U.S. patent number 3,615,732 [Application Number 04/752,165] was granted by the patent office on 1971-10-26 for electroless copper plating.
This patent grant is currently assigned to Shipley Company, Inc.. Invention is credited to Oleh B. Dutkewych, Michael Gulla, Charles R. Shipley, Jr., Lucia H. Shipley.
United States Patent |
3,615,732 |
Shipley, Jr. , et
al. |
October 26, 1971 |
ELECTROLESS COPPER PLATING
Abstract
An electroless copper plating solution comprising a source of
cupric ions, hydroxyl radicals, formaldehyde or a formaldehyde
precursor preferably paraformaldehyde, and a complexing agent for
copper, said solution characterized by the addition of a hydrogen
inclusion retarding agent and at least one member selected from the
group consisting of a formaldehyde addition agent and a salt of a
Group VIII metal of the Periodic Chart of the Elements. The
electroless copper plating solution is capable of providing a rapid
rate of copper deposition dependent upon the selection of the
complexing agent without sacrifice in tensile properties of the
copper deposit. The copper plate deposited from the electroless
solution of this invention is distinguishable from prior art
electroless copper deposits by substantially improved bending or
ductility properties.
Inventors: |
Shipley, Jr.; Charles R.
(Newton, MA), Shipley; Lucia H. (Newton, MA), Gulla;
Michael (Newton, MA), Dutkewych; Oleh B. (Medfield,
MA) |
Assignee: |
Shipley Company, Inc. (Newton,
MA)
|
Family
ID: |
25025176 |
Appl.
No.: |
04/752,165 |
Filed: |
August 13, 1968 |
Current U.S.
Class: |
106/1.23 |
Current CPC
Class: |
C23C
18/405 (20130101) |
Current International
Class: |
C23C
18/40 (20060101); C23C 18/31 (20060101); C23c
003/02 () |
Field of
Search: |
;106/1
;117/13E,130,47R,35S,213,227 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hayes; Lorenzo B.
Claims
We claim:
1. In an electroless copper plating solution comprising a source of
cupric ions, hydroxyl radicals, formaldehyde and sufficient
complexing agent to render said cupric ions soluble in alkaline
solution, the improvement comprising an additive in solution of at
least one hydrogen inclusion retarding agent in an amount of from 1
to 1,000 parts per million parts of solution, said hydrogen
inclusion retarding agent being selected from the group consisting
of solution soluble compounds of alkali and alkaline earth metal
cyanides and nitriles, vanadium, molybdenum, niobium, tungsten,
rhodium, arsenic, antimony, bismuth, rare earths of the actinium
series, rare earths of the lanthanum series and mixtures thereof;
and at least one solution soluble member selected from the group
consisting of a formaldehyde addition agent in an amount of from
0.1 moles times the moles of formaldehyde to 1 times the moles of
formaldehyde, said agent being selected from the group consisting
of alkali metal sulfites, bisulfites, and phosphites; and a salt of
a member selected from the group of iron, nickel, and platinum in
an amount of from 5 to 2500 parts per million parts of solution,
said salt having an anion noninterfering with said electroless
copper solution. 2. The copper plating solution of claim 1 having
as additive at least one hydrogen inclusion retarding agent and
a
salt of a Group VIII metal. 3. The copper plating solution of claim
1 having as additive at least one hydrogen inclusion retarding
agent and a
formaldehyde addition agent. 4. The copper plating solution of
claim 1 having as additive at least one hydrogen inclusion
retarding agent, a salt
of a Group VIII metal and a formaldehyde addition agent. 5. The
copper plating solution of claim 1 having the following
formulation:
6. The copper plating solution of claim 1 where the cyanide
compound is sodium
cyanide. 7. The copper plating solution of claim 1 where the
hydrogen
inclusion retarding agent is As.sub.2 O.sub.3. 8. The copper
plating solution of claim 1 where the hydrogen inclusion retarding
agent is V.sub.2 O.sub.5. 9. In an electroless copper solution
comprising a source of cupric ions, hydroxyl radicals, formaldehyde
and sufficient complexing agent to render said cupric ions soluble
in alkaline solution, the improvement comprising an additive in the
solution comprising at least one hydrogen inclusion retarding agent
and at least one solution soluble member selected from the group
consisting of a formaldehyde addition agent and a salt of a Group
VIII metal of the Periodic Chart of the Elements; said hydrogen
inclusion retarding agent, and Group VIII metal salt being present
in solution in minor amounts sufficient to improve ductility of a
copper deposit and said formaldehyde addition agent being present
in an amount of from 0.1 moles per mole of formaldehyde to that
amount that
restricts copper deposition. 10. The copper plating solution of
claim 9 having as additive at least one hydrogen inclusion
retarding agent, and
the Group VIII metal salt. 11. The copper plating solution of claim
9 having as additive at least one hydrogen inclusion retarding
agent and the
formaldehyde addition agent. 12. The copper plating solution of
claim 9 having as additive the hydrogen inclusion retarding agent,
the
formaldehyde addition agent and the salt of the Group VIII metal.
