CONDITIONING OF POLYAMIDES FOR ELECTROLESS PLATING

PREPARATION DE POLYAMIDES POUR PLACAGE NON ELECTROLYTIQUE

English Abstract

Abstract of the Invention
Polyamide substrates are pre-conditioned for electroless
plating by contact with an alkaline aqueous solution having
a pH of at least about 10 and etched with an acid solution.
The acid solution is preferably an aqueous solution of an
organic acid containing at least two carbon atoms, particularly
an acetic acid compound, such as trichloracetic acid.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a process for electroless plating of polyamide
substrate wherein the substrate is etched with an acid prior
to electroless plating, the improvement which comprises
conditioning the substrate prior to etch by contact with an
aqueous alkaline conditioning solution having a pH of at least
about 10 and maintained at a temperature of from about 150°F
to the lesser of the boiling point of the solution and the
softening temperature of the polyamide substrate for a time
sufficient to enhance acid etch of the polyamide substrate.
2. A process as claimed in claim 1, in which the polyamide
substrate is contacted with the conditioning solution for a
period of from about 0.5 to about 20 minutes.
3. A process as claimed in claim 1, in which the polyamide
substrate is contacted, prior to contact with the conditioning
solution, with a dilute aqueous solution of an organic solvent
for the polyamide for a time sufficient to soften the surface
of the polyamide substrate.
4. A process as claimed in claim 1, in which the polyamide
substrate is contacted following contact with the conditioning
solution, with a dilute aqueous solution of an organic solvent
for the polyamide for a time sufficient to soften the surface
of the polyamide substrate.
17

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5. A process as claimed in claim 1 in which the
conditioning solution contains an organic solvent for
the polyamide.
6. A process for preparing the surface of polyamide
substratres for electroless plating which comprises:
(a) forming a conditioned polyamide substrate for
etching by contacting the polyamide substrate with an aqueous
alkaline conditioning solution having a pH of at least about
10 and maintained at a temperature from about 150°F to the
lesser of the boiling point of the solution and the softening
temperature of the polyamide substrate for a time sufficient
to render the substrate receptive to etch by an organic acid;
(b) etching the conditioned polyamide substrate
by contacting the conditioned polyamide substrate with an
aqueous etch solution comprising at least one water soluble
organic acid containing from 2 to about 10 carbon atoms in
the molecule and present in the aqueous solution in a con-
centration of at least about 3 percent by weight of the solution
and sufficient to render the conditioned polyamide substrate
substantially uniformly receptive to a metal electroless plating
catalyst.
7. A process as claimed in claim 6 in which the
polyamide substrate is cleansed prior to contact with the
metal catalyst by contact with an aqueous acidic or basic
cleansing solution.
113-1 18

8. A process as claimed in claim 6 in which the
polyamide substrate is contacted, prior to contact with the
conditioning solution, with a dilute aqueous solution of
an organic solvent for the polyamide for a time sufficient
to soften the surface of the polyamide substrate.
9. A process as claimed in claim 6 in which the
polyamide substrate is contacted following contact with
the conditioning solution, with a dilute aqueous solution
of an organic solvent for the polyamide for a time sufficient
to soften the surface of the polyamide substrate.
10. A process as claimed in claim 6 in which the
conditioning solution contains an organic solvent for the
polyamide.
11. A process for preparing the surface of polyamide
substrates for electroless plating which comprises:
(a) forming a conditioned polyamide substrate for
etching by contacting the polyamide substrate with an aqueous
conditioning solution of at least one alkali metal hydroxide
in which the alkali metal hydroxide concentration of the
solution is from about 2 percent by weight of the solution
to solution saturation and maintained at a temperature of
from about 150°F to the lesser of the boiling point of the
solution and the softening temperature of the polyamide surface
for a time sufficient to render surface polyamide substrate
receptive to etch by an acetic acid compound;
13-1 19

(Claim 11 cont.)
(b) etching the conditioned polyamide substrate by
contacting the conditioned polyamide substrate with an aqueous
acid etch solution comprising at least one acetic acid compound
having the formula:
<IMG>
wherein each X is independently selected from the group
consisting of hydrogen, hydroxyl and halogen and in which
the acetic acid compound concentration is sufficient to render
the conditioned polyamide substrate receptive to a metal
electroless plating catalyst.
12. A process as claimed in claim 11 in which the
polyamide substrate is cleansed prior to contact with the
metal catalyst by contact with an aqueous acidic or basic
cleansing solution.
13. A process as claimed in claim 11 in which the
polyamide substrate is contacted, prior to contact with the
conditioning solution, with a dilute aqueous solution of
an organic solvent for the polyamide for a time sufficient
to soften the surface of the polyamide substrate.

