Note: Descriptions are shown in the official language in which they were submitted.
- 1119150
.
. .
Generally stated, the subject matter of the present
invention relates to new and useful-methods to prepare precious
, metal sensitizing, compositions. ' More p~rticularly, the invention
, selates to the preparation of solid compositions com~rising a
; , precious metal compound. Solutions prepared by dissolving the
novel solids are used to render surfaces of substrates catalytic
,.
to the reception of an electroless metal.
, ' .
, 'Back~round of the Invention - The electroless
i deposition of a metal on either a metallic or non-metallic
,' ' i~ substrate usually requires pretreatment or sensitization of,; , the sub~trate with a precious me~sl composition to render it
catalytic to the reception of such deposit. Variou~ methods
, have evolved over'the years employing partlculsr sensitizin~
compositions. ', ' -
." , . , :, '.' ', ' ' - '
' " , , ' ' '2 , ' ~ ' ' ~ '
.. ..
.: .
', ' ~ '
9~50
1 Unitary bath sensitizers are known, e.g.,
2 Shipley, U.S. 3,011,920, but dry, stable solids, suitable to
3 prepare such baths by dissolution have not been feasible to
4 prepare, ship or store. Applicant herein has developed unitary
bath sensitizers in a dry powder form, see, e.g., U.S.
6 3,672,923, assigned to the present assignee. These dry
7 sensitizers are desirable because shipping and storage costs
8 are minimized and process solutions are very simple to put
9 together (by dissolution, for eY~ample).
. ' ' ;~
11 - The methods for preparing sensitizers in dry solid
12 form known until now are somewhat disadvantageous, however, in
13 that they depend on heating and evaporating relatively large
14 quantities of water, often with the need also to provide for
safe operation because of the liberation of acidic fumes.
16
17 It has now been found possible to provide solid
18 catalytic compositions by novel methods which do not require
19 evaporation of large quantities of aqueous media and/or acids.
Surprisingly, the solid compositions are different from and
21 superior to solid compositions produced by the prior art
22 methods.
23.
24 Accordingly, it is a primary object of the present
invention to provide new methods for producing solid sensitizer
26 compoqitions, the methods in general involving (i) precipitation
27 of the com~osltion from aqueous media or a hot melt or (ii)
28 ~he formation thereof by intimately blending dry components or
29 the catalyst.
_3
. . . .
.
.
¦ lI19150
Additional objects and advantages will be set forth !
2 in par~ in the description which follows, and in part will be
3 obvious from the desciption, or may be realized by practice o~
4 the invention, the objects and advantages being realized and
attained by means of the methods, processes, instrumentalities
6 and combinations particularly pointed out in the appended
7 ¦- claims.
9 ¦Description of the Invention - To âchieve the
I . .
¦ foregoing objects, and in accordance with its purposes as
11 ¦ embodied and broadly described~ the present invention relates
12 ¦ to (i) precipitation and (ii) dry blending methods for the
13 ¦ preparation of solid compositions, dissoluble in media comprising
14 ¦ water to provide sensitizing solutions for rendering surfaces
¦ receptive to the deposition of an adherent electroless metal.
16 I The solids comprise a composition consisting of three components:'
17 ¦ (a) A compound of an unreduced icn of a precious
18 I metal selected from the group consisting of the precious metals
19 ¦ of the fifth and sixth periods of Groups VIII and IB of the
¦ ~eriodic Table of Elements:
21 ¦ (b) a compound of a Group IV metal of the Periodic ¦
22 ¦ Table of Elements which is capable of two valence states; and
23(c) an anion capable of forming a stable moiety
24 with both valence states of the Group IV metal, preferably the
gram atomic ratio of components (a~ to (b) to (c) will be 1:
26at least 1: at least 3, e.g., from about 1:1:3 to 1:6:24.
27
28The term "solid" contemplates, e.g., dry but
29 hydroscopic powders, solid hard lumps (also ~ery hydroscopic),
a compacted precipitaté or a paste, slurry-or liquid comprising
31 predominantly solid particles.
. '' I
- ~ "
- 1~19150
According to one feature of the invention, the
2 solid is prepared by precipitation from a mixture, e.g., a
3 solution comprising water, of the components (a), (b) and (c).
