Note: Descriptions are shown in the official language in which they were submitted.
3 0 ~
SPECIFICATI~:)N
Background and Description of the Invention
The present invention generally relates to the
treatment of metal substrates so as to render them catalytic
to subsequent eleciroless aeposition of metals thereonto,
and is especially well suited to the electroless deposition
of nickel, cobalt, or polyallovs containing nickel and/or
cobalt onto copper that had previously been plated onto a non-
conductive substrate in an electronic circuitry pattern. In
an important embodiment o~ this invention, printed wiring
boards are prepared which are less likely to develop electrical
short circuiting problems than plates prepared without the
use of these catalytic solutions.
Copper-plated circuits tend to oxidize, making it
highly desirable to overplate the copper with a more durable
metal to thereby enhance the circuitsl corrosion resistance,
abrasion resistance, and solderability or bondability to
aluminum or gold wire by ultrasonic means or the like, while
at the same time maintaining or enhancing adequate conductivity.
Early procedures for providing overplatings included Plectro
plating techniques which require electrically connecting each
indiviaual circuit of the printed wiring board to a current
source T~hile electroless overplating does not require such
inefficient handling techniques, and avoids other drawbacks
of electroplating such as non-unirorrnity of coating at board
locations relatively re~note from the power source and exposed
copper at the elec~rode connection sites, it has been found
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that such electroless overpl~tirlgs do not readily adhere
to copper or copper alloys.
When electrolessly overplating the copper circuitry
of a printed wiring board or a printed circuit board with a
nickel-phosphorus or nickel-boron deposit, general im-
provement has been found to be attained by dipping copper
clad boards into a bath of an activator without rinsing in
order to coat the copper clad board with a slightly alkaline
film prior to nickel overplating in a slightly acidic electro-
less nickel bath. Activators known to be useful in this
regard include a bath having dimethylamine borane to activate
reduction of nickel onto the copper. A serious drawback of
this procedure is that it activates the entire board including
the insulating portions thereof to also activate the reduction
of nickel onto portions of the board that are not in the
circuitry pattern for carrying current, which leads to short
circuiting or bridging, especially when the insulating portions
have metal specks therein which serve as sites for plating
initiation and bridging between specks and between specks and
portions of the circuitry.
It is believed that one important reason for the un-
desirable plating in the non-circuitry portions is the fact
that it is not possible to rinse the plate after treatment
with such activators primarily because such a rinsin~ step
would simply remove essentially all of the activator before
it has had a chance to enhance the subsequent electroless step.
Copper specks are often embedded into the surface of the
board and they typically can not be seen by the human eye.
Specks that remain on the board at the time it is over-
plated with nickel or the like serve as sites for electroless
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~93~4
metal deposition at locations that are not within the
circuitry pattern and which can eventually lead to short
circuiting of the circuitry.
Another approach that has been taken in attempting
to improve the electroless overplating of nickel or the like
onto copper clad boards includes the use of baths having
matPrials, known generally as catalyzing agents, which
operate to make the copper surface more receptive to the
electroless deposition o~ metals thereover~ A known
catalyzing agent is a palladium chloride dip which, although
it effectively catalyzes the copper, has been found that
adhesion between the copper and the subsequently
electrolessly deposited metal is tenuous; and, as a result,
when circuits made in this manner are subjected to rugged
mechanical handling, or heat shock such as that developed
during dip soldering, there is a tendency for the conductive
layer to crack or pop free of the non-conductive base,
thereby diarupting the circuit. Discussions relative to
catalyzing agents are ~ound in Schneble et al U.S~ Patent
No. 3,226,256 and Weisenberger U.S. Patent No. 3,431,120
It has now been discovered that certain
formulation~ perform quite effectively as catalyzing agen~æ
in order to enhance the adhesion of nickel 9 cobalt, or
polyalloys of nickel and/or cobalt over copper`surfaces,
especially those copper surfaces found on printed wiring
; boards for use in preparing printed circuitry, while at the
same time permitting a procedure whereby these catalyzing
agents in conjunction with a rinse will enhance
verdeposition only upon the metal carrying components of
the circuit board to the exclusion of other metal imbedded
in ~he board.