2161:
14. A process as claimed in claim 11 in which the
polyamide substrate is contacted following contact with the
conditioning solution, with a dilute aqueous solution of an
organic solvent for the polyamide for a time sufficient to
soften the surface of the polyamide substrate.
15. A process as claimed in claim 11 in which the
conditioning solution contains an organic solvent for the
polyamide.
16. A process as claimed in claim 15 in which the
organic solvent is an alkali soluble organic solvent.
17. A process as claimed in claim 11 in which the
polyamide substrate is formed of a filled polyamide.
18. A process as claimed in claim 11 in which the total
alkali metal hydroxide content of the conditioning solution
is from about 10 to about 50 percent by weight of
the solution.
19. A process as claimed in claim 11 in which the
conditioning solution is maintained at a temperature from
about 170 to about 200°F.
20. A process as claimed in claim 11 in which the contact
time in the conditioning solution is from about 0.5 to about
20 minutes.
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12161:
21. A process as claimed in claim 11 in which the total
acetic acid compound concentration of the etch solution
is from about 3 percent by weight to solution saturation.
22. A process as claimed in claim 11 in which the total
acetic acid compound concentration of the etch solution is
from about 5 to about 60 percent by weight of the solution.
23. A process as claimed in claim 11 in which the
polyamide substrate is contacted with the etch solution
for a period of from about 10 seconds to about 15 minutes.
24. A process as claimed in claim 11 in which the acetic
acid compound is trichoracetic acid.
25. A process as claimed in claim 11 in which the acetic
acid compound is dichloracetic acid.
26. A process as claimed in claim 11 in which the acetic
acid compound is acetic acid.
27. A process for preparing the surface of polyamide
substrates for electroless plating which comprises:
(a) forming a conditioned polyamide substrate by
contacting the polyamide substrate with an aqueous condition-
ing solution of at least one alkali metal hydroxide in which
the total alkali metal hydroxide concentration is from about
10 per cent by weight of the solution to solution saturation
113-1 22

12161:
(Claim 27 cont.)
and maintained at a temperature of from about 150°F to the
lesser of the boiling point of the solution and the softening
temperature of the polyamide surface for a period of from
about 0.5 to about 20 minutes;
(b) forming an etched polyamide substrate by
contacting the conditioned polyamide substrate with an aqueous
etch solution comprising at least one acetic acid compound
selected from the group consisting of trichloracetic acid,
dichoracetic acid and acetic acid in which the acetic acid
compound concentration is sufficient to render the conditioned
polyamide substrate receptive to a metal electroless plating
catalyst.
28. A process as claimed in claim 27 in which the
polyamide substrate is cleansed prior to contact with the
metal catalyst by contact with an aqueous acidic or basic
cleansing solution.
29. A process as claimed in claim 27 in which the
polyamide substrate is contacted, prior to contact with the
conditioning solution, with a dilute aqueous solution of
an organic solvent for the polyamide for a time sufficient
to soften the surface of the polyamide substrate.
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12161:
30. A process as claimed in claim 27 in which the
polyamide substrate is contacted following contact with the
conditioning solution, with a dilute aqueous solution of
an organic solvent for the polyamide for a time sufficient
to soften the surface of the polyamide substrate.
31. A process as claimed in claim 27 in which the
conditioning solution contains an organic solvent for
the polyamide.
32. A process as claimed in claim 31 in which the
organic solvent is alkali soluble.
33. A process as claimed in claim 21 in which the
polyamide substrate is formed of a filled polyamide.
34. A process as claimed in claim 27 in which the total
alkali metal hydroxide content of the conditioning solution
is from 10 to about 50 percent by weight of the solution.
35. A process as claimed in claim 27 in which the
conditioning solution is maintained at a temperature
from about 170 to about 200°F.
36. A process as claimed in claim 27 in which the total
acetic acid compound concentration of the etch solution
is from about 5 percent by weight of the solution to
solution saturation.
24
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?161:
37. A process as claimed in claim 27 in which the total
acetic acid compound concentration of the etch solution
is from about 5 to about 60 percent by weight of the solution.
38. A process as claimed in claim 27 in which the
polyamide substrate is contacted with the etch solution
for a period of from about 10 seconds to about 15
minutes.
113-1 25