4 Preferably, prior to precipitation,an aqueous solution of com-
5 - ponents (a) and (c) will be mixed with an aqueous solution of
6 components (b) and (c) and the mixture heated a~ from 80C. to
7 its ~oiling point to permit substantial completion of the
8 formation of an especially active form of the sensitizer.
9 Alternatively, a composition will be prepared from components
at least one of which melts and dissolves the others, when
11 heated, and the solid wili form in cooling.
12
13 Precipitation can be induced by, e.~., ra-sing
14 the pH to cause separation of the sensitizer. As will be
seen, precipitation can b~ made to occur after the sensitizer
16 is formed or simultaneously as it is formed, in the l~tter
17 case by carrying out the preparation in an alkaline solution.
18 In the former case, if the sensitizer solution is treated with
19 a basic reagent, e.g., an alkali metal hydroxide, e.g., NaOH,
or an alkaline earth hydroxide, a carbonate, ammonium hydroxide,
21 an amine hydroxide, or, indeed, any rea~ent commonly employed
22 to raise pH, the sensitizer precipitates at a pH beginning
23 between 1.5 and 2. The precipitated sensitizer and any co-
24 precipitated salts, e.g., Sn(OH)Cl, can then be separated from
the aqueous liquor by filtration, centrifugation, decantation,
26 and the like. Of course, the pH can be raised even higher,
27 e.g., pH 5-11, to effect a ~.ore complete precipitation of the
28 salts. At the lower pH values, some of the salts may not be
29 completely precipitated and at the higher pH values, they may
sesrt edissolve if an alkaline metal bydroxide is uted.
,
' '
. . .
'
~ll91SO
C-3l L , ,
1 I These factors are easi'y controllable however by observations
2 ¦ well within the skill of those in this art. .
3 I
¦ The solid sensitiæer may also be made and
precipitated simultaneously in an alkaline solution. Components
¦ (b) and (c), e.g., SnC12, can be dissolved in water and treated
7 1 with enough base to render the solution alkaline. Then component
8 (a) and (c), e.g., PdC12, can be added and a precipitate of
9 sensitizer will form and this can be recovered as described
above.
11
12 ¦ Alternatively, precipitation can also be induced
13 ¦ by preparing a "near" saturated hot solution and allowing it
14 ¦ to cool. The basic concept is to provide the sensitizer in a
lS ¦ hot aqueous medium with a high concentration of salts. In t~e
16 ¦ case of Group IV metal halides, e.g., SnC12.2H20, which ha~e
a relatively low melting point (37.7.C. for SnC12.2H20), or
18 the corresponding low melting germanium compounds, these act
19 as "hot melt" liquids after all of the excess water has been
removed during preparation of the near saturated solution.
21 Excessive heat is avoided to preclude evaporating to dryness,
22 then the mixture is allowed to cool and the solid sensitizer
23. i8 formed. The mixture can, as i~ mentioned above, also be
24 prepared in a "hot melt" fashion, i.e., without water being
25 added.
26 Obviously, as will be understood precipitation can
27 also be brought about by the addition of a counter-ion, e.g.,
28 triphenylarsonium ion, which combines with the solid co~position
29 (in ionic for~) to cause it to precipitate.
-6-
,
~ . . .
.
,:
'
~l~9~5V
A further preferred feature is to produce the solld
sensitizer by intimately blending solids comprising components (b) a~.d ~c),
e.g., SnC12, with components (a) and ~c), e.g., PdC12. The intimate blend
can be produced in any conventional fashion, but preferably ball milling
will be used. Of course, other solid components can also be included, e.g.,
alkali metal halides, e.g., sodium chloride and solid acids, e.g., tartaric
acid, and the like.
In all cases, the solid product can be stored for
future use, preferably in a closed container to avoid air oxidation.
10 - The products can be broken up and co-mixed with otherconventional dry addition agents such as salts, e.g., NaCl, NaHSO4, and the
like, dry acids, such as tartaric acid, citric acid and the like, stannous
chloride, germanium chloride, lead chloride or other halides, and the like,
surface active agents such as perfluorosulfonic acids and the like, stabilizers
and so forth all can be added. All such products can later be dissolved in
water or an acid solution for use as a sensitizer solution in accordance with
; the teachings typically set forth in the above-mentioned Zeblisky patent,
U.S. 3,672,923.