13. The copper plating solution of claim 9 where the salt of the
Group VIII metal is selected from the group consisting of
NiSO.sub.4, Fe.sub.2 (SO.sub.4).sub.3 and H.sub.2 PtCl.sub.6. 14.
The copper solution of claim 9 where the formaldehyde addition
agent is selected from the group consisting of Na.sub.2 SO.sub.3,
NaHSO.sub.3, and Na.sub.2 HPO.sub.3.
5H.sub.2 O. 15. The copper plating solution of claim 9 where the
hydrogen
inclusion retarding agent is NaCN. 16. The copper plating solution
of claim 9 where the hydrogen inclusion retarding agent is selected
from the group consisting of V.sub.2 O.sub.5 and As.sub.2 O.sub.3.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a metal depositing composition and more
particularly to an electroless copper plating solution capable of
providing electroless copper deposit of improved bending or
ductility properties.
2. Description of the Prior Art
Electroless copper deposition refers to the chemical plating of
copper over clean catalytically active surfaces by chemical
reduction in the absence of an external electric current. Such
processes and compositions useful therefor are known and are in
substantial commercial use. They are disclosed in a number of prior
art patents, for example, U.S. Pat. Nos. 2,938,805; 3,011,920;
3,3l0,430 and 3,383,224.
Known electroless copper deposition solutions generally comprise
four ingredients dissolved in water. They are (1) a source of
cupric ions, usually a copper salt, such as copper sulfate, (2) a
reducing agent such as formaldehyde, or preferably a formaldehyde
precursor such as paraformaldehyde, (3) free hydroxide, generally
an alkali metal hydroxide and usually sodium hydroxide, sufficient
to provide the required alkaline solution in which said
compositions are effective, and (4) a complexing agent for copper
sufficient to prevent its precipitation in alkaline solution. A
large number of suitable complexing agents are known and described
in the above-cited patents, and also in U.S. Pat. Nos. 2,874,072;
3,075,856; 3,119,709; 3,075,855, and 3,329,512 all incorporated
herein by reference. Known electroless plating solutions of the
above type usually provide a plate which, if mechanically dense and
strong, is somewhat brittle such that it can withstand only limited
bending or thermal stress without fracture. This is not a
substantial disadvantage where the electroless plate is of the
order of millionths of an inch in thickness and is overplated with
ductile electrolytic copper. However, where the entire desired
thickness, typically 1 to 3 mils in an electrical application, is
provided by electroless plating, limited ductility is a serious
limitation.
One means for improving the tensile properties of an electroless
copper deposit while simultaneously improving brightness and other
appearance properties is described in U.S. Pat. No. 3,475,186 filed
Jan. 5, 1968, and incorporated herein by reference. Improved
properties are obtained by the addition of an organic silicon
compound to an electroless copper solution where silicon is
believed to be the active agent. A major advantage of this system
is that the rate of copper deposition does not substantially affect
tensile properties. The manner in which the silicon compound
improves tensile properties is not fully understood but it is
believed to be due, at least in part, to a surface effect resulting
in deposition of a smoother deposit having fewer structural
defects.
An improved method for improving tensile properties is set forth in
copending U.S. Pat. application Ser. No. 752,250 filed concurrently
herewith. In a preferred embodiment, a combination of additives
comprising a silicon compound, a formaldehyde addition agent, and a
salt of a Group VIII metal of the Periodic Chart of the Elements is
added to the electroless copper bath. Electroless copper deposited
from said bath is characterized by substantially improved tensile
properties resulting from a synergistic reaction between the
additives and possesses increased tensile properties, improved
brightness and substantially improved solderability.
