Note: Descriptions are shown in the official language in which they were submitted.
This ~nvention relates to the fabrication o~
copper in the ~orm of elongate bodies and especially but
not exclusively to the ~abrication o~ elongate bodies
o~ copper of electric conductor gradeJ which ~or avoidance
o~ uncertain~y can be taken to mean copper with a
conductivi~y o~ at least 101% I.A.C.S. When the copper
contain~ impuriti~s of the usual kind, this corresponds
to a total impurity level (counting oxygen as an impurity)
in the re~ion o~ 0,05~ or below.
Copper o~ this quality is normally produced by
electrolytic refining as flat9 approximately rectangular
cathodes, and the conventional fabricatlon process
involves melting the cathodes, casting (either continuously
or discretel~) into bars and hot-working (by swaging,
rolling, extrusion or more than one o~ these processes)
to elongate shape. In most cases cold drawing and/or
cold rolling ~ollows.
It has long been recognised that this process
involves the provision o~ much expensive equipment and
the use o~ large amounts o~ energy merely to raise the
temperature of the copper to melt it and sub~equently to
maintain a suitable hot-working temperature, and attempts
have been made to pr.ovide a low-temperature ~abrication
process ~or the production of elongate products from
unmelted cathode copper.
Most such attempts have been based on modification
of the electrolytic refining process to form an elongate
product directly~ Though technically possible ~or some
- 2 --
products, thi~ has 9~ ~ar proYed lmpr~ctieable and/or
uneconomic ~or the manu~a~ture o~ eleotric conductcr~
(e~cept thin ~oil3) becau~e the area o~ th~ electrodes i~
not e~ficiently utili~ed i~ it~ component part~ (e.g. the
turns o~ a spiral) are ~pac.ed gufficlentl~ to avoid rl~k
of adhesion, irregular cro~-3ection, a~d con~equent
fracture i~ ~ub~equent proce~3ing, and the additi~es
required in the electrolytic bath to control ~he shape of
the product may have a deleteriou~ e~ect on its
electr~cal condu¢tivity and~or the rate o~ depo~ition~
Anether ~uch attemptJ wh~ ch reached commercial u~e ln
the United Stat0~ of America on a mode~t ~cale in the
1930l9 or thereabollt~9 but ha~ ~ince fallen into disu~e~
produced a product known a~ "coalesoed Gopperl~. The
coalesced copper proee~ wa~ in a broad 3en~e of the
word, a ~powder metallurgic~ proce3~ as lt lnvolved the
del~berats produ~tion o~ brittle cathodes whloh ware
broken up into fragment3 whi~h might be as large as
several centimetr.es 1n each of their ma~or dlmen3~0n~ and
5 nn~ thick. ~he~e ~ragments wera compre~ed lnto
briquette~, ¢oale~ced by heating ~or a substantial period
under relluc~ ondition~ Qt around 900C to effect
3~rface d0~xidatlon, sane other ~ icatlon and grain
grGwth, and ~ub equently hot-e~ctruded to gi~e a solid
pro*uct of electric ¢ondllctor grade.
We have rec0ntly discovered that the heat-treatment
and c oale~en¢e step o~ thl3 known proces~ was nolther
ns¢es~ary nor bene~i~ial and th~t fabricated productQ with
-- 5 --
... , .. _ _ . ,, ., ... . , _,,, . ... ,. ., ... . . .. _, .. . .
~8l~8~
superior properties can be obtained without surface-deoxidation
provide~ that the metal is never heated to the extent of
allowing significant amounts of any impuri-ty present to
dissolve in the copper, and have therefore proposed in the
complete specification of our British Patent No. 1543440, a
method of making an elongate body of copper of electric
conductor grade comprising: electrodepositing copper in the
form of brittle cathodes; breaking the cathodes into ~ragments
with a mean specific surface area in the approximate range from
10 25 - 1,000 mm /g; feeding these fragments as such and without
any high temperature treatment Eor purification or grain growth
to a continuously acting friction-effected extrusion machine
and by means of that machine working the fragments under
pressure sufficiently to consolidate and bond the fragments
into a continuous elongate body.
