U.S. patent application number 16/257132 was filed with the patent office on 2020-07-30 for indium electroplating compositions and methods for electroplating indium on nickel.
The applicant listed for this patent is Rohm and Haas Electronic Materials LLC. Invention is credited to Margit CLAUSS, Adolphe FOYET.
Application Number | 20200240029 16/257132 |
Document ID | 20200240029 / US20200240029 |
Family ID | 1000003899439 |
Filed Date | 2020-07-30 |
Patent Application | download [pdf] |
United States Patent
Application |
20200240029 |
Kind Code |
A1 |
FOYET; Adolphe ; et
al. |
July 30, 2020 |
INDIUM ELECTROPLATING COMPOSITIONS AND METHODS FOR ELECTROPLATING
INDIUM ON NICKEL
Abstract
Indium electroplating compositions electroplate substantially
defect-free, whisker-free, uniform indium layers which have a
smooth surface morphology on nickel. The indium electroplating
compositions are environmentally friendly and include select amino
acids to provide for the smooth, uniform and defect-free indium
deposits.
Inventors: |
FOYET; Adolphe; (Luzern,
CH) ; CLAUSS; Margit; (Kriens, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rohm and Haas Electronic Materials LLC |
Marlborough |
MA |
US |
|
|
Family ID: |
1000003899439 |
Appl. No.: |
16/257132 |
Filed: |
January 25, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 3/54 20130101; C25D
3/56 20130101 |
International
Class: |
C25D 3/54 20060101
C25D003/54; C25D 3/56 20060101 C25D003/56 |
Claims
1. An indium electroplating composition consisting of water; one or
more sources of indium ions; one or more acids selected from the
group consisting of inorganic acids, alkane sulfonic acids, and
salts of the acids, wherein the inorganic acids are selected from
the group consisting of sulfamic acid and sulfuric acid; and one or
more amino acids selected from the group consisting alanine,
arginine, aspartic acid, asparagine, glutamic acid, glycine,
glutamine, leucine, histidine, lysine, threonine, isoleucine,
serine, and valine; optionally one or more alloying metal; and
optionally one or more pH adjuster.
2. The indium electroplating composition of claim 1, wherein the
one or more amino acids are selected from the groups consisting of
glycine, arginine, lysine, glutamine, serine, histidine and
asparagine.
3. The indium electroplating composition of claim 1, wherein the
one or more amino acids are in amounts of at least 5 g/L.
4. The indium electroplating composition of claim 3, wherein the
one or more amino acids are in amounts of 10 g/L to 200 g/L.
5. The indium electroplating composition of claim 1, wherein the
one or more acids are inorganic acids selected from the group
consisting of sulfamic acid and sulfuric acid.
6. The indium electroplating composition of claim 1, wherein the
one or more alloying metals is selected from the group consisting
of tin, silver, bismuth and copper.
7. A method of electroplating indium on nickel comprising: a.
providing a substrate comprising a nickel layer adjacent to a
copper or copper alloy layer; b. contacting the substrate
comprising the nickel layer adjacent to the copper or the copper
alloy layer with an indium electroplating composition consisting of
water; one or more sources of indium ions; one or more acids
selected from the group consisting of inorganic acids, alkane
sulfonic acids, and salts of the acids, wherein the inorganic acids
are selected from the group consisting of sulfamic acid and
sulfuric acid; and one or more amino acids selected from the group
consisting alanine, arginine, aspartic acid, asparagine, glutamic
acid, glycine, glutamine, histidine, leucine, lysine, threonine,
isoleucine, serine, and valine; optionally one or more alloying
metal; and one or more pH adjuster; and c. electroplating an indium
layer adjacent to the nickel layer of the substrate with the indium
electroplating composition.
8. The method of electroplating indium on nickel of claim 8,
wherein the indium layer is greater than 0.1 .mu.m.
9. The method of electroplating indium on nickel of claim 8,
wherein the indium layer is 0.2-1 .mu.m.
10. The method of electroplating indium or indium alloy of claim
10, wherein the one or more amino acids are selected from the
groups consisting of glycine, lysine, glutamine, histidine, serine,
asparagine and arginine.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to indium electroplating
compositions and methods for electroplating indium on nickel layers
where the indium deposit is uniform, substantially void-free,
whisker-free and has a smooth surface morphology. More
specifically, the present invention is directed to acid indium
electroplating compositions and methods of electroplating indium on
nickel layers where the indium deposit is uniform, substantially
void-free, whisker-free and has a smooth surface morphology,
wherein the indium electroplating compositions are environmentally
friendly and include select amino acids to provide the uniform
matte, substantially void-free, whisker-free and smooth surface
morphology indium deposit.