These results are achieved in accordance with the
prese,nt invention basically by employing catalyzing formulations
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that include nickel or cobalt and a source of a secondary,
inhibitor-type of metal such as tin, molybdenum, copper or
tungsten, together with a reducing agent. Such catalyzing
formulat1ons can be applied to a copper surface
and rinsed to form a catalytic film for enhancing electro-
less overplating in a bath that deposits nickel or cobalt,
either alone or in combination with other metals, onto the
circuitry pattern but discourages overplating onto portions
of the board not within the circuitry pattern.
Accordingly, an object of this invention is to pro-
vide a formulation and a method for improving electroless
plating and products produced in accordance therewith.
Another object of the present invention is to pro-
vide a formulation, method, and product having improved
adhesion of an electrolessly deposited metal over copper,
copper alloys, or the like.
Another object of this invention is to provide an
improved catalyzing agent, its method of use, and products
produced therewith.
Ano-ther object of the present invention is to provide
an improved catalyzing agent, method, and product which exhibi-t
enhanced adhesion and simultaneously allow for rinsing just
prior to electroless overplating for reducing the tendency
to bridge or short circuit.
Another object of the present invention is an im-
proved method for providing a catalytic surface onto platea
copper, which surFace can be subsequently treated by electro-
less deposi-tion of nickel, cobalt, and/or polyalloys includ-
ing either.
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~930~
Another object of this invention is to pro~id~ an
improved catalyzing agent which includes nickel or cobalt
and tin, molybdenum, copper or -tungsten together with a
reducing agent, which catalyzing agent is suitable for in-
corporation into a bath.
These and othex objects of the present invention will be
apparent from the following detailed description, taken in
conjunction with the accompanying drawings wherein:
The Figure is a generally schematic view depicting
a production flow in accordance with this invention and
products at various stages of production.
Catalyzing agents in accordance with this invention
are, in general, polymetallic formulations of deposition-
enhancing nickel and/or cobalt metal, and of secondary or
inhibitor-type metals such as tin, molybaenum, copper and
tungsten. As such, these catalyzing agents are related to
the electroless polyalloy plating-formulations shown in Malloxy
U.S. Patent No. 4,019,910. Typically, the formulations will
be put to use within an aqueous bath which also includes a
reducing agent for electrole~ss baths.
Any of these metals can be added as soluble salts,
salts of low solubility within the particular electroless
bath system in which they are intended to be used, esters, or
substantially any other source suitable for electroless systems.
In an important aspect of this invention/ boron is added to
the system as a third metal by means of a boron-containing
reducing agent.
Suitable salts of nickel or cobalt include sulfates,
chlorides, sulfamates or other anions compatible with these
electroless systems. These same anions usually pro~ide an
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acceptable source of sal-ts of the secondary metals, inclllding
for example stannous chloride, stannous fluorobora-te, sodium
stannate, cuprous chloride, cuprous sulfate, and cupric salts,
although it is preferred that these secondary metals be
provided in the form o~ ester complexes of polyhydric compounds
which are prepared hy conventional techniques involving reaction
between an oxyacid and a pol~hydric acid or alcohol. The oxyacids
are generally inorganic acids of the particular metal cation,
for example, the tungstic, molybdic or boric acids. Representative
O of the polyhydric acids or alcohols which may be employed
are carboxylic acids or alcohols which contain at least two
hydroxy groups and from about four to about fifteen carbon
atoms per molecule. Typical polyhydric compou~ds include acids
such as tartaric, gluconic, or glucoheptonlc acid, or alcohols
such as mannitol, 2,3-butanediol or 1,2,3-propanetriol. Of
these various polyhydric compounds, the carboxylic acids are
generally preferred, and a particularly suitable one is gluco-
heptonic acid. The ester complexes may also be, and in certain
instances preferrably are, in the form o~ a polyester, that is
O as ester complex formed by reacting two or more mols of the
oxyacid with one mol of the polyhydric compoundl
Ester complexes of these general types are formed
and are generally believed to exist in aqueous solution as
a complex equilibrium mixture where the cation of the oxyacid
forms one or more ester linkages either with two hydroxyl
groups of the polyhydric compound or with one hydroxyl group
and one carboxylic acid group when the polyhydric compound is
an acid, for example glucoheptonic acid. Such an ester complex
has been found to be quite stable when used within baths pre-
pared with the catalyzing formulations.