Brittle cathodes are likely to be of higher porosity
than cathodes of conventional ductility and may therefore
occlude greater amounts of electrolyte and possibly anode
slime, leading in some cases to higher impurity levels
20 (especially for antimony, arsenic and sulphur) than for
conventional coppers; such a higher impurity level may not in
every circumstance be completely compensated by the control of
impur.ity dissolution and is likely to result in a product with
a lower conductivity than might have been obtained from a feed
of ductile copper particles.
In accordance with the invention, a method of
fabricating copper into an elongate product comprises:-
(i) Electrodepositing copper onto an electrode having
a plurality of cathode sur:Eaces substantially
separated from one another by insulating material
until the areas of copper deposited on the
-- 4 --
individual cathode surfaces cohere across the
boun~aries o~ those areas in the form of a shee-t;
(ii) Stripping the deposited copper from the electrode;
(iii) Subse~uently fracturing the sheet in areas of
weakness corresponding to at least some of those
boun~aries to form particles of copper and
(iv) Extruding those particles by a continuous
friction-effected extrusion process to form an
elongate product.
The particles preferably have volumes in the
approximate range from 1 mm to 0.1 dm and par-ticles of
these dimensions are hereaf-ter called "granules"; granules
produced by the present invention wlll usually have at least one
major dimension (their thickness) not greater than 10 mm but
thicker granules could be produced if desired.
The electrode may be of any suitable conductive
material; for conventional acid copper sulphate baths either
titanium, stainless steel, or copper will usually be preferred;
if copper is used, a parting agent will usually he applied -to
it. Normally the cathode areas will all be parts of the major
surace(s) of an initially continuous sheet.
Normally electrodeposition will be part of an
electro-refining process, and the conditions adopted
are preferably such that ductile copper is deposited,
standard refining conditions can be, and are preferably,
-- 5 --
~-~0~
ueed .
The separation oR 1~h~ shset lnto distinct sathode
area~ by in~la~in~ materlal may bs e~ected in variou~
waysO In particular the ln~ulating material ma~r be
durable 30 a~ to ~urvlve ~tripping Or the copper and
repaated uqe or~ i~ oheap enou~h, it may be di~po~able
a~d be replaced a~tor each u9eo ~he pre~erred durable
in3ulating material i~ an a~odic o:~cide layer f`orm0d on an
elsctrode Or titanium ( or o tiher sui~able motal ) ,.
AlternR~ives include variouq organie in~ulating materlal~
prote¢ted ~rom mechani¢al damaga bg being re~essed into
shallow grooves pro~lded in l~he surf`ace o~ the electrode;
suitable organic material~ ~or u8e in ~hi 9 way includs
epoxy resln~ (thermo~ettine~ or coldsetting)J ~bbers
(pre~erably vulcani~ed in itu) " and ethylene-vinyl
acetate copolymers (thermopla~tic)O I~ po~abl0
insulating material i!~l ~eferrea, thi~ wlll u~ually be an
organic materlal applied as a ~ a~e layer on a plain
matal ~ur~a~eO ~he ~ ace layer may be a ~oating applied
~roro a ~luid ~ta~e9 or it may be a prefor~d por~orate
sheet prsferably se¢urely bonded to ~he metal Or the
eleotrode b~ ~el~ adhesion or by a separate adhe ~iYe but
alte~nativ31~ ecurely Glamped to the metal ~o a~ to
a~tabli3h a ~ub~tantiall~ ~luid-tight eontaotO Suita~le
material~ include roorn-temperature vulcani3ing sllicone
rubber con~:~o~i~ions applied in th~ ~ condition~ and
poly~rln~l chloride applied in ~heet ~ormO
To enqure the produotion o~ a unl~orm p~odu¢t tha
oathodic area~ ar3 pre~erably allke in ~hape and ~ize~ or
6-
.. . . . .... . .. .... . .
.: ,
~ 8 ~
at least are o~ only a small number of di~erent hapes
and/or sizes. We pre~er to use a regular pattern of
squares, hexagons, rectangular strips~ or other polygons
spaced by insulating strips of uniform width, except
when pre~ormed insulating sheets are used, when it may
be pre~era~le to use circular openingsJ poss~bly of two
di~erent sizes to secure better space utilisation.