BACKGROUND OF THE INVENTION
[0002] Electrolytic indium is very attractive in the connectors
industry for press-fit applications. Indium can be used as a
replacement metal for tin. Tin usually grows whiskers under stress
conditions. As electronic components become smaller, it is
important to eliminate the risk of whisker formation which can
create electrical short circuits. The advantage of indium over tin
is that indium is less susceptible to whisker formation even after
reflow.
[0003] Connector pins (copper alloy) for press-fit applications are
initially coated with nickel followed by indium flash adjacent to
the nickel. The thickness of indium layer is generally from 0.2-1
.mu.m. The problem is that many electrolytic indium processes are
unable to plate such a thin layer with uniform thickness
distribution and with good adhesion on the nickel without using a
strike layer (adhesion promotor coating). Such strike layers can
have a thickness of 1-100 nm.
[0004] The ability to reproducibly plate void-free uniform matte
indium of target thickness and smooth surface morphology on nickel
layers is challenging. Indium reduction occurs at potentials more
negative than that of proton reduction, and significant hydrogen
bubbling at the cathode causes increased surface roughness. Indium
(1.sup.+) ions, stabilized due to the inert pair effect, formed in
the process of indium deposition catalyze proton reduction and
participate in disproportionation reactions to regenerate Indium
(3.sup.+) ions. In the absence of a complexing agent, indium ions
begin to precipitate from solutions above pH>2. Plating indium
on nickel is challenging because nickel is a good catalyst for
proton reduction and is more noble than indium, nickel can cause
corrosion of indium in a galvanic interaction. Indium may also form
undesired intermetallic compounds with nickel. Another problem with
indium plating is the generation of hydrogen gas. Such hydrogen gas
generation can result in rough and irregular indium deposits
unsuitable for electronic components and devices.
[0005] In addition, many conventional indium plating baths include
environmentally unfriendly additives required to enable acceptable
indium plating performance, such as certain suppressors, many
levelers, grain refiners, certain buffers and compounds used to
inhibit hydrogen evolution during plating. Many governments around
the world are passing stricter environmental laws and regulations
with respect to how chemical waste is treated and the types of
chemicals industries may use in development and manufacturing
processes. For example, in the European Union the regulation
Registration, Evaluation, Authorization and Restriction of
Chemicals, known as REACh, has banned numerous chemicals or is in
the process of banning chemicals used in plating baths from
substantial industrial use.
[0006] Accordingly, there is a need for improved indium
compositions for electroplating indium metal layers on nickel
substrates and which are environmentally friendly.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to an indium
electroplating composition consisting of water; one or more sources
of indium ions; one or more acids selected from the group
consisting of inorganic acids, alkane sulfonic acids, and salts of
the acids, wherein the inorganic acids are selected from the group
consisting of sulfamic acid and sulfuric acid; and one or more
amino acids selected from the group consisting alanine, arginine,
aspartic acid, asparagine, glutamic acid, glycine, glutamine,
histidine, leucine, lysine, threonine, isoleucine, serine, and
valine; optionally one or more alloying metal; and optionally one
or more pH adjuster.
[0008] The present invention is also directed to a method of
electroplating indium on nickel comprising: [0009] a) providing a
substrate comprising a nickel layer adjacent to a copper or copper
alloy layer; [0010] b) contacting the substrate comprising the
nickel layer adjacent to the copper or the copper alloy layer with
an indium electroplating composition consisting of water; one or
more sources of indium ions one or more acids selected from the
group consisting of inorganic acids, alkane sulfonic acids, and
salts of the acids, wherein the inorganic acids are selected from
the group consisting of sulfamic acid and sulfuric acid; and one or
more amino acids selected from the group consisting alanine,
arginine, aspartic acid, asparagine, glutamic acid, glycine,
glutamine, histidine, leucine, lysine, threonine, isoleucine,
serine, and valine; optionally one or more alloying metal; and
optionally one or more pH adjuster; and [0011] c) electroplating an
indium layer adjacent to the nickel layer of the substrate with the
indium electroplating composition.
[0012] The aqueous acid indium electroplating compositions and
methods of the present invention can be used to plate indium metal
layers having a thickness of >0.1 .mu.m on nickel without using
a strike. The current efficiency for the aqueous acid indium
electroplating compositions is high, and the indium deposit is
uniform and matte, substantially void-free, whisker-free, has a
smooth surface morphology and shows good adhesion on Nickel. Post
annealing of the substrates with the indium deposit shows minor to
substantially no dewetting. During indium electroplating hydrogen
gas evolution is substantially inhibited to enable smooth uniform
matte indium deposits. The indium electroplating compositions
contain only registered and REACh compliant compounds.