3~
Catalyzing baths for use in connection with the
catalyzing agent formulations of this invention will usually
include a reducing agent for the cations in the bath. While
reducing agents such as hydrazine may be used, it has been
found to be most advantageous if the reducing agent is a
boron compound whereby boron cations are provided to the
system and assist in forming the catalyzing film, together
with the nickel or cobalt and the secondary metal~ Various
boron-containing compounds can be used;theY are preferably any
of those employed as reducing agents in electroless nickel
or cobalt plating baths. Typical examples include boron
hydrides, amine boranes or lower alkyl substituted amine
boranes such as dimethyl-or diethyl-amine horane. Generally,
of the various boron compounds which may be employed, the
alkylamine boranes are preferred, particularly dimethylamine
borane.
In general, when these various a~ents are combined
with water and formulated into a catalyzing bath, -the total
bath will usually be alkaline although slightly acidic baths
can be put to ractice, a typical pH range being between 5.5
and 13, preferably between about 8 and about 11. Operating
temperatures are between room temperature and the boiling
temperature of the bath, a typical temperature range being
between about 20 and 100C. These baths are, in ~eneral,
capable of operating as electroless polyalloy plating baths;
their catalyzing function is achieved in part by using
relatively low concentrations of active ingred;ents and by
limiting the time period during which the article being sub-
jected to the catalyzing agent remains within the bath. Very
~ :l6~3~
generally, active ingredient concen~rations about one-tcnth
those of plating baths can be ~ormulated. The time period is
such that the catalytic agent will form a coatiny to the extent
that the surface is ~Inuc1eated~ typically with a tertiary
polyalloy; in order to provide a film that is not necessarily
observable to the ~naided eye but which will perform as catalyzing
agent even after rinsing a substrate that had been immersed
in the bath. Generally, catalyzing bath immersion will continue
for between about 10 to 9~ seconds, usually no more than 60
seconds, at approximately 0.1 mil/hour, the most appropriate
time and rate depending upon the particular catalyzing system
being used, the temperature of the bath, the pH of the bath,
and the precise make-up of the material being overplated.
Plating baths prepared with formulations according to
this invention may, if desired, contain conventional bath
additives which are commonly employed in electroless plating
baths. Included are bath stabilizers such as sulfur contain-
ing compounds, for example thiourea, as well as pH regulators
such as an acid or a base, complexing agents for the metal
~0 ions maintained within the bath, such as ethylene diamine
tetracetic acid, potassium pyrophospha-te or polyamines, or
sulfide ion controllers such as lead. Buffering agents can
also be added to add to the pH stability of the bath.
In proceeding with the ~ethod according to this in-
vention, a metal substrate that is not normally receptive to
electroless nickel or cobalt plating baths is rendered
catalytic whereby nickel or cobalt can be electrolessly de-
posited thereover. Not only does the method include catalyz-
ing a surface and improving adhesion between the nickel or
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cobalt and the overcoated metal, but also it allows for
rinsing after application of the catalytic coating in order
to enhance the quality of produets produced thereby.
As an aid for illustrating this invention, reference
is made to the ~igure, which generally depicts the catalyzing
and overplating of a copper clad board, generally designated
11, that had been prepared by conventional plating techniques
to plate about 1/4 ounce of copper per square foot of plating
area. These conventional plating techniques prepare a copper
elad board by a process which ineludes removing copper from
a plate 12 at those locations that are not within a eircuitry
pattern 13, which, in general tends to leave copper specks or
partieles 14 lying on the surface of plate 12 and often em-
bedded into that surface.