The sensitizers with which the instant invention is
concerned are formed reversibly. Therefore, an excess of component (b) with `
respect to component (a) appears to enhance their formation. It has been
found, however, that too much of an excess of component tb) results in a
reduced sensitizing
1~9 150
-1. ' I . . .
1 capability, Below a ratio of 3 gram atoms o~ componcnt (b)
2 for each mole of precious metal, the anion, while
3 formed, is difficult to stabilize. On the other hand, if the
amount of component (b) is in excess of about 100 gram atoms
per mole of precious metal compound sensitizing activity is
6 noticeably reduced. In practice, a solution containing a
7 relatively large excess of component (b) is preferred for long
8 operating life. Best results are obtained whe~ an excess of
9 component (b) is present in an amount.to provide from about
~0 S to 70 gram atoms of component (b) for each mole of precious
11 metal in the total composition.
- 12
13 ¦ In addition to preferring compositions which contain
14 ¦ a relatively large excess of component (b), it is preferred to
¦ use a large excess of component (c) to solubilize the composition .
16 ¦ In the most preferred embodiments, this will be introduced in
17 ¦ the form of a halogen compound, preferably an alkali metal halid .
18 ¦ e.g., NaCl or NaBr or a trihalotin (II) compound, e.g., SnC13~ ,
~9 ¦ or as HCl. Extremely large excesses of this component do not
1 seem to be detrimental to sensitizing activity. As to HCl, this
21 1 seems to serve a two-fold purpose: it provides both a large
i2 excess of Cl- ion and also H+ ions, both assisting in the
23. solubilization of the powdered product. L~ pH alone, as
24 produced, for example, by fluoboric acid does not solubilize
the powder unless excess component (c) too is present, e.g.,
26 80dium chloride can be added. A high excess of component
27 tc), e.g., sodium chloride alone, 25 to 100 moles per mole of
.28 complex, helps dissolve the sensitizer and any excess component
29 (b). However, for example, if componer.t (b) is stannous chlorid
.30 or a similas hydrolyzable composition which forms a basic sal~,
~ ,. . ~~ . .
. , ., , ' ''I
- '
,
,f`~ I ' ' 1~19150 ''.
1 ¦ e.g., Sn(OH)Cl, unless acid too i8 present to prevent hydrolysis,
2 an insoluble hydrolysis product is formed which appears to
3 ¦ ads~rb ~he composition causing it to be inactive as a sensitizer.
4 I Accordingly, in preferred embodiments, to prevent hydrolysis of
¦ the Group IV metal, i.e., component (b), acid will be added.
- 6 ¦ High concentrations of acid are preferred, as will be explained
7 ¦ hereinafter.
8 I
9 ¦ While it should not be construed as limiting the
¦ invention, it is believed that the reaction which occurs between
11 ¦ the metals and the anion results in the formation of ~ore than
12 one and possibly several compounds. Empirically, these can be
13 depicted as including complex anions of the formula~
14 (MeSn2x8)-2; (MeSnX6)-2;
(Me2Sn4X14)~4; (Me2Sn4X16) ;
16 (MeSnsX14)~3; (Me3SngX20) ; or
17 (Me2sn4X18)-4; (MeSn4X12H) ; or ~
18 mixtures thereof, wherein Me is Ru, Rh, Pd, Os, Ir~, Pt, Au or a
19 mixture thereof, and X is halogen, i.e., fluorine, chlorine,
bromine, or iodine; preferably chlorine or bromine. Preferred
21 complexes are those wherein Me is Pd or Pt, and X is chlorine.
i2 .
23. . The concentrations of the components of the com-
24 position are expressed interms of gram atomic ratio. The-efore,
25 thç gram atomic ratio of precious metal to Group IV metal to ¦ ;
26 anion of the compositions most preferred in the present invention
27 is at least from about 1:1:3 up-to, for example, 1:6:24, or .
28 higher.
29 / -~_
t
.'' , , ' " , ': ' " .
,', " ' ' ~'.''': ' '""' ''.
, .:
, : . ... .. . .. : -
.
. .. ..