Rectangular strips may be as long as the electrode
itsel~, lf desiredO Currently we pre~er that long strips
should not be wider than 10 mm, or at the most 25 mm,
and that more compact shapes should not exceed 100 mm
square. Particular friction-ef~ected extrusion machines~
such as the prototypes currently in use~ may require
smaller particles than this.
The cathodic areas will usually need to be
spaced by a ~ew millimetres to ensure clear demarcation;
and we have ~ound that ror shest ~ormation the deposit
thickness will usually need to be several times the
spacing.
A~ter removal ~rom the electrolytic cell, the
electrode with the deposited copper on lt will normally
be washed to remove electrolyte, ~or convenience in
subsequent handling. The copper may then be strippe~
broadly in the same way as copper start~ng sheets are
stripped from blanks, that is by a blade ~orced along
the electrode at a position slightly spaced ~rom the
-- 7 --
~ 8 ~
electrode sur~ace and possibly (where applicable) by
tearing after a corner or end has been separated. The
continuous sheet so formed may be broken up ~ubsequently
by any suitable type of mill~ u~u~lly one operating by
impact and/or bendlng. Jaw mills, tooth millsg ball
mills, ha~mer mills~ and tumblers may all be used.
A~ter stripping, and be~ore and/or a~ter
~ragmentakioll, the particulate copper is pre~erably
washed again to minimise electrolyte contamination, and
afterwards preferably dried. The copper is preferably
screened to elim~nate any oversize particles (which may
be returned to the fragmentation mill).
Continuous ~riction-effected extrusion processes,
such as those known by the proprietary names "Conform",
"Linex" and "Extrolling", operate without a closed
billet Qhamber and the metal, instead o~ being ~orced
into the extrusion die by a ram or by fluid pressure,
is gripped by a member or members o~ the enclosure that
are advanced towards the die mouthl where it upsets and
extrudes thDough the die. (A fuller description o~ the
Con~orm and Linex processes will be ~ound in Wire Journal~
April 1976, pp 64-69; the Con~orm process is the sub~ect
o~ British Patents 1370894 and 14~4201 and the Line~
process the subject o~ British Patent 1488445).
Pre~erably the granules or other particles of
copper are fed as such, without any pre-compaction9 to the
8~
friction-effected e~rusion operation and are caused to
cohore by the ex~rusion proceqs it~el~; pro~erably alqo
the temperature o~ the copper at no time e~ceads 700C~ so
a~ to avoid any ~ub~tantial los~ of elactrical conductivity
by di~solution o~ impurities that may be pre~ent in
undissolved ~orm.
Optionally ths particles may be preheated be~ore
e~trusion, to reduce the e~truslon pres ure requi~ed.
Preferably the prehoating temperature doe~ not exceed
450C, as otherwise there may be a risk that during the
e~trusion proce~s a temperature Q~ 700C may be exceeded
as a result o~ adiabatic he~ating. A reducing or neutral
atmosphere, or the use o~ vacuum, may be desirable i~
preheating i3 uqed; cracked ammonia and ~team (preferabl~
~ree of air in both case3) are suitable.
I~ de~ired~ the extrusion tools ma~ be pre-heated~
at lsa8t ini~ially. ~he 3xposure time is ~o short that a
protective atmosphere i~ not consid3red necessar~ in
normal ca~e~. ~nles~ a porous product ls acceptable9 the
extrusion ratio is pre~erably at lea~t 8:1, and reductions
of around 9:1 to 20:1 are pref~erredO In s~e ca~e~ it may
be bene~icial to e~trude two or more product~ s1multan
eou~ly using a dual or multiple dia. E~trusion may be
a~ial~ iOe. in the same direction ~ the material to ba
o~truded approaches the dle, or it rnay be at right angle~,
or another angle, to the a~cial direction.
_ g .
~ , . _ , _ .... . . . . .. . .. , . .. . _ . , .. ... .. . . .. .. . . . . . .. . .. ....... .. . . . . . . . . . ...... _ _ ..
