CA1260157A - Electrical circuit fabrication apparatus and method - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Wire for repairing or changing circuit elements such as printed circuits has heat-resistant insulation surrounded by a hot-melt adhesive. The wire is attached to the surfaces of printed circuit boards easily by applying a hot iron to the adhesive layer on the wire and melting the adhesive which then adheres to the board surface. The hot iron has a tip with a groove in it so that when the iron tip is pressed onto the wire, the tip embraces the wire to melt the adhesive quickly and to make the bond relatively quickly. The coating is applied by passing insulated wire vertically through a length of molten adhesive and then through a die. A cleaner/holder device is used for cleaning the tip of a hot iron used for melting adhesive, or a soldering iron, and for holding the hot iron when it is not in use. The preferred cleaner is anti-combustion treated absorbent cotton string wound on a spool which is mounted in the holder, or adhesive tape with a soft cloth backing. A
fresh cleaning surface can be provided simply by rotating the spool, or unwinding a layer of the cleaning material and removing it.

Description

`' iL~,6(3~7 FIELD OF THE INVENTION
This invention relates to electrically conductive wire suitable for use as jumper wire for making corrections and changes in electrical cir~uits, and partieularly printed circuit boards.

BACKGROUND OF THE INVENTION
Printed circuit boards often are found to contain errors, or require changes due to improvements in the circuits.
The circuit board changes can be made by changing the art work for the board. However, this can be very expensive. Even if the changes are fairly extensive, often it is far less costly to hand-apply jumper wires in selected locations on the board. The new connections usually are made by inserting one bare end of an insulated jumper wire into a plated hole in ~he board, gluing the wire onto the surface of the board along a predetermined path, and inserting the other bare end into another plated hole. Then the board is passed through a wave soldering bath which solders all of the wires and component terminals in the plated holes.
Alternatively, the terminals can be hand-soldered in place.
The board surfaces onto which the jumper wires are glued most often are coatings of n solder resist" materials, usually epoxy resins. The adhesives used to glue the jumper wires onto those surfaces vary; they include silicone rubber, acrylics, epoxies, and hot-melt adhesives. The adhesives are applied manually. The prior methods of applying adhesives suffer various disadvantages. For example, the wire usually must be held in place for a substantial amount of time to allow for . . .

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sufficient curing or cooling of the adhesive to properly secure the wire to the printed circuit board. Usually this is a time-consuming process and may result in a poor bond if zuficient cooling or curing time is not allocated.
Another disadvantage of prior methods is that they are messy. This increases labor costs for the process due to increased set-up and clean-up time. Also, the prior methods usually are awkward to use. This further reduces worker productivity.
When epoxy adhesives are used, the two components are mixed in a batch which is kept near the work station where it is to be used. The material hardens into a useless mass if it is not used promptly; that is, the material does not have a very long "pot }ifen. This is wasteful, costly and requires additional labor to mix new batches relatively frequently.
Some prior adhesives are toxic or ~ive off toxic fumes when used, thus posing a health hazard to workers and necessitating the use of special safety procedures and/or equipment.

A heating tool used to melt a hot-melt adhesive creates the new problem that the heating tool should be cleaned frequently in order to prevent the build-up of hardened adhesive on it. Cloths can be used to this purpose, but they are relatively slow and inefficient -to use since they must be replaced frequently as the surface becomes covered with waste adhesive, and since a c]ean area on the cloth may take a considerable ]enqth of time to find. A]so, the cloth may smolder or burn due to contact with the iron.

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A cleaning problem similar to that exp~rienced with hot-melt adhesive melting i~ns is found in using soldering irons. Wet sp~nges us~ally are used to wipe the excess solder and flux materials off of the iron tip. However, the sponqe dries out and becomes c~.arred and must be replaced rel3tively frequently, A problem with some jumper wires whi~h have thin coatings of high-temperature-resistant plastics such as polytetrafluorethylene te.g. DuPont "Teflon"*) for insulation is that they are not very resistant to cuts and abrasion. This enda~gers the integrity of the circuits in which they are used.

O ECT OF THE INVENTION
It is an object of the present invention to provide ar~ ,ir~pr~ved wire suitable for use ~s a jumper wire for circui~ ~lel~lents such as printed circuit boardsO

SUMMARY OF THE INVENTION
In accordance with the invention there is provided an electrically conductive wire comprising, in combination, an electrical conductor, a coating of relatively easily s-trippable insulation surrounding the conductor, and a coating of hot-melt adhesive surrounding the insulation. The adhesive is adapted to be activated by the application of a heating tool thereto at each of a plurality of locations along its length so as to cause the wire to adhere to a substantially planar support surface at each of said locations in response to the application of heat from the tool.