Description

11~3~:60
.,~.. I ~ ~
12161:JPG 1 CONDITIONING OF POLYAMIDES FOR ELECTROLESS PLATING
~.
Background of the Invention
The present invention relates to electroless plating
of polyamides, in particular, to providing a surface uniformly
receptive to metals which catalyze electroless deposition of
1 nickel and copper.
The benefits of electroless plated, non-conductive
articles, particularly plastic articles, are well known.
In the finished product, the desirable characteristics of
the plastic and the metal are combined to offer thereby
the technical and aesthetic advantages of each.
Polymeric substrates are conventionally plated by
pre-conditioning the surface by contact with an aqueous
solution of at least one organic compound active for
conditioning the surface of the plastic, etching with
2 a strong oxidizing acid or base, seeding the surface with
a noble metal catalyst, e.g., a palladium chloride solution,
then immersing the seeded surface in an autocatalytic
electroless solution where an initial coatinq of a conductive
metal, e.g., copper or nickel, is established by chemical
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`~ deposition. The metal deposit acts as a buss to allow a thicker
coating of metal to be built up electrolytically.
Attempts to adapt conventional procedures for electroless
plating of polymers to polyamides by us have resulted in a
failure to achieve a uniform adherent coat of metal. Having
found conventional electroless plating procedures ineffective,
a quest was initiated to discover a procedure to enable uniform
coating of polyamides with electroless deposited metals.
Summary of the Invention
In accordance with the present invention there is
; provided in a process for ~lectroless plating of polyamide
substrate wherein the substrate is etched with an acid prior to
electroless plating, the improvement which comprises conditioning
the substrate prior to etch by contact with an aqueous alkaline
conditioning solution having a pH of at least about 10 and
!; maintained at a temperature of from about 150F to the lesser of
, the boiling point of the solution and the softening temperature
of the polyamide substrate for a time sufficient to enhance acid
etch of the polyamide substrate.
Also in accordance with the invention there is provided
a process for preparing the surface of polyamide substrates for
electroless plating which comprises:
(a) forming a conditioned polyamide substrate for etching
by contacting the polyamide substrate with an aqueous alkaline
conditioning solution having a pH of at least about 10 and
maintained at a temperature from about 150F to the lesser of the
boiling point of the solution and the softening temperature of the
polyamide substrate for a time sufficient to render the substrate
receptive to etch by an organic acid;
(b) etching the conditioned polyamide substrate by
-- 2
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11~3Z~;O
contacting the conditioned polyamide s.ubstrate with an aqueous
etch solution comprising at least one water soluble organic acid
containing from 2 to about 10 carbon atoms in the molecule and
present in the aqueous solution in a concentrati.on of at least
about 3 percent by weight of the solution and sufficient to render
the conditioned polyamide substrate substantially uniformly
receptive to a metal electroless plating catalyst.
Further in accordance with.the invention there is provided
a process for preparing the surface of polyamide substrates for
; 10 electroless plating which comprises:
(a) forming a conditioned polyamide substrate for
etching by contacting the polyamide substrate with an aqueous
conditioning solution of at least one a.lkali metal hydroxide in
.: which the alkali metal hydroxide concentrati.on of thR solution is
.. 15 from about 2 percent by weight of the solution to solution
saturation and maintained at a temperature of from about 150F
to the lesser of the boiling point of the solution and the
softening temperature of the polyamide surface for a time sufficient
. to render surface polyamide s:ubstrate receptive to etch by an
acetic acid compound;
(b) etching the conditioned polyamide substrate by
contacting the conditi.oned polyamide substrate with an aqueous
acid etch solution comprising at least one acetic acid compound
having the formula:
~ O
X C - C
wherein each X is independently selected from the group consisting
of hydrogen, hydroxyl and halogen and in which the acetic acid
compound concentration is sufficient to render the conditioned
~olyamide substrate receptive to a metal electroless plating catalyst.
-- 2a

