U.S. patent application number 09/971300 was filed with the patent office on 2003-04-10 for plating bath and method for depositing a metal layer on a substrate.
This patent application is currently assigned to Shipley Company, L.L.C.. Invention is credited to Barstad, Leon R., Buckley, Thomas, Cobley, Andrew J., Gabe, David R., Kapeckas, Mark J., Reddington, Erik, Sonnenberg, Wade.
Application Number | 20030066756 09/971300 |
Document ID | / |
Family ID | 30445132 |
Filed Date | 2003-04-10 |
United States Patent
Application |
20030066756 |
Kind Code |
A1 |
Gabe, David R. ; et
al. |
April 10, 2003 |
Plating bath and method for depositing a metal layer on a
substrate
Abstract
A metal plating bath and method for plating a metal on a
substrate. The metal plating bath contains hydroxylamines that
inhibit the consumption of additive bath components to improve the
efficiency of metal plating processes. The additive bath components
are added to metal plating baths to improve brightness of plated
metal as well as the micro-throwing and macro-throwing power of the
bath. In addition to brighteners, the additive bath components may
include levelers, suppressors, hardeners, and the like. The
hydroxylamines that inhibit additive consumption may be employed in
metal plating baths for plating copper, gold, silver, platinum,
palladium, cobalt, cadmium, nickel, bismuth, indium, tin, rhodium,
iridium, ruthenium and alloys thereof.
Inventors: |
Gabe, David R.;
(Loughborough, GB) ; Cobley, Andrew J.; (Coventry,
GB) ; Barstad, Leon R.; (Raynham, MA) ;
Kapeckas, Mark J.; (Marlborough, MA) ; Reddington,
Erik; (Ashland, MA) ; Sonnenberg, Wade;
(Edgartown, MA) ; Buckley, Thomas; (Dedham,
MA) |
Correspondence
Address: |
EDWARDS & ANGELL, LLP
Dike, Bronstein, Robert, Cushman, IP Group
P.O. Box 9169
Boston
MA
02209
US
|
Assignee: |
Shipley Company, L.L.C.
Marlborough
MA
|
Family ID: |
30445132 |
Appl. No.: |
09/971300 |
Filed: |
October 4, 2001 |
Current U.S.
Class: |
205/296 ;
205/238; 205/241; 205/242; 205/243; 205/247; 205/253; 205/255;
205/257; 205/261; 205/263; 205/264; 205/265; 205/267; 205/269;
205/271; 205/281; 205/290; 205/299; 205/302; 205/311 |
Current CPC
Class: |
C25D 3/38 20130101; C25D
3/02 20130101; H05K 3/242 20130101 |
Class at
Publication: |
205/296 ;
205/238; 205/241; 205/242; 205/243; 205/247; 205/253; 205/255;
205/257; 205/263; 205/264; 205/265; 205/267; 205/269; 205/271;
205/281; 205/290; 205/261; 205/299; 205/302; 205/311 |
International
Class: |
C25D 003/56; C25D
003/60; C25D 003/58; C25D 003/62; C25D 003/00; C25D 003/46; C25D
003/50; C25D 003/48; C25D 003/12; C25D 003/26; C25D 003/10; C25D
003/38 |
Claims
What is claimed is:
1. A metal plating bath comprising an additive consumption
inhibiting compound having a formula:
(R.sup.1--NHR.sup.2--OH).sub.nX where R.sup.1 and R.sup.2 are each
independently hydrogen, C.sub.1-C.sub.6 alkyl, n is 1 or 2, when n
is 1, X is HSO.sub.4.sup.-, H.sub.2PO.sub.4.sup.-, NO.sub.3.sup.-,
F.sup.-, Cl.sup.-, Br.sup.- or I.sup.- and when n is 2, X is
SO.sub.4.sup.2-; and metal salts of copper, gold, silver,
palladium, platinum, cobalt, cadmium, chromium, nickel, bismuth,
indium, tin, rhodium, lead, ruthenium, iridium, or alloys
thereof.
2. The metal plating bath of claim 1, wherein the C.sub.1-C.sub.6
alkyl comprises methyl, ethyl, propyl, isopropyl, butyl, isobutyl,
sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl,
hexyl, isohexyl, 3-methylpentyl, 2,2-dimethylbutyl, or
2,3-dimethylbutyl.
3. The metal plating bath of claim 1, wherein the additive
consumption inhibiting compound comprises hydroxylamine sulfate,
hydroxylamine nitrate, hydroxylamine chloride or mixtures
thereof.
4. The metal plating bath of claim 1, wherein the additive
consumption inhibiting compound comprises from about 0.001 g/L to
about 100 g/L of the bath.
5. The metal plating bath of claim 4, wherein the additive
consumption inhibiting compound comprises from about 0.01 g/L to
about 20.0 g/L of the bath.
6. The metal plating bath of claim 1, further comprising additives
comprising brighteners, levelers, hardeners, wetting agents,
malleability modifiers, ductility modifiers, deposition modifiers,
or suppressors.
7. The metal plating bath of claim 6, wherein the brighteners
comprise compounds having the formulas: HO.sub.3--S--R.sup.11--SH;
HO.sub.3S--R.sup.11--S--S--R.sup.11--SO.sub.3H, where R.sup.11 is
C.sub.1-C.sub.6 alky or an aryl group; or
HO.sub.3--Ar--S--S--Ar--SO.sub.- 3H, where Ar is phenyl or
naphthyl, the alky and aryl groups may be unsubstituted or
substituted with an alkyl group, halo or alkoxy group.
8. The metal plating bath of claim 7, wherein the brighteners
comprise 3-mercapto-propylsulfonic acid sodium salt,
2-mercapto-ethanesulfonic acid sodium salt, bissulfopropyl
disulfide, N,N-dimethyldithiocarbamic acid (3-sulfopropyl) ester
sodium salt, (O-ethyldithiocarbonato)-S-(3-sul- fopropyl)-ester
potassium salt, 3-[(amino-iminomethyl)-thio]-1-propanesulf- onic
acid, 3-(2-benzthiazolylthio)-1-propanesulfonic acid sodium salt or
mixtures thereof.
9. The plating bath of claim 6, wherein the levelers comprise
alkylated polyalkyleneimines, organo sulfo sulfones, dyes of the
phenazine class, phenazine azo dyes, or mixtures thereof.
10. The plating bath of claim 6, wherein the brighteners comprise
3-(benzthiazoyl-2-thio)-propylsulfonic acid sodium salt,
3-mercaptopropane-1-sulfonic acid sodium salt,
ethylenedithiodipropylsulf- onic acid sodium salt,
bis-(p-sulfopehnyl)-disulfide disodium salt,
bis-(.omega.-sulfobutyl)-disulfide disodium salt,
bis-(.omega.-sulfohydro- xypropyl)-disulfide disodium salt,
bis-(.omega.-sulfopropyl)-disulfide disodium salt,
bis-(.omega.-sulfopropyl)-sulfide disodium salt,
methyl-(.omega.-sulfopropyl) sodium salt,
methyl-(.omega.-sulfopropyl)-tr- isulfide disodium salt,
O-ethyl-dithiocarbonic acid-S-(.omega.-sulfopropyl- )-ester,
potassium salt thioglycolic acid, thiophosphoric
acid-O-ethyl-bis-(.omega.-sulfopropyl)-ester disodium salt,
thiophosphoric acid-tri(.omega.-sulfopropyl)-ester trisodium salt,
or mixtures thereof.