DETAILED DESCRIPTION OF THE INVENTIONS
[0013] As used throughout the specification, the following
abbreviations have the following meanings, unless the context
clearly indicates otherwise: .degree. C.=degrees Centigrade;
g=gram; mg=milligram; L=liter; A=amperes; dm=decimeter;
ASD=A/dm.sup.2=current density; m=micron=micrometer; indium
ion=In.sup.3+; nm=nanometers=10.sup.-9 meters;
.mu.m=micrometers=10.sup.-6 meters; M=molar; min.=minute;
IC=integrated circuits; XRF=X-ray fluorescence; and e.g.
=example.
[0014] The terms "depositing", "plating" and "electroplating" are
used interchangeably throughout this specification. The term
"aqueous" means water based or the solvent of the composition is
water. The term "adjacent` means in direct contact or two separate
surfaces or planes having a common interface. The term "interface"
means point(s) of contact between two surfaces or planes. The term
"plane" means a substantially flat surface such that a straight
line joining any two points on it lies wholly in it. The term
"surface" means outer area or upper most area of an article or
structure. The term "copolymer" is a compound composed of two or
more different monomers or oligomers. The term "dewetting" means
the retraction of indium plating at some position on the nickel
surface after reflow, wherein this position of the nickel is called
the non-wettable area and occurs when adhesion is poor. The term
"matte" means dull and flat in appearance without shine. Unless
otherwise noted all plating baths are aqueous solvent based, i.e.
water based, plating baths. All amounts are percent by weight and
all ratios are by moles, unless otherwise noted. All numerical
ranges are inclusive and combinable in any order except where it is
logical that such numerical ranges are constrained to add up to
100%.
[0015] The aqueous acid indium compositions of the present
invention include one or more sources of indium ions which are
soluble in an aqueous environment. Such sources include, but are
not limited to, indium salts of alkane sulfonic acids, such as
methanesulfonic acid, ethanesulfonic acid, and butane sulfonic
acid, indium salts of sulfamic acid, sulfate salts of indium,
chloride and bromide salts of indium, nitrate salts, hydroxide
salts, indium oxides, fluoroborate salts, indium salts of
carboxylic acids, such as citric acid, acetoacetic acid, glyoxylic
acid, pyruvic acid, glycolic acid, malonic acid, hydroxamic acid,
iminodiacetic acid, salicylic acid, glyceric acid, succinic acid,
malic acid, tartaric acid, hydroxybutyric acid, indium salts of
amino acids, such as arginine, aspartic acid, asparagine, glutamic
acid, glycine, glutamine, leucine, lysine, threonine, isoleucine,
and valine. Preferably, the source of indium ions is one or more
indium salts of sulfuric acid, sulfamic acid, and alkane sulfonic
acids. More preferably, the source of indium ions is one or more
indium salts of sulfuric acid, sulfamic acid and methane sulfonic
acid. Most preferably, the source of indium ions is indium
sulfate.
[0016] The indium ions from the water-soluble salts of indium are
included in the compositions in sufficient amounts to provide an
indium deposit of desired thickness. Preferably, the indium ions
from the water-soluble indium salts are included in the
compositions in amounts of 5 g/L to 70 g/L, more preferably, from
10 g/L to 50 g/L, most preferably, from 10 g/L to 40 g/L.
[0017] One or more amino acids selected from the group consisting
of alanine, arginine, aspartic acid, asparagine, glutamic acid,
glycine, glutamine, histidine, leucine, lysine, threonine,
isoleucine, serine, and valine are included in the indium plating
compositions of the present invention. Preferably, the indium
electroplating compositions of the present invention are free of
amino acids having sulfur and sulfur functional groups. Preferably,
the one or more amino acids are selected from the group consisting
of arginine, aspartic acid, asparagine, glycine, glutamine, lysine,
serine and histidine, more preferably, the one or more amino acids
are selected from the group consisting of arginine, asparagine,
glycine, aspartic acid, lysine and serine, even more preferably,
the one or more amino acids are selected from the group consisting
of glycine, lysine and serine. Most preferably, the amino acid is
glycine. Including one or more of the amino acids in the indium
electroplating compositions of the present invention inhibits
hydrogen gas evolution during indium electroplating and stabilizes
indium ions such that no substantial precipitation of the indium
ions occurs at a relatively high pH of >1.5.
[0018] One or more of the foregoing amino acids can be included in
the indium plating compositions of the present invention in amounts
of 5 g/L or greater. Preferably, the one or more amino acids of the
present invention can be included in amounts of 10 g/l to 200 g/L,
more preferably, the amino acids can be included in amounts of 25
g/L to 150 g/L (e.g. 30 g/L to 120 g/L, 30 g/L to 100 g/L or 25 g/L
to 75 g/L), even more preferably, the amino acids can be included
in amounts of 25 g/l to 100 g/L (e.g. 30 g/L to 100 g/L or 40 g/L
to 100 g/L), most preferably, the amino acids are included in
amounts of 50 g/L to 100 g/L (e.g. 50 g/L to 90 g/L).