~ ~19150 . I
As is explained above, it is a preferred feature
2 of this invention when preparing particularly preferred
3 ~ensitizing solutions, most notably those containing complexes
4 of palladium, stannous chloride, to employ an excess of Group IV
metal and 2 large excess of the anion, (c) with respect to
6 components (a) plus (b). Especially preferred is to use the
7 same anions as component (c).
9 In one manner of proceeding, the compositions are
prepared by heating the salts of the precious metals and a
11 Group IV metal salt in an aqueous solution of suitable acid
}2 and inducin~ precipitation. Among the acids that may be
13 mentioned are hydrochloric acid, hydrofluoric acid, sulf~lric
14 acid, citric acid, acetic acid, and ~he like. Preferably, the
anion of the inorganic acid corresponds to the anion of the salt
16 of the precious metal, or to the anion of the Grou? IV metal
17 salt. Where the anions of the precious metal salt and the Group18 IV metal salt are the same, th2 anion or the acid should pre-
19 ferably correspond to the cc~mon anion of the salts. Where the
anion of the precious metal differs from that of the Group IV
21 metal salt, the anion of the acid preferably corre3ponds to the22 anion of the precious metal salt. However, acids h~ving anions
23 which differ from the anions of the precious metal salt or of
24 the Group IV metal salt may also be used. The hydride anion, H-,
can be part of the complex. Preferred anions are Cl- and
26 SnC13.
27
28 In essence, the solid comprises a compound which is .
29 formed between the metals and the anion. The preferred palladi
¦ chloride tin chloride solid compound produced by this invention~
, I ' ~
, - .
1119150
. .
is acid soluble. Solid composltlons comprlslng the catalyst may be dissolved,
then diluted to levels of concentration whlch can easily and reproducibly be
directly formulated into active sensitizing solutions. In other words, the
invention makes available stable sensitizing solutions comprising significantly
lower concentrations of precious metal compound than can be produced by other
known methods, excluding, of course, the methods of U.S. patents No. 3,682,671
(Auq. 8/72~ and No. 3,672,938 (June 27/72) and the technique of above-mentioned
Zeblisky, U.5. 3,672,923.
,~ The sensitizing solution prepared by diluting the solid
composition comprises an acidic aqueous solution of a precious metal as defined
above consisting of ta) a precious metal compound, (b) a Group IV metal com-
pound and (c) a compound of an anion. Among the pre-cious metals that may be
employed are palladium, platinum, gold, rhodium, osmium, iridium and mixtures
of these metals. The inorganic and organic acid salts of these metals, and
of the Group IV metals, such as the chlorides, bromides, fluorides, fluo-
borates, iodides, nitrates, sulfates and acetates of stannous tin, titanium
and germanium among others may be used. Other acid salts of the precious
metals and Group IV metals will readily suggest themselves to those skilled
in the art. The salts are preferably soluble in water, or in organic or in-
organic acid aqueous solutions. Among the salts, the chloride is preferred,both for the precious metal, and the Group IV metal compound. The preferred
precious metals and Group IV metal are palladium or platinum, particularly
palladium, and stannous tin. In the sensitizing solution bath the precious
metal concentration should be from at least about 0.003 to about 1.5 grams/
llter of solutlon. ~7hile the higher
-- ,11 --
1119~50
end of this range causes sensitization to be completed ln very
- 2 abbreviated periods of time, e.g., ten seconds, the lower end
3 of this range is normally more economic.
As is explained in Zeblisky, U.S. 3,672,923, above-
1 6 mentioned, highly acti~e sensitizin~ solutions are prepared
7 by dissolving such solid compositions a liquid acid or a
8 mixture of water and an acid, until the concentration of compo-
9 nent (~) has been reduced to a concentration of from about O.OQO~
grams/liter to about 1.5 grams per liter.
' 11 ..
12 ' The sensitizers render surfaces receptive to the
13 deposition of an adherent electroless metal by known procedures.
14. For example, the particular acidic precious'''metal solutions
render conductive and non-conductive materials receptive to the
16 deposition of electroless copper, nickel, cobalt, palladium,
17 gold or silver, and especially to copper or nickel.