`~
The extruded product may be haat-treated, i~ desired,
to homogeni~e it~q ~trueture and/or modi~ machanical
properties; pre~erQbly heat-treatment ls below 7OOC to
avoid si~ni~icant grain growth and dis~qolution o~
impuritie~
me elongate product will ofte.n be ~wire rod~, that
is round rod suitable ~or drawing into wire; alternati~ely
it may be a finish3d product Or rectangular or other
special qection9 includin~ hollow soctions which can be
produced using bridge or porthole dies. Further it may be
intermodiate (3a~ a square or re~tangular rod) ~or u3e as
a ~eed to a qecond continuou~ friction-e~ected extru~ion
procesq, a~d in ~qome ca~eq wire may be e~truded directly.
In the accompan~ing drawings each o~ ~igure~q 1-6 is a
diagrammatic elevation (not to ~cale) o~ a di~erent
electrode for use in the first step of the method o~ the
invention.
The electrode o~ figure 1 comprises a stout metal
sheet having an uppor area 1 that iq bare and .~erves ~or
makin~ electrical connections, an intermediate area 2 that
i~ coated with insulating matarlal and in use extends
partly in th~ elect~olyte and partly in ths air above i~,
and a main area 3 qer~ing ~or raception o~ electrodspoqited
coppar. The edge~ 49494 o~ the main area ~r~ coated with
insulating materi~l and both it3 ma~or sur.~aces ara ~ub-
di~ided by diagonal strip~ ~,6 of i~ulating material into
a multiplicity of diamo~d-~haped cathode 9urfaces 7.
Triangular or other undersize area9 8 ad~oining the edge3
of the 3~rip may be coatad ir uni~ormity o~ particl0 i~
re~uired,
- 10 -
..... , .. ,,--. . ...
2 ~
The electrode of figure 2 differs only in that ~he
insulating strips 9~10 on ~he main area ~ run vertically
and horizontall~. This ensures uniformity of particle
sizes withou~ loss of volume efficiency, but may produce
a slightly less pure deposit as ~he horizontal upper edges
of the initial copper deposits may tend to collect some
particulate impurities ("sllmes").
The electrode o~ ~igure 3 has vertical in~ulating
strips 9 onl~, and consequently has long narrow bare areas
11 for deposition o~ copper strips. Horizontal strips 10
could be used alone, as seen in figure 4, but this
arrangement would also tend to produce a less pure product.
m e electrodes o~ figures 5 and 6 have their main
areas 3 coated all over apart from circular areas 12~13,
of one size in figure 5 and two di~ferent si~es in figure
6. This arrangement has a lower volume efficiency but the
rounded shape o~ the particles may help them feed more
satis~actorily to s-ome ~riction-ef~ected extrusion machines.
EXAMPLES
Electrodes, measuring 2~5 mm by 280 mm~ for use in a
pilot electro-re~ining cell were prepared as follows:
Exam~le 1
A titanium sheet was coated on both sides with a
photo-resist and exposed on each side in turn to actinic
light under a negative having dark bands about 4 mm wide
at 15 mm centres in a square grid pa~tern made by sticking
strips of opaque material on a clear plastics sheet and
photographing it. ~he unexposed grid pattern was removed
by conventional development leaving a pattern o~ protected
, l . _ . _ _ __ . . . .... , _ . .. ... . ... . . ... . . . .. . .... . .... . ..... .. . . . . ..
~ 6
squares o~ about 11 mm side. The plate was then anodised
using a conventional technique to apply a durable oxide
coating to the exposed metal; the remaining photoresist
was then stripped off with a solvent to expose the metal
in the unanodised area o~ the squares. (Pattern as
figure 2).
Example 2
A copper sheet was divided into square grid patterns
o~ various sizes ranging ~rom about 10 mm to 25 mm side
using a room-temperature vulcanising silicone rubber
composition, sold b~ Imperial Chemical Industries Limited
under the trade mark Silcoset a~ Silcoset RTV No. 100,
No. 101, or No. 105 (two-pack) or No. 151, No. 152 or
No. 15~ (one-pack) applied to the clean dry surface of
the sheet in a strip o~ about 5 mm wide, over a priming
strip o~ the recommended primer OPl. (Pattern as
~igure 2). A conventional parting agent was then applied.