[0019] One or more acids selected from the group consisting of
inorganic acids, alkane sulfonic acids, and salts of the acids,
wherein the inorganic acids are selected from the group consisting
of sulfamic acid and sulfuric acid. Alkane sulfonic acids include,
but are not limited to methanesulfonic acid, ethanesulfonic acid,
and butane sulfonic acid. Preferably, the one or more acids are
selected from the group consisting of sulfuric acid, sulfamic acid
and methane sulfonic acid, more preferably, the one or more acids
are selected from the group consisting of sulfuric acid and
sulfamic acid, most preferably, the acid is sulfamic acid.
[0020] One or more of the foregoing acids or salts thereof are
included in the indium electroplating compositions of the present
invention in amounts of 10 g/L or greater. Preferably, the one or
more acids are included in the indium plating compositions in
amounts of 10 g/L to 300 g/L, more preferably, from 50 g/L to 250
g/L, even more preferably from 50 g/L to 200 g/L, most preferably
from 50 g/L to 100 g/L.
[0021] The pH of the aqueous acid indium electroplating
compositions of the present invention range from 5 or less,
preferably from 1-4, more preferably, from 1-3, even more
preferably, from 1.5-3, most preferably, from 1.5-2.5.
[0022] Optionally, one or more pH adjusters can be included in the
indium electroplating compositions to provide and maintain a
desired acid pH. The pH adjuster can include buffers which include
an acid and the salt of its conjugate base. Acids are selected from
glyoxylic acid, pyruivic acid, hydroxamic acid, iminodiacetic acid,
salicylic acid, succinic acid, hydroxybutyric acid, acetic acid,
acetoacetic acid, tartaric acid, phosphoric acid, oxalic acid,
carbonic acid, ascorbic acid, butanoic acid, thioacetic acid,
glycolic acid, malic acid, formic acid, heptanoic acid, hexanoic
acid, hydrofluoric acid, lactic acid, nitrous acid, octanoic acid,
pentanoic acid, uric acid, nonanoic acid, decanoic acid, sulfurous
acid, sulfuric acid, alkane sulfonic acids and aryl sulfonic acids
such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic
acid, toluenesulfonic acid, sulfamic acid. Bases such as potassium
hydroxide and sodium hydroxide can also be used as pH adjusters
alone or combination with one or more of the foregoing acids.
Preferably, the one or more pH adjustors are selected from the
group consisting of sulfamic acid, sulfuric acid, potassium
hydroxide and sodium hydroxide, more preferably, the one or more pH
adjusters are selected from the group consisting of sulfamic acid,
sulfuric acid and potassium hydroxide.
[0023] Optionally, the aqueous acid indium electroplating
compositions can include one or more alloying metal. Preferably,
the one or more alloying metal is selected from the group
consisting of tin, copper, bismuth and silver, more preferably, the
one or more alloying metal is selected from the group consisting of
tin, copper and silver, most preferably, the alloying metal is tin.
The alloying metals can be added to the indium compositions as
water soluble metal salts. Such water-soluble metal salts are well
known to those of skill in the art. Many are commercially available
or can be prepared from descriptions in the literature. One or more
sources of alloying metal can be added to the indium electroplating
compositions in amounts such that the indium alloy has from 1 wt %
to 3 wt % of one or more alloying metals. Preferably, alloying
metals are excluded from the indium compositions. It is preferred
that only indium metal is plated.
[0024] Optionally, one or more sources of chloride can be added to
the indium electroplating compositions of the present invention.
Sources of chloride include, but are not limited to, sodium
chloride and potassium chloride. Preferably, when one or more
sources of chloride is added to the indium electroplating
composition, the concentration of chloride can range from 1-50
g/L.
[0025] Conventional hydrogen gas suppressors, such as copolymers of
epihalohydrin and nitrogen-containing organic compounds, are
excluded from the indium electroplating compositions of the present
invention. Preferably, many conventional additives, such as
levelers, suppressors, brighteners, grain refiners, alloying metals
and surfactants are also excluded of the indium electroplating
compositions of the present invention.
[0026] Preferably, in the aqueous acid indium electroplating
compositions of the present invention, the water is at least one of
deionized and distilled water to limit incidental impurities.