Typical conventional techniques (not depicted) ean
inelude adhering copper to the plate, for example an expoxy
fiberglass plate, at whieh stage procedures sueh as
drilling holes 15 can be proceeded with, and this ean be
followed by laying down a resist and plating copper onto the
board. The copper plating can be entirely electroless, but
the length of time needed to plate a suitable thickness is
shortened if an electroless co per deposition is followed by
an electrodeposition of copper. Then, by etchingl lifting-
off, or the like, the copper that had been plated onto the
non-circuitry portions of the plate 12 is removed in order to
leave an isolated eircuitry pattern to form the copper elad
board 11.
Conventional further treatment that is not depicted -
can include cleaning the copper clad board in a mildly
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alkaline detergent bath Eor on the or~er of about five minutes
at an elevated temperature that will not damage surfactants
in the bath. After rinsing with water to remove residual
carry-over, the plates are oEten either mechanically scrubbed
or are dipped in an etching agent such as ammonium persulfate
at a concentration of about 1 pound per gallon in order to
etch off surface oxides and render the copper more active for
subsequent deposition, which step would typically be followed
by rinsing with tap water or the like. Next, a copper clad
plate would usually be acid dipped as insurance that any
residual surface materials are removed and in order to re-
activate the copper. A mineral acid bath, such as 10% sulfuric
acid, or a dry acid salt such as sodium bisulfate salts can
be used, followed by rinsing for about one minute with, for
example, deionized water. Even if every one of these further
treatments are conducted on the copper clad board 11, the
residual specks or particles of copper remain on the plate
portion 12 off of the circui-try pattern 13~
Copper clad b~ard 11 is treated with the catalyzing
agent in accordance with -this invention, with the general
objective of forming a catalyzing film thereon to, generally
~peaking, nucleate the copper surface with what may be in the
nature of a monomolecular layer. Typically, this treating
step will include immersing the board ll into a bath 16 having
the catalyzing agent according to this invention. This
treating step should not be of such a length that electroless
plating actually occurs, but should be of a duration adequate
to provide a catalytic coa-ting of the board as shown at 17.
When the bath immersion technique is used, a typical suitable
time period will be between about lO and 60 seconas, the exact
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time that is most sui~able depending upon the particular
catalyzing systems being used, the temperature of the bath,
the pH of the bath, the reducing agent used, and the make-up
of the copper clad board.
The catalyzing treatment time is also dependent
somewhat upon the temperature o the bath in which the
catalyzing agent is used, with typical temperature ranges
being between about 20C. to substantially boiling, or
about 100C., preferred temperature ranges therewithin
varying somewhat depending upon the particular reducing
agent included within the bath.
After treatment with the catalyzing agent, the
board 17 is subjected to a rinsing step, illustrated in the
Figure by spray nozzle 18, although any means or method for
rinsing may be used, such as running through a water bath
for a very short period of time. This rinsing step will not
significantly affect the catalytic surface formed by the
catalyzing agent at the circuitry pattern 13 or the
particles or specks of metal 14, but the rinsing step does
wash away all of the plating solu~ion, especially that on
the insulator board 12, which is not nucleated or catalyzed,
on~y the metal portions having been nucleated. It is possi-
ble to then pass the rinsPd board 17 into subsequent baths,
- even those having hypophosphite, which is not possible when
activator solutions such as dimethylamine borane are used
instead of cataly~ing agents of this invention.
It has been found that the catalyzing agents, when
used according to the method of this invention, can be
combined with this subsequent rinsing step in order to
obtain a result that catalyzes plating on the circuitry pattern by
- nucleating, or providing active sites thereon, while at the ~ e
time avoiding enh~ncement of deposition, t~pically discouraging
930~
deposition, at those locations on the surface of the board 12
that are not wi~hin a circuitry pattern 13. ~s a resultr a~ter
the catalyzing agent films are electrolessly plated over with
nickel, cobalt, or polyalloys including either or both, the
electroless overplating is selectively deposited onto only the
nucleated metal and does not spread onto the irlsulator board
by way of forming plated bridges between specks and/or the
circuitry pattern, which undesirable spreading out or extending
is otherwise started at and encouraged by the specks within
a catalyzed board environment provided by other systems. In
this way, a finished printed circuit or wiring board can be made
with precisely overplated circuitry pattern, one that does no~
have substantial excess deposits outside of the pattern which
can and often do lead to short circuiting within the circuitry
pattern and a generally undesirable increase in the conductivity
of the board 12 outside of the pattern.
