A high temperature solder device for flat cables includes a microwelder, an anvil which acts as a heat sink and supports a flexible flat ribbon cable that is to be connected to a multiple pin connector. The microwelder is made from a modified commercially available resistance welding machine such as the Split Tip Electrode microwelder by Weltek, which consists of two separate electrode halves with a removable dielectric spacer in between. The microwelder is not used to weld the items together, but to provide a controlled compressive force on, and energy pulse to, a solder preform placed between a pin of the connector and a conductor of the flexible flat ribbon cable. When the microwelder is operated, an electric pulse will flow down one electrode, through the solder preform and back up the other electrode. This pulse of electrical energy will cause the solder preform to heat up and melt, joining the pin and conductor

Haehner, Carl L.

English

NASA Technical Reports Server

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US005126527A 
United States Patent [I91 p i ]  Patent Number: 5,126,527 
Haehner 1451 Date of Patent: Jun. 30, 1992 
[54] HIGH TEMPERATURE SOLDER DEVICE 
[75] Inventor: Carl L. Haehner, Dayton, Md. 
1731 Assignee: The United States of America as 
FOR FLAT CABLES 
represented by the Administrator of 
the Kational Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 718,046 
[22] Filed: Jun. 20, 1991 
[51] Int. c1.5 ................................................ B23K 1/00 
[52] U.S. C1. ............................... 219/85.15; 219b35.19 
1581 Field of Search ............... 219h5.18, 85.21, 85.16. 
2191'85.19, 56, 56.1, 233, 85.15. 86.9, 161; 
350/96.15; 228/46 
1561 References Cited 
U.S. PATENT DOCUMENTS 
3.238.351 3/1966 
3.393.288 7/1968 
3.418.44 12/1968 
3.478.190 11/1969 
3.552.630 ]/I971 
4.071,730 ]/I978 
4,342.083 2/1979 
4.220.845 9/1980 
4,339.651 7/1982 
4.396.819 8/1983 
4,854.659 8/1989 
4,899,029 2/1990 
Hill ..................................... 219/56.1 
Barstow et al. .................... 219B6.9 
Ruehlmann ............... 
Daues ................................ 2 19B6.9 
Dean ..................................... 228/46 
Bassler ............................. 219/85.15 
DuRocher 219/161 
Morreale ............................. 219/243 
Kraus ............................... 219/85.15 
Muchkin et a]. ...................... 219/56 
Hamerslag et al. .............. 350/96.15 
Kumagai ............................ 219/56.1 
5,050.036 9/1991 Oudick et al. ...................... 361/385 
FOREIGN PATENT DOCUMENTS 
556915 7/1975 U.S.S.R. ............................. 219/56.1 
Primary Examiner-Geoffrey S. Evans 
Attorney, Agenr. or Firm-R. Dennis Marchat; Guy M. 
Miller; Paul S. Clohan, Jr. 
V I  ABSTRAm 
A High Temperature Solder Device for Fiat Cables 
includes a microwelder, an anvil which acts as a heat 
sink and supports a flexible flat ribbon cable that is to be 
connezted to  a multiple pin connector. The mi- 
crowelder is made from a modified commercially avail- 
able resistance welding machine such as the Split Tip 
Electrode microwelder which consists of two separate 
electrode halves with a removable dielectric spacer in 
between. The microwelder is not used to "weld" the 
items together, but to provide a controlled compressive 
force on, and energy pulse to. a solder pre-form placed 
between a pin of the connector and a conductor of the 
flexible flat ribbon cable. When the microwelder is 
operated, an electric pulse will flow down one elec- 
trode. through the solder pre-form and back up the 
other electrode. This pulse of electrical energy will 
cause the solder pre-form to heat-up and melt, joining 
the pin and conductor. 