An additional method for improving the bending or tensile
properties of an electroless copper plate using a different
mechanism is described in U.S. Pat. No. 3,310,430, which discloses
the addition to a copper plating solution of a water soluble
compound of cyanide, vanadium, molybdenum, niobium, tungsten,
arsenic, antimony, bismuth, rare earths of the actinium series and
rare earths of the lanthanum series. Certain members of the group,
especially the vanadium compounds, provide significantly improved
bending characteristics. The reason for this is not fully
understood but it is stated in the patent that the agents poison
the catalytic surface so as to promote formation and release of
hydrogen at the catalytic surface, thereby inhibiting the inclusion
in the deposit as it forms. It has been found that where a
complexing agent or a bath formulation is used permitting rapid
deposition of copper with rapid evolution of hydrogen gas at the
surface, the improved ductility or bending characteristics are
frequently sacrificed or lost.
STATEMENT OF THE INVENTION
The subject invention is an improvement over that described in the
above-noted U.S. Pat. No. 3,310,430 in that it avoids the
disadvantages noted above and provides an electroless copper
solution capable of depositing an electroless copper plate having
substantially improved bending or tensile properties regardless of
the rate of copper deposition and the complexing agent used. The
copper solution is characterized by the addition of a hydrogen
inclusion retarding agent and at least one member selected from the
group consisting of a formaldehyde addition agent, and a salt of a
Group VIII metal of the Periodic Chart of the Elements. In addition
to an improvement in bending or tensile properties, electroless
copper deposits from the solutions of this invention provide the
further advantages of excellent laydown properties, and excellent
solderability along with improvement in smoothness, brightness and
overall appearance.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A typical electroless copper solution in accordance with the
invention will have additives in the following concentration
ranges:
Preferred
__________________________________________________________________________
Copper salt 0.002 moles 0.02 to 0.12 to saturation moles
Formaldehyde 0.05 to 3.5 moles 0.1 to 1 moles Complexing agent
minimum necessary to maintain copper in 1 to 3 times solution the
moles of cupric ion Free hydroxide Sufficient to 0.1 to 0.8 provide
moles pH 10 or greater Hydrogen inclusion 1 to 1000 p.p.m. 5 to 250
retarding agent p.p.m. Formaldehyde addi- up to that 0.1 to 1 tion
agent amount that times the restricts moles of deposition
formaldehyde Group VIII metal salt 5 to 2500 p.p.m. 30 to 1000
p.p.m. Water to 1 liter of solution
__________________________________________________________________________
It should be understood that the above concentration ranges are
preferred but not critical. Variations in the ranges are possible
without varying from the scope of the invention. In most cases,
additives may be added in any amount up to that amount that poisons
the solution and prevents deposition.
In the above formulations, any water soluble copper salt heretofore
used for preparing electroless copper deposition solutions may be
used. For example, certain of the halides, nitrate, acetate,
sulfate, and other organic and inorganic acid salts of copper are
generally suitable as is known in the art. Copper sulfate is
preferred.
Suitable complexing agents for the copper ions are well known in
the art and include Rochelle salts, the sodium salts (mono-, di-,
tri-, and tetrasodium salts) of ethylenediaminetetraacetic acid,
nitrilotriacetic acid and its alkali metal salts, triethanolamine,
modified ethylenediaminetetraacetic acids such as
N-hydroxyethylenediaminetriacetate, hydroxyalkyl substituted
dialkylene triamines such as pentahydroxypropyldiethylenetriamine,
sodium salicylate, and sodium tartrate. Other complexing agents for
copper ions are disclosed in U.S. Pat. Nos. 2,996,408; 3,075,855;
3,075,856 and 2,938,805.
The preferred class of complexing agents are those described in
U.S. Pat. No. 3,329,512 noted above. They include hydroxyalkyl
substituted tertiary amines corresponding to one of the following
structures: ##SPC1##
where R is an alkyl group having from two to four carbon atoms, R'
is a lower alkylene radical and n is a positive integer. Examples
of these complexing agents include tetrahydroxypropyl ethylene
diamine, pentahydroxypropyl diethylene triamine,
trihydroxypropylamine (tripropanolamine), trihydroxypropyl
hydroxyethyl ethylene diamine, etc. As disclosed in said patent,
the aforesaid amines are preferably used in small amounts in
combination with other complexing agents and with certain polymers
dispersed in solution such as cellulose ethers, hydroxyethyl
starch, polyvinyl alcohol, polyvinylpyrrolidone, peptones, gelatin,
polyamides and polyacrylamides.