1~3260
Further in accordance with the invention there is
provided a process for preparing the surface of polyamide sub-
strates for electroless plating ~hich comprises:
(a) forming a conditioned polyamide substrate by contacting
the polyamide substrate with an aqueous conditioning solution of
at least one alkali metal hydroxide in which the total alkali
metal hydroxide concentration is from about 10 per cent by weight
of the solution to solution saturation and maintained at a
temperature of from about 150F to the lesser of the boiling
point of the solution and the softening temperature of the poly-
amide surface for a period of from about 0.5 to about 20 minutes;
(b) forming an etched polyamide substrate by contacting
the conditioned polyamide substrate with an aqueous etch solution
comprising at least one acetic acid compound selected from the
group consisting of trichloracetic acid, dichoracetic acid and
acetic acid in which the acetic acid compound concentration is
sufficient to render the conditioned polyamide substrate
receptive to a metal electroless plating catalyst.
Thus, it has now been found that electroless plating of
polyamides, particularly filled polyamides, can be enhanced by
first contacting the polyamide substrate with an aqueous alkaline
solution having a pH of at least about 10, preferably a solution
of at least one alkali metal hydroxide in which the alkali metal
hydroxide content is from about 2 percent by weight to solution
saturation, more preferably from about 10 to about 50 percent by
weight. The alkaline solution is maintained at a temperature
from about 150F to the lesser of the boiling point of the
solution and the softening point of the plastic. Contact is
for a time sufficient to enable etching by an acid solution.
The substrate is then contacted with an acid etch at
- 2b
.. ..
. .
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ll143Z60
ambient temperature or above. The concentration of the acid
is sufficient to render the polyamide surface uniformly
receptive to seeding by a metal catalyst. A preferred acid
solution is a solution comprising at least one organic acid
containing from two carbon atoms to about 10 carbon atoms
and having a solubility in water of at least about 3 percent
by weight of solution.
- 2c
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11~3Z60
12161:JPG
l The present1y preferred acid solutions are solutions
comprising at least one acetic acid compound of the formula:
wherein each X is independently selected from the group
consisting of hydrogen, hydroxyl and halogen.
Contact with the acid etch may be directly followed
by seeding the surface with a metal electroless plating
catalyst which are solutions of metal ions or suspensions
of metal particles.
Following seeding and activation of the metal catalyst by
conventional means, the surface can be uniformly plated with
electroless copper or nickel.
Etching may be followed by rinsing debris from the surface
of the substrate with an acid to alkaline rinse solution.
In carrying out the process of this invention in its
preferred embodiment, an alkali metal hydroxide solution is
used as the conditioner and is preferably employed at a
; 2 temperature from about 170 to about 200F at contact times
ranging from about 0.5 to about 20 minutes or more, depending
on temperature and caustic concentration. No damage has been
found from prolonged contact.
Contact time in the aqueous acid solution etch is normally
2 from about lO seconds to lS minutes at room temperature.
When, as is presently preferred, a solution of an acetic acid
compound is employed for etching the substrate, concentration
is normally at least about 3 percent by weight up to solution
saturation, preferably from about 5 to about 60 percent by
3 weight.
113-~

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In conducting the process of the invention, the article
may he treated by contacting the article in an aqueous
solution of an organic solvent for the polyamide, prior to
or following contact with the alkaline solution. Alternatively,
the organic solvent can be contained in the alkaline solution.
j The solvent in its solution is normally employed in a concen-tration up to about 2 percent by weight, preferably up to
about 1 percent by weight. Ethylene glycol, phenolic compounds
such as chlorophenol, cresols and salts thereof are presently
I 10 preferred. As indicated, solvent may be contained in its own
! bath or included in the alkaline solution so long as the
organic solvent is not hydrolyzed or degraded. The solvent
serves to soften plastic to aid attack by the alkaline
conditioner or acid etch.
¦ 15 As indicated, the substrate after etching may be
further processed to remove the debris of etching by contact
with acidic to basic wash.
! Detailed Description
¦ The present invention provides a process which enables
¦ 20 uniform electroless deposition of metals onto polyamide
substrates. In particular, the processes of the present
invention are directed to improvements in electroless plating
of filled and unfilled polyamides such as Nylon 6 and Nylon 6,6.
In its broadest aspects, the invention is directed to
conditioning the surface of a polyamide substrate with an
; aqueous alkaline solution having a p~I of at least about 10 to
render the surface receptive to attack by an acid etch.
~ 4 -