Rinsing solutions suitable for use in -the rinsing step
will typically be aqueous, and the rinsing step itself should
be long enough to significantly reduce the effect of catalyzlng
agent that had been placed onto the non-circuit portion during
the immersion step. The maximum rinsing time desired will be
determined by convenience and economics in general, there being
a point at which lengthy rinsing times will become expensivev
On the whole, lengthy rinsing will not reduce the extent -that
the surfaces are catalyzed since it is the surfaces themselves
that are transformed rather than a rinsable film being placed
thereon. The catalytic surface will be removed only by etching
off or otherwise removing the copper or the like from the board.
Multiple rinsing can be carried out, and the rinsing can be
in a still bath, under a running ba-th, or tne like. Rinsing
times will vary somewhat depending upon the overa]l make-up
of the plates, the materials, other physical
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conditions, and whether the rinsing solution is running or
still, typical times generally ranging be-tween about 2
seconds and about 45 seconds for each rinse. The pre-Eerred
rinsing times will depend upon the catalyzing agent being
used, the extent to which the catalyzing agent has adhered
to the copper prior to rinsing, and the solventizing ability
of the particular rinsing agent being used. Usually, a
cool water rinsing agent, such as tap water or deionized
water at ar~ient temperature, is preferred primarily because
of the ready availability and low cost of water. If desired,
wetting agents could be added, provided they do not interfere
with the subsequent electroless plating.
Once rinsing in accordance with this invention has
been accomplished, the selective electroless plating step
is ready to be carried out. Catalytic flims formed in ac-
cordance with the preceeding steps are especially receptive
to electroless deposition of nickel plating or cobalt plating
within any number of baths, such as nickel-phosphorous baths,
electroless cobalt plating baths, or pollyalloy type baths,
including ones listed in U.S. Patenk No. 4,019,910. The
rinsed board 17 is electrolessly plated in a conventional
manner, such as within a plating hath 19, whereby an over-
coated layer 20 is added to the copper circuitry pattern 13
in order to form an overcoated circuit board 21, shown in the
Figure emerging from the bath 19, which has subs-tantially no
overplating deposits that are not within the precise circuitry
pattern 13, except for any specks 22 that had been catalyzea
and overplated but not spread out or expanded into a bridging
or short circuiting path, the specks 14 and 22 being illustrated
in exaggerated size for drawing clarity.
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Included within the electroless plating bath 19 can be a
source of nickel cations or cobalt cations, a source of other
metal cations when polyalloy deposition is to be accomplishedt
a pH regulator, a reducing agent, a complexing agent, water, bath
stabilizers, sulfide ion controllers, or other suitable bath
ingredients. Details concerning many of these various ingredients
and the conditions suitable for such baths are discussed in U.S.
Patent No. 4,019,910. ~lso, a typical nickel-phosphorus electro-
less plating bath usually would form a binary coating having be-
10 tween about 88 to 95 weight percent nickel and between about 12
to 5 weight percent phosphorus.
If desired, especially when preparing printed circuit
boards of high quality, it is possible, usually after one or more
rinsing steps, to plate over the overcoating of nickel, cobalt, or
polyalloy with another metal, such as gold, in order to enhance the
solderability and corrosion resistance of the circuit. When final
plating is completed, the substrate formed by this invention, such
; as a printed circuit or wiring boardr will be allowed to dry or will
be dried according to any desired drying procedure.
While there is no desire to be bound by any theory concerning
the operation of this invention, it is believed that the inclusion
of metals generally accepted as being inhibitors, especially in
the case of the molybdenum, tungsten or tin secondary metals,
cooperate with the plating enhancement abilities of the nickel or
cobalt within the catalyzing agent io render catalytic the other-
wise non-catalytic surfaces, especially copper circuitry patterns.