11. The plating bath of claim 6, wherein the suppressors comprise
carboxymethylcellulose, nonyphenolpolyglycol ether,
octandiolbis-(polyalkylene glycolether), octanolpolyalkylene
glycolether, oleic acidpolyglycol ester, polyethylenepropylene
glycol, polyethylene glycol, polyethylene glycoldimethylether,
polyoxypropylene glycol, polypropylene glycol, polyvinylalcohol,
polyethylene oxide, stearic acidpolyglycol ester, stearyl
alcoholpolyglycol ether, or mixtures thererof.
12. The metal plating bath of claim 1, wherein the bath has a pH of
from 0 to about 14.0.
13. The metal plating bath of claim 12, wherein the bath has a pH
of from 0 to about 8.0.
14. A copper metal electroplating bath comprising a copper salt,
and an additive consumption inhibiting compound having the formula:
(R.sup.1--NHR.sup.2OH).sub.nX where R.sup.1 and R.sup.2 are each
independently hydrogen, C.sub.1-C.sub.6 alkyl, n is 1 or 2, when n
is 1, X is HSO.sub.4.sup.-, H.sub.2PO.sub.4.sup.-, NO.sub.3.sup.-,
F.sup.-, Cl.sup.-, Br.sup.-, or I.sup.-, and when n is 2, X is
SO.sub.4.sup.2-.
15. The copper metal electroplating bath of claim 14, wherein the
C.sub.1-C.sub.6 alky comprises methyl, ethyl, propyl, isopropyl,
butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl,
neopentyl, tert-pentyl, hexyl, isohexyl, 3-methylpentyl,
2,2-dimethyl or 2,3-dimethylbutyl.
16. The copper metal electroplating bath of claim 14, wherein the
additive inhibiting compound comprises hydroxylamine sulfate,
hydroxylamine nitrate, hydroxylamine chloride, or mixtures
thereof.
17. The copper metal electroplating bath of claim 14, wherein the
additive consumption inhibiting compounds comprise from about 0.001
g/L to about 100 g/L of the bath.
18. The copper metal electroplating bath of claim 17, wherein the
additive consumption inhibiting compounds comprise from about 0.01
g/L to about 20.0 g/L of the bath.
19. The copper metal electroplating bath of claim 14, further
comprising additives comprising brighteners, levelers, hardeners,
wetting agents, malleability modifiers, ductility modifiers,
deposition modifiers, suppressors or mixtures thereof.
20. The copper metal electroplating bath of claim 19, wherein the
brighteners comprise compounds having the structural formula:
HO.sub.3--S--R.sup.11--SH;
HO.sub.3S--R.sup.11--S--S--R.sup.11--SO.sub.3H- , where R.sup.11 is
C.sub.1-C.sub.6 alkyl group or an aryl group; or
HO.sub.3--Ar--S--S--Ar--SO.sub.3H, where Ar is phenyl or naphthal;
the alkyl and aryl groups may be alkyl groups, halo or alkoxy.
21. The copper metal electroplating bath of claim 19, wherein the
levelers comprise alkylated polyalkyleneimines, organic sulfo
sulfonates, dyes of the phenazine class and phenazine azo dyes of
mixtures thereof.
22. The copper metal electroplating bath of claim 19, wherein the
copper metal salt comprises copper halides, copper sulfates, copper
alkane sulfonate, copper alkanol sulfonate, or mixtures
thereof.
23. The copper metal electroplating bath of claim 14, wherein the
bath has a pH of from about 0 to about 8.0.
24. A method for plating a metal on a substrate comprising:
contacting the substrate with a metal plating bath; and applying
sufficient current density to the plating bath to deposit the metal
on the substrate; the plating bath comprises a metal salt of the
metal copper, gold, silver, palladium, platinum, cobalt, cadmium,
chromium, nickel, bismuth, indium, tin, rhodium, iridium,
ruthenium, lead, or alloys thereof, and an additive consumption
inhibiting compound having the formula:
(R.sup.1--NHR.sup.2OH).sub.nX where R.sup.1 and R.sup.2 are each
independently hydrogen, C.sub.1-C.sub.6 alkyl, n is 1 or 2, when n
is 1, X is HSO.sub.4.sup.-, H.sub.2PO.sub.4.sup.-, NO.sub.3.sup.-,
F.sup.-, Cl.sup.-, Br.sup.-, or I.sup.-, and when n is 2, X is
SO.sub.4.sup.2-.
25. The method of claim 24, wherein the C.sub.1-C.sub.6 alkyl
comprises methyl, ethyl, propyl, isopropyl, butyl, isobutyl,
sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl,
hexyl isohexyl, 3-methylpentyl, 2,2-dimethylbutyl, or
2,3-dimethylbutyl.
26. The method of claim 24, wherein the additive consumption
inhibiting compound comprises hydroxylamine sulfate, hydroxylamine
nitrate, hydroxylamine chloride, or mixtures thereof.
27. The method of claim 24, wherein the additive consumption
inhibiting compound comprises from about 0.001 g/L to about 100 g/L
of the bath.
28. The method of claim 24, further comprising brighteners,
levelers, hardeners, wetting agents, malleability modifiers,
ductility modifiers, deposition modifiers, suppressants or mixtures
thereof.
29. The method of claim 24, wherein the brighteners comprise
compounds of the formula: HO.sub.3S--R.sup.11--SH;
HO.sub.3S--R.sup.11--S--S--R.sup.11- --SO.sub.3H, where R.sup.11 is
C.sub.1-C.sub.6 or an aryl group; and
HO.sub.3--Ar--S--S--Ar--SO.sub.3H, where Ar is phenyl or naphthyl;
and the alkyl and aryl groups may be unsubstituted or substituted
with an alkyl group, a halo or an alkoxy.
30. The method of claim 24, wherein the current density is from
about 1 ASF to about 1000 ASF.
31. The method of claim 24, wherein the substrate comprises a
printed wiring board, and integrated circuit, an electrical contact
surface, a connector, an electrolyte foil, a silicon wafer, a
semi-conductor, a lead frame, a optoelectronic component, a solder
bump on a wafer, a decorative article, a sanitary appliance and the
like.
32. A method for electroplating copper metal on a substrate
comprising: contacting the substrate with a metal plating bath; and
applying sufficient current density to the plating bath to deposit
the copper on the substrate; the copper metal plating bath
comprises a copper salt and an additive consumption inhibiting
compound having the formula: (R.sup.1--NHR.sup.2OH).sub.nX where
R.sup.1 and R.sup.2 are each independently hydrogen, or
C.sub.1-C.sub.6 alkyl, n is 1 or 2, when n is 1, X is
HSO.sub.4.sup.-, H.sub.2PO.sub.4.sup.-, NO.sub.3.sup.-, F.sup.-
Cl.sup.-, Br.sup.-, I.sup.-, and when n is 2, X is
SO.sub.4.sup.2-.