~` - ~ (
1~3260
12161:JPG
l Although solutions of alkali hydroxide are preferab1y
employed, there may also be used alkaline compounds such as
sodium metasilicate, trisodium phosphate, sodium carbonate and
the like, used alone, in admixture and/or in combination with
an alkali metal hydroxide.
When a conditioning solution of at least one alkali
metal hydroxide is employed, the solution has an alkali
metal hydroxide content of from about 2 percent by weight
of solution to solution saturation, preferably about 10
to about 50 per cent by weight.
~ ¦ The alkali conditioning solutions are, as presently
v- ¦ employed, maintained at a temperature from about 150F to
¦ the lesser of the boiling point of the solution and the
¦ softening temperature of the polyamide.
15 ¦ Contact is for a time sufficient to render the substrate
¦ receptive to attack by the acid etch; and after rinsing,
¦ is followed by contact of the polyamide substance with an
¦ acid etch solution. The preferred acid solutions are solutions
¦ comprising at least one soluble organic acid containing at
20 ¦ least two carbon atoms, and contact is for a time sufficient
¦ to render the surface receptive to a metal catalyst. The
¦ metal catalyst may be in the form of a solution of functional
¦ metal ions or as a dispersion of metal particles. It is
¦ presently preferred that the organic acid be an acetic
25 ¦ acid compound as defined below.
¦ As part of the process measures, water rinsing with
¦ deionized water is performed for good housekeeping between
¦ each step. The substrate may be treated with a dilute
¦ solution of solvent for the polyamide to soften the surface
30 l
.

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12l61:JPG
l of the polyamide to promote conditioning and/or etch.
Contact. with the solvent may be prior to or after contact
with the alkaline solution or contained in the alkaline
solution. It is presently preferred to contact the substrate
with the solvent following contact with the alkaline solution.
If desired, a solution of the solvent may be employed prior
to and following contact with the alkaline conditioner. The
solvent softens the surface of the substrate to promote
conditioning or etching. The solvent for the polyamide may
be contained in a separate bath or part of the alkaline solution.
In addition, the substrates may be contacted with an
acidic to basic solution subsequent to etch to remove debris
present on the surface of the substrate.
The procedure of contact with the aqueous alkaline
solution prior to contact with an acid etch is critical to
the process of the invention and the reverse of steps normally
conducted in electroless plating operations.
While reception of electroless plating onto the surface
of any polyamide may be enhanced, the polyamides to be
normally treated are filled polyamides as are conventionally
used in molding operations. Typical of such materials are
filled Nylon 6, Nylon 6,6 and the like.
The first essential step of the process is contacting
the polyamide substrate with an aqueous alkaline solution.
2 The presently preferred solutions are solutions of at least
one alkali metal hydroxide, such as sodium and/or potassium
hydroxide, present in a concentration from about 3 percent
by weight of solution to solution saturation, preferably from
about lO to about 50 percent by weight. Solution temperature
113-1 6

:~ ~ (- (-
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12161:JPG
1 is maintained from about 150F to the lesser of the boiling
point of the solution and the softe~ing temperature of the
polyamide substrate, preferably from a temperature of about
170 to about 200F.
S Contact time may vary from about 0.5 to 20 minutes or
more, depending upon temperature and the alkaline compound
concentration, although it has been found that prolonged
immersions will not damage the substrate. The object is
to condition the surface of the substrate to make it receptive
0 to attack by the acid etch.
Following water rinsing to remove the alkaline
; conditioning solution, the article is passed to an acid etch,
preferably one based on organic acids containing from 2 to
;; about 10 carbon atoms and having a water solubility of at least
about 3 percent by weight of solution. The presently preferred
etch is one comprising from about 5 percent by weight to
about 65 percent by weight of solution and more preferably,
from about 10 to about 25 percent.by weight of solution of
at least one acetic compound of the formula:
~' X C C ~
where each X is independently hydroxyl, hydrogen or halogen
2 with halogen preferred.
Contact is at ambient or room temperature although elevated
temperatures may be employed. Contact times range from about
. 10 seconds to lS minutes or more and are for a time sufficient
to etch the surface of the polyamide to a degree that it becomes
uniformly receptive to seeding by a metal catalyst.
`~! 3
113-1 7
,. 9
;'' '

