate
pentahydrate, 115 ml/l of sulphuric acid and 75 mg/l of chloride
ion. 300 mg/l of a polyalkyleneglycol and 30 mg/l of
bis-(ethane-2-sulphate)disulp- hide disodium salt was added. A Hull
cell panel was plated at 1 amp for 15 minutes using direct current
and the thickness ratio was calculated as 4.0:1. The deposit was
semi-bright across the whole range.
[0041] Examples 6-12 illustrate non-limiting plating baths of the
instant invention. The compositions and plating conditions used in
these examples are set forth below in Tables 2-3.
2TABLE 2 Various copper plating baths of the instant invention
Example 6 Example 7 Example 8 Example 9 Copper sulphate 75 g/l 75
g/l 75 g/l 75 g/l pentahydrate Sulfuric acid 115 ml/l 115 ml/l 115
ml/l 115 ml/l Chloride ion 75 mg/l 75 mg/l 150 mg/l 150 mg/l
Additive 300 mg/l PAG.sup.1 MacuSpec PPR 300 mg/l PAG 300 mg/l PAG
Additive 30 mg/l disodium salt.sup.2 30 mg/l disodium salt.sup.3 50
mg/l disodium salt.sup.3 Type of plating Pulse reverse Pulse
reverse Pulse reverse Pulse reverse Current 1 amp 1 amp 1 amp 1 amp
Plating time 15 minutes 15 minutes 15 minutes 15 minutes Thickness
ratio 2.20:1 1.9:1 2.20:1 2.15:1 .sup.1PAG = Polyalkylene Glycol
.sup.2disodium salt = bis-(ethane-2-sulphate)disulphide disodium
salt .sup.3disodium salt = bis-(3-sulphopropyl)disulphid- e
disodium salt
[0042]
3TABLE 3 Various copper plating baths of the instant invention
Example 10 Example 11 Example 12 Copper sulphate 75 g/l 75 g/l 75
g/l pentahydrate Sulfuric acid 115 ml/l 115 ml/l 115 ml/l Chloride
ion 75 mg/l 75 mg/l 75 mg/l Additive 300 mg/l PAG.sup.1 300 mg/l
PAG 300 mg/l PAG Additive 30 mg/l disodium salt.sup.2 30 mg/l
disodium salt.sup.3 30 mg/l disodium salt.sup.3 Additive 40 mg/l
levelling compound A 50 mg/l levelling compound B 40 mg/l levelling
compound A Type of plating Pulse reverse Pulse reverse Pulse
reverse Current 1 amp 1 amp 1 amp Plating time 15 minutes 15
minutes 15 minutes Thickness ratio 1.70:1 2.20:1 2.15:1 .sup.1PAG =
Polyalkylene Glycol .sup.2disodium salt =
bis-(ethane-2-sulphate)disulphide disodium salt .sup.3disodium salt
= bis-(3-sulphopropyl)disulphide disodium salt
Example 6
[0043] A solution was prepared containing 75 g/l of copper sulphate
pentahydrate, 115 ml/l of sulphuric acid and 75 mg/l of chloride
ion. 300 mg/l of a polyalkyleneglycol and 30 mg/l of
bis-(ethane-2-sulphate)disulp- hide disodium salt was added. A Hull
cell panel was plated for 15 minutes using a pulse reverse current
regime with an average current of 1 amp and an anodic:cathodic
current density of approximately 2:1. The thickness ratio was
calculated as 2.20:1. The panel was smooth matte in high current
density areas and semi-bright in low current density areas.
Example 7
[0044] A solution was prepared containing 75 g/l copper sulphate
pentahydrate, 115 ml/l sulphuric acid and 75 mg/l of chloride ion.
Proprietary additives (MacuSpec PPR, a MacDermid process for
plating of printed circuit boards) were added and a Hull cell panel
was plated for 15 minutes using a pulse reverse current regime with
an average current of 1 amp and an anodic:cathodic current density
of approximately 2:1. The thickness ratio was calculated as 1.9:1.
The deposit was smooth matte in high current density areas and
semi-bright in low current density areas.
Example 8
[0045] A solution was prepared containing 75 g/l copper sulphate
pentahydrate, 115 ml/l sulphuric acid and 150 mg/l of chloride ion.
300 mg/l of polyalkyleneglycol and 30 mg/l of
bis-(3-sulphopropyl)disulphide disodium salt were added. A Hull
cell panel was plated for 15 minutes using a pulse reverse current
regime with an average current of 1 amp and an anodic:cathodic
current density of approximately 2:1. The thickness ratio was
calculated as 2.20:1. The deposit was smooth matte in high current
density areas and semi-bright in low current density areas.
Example 9
[0046] A solution was prepared containing 75 g/l copper sulphate
pentahydrate, 115 ml/l sulphuric acid and 150 mg/l of chloride ion.
300 mg/l of polyalkyleneglycol and 50 mg/l of
bis-(3-sulphopropyl)disulphide disodium salt were added. A Hull
cell panel was plated for 15 minutes using a pulse reverse current
regime with an average current of 1 amp and an anodic:cathodic
current density of approximately 2:1. The thickness ratio was
calculated as 2.15:1. The deposit was smooth matte in high current
density areas and semi-bright in low current density areas.
Example 10
[0047] A solution was prepared containing 75 g/l copper sulphate
pentahydrate, 115 ml/l sulphuric acid and 75 mg/l of chloride ion.
300 mg/l of polyalkyleneglycol, 30 mg/l of
bis-(ethane-2-sulphate)disulphide disodium salt and 40 mg/l of
commercially available levelling compound A were added. A Hull cell
panel was plated for 15 minutes using a pulse reverse current
regime with an average current of 1 amp and an anodic:cathodic
current density of approximately 2:1. The thickness ratio was
calculated as 1.70:1. The deposit was smooth matte in high current
density areas and fully bright in low current density areas.
Example 11
[0048] A solution was prepared containing 75 g/l copper sulphate
pentahydrate, 115 ml/l sulphuric acid and 75 mg/l of chloride ion.
300 mg/l of polyalkyleneglycol, 30 mg/l of
bis-(3-sulphopropyl)disulphide disodium salt and 50 mg/l of
commercially available levelling compound B were added. A Hull cell
panel was plated for 15 minutes using a pulse reverse current
regime with an average current of 1 amp and an anodic:cathodic
current density of approximately 2:1. The thickness ratio was
calculated as 2.20:1. The deposit was smooth matte in high current
density areas and fully bright in low current density areas.
Example 12
[0049] A solution was prepared containing 75 g/l copper sulphate
pentahydrate, 115 ml/l sulphuric acid and 75 mg/l of chloride ion.
300 mg/l of polyalkyleneglycol, 30 mg/l of
bis-(3-sulphopropyl)disulphide disodium salt and 40 mg/l of
commercially available levelling compound A were added. A Hull cell
panel was plated for 15 minutes using a pulse reverse current
regime with an average current of 1 amp and an anodic:cathodic
current density of approximately 2:1, followed by 1 amp for 5
minutes of direct current. The thickness ratio was calculated as
2.15:1. The deposit was bright across the entire panel.
* * * * *