Apparatus for solder joining metal tapes

An apparatus for solder joining metal tapes to form laminated metal tapes comprises an alignment box having a base and a sidewall means extending therefrom to define a tapered inner channel extending through the box. The tapered channel having an entrance end and narrowing to an exit end. At least one tapered wall extending from the base and within the inner channel to define subchannels that are spaced at the entrance end and converge into the inner channel before the exit end. The sidewall means and tapered wall extending from the base to respective wall tops, and a cover extending over the channel and subchannels is mounted on the wall tops. The base, sidewalls, inner wall, and cover being configured to form the channel and subchannels to have a first preselected distance between the base and cover that is greater than the width of the tapes. A second preselected distance between oppositely facing walls bordering the subchannels that is greater than the thickness of the tapes, and a third preselected distance between oppositely facing walls at the exit end that is greater than the thickness of the laminated tapes. A solder duct means mounted on the box for directing molten solder into the inner channel to flow from the exit end to the entrance end. The solder duct means having a slot extending therethrough and aligned with the exit end. A seal means mounted on the solder duct means adjacent the slot for minimizing solder escaping from the slot while solder coated tapes pass therefrom, and a wiper means mounted on the solder duct means and positioned from the seal means removes excess solder from tapes passing through the seal means.

BACKGROUND OF THE INVENTION 
This invention relates to an apparatus for solder joining metal tapes in a 
continuous tape laminating apparatus. 
Soldering has been defined as metal coalescence below about 800.degree. F. 
As a result, soldering facilitates joining parts while minimizing damage 
from heating. Solder alloys are comprised of tin and lead, and the tin 
component reacts with metals to be joined to form a metallurgical bond. In 
many soldering systems, an intermetallic compound is developed at the 
interface between the solder and the base metal, producing an essentially 
complete metallurgical joint. The cleanliness and chemical composition of 
the surfaces to be joined are critical to the process. For example, flux 
can be used to insure that the base metal is sufficiently cleaned to 
provide adequate spread and flow of the soldering alloy to promote joint 
formation. However, when a flux is not used surface cleanliness, e.g., 
freedom from surface oxides, is critical to joint formation. 
One application that has been disclosed for solder joined metal tapes is 
for laminated superconducting tapes, for example disclosed in U.S. Pat. 
No. 3,537,827. Briefly described, the laminated superconducting tape is 
comprised of a brittle triniobium tin superconducting layer bonded between 
outer laminae of non-superconductive metals having a coefficient of 
thermal expansion greater than that of the triniobium tin inner layer. The 
outer laminae are bonded integrally to each side of the triniobium tin 
inner layer by soldering. As a result, the triniobium tin inner layer is 
in a state of mechanical compression which results from the fact that the 
outer laminae are in a state of mechanical tension. 
Uniform solder joining of the outer laminae to the relatively brittle inner 
layer provides benefits, such as, improved thermal conductivity for 
cooling of the superconducting core of the tape, improved formability of 
the tape, and greater resistance to handling damage. For some applications 
the laminated tape must have a uniform cross section, for example to 
enable uniform winding of the tape to form coils. Therefore, it is 
desirable to solder the metal tapes to form a uniform solder joint, and a 
laminated tape having a uniform cross-section with a smooth surface finish 
in a continuous operation. However, imperfections in the tapes that are to 
be laminated such as camber or wavy edge cause misalignment of the tapes 
in the width dimension, oxidized tape surface causes dewetting and poor 
solder bonding, and particles in the solder such as dross (tin oxide) or 
intermetallic compounds (CuSn) can cause non-uniform cross-sections and 
excessively rough surface finish defects in the laminated tape. 
Excessive time at the soldering temperature, about 250.degree. C., can 
produce softening of the outer laminate. Since yielding of the outer 
laminate will cause fracture of the relatively brittle superconductive 
inner laminate, it is desirable to maintain the yield strength of the 
outer laminate as high as possible. Therefore it is desirable to minimize 
the time the tapes are at the soldering temperature. 
It is an object of this invention to provide an apparatus for solder 
joining metal tapes to form a laminated metal tape. 
It is another object of this invention to provide an apparatus for solder 
joining metal tapes symmetrically aligned in the width dimension. 