11~3~60
12161:JPG
Among the acetic acid compounds which may be used there
may be mentioned trichloracetic acid, acetic acid, hydroxy-
aceti^ acid, dichloracetic acid, chloracetic acid, fluoracetic
acid, difluoracetic acid, trifluoracetic acid, bromacetic acid,
dibromacetic acid and the like. Trichloroacetic acid is presently
preferred.
Optionally, there may be employed as part of the process,
contact with an organic solvent for the polyamide. The solvent
may be in a separate bath used preceding and/or following the
alkaline conditioning solution or included in the alkaline con-
ditioning solutionr The organic solvent softens the surface of
the substrate to aid attack by the conditioning and/or etching
solutions. Typically, concentration of the solvent in its
solution is up to about 2 percent by weight, preferably up to
about l percent by weight. A wide variety of solvents for
polyamides may be used. The presently preferred solvents are
, ethylene glycol, chlorophenol, cresols and salts thereof. If
employed in the alkaline conditioner as its solution, the sol-
; vent should not be hydrolyzed or degraded by the alkaline batch.
~ 20 In addition, subsequent to contact with the acid etch,
: the substrate may be brought into contact with an acid to
~, alkaline solution of either an organic or inorganic acid or
base to cleanse the surface of debris, i.e., filler and/or
degradated resin. Such solutions are normally maintained at
room temperature, although elevated temperatures may be
¦ employed. Although solutions used as the conditioner may be
r'; ¦ employed, solutions having an acidic or alkaline compound
, ¦ in concentration in the range up to about 20 percent by weight,
: ¦ preferably up to about l0 percent by weight may also be
30 ¦ employed. Functional acids include hydrochloric acid, sulfuric
~ acid, phosphoric acid, nitric acid, formic acid, acetic acid
113-l 1 8
.' I
'

~1~3,''260
and the like. As indicated, there may also be used as a
convenience to minimize the number of baths involved, the
alkaline solution used for conditioning the substrate.
- Alternative solutions include such as solutions of borax,ammonium bifluoride and the like. The concentration is that
- which will enhance surface finish without detracting fromthe ability of etched surface to accept a metal catalyst.
Whether or not the cleansing treatment is employed,
the article is rinsed in water, usually deionized water, and
seeded with a metal electroless plating catalyst.
The electroless plating catalysts employed may be
nob~e metal or non-noble metal based. Non-noble metal
catalysts are described in United States Patent 3,958,048 to
the same assignee as this application.
A noble metal catalyst in an aqueous medium is
presently preferred. By a "noble metal catalyst contained
in an aqueous medium" there is meant an ionic solution or
colloidal suspension of the free metals. Colloidal suspensions
are preferred. The noble metals include gold, platinum and
palladium, with palladium preferred.
A suitable ionic bath is one containing palladium
chloride in a concentration of about 0~2 grams per liter
solution and 3 ml of concentrated hydrochloric acid per liter
of solution. Following seeding, the palladium can be reduced
to the free metal state by immersion in a bath of a reducing
agent such as dimethyl amine borane.
Colloidal suspensions of noble metals are described
in United States Patent 3,011,920 to C.R. Shipley, Jr. Such
-- suspensions are colloidal in nature in which the noble metal
~ 30 colloid is maintained in suspension
. _ g _.
. ~
'~
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3~60
by a protective colloid, i.e., stannic acid colloids. Following
seeding, the colloid is removed by immersion in an acidic or
alkaline accelerator solution to remove the protective colloid
and expose the absorbed noble metal.
- 5 Although less preferred, there may also be employed a
seeding method which involves contacting the etched article
with a sensitizing solution containing stannous chloride
followed by immersion in an activator solution such as a
palladium chloride solution where the ionic palladium is reduced
to the free metal on the surface of the substrate.
Suitably activated, the article may be electrolessly
plated by conventional means. Electroless copper and nickel
formulations, such as those described in United States Patents
3,011,920 and 3,874,072, may be employed. Electroless copper
solutions are typically based on a soluble copper salt, such
as copper sulfate, a complexing agent for the cupric ion such
as Rochelle salt, an alkali hydroxide for adjustment of pH, a
carbonate radical as a buffer and a reducing agent for the
cupric ion such as formaldehyde.
Following electroless plating, the substrate may be
electrolytically plated by conventional means, with nickel, gold,
silver, chromium and the like to provide the desired finish on
the article. It has been observed that adhesion will increase
with age of the plate.
In the following Examples and Controls where the
article or substrate was contacted with an alkali hydroxide
solution, the bath was about 35 percent weight to volume sodium
hydroxide solution maintained at 200~F. Where contacted with a
_ ln