8 Claims, 3 Drawing Sheets 
https://ntrs.nasa.gov/search.jsp?R=19920019851 2020-03-24T07:14:57+00:00Z
US.  Patent June 30, 1992 Sheet 1 of 3 5,126,527 
22 
f -I I I  __ . .. . . .- -. - . . . - 
FIG. 1 
U.S. Patent June 30, 1992 Sheet 2 of 3 5,126,527 
26 
28 
FIG. 2 a  
0 
FIG. 2 ' b  
U S .  Patent June 30, 1992 Sheet 3 of 3 5,126,527 
FIG. 3 
5,126,527 
1 
HIGH TEMPERATURE SOLDER DEVICE FOR 
FLATCABLES 
ORIGIN OF T H E  INVENTION 
The invention described herein was made by an em- 
ployee of the United States Government, and may be 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
TECHNICAL F I E L D  
This invention relates to soldering devices and partic- 
ularly to a solder device useful for soldering multi-pin 
connectors to  thin fragile flat ribbon cables using high 
temperaturehigh thermal fatigue solders. 
BACKGROUNDART 
Various soldering devices and techniques are known 
in the prior art. One particular application of the joining 
of two items by soldering is the connection of miniature 
and subminiature connectors to very thin flat flexible 
cables. In this application, conventional soldering tech- 
niques have been limited to the low to intermediate 
temperature solders. Fabrication temperatures are re- 
stricted to around 180" C. or less to prevent damage to  
the plastic insulation on the thin flat cables. This restric- 
tion precludes the use of the higher melting temperature 
solders with correspondingly greater thermal fatigue 
resistance. Presently, connections to flat cables are 
made using conventional soldering techniques using 
Eutectic 63 SN, 37 Pb solder. which has a melting point 
of around 183" C. This solder has low thermal fatigue 
resistance, and failures have been known to occur at 
only several thousand cycles at moderate -40" to  +40' 
C. low cyclic conditions. For  example, on one item of 
space hardware, solar array panels exhibited solder 
fatigue after only 10,000 thermal cycles. This is of great 
concern when fabricating hardware for use in outer 
space. The anticipated temperatures in this environment 
for many orbital platforms may range from -40" C. to 
+ 115" C. at 5,000 cycles per year for thirty years, or 
150.000 cycles. The hundreds to  thousands of solder 
connections required in this type of hardware requires a 
high reliability solder technique. In addition, each orbit 
in and out of the sun will produce wide temperature 
swings further exacerbating the thermal stresses placed 
on these connections. 
STATEMENT OF THE INVENTION 
the combined use of shaped electrodes. carefully select- 
ing the gap between the electrodes. proper selection 
and placement of a solder preform, controlling the ap- 
plied force on the connector/solder preform/conductor 
5 sandwich, selection of electrode material. and a con- 
trolled applied electrical pulse. In addition, a heat- 
sinked anvil further protects the thin plastic insulation 
of flexible ribbon cable. With improved thermal resis- 
tance, electrical reliability will be improved for hard- '' ware that is exposed to cyclic temperatures in space- 
craft, aircraft, and other severe applications. 
BRIEF DESCRIPTION OF T H E  DRAWINGS 
FIG. 1 is a front view of a High Temperature Solder 
l 5  Device for Flat Cables according to the present inven- 
FIGS. 20 and 2b are enlarged views of the shaped 
FIG. 3 is an alternate embodiment of the High Tem- 
tive concepts. 
electrode tips used in the present invention. 
perature Solder Device for Flat Cables. 
2o 
DETAILED DESCRIPTION OF T H E  
INVENTION 
25 Referring now to FIG.  1, a High Temperature Solder 
Device for Flat Cables according to the present inven- 
tive concepts is shown generally by reference numeral 
10. Device 10 includes a microwelder 3 (only the elec- 
trodes are shown), an anvil 16. which is a heat sink and 
30 also supports a flexible flat ribbon cable 22 that is to be 
connected to a subminiature multiple pin connector 8. 