18 In use, the concentration of the acid in the
19 sensitizing solutions depends upon the strength oE the acid
employed. The concentration of the acid should be at least
21 sufficient to prevent hydrolysis of the Group I~ metal, at the
22 final concentration. A suitable lower limit is 0.001 Normal. I
23 At the upper end, the concentration of the acid may be as high
24 as 15 Normal, or even higher. When strong acids are used, the
concentration of'the acid in the sensitizing solution varies
26 betweenabout 0.02 and 7.5 Normal, preferably the pH is usually
27 1.5 or lower. When weak acids are used, the concentration of
28 the acid'in the sensitizing solution approaches the upper limit
29 given hereinabove. The concent,ation of acid in the sensitiz'ng
solution should, of courAe, al~o be high enough to solubilize
. - l
,
11 1119 ~50
l the salts of the precious metals and the Group IV metal and
2 also be high enough to render the solution suit~ble for use
3 as a sensitizer for the material being treated. Care should
4 be used in selecting the acid concentration to insure that the
specimen being treated is not adversely atta ked or corroded
6 by the treating solution.
8 In use, the Group IV metal ion concentration m~y
¦ vary widely but must be maintained in excess of a stoichiometric
¦ amount based on the amount of precious metal ions present in
11 ¦ the sensitizing solution. Normally a large excess of, for
12 ¦ example, stannous chloride, is maintained to allow for air
13 I oxidation of the stannous ion. Illustratively, concentrations
14 ¦ of as high as 50 grams per liter of stannous chloride are not
¦ detrimentaL to the effectiveness of ehe sensitizing activity
16 ¦ of the diluted solutions.
17 1
18 ¦ In use, the sensitizing solutions resulting from
19 1 dilution of the solids prepared by the present invention may
¦ contain additional agents to stabilize the solution, e.g.,
21 ¦ against the effects of atmospheric oxidation. Such agents will
22 ¦ include the use of additional quantities of the Grolp IV metal,
23.1 as for example, additional stannous chloride may be added to a
24 ¦ palladium-stannous chloride sensitizing solution, as well as
¦ compounds, such as organic hydroxy compounds (ols), dihydroxy
26 ¦ compounds (diols) and polyhydroxy compounds (polyols), the
27 ¦ fluorinated hydrocarbon wetting agents and hydrogen fluoride.
28 ¦ One result of the addition ~f such compounds to the sensitizing
-29 ¦ solutior. is the inhibition of oxidation of the Group IV metals
¦ and the subsequent reduc~ion of the precious metals.
~ I ~ -i3-
,. - ,.... , : : ~ -
-
119150
-1 The stabilizers, if solid, can be compoundet with the solid
~ sensitizer or they can be co-precipitated therewith by mixing
3 solutions and evaporating the solvents.
~ . ' .' '.
5 ' Illustrative of the conductive and non-conductive,
6 metallic and non-metallic surfaces which can be plated uniformly
7 with adherent electroless'metal by use of the sensitizing
8 solutions produced by diluting the solids prepared by'the present
g invention are plastic surfaces and surfaces of metallic copper,
iron, nickel, cobalt, silver, gold and alloys thereof, such as
11 brass, sterling silver and the like. The present invention can
12 be employed to render a surface catalytic to the reception of
13 such metals as copper, nic~el, palladium, cobalt, silver, gold
14 and the like.
16 Such sensitizers lead to practically complete
17 avoidance of the deposition of a flash coating of precious metal
18 from the sensitizing bath. A flash coating of precious metal
19 normally leads to a low grade of adhesion. Also, avoidance of
such deposition economically conserves the precious metal.
21 Solid sensitizers can also be incorporated into a plastic base
22 for the preparation of pre-sensitized substrates.
23
24 Description of the Preferred Embodiements - The'
25 following examples are provided for illustrative purposes and
26 may include particular features of the invention. Howe~er,-the
27 examples should not be constured as limiting the invention; many
28 variations of which are possible without departing from th~
29 spirit or scope thereof.
/.
.'' '.
. ' ~ ' ' '.
: ' ' '
9150
i EX~LE 1
2 ¦ A solid composition, dissolvable to provide a
3 ¦ sensitizing solution is prepared.