* denotes trade mark ; -s~

In one embodiment of the invention, the wire can bepre-cut to desired lengths and the insulation stripped at the ends to form pre-fabricated jumper wires. The pre-fabricated jumpexs also can ~e pre-~ent to a desired shape, thus making them ready to use.
In use, the adhesive-coa~ed wire is electrically connected at its ends to terminals of the circuit element, and the wire is secured to the surface of the element by simply heating and pressing the adhesive coating against the surface.
The adhesive coating advantageously serves the dual purpose of providing a quantity of adhesive convenient to every spot along the length of the wire, while also serving as a protective coating for the relatively thin insulation in the wire.
Prefera~ly, the adhesive is heated and pressed against the surface by means of a heating device such as a hot iron with a tip shaped to straddle the wire and press it against the s~rface of the circuit element.

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The adhesive coating and iron tip are dimensioned so that only a relatively small amount of adhesive is melted by the hot iron, thereby ena~ling the adhesive to be ~elted relatively quickly and harden with similar speed.
In straddling the wire, the hot iron preferably contacts the surface of board to heat it locally. To this end, the hot iron tip, in its preferred form, has an elongated groove which is deeper than the diameter of the insulator layer but sh~llower than the diameter of the adhesive layer.
It is preferred that the melting temperature of the adhesive be relatively high so that there will be a minimum amount o softening of the adhesive bonds of the 3umper wires to the pri~ted circuit board wh~n it is passed thr~ugh a wave soldering device which heats the board significantly. It also is preferred to use a relatively high iron temperature so as to ensure good adhesion of the adhesive to most of the epoxies and other materials used to coat printed circuit boards.
The electrical insulation on the wire should be able to withstand the temperature of the heating device without melting.
Therefore, it is preferred that the insulation be made of a high-temperature-resistant material such as polytetrafluoroethylene (PTFE), (e.g., DuPont "Teflon").
Alternatively, an irradiated, cross-linked polymer such as irradiated cross-linked polyvinyl chloride can be used where condi~ions are not the most severe.
The adhesive coating is applied to the PTFE-coated wire by heating a container o~ the adhesive to a fluid state, and passing the wire through $he fluid material and a die.
Preferably, the surface of the PTFE insulation is etched to improve adhesion of the adhesive coating, and the wire is moved O~
vertically through the fluid container t9 ensure uniformity in the thickness of the ~dhesive coating, The ho~ iron tip cleaning problems are solved by providing a cleaning element with an easily-renewable cleaning surface. The surface can be renewed by simply removing one layer of a layered cleaning element to expose a fresh layer.

The cl~aning element preersble for use with the grooved hot iron tip i one composed of plural strands of fibrous material, preferably of a size to fit into the groove of the iron. Preferably, the cleaning material is wound on a form such as a spool. Ordinary co'Lton stxing comprises an excellent and inexpensive ~tranded fibrous materialO It is simply wound on the spool, and unwound to expose a fresh layer when needed.
Alternatively,. especially for cleaning soldering irons, the cleaning surface comprises a roll of cloth tape with a pressure-sensitive adhes~ve backing which ~s simply peeled of~ of the roll and torn off to expose a fresh su~face.
A combination iron holder and iron cleaner also is discl.ose~ herein.
If it is desired to dampen the cleaning material with water, a water seservoir is provided in which to store water in contact with the cleaning material.
The cleaning material is trea~ed with a combustion retardant to prevent the material from burning or sm~ldering due to contact with a hot iron.
Various o~her objects, advantages, and fea~ures of the present invention will be described in or will become readily apparent from the following detailed description and drawings.