1143;Z60
` 12161:JPG
l hydrochloric acid solution, the solution was a 28.5 percent
(volume by volume) of concentrated hydrochloric acid in water.
The solution of trichloracetic acid (TCA solution) employed
was a 20 percent by weight to volume aqueous solution maintained
at room temperature. Seeding of the etched substrate was with
a proprietary colloidal tin-palladium catalyst as described
in U.S. Patent 3,011,920 at an acid molarity of about 1.7.
An alkaline accelerator was used to expose the palladium metal.
The catalyst was maintained at about 120F and the accelerator
at about 105F. The electroless copper solution employed was
Cuposit(TM) PM-990 manufactured and sold by the Shipley Company.
The electroless copper solution was maintained at ambient
temperature.
Following electroless plating, the article was
electrolytically plated when possible. In this operation, the
substrate was rinsed in deionized water, soaked in an alkaline
cleaner, then passed to a reverse current cleaner, an acid
dip, bright acid copper and nickel electrolytic plating
solutions and finally to a chromium plating solution.
Some plated articles were subjected to cycle testing to
determine adhesion performance under thermal stress conditions.
In this test the plated article was maintained at a temper-
ature of at least 180 F for l hour, then cooled to room
temperature and maintained at room temperature for 30 min-
; 25 utes then cooled to -20 F and maintained at that temperature
for l hour.
113-1 ll

~ ~ 3;~1i0
12161-JPG
lExample l
A p1ating grade of filled Nylon 6,~ known as Vydyne(TM)
RP-260, manufactured and sold by the Monsanto Company, was
- immersed for lO minutes in the alkali hydroxide solution then
water rinsed and immersed for l minute in the TCA solution.
The article was then rinsed in water, catalyzed, rinsed,
electrolessly plated with copper and electrolytically plated.
Initial plate adhesion ranged from l.0 to l.5 lb/in with
an average of 1.3 lb/in. The cycle test was successful.
Control l
The procedure of Example l was reversed in that the
article was immersed in the TCA solution prior to contact
with the alkali hydroxide solution. This resulted in skip
- plating and blistering of the electroless plate.
Control 2
; Control l was repeated except that immersion time in
the TCA solution was increased to 5 minutes. The electrolessly
deposited plate blistered.
Control 3
Example l was repeated except that immersion in the
TCA solution was omitted. This also resulted in blistering
; of the electroless plate.
, Example 2
Example l was repeated except that the article after
contact with the TCA solution was reimmersed in the caustic
solu~ion for lO minutes to cleanse the surface. There was
~.'
113-1 12

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':
12161:JPG
obtained uniform coverage of the electroless and electrolytic
plate. Initial adhesion ranged from l.S to 1.8 Ib/in with
an average of 1.7 Ib/in. The cycle test was successful.
:
Example 3
- Example 1 was repeated except that immersion in the TCA
solution was for 2 minutes followed by immersion in a
hydrochloric acid solution for 1 minute. The article uni-
; formly plated with electroless copper and was electrolytically
;~ 10 plated. Initial adhesion of the plate ranged from 1.3 to
' 1.8 lb/in with an average of 1.5 lb/in. The cycle test was
successful.
Control 4
In this test Example 1 was repeated except that the
Vydyne article was immersed in the hydrochloric acid solution
for 1 minute, rinsed, then immersed for 1 minute in the TCA
solution and again for one minute in the hydrochloric acid
solution. Small blisters developed in the electroless
plating operation with extensive blistering occurring in the
2 reverse current cleaning step preceding electrolytic plating
such that the article could not be electrolytically plated.
Control 5
; 2 An article molded of Vydyne(TM) RP-260 was immersed in the
hydrochloric acid solution for 1 minute, rinsed for 1 minute
in the TCA solution, followed by 10 minutes in the caustic
solution but at a reduced temperature of 160F. The electro-
less plate exhibited small blisters with large blistering
occurring in the reverse current cleaner.
113-1 13
'"'''`