[0027] Preferably, the aqueous acid indium electroplating
composition of the present invention consists of water; one or more
sources of indium ions, including both indium (In.sup.3+) cations
and counter anions; one or more acids selected from the group
consisting of inorganic acids, wherein the inorganic acids are
selected from the group consisting of sulfamic acid and sulfuric
acid, and alkane sulfonic acids, including salts of sulfamic acid,
sulfuric acid and alkanesulfonic acid; one or more amino acids
selected from the group consisting of alanine, arginine, aspartic
acid, asparagine, glycine, glutamine, histidine, leucine, lysine,
threonine, isoleucine, serine, and valine; optionally one or more
sources of chloride; and optionally one or more pH adjusters.
[0028] More preferably, the aqueous acid indium electroplating
composition of the present invention consists of water; one or more
sources of indium ions, including both indium (In.sup.3+) cations
and counter anions; one or more acids selected from the group
consisting of sulfamic acid, sulfuric acid, methane sulfonic acid
and salts of the foregoing acids; one or more amino acids selected
from the group consisting of arginine, aspartic acid, asparagine,
glycine, glutamine, lysine and serine; one or more sources of
chloride; and optionally one or more pH adjusters.
[0029] Most preferably, the aqueous acid indium electroplating
composition of the present invention consists of water; one or more
sources of indium ions, including both indium (In.sup.3+) cations
and counter anions; one or more acids selected from the group
consisting of sulfamic acid and sulfuric acid, wherein the most
preferred acid is sulfamic acid; one or more amino acids selected
from the group consisting of arginine, asparagine, glycine, lysine
and serine, wherein glycine, lysine and serine are the more
preferred amino acids, and glycine is the most preferred; and
optionally one or more pH adjusters.
[0030] Preferably, the aqueous acid indium electroplating
composition of the present invention can be used to electroplate
indium metal or an indium alloy directly adjacent to a nickel
layer, wherein the nickel layer is directly adjacent to copper or a
copper alloy. More preferably, the aqueous acid indium
electroplating composition of the present invention can be used to
electroplate indium metal directly adjacent to a nickel layer,
wherein the nickel layer is directly adjacent copper or a copper
alloy. Nickel layer thickness preferably ranges from 0.1-5 .mu.m.
Conventional strike layers of indium or silver having thickness
values ranging from 1-100 nm, more typically, from 1-40 nm are
excluded from the nickel surface such that the indium metal or
indium alloy can be electroplated directly adjacent the nickel and
provide a matte, uniform, void-free and substantially whisker-free
indium deposit of >100 nm which has good adhesion to the nickel.
Such adhesion can be tested by cross-hatch tests, pin bending tests
and reflow test followed by dewetting control.
[0031] The indium layers range in thickness from >0.1 .mu.m,
preferably, from 0.2 .mu.m to 10 .mu.m, more preferably, from 0.2
.mu.m to 5 .mu.m, most preferably, from 0.2 .mu.m to 1 .mu.m.
[0032] Apparatus used to deposit indium metal or indium alloys
directly adjacent to nickel is conventional. Preferably,
conventional soluble indium electrodes are used as the anode.
Current densities can vary depending on the concentration of indium
ions in the electroplating composition and bath agitation.
Preferably, current densities range from 0.1 ASD or greater (e.g.
0.1-50 ASD, 0.1-30 ASD or 0.1-20 ASD), more preferably, 0.5 ASD to
50 ASD (e.g. 0.5-40 ASD, 1-20 ASD or 1-10 ASD).
[0033] The temperatures of the indium compositions during indium
metal or indium alloy electroplating can range from room
temperature to 60.degree. C. Preferably, the temperatures range
from room temperature to 55.degree. C., more preferably, from room
temperature to 50.degree. C., most preferably, from 30-45.degree.
C.
[0034] The indium plating speed of the aqueous acid indium
electroplating compositions of the present invention can range from
.gtoreq.0.2 .mu.m/min., .gtoreq.0.5 .mu.m/min., >1
.mu.m/min.,>2.3 .mu.m/min., or >3 .mu.m/min., at 1, 2, 4, 8
or 10 ASD, respectively.
[0035] Optionally, the indium or indium alloy plated nickel and
copper or copper alloy substrates are reflowed. Reflow tests are
preferably done at temperatures of .gtoreq.150.degree. C., more
preferably, at temperatures of .gtoreq.200.degree. C., most
preferably, from 200-350.degree. C. Reflow can be done in
conventional reflow ovens used for metal substrates. The reflowed
indium plated nickel substrates show minor to substantially no
dewetting.
[0036] Although the aqueous acid indium electroplating compositions
of the present invention are preferably used to deposit indium
metal or indium alloy directly adjacent a nickel layer, wherein the
nickel layer is directly adjacent copper or copper alloy, such as
for connector pins in IC electronic devices, it is envisioned that
the aqueous acid indium electroplating compositions of the present
invention can be used to deposit indium metal or indium alloys
directly adjacent other metals, such as copper and copper alloys.