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In the drawings:
~ igure 1 is a perspective view of an insulatedelectrical wire embodying the present invention;
Figure 2 is a side elevation view of a heating device for use with the wire of Figure 1;
Figure 3 is a schematic perspective view illustrating of the use of the wire of Figure 1 and the heating device of ~igure 2 to repair a printed circuit board;
Figure 4 is an enlarged side elevation view of the tip of the heating device of Figure 2 being brought into contact with the wire of Figure l;
Figure 5 is a side elevation view similar to Figure 4 after the tip of the heating device has been removed from the wir-e;
Figures 6, 6A and 6B are, respectively, enlarged side elevation, bottom plan, and end elevation views of the preferred embodiment of the tip of the heating device of Figure 2;
Figure 7 is a cross-sectional view of the tip of the heating device of Figure 6 shown as it melts the adhesive which coats the electrical wire of Figure l;
Figure 8 is an enlarged perspective view of an alternative embodiment of the tip of the heating devi~e of the invention;
Figure 9 is an enlarged side elevation view of the tip of Figure 8 being brought into contact with the wire of Figure l;
Figure 10 is an enlarged side elevati~n view of an alternative embodimen~ of the tip of the hea~ing device of the invention being brought into contact with the wire of Figure l;
Figure 11 is a 6ide elevation view similar to ~hat of ~igure 9 showing the tip of Figure 10 after it has been pressed ` ~'6015~
against the wire of Fig~re 1 and then removed;
Figure 12 i5 an enlarged view of an alternative emb~diment of the tip of the heating device of the inven~ion;
Figure 13 is a bottom plan view of the device shown in Figure 12;
( Figure 14 is a schematic perspective of the equipment used for coating insulated wire with a hot-melt adhesive outer ~oating;
Figure 15 shows graphs plotting the viscosity versus temperature for two hot-melt adhesives used to coat ~he wire of the inven ion;
Figure 16 is a perspective view of one embodiment of a device for holding and cl aning a heating device tip in accordance with the present invention;
Figure 17 is a cross sectional view taken along line 17-17 of Figure 16;
Figure 18 is a perspective view of an alterna~ive heating device holder/cleaner device;
Figure 19 is a cross sectional view taken along line 19-19 of Figure 18;
Figure 20 is a partially schematic cross-sectional view of the cleaning action of the cleaning device of the invention;
Figure 21 is a cross-sectional view of another embodiment of the holder/cleaner device, and Figure 22 is a perspective view of a material used in the device of Pigure 21.
GENERAL DESCRIPTION
___ Figure 1 shows the s~ecial jumper wire 10 of the present invention. The wire 10 includes an inner conductor 12, a coating of insula~ion 1~, and a coating of hot melt adhesive 16 over the insulation 14.

Figure 2 shows an electrical heating iron 19, like a ~%6~5~

soldering iron, with a handle 17, a receptacle 18, an electrical heating element ~6, and a ~pecially-shaped ~ip 23. As it is shown in Figures 6 and 7, the tip 23 is flattened to give it a shape like a screwdriYer blade. The lower edge of the tip has an ~longated groove 41 (Figures 6-6B) to fit over the outside of the wire 10 so that the iron tip embraces the wire, and the sides 44 of the tip on oppo~ite sides of the groove 41 straddle the wire as shown in Fiyure 7 when the tip is pressed down on top of the wire.
In Figure 3, a jumper wire 11 having the structure of the wire 10 in Figure 1 and the heating device 19 of Figure 2 are shown in use for repairing or changing a prin~ed circuit board 28.
First, i the jumper wire 11 has not been pre-cut to the proper length, one end of the wire 10 is stripped of insulation, bent over, and inserted into a plated hole 25 in the board 28. Then the heated tip 23 of the device 19 is pressed down onto the wire 10 near the hole ~5, held there for a second or two, and released. The wire then is bent to form corners 13 and 15, and the hot iron 19 is used again in the same way at appropriate points along ~he wire to secure it to the surface of the board 28. Then, when the correct length of ~he jumper wire has been determined~ the wire is cut, and the remaining end is stripped of insulation, bent over and inserted into another plated hole 27. Then, the jumper wire ends are soldered into the holes 25 and 27 by the use of a soldering iron or gun, or preerably, in a wave soldering device which solders all of the junctions on the board 28 simultaneously.
If the jumper wire 11 has be~n pre-cut to the proper length and its ends stripped before use, the stripping and cutting ~teps described above are not necessary. Also, the bends of the wire at 13, 15 and at the ends of ~he jumper wir~ can be pre-formed by the use of bending dies. Then ~he user need only apply and attach the wire ~o the board.