33. The method of claim 32, wherein the C.sub.1-C.sub.6 alkyl
comprises methyl, ethyl, propyl, isopropyl, butyl,isobutyl,
sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl,
hexyl, isohexyl, 3-methylpentyl, 2,2-dimethylbutyl, or
2,3-dimethylbutyl.
34. The method of claim 32, wherein the additive consumption
inhibiting compound comprises hydroxylamine sulfate, hydroxylamine
nitrate, hydroxylamine chloride, or mixtures thereof.
35. The method of claim 32, wherein the additive consumption
inhibiting compound comprises from about 0.001 g/L to about 100 g/L
of the bath.
36. The method of claim 32, further comprising brighteners,
levelers, hardeners, wetting agents, malleability modifiers,
ductility modifiers, deposition modifiers, suppressants or mixtures
thereof.
37. The method of claim 36, wherein the brighteners comprise
compounds of the formula: HO.sub.3S--R.sup.11--SH;
HO.sub.3S--R.sup.11--S--S--R.sup.11- , where R.sup.11 is
C.sub.1-C.sub.6 alkyl or an aryl group; or
HO.sub.3--Ar--S--S--Ar--SO.sub.3H, where Ar is phenyl or naphthyl;
the C.sub.1-C.sub.6 alkyl and aryl group may be unsubstituted or
substituted with an alkyl group, halo or alkoxy group.
38. The method of claim 32, wherein the substrate comprises a
printed wiring board, an integrated circuit, an electrical contact
surface, a connector, an electrolytic foil, a silicon wafer, a
semi-conductor, a lead frame, a optoelectronic component, a solder
bump on a wafer, a decorative article, a sanitary appliance, and
the like.
39. The method of claim 32, wherein the current density is from
about 1ASF to about 1000 ASF.
40. An apparatus comprising an electrical power source electrically
connected to an anode and a cathode such that an electrical current
can pass through the anode and cathode, the anode and the cathode
are in contact with a metal plating bath such that when the
electrical power source is operative a metal from the plating bath
plates onto the cathode, the metal plating bath comprises a salt of
a metal of copper, gold, silver, palladium, platinum, cobalt,
cadmium, chromium, nickel, bismuth, indium, tin, rhodium, lead,
ruthenium, iridium, or alloys thereof and an additive consumption
inhibiting compound having the formula:
(R.sup.1--NHR.sup.2OH).sub.nX where R.sup.1 and R.sup.2 are each
independently hydrogen, or C.sub.1-C.sub.6 alkyl, and n is 1 or 2,
when n is 1, X is HSO.sub.4.sup.-, H.sub.2PO.sub.4.sup.-,
NO.sub.3.sup.-, F.sup.-, Cl.sup.-, Br.sup.- or I.sup.-, and when n
is 2, X is SO.sub.4.sup.2-.
41. The apparatus of claim 40, wherein the additive consumption
inhibiting compound comprises from about 0.01 g/L to about 20.0 g/L
of the bath.
42. The apparatus of claim 40, wherein the metal plating bath
further comprises brighteners, levelers, hardeners, wetting agents,
malleability modifiers, ductility modifiers, deposition modifiers,
suppressors or mixtures thereof.
43. The apparatus of claim 40, wherein the anode is an insoluble or
soluble anode.
44. The apparatus of claim 43, wherein the insoluble anode
comprises metals of cobalt, nickel, ruthenium, rhodium, palladium,
iridium, or platinum.
45. The apparatus of claim 44, wherein the insoluble anode further
comprises metals of titanium, zirconium, hafnium, vanadium,
niobium, or tantalum.
46. The apparatus of claim 45, wherein the insoluble anode further
comprises beryllium, calcium, strontium, barium, scandium, yttrium,
lanthanum, or rare earth elements.
47. The apparatus of claim 43, wherein the insoluble anode
comprises tantalum with a coating of iridium dioxide.
48. The apparatus of claim 40, wherein the cathode comprises a
wiring board, an integrated circuit, an electrical contact surface,
a connector, an electrolytic foil, a silicon wafer, a
semi-conductor, a lead frame, an optoelectronic component, a solder
bump, a decorative article, a sanitary application and the like.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is directed to a plating bath and
method for improving deposition of a metal on a substrate. More
specifically, the present invention is directed to a plating bath
and method for improving deposition of a metal on a substrate by
including hydroxylamines in the plating bath that prevent the
degradation of plating bath components.
[0002] Deposition of a metal on a substrate is used in a variety of
industrial applications such as electroforming, electrorefining,
manufacture of copper powder, electroplating, electroless plating
and the like. The process of plating a substrate with a metal is
used in the production of decorative articles for sanitary
appliances, automobile parts, jewelry and furniture fittings, many
electrical devices and circuits such as printed wiring and circuit
boards, electrolytic foil, silicon wafer plating, and the like.
Examples of metals that may be plated on a substrate include
copper, gold, silver, palladium, platinum, zinc, tin, nickel, lead,
cobalt and alloys thereof. Although many metals are employed in
plating in the production of decorative articles and electrical
devices, copper is one of the most common metals plated. The
electronics industry extensively employs copper as a metal in the
manufacture of printed wiring and circuit boards as well as other
electronic articles.
[0003] The electronics industry has a number of requirements for
copper deposits on printed wiring boards. For example, copper
layers can not form any cracks when subject to thermal shock
(immersed at least once for 10 sec. in liquid tin/lead solder at
288.degree. C.). In addition, the copper layers must be smooth, and
as uniformly thick at all locations of a coated surface. Also,
deposition procedures must be easy to manage and economical.
[0004] Anodes, such as copper anodes, that may decompose during
electroplating are often used in the electroplating of copper. Such
anodes are known in the industry as soluble anodes. Soluble anodes
may be in the form of plates, bars or spheres. The plates and bars
are connected to a power supply with a suitable fastening means.
The spheres come in baskets that often consist of titanium. The
spheres are connected to a power supply with suitable fastening
means. Such anodes decompose at about the same rate during
deposition as the copper is deposited from the deposition bath, the
amount of copper in the deposition solution remains about constant.
Thus, copper replenishment is not necessary.
[0005] Another type of anode is the insoluble anode. Exterior
dimensions of insoluble anodes do not change during metal
deposition process. Such anodes consist of inert materials such as
titanium or lead that can be coated with catalytic metals such as
platinum to prevent high anodic overvoltages. Insoluble anodes are
preferred over the soluble anodes in the production of printed
wiring and circuit boards. Electroplating processes employing
insoluble anodes are more versatile than those using consumable
electrodes, permit higher plating speeds, require smaller apparatus
size and ease of maintenance, improved solution flow and agitation,
and insoluble anodes may be placed close to cathodes. Particularly
advantageous is the fact that the insoluble anode does not change
size (i.e., cell geometry remains fixed). Thus, more uniform
plating results are obtained. In addition, copper salts used to
provide a source of copper are often available as products of
etching procedures associated with the production of copper plated
devices. For example, in the production of circuit boards, a copper
layer is put down over an entire surface of an insulating substrate
and part of the copper etched off to produce the circuit board of
interest.