It is another object of this invention to provide an apparatus that aligns 
metal tapes symmetrically in the width dimension having nonuniformities 
that cause misalignment of the tapes such as camber or wavy edge. 
It is another object of this invention to provide an apparatus for solder 
joining metal tapes rapidly so that the outer laminae is at the soldering 
temperature for a minimum time to reduce softening of the outer laminae. 
It is another object of this invention to form an apparatus for solder 
joining metal tapes with a high uniformity of solder bonding across the 
entire surface of the facing tapes. 
It is another object of this invention to provide an apparatus for 
continuously solder joining metal tapes while minimizing bending or 
abrasion of the tape surface. 
It is another object of this invention to provide an apparatus for 
continuously solder joining metal tapes. 
BRIEF DESCRIPTION OF THE INVENTION 
The apparatus of this invention joins metal tapes to form laminated metal 
tapes in a continuous tape laminating apparatus. As used herein the term 
"tape" is a body having a length, width, and thickness dimension with 
major surfaces in the length and width dimension. The apparatus is 
comprised of an alignment box having a base and a sidewall means extending 
therefrom to define a tapered inner channel extending through the box. The 
tapered channel having an entrance end and narrowing to an exit end. At 
least one tapered wall extends from the base and within the inner channel 
to define subchannels that are spaced at the entrance end and converge 
into the inner channel before the exit end. The sidewall means and tapered 
wall extend from the base to respective wall tops. A cover extending over 
the channel and subchannels is mounted on the wall tops. 
The base, sidewalls, inner wall, and cover are configured to form the 
channel and subchannels to have a first preselected distance between the 
base and cover that is greater than the width of the tapes, a second 
preselected distance between oppositely facing walls bordering the 
subchannels that is greater than the thickness of the tapes, and a third 
preselected distance between oppositely facing walls at the exit end that 
is greater than the thickness of the laminated tape. 
A solder duct means is mounted on the box for directing molten solder into 
the inner channel to flow from the exit end to the entrance end. The 
solder duct means having a slot extending therethrough and aligned with 
the exit end that is larger than the cross-section of the laminated tape. 
A seal means is mounted on the solder duct means adjacent the slot for 
minimizing solder escaping from the slot while solder coated tapes pass 
therefrom. A wiper means mounted on the solder duct means and positioned 
from the seal means removes excess solder from tapes passing through the 
seal means. Preferably, the seal means and wiper means are compliant so 
that minor sized particles, for example up to about 20 microns, having 
minimal effect on the tape performance can pass therethrough.

DETAILED DESCRIPTION OF THE INVENTION 
Superconducting tapes and the method of forming the superconductor on such 
tapes are well known. For example British patents 1,342,726 and 1,254,542 
incorporated by reference herein, disclose improved superconducting tapes 
and methods of forming the improved tapes. The '827 referenced above 
discloses improvements in laminating superconductive tapes. In addition, 
triniobium tin tapes are well known in the art being described, for 
example, in "Superconducting Properties of Diffusion Processed Niobium-Tin 
Tape," M. Benz, I.E.E.E. Transactions of Magnetics, Vol. MAG-2, No. 4, 
December 1966, pp 760-764, incorporated by reference herein. 
A method of forming a continuous length of triniobium tin tapes is briefly 
described by making reference to FIGS. 1-4. A niobium tape 2 comprised of 
up to about 5 atomic percent of a metal selected from the group consisting 
of zirconium, aluminum, hafnium, titanium, and vanadium, and up to about 
5000 parts per million oxygen is contacted with a molten tin bath 
comprised of up to about 45 weight percent copper, up to about 25 weight 
percent lead, and the balance tin to form a coating 4. Alternatively, the 
coating may be deposited onto the niobium tape at least partly by plating, 
or by electrolytic or chemical processes. 