_g _ Portions of printed con~uctors on the board 28 are shown at 29, 31 and 33~ ~he conductors 29 and 31 make electrical contact with the jumper wire 11 at the plated holes 25 and 27.
However, the jumper wire 11 crosses over the conductor 33 and others like it without making electrical contact, both because of the insulation on the wire, and because of the insulating epoxy ~older-resist coating over at least some of the conductors on the board.
The iron tip 23 heats and very quickly melts the hot-melt adhesive 16, which flows in the manner shown in Figure 7, and adheres to the surface of the printed circuit board 28.
Some of the adhesive cools quickly to form a bond~ Then, after being held in place briefly, the iron tip 23 is xemoved and the remaining melted adhesive cools, forming a solid adhesive bond between the wire and the board surface.
The jumper wire process and equipment described above are quick and easy to use, and h ve other advantages which will be discussed in the detailed description which follows.
DETAILED DESCRIPTION
A. Wire Structure The wire 10 shown in Figure l includes an inner conductor 12 which, for example, may be a .~10 inch diameter copper wire. It may have a very thin (.0002-.0005 inch) electroplated coating of silver on the outer surface.
In order for the insulation 14 to be able to withstand the high temperatures it will be subjected to during ~he use of this invention, the insulation is preferably i~ a thermoset, heat resistant polymer material. Preferred materials are hea~-resi~tant materials such as polytetrafluorethylene ~PTFE~ and may include irradiated cross-linked poly~inylchloride and polyethylene. Such an insulation layer 14 is typically about .005 inch thick, and in the preferred ~ 5~

embodiment its suter surface is etched chemically, e.g. by a caustic chemical solution, in order to promote adhesion between it and the adhesive 16. The thickness of insulation layer 14 is preferred to be approximately 45% to 55% of the diameter of conductor 12.
(~ The hot-mel~ adhesive layer 16 should be just thick enou~h ~o supply enough melted adhesive to make a good bond. For example, an adhesive thickness of about .005 inch thick, that i5, one approximately equal to the thickness of the insulation layer 14, is preferred. For reasons discussed below, a preferable hot-melt adhesive is l'Hysol" brand type XPA-1245 or type 7901.
Both materials are polyamides sold by the Dexter Corporation.
B. Heatin~ Device The heating device l9 illustrated in Figure 2 may be a conventional soldering iron but with the typical pointed soldering tip replaced by the special tip 230 The device of Figure 2 may be used to help rout~ ~he wire by pressing the hot tip again~t the wire near a desired bend to fasten the wire to the board at the point of contact. As the iron is used to hold the wire down, it is bent at the contact point of the iron tip to ~he board 28 to change the direction of the wire. This is desirable because bending ~nd fastening of the wire are done in the same step.
The preferred tip 23 is illustrated in Figures 4 through 7. As it is shown in Figure 6, the tip preferably has ~crew threads 35 at one end and is threaded into a threaded hole in the receptacle 18 (Figure 2). Therefore, the ~ip 23 may be used in conjunction with many different types of irons such as ~oldering irons which use replaceable tips. The tip 23 is elongated and relatively thin at its lower end so as to facilitate acce~sibility to ~he printed circuit board 28 in areas eongested with many c~mponents and/or conductors.

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The tip ~3 is cylindrical at its upper threaded end 35 and tapers outwardly i~ the dimension shown in Figure 6, and tapers inwardly in the dimension shown in Figure 6B. The angle O
of taper is approxima~ely four degrees.
As it is shown in Figure 6, the metal at each end of the groove 41 is cut away to form rounded edges 37. This enables one to tilt the tip 23 sideways while using one of the rounded edges 37 as a pivot, thus holding the wire down and allowing one end of the mel~ed adhesive area to cool and harden faster than if the iron tip were held in contact with the wire over the full width of one tip. ~he rounded edges 37 prevent the metal from digging into the insulation 14 on ~he wire, The depth of the groove 41 preferably is between 65%
and 85% of the total diame er of the wire 10 with the adhesive coating intact, and is a~out equal to the diameter of the insulated wire plus the thickness of the adhesive coating. The groove 41 forms ridges or legs 44 (Figure 7) with bottom edges 43 (Figure 6~.
When the hot iron tip 23 has melted through the adhesive 16, the bottom edges of ~he ridges 44 abut against the epoxy "solder-resist" coating 47 on the printed circuit board 28, as it is shown in Figures 4 and 7. ~his creates some hea~ing of the board material so as to enhance adhesion~ The tip 23 is shown in Figure 7 with melted adhesive which has spread outwardly from the ridges 44 as indicated at 45. This spreading action is believed to enhance rapid cooling and hardening of the adhesive.
The preferred range of temperatures for ~he tip 23, when using Hysol XPA adhesive is from around 550F. to 650F. A
temperature of approximately 600~. is preferred.