[0006] Plating metal on a substrate, such as electroplating with
copper, is used extensively in a variety of manufacturing
procedures. Copper plating is used to prevent corrosion on various
surfaces (i.e., iron surfaces), as a binding layer for additional
metal layers, to increase electrical or thermal conductivity and to
provide conducting paths in many electrical applications.
Electroplating with copper is employed in the manufacture of
electrical devices such as circuit boards, integrated circuits,
electrical contact surfaces and the like.
[0007] Plating metal is a complex process that involves multiple
ingredients in a plating bath. In addition to metal salts that
provide a source of metal, pH adjusters and surfactants or wetting
agents, many plating baths, such as electroplating baths, contain
chemical compounds that improve various aspects of the plating
process. Such chemical compounds or additives are auxiliary bath
components that are used to improve the brightness of the metal
plating, the physical properties of the plated metal especially
with respect to ductility and the micro-throwing power as well as
the macro-throwing power of the electroplating bath. Of main
concern are additives that have an effect on the bright finish,
leveling and uniformity of metal deposition on surfaces.
Maintaining bath concentrations of such additives within close
tolerances is important to obtain high quality metal deposits. Such
additives do breakdown during metal plating. The additives
breakdown due to oxidation at the anode, reduction at the cathode
and by chemical degradation. When additives breakdown during
plating, the breakdown products may result in metal layer deposit
characteristics that are less than satisfactory for industry
standards. Regular additions of additives based upon empirical
rules established by workers in the industry to try and maintain
optimum concentrations of the additives have been employed.
However, monitoring the concentrations of the additives that
improve metal plating is still very difficult because the additives
are present in small concentrations, i.e., parts per million of
solution, in the plating baths. Also the complex mixtures of the
additives and the degraded products formed from the additives
during plating complicate the replenishment process. Further,
depletion of specific additives is not always constant with time or
bath use. Accordingly, the concentration of the specific additives
is not accurately known and the level of the additives in the bath
eventually diminishes or increases to a level where the additives
are out of the acceptable range of tolerance. If the additive
content goes too far out of the range of tolerance, the quality of
the metal deposit suffers and the deposit may be dull in appearance
and/or brittle or powdery in structure. Other consequences include
low throwing power and/or plating folds with bad leveling.
Electroplating of through-hole interconnections in the manufacture
of multi-layer printed circuit boards is an example of where high
quality plating is required.
[0008] Stability and lifetime of a plating bath is very important.
Increased stability of the additives that improve metal plating
leads to longer lifetimes for plating baths. Plating baths having
longer lifetimes are economically very important. Frequent
replacement of plating baths, as mentioned above, as well as
disposal of baths containing degraded additives interrupts metal
plating operations. Such interruptions reduce product yield.
Accordingly, stable plating baths where breakdown of the additives
is prevented or reduced, are highly desirable.
[0009] U.S. Pat. No. 4,469,564 discloses a copper electroplating
process that allegedly increases the electroplating bath lifetime.
The patent states that the process may be employed with a soluble
or insoluble anode. A cation-permeable membrane surrounds the anode
to prevent organic additives from contacting the anode and being
oxidized by the anode. A disadvantage to such a process is that the
cation-permeable membranes are exposed to corrosive chemicals for
long periods of time that may cause the membranes to decompose. For
example, bath pH ranges may be less than 1.0 to as high as 11.0 and
higher. Also, bath pH ranges may fluctuate over time as bath
components are consumed or breakdown. Thus, workers in the art must
be selective in choosing a membrane with a chemical composition
that does not breakdown due to pH fluctuations during
electroplating. Additionally, as discussed above, electroplating
baths contain a variety of components. Components such as the
organic additives or their breakdown products may block pores in
the cation-permeable membrane preventing passage of cations through
the bath. Thus, workers must shut down the electroplating process
and replace the membrane. Both blockage of the pores and shutting
down the process lead to inefficiency in metal electroplating.
[0010] Japanese Patent Application 63014886 A2 discloses an acid
copper electroplating bath with chloride ions and also containing
transition metal ions in amounts of from 0.01-100 g/l. The
electroplating bath allegedly does not suffer from organic additive
consumption. Such organic additives include brighteners, leveling
agents, hardener, malleability and ductility modifiers, and
deposition modifiers.
[0011] EP 0402 896 discloses a method of stabilizing an organic
additive, such as a brightener, in an acid copper electroplating
solution. The process employs a soluble anode of copper chips in a
titanium basket. Transition metal salts of manganese, iron,
chromium, and titanium are added to the electroplating solution in
concentrations of not more than 5 g/l. The transition metals may
exist in at least two positive oxidation states, but are
substantially present in solution in their lowest common positive
oxidation state. The presence in solution of the positive oxidation
states of the transition metal ions allegedly stabilizes the
organic additives.
[0012] U.S. Pat. No. 6,099,711 discloses an electroplating process
employing an insoluble anode where metal ions, such as copper ions,
are replenished in the electroplating bath by employing a metal ion
generator in the form of a reversible redox system. Because an
insoluble anode is employed instead of a soluble anode, metal ions
are not replenished in the bath by dissolution of the anode. Thus,
the reversible redox system replenishes the metal ions. Iron (II)
and iron (III) compounds are used as an electrochemically
reversible redox system. Other redox systems disclosed in the
patent include metals of titanium, cerium, vanadium, manganese and
chrome. Such metals may be added to a copper depositing solution in
the form of iron (II) sulfate-heptahydrate, iron (II)
sulfate-nonahydrate, titanyl-sulfuric acid, cerium (IV) sulfate,
sodium metavanadate, manganese (II) sulfate or sodium chromate. The
patent states that the redox systems may be combined.
[0013] In addition to replenishing metal ions in the electroplating
bath, the patent states that the process prevents degradation of
organic additives to a significant extant. Degradation of large
amounts of organic additives in a bath occurs electrolytically at
the anode due to the anode potentials. Workers in the art believe
that the potential of the iron (II) to Iron (III) redox reaction
(about 0.530 V vs. SCE) provides an anode potential low enough to
prevent brightener oxidation at the anode. Thus, brightener
consumption is reduced. Such organic additives include brighteners,
levelers, and wetting agents. Brighteners that are employed include
water-soluble sulfur compounds and oxygen-containing high-molecular
weight compounds. Other additive compounds include nitrogenous
sulfur compounds, polymeric nitrogen compounds and/or polymeric
phenazonium compounds.