Microwelder 3 is constructed from a modified com- 
mercially available resistance welding machine. As 
those skilled in the art will recognize. resistance weld- 
35 ing is a general term for a group of methods for joining 
metals together electrically. In resistance welding, a 
low voltage forces a high-density current for a rela- 
tively short time through an area covered by the welfl- 
ing electrodes. A mechanical force must be applied to 
4.0 the electrodes before, during, and after the time the 
current flows in order to  produce the proper conditions 
for heating and forging the metals together. In a typical 
resistance welder, the welding current flows from a 
transformer through an electrode of the welder, the 
45 workpiece? the other electrode, and back to the trans- 
former. Open-circuit secondary voltage necessary to  
produce the welding current is determined by the impe- 
dance of the secondary circuit. When this voltage is 
multiplied by the welding current the demand kilovolt- 
50 amperes (kva) of the welding transformer is obtained. It is therefore an object of the present invention to  
provide a device for soldering connectors to thin flat 
cables, using high temperature solder, without damag- 
ing the cable materials. 
Because the welding current flows for a small part of 
the total time, the demand kva rating is greater than the 
thermal rating. Total heat H generated in the workpiece 
A funher ob,ect of the invention is to improve the 55 and electrodes is expressed in watt-seconds and is given 
peres, R is the sum of contact and workpiece resistances cables. 
measured between the electrodes, and T is the time in 
soldered connections for outer space applications. seconds. 
An example Of a suitable resistance welder for Use in 
device that will allow the use of solder alloys that have the Present invention is the split Tip Electrode mi- 
superior thermal fatigue resistance. The present inven- crowelder made by WELTEK, which consists of two 
tive device carefully controls the heat zone and solder separate electrode halves, electrode 2 and electrode 4, 
quantity, allowing the use of alloys with higher melting with a removable dielectric spacer 6 between, which is 
temperatures. By limiting, confining, and carefully con- 65 joined by Nylon screws. The size of the gap between 
trolling the energy pulse to  the heat affected zone on a electrode 2 and electrode 4 is determined by the thick- 
microscopic scale, it will allow soldering with these ness of the dielectric spacer 6 used. In the WELTEK 
high temperature solders. This is accomplished through microwelder 3, the electrode gap can be easily changed 
thermal fatigue life of solder connections made on flat by the equation H=pR where I is the current in am- 
A still further object is to increase the reliability of 
ne foregoing objects are achieved by providing a 60 
5.126.527 
3 
from 0.001'' up to 0.025". The WELTEK model num- 
bers are 310-SP, 410-D, 410-DVP and the 410-E. 
II? the present invention, microwelder 3 is not used to 
"weld" two items together, but to provide a controlled 
compressive force on, and electrical pulse to, a solder 
pre-form or solder paste 30, which is placed between 
pin 12 of subminiature multiple pin connector 8 and 
conductor 26 of flexible flat ribbon cable 22. When 
microwelder 3 is operated. an electric pulse will flow 
down electrode 2, through shaped electrode tip 5, 
through pin 12, through solder pre-form 30 and conduc- 
tor 26, back through pin 12 to shaped electrode tip 7, 
and up electrode 4. This pulse of electrical energy will 
cause solder pre-form 30 to heat-up and melt, joining 
pin 12 to conductor 26. Microwelder 3 is then moved to 
the next pin 12 and the above steps are repeated on all 
the pins on the top row of connector 8. The subminia- 
ture multiple pin connector 8 can then be flipped over 
so the bottom row of pins (pins 14) can be joined to a 
second flexible flat ribbon cable in the same manner that 
the top row of pins 12 were joined. 
By carefully selecting the resistance welding parame- 
ters to produce the proper amount of energy to solder 
pre-form 30, pin 12 can be safely and securely soldered 
to  conductor 26 without damage to flexible cable 22. 
The welding parameters need to be carefully selected 
and controlled as flexible flat ribbon cable 22 is fragile. 