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The iro~ need be applied for only one or two seconds,in most cases. One reason for such speed, it is believed, is that the mass of the melted adhesi~e is small relative to the mass usually used with prior methods. The coating of adhesive is just thick enough ~o ensuxe that ~he ~paces between the ridges 44 (;~nd the wixe 10 are illed, or a little more than filled, with adhesive. Another rea~on, it is believed, is that the bond extends over a relatively long section of the wire and thus covers a substantial area so that the holding power of the adhesive quickly becomes adequate to secure the wire to the board without being held dow~ so that the iron can be removed to allow the adhes.ive to further cool and harden rapidly.
An alternative tip 22 for the heating evice is shown in Figures 10 and 11. ~he tip 22 is cylindrical in shape and is surrounded by a coil spring 24 which can be used ~o press the wire against ~he prin~ed circuit board before, during, and after melting of the hot-melt adhesive in the unusual circumstances in which the foregoing arrangement does not give fast enough cooling of the adhesive. The spring 24 is fixed at one ena ~o the heating element 26 (Figure 2) of the heatin~ device 19. At its opposite end, the spring extends beyond the end of ~he tip 20 As it is shown in Figure 11, the spring 24 presses the wire 10 downwardly against the printed circuit board 28. As the heating device 19 is pushed downwardly further, the spring 24 is further compressed so that the tip 22 is pressed against the wire to heat a local region of the adhesive layer 16.
After the adhesive has been meltedl the heating device 19 is lifted slightly from the wire 10, as shown in Figure 11, so that the tip 22 is lifted ~rom the wire, but the spring 24 continues to hold the wire against the printed circuit board 28.
This allows time for cooling and setting of ~he adhesive 16 without allowing the wire to spring upwardly and pull free of the ~ ~ ~0~5 7 circuit board 28.
Another tip 3~ of the heating device 19 is shown inFigure 8~ The tip 32 includes three h~mispherical feet 34. As it is shown in Figure 9, the~e feet allow the tip 32 to straddle the wire 10 as it is pressed against the printed circuit board 28. The feet also serve to position the tip properly ~ver the wire 10 during the bonding process.
Another tip 40 for the heating device 19 i~ shown in Figures 12 and 13. The tip 40 is substantially the same as the tip 23 described above. One end Inot shown) has threads and is threaded into a hole in a hexagonal body membex 38 which is, in turn, threaded into the heating element of the device.
The tip 40 has a concave, cylindrical groove in it.
The groove 42 separates elongated ridges 44 which serve as legs which s~raddle ~he wire 10 as the ~ip is pressed against the printed circuit board 28. As with the preferred embodiment of Figures 6 and 7, the tip 40 straddles the wire 10 and presses against the prin~ed circuit board 28 o locally heat the board for a better bond. The spring 24 is not required. The groove 42 is alig~ed with two corners of the hexagonal member 38. This assists in the orientation of the groove 42 with the wire by giving the user an alignment reference plane.
C. Adhesive Material The temperature of the usual wave solder bath is around 500F or a little higher. In the usual wave soldering process the bath metal brief touches only the bottom side of the printed circuit board - the one without components attached. However, portions of the upper side of the board sometimes reach temperatures over 300F. Therefore, in order to prevent the jumper wire from coming loose during wave soldering, the melting tempera~ure of the adhesi~e should be as high as possible, but at leas~ 300F to 350F. ~ccordingly, the ~wo preferred adhesives 6(~i7 for use in this invention are those having the hiqhest meltingpoints and having the ability to adhere to glass-filled epoxy printed circuit board surfaces and epoxy solder-resist coatings.
The approximate viscosity-temperature curves of the preferred Hysol adhesives used in the present invention are illustrated in Figure 1$. Both are seen to be adva~tageous in that the viscosity is relatively high at temperatures just below the "melting point~ temperatures. The melting point of the Hysol 7901 adhesive, as determined by the standard "ring and ball" test specified in ASTM E28-67 t is around 340F. The mel~ing point of the XPA 124S adhesive, using the same procedures, is approximately 392F. The XPA 124~ material i5 preferred because of its higher melting point and its higher viscosity at temperatures above the melting point~ Bowever, adhesives with e~en higher melting points, say, up to 550F, are even better.
The maximum melting point temperature of the adhesive is not particularly critical. Howeverl it has been found that an iron tip temperature o at least 500 to 650D should be used in order to obtain an adequate chemical reaction between the adhesive and certain epoxy resins used as so]der-resist ma~erials to ensure a good bond. Although higher iron temperatures can be used, this can cause problems. Therefore, a melting point below 550F is preferred.
It should be pointed out that the viscos~ty-temperature curves of Fi~ure 15 are only estimates, and that the actual values may differ significantly from those shown. Therefore, the "melting point" for each material, which is fairly well defined, 6hould be used as the most reliable measure of the holding power of the adhesive at elevated temperatures.