[0014] Although the patent alleges to replenish metal ions and to
reduce brightener consumption, the process, disclosed in the '711
patent, has disadvantages. Iron (III) may be reduced back to iron
(II) in the reversible redox reaction instead of oxidizing copper
to copper (II). Additionally, there is the problem that iron may
build-up in the system over time requiring shut down and cleaning
operations. Such operations reduce the efficiency of the process,
and raise the cost of the process. Another disadvantage to the
process is that the concentrations of the compounds in the redox
system must be arranged in such a way that a constant concentration
of metal ions is maintained in the deposition solution. Thus, there
is a narrow or nonexistent margin of error in the concentrations of
redox compounds in the deposition solution for the process to
operate. Accordingly, minor changes in the concentrations of the
redox compounds may hinder the operation of the process.
[0015] Japanese Patent Application 96199385 discloses an
electroplating method and solution containing fluoride-based
surfactants and organic additives such as brighteners. Addition of
the fluoride-based surfactants allegedly prevents brightener
consumption.
[0016] Although there are methods for preventing the degradation of
additives in metal plating baths, there is still a need for
additional methods of preventing the degradation of bath
additives.
SUMMARY OF THE INVENTION
[0017] The present invention is directed to a plating bath
containing hydroxylamines that inhibit the consumption of additives
in the plating bath, and a method of plating a metal on a substrate
employing the plating baths. Such hydroxylamines include compounds
having the following formula:
(R.sup.1--NHR.sup.2OH).sub.nX
[0018] where R.sup.1 and R.sup.2 are each independently hydrogen,
or C.sub.1-C.sub.6 alkyl, and n is 1 or 2, when n is 1, X is
HSO.sub.4.sup.-, H.sub.2PO4.sup.-, NO.sub.3.sup.-, F.sup.-,
Cl.sup.-, Br.sup.- or I.sup.-, and when n is 2, X is
SO.sub.4.sup.2-.
[0019] The foregoing hydroxylamines may be employed in metal
plating baths for plating copper, gold, silver, palladium,
platinum, cobalt, cadmium, chromium, nickel, bismuth, indium, tin,
rhodium, lead, iridium, ruthenium, or alloys thereof.
[0020] Advantageously, addition of the hydroxylamines to a plating
bath prevents or reduces degradation of metal plating bath
additives. Thus, the hydroxylamines provide for a plating bath that
has a long life, and a method of metal plating that is efficient.
Also, because the hydroxylamines of the present invention prevent
degradation of the additives, plating baths of the present
invention provide for uniform, high brightness metal layers with
good physical-mechanical characteristics on substrates.
[0021] Metal plating baths of the present invention may be employed
to plate metal layers on any substrate that may be metal plated.
Metal plating methods of the present invention involve passing a
current between two electrodes immersed in a bath containing
dissolved plating metal, bath additives and one or more
hydroxylamine consumption inhibiting compounds of the present
invention. Current is passed through the bath until a substrate is
plated with a desired thickness of metal.
[0022] The hydroxylamines and methods of the present invention may
be employed in any industry where metal plating is used. For
example, the metal plating baths may be employed in the manufacture
of electrical devices such as printed circuit and wiring boards,
integrated circuits, electrical contact surfaces and connectors,
electrolytic foil, silicon wafers for microchip applications,
semi-conductors and semi-conductor packaging, lead frames,
optoelectronics and optoelectronics packaging, solder bumps such as
on wafers, and the like. Also, the metal plating baths may be
employed for metal plating decorative articles for jewelry,
furniture fittings, automobile parts, sanitary appliances, and the
like. Further, the hydroxylamines also may be employed in waste
treatment methods.
[0023] The present invention also includes an apparatus composed of
an electrical power source, an anode, a cathode, and a metal
plating bath containing hydroxylamine consumption inhibiting
compounds. The cathode of the apparatus is the article that is
metal plated. The apparatus may be a vertical or a horizontal metal
plating apparatus.
[0024] A primary objective of the present invention is to provide
hydroxylamines that prevent or reduce degradation of additives in a
metal plating bath.
[0025] Another objective of the present invention is to provide a
metal plating bath that has a long operating life.
[0026] An additional objective of the present invention is to
provide for an efficient method for plating a metal on a
substrate.
[0027] A further objective of the present invention is to provide a
method for plating a uniform, high brightness metal layer with good
physical-mechanical properties on a substrate.
[0028] Still yet another objective of the present invention is to
provide an apparatus containing a hydroxylamine metal plating
bath.
[0029] Additional objectives and advantages may be ascertained by a
person of skill in the art after reading the detailed description
of the invention and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a diagrammatic illustration of an apparatus for
treating a workpiece by the vertical method in accordance with the
present invention; and
[0031] FIG. 2 is a diagrammatic illustration of an apparatus for
treating a workpiece by the horizontal method in accordance with
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Metal plating baths of the present invention contain
hydroxylamines that prevent or reduce the consumption of additives
added to metal plating baths to improve metal deposition on a
substrate. The metal plating baths may be employed in any suitable
process for plating a metal on a substrate. Such hydroxylamines
have the following formula:
(R.sup.1--NHR.sup.2OH).sub.nX
[0033] where R.sup.1 and R.sup.2 are each independently hydrogen or
C.sub.1-C.sub.6 alkyl, and n is 1 or 2, when n is 1, X is
HSO.sub.4.sup.-, H.sub.2PO.sub.4.sup.-, NO.sub.3.sup.-, F.sup.-,
Cl.sup.-, Br.sup.-, or I.sup.-and when n is 2, X is
SO.sub.4.sup.2-. The C.sub.1-C.sub.6 alkyl may be exemplified by
methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl,
tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl,
isohexyl, 3-methylpentyl, 2,2-dimethylbutyl, and
2,3-dimethylbutyl.
[0034] Preferred hydroxylamines are hydroxylamines where R.sup.1
and R.sup.2 are hydrogen such as hydroxylamine sulfate,
hydroxylamine nitrate and hydroxylamine chloride. The most
preferred are hydroxylamine sulfate and hydroxylamine nitrate. The
foregoing additive consumption inhibiting compounds may be obtained
commercially or may be synthesized according to methods well known
in the art.
[0035] The foregoing compounds may be employed in metal plating
baths for plating copper, gold, silver, palladium, platinum,
cobalt, chromium, cadmium, nickel, bismuth, indium, tin, iridium,
ruthenium, rhodium, lead or alloys thereof. Preferably, the
foregoing compounds may be employed in metal plating baths for
plating metals consisting of copper, gold, platinum, silver,
palladium, iridium, ruthenium, and cobalt. More preferably, the
foregoing additive consumption inhibiting compounds are employed in
metal plating baths for plating copper, iridium, and ruthenium.
Most preferably, the metal plating bath is for plating copper. Such
metals are included in the metal plating baths as their water
soluble salts.
[0036] Adding one or more of the hydroxylamines to metal plating
baths prevent or reduce the degradation of additives in the metal
plating baths. Preferably, the metal plating baths are
electroplating baths. The hydroxylamines are added in amounts of
generally from about 0.001 g/L to about 100 g/L of bath.