The coated niobium tape 10 is reaction annealed at about 850.degree. to 
1100.degree. C. to react the niobium substrate with the coating and form 
laminae 6 of triniobium tin on triniobium tin tape 12. Excess coating 4', 
as shown in FIG. 3, covers the triniobium tin laminae 6. Tin reacts with 
niobium to form the triniobium tin, and excess coating 4' becomes enriched 
in any copper or lead that was in coating 4. The remaining niobium tape 2, 
is reduced in thickness from reaction with the coating 4 to form the 
triniobium tin laminae 6. Non-superconducting outer laminae 8 are bonded 
to the triniobium tin tape 12 by soldering to form a laminated triniobium 
tin tape 14 having improved strength and formability. The apparatus of 
this invention is suitable for solder joining the outer laminae 8 
continuously onto triniobium tin tape 12. 
Referring to FIGS. 5 and 6, the apparatus is comprised of a rectangular 
alignment box 2 formed from a material resistant to reaction with molten 
solder, such as tool steel or stainless steel. Preferably, the tool steel 
has an adherent oxide surface layer, such as a blue oxide formed thereon. 
The alignment box 2 has a base 4, and sidewall means 6 extending therefrom 
to form a tapered inner channel 8. Tapered channel 8 has an entrance end 
10, and narrows to an exit end 12. Tapered inner walls 14 and 16 extend 
from the base and within the inner channel to define subchannels 18, 20, 
and 22 that are spaced at the entrance end, and converge into inner 
channel 8 before the exit end 12. The space between inner walls 14 and 16, 
and sidewalls 6 and inner walls 14 and 16 is the width of subchannels 18, 
20, and 22. The subchannel width is greater than the thickness of the 
tapes to be joined, for example, a subchannel width of about 3 millimeters 
is suitable for tapes having a thickness of about 20 to 200 microns. 
Referring to FIG. 5, a triniobium tin tape 40, can be laminated with tapes 
of copper 42 and 42' to form laminated tape 40'. Bending or mechanical 
abrasion of the triniobium tin tape 40 is minimized since there is no 
bending or contact with rollers or shoes within the laminating apparatus 
of this invention. FIG. 6 is a side view cross-section at the centerline 
of the alignment box where inner tape 40 can extend through the alignment 
box. 
Base 4 has bores 24, 26, and 28 extending therethrough and positioned 
between inner tapered walls 14 and 16, and sidewalls 6. Preferably, the 
diameter of bores 24, 26, and 28 is larger than the width of subchannels 
18, 20, and 22, so that the bores extend to sidewalls 6, and inner walls 
14, and 16 to form concave surfaces 25, 27, and 29 in the sidewalls and 
inner tapered walls. The bores extended into the sidewalls ensure that 
solder flowing through the bores and into the subchannels flows on both 
sides of the tapes passing therethrough. As a result, wetting of solder on 
both tape surfaces is promoted, and contact between the tapes and the 
sidewalls or inner walls is minimized. 
Sidewall means 6 and inner walls 14 and 16 extend a preselected distance 34 
from base 4 to respective wall tops 30, shown in FIG. 6. The preselected 
distance 34 is slightly larger than the width 34' of the tapes that are to 
be joined in the box 2. This preselected distance 34 determines the 
registry of the laminated tapes. The more distance 34 exceeds the width 
34' of the tapes, the more disregistry can be tolerated in laminating the 
tapes, i.e., the more shape imperfections such as camber in the tape can 
be tolerated. For example, the preselected distance 34 can be about 625 
microns greater than the width 34' of tapes 40, 42, and 42' so that the 
alignment of the tape edges does not vary by more than 625 microns. 
Referring to FIG. 6, a rectangular housing 44 contains box 2 mounted on a 
solder duct means for directing molten solder into the inner channel 8 and 
bores 24, 26, and 28 to flow from the exit end to the entrance end of 
channel 8 and subchannels 18, 20, and 22 as shown by arrows 3, and means 
for collecting and draining molten solder flowing from the entrance end of 
alignment box 2. 