6(~57 D Adhesive Coatin Process .~
Figure 12 sh~ws machine 48 used for coating the wire 10of Figure 1 with hot-melt adhesive. The adhesive-free wire 60 preferably has PTFE-insulation which is etched in a causkic chemical solution to promo~e the adhesion of the adhesive layer 16 to the insulator layer 14. Any of several caustic chemical solutions known in the art may be used for the etching process.
The coating machine 48 consists essentially of a take-up reel 74 driven by a variable speed motor (not shown), a supply reel 58, a melting pot 50 with an adhesive supply reservoir 52 and a die 66 through which the adhesive-free wire 60 passes in a vertical direction.
The adhesive is placed in pellet form in the melting pot 50 and is melted by an electric heater which is part of the melting pot assembly. The melted adhesive is stored in the adhesive supply reservoir 52 at a constant temperature of around 400~F, which is monitored by means of thermocouple 54. Reservoir 52 also serves as the coating chamber. Ni~rogen gas is fed into the melting pot 50 ~hrough a tube 56 to minimize the oxidation of the molten adhesive.
The adhesive-free electrical wire 60 is mounted on the supply reel 58 and routed over a guide puiley 62 to the adhesive supply reservoir 52. The wire 60 passes upwardly through a guide 64 into the reservoir 52 where i~ is coated with molte~ adhesive.
The wire 60 then exits the reservoir 52 through the die 66 which is provided to determine the thickness of the adhesive layer on ~he wire.
The orifice size of ~he die 66 is adjust~ble to vary the thickness of ~he adhesive and to accept various sizes of wire.