Preferably, the compounds are generally employed in plating baths
of from about 0.01 g/L to about 20.0 g/L. The additive preserving
hydroxylamine compounds may be added to plating baths by any
suitable method employed to add components to a bath. One method is
to admix the hydroxylamines into the plating bath with the other
bath components and additives.
[0037] Additives that the hydroxylamines prevent degradation of or
substantially reduce the amount of degradation include, but are not
limited to, brighteners, levelers, hardeners, wetting agents,
malleability, ductility and deposition modifiers, suppressors and
the like. The additive preserving hydroxylamine compounds of the
present invention are especially effective in preventing
degradation of brighteners and levelers. While the hydroxylamines
of the present invention may be employed to prevent the degradation
of additives employed in various metal plating baths, the
hydroxylamines are preferably employed to prevent the degradation
of additives employed in copper baths.
[0038] Examples of suitable brighteners employed in plating baths
of the present invention, include but are not limited to, compounds
that contain structural formulas: HO.sub.3S--R.sup.11--SH,
HO.sub.3S--R.sup.11--S--S--- R.sup.11--SO.sub.3H, where R.sup.11 is
C.sub.1-C.sub.6 or an aryl group, and
HO.sub.3S--Ar--S--S--Ar--SO.sub.3H, where Ar is phenyl or naphthyl.
Substituents of the alkyl and aryl groups may be, for example,
alkyl, halo and alkoxy. Examples of such brightening agents are
3-mercapto-propylsulfonic acid (sodium salt),
2-mercapto-ethanesulfonic acid (sodium salt), and bissulfopropyl
disulfide (BSDS). Such compounds are disclosed in U.S. Pat. Nos.
3,770,598, 4,374,709, 4,376,685, 4,555,315 and 4,673,469, all
incorporated herein in their entirety by reference. Such
polysulfides also may be employed to increase ductility of
deposited metal. Examples of other suitable brighteners, especially
for copper baths, include N,N-dimethylthiocarbamic acid
(3-sulfopropyl) ester, sodium salt (DPS),
(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-este- r, potassium salt
(OPX), 3-[(amino-iminomethyl)-thio]-1-propanesulfonic acid (UPS),
3-(2-benthiazolylthio)-1-propanesulfonic acid, sodium salt (ZPS)
and the thiol of bissulfopropyl disulfide (MPS).
[0039] Examples of levelers that may be employed in a plating bath
include, but are not limited to, alkylated polyalkyleneimines and
organic sulfo sulfonates. Examples of such compounds include
1-(2-hydroxyethyl)-2-imidazolidinethione (HIT), 4-mercaptopyridine,
2-mercaptothiazoline, ethylene thiourea, thiourea and alkylated
polyalkyleneimine. Such compounds are disclosed in U.S. Pat. Nos.
4,376,685, 4,555,315, and 3,770,598, the disclosures of which are
hereby incorporated herein in their entireties by reference.
[0040] Examples of other additives that may function as brighteners
in plating baths within the scope of the present invention include,
but are not limited to, sulfur compounds such as
3-(benzthiazoyl-2-thio)-propylsu- lfonic acid sodium salt,
3-mercaptopropane-1-sulfonic acid sodium salt,
ethylenedithiodipropylsulfonic acid sodium salt,
bis-(p-sulfophenyl)-disu- lfide disodium salt,
bis-(.omega.-sulfobutyl)-disulfide disodium salt,
bis-(.omega.-sulfohydroxypropyl)-disulfide disodium salt,
bis-(.omega.-sulfopropyl)-disulfide disodium salt,
bis-(.omega.-sulfo propyl)-sulfide disodium salt,
methyl-(.omega.-sulfopropyl)-disulfide sodium salt,
methyl-(.omega.-sulfopropyl)-trisulfide disodium salt,
O-ethyl-dithiocarbonic acid-S-(.omega.-sulfopropyl)-ester,
potassium salt thioglycoli acid, thiophosphoric
acid-O-ethyl-bis-(.omega.-sulfpropyl)-es- ter disodium salt,
thiophosphoric acid-tris(.omega.-sulfopropyl)-ester trisodium salt,
and the like.
[0041] Examples of oxygen containing high molecular weight
compounds that may be employed as suppressors include
carboxymethylcellulose, nonylphenolpolyglycol ether,
octandiolbis-(polyalkylene glycolether), octanolpolyalkylene
glycolether, oleic acidpolyglycol ester, polyethylenepropylene
glycol, polyethylene glycol, polyethylene glycoldimethylether,
polyoxypropylene glycol, polypropylene glycol, polyvinylalcohol,
stearic acidpolyglycol ester, stearyl alcoholpolyglycol ether,
polyethylene oxide and the like.
[0042] Dyes of the phenazine class (Safranine type) and phenazine
azo dyes (Janus Green B type) may be employed as levelers.
Polyethers are used to improve thickness and uniformity of metal
plating.
[0043] Brighteners and levelers are added to plating baths in
amounts of from about 1 part per billion to about 1.0 g/L of bath.
Preferably, brighteners and levelers range from about 10 parts per
million to about 500 parts per million. Ranges for bath components
may vary from one bath composition to the next. Thus, the foregoing
weight ranges for the additives are general ranges.
[0044] Examples of suitable wetting agents or surfactants that may
be employed in plating baths of the present invention include
nonionic surfactants such as alkyl phenoxy polyethoxyethanols.
Other suitable wetting agents containing multiple oxyethylene
groups also may be employed. Such wetting agents include compounds
of polyoxyethylene polymers having from as many as 20 to 150
repeating units. Such compounds also may perform as suppressors.
Also included in the class of polymers are block copolymers of
polyoxyethylene and polyoxypropylene. Surfactants and wetting
agents are added in conventional amounts.
[0045] In addition to the additives, other plating bath components
are included in plating baths as a source of metal ions, pH
adjusters, such as inorganic acids, and a source of halide ions.
Generally, plating baths are aqueous. The pH range of the baths may
range from 0 to about 14, preferably from 0 to about 8. Wetting
agents employed in plating baths and amounts employed in such baths
are well known in the art. Inorganic acids employed include, but
are not limited to, sulfuric acid, hydrochloric acid, nitric acid,
phosphoric acid and the like. Sulfuric acid is a preferred acid.
Halogen ions are optional. Halogen ions employed in plating baths
include chloride, fluoride, and bromide. Such halides are added
into the bath as a water soluble salt. Chloride is preferred, and
is introduced into the bath as sodium chloride, preferably as HCl.
Water soluble salts of metals provide a source of the metal to be
plated on a substrate. Such water soluble salts include metal salts
of copper, nickel, chromium, gold, silver, cadmium, platinum,
palladium, cobalt, bismuth, tin, rhodium, iridium, ruthenium, lead,
and indium. Solder also may be plated with the plating baths of the
present invention.
[0046] Copper is the preferred metal to be plated with the baths of
the present invention. Preferably, the copper is electroplated.