Rectangular housing 44 is comprised of a bottom plate 46, end plates 45 and 
48, and sidewalls 47 (shown in FIG. 8) extending from bottom plate 46 to 
form an inner cavity 43. Base plate 46 extends beyond the entrance end of 
alignment box 2 and the sidewalls and first end plate 45 extend therefrom 
to enclose a first cavity section 43a for collecting molten solder flowing 
from entrance end 10. First end plate 45 has rectangular holes 11, 13, and 
15 (shown in FIG. 5) extending therethrough. Rectangular holes 11, 13, and 
15 are larger than the cross-section of the tapes, and aligned with 
imaginary planes extending from subchannels 18, 20, and 22. Alignment box 
2 is mounted on a duct piece 52 having sidewalls 53 (shown in FIG. 8), and 
a divider wall 54 therebetween separating the portion of channel 43 below 
box 2 into two duct sections 43' and 43". Solder enters alignment box 2 
through first duct section 43', and drains from cavity section 43a through 
second duct section 43". 
Second end plate 48 is mounted at the end of housing 44 opposite the first 
end plate 45, and adjacent exit end 12. A notch 50 formed in second end 
plate 48 is aligned with and extends below exit end 12 to provide 
communication between exit end 12 and first duct section 43'. A slot 56 
extending through second end plate 48 at notch 50 is larger than the 
laminated tape cross-section and is aligned with exit end 12 to provide 
for passage of the laminated tape therethrough. 
A seal means 58 is mounted on the second plate 48 over slot 56 to minimize 
solder escaping from slot 56 while allowing solder coated tapes to pass 
therethrough. A suitable seal means 58 can be formed from a resilient 
material resistant to molten solder, such as silicone rubber or TEFLON 
synthetic resin polymer. For example, a sheet of silicone rubber is razor 
cut on a line to form a slit aligned with slot 56. A suitable silicone 
sheet is about 3 millimeters thick, and is at least large enough to extend 
over and beyond slot 56. Optionally, a second drain means 60 formed from 
material resistant to molten solder such as stainless steel is mounted 
adjacent seal means 58 and provides for draining of solder that passes 
through seal means 58. Conventional resistance heating rods 61 in second 
drain means 60 heat the drain means so that solder escaping from seal 
means 58 will drain therefrom. 
A wiper means 62 is positioned from the seal means to remove excess solder 
from the tapes exiting the seal means by mounting adjacent the second 
drain means 60. Wiper means 62 can be formed from any material resistant 
to molten solder and rigid enough to wipe excess solder from the laminated 
tape. Suitable wiper means 62 can be formed from metal such as steel, 
iron, nickel alloys, and the like, fiberglass, TEFLON synthetic resin 
polymer, silicone rubber, and boron nitride. Preferably, wiper means 62 is 
formed from a material that is also compliant, such as the silicone 
rubber. A suitable silicone rubber is temperature resistant to about 
250.degree. C., and has a durometer hardness of at least about shore A 40. 
A suitable silicone rubber is GE RTV silicone rubber, or high temperature 
gasket GEC560, GE, Waterford, N.Y. 
Wiping means 62 is configured to present a wiping surface 63 that extends 
beyond the width of tape 40', and from second drain 60 a distance 
sufficient to wipe excess solder from laminated tape 40', for example, 
about 2 centimeters. Wiping means 62 is formed to have a smooth wiping 
surface 63 to apply a uniform and even pressure across the surface of 
laminated tape 40' facing wiping surface 63. For example, wiping means 62 
formed from silicone rubber can be cast as a monolithic L-shaped member, 
or two sheets of silicone rubber sheet can be joined together with the RTV 
silicone rubber to form the L-shaped member shown in FIG. 5. It is further 
contemplated that wiping means 62 can be configured as two rollers (not 
shown) positioned to apply a compressive force to laminated tape 40' after 
seal means 58 to remove excess solder from the laminated tape. Preferably, 
the rollers have at least an outer layer of a compliant material such as 
the silicone rubber bonded on the roller to permit small particles, for 
example up to about 20 microns, on the laminated tape 40' to pass through 
the wiping means without causing a substantial increase in the stress 
applied to the tape. Excess solder wiped from the laminated tape flows 
into and drains from second drain means 60. 
Mounting bolts 66 (shown on FIG. 5) on second end plate 48 extend therefrom 
through aligned holes in seal means 58, drain means 60, and wiper means 
62. Nuts 64 threaded onto bolts 66 are tightened to bias seal means 58, 
drain means 60, and wiper means 62 into sealing engagement with second end 
plate 48. 