The combination of the nickel or cobalt with the inhibitor-type
secondary metals is believed to bring about the catalyzing properties
attained by this invention by nucleating the otherwise non-catalytic
surface and thus render the surface itself catalytic rather than
merely lay a film over such surface tnat will be washed off during
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a subsequent rinsing step. It is believed that this particular
combination within the system of this invention enhances the
deposition efficiency of the system to the extent that a
catalyzing surface is actually formed ~rom a surface that
previously was non-catalytic. Once such a catalytic surface
is formed, it is possible to electrolessly plate thereover
because the overplating reaction is thereby encouraged, the
catalyzed surface being much more favorable to deposition
thereover than the original non-catalytic surface, especially
when such overdeposition is that ~f a polyalloy. The components
of the system cooperate with each other to efficiently
- utilize the attributes of each to the extent that the system
will successfulIy transform a non-catalytic surface into a
catalyzed one.
As far as the mechanism by which the catalyzing agent
itself renders the circuitry pattern more receptive to over-
plating, it is believed that galvanic initiation plays a part
in instituting the overplating surface. In a general sense,
the catalyzing agent transforms the copper surface to the
extent it is rendered catalytic for the subsequent overplating
step. The ultimate result is a preferential catalyzing of the
copper within the circuitry pattern
It is believed-that the results attributable to the
invention areenhanced by including boron within the sensi-
tizing agent formulation, which inclusion can be most readily
accomplished by using a boron-containing reducing agent~
~ 1693~
It is also possible that p}lysical ~ttri~ es of t~e v~rious
materials involved in the process contribute to this ef~ect.
An in~ersion within the catalyzing agent bath wets all of
the board, but the surface textures of the board within and
out of the circuitry pattern are different, which would in-
dicate that the effects of the subsequent rinsing step on
the mzke-up of the catalyzing agent left on the board will
be different too.
Baths incorporating the catalyzing agents according
to this invention are typically alkal~ It is believed that
operating with pH any lower than about 5.5 can lead to bridg-
ing or plating in bet~een portions of the circuitry pattern,
and a pH that is too high, say above about 13, would be un-
necessarily severe. The preferred pH range is between about
and about 11. The concentration of the deposition-enhancing
metals such as nickel compounas within a bath according to
the invention can be between about 0.001 and about 0.3 mol/literJ
usually between about 0 002 to about 0.125 mol/liter. A
typical ranye for the secondary metals such as the tin com-
pounds within such baths is between about 0.001 to about 0.5
mol/liter, generally between about 0.002 and about 0.250
mol/liter. Reducing agent concentrations such as those for
dimethylamine borane can be between about 0.001 and abol~t 0.2
mol/liter, usually be~ween about 0.002 and 0.1 mol/liter~ The
up~er limits of the various constituents are ~etermined by
economics and solubility, ana the lower limits by minimal
eI~ectiveness.
While the Figure and ihis specification ~eal ~rimarily
~ith the preparation of prinied circuit boards, the invention
is suitable for use whenever it is desired to catalyze a metal
3 0 ~
surface, particularly a copper surface, for subseql~ent
overplating wi~h nickel, cobalt, or ~olyalloys including
same. Eventual end uses for pro~ucts produced accor~ing to
this invention incluae boards for carrying electrical
circuit components within games, watches/ or magnetic memory
devices in computer-type applications. These may bé in the
Iorm of 2-sided printed etched boards which can have plating
through holes therein. The following ex~nples are offered
to illustrate the present invention:
E X k M P L E
Nickel - Molybdenum - Boron
A catalyzing agent immersion bath was prepared to
include 0.01 moi/liter molybdenum ester of gluconic acid,
0.05 mol/liter nickel sulfate, 0.1 mol/liter potassium
pyrophosphate, which is a buffer and complexing agent, and
0 004 mol/liter dimethylamine borane reducing agent. The
operating pH was 9.0, and the operating tem~erature was
40~C. This bath formed an adherent catalytic lilm on copper
alloys that was then overplated with e]ectroless nickel.
Printea circuit boards were prepared an~ exhibited an en-
hance~ adhesion between the copper and its nickel-containing
overcoating. The use of printed circuits thus prepared were
lound to be more consistently iess susceptible to developing
short c;rcuits during use.