The rate of copper deposition is, to some extent, dependent upon
the selection of the complexing agent. Complexing agents such as
pentahydroxypropyldiethylenetriamine provide a rapid rate of copper
deposition, usually in excess of 1.0 mils per hour. Though the
copper solutions of this invention provide copper deposits from
solutions containing any of the known complexing agents for copper
ions, they are particularly well adapted for copper solution having
complexing agents that provide a rapid rate of copper
deposition.
The hydrogen inclusion retarding agent is of the same class
disclosed in the above-noted U.S. Pat. No. 3,310,430 and includes
simple and complex compounds which comprise one or more of cyanide,
vanadium, molybdenum, niobium, tungsten, rhenium, arsenic,
antimony, bismuth, actinium, lanthanum, rare earths of both the
lanthanum and actinium series and mixtures of the foregoing.
Preferred are those compounds which consist of or comprise elements
of the type described which have at least two oxidation states. In
this preferred group are compounds comprising vanadium, niobium,
molybdenum, tungsten, rhenium, arsenic, antimony, bismuth, cerium,
praseodymium, neodymium, samarium, europium, terbium, uranium, and
mixtures of the foregoing. These elements are preferably added to
the electroless copper plating baths in a form such that the
element is at its most stable valence state. Vanadium and cyanide
are the most preferred hydrogen inclusion retarding agents. Where
cyanide is selected as the hydrogen inclusion retarding agent, it
may appear twice in the formulation dependent upon the selection of
the remaining additives.
The hydrogen inclusion retarding agent is added to the bath,
preferably as a soluble salt. For example, molybdenum may be
supplied as molybdic trioxide as well as water soluble organic and
inorganic acid salts of molybdenum, as for example alkali and
alkaline earth metal, or ammonium molybdates. Suitable sources of
tungsten, molybdenum, rhenium, and arsenic are the oxides of such
elements, as well as organic and inorganic acid water soluble salts
of such elements, e.g., the tungstates, vanadates, arsenates, and
rhenates of the metals of Groups I-A and II-A of the Periodic Chart
of the Elements, and ammonium. Preferred for use are the sodium,
potassium, and ammonium salts. Sources of antimony, bismuth,
lanthanum, actinium, and rare earths are the oxides of such
elements and water soluble organic and inorganic acid salts of such
elements, including the sulfates, nitrates, halides, acetates, and
the like. The function of the hydrogen inclusion retarding agent is
not fully understood, but it is reported that it tends to poison
the catalytic surface so as to promote the formation and release of
hydrogen gas at the catalytic surface on which copper is depositing
electrolessly, thereby inhibiting the inclusion of hydrogen in the
deposit as it forms.
The formaldehyde addition agent for purposes of this invention is
one that may be added to solution in amounts sufficient to undergo
reaction with formaldehyde to form a relatively unstable
formaldehyde adduct without poisoning the solution. Reactions of
this nature and formaldehyde addition agents are well known in the
art and described in various publications such as "Formaldehyde" J.
Frederick Walker, Reinhold Publishing Company, Third Edition 1964,
pages 219 to 221, included herein by reference. Preferred
formaldehyde addition agents include alkali and alkaline earth
metal sulfites, bisulfites, and phosphites of a metal cation that
does not codeposit with copper and preferably, an alkali metal
cation. Preferred formaldehyde addition agents are sodium sulfite,
sodium bisulfite, potassium sulfite and sodium phosphite.
The formaldehyde addition agent and formaldehyde or preferably,
paraformaldehyde are reacted with each other to form the adduct
prior to addition to the remaining components of the copper
solution.
The Group VIII metal salts are preferably water soluble inorganic
salts of iron, cobalt, nickel, ruthenium, rhodium, palladium,
osmium, iridium, and platinum; salts of nickel, iron and platinum
being most preferred and salts of palladium being least preferred
due to solution stability problems caused by palladium. Suitable
salts include phosphates, nitrates, halides, and acetates, of the
above metals.