Copper that is useful may be in the form of any solution soluble
copper compound. Suitable copper compounds include, but are not
limited to, copper halides, copper sulfates, copper alkane
sulfonate, copper alkanol sulfonate, and the like. When copper
halide is used, chloride is the preferred halide. Preferred copper
compounds are copper sulfate, copper alkane sulfonate, or mixtures
thereof. The more preferred are copper sulfate, copper methane
sulfonate or mixtures thereof. Copper compounds useful in the
present invention are generally commercially available or may be
prepared by methods known in the literature. When copper is plated
on a substrate the pH of the bath may range from 0 to about 14.
Preferably the bath ranges from a pH of from 0 to about 8.0.
[0047] Metal ions range in concentration in the plating baths of
from about 0.010 g/L to about 200 g/L, preferably from about 0.5
g/L to about 100 g/L. When copper is employed the amount of copper
may range from about 0.01 to about 100 g/L. Preferably copper is
used in the bath in amounts from about 0.10 g/L to about 50 g/L.
When the bath of the present invention is used in a non-high speed
plating process, the amount of copper present in the bath ranges
preferably from about 0.02 g/L to about 25 g/L. When the bath of
the present invention is used in a high speed plating process, the
amount of copper present in the bath ranges from about 1.0 g/L to
about 100 g/L, preferably from about 2.0 g/L to about 50 g/L.
[0048] Halide ions, especially for copper baths, range in
concentration of from 0 mg/L to about 1 g/L, preferably from about
1.0 mg/L to about 150 mg/L. Acids are added to the plating baths to
obtain a pH range of from about 0 to about 8.0, most preferably
from about less than 1.0 to about 2.0. Accordingly, acids are added
in amounts of from about 10 g/L to about 600 g/L, preferably from
about 15 g/L to about 500 g/L.
[0049] An example of an acid copper electroplating bath for
practicing the present invention has a composition as follows:
1 Copper Ions (as Copper Sulfate) 0.01 to 50 g/L Sulfuric Acid
(Concentrated) .sup. 15 to 500 g/L Chloride Ions (as Sodium
Chloride) 1 ppm to 150 ppm Additives As Required Hydroxylamine
sulfate 0.1 to 10 g/L Water To 1 liter
[0050] While the hydroxylamine compounds may be employed to prevent
degradation of additives in any suitable plating bath where a
substrate is to be metal plated, preferably, the additive
preserving hydroxylamine compounds are employed in electroplating
baths. Such electroplating baths are employed in electrodeposition
of a metal on a substrate such as in the manufacture of printed
wiring boards and silicon wafers used in microchip applications,
and in the manufacture of other components for electrical devices.
Electroplating processes involve passing current through an anode,
an electroplating solution, and a cathode for a sufficient amount
of time to metal plate a substrate to a desired thickness. The
anode may be a soluble anode (composed of a metal such as copper
that dissolves and replenishes the electroplating bath as plating
occurs). Alternatively, an insoluble anode (composed of an inert
material such as platinum, platinized titanium, lead, and the like)
may be employed. Preferably, the present invention is employed in
plating processes employing an insoluble anode where electroplating
rates are greater and problems associated with additive consumption
(often oxidation at the anode) are greater than with processes
employing soluble anodes.
[0051] Examples of useful insoluble anodes are anodes that have
surfaces with oxides of iridium and tantalum. Such anodes have from
about 20 to about 90 moles percent of iridium with the remainder
tantalum. Preferred is about 60 to about 90 mole percent of iridium
with the remainder tantalum. The anodes are made by coating iridium
and tantalum on a conducting substrate such as a titanium
substrate.
[0052] Other suitable anodes include anodes composed of at least
about 10 mole percent of group VIII metals, at least about 10 mole
percent valve metal and at least about 5 mole percent binder metal.
Group VIII metals include cobalt, nickel, ruthenium, rhodium,
palladium, iridium and platinum. Valve metals include titanium,
zirconium, hafnium, vanadium, niobium and tantalum. Binder metals
include beryllium, calcium, strontium, barium, scandium, yttrium,
lanthanum and rare earth elements with atomic numbers 58 through
71. Especially useful is an oxide composition with from about 5 to
about 20 mole percent of barium, and the ratio of iridium to
tantalum between about 1/4 and about 4. Such a composition is about
5 mole percent barium, from about 30 to about 40 mole percent
iridium with the remainder tantalum. Additionally, osmium, silver
and gold or their oxides may be employed in insoluble anodes.
[0053] As mentioned above, plating baths of the present invention
may be employed in any suitable plating process where metal is
plated on a substrate. Examples of such plating processes include,
but are not limited to, direct current (DC) electroplating and
pulse electroplating plating. Plating baths of the present
invention are especially suitable for plating substrates in the
manufacture of electronic devices such as in the printed wiring
board industry and the manufacture of silicon semiconductor
wafers.
[0054] In an electroplating process, the substrate to be plated is
used as a cathode. A soluble or preferably an insoluble anode, as
described above, is employed as a second electrode. A process of
pulse plating, DC (direct current) plating or a combination of both
is employed. Such methods of plating are known in the art. Current
densities and electrode surface potentials may vary depending on
the specific substrate to be plated. Generally, anode and cathode
current densities may vary within a range of from about 1 to about
1000 amps/ft.sup.2 (ASF). Plating baths are maintained in a
temperature range of from about 20.degree. C. to about 110.degree.
C. Specific ranges vary depending upon which metal is being plated.
Such temperature ranges are well known in the art. Copper baths may
range from about 20.degree. C. to about 80.degree. C. Acid copper
baths range in temperature of from about 20.degree. C. to about
50.degree. C. Plating is continued for a time sufficient to form a
deposit of desired thickness. Generally, plating time for a circuit
board is from about 45 minutes to about 8 hours. For circuit board
manufacture, a desired thickness may range from about 0.5 to about
3.0 mils. More often layer thickness ranges from about 1.0 to about
1.5 mils.
[0055] Both vertical and horizontal plating processes may be
employed. In the vertical process, the substrate, such as a printed
circuit or wiring board, is sunk in a vertical position into a
container containing a plating bath solution of the present
invention. The substrate, which functions as a cathode, is situated
in the vertical position opposite at least one anode, preferably an
insoluble anode. The substrate and the anode are connected to a
current source. Instead of regulating the current density with the
current source, there also can be a voltage arrangement where the
voltage between the substrate and the anode is regulated. Plating
solution is directed continuously through the container by means of
transporting equipment such as a pump.
[0056] An example of an arrangement that is suitable for treating a
substrate or workpiece by a vertical method and apparatus is
represented in FIG. 1. Apparatus 10 is composed of container 12
with metal plating bath 14 that contains a hydroxylamine that
prevents additive consumption. The metal plating bath 14 may be
used, for example, for copper plating and contains previously
mentioned components and additives.
[0057] Workpiece 16 (cathode), for example a circuit board, and
anodes 18, for example insoluble titanium anodes coated with
iridium dioxide, are immersed into metal plating bath 14. Workpiece
16 and anodes 18 are connected electrically to current source 20.