4 1
¦ A first solution is prepared comprising the
6 ¦ following ingredients:
7 ¦ palladium chloride (g.) 10
8 ¦ hydrochloric acid (3r/O,ml.) 200
9 ¦ water to make total (ml.) 500
~0 I
11 ¦ The palladium salt dissolves slowly in the acid-
12 ¦ water mixture.
13 I
14 ¦ A second solution is prepared comprising the
I following ingredients:
16 ¦ stannous chloride dihydrate 800 grams
17 ¦ hydrochloric acid (37%) 500 m~.
18 I ~
19 ¦ The first solution is added to tne second with
¦ agitation and the mixture is heated to 85C. and then boiled
21 ¦ in a well ventilated place for 1.5 hours, during which time it
22 ¦ changes color from blue or purple, through green, then straw-
23 ¦ yellow and, finally, brown.
24
The mixture is allowed to co~l. The mixture is
26 diluted with 15 parts of water and the pH is raised by the addi-
27 tion of NaOH during which a gray precipitate forms, pH 1.~ to
28 2. Additional NaOH is added, keeping the mi~ture cooled to
2g about 23C., and the gray precipitate disappears and oniy 2
black precipitate remains. The mixture is centrifuged and
. -/S-. ' .
Il 11 19 15~
1 washed with alkali solution. There i9 obtained a solid composi-
2 tion according to this invention, which is a black powder. The
black solid is diluted with sufficient 4 N HCl and adding
4 SnC12.H2O to produce an active sensitizing solution, which
contains Pd ion at a concentration of 0.5 g./l., SnCl2.2H2O at 40
6 g./l. and including 0.04 g./l. of FC-95 surface active agent.
7 :
8 EX~LE 2
9 A solid composi.ion, dissolvable to an active
sensitizing solution is prepared and simultaneously precipitated.
' 11 . ' -
12 Add 8.5 g. SnC12 to one liter water. Add a sol-
13 ution of NaOH until the precipitate formed redissolves. Add
14 approximately 10 g/l. more NaOH. Add 4 g. PdC12 from a solution
containing 50 g/l. PdC12 and 5 ml./l. HCl. A black precipitate
16 forms. The precipitate is separated from the solution as a
17 solid sensitizer.
18 .
19 For use the precipitate is dissolved :n a solution
of hydrochloric acid and stannous chloride to produce a solution
2~ with the following formula: -
22 0.5 g./l. PdC12
23 100 ml./l. HCl
24 55 g./l. SnC12.
26 ; EXAMPLE 3
27 A solid sensitizer is prepared under "near"
28 saturation conditions:
~29
25 ml. of a solution containing 260 g./l. PdC12
_/6-
. ' ~ ' .
.
.
11 1119150 - I
1 and 400 ml./l. HCl is added to 40 ml. of a-solution ~ontaining
2 800 g./l. SnC12.2H20 and 500 ml. HCl and placed in a flask. The
mixture is boiled very slowly for one hour.. Sufficient hezting
4 must occur to boil off excess free HCl and water; but ~xcessive
- 5 heat must be avoided to avoid overheating the sensitizer which
6 "scorches" it and renders it less active. After the heating
7 step, the mixture is allowed to cool. A solid sensitizer product
8 is formed upon cooling. A solid product is formed because t~e
excess free water and HCl have been boiled off during the heating
step. SnC12.2H2b which melts at 37.7C. keeps the mixture in
11 a liquid form during the latter part of the heating step provided
1~ excessi~e amounts of heat are not applied. When the mixture ~s
13 cooled to room temperaturo, the SnC12.2H2O freezes and the
14 sensitizer mixture becomes a solid product.
~
16 For ùse as a highly active sensitizer, the solid
17 catalyst product is dissolved in a solution of stannous chlGride,
18 hydrochloric aci~, and FC-95 to produce a solution of the
19 following composition:
PdC12 0.5g.
21 SnC12 25 g.
22 FC-95 wetting agent 0.05 g.
23 Hydrochloric acid (37%) 350 ml.
24 Water (to make) 1000 ml.
26 . EXAMPLE 4
27 A solid catalyst is prepared under "hot melt"
28 conditions. A mixture is prepared comprising .625 g. of PdC12;
29 3.48 g. of NaCl and 32 g. of SnC12.2H2O. The mixture is heated
and the SnC12.2H2O melts and dissolves the other components.