It is preferred that indium metal is deposited directly adjacent
other metals, such as nickel, copper or copper alloys, most
preferably, indium metal is deposited directly adjacent nickel,
wherein the nickel is directly adjacent copper or copper alloy.
[0037] The following examples are intended to illustrate the
present invention, but are not intended to limit the inventions
scope.
Examples 1-10
Hull Cell Electroplating Performance of Aqueous Acid Indium
Electroplating Compositions of the Present Invention
[0038] The following aqueous, acid indium electroplating
compositions were prepared:
TABLE-US-00001 TABLE 1 Plating Ex- Indium Ion Amino Temperature
ample Concentration Acid Acid pH .degree. C. 1 30 g/L Indium
Glycine Sulfamic 2.1 30 ions (from 100 g/L acid indium sulfate) 50
g/L 2 30 g/L Indium Glycine Sulfamic 1.1 50 ions (from 50 g/L acid
indium sulfate) 100 g/L 3 30 g/L Indium Glycine Sulfamic 2 50 ions
(from 50 g/L acid indium sulfate) 100 g/L 4 30 g/L Indium Glycine
Sulfuric 2.4 40 ions (from 100 g/L + acid indium sulfate) Arginine
28 g/L 40 g/L 5 30 g/L Indium Glycine Methane 2.2 30 ions (from 120
g/L Sulfonic indium sulfate) acid 160 g/L 6 30 g/L Indium Lysine
Sulfamic 2.1 35 ions (from 100 g/L acid indium sulfate) 50 g/L 7 30
g/L Indium Glutamine Sulfamic 2.1 40 ions (from 100 g/L acid indium
sulfate) 50 g/L 8 30 g/L Indium Histidine Sulfamic 2.1 35 ions
(from 100 g/L acid 50 g/L indium sulfate) 9 30 g/L Indium Serine
Sulfamic 2.1 35 ions (from 100 g/L acid indium sulfate) 50 g/L 10
30 g/L Indium Asparagine Sulfamic 2.1 35 ions (from 100 g/L acid
indium sulfate) 50 g/L
The solvent of the foregoing indium electroplating compositions was
water and the pH of the indium electroplating compositions was
adjusted with potassium hydroxide.
[0039] 250 mL of each indium composition was placed in separate
Hull cells. A brass (copper-zinc alloy) panel coated with nickel
was used as the cathode. Indium metal was used as a soluble anode.
The rectifier was set as 2 A. During plating, the indium
compositions were agitated using a common laboratory paddle
agitator. Indium electroplating was done for 3 min. Current
densities ranged from 0.1-10 ASD. The indium metal deposit was
measured at current densities of 1, 2, 3, 4, 6, 8 and 10 ASD using
a Fischerscope X-Ray XDV-SD XRF apparatus. The plating rate was
determined by dividing the thickness at each current density by the
plating time in minutes.
[0040] As the current density increased, the plating rate of the
indium deposition on the nickel also increased. Plating rates
ranged from a low of 0.5 .mu.m/min. at 1 ASD to a high of 3.2
.mu.m/min. at 10 ASD. After electroplating was completed, the
indium deposits were examined for the quality of the deposits. All
the indium deposits appeared smooth, matte and uniform. No deposit
defects were observed.
Examples 11-12
Reflow Test of Indium Metal on Nickel
[0041] The following aqueous, acid indium electroplating
compositions were prepared:
TABLE-US-00002 TABLE 2 Plating Indium Ion Amino Temperature Example
Concentration Acid Copolymer Acid pH .degree. C. 11 30 g/L Indium
Glycine -- Sulfamic 2.1 30 ions (from 100 g/L acid indium sulfate
50 g/L 12 30 g/L Indium -- Imidazole- Methane 1.1 50 (comparative)
(from indium epichlorohydrin.sup.1 sulfonic sulfate) 130 g/L acid
4.4 g/L .sup.1LUGALVAN .TM. IZE, available from BASF (IZE contains
48-50 wt % copolymer).
[0042] Each aqueous, acid indium electroplating composition was
used to plate indium on nickel coated brass (copper-zinc alloy).
The counter electrode was an indium soluble anode. Plating of
indium on the nickel of the substrate was done for 3 min. at a
current density of 5 ASD. The indium electroplating compositions
were agitated throughout plating.
[0043] After plating, the indium plated substrates were rinsed with
DI water, dried and observed for plating performance. The indium
deposit on the nickel appeared uniform, matte and smooth on both
substrates.
[0044] The substrates were then reflowed/heated using a
conventional reflow oven. Reflow was done at 200.degree. C. for 3
min. The reflowed substrates were removed from the oven and the
quality of their surfaces was analyzed. The substrate which was
plated with the indium composition of Example 11 showed no
indication of dewetting. In contrast, the substrate plated with the
indium composition of Example 12 showed significant dewetting:
nickel was exposed on some areas which were covered by the indium
before reflow.