E X A M P ~ E 2
- _cXel - Tungsten - Boron
Another catalyzing bath was ~repared and used
generally in accord~nce with Example 1, this catalyzing
agent bath including 0.005 mol/liter tun~sten ester of
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3 0 ~
glucoheptonic acid, 0.02 mol/liter nickel sulfate, 0.05
mol/liter po~asium pyrophosphate, 0.04 mol/liter dimethyl-
amine borane, with the balance of the bath being essentially
water. The bath was operated at a 2H of 9.0, and the
operating temperature was 40C.
E X A M P L E 3
Nickel - Tungsten - Boron
Another bath that had been prepared and is suitable
for use as a catalyzing agent bath includes 0.2 mol/liter of
a tungsten ester of glucoheptonic acid, 0.1 mol/liter of
nickel sulfate, 0.06 mol/liter of dime~hylamine borane and
~ ppm of thiourea. The operating conditions were a pH of
9.6 and a ~temperature of 90C., and the catalytic film pre-
pared thereby should include 77.4 weight percent nickel, 20.0
weight percen-t tungsten, and 2.6 weight percent boron.
E X A M P L E 4
Nickel - Tungsten - Tin - Boron
Another suitable catalytic agent bath includes
deionized, carbon 'reated and filtered water containing 0.2
mol/liter tungsten ester of g}ucoheptonic acid, 0.1 mol/liter
nickel slllfate, 0.025 mol/liter stannous chloride, 0.06
mol/liter dimethylamine borane, and 1 ppm of thiourea, the
operating temperature being 90C an~ the pH being about 7.5.
This bath produces a catalytic film believe~ t~ be analyzable
as 71.9 weight percent nickelr 16.0 weight percent tungsten,
4.2 weight percent tin, and 1.9 weight percent boron
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3 ~ ~
E X A M P L E 5
Nickel - Tin - Boron
A suitable catalytic plating aqueous bath includes
0.1 mol/liter of nickel sulfate, 0.1 mol/liter of stannous
chloride, 0.06 mol/liter of dimethylamine borane, 0.2 mol/liter
of potassium pyrophosphate, 1 ppm of thiourea, and 0.1 mol/liter
of a diboron ester of glucoheptonie acid, which was pre-
pared by charging approximately 2 mols of boric acid and 1
mol of sodium glucoheptonate into an esterification vessel
eontaining about 600 milliliters of water as a solvent,
followed by stirring while maintaining the temperature at
about 25C for 30 mlnutes, after whieh it was diluted to a
final volume of 1 liter with additional water. This bath
produces a eatalytie film whieh has been analyzed in thicker,
plating, operations as 92.8 weight percent nickel, 6.1 weight
percent tin, and 1.1 weight percent boron.
E X A M P L E 6
Nickel - Molybdenum ~ Boron
An aqueous catalyzing agent bath was produced to
include 0.001 mol/liter of a molybdenum ester of glueohep-
tonie acid, 0.1 mol/liter of nickel sulfate, 0.06 mol/liter
: of dimethylamine borane, and 0.3 mol/liter of lactic acid,
the operating pH being 10.0, and the operating temperature
being 90C. This bath produces a catalytic film which has
been analyzed in thicker, plating, operations as 79.8 weight
percent nickel, 20 weight percent molybdenum, and 0.2 weight
. percent boron.
.
~ '.
3 0 4
E X A M P L E 7
Nickel - Mol bdenum - Copper - Boron
y
A catalyzing agent bath was prepared by adding the
following to deionized, carbon treated and filtered water:
0 001 mol/liter of molybdenum ester of glucoheptonic acid,
0.1 mol/liter of nickel sulfate, 0.0005 mol/liter of copper
sulfate, 0.06 mol/liter of dimethylamine borane, and 0.3
mol/liter of lactic acid. The operating temperature was
90C and the operating pH was lQ. This bath has been
analyzed to produce a coating of 77.87 weight percent nickel,
20 ~7eigh percent molybdenum, 1.8 weight percent copper, and
0.33 weight percent boron.