. _,7_
. ' .
I
YC-31 L
~119~50
l After keeping the melt,heated for about 1 hour, it is cooled and
2 solidifies. The solidified catalyst is dissolved in a solution
3 of stannous chloride, hydrochloric acid and FC-95 wetting agent,
4 as described in Example 3 to produce an active sensitizer
S composition.
' '6
7 EXAMPLE 5
,
8 A solid sensitizer is prepared by the intimate
9 blending technique, as follows: '
10'
ll 40 g. of SnC12~2H20 is placed in a ball mill jar
12 with 0.5 g. PdC12. The mixture is ball milled for 48 hours
13 using flint balls. A solid catalyst product is obtained.
,14, ' - " ' ',
For use, the catalyst material is dissolvPd in
16 ~ne liter of 4 Normal HCl.
17 ' ' ' ~ ' '
t8 EXAMPLE 6
19 A solid sensitizer is prepared by first making a
solution comprising the following ingredients:
21 , Gold chloride solution 2% - 5 cc.
22 Stannous chloride 2H20 - 17 grams '
23 Hydrochloric acid (37%) - 50 cc.
24 Water - to ' 1000 cc.
The stannous chloride is dissolved in water and the hydrochloric
26 acid is added. Then the gold chloride solution is added with
27 agitation. A small amount of p,recipitate forms and is removed
28 by filtration. Then the pH is raised by adding NaOH until
29 formation of a precipitated gold-stannous chloride compound
is complete. This is recovered and dried, and can thereafter
,.
.' .
. ~
PC-31 L ¦¦
slso
1 be redissolved in water to produce an active sensitizing
2 solution as described above.
4 EXAMPLE 7
A solid sensitizer is prepared by making an
fi aqueous solution comprising:
7 Palladium chloride - 1 gram
8 Fluoboric acid (49%) - 50 cc.
9 Stannous fluoborate - lO cc.
Water - to - 1000 cc.
11
12 The pH is raised by adding NaOH until formation
13 of a palladium-stannous fluoborate precipitate is su~stantially
14 complete. This is recovered and dried, and can thereafter be
redissolved in water to produce an active sensitizing solution
16 as described above.
17 . : ~ -
18 EXAMPLE 8
19 A solid sensitizer is prepared by making
an aqueous solution comprising:
21 Palladium chloride -4 grams
22 Sulfuric acid (98%) -140 cc.
23 Stannous sulfate -20 grams
24 Water - to -lOO cc. `
26 The pH is raised by adding NaOH until formation
27 of a palladium-stannous sulfate.precipitate is substantially
28 complete; This is recovered and dried, and csn tnere~fte~ be
29 redissolved in water to produce an ac~ive sensltizing solution
3o as described above.
, - '
,, . ~ . .
" .
I ~1191 SO
1 EXAMPLE_9
A ~olid sensitizer is prepared by making an
3 aqueous solution comprising:
4 Platinum chloride - 1 gram
Stannous chloride - 20 ~rams
6 Hydro~hloric acid (37%) - 40 cc.
7 Water - to - 1000 ml.
. 9 The pH is raised by adding NaOH until formation
of a platinum-stannous chloirde precipitate is substantially
11 complete. This is recovered and dried, and can thereafte,
12 be redissolved in water or in aqueous acid to produce an active
13 sensitizing solution as described above.
14 ;
E~AMPLE 10
1~ One gram of platinum chloride is placPd in a ball
17 mill jar with 20 gra~s of stannous chloride dihydrate. The
18 mixture is ball milied for 48 hours using flint balls.
19 A solid catalyst product is obtain2d, which can be dissol~ed
2d in one liter of 4 Normal HCl for use as a sensitizing solution.
21 :
22 EXAEPLE 11
23 . Add 8.5 g. of SnC12-2~20 to one liter of water.
24 Atd a solution of NaOH until the precipitate which forms
redissolves. Add about 10 g./l. more of ~aOH. Add 4 g. of
26 rhodium chloride and collect the black precipitate which fo~ms.
27 For use, the precipitate is dissolved in a solution of hydro--
28 chloric acid and stannous c~loride to produce a concentration
29 of o. 5 grams/liter of rhodium chloride.