Means for providing a preselected atmosphere over the alignment box are 
further shown by making reference to FIGS. 6 and 7. A silicone sheet 70 is 
mounted on first end plate 45 by bolted attachment through metal cover 
plate 72. Silicone sheet 70 has slits 74 extending therethrough and in 
alignment with the rectangular holes 11, 13, and 15 in the first end 
plate. Cover plate 32 configured to extend between end plates 45 and 48, 
and sidewalls 47 is mounted on the wall tops of box 2. Preferably, housing 
44 is assembled with molten solder resistant seals, for example of GERTV 
red high temperature silicone rubber such as RTV 106, between the base, 
side walls, end plates and cover. Optionally, a viewing port 86 extending 
through cover 32 at a position over the entrance end of box 2 has a mating 
cylindrical tube (not shown) extending therefrom to a viewing glass sealed 
thereon. A gas inert to the molten solder such as nitrogen or argon can be 
introduced into housing 44 through a conventional gas valve (not shown) 
extending from the cylindrical tube. 
Optionally, housing 44 has conventional heaters 92 such as calrod heaters 
attached thereto to maintain the temperature of the housing at the 
soldering temperature. The heaters 92 and housing 44 are then enclosed in 
an outer housing 94. Conventional insulation such as fiberglass or 
Fiberfrax alumina fibers can be placed between housing 44 and outer 
housing 94. Outer lid 96 configured to mate with housing cover 32 and 
extend over housing 44 is sealed thereon with the RTV silicone rubber. 
Conventional clamps 98 bias outer lid 96 and housing cover 32 against 
housing 44 to form a seal that minimizes leakage of molten solder flowing 
in housing 44. 
In operation, a conventional molten metal pump system provides a flow of 
molten solder through pipe 80 and into first duct 43'. Suitable molten 
solder pump systems such as a wave solder pump system can be obtained from 
Wenesco, Chicago, Ill. The molten solder passes from first duct 43' 
through notch 12 and bores 24, 26, and 28 into channel 8 and subchannels 
18, 20 and 22 flowing in the direction from the exit end to the entrance 
end of channel 8 as shown by arrows 3. The tapes enter the housing 44 at 
seal means 70 and enter the alignment box at the entrance end 10, passing 
in the direction of arrow 90. In other words, the molten solder passes in 
the direction of arrows 3 counter-current to the direction 90 that the 
tapes are passing. 
The counter-current solder flow provides a washing action that washes 
particles such as dross and copper-tin intermetallics from the alignment 
box and into the cavity 43a and out of the alignment box through drain 
cavity 43" and out through pipe 82, as shown by the direction of arrows 3. 
Pipe 82 returns the solder to the molten solder pump system. As a result, 
the deposition of particles in the solder onto the laminated tape is 
minimized. The particles are washed out of the alignment box to minimize 
particle accumulation and buildup, and the formation of larger particle 
agglomerations. Particles large enough to cause excessive surface 
roughness, poor bonding of the laminate to the tape, or that alter the 
cross section so that the tape does not wind evenly are washed away by the 
counter-current molten solder flow. The flow of molten solder at notch 12 
also provides for washing of particle buildup occurring at seal means 58. 
Wiper means 62 removes excess solder from the laminated tape, and smooths 
particles that are deposited on the tape. Preferably, wiper means 62 is 
formed from a compliant material such as silicon rubber so that minor size 
particles that do not affect the laminated tape performance pass through 
the compliant wiper means. 
Wiper means 62 apply a force to laminated tape 40' to remove excess solder 
from the laminated tape. Additional pressure can be applied to wiping 
means 62 by conventional means (not shown) for applying a compressive 
force to wipers 62' such as electric servo motors, vacuum motors, or air 
activated grippers, for example available from PHD, Inc., Fort Wayne, Ind. 
Suitable air grippers are described in U.S. Pat. No. 4,607,873, 
incorporated by reference herein. 
Although the apparatus above has three subchannels for solder joining three 
tapes, it should be understood that the apparatus of this invention can 
have fewer subchannels, i.e. two, or can have more subchannels, e.g. five 
or more, by either subtracting or adding additional inner tapered walls in 
the channel of the alignment box.