~0~7 After coating, the wire 10 travels a distance sufficient to allow the adhesi~e to harden. The distance L
depends on the thickness of the adhesive, the ~peed of the wire, and the ambient air temp~rature, among other things. The wire 10 then is routed over a precision pulley 70. The pre~ision pulley 70 is integral with a counter mechanism 71 which counts the number of revolutions of the pulley 70 in order to measure the length of wire coated.
The wire 10 then passes over a level-winding pulley 72 and i5 level~wound on the ta~e-up reel 74. The reel 74 is driven at a variable speed and pulls the wire 10 through the coating machine 48 at a relatively constant speed.
By ~oving the adhesive-free wire 60 vertically rather than horizontally through the die 66, unevenness of the adhesive coating due to the effects of gravity are avoided. The result is an even adhesive coating economically applied.
E. Ti~ Clean ng A device 76 for cleaning the tip of ~he heated iron 19 is shown in Figures 16 and 17~ The device 76 also serves as a holder for the heating iron.
The cleaner/holder device 76 has a frame made of aluminum or other suitable metal. The fram~ comprises a single sheet of metal forming a base plate 78 and an upwardly-bent end portion 82, a eleaning device 79, and an iron holder 88 secured to the base plate at one end by means of a bolt and washer combination 89. The cleaning device 79 includes a form or spool 80 into which is wound several layers of an elonga~ed fibrous ma~erial such as cotton string.
The spool 80 i5 wedged between the tapered helical spring forming the iron holder 88 and the upper edge 85 of the end-portion 92 of ~he base to releasably hold the spool in piace ~L~ 6015~
so that the iron tip 23 can be wiped across the cleaning surface84 formed by the string wound on the spool 80.
The spool B0 has a cylindrical ~ore and flanges 92 to hold the string wound in it in place. The spool 80 can be an ordinary ~ishing-line spool, for example. It is hsld by tabs 83 at the ends of the upper edge 85 of the end portion 82.
The cotton string preferably is treated with a combustion-retardant solution A suitable solution consists of 2~ borax and 2% boric acid by weight dissolved in water The cleaning process is shown in Eigures 17 and 20, as well as Figure 16. The tip 23 is moved over the cleaning surface 84 in a direction 87 (Figure 17) in which the groove 41 is aligned with the strands 106 of the string as shown in Figure 20, so as to allow the strands 106 to enter the groove 41 of the tip 23 to clean out any residual adhesive. The bottom edges 43 of the ridges 44 and the outside surfaces of the ridges are also cleaned by adjacent strands of stringO
Of course, the surface 84 also can be used to clean other adhesive melting iron tips such as thoses illustrated in Figures 8 through 13, regardless of the shape of the tip.
In accordance with the present invention, a fresh cleaning surface can be exposed by means of one of two alternative methods. First, the spool 80 can be rotated a little to expose a clean portion of the surface 84. When there is no more clean area, the second method can be used; namely, unwinding the string on the spool until a fresh layer of string has been exposed. Either method is simple and quick.
Other cleaning surfaces ran b~ used. For 0xample, Figure 21 shows a cleaning surface ~ormed by a roll 97 of adhesive tape which has a relatively soft, absorbent cloth backing. When a clean wiping surface is needed, the user can ~18-6~L57 either r~tate the sp~ol 80, or the user can peel off all or parto~ one layer of tapP 97. The upper front edge 85' of the ~ase portion is sharpened and/or serrated to facilitate cutting off a length of tape.
Figure 22 is an enlarged section of the tape 97 of Figure 21. The adhesive material is shown at 99 and the soft cloth backing at 101. A tape of the type described is so-called ~athletic" tape which is used to wrap ankles~ knees and other parts of athlete'~ bodies for support purposes~ Since the adhesive tape 97 needs the adhesive primarily to hold the roll together without unwinding, tape with a relatively weak adhesive may be used. The cloth 101 should be treated with fire-retardant materials of the type described above.
It is believed that the embodiment of the invention shown in Figures 21 and 22 is especially 6uitable for cleaning the tips of soldering irons. If the adhesive melting iron of Figures 2-7 is to be cleaned using the tape form of cleaning surface, ~he groove in the iron tip can be clea~ed especially well if corduroy cloth is used for the tape 97. The ridges of the cl~th preferably extend circumferentially around the roll, and the tip 23 can be wiped against the cloth in the direction shown by arrow 87 in Figure 17 to clean out the groove in the tip.
It is believed by many that a cleaning surface for ~oldering irons sh~uld be wet in order to do the best cleaning.
Accordingly, a water reservoir 93 is mounted on the base plate 78 (Figure 17) ~or the roll of string 80 ~o be immersed in. The string will stay wet all the way around as water i~ absorbed from the reservoir 93 into all fibers of the string. The same kind of 6~S~

reservoir 93 also can be used with the tape of Figure 21. As desired, the fire-retardant chemicals can be added to the water in the reservoir 93, if desired, rather than soaking the string before the spool of string i8 mounted on the base plate 78.
If desired, water in the reservoir 93 can be replenished automaticallv by use of any of a multitude of known water repleni~hmen~ devices, such as those used to water pets, chickens~ etc. Water can be added by such means through an inle~
tube 9S.
An improved cleaner/holder device 94 is illustrated in Figures 18 and 19. The device 94 has a frame consisting of a single aluminum shee~ punched and bent to form a generally U-shaped structure. The frame has a lower base portion 96, an angled front portion 100, and a top portion 98. The top portion 98 has a re~tangular hole 102 which is slightly wider than the lensth of the spool 80, but whose other dimension is slightly smaller ~han the diameter of the flanges 92 of the spool 8~. The weight of the spQol forces the edges sf the flanges 92 against the edges of the hole 102. This acts as a brake to hold the spool in place while an iron tip is being wiped across its surface 84.
The front portion 100 of the frame has a circular hole into which an elongated cylindrical bushing 86 is fitted.
Bushing 86 is constructed of a heat-resistant material and, as it is shown in Figure 19, is secured in place by circular retaining clip 104. Bushing 86 serves ~s the holding device to hold the heating device 19 when it is not in use.
As with the embodimen~s shown in Figures 16, 17, 21 and 22, a water reservoir g3 can be provided to keep the cleaning surface damp. Also, ~he tape form of the cleaning surface shown 6Q~L57 in Figures 21 and 22 also can be used with the holder shown inFigures 18 and l9, Each of the embodiments shown in Figures 16-21 has rubber feet l~ on the base plate to keep the device from slipping on a surface on which it rests while a hot iron is being pushed against the cleaning spool 800 While the presen~ invention has been particularly shown and described with reference to preferred embodiments, various changes and modifications in form and details may be made without departing from the spirit and s~ope of the invention. It is intended that the appended claims be interpreted as including the foregoing as well as various other changes and modifications.