Typically, cable 22 is made from flexible plastic (Kap-. 
ton or Mylar) insulation 24 and 28 on either side of 
multiple copper conductors 26 with are generally 
0.050" wide by 0.002" thick. The ribbon cable widths 
vary from about one inch to several inches. In the past, 
excessive heat used to solder pin 12 to conductor 26 has 
caused delamination of conductor 26 and/or damage to 
insulators 24 and 28. 
Prior to the soldering of connectors to cables. mi- 
crowelder 3 settings would be determined using an 
iso-strength diagram to determine optimum conditions 
for a particular set of cables and connectors. Samples 
would be made at selected settings and tensile tested. A 
graph of electrode compressive force versus power 
setting would be made recording the tensile test results 
on the graph. The settings would be varied until results 
indicated good tensile strengths. Thermocouple mea- 
surements and electrode electrical pulses would be re- 
corded to produce records and to monitor the soldering 
process. Settings would vary depending on the configu- 
ration and particularly on the selected solder pre-form 
30. 
In order to protect the plastic insulation 24 and 28 of 
the flexible flat ribbon cable 22, anvil 16, sitting on base 
18 (e.g., a table) is used not only to  position and support 
cable 22 but to provide a heat sink during the solder 
operation. Anvil 16 can also shaped to  accommodate 
different connector 8 configurations, and can be pro- 
vided with a cooling medium such as water or air 
through intake 21, voids 20, and outflow 23, if neces- 
sary. Anvil 16 will then act like a radiator to remove the 
heat during the soldering operation. Anvil 16 would 
typically be made from aluminum or any other metal 
with good (high) thermal conductivity. 
A principal advantage of the present invention is that 
it will allow the use of solder alloys with greater ther- 
mal fatigue resistance. This is accomplished by provid- 
ing a precise method for controlling the heat input to 
the parts being soldered. Solders that could not be used 
in the prior art can now be used effectively without 
damage to the fragile flat ribbon cable 22. High thermal 
4 
fatigue solders such as the Indium alloys, Silver alloys, 
etc. can now be used. Typical high temperature solders 
are listed in table I below. 
TABLE I 
5 
LIQL3Dl'S 
310' C. 
240" C. 
309" C. (Eutectic) 
231' C. 
221' C. (Eutectic) 
C0,MPOSITIOS 
92.5 Pb. 5 In. 2.5 A g  
95 Sn. 5 Sb 
97.5 Pb. 1.5 Ag.  i Sn 
60 Pb. 40 I n  
96.5 Sn. 3.5 Ae 
10 50 In, 50 Pb 210' c. 
In order to properly control the flow of electricity 
through solder pre-form 30, the shape of electrode tips 
l 5  5 and 7 should conform to the shape of pin 12. This is 
shown in FIGS. 2u and 26 which are views of the elec- 
trode tips from view 2-2 of FIG. 1. In FIG. 2u, pin 12 
is a round pin, typically having a diameter of 0.050", 
and therefore electrode tip 5 on electrode 2 has a semi- *' circular shape to conform to pin 12. In FIG. 26, pin 12 
has an elongated or flattened shape and electrode tip Sa 
on electrode 2u is likewise shaped to conform to this 
type pin. In the WELTEK microwelder, a wide selec- 
tion of materials is available for electrode tips 5 and 7, 
such as molybdenum; the selection of material will de- 
pend upon the particular resistance parameter required. 
Also, tips 5 and 7 do not come shaped from the manu- 
facturer for any particular connector; shaping must be 
An alternate embodiment of the High Temperature 
Solder Device is shown in FIG. 3. In this embodiment, 
all elements remain the same as FIG.  1 except for elec- 
trodes 26 and 46 and their associated shaped electrode 
35 tips 56 and 76. In this embodiment, electrodes 26 and 46 
are held apart by clamps 9, which allows electrodes 26 
and 46 to  be angled towards each other as shown, or 
away from each other as not shown. This configuration 
may prove advantageous for some applications. 