The cyanide compound is a water soluble compound such as an alkali
metal cyanide, such as sodium cyanide, potassium cyanide, sodium
nitrile, potassium nitrile, organic nitriles such as
alphahydroxynitrile, e.g., glycolnitrile and lactonitrile, and
dinitriles, such as iminodiacetonitrile and
3,3'-iminodipropionitrile.
A wetting agent may be added to solution in accordance with art
recognized procedure.
The bath may be used at widely varying temperatures, e.g., at least
room temperature and preferably up to 140.degree. F. As temperature
is increased, it is customary to find an increase in the rate of
plating. Temperature is not highly critical and within the usual
operating ranges, excellent, bright deposits of electroless copper
having excellent ductility properties are obtained. Preferably, the
bath is used without agitation.
In using the electroless copper solution to plate metal, the
surface to be plated should be catalytically active and free of
grease and contaminating material. Where a nonmetallic surface is
to be plated, the surface area to receive the deposit must first be
sensitized to render it catalytically active as by the well-known
treatment with an acidic aqueous solution of stannous chloride
followed by treatment with a dilute aqueous acidic solution of
palladium chloride. Alternatively, extremely good sensitization of
nonmetallic surfaces is achieved by contact with an acidic
colloidal formulation formed by the admixture of stannous chloride
and a precious metal chloride, preferably palladium chloride, the
stannous chloride being present in stoichiometric excess based upon
the amount of precious metal chloride.
The invention will be better understood by reference to the
following examples where all parts were plated using the following
procedure:
a. Cut a phenolic substrate to a size of 2" .times. 2."
b. Scrub part clean using an abrasive cleaner.
c. Rinse in cold water.
d. Immerse in a solution of a wetting agent identified as Shipley
Conditioner 1159 at room temperature for 1 to 3 minutes.
e. Rinse in cold water.
f. Immerse in a colloidal stannic acid-palladium catalyst
(identified as Cuposit Catalyst 6F) maintained at room temperature
for 1 to 5 minutes.
g. Rinse in cold water.
h. Immerse in a Cuposit Accelerator 19 or a mild perchloric acid
solution maintained at room temperature for 3 to 10 minutes.
i. Rinse in cold water.
j. Immerse in electroless copper solution maintained at between 110
and 130.degree. F. for a period sufficient to provide a deposit of
desired thickness not to exceed 3 hours.
k. Dry parts and analyze the deposit for appearance and ductility.
Ductility is determined by peeling a copper deposit from the
substrate and bending it through 180.degree. F. in one direction,
creasing at the fold, then returning it to its original position
with pressing along the crease to flatten it. This cycle
constitutes one bend. The procedure is repeated until the sample
breaks at the crease. A sample unable to withstand at least
one-half bend is considered brittle.
---------------------------------------------------------------------------
EXAMPLES 1-20
CuSO.sub.4.sup.. 5H.sub.2 O 8.0 g. Paraformaldehyde 7.5 g. NaOH
(25% solution by wt.) 50.0 ml. Tetrahydroxypropylethylene amine
12.0 g. Triisopropanoldiamine 2.0 g. Water to 1 l. of solution
__________________________________________________________________________
The above formulation, with various additives, is used to deposit
electroless copper. Additive compositions and deposit properties
are set forth in the following table: ##SPC2##
In the above examples, a deposit was considered poor if it was dark
in color and powdery. A fair deposit was one lighter in color
though powdery in appearance. A good deposit was one having a fine
grained metallic copper appearance.
The improvements in tensile properties using the electroless copper
solutions of the present invention are readily apparent by
reference by the above examples. Examples 2 to 4 illustrate copper
solutions containing only a hydrogen inclusion retarding agent.
Examples 5 to 9 illustrate copper solutions containing only a Group
VIII metal salt. Examples 10 to 12 illustrate copper solutions
containing only a formaldehyde addition agent. Using any of these
single additives alone, little or no improvement in tensile
properties is obtained. In examples 13 to 17, there is represented
combinations of two additives resulting in minor improvements in
tensile properties. Examples 18 to 20 represent deposits formed
from solutions of the subject invention and illustrate a minimum of
a 300 percent increase in ductility as measured by bending. It
should be noted that the base formulation is one typically
providing brittle deposits. Greater increases in tensile properties
are possible with other copper solutions as will be illustrated
below.