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Claims (22)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An electrically conductive wire, said wire comprising, in combination, an electrical conductor, a coating of relatively easily strippable insulation surrounding said conductor, and a coating of hot-melt adhesive surrounding said insulation, said adhesive being adapted to be activated by the application of a heating tool thereto at each of a plurality of locations along its length so as to cause said wire to adhere to a substantially planar support surface at each of said locations in response to the application of heat from said tool.

2. A wire as in Claim 1 in which said insulation is made of polytetrafluoroethylene with a higher melting point than that of said adhesive.

3. A wire as in Claim 1 in which said support surface is an epoxy resin surface of an electrical printed circuit board.

4. A wire as in Claim 1 in which said adhesive is a polyamide resin with a melting point of from approximately 300°F to approximately 550°F.

5. A wire as in Claim 1 in which said adhesive has a melting point of from approximately 375°F to 400°F.

6. A wire as in Claim 1 in which the thickness of said adhesive coating is approximately equal to the thickness of said insulation.

7. A wire as in Claim 1 in which the thickness of said adhesive coating is approximately sufficient to fill the interstices between said insulated wire and said planar surface when an applicator which straddles and envelops said wire is applied thereto.

8. A wire as in Claim 1 in which said conductor has a relatively thin coating of silver coating it substantially completely, with said insulation coating covering said silver coating.

9. A pre-fabricated jumper wire, said jumper wire comprising, in combination, a length of wire, pre-cut to a desired dimension, said wire having an inner conductor and a coating of relatively easily strippable insulation which is stripped away at at least one end of said wire, and a coating of hot-melt adhesive surrounding the remaining insulation on said wire, said adhesive being adapted to be actived by the application of a heating tool thereto at a plurality of locations along its length to cause said wire to adhere to a substantially planar surface.

10. A jumper wire as in Claim 9 in which both ends of said length of wire have the insulation stripped away, and said wire is pre-bent to a desired shape so as to follow a desired path when attached to said planar surface.

11. A wire as in Claim 9 in which said insulation made of polytetrafluoroethylene with a higher melting point than that of said adhesive, and in which said adhesive is a hot-melt polyamide adhesive material.

12. A wire as in Claim 9 in which said conductor has a relatively thin coating of silver coating it substantially completely, with said insulation coating covering said silver coating.

13. A wire comprising an electrical conductor, an electrical insulator layer surrounding said conductor, and a hot-melt adhesive coating surrounding said insulator layer for bonding said wire through heating to a non-adhesive surface, in which said insulator layer is polytetrafluorethylene (PTFE) which has been etched in a caustic solution to promote adhesion with said adhesive layer, and in which said adhesive layer has a lower melting point than said insulator layer.

14. A wire as in Claim 1 in which said adhesive layer has a melting point between approximately 300°F and 550°F.

15. A wire as in Claim 13 in which said adhesive layer has a melting point between approximately 340°F and 400°F.

16. A wire as in Claim 13 in which said conductor has a relatively thin coating of silver coating it substantially completely, with said insulation coating covering said silver coating.

17. A wire as in Claim 13 in which said adhesive layer has a thickness approximately equal to the thickness of said insulator layer.

18. A printed circuit board having a non-printed electrical wire interconnector thereon, the wire interconnector comprising an insulator layer surrounding a conductor and a hot-melt adhesive layer surrounding the insulator layer along substantially its entire length, the conductor being electrically connected to the printed circuit board at its ends and mechanically coupled to the printed circuit board between its ends by the adhesive layer.

19. A printed circuit board as claimed in Claim 18 in which said conductor has a relatively thin coating of silver coating it substantially completely, with said insulation coating covering said silver coating.

20. A printed circuit board as claimed in Claim 18 wherein the adhesive layer has a melting point of between approximately 300°F and 550°F.

21. A printed circuit board as claimed in Claim 18 wherein the conductor is electrically connected at its ends by solder.

22. A printed circuit board as claimed in Claim 18 wherein the insulator layer is a thermoset material.