E X A M P L E 8
NicXel - Tin - Boron
A tin-containing catalyzing bath is prepared by
adding to water 0.001 mol/liter of nickel ion, 0.02 mol/liter
of sodium stannate (tetravalent) complex of gluconic ~cid,
and 0.02 mol/liter of dimethylamine borane. A very similar
bath is prepared when 0.002 mol/liter of dimethylamine borane
is included therein.
E X A M P L E 9
Nickel - Tin - Boron
Another useful catalvzing agent bath includes 0.001
mol/liter of the stannate ester of glucoheptonic acid, 0.1
mol/liter of nickel sulfate J 0. 06 mol/liter of dimethylamine
borane, and 0.3 mol/liter of lactic acid, with the operating
temperature being 90~C and the operating pH being 10Ø
-20-
1 il~930~1
E X A M P L E 10
Cobalt~- Tungsten - Boron
A complexing ayent agueous bath for subsequent
cobalt overcoating has 0.2 mol/~ter ofthe tungsten ester of
sluc~heptonic acid, 0.1 mol/liter of cobalt sulfate, 0.06
m~l/liter of dimethylamine borane, ana 1 ppm of thiourea.
The operating pH is about 9.6 at a temperature of about 90C,
coating analysis being about 81 weight percent cobalt, 18
weight percent tungsten and 1 weight percent boron. After
application of a catalyzing film with this bath, subsequent
cobalt overplating can be accomplished by using a similar
bath.
E X A M P L E 11
Cobalt - Molybdenum - Phosphorus
Copper catalyzing bath can be prepared including 0.1
mol/liter of molybdenum ester of yluconic acid, 0.1 mol/liter
o~ cobalt sulfate, and 0.28 mol/liter of sodium hypophosphite.
An operating pH is 10.0, and an operating temperature is 90
the film to be preparea having about 92.9 weiyht percent
cobalt, 1.1 weight percent molybdenum, and 6 weight percent
phosphorus. If aesired, the bath formulation is useful for
coating over this catalytic coating after rinsing with cola
water; typically incluain~ increasing the plating rate to
about 0.2 to 0.3 mil/hour and reaucing the pH to an acidic
level.
E X A M P L E 12
Cohalt - Tin - Boron
An aqueous catalyzing agent bath can be prepared to
include 0.1 mol~liter of robalt sulfate, 0.2 mol/liter of a
sodium stannate complex of gluconic acid/ and 0. a mol/liter of
dimethylamine borane. The operatlng temperature is 60C at
a pH of about 7.
~ 1~93~
E X A M P L E
After any o~ one of the catalyzing ayent baths of
Examples 1 through 9 have been used to prepare a catalytic
film on a copper substrate which remained in the bath for
about 45 seconds, and after that film has been rinsed with
- water twice for 15 second time periods, nickel can be
electrolessly plated thereover using an aqueous bath having
0 1 mol/liter of nickel sulf~te, 0.2 mol/liter of citric
acid and 0.17 mol/liter of sodium hypophosphite The operating
pH is between about 4 5 and 5 0 at a temperature of 90C, and
the plating rate is about 10 microns/minute which usually con-
tinues for about 10 to 20 minutes. The overplating is generally
complete, no bridging or coating over of copper specks on the
board being observable.
E X A M P L E 14
After copper clad substrates are immersed in any of
on~ of the cataiyzing agent baths of Examples 1 through 9
for about 45 seconds~ to prepare a catalytic ilm thereon,
and after that film has been rinsed twicèwith running water,
a nick~l overplating can be electrolessly formed thereover at
about ~0C and a pH of 5 0 using an a~ueous bath having 0.1
mol/liter of nickel sulf~te, 0 25 mol/liter of succinic acid,
and 0 04 mol/liter of dimethyla~ine borane~ This was followed
by two running water rinses and further overplating with an
electroless yold bath at 63C ana at a plating rate of about
1 micron/minute.
While in ~he Ioregoing s~ecification certain embodi-
ments and examples of this inven~ion have been described in
aetail, it will be appreciated that modifications and
variations therefrom will be apparent to those skilled in
this art. Accordingly, this invention is to be limited only
by the scope of the appended claims.