To those skilled in the art, many modifications and 
variations of the present invention are possible in light 
of the above teachings. It is therefore to be understood 
that the present invention can be practiced otherwise 
than as specifically described herein and still will be 
25 
3o done separately. 
40 
45 within the spirit and scope of the appended claims. 
I claim: 
1. A device for soldering multi-pin connectors to thin 
fragile flat ribbon cables having a plurality of conduc- 
tors using high temperaturehigh thermal fatigue sol- 
electrode means having a first half and a second half, 
the tips of said electrode means halves conforming 
to  the shape of said pins of said multi-pin connec- 
tor; 
solder means having a melting temperature above 
200" C. and a high thermal fatigue characteristic 
between said pins of said multi-pin connector and 
said conductors of said flat ribbon cable; 
heat sink means comprising an anvil made from a 
material having high thermal conductivity for sup- 
porting said thin fragile flat ribbon cables having a 
plurality of conductors such that said electrode 
means can apply a downward compressive force 
on said pins of said multi-pin connector and said 
conductors of said flat ribbon cable; 
means for applying a short duration, high density, 
electrical pulse of energy through said solder 
means between said pins of said multi-pin connec- 
50 ders comprising: 
55 
60 
65 
5,126,527 
5 6 
tor and said conductors of said flat ribbon cable 
thereby melting said solder without excessive heat 
and joining said pins of said multi-pin connector 
and said conductors of said flat ribbon cable with- 
Out damage to said thin fragile flat ribbon cable. 
2. The device of claim 1 wherein said means for ap- 
plying a short duration. high density, electrical pulse of 
energy through said solder means comprises a resis- 
tance welding machine. 
3. The device of claim 1 wherein said electrode means 10 
first and second half are separated by a dielectric mate- 
rial between said electrode means first and second half. 
4. The device of claim 1 wherein said electrode means 
first and second half are separated by providing a clamp 
such that said electrode means first and second half may 
be tilted toward or away from each other. 
5. The device of claim 1 wherein said anvil contains 
voids within and for circulating a coolant 
through said voids. 
6.  The device of claim 5 wherein said coolant is wa- 
ter. 
7. The device of claim 5 wherein said coolant is air. 
8. A method for soldering multi-pin connectors to 
thin fragile flat ribbon cables having a plurality of con- 25 
ducrors using high temperature/high thermal fatigue 
solders comprising the steps of: 
on said flat surface \vith said exposed portion of 
said conductors facing upward: 
3) positioning the pins of said multi-pin connector 
above said exposed portion of said conductor in a 
manner such that each pin of said multi-pin connec- 
tor is above a corresponding exposed conductor of 
said flat ribbon cable; 
4) placing a suitable amount of solder having a melt- 
ing temperature above 200" C .  and also a high 
thermal fatigue characteristic between the first pin 
of said multi-pin connector and its corresponding 
exposed conductor; 
5 )  providing a downward compressive force on said 
trode having a first half and a second half. the tips 
of said electrode halves conforming to the shape of 
said pins of said multi-pin connector; 
6) providing a short duration, high density, electrical 
pulse of energy through said solder by sending an 
electrical current down said first half of said eltsc- 
trode and back up said second half of said electrode 
thereby melting said solder without excessive heat 
and joining said first pin of said multi-pin connector 
to its corresponding exposed conductor without 
damage to said flat ribbon cable; 
7) repeating steps 4 through 6 until all pins of said 
multi-pin connector are soldered to their corre- 
sponding exposed conductors. 
5 
means on each first and second half 15 first pin Of said multi-pin connector with an 
20 
1 i providing a heat sink having a flat surface: 
2 )  exposing a portion of the conductors of said flat 
ribbon cable and positioning said flat ribbon cable 30 r * * * r  
35 
40 
45 
50 
55 
60 
65 


High temperature solder device for flat cables

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