Examples 13-14
Hull Cell Plating Performance of Aqueous Acid Indium Plating
Compositions Containing Amino Acid Cysteine or Amino Acid
Glycine
[0045] The following aqueous acid indium electroplating
compositions were prepared:
TABLE-US-00003 TABLE 3 Plating Indium Ion Amino Temperature Example
Concentration Acid Acid pH .degree. C. 13 30 g/L Indium L-cysteine
Sulfamic 2 35 (compar- ions (from 100 g/L Acid ative) indium
sulfate) (sufficient amount to provide desired pH) 14 30 g/L Indium
Glycine Sulfamic 2 35 ions (from 100 g/L Acid indium sulfate)
(sufficient amount to provide desired pH)
[0046] 250 mL of each aqueous acid indium composition was placed in
a Hull cell. A nickel coated brass (copper-zinc alloy) substrate
was used as a cathode. The plating was done at a current of 2 A for
3 min. under paddle agitation. The counter electrode was a soluble
indium anode. The coating appearance and thickness were evaluated
at the current density ranging from 0.1-10 ASD. For comparative
Example 13 there was no indication of indium plating as the lower
current densities of 0.1-3 ASD. The indium deposit was very thin
(less than 0.4 .mu.m) and non-uniform at current densities above 3
ASD. Substantial gas evolution was observed during plating
(observed by gas bubbling from the cathode with the naked eye).
[0047] In contrast, the indium deposit of Example 14 appeared
uniform, matte and smooth from 0.1-10 ASD. The plating speed was
comparable to the plating speeds of Examples 1-5, above.
Examples 15-17
Hull Cell Plating Performance of Aqueous Acid Indium Plating
Compositions
[0048] The following aqueous acid indium electroplating
compositions were prepared:
TABLE-US-00004 TABLE 4 Plating Indium Ion Amino Temperature Example
Concentration Acid Copolymer Acid pH .degree. C. 15 30 g/L Indium
Glycine -- Sulfamic 2 35 ions (from 100 g/L acid indium sulfate) 50
g/L 16 30 g/L Indium Glycine Imidazole- Sulfamic 2 35 (comparative)
ions (from 100 g/L epichlorohydrin.sup.1 acid indium sulfate) 5 g/L
50 g/L 17 30 g/L Indium Glycine Imidazole- Sulfamic 2 35
(comparative) ions (from 100 g/L epichlorohydrin.sup.1 acid indium
sulfate) 15 g/L 50 g/L .sup.1LUGALVAN .TM. IZE, available from BASF
(IZE contains 48-50 wt % copolymer).
[0049] 250 mL of each aqueous acid indium composition was placed in
a Hull cell. A nickel coated brass (copper-zinc alloy) substrate
was used as a cathode. The plating was done at a current of 2 A.
Plating was done under paddle agitation for 3 min. The counter
electrode was an indium soluble anode. The indium coating
appearances and thicknesses were evaluated at current densities
ranging from 0.1-10 ASD.
[0050] The substrate plated with indium from Example 15 had a
uniform, matte and smooth indium deposit. The plating rate was good
and was substantially the same as in Examples 1-5 above over the
current density range of 0.1-10 ASD. There were no observable
defects.
[0051] In contrast, the substrates plated with the indium
compositions of Examples 16-17 showed no substantial indium
deposited on the substrate. XRF analysis of the substrates from
Examples 16-17 showed 0.1-0.6 .mu.m indium clusters at some areas
of the substrates. Substantial gas evolution was observed during
the plating of the substrates of Examples 16-17. It was determined
that the imidazole/epihalohydrin copolymer was not suitable for
indium metal electroplating.
Example 18
Hydrogen Gas Generation and Reflow Test of Indium on Nickel
[0052] The indium plating compositions of Examples 15, 16 and 17 of
Table 4 above were added to separate one liter glass beakers. Two
indium soluble anodes were placed in each beaker. A nickel coated
brass coupon was used in each beaker as a cathode. The electrodes
were connected to a rectifier. A current density of 4 ASD was
applied to each composition. Plating was done over 2 min. The
indium electroplating compositions were agitated using a magnetic
stirrer throughout plating. After plating, each coupon was removed
from the beaker and rinsed with DI water, dried and analyzed for
indium plating performance.
[0053] The coupon from Example 15 had a uniform, matte and smooth
indium deposit 2.2 .mu.m thick. In contrast, the indium deposits
from the plating compositions of Examples 16-17 were very thin. XRF
analysis measured an indium deposit of only 0.2 .mu.m thick for the
coupon plated with the indium composition from Example 16 and an
indium deposit of 0.1 .mu.m thick from the composition of Example
17. Substantial gas evolution was observed during plating for
Examples 16-17.