---------------------------------------------------------------------------
EXAMPLES 21-25
CuSO.sub.4.sup.. 5H.sub.2 O 8.0 g. Paraformaldehyde 7.5 g. NaOH(25%
solution) 50.0 ml. Ethylenediaminetetraacetic acid 30.0 g. Water to
1 l. of solution
__________________________________________________________________________
The above formulation, with various additives, is used to deposit
electroless copper. Additive composition and deposit properties are
set forth in the following table: ##SPC3##
Example 25 of the above represents a substantial improvement in
tensile properties.
---------------------------------------------------------------------------
EXAMPLES 26-29
CuSO.sub.4.sup.. 5H.sub.2 O 8.0 g. Formaldehyde 7.5 g. NaOH(25%
solution) 50.0 ml. Sodium/potassium tartrate 40.0 g. As.sub.2
O.sub.3 10 p.p.m. Water to 1 l. of solution
__________________________________________________________________________
The above formulation, with various additives, is used to deposit
electroless copper. Additive compositions and deposit properties
are set forth in the following table: ##SPC4##
In the above, example 26 represents a poor control sample because
of the thinness of the deposit. A thicker deposit would probably be
brittle. However, the combination of the hydrogen inclusion
retarding agent, Group VIII metal salt and formaldehyde addition
agent provides deposits substantially improved over that of the
control capable of withstanding in excess of five bends without
fracturing.
Copper solutions of this invention find utility for all purposes
for which electroless copper solutions have heretofore been used
including both decorative and industrial applications. They are
especially useful for the formation of printed circuit boards where
the deposit acts as a ductile conductor both in a circuit pattern
and on the walls of through-holes. The formation of a printed
circuit board having conductive through-holes is illustrated in the
following example:
EXAMPLE 30
a. Sandblast one side of a phenolic substrate leaving the second
surface smooth.
b. Drill through-holes at desired locations.
c. Silk screen a reverse image of a printed circuit pattern onto
the roughened surface of the phenolic substrate using an epoxy
resin resist.
d. Immerse in a colloidal palladium sensitizing solution maintained
at room temperature for a period of 5 minutes.
e. Immerse in a stripping solution comprising 10 grams of copper
chloride, 100 grams of 37 percent hydrochloric acid, and water to 1
liter. Maintain stripping solution at room temperature and immerse
part in solution for 6 minutes.
f. Deposit electroless copper of example 25 with copper deposition
taking place on the walls of the through-holes and on the roughened
surfaces in an image pattern. No copper deposition takes place on
the epoxy resist or on the smooth side of the plastic laminate.
The mechanism by which copper deposits from the solution of this
invention differs from that of the above referenced U.S. Pat. No.
3,310,430 where hydrogen inclusion retarding agents alone are used
to improve ductility. Though neither mechanism is fully understood,
a different mechanism is suggested by the observation that the
Group VIII metal cation codeposits with copper, to some extent, in
the absence of a hydrogen inclusion retarding agent but
codeposition is lessened when a hydrogen inclusion retarding agent
is in solution. This is shown by the following examples:
---------------------------------------------------------------------------
EXAMPLES 31-32
31 32
__________________________________________________________________________
CuSO.sub.4 .sup.. 5H.sub.2 O 8.0 8.0 Paraformaldehyde (g.) 7.5 7.5
NaOH (25% solution by wt.) (ml.) 50.0 50.0 tetrahydroxypropyl
ethylene diamine (g.) 15.0 15.0 NaHSO.sub.3 (g.) 20.0 20.0 V.sub.2
O.sub.5 (p.p.m.) 20 NiSO.sub.4 (p.p.m.) 300 300
__________________________________________________________________________
The copper deposits of the above examples were analyzed. In example
31 containing both vanadium and nickel compounds in solution, only
0.00088 percent nickel was found in the deposit. Omission of the
vanadium compound in example 32 results in a copper deposit
containing 0.100 percent nickel. This indicates that the vanadium
somehow retarded the codeposition of nickel.
It should be understood that various changes may be made in the
embodiments described above without departing from the spirit and
scope of the invention as defined by the following claims:
* * * * *