`-~ ~ 3'~60
12161:JPG
1Example 4
An article molded of Vydyne(TM) RP-260 was immersed for lO
minu~es in the caustic solution, rinsed, immersed for l
minute in the TCA solution and for 5 minutes in a cleaner
- 5 which was a 50 percent volume by volume solution of glacial
acetic acid in water at room temperature. The article
accepted the electroless and the electrolytic plates.
Initial adhesion averaged 1.2 Ibs/in.
Example 5
10 An article molded of Capron(TM) XPN-1030, a filled Nylon 6
manufactured and sold by Allied Chemical Corporation, was
immersed in the caustic solution for lO minutes, rinsed, then
immersed in a 10 percent volume by volume solution of
dichloracetic acid for 5 minutes. The article accepted uniform
electroless and electrolytic plates.
Example 6
Example 5 was repeated except that immersion in the
dichloracetic solution was for 2 minutes at 120F. The same
results were obtained.
.'
Example 7
An article molded of Vydyne(TM) RP-260, following
immersion in the alkali hydroxide solution as described
in Example 1, was immersed for 15 seconds in a 90 percent
aqueous acetic acid solution at room temperature. The
etched article accepted an adherent deposit of electroless
copper, then adherent electrolytic pLates of copper,
nlckel and chrome.
113-1

11~3Z60
:'
12161:JPG
1 Example 8
The procedure of-Example 1, was repeated except that
the trichloracetic acid concentration was reduced to
10 percent by weight to volume. Immersion was for I minute.
The etched article accepted uniform adherent deposit of
electroless copper, an electrolytic plate of copper, nickel
then chrome.
Example 9
The procedure of Example 8, was repeated except that
the polyamide substrate was Capran(TM) XPN-1030. The results
were equally successful.
~'
Example 10
A substrate molded Minlon(TM) ll-C-40, a nylon manu~
factured and sold by DuPont, was immersed in a 2 percent
by volume solution of cresylic acid in a 5 percent by weight
volume aqueous solution of sodium hydroxide, maintained at
I 130 F for 5 minutes, then immersed in the alkali hydroxide
; ¦ solution maintained at 200F for lO minutes and for l minute
¦ in a 15 percent weight by volume aqueous solution of tri-
¦ chloracetic acid. The etched article accepted upon catalysation
¦ a uniform electroless plate of copper and an electrolytic
¦ plate of copper, nickel then chrome and passed the cycle test.
¦ Adhesion ranged from 2 to 3 pounds per inch.
25 I
¦ Example 11
¦ There was employed an unfilled nylon substrate formed
of Capron(TM) 8202F - Type 6 manufactured and sold by Allied
Chemical Corporation. The substrate was contacted with the
113-1 15

~1~3;260
1216l:JPG
1 caustic solution for 5 minutes at 200 F, then with the TCA
solution for 1 minute at ambient temperature, followed by
c re-contact with the caustic solution for 5 minutes. The etched
substrate accepted uniform electroless and electrolytic plates.
Controls 7 to 9
In tests on Vydyne where contact with the alkali
hydroxide solution was used for 5 or 10 minutes contact,
failues occurred in the organic solutions and conditions
identified below.
Control Test Solution Nature of
(Conc, Temp, Contact Time) Failure
7 dichloropropanol(l5% v/v, Massive blistering
; 15 150F, 1.5 min.) in cycle test
8 do Blistered severely
in reverse current
: 9 Formic acid (45% v/v, Blistered in pre-
R.T., 1 min.) plate
,.:'
30 l
113-1 1 16