Example ~
An adhesive-backed pvc filmg about 1 mm thick~ sold
as a pro~ective ~ilm ~or book covering, was punched with
a square pattern o~ round holes each about 25 mm in
diameter on 18 mm centres with smaller holes about 5 mm
in diameter interposed diagonally between them and was
stuck to the surface of a titanium sheet. (Pattern as
figure 6).
Exam~le 4 "` `;
A resilien~ plasticised pvc sheetg about 5 mm thick,
was punched with a hexagonal pattern of 20 mm holes on
- 12 -
.
.. . .. .
8~
mm centres, clamped to a titanium sheet and held ~mderpressure applied at many points across its surface. (Pattern as
Figure 5).
Example 5
A thick tltanium sheet had a diagonal square pattern
o grooves 3 mm square an~ on 15 mm centres cut into it on each
face by a circular saw. (Pattern as Figure 1). These grooves
were filled by pouring in a cold-setting synthetic resin
composition comprising, in parts by weight:
Low-viscosity Bisphenol-A type expoxy
resin sold under the trade mark "Araldite"
as "Araldite MY 750" 50
Talc 40
Polyoxypropylene diamine of molecular weight
about 2000, sold under the trade mark
"Jeffamine" as "Jeffamine 2000", a bonding
agent 10
Hardener, sold under the trade mark
"Jeffamine" as "Jeffamine D230" and described
as the bis 2-aminopropyl ether of a diol, with
molecular weight 230 14
Proprietary curing promoter sold as
"Accelerator 398" 5
(Jeffamine D2000, Jeffamine D230 and Accelerator 398
are all obtainable from Jefferson Chemical Company, Houston,
Texas, U.S.A.).
After the resin had hardened the surfaces of the
electrode were smoothed by sandlng.
Example 6
This was the same as Ex~ample 5 except -that the grooves
were on 8 mm centres, leaving deposition areas 5 mm square.
13 -
Example 7
This was similar to example 2 except that the
shee~ was o~ ~itanium and the insulating material was the
asphalt-based material sold under the trad~mark
"Mexphalte" applied by brushing or by printing with a
patterned rubber roll.
Ea¢h o~ the electrodes prepared as descr~bed in
examples 1-7 was ~ade cathodio ~n the electrolytic cell
using conventional anode copper cut to 235 mm x 254 mm
and conventional electrolyte and circulation procedure.
The current density was maintained at approximately the .
conventional level (the ef~ective area is initially less
than ~or ~ plain cathode o~ the same overall size but
rises as deposition proceeds and may in some cases exceed
the area of a plai~ cathode for part o~ the time when
copper is being deposited on the edges o~ separate blocks
already deposited). The electrodes oP Examples 1, 5 and
could be re-used without being ~reshly prepared.
This was similar to E~ample 1 exoept that the
negative was made with only one set of parallel dark
bands and consequently rectangular copper ~krips extending
the full length o~ the electrode were produced. (Pattern
as ~igure 3).
All the electrodes could be used to produce
~rangible sheets of ductile copper by continuing deposition
to various thicknesses ln the region o~ 10 mm.
Granular copper produced by depositing on the
- 14 -
~ .. . ....... . . . . . . . . .. ... . . .. . . . . .. . .. . .
~18~
electrode o:f example 6 to a thickness o:f 5 mm, washing and
stripping was re-washedg dried and pre-heated to 275C;
the roughly cubic granules were ~ed ~o a small "Con~orml'
~riction-ef~ected extrusion machine (a laboratory prototype
with a groove about 9 mm square~ and extruded at a ratio
o~ 8:1 to ~orm round rod 3.~ mm in diameter. After
drawing into wire 0.5 mm ln diameter and annealing the
product had an elongation of 26%, tensile strength
2~5 MN/m2, and electrical conductivity 101.8% IACS.
Similar results can be expected ~rom extruding
granules deposited on the electrodes o~ the other examples
or made by fracturing sheets deposited thereon, but a
larger ~riction-e~ected extrusion machine will be required
to accept the larger granules.
- 15 -
-, ~
.. ! .j~l . ~
. dD~`~