Instead of regulating the current with the current source, a
voltage arrangement (not shown) may be used to regulate voltage
between the workpiece 16 and anodes 18. Metal plating bath 14 is
directed continuously to second container or reservoir 22 by a
transporting means (not shown) such as a pump. Reservoir 22, which
metal plating bath 14 flows through, replenishes metal bath
components and additives in metal plating bath 14 such as copper
salts, brighteners, levelers, hydroxylamine additive consumption
inhibitors and the like.
[0058] In the horizontal plating process, the substrate is
transported through a conveyorized unit in a horizontal position
with a horizontal direction of movement. Plating bath is injected
continuously from below and/or from above onto the substrate by
means of splash nozzles or flood pipes. The anodes are arranged at
a spacing relative to the substrate and are brought into contact
with the plating bath by means of a suitable device. The substrate
is transported by means of rollers or plates.
[0059] An example of a horizontal method and apparatus that may be
employed to practice the present invention is illustrated in FIG.
2. Spray chamber 24 of apparatus 46 is formed with slots 26 at
either end to allow for continuous conveyance of panel 28, such as
a circuit board panel to A be metal plated, to enter and leave
chamber 24. While a circuit board panel is illustrated, any
suitable surface that may be plated by a horizontal apparatus lies
within the scope of the present invention. Panel 28 is supported
for moving in the direction of the arrow by idler rollers 30. A
series of roller brushes 32 is positioned to contact both upper and
lower surfaces of panel 28 with a series of anodes 34 positioned to
contact roller brushes 32 on the side of idler rollers 30 away from
panel 28. Anodes 34 are formed of any suitable metal such as
titanium coated with iridium dioxide. While any suitable anode may
be employed, an insoluble anode such as the titanium coated iridium
dioxide anode is preferred. Anodes 34 are positioned such that the
anodes touch the upper set of idler rollers 30 from above, and
touch the lower set of idler rollers 30 from below. All of anodes
34 are electrically connected in parallel to a positive terminal of
power supply 36. A negative terminal of power supply 36 is
connected to panel 28 (cathode) that is to be plated. Spray jets 38
which are connected to reservoir 42 containing metal plating bath
40 by means of lines 44 are arranged to spray metal plating bath 40
down on both anodes 34 and roller brushes 32 as well as panel 28
between roller brushes 32. Arrows show the path for the metal bath
flow through lines 44. Metal plating bath 40 is pumped from
reservoir 42 through lines 44 by a pumping means (not shown) in
mechanical connection to reservoir 42. The transport mechanism
means (not shown) for panel 28 is a conveyor-type mechanism that
provides for a continuous movement of panel 28 through chamber 24
while maintaining electrical contact between the negative pole of
power supply 36 and panel 28.
[0060] By preventing or reducing the amount of additive breakdown,
the hydroxylamine compounds provide for improved brightness of
plated metal and improved physical-mechanical properties of the
plated metal. Metal layers plated with baths of the present
invention are not brittle or powdery in structure. Also, metal
layers plated with the baths of the present invention have good
throwing power and no appreciable plating folds. Such properties
for metal layers are especially desirable for through-holes in
printed circuit and wiring boards. Additionally, because the select
compounds prevent or substantially reduce the amount of additives
degraded during metal plating, replenishment of the additives is
rarely, if ever, needed. Also, prevention of additive breakdown
permits metal plating operations to continue for longer periods
without bath replacement. Further, because the hydroxylamine
compounds inhibit degradation of additives, costly semi-permeable
membranes can be eliminated from apparatus during plating. Thus,
plating baths containing the hydroxylamine compounds provide for a
more efficient and economic method for metal plating than baths
without the hydroxylamine compounds. Accordingly, metal plating
baths of the present invention provide for an improved metal
plating process. All numerical ranges disclosed above are inclusive
and combinable.
[0061] While the present invention is described with an emphasis on
electroplating processes in the printed wiring board industry, the
present invention may be employed in any suitable plating process.
The hydroxylamine compounds may be employed in metal plating baths
in the manufacture of electrical devices such as printed circuit
and wiring boards, integrated circuits, electrical contact surfaces
and connectors, electrolytic foil, silicon wafers for microchip
applications, semi-conductors and semi-conductor packaging, lead
frames, optoelectronics and optoelectronic packaging, solder bumps
such as on wafers, and the like. Additionally, the metal plating
baths may be employed for metal plating decorative articles for
jewelry, furniture fittings, automobile parts, sanitary appliances,
and the like. Further, the additive consumption inhibiting
compounds may be employed in waste treatment methods.
[0062] The following examples are provided to better describe the
present invention, and are not intended to limit the scope of the
invention.
EXAMPLE 1
[0063] Brightener consumption is determined in an electroplating
bath using a Hull Cell. Each Hull Cell employed is a
hydrodynamically controlled Hull Cell (HCHC). The bath is a copper
plating bath containing the following components:
2 Copper Sulfate Pentahydrate 80 g/L Sulfuric Acid (concentrated)
225 g/L Chloride (as sodium chloride) 50 ppm Bissulfopropyl
Disulfide (brightener) 1 mg/L Water To 1 L
[0064] The first Hull Cell experiment has a soluble copper anode
and a copper clad glass epoxy panel as a cathode. The second and
third Hull Cells employed have an insoluble iridium dioxide anode
in place of the soluble copper anode. In addition to the above bath
components, the third Hull Cell contains about 1 g/L of
hydroxylamine sulfate. Copper is plated on the copper clad glass
epoxy cathode. Brightener consumption is measured as percent matte
on the surface of plated copper. Matte as defined within the scope
of the present invention means a dull or non-reflective surface
appearance on the copper plated on the cathode.
[0065] Each Hull Cell experiment is operated at about 3 amps for
about 2 minutes, and then for about 10 minutes. The percent matte
on the plated copper surface is determined after about 2 minutes
and after about 10 minutes. The first Hull Cell experiment with the
soluble copper anode shows about the same percentage of matte on
the copper metal after about 2 minutes as after about 10 minutes.
Accordingly, very little brightener is consumed between about 2
minutes and about 10 minutes with a soluble copper anode.
[0066] In the second experiment where an iridium dioxide insoluble
anode is used, about 30% of the copper metal is matte after about 2
minutes. After about 10 minutes, almost all of the copper metal is
matte. Accordingly, after about 10 minutes almost all of the
brightener is consumed with an insoluble iridium dioxide anode.
[0067] In the third experiment, about 1.0 gm/L of hydroxylamine
sulfate is added to the copper plating bath to act as a brightener
consumption inhibitor. The matte on the copper plated on the
cathode is about the same percentage after both the about 2 minute
period and the about 10 minute period. Accordingly, very little
brightener is consumed between the about 2 minute period and the
about 10 minute period.
[0068] Brighter consumption is especially problematic when an
insoluble anode is employed in contrast to a soluble copper anode.
However, when hydroxylamine sulfate is added to the copper plating
bath with an insoluble anode, brightener consumption is
inhibited.
* * * * *