[0054] The above experiment was repeated using a current density of
8 ASD with a plating time of 1 min. 30 sec. The indium deposit from
Example 15 was uniform, matte and smooth in appearance with a 3.7
.mu.m thick indium deposit. The indium deposit from the
compositions of Examples 16-17 had indium thicknesses of 0.55 .mu.m
and 0.35 .mu.m, respectively.
Examples 19-21
Hydrogen Gas Generation and Reflow Test of Indium on Nickel
[0055] The following aqueous acid indium electroplating
compositions were prepared:
TABLE-US-00005 TABLE 5 Plating Indium Ion Amino Temperature Example
Concentration Acid Copolymer Acid pH .degree. C. 19 30 g/L Indium
Glycine -- Sulfamic 2 35 ions (from 100 g/L acid indium sulfate) 50
g/L 20 30 g/L Indium Glycine Imidazole- Sulfamic 2 35 (comparative)
ions (from 100 g/L epichlorohydrin.sup.1 acid indium sulfate) 5 g/L
50 g/L 21 30 g/L Indium Glycine Imidazole- Sulfamic 2 35
(comparative) ions (indium 100 g/L epichlorohydrin.sup.1 acid
sulfate) 15 g/L 50 g/L .sup.1LUGALVAN .TM. IZE, available from BASF
(IZE contains 48-50 wt % copolymer).
[0056] Each of the indium plating compositions of Examples 19-20
were added to separate glass one liter beakers. Two indium anodes
were placed in each beaker and a nickel coated coupon was used in
each beaker as a cathode. The electrodes were connected to a
rectifier. A current density of 4 ASD was applied for 2 min. of
plating. The plating compositions were agitated throughout plating.
During indium plating substantial hydrogen gas evolution was
observed for Examples 20-21. In contrast, insignificant hydrogen
gas evolution was observed for Example 19.
[0057] After plating, the indium plated substrates were rinsed with
DI water, dried and observed for plating performance. The indium
deposit on the nickel plated from the indium compositions of
Example 19 appeared uniform, matte and smooth. The average indium
thickness was 2.2 .mu.m.
[0058] In contrast, substantially no indium was deposited on the
nickel from the indium compositions of Examples 20 and 21. The
average indium thickness on the nickel plated with the indium
composition of Example 20 was only 0.55 .mu.m and the average
thickness on the nickel plated with indium with the composition of
Example 21 was only 0.35 .mu.m.
[0059] The substrates with the indium deposits adjacent the nickel
were then reflowed using a conventional reflow oven. Reflow was
done at 200.degree. C. for 3 min. The reflowed substrates were
removed from the oven and the quality of their surfaces was
analyzed. The substrate which was plated with the indium
composition of Example 19 showed no indication of dewetting. In
contrast, the substrates plated with the indium compositions of
Examples 20-21 showed several dewetting spots spread over the
surface of the indium layer.
Examples 22-27
Aqueous Acid Indium Electroplating Composition Stability
[0060] The following aqueous acid indium electroplating
compositions were prepared:
TABLE-US-00006 TABLE 6 Indium Ion Amino pH Example Concentration
Acid Acid pH Adjuster 22 30 g/L Indium -- Sulfamic 2 Potassium
(comparative) ions (from acid hydroxide indium sulfate) 50 g/L 23
30 g/L Indium Glycine Sulfamic 2 Potassium ions (from 25 g/L acid
hydroxide indium sulfate) 50 g/L 24 30 g/L Indium Glycine Sulfamic
2 Potassium ions (from 50 g/L acid hydroxide indium sulfate) 50 g/L
25 30 g/L Indium Glycine Sulfamic 2 Potassium ions (from 75 g/L
acid hydroxide indium sulfate) 50 g/L 26 30 g/L Indium Glycine
Sulfamic 2 Sulfamic ions (from 100 g/L acid acid indium sulfate) 50
g/L 27 30 g/L Indium Glycine Sulfamic 2 Sulfuric ions (from 150 g/L
acid acid indium sulfate) 50 g/L
[0061] After initial make-up at room temperature, all the foregoing
indium plating compositions appeared colorless. All the indium
plating compositions idled at room temperature for one day. The
indium plating composition of Example 22 was significantly turbid.
White precipitate was observed at the bottom of the glass beaker.
The white precipitate indicated that an indium salt precipitated
from the composition.
[0062] In contrast, the indium plating compositions of Examples
23-27 remained colorless indicating good stability. The
compositions of Examples 23-27 remained colorless indicating stable
indium compositions over several weeks. No turbidity or
precipitation was observed even after one month.
* * * * *