, ' ,
. :
.
,, .
.. . .
: . , .
.. ~ . .
I PC-31 L
~l~gl50
EXAMPLE 12
2 ¦A solution is prepared comprising:
3 1 Palladium bromide - 1.75 gr~ms
I - Acetic acid (99.5%) -880 cc.
5 ¦ Stannous bromide -30 grams
6 ¦ Water - to -1000 cc.
7 1
8 ¦The pH is raised by adding ~aO~ until ~ormation
9 ¦ of a palladium-stannous bromide/acetate compound precipitate
¦ is substantially complete. This is recovered and dried, and
11 ¦ thereafter is redissolved in aqueous acid to produce an active
12 1 sensitizing solution as described above.
13 1
14 ¦ EXAMPLE i3
15 ¦A solution is prepared comprising:
16 .¦ Palladium iodide ~ 2.50 gram~
17 1 Hydrochloric acid (37%) - 880 cc. `
18 ¦ Stan~ous iodide -60 grams
19 ¦ Water - to -1000 cc.
~ I
¦lhe pH is raised by adding NaOH until formation
22 ¦ of the palladium-stannous iodide/chloride compound precipitate
-23 -¦ ~s substantially complete. This is recovered and dried, and
24 ¦ thereafter is redissolved in aqueous acid to provide an active
~5 ¦ sensitizing solution as described above.
26
27
28 1
29 I .
~rl I
, : '
PC-31 L
~-~ ~ 9 15
.,--- ' .
Substituting for the palladium chloride, stoich-
2 iometrically-equivalent amounts of the following: ruthenium
3 chloride (RuC13~; rhodium chloride (RhC13); osmium chloride
4 (OsC13); iridium chloride (IrC13); and platinum chloride (PtC14)
S will provide solid compositions according to this invention
6 containing, respectively, ruthenium, rhodium, osmium, iridium
7 and platinum.
9 EXAMpLE 14
Sensitizing solutions are prepared by taking
11 appropriate weights of the solid compositions from E~amples
12 1-4 and dissolving them in a mixture comprising 490 ml. or 37
13 percent hydrochloric acid and 490 ml. o water. The resulting
14 solutions will contain about 0.6 grams/liter of palladium in
the form of an active palladium-stannous chloride complex and
16 will have good catalyti~ activity.
7 ~
18 It is noted that while the use of stannous chloride
19 is preferred iR the practice of thepresent invention, other
stannous tin compounds such as, for example, stannous fluoborate
21 and stannous sulfate, as well as othe~ Group IV metal compound~,
22 e.g., the analogous germanium and lead compounds, are also
23. suitable for use in the seeding, i.e., sensitizing co~positions
24 described herein and in equivalent concentrations.
26 To demonstrate sensitizing activity, panels are
27 immersed in the solutions prepared from the dissolved solids.
28 These contain from 0.0005 to 2.5 grams/liter of precious metal.
29 After a suitable period of time, the panel surfaces including
any side walls of the apertures defined therein are thoroughly
. -22- .
_
9~50
1 rinsed with water to entirely remove the excess sensitizing
2 solution there~rom. Conventional electroless plating baths are
3 then used for the deposition of the ad~erent metal after
4 sensitizing the plating surface. Typicall~, electroless copper
deposition ma~ be followed by electroplating with copper or
6 other metals to build ~p copper thicknesses of O.OCl to 0.002
7 inch or greater.
As one e~bodiment, in the printed circuit industr~J,
electroless copper is ordinarily deposited on the sensitized
11 surfaces of apertures formed in plastic insula~ion sheets whieh
12 have conductivP copper foil laminated on both top and bottom
13 surfaces, and thereby conductive pathways between the top and
14 bottom and produced. -
16 Although the invention has been described and
17 illustrated by reference to particular embodiments thereo,
18 it will be understood that in its broadest aspects, tke invenlion
19 is not limited to such embodi~ents, and that variations and
substitution of such equivalents may be resorted to within the
21 scope of the appended claims.
22 This application is a division of copending
23 Canadian application Serial No. 286,221 filed September 7,
24 1977.
26
27
:28 . ,
29
~0
. 23 -
. ~, . ' .
