Patent Publication Number: US-3874068-A

Title: Wave soldering electrical connections

Description:
1451 Apr. 1, 1975 1 WAVE SOLDERING ELECTRICAL CONNECTIONS [75] Inventor:  
 [73] Assignee: Dynamics Corporation of America, New York, NY.  
 [22] Filed: Mar. 2, 1973 [21] Appl. No.: 337,386  
 Related US. Application Data Lawrence E. Cook, Meriden, Conn.  
 [60] Division of Ser. No. 219,036, Jan. 19, 1972, Pat. No.  
 3,765,591, which is a continuation-in-part of Ser. No. 138,651, April 29, 1971.  
 [52] US. Cl 29/47l.l, 29/481, 29/503, 228/37 [5 l] Int. Cl B23k 31/02 [58] Field of Search 29/471.1, 484, 503, 481; 117/113, 114 R; 228/36, 37  
 [56] References Cited UNITED STATES PATENTS 1,478,696 12/1923 Boehme 228/31 2,776,640 l/l957 Miklofsky ct al. 228/36 UX 3,482,755 12/1969 Raciti 228/37 X 3,502,787 3/1970 Reach et a1 29/471.1 X 3,536,243 10/1970 Higgins 228/36 X 3,589,590 6/1971 Fitzsimmons 29/503 3,673,681 7/1972 Steranko 228/5 X Primary E,\&#39;aminer-Francis S. Husar Assistant Examiner-Robert J. Craig Attorney, Agent, or Firm1-larbaugh and Thomas [57] ABSTRACT Wire connectors are wave soldered to a terminal by moving mechanically connected insulated wire and depending terminal connectors in a fixed plane progressively through a flux bath and then through a bidirectionally flowing molten solder bath for a time-heat cycle effective to burn off the insulation and solder bond the elements. The work pieces may be moved in a circular path or moved along a guiding divider which shields the remaining parts of the work piece from flux splatter in a clean cooling dispersing atmosphere or a blast of cooling air may be used to scavenge and return to the bath surplus molten solder from the soldered elements as they leave the bath.  
 11 Claims, 10 Drawing Figures WAVE SOLDERING ELECTRICAL CONNECTIONS RELATED APPLICATION This application is a division of application Ser. No. 2l9.036 filed Jan. I9, 1972 now US. Pat. No. 3,765,59l which is a continuation-in-part application of application Ser. No. 138,651, filed by the same inventor, Apr. 29, 1971.  
 BACKGROUND OF THE INVENTION Heretofore electrical connections have been soldered under conveyor conditions in which relative movement has been required between a work piece and molten solder to dispose the solder and the work piece in a proper dip relation. A preheating of the work piece has generally been employed ahead of a solder dip to bring bare uninsulated metal parts up to predetermined temperatures. Where relatively moving molten solder has been employed as a dip the flow is restricted to a small exposed area and must have a mild upward component of movement of solder generally towards the connection whereby solder cannot contact the work piece other than the metal parts to be soldered. Even then care must be taken to prevent over-spread and the undesirable contacting of other parts. Conveyors are usually momentarily stoppped, or make a quick vertical excursion for an adequate operation to provide a soldered joint.  
 SUMMARY OF THE INVENTION The present invention is characterized by a molten solder pot that is elongated in the direction of planar movement of a continuous conveyor which preferably is either a turning wheel having work carriers at the ends of spokes where work pieces are carried by a fixture. or. an endless conveyor along a rectilineal track as closely grouped as desirable where the work pieces have carriage parts below the level of which the solder joints depend.  
  Thermostatically controlled heated solder is moved at a substantially high rate from the heater upwardly at the horizontal center of the pot to establish the hottest point of the solder preferably at the horizontal center of the pot. From there the flow preferably divides itself into two currents continuously flowing substantial distances in opposite directions essentially in alignment with the path of movement of the work piece on the conveyor. The two currents spill over weirs at the opposite ends of the pot at a depth and with agitation great enough: (1) to heat the mechanically secured parts; (2) burn the insulation from any insulated wire ends; (3) solder bond the two parts; (4) solidly interconnect wire ends with solder in small apertures of thin wall terminals; and (5) wash away dross and debris to keep the surface of the solder substantially clean since there are no corners in which dross can collect.  
  The current of solder flowing in one direction flows towards the approaching work pieces and rapidly heats each successive work piece regardless of their frequency with increasingly hotter molten solder until the center of the pot is reached where the hottest portion of solder burns away the flux coated insulation to bare &#39;clean metal for direct contact by the flux without contamination by dross or air. The flux required to bond the solder to the clean metal stripped of insulation in the bath is very little and enough flux for that purpose LII preferably is supplied by a preliminary light bubblebath of low viscosity.  
  With the solder flowing in the opposite direction from the center of the pot; the work piece moves with it and retains sufficient solder to hold the wires solidly and rigidly in place. In one embodiment where the ter- -minal is made of substantial thickness of metal having high electrical conductivity an air blast, which in operation happens to have a cooling effect upon the work piece and the solder bath, is employed to scavenge the excess molten solder from the work pieces as they leave the exit spillway. The air blows the scavenged excess back into the body of the spillage. The remaining bonding solder is quickly hardened before undesirable temperatures can be built up in the remaining structure of the work piece. Thus the blast of air operates in part to keep down the temperature of the remaining structure of the work piece while the electrical joint is being soldered and then scavenges and chills it. Where depending work piece parts may be contacted by flux fumes or splatter they are shielded and subjected to a moving clean atmosphere which disperses fumes and splatter.  
  Mechanical surface skimmers can be carried by the conveyor to keep the surface of the solder brighi and clean throughout its exposed area, but it has been found that the high volume flow that is adequate to raise the solder level well above the weirs as much as one-half inch, along with the movement of the work piece itself, provides an action that is generally enough to keep the surface of the solder adequately clean.  
  The invention is characterized by eliminating the need for a conventional preheat flame ahead of or be tween a fluxing station and the soldering station, and, along therewith also eliminates an extra expense of prestripping the connector wire of insulation for use at the connector joint.  
  A further object of the invention is to eliminate all mechanisms and operations requiring relative vertical movement between the solder pot and the work piece whereby speed and cooperation are accomplished with continuous conveyor movement preferably in a single horizontal plane, and preferably with a simplified apparatus whose only movable parts are essentially a turntable with fixtures for loading and unloading work pieces at a single station or a track along which loose work pieces are moved, a hot solder pump, means for providing enough air for a shield or scavenging blast or both, and low pressure air for the flux bubbler, all of which once adjusted and running requires little if any further attention.  
  A further object of the invention is to provide currents in a solder pot that are fast flowing in opposite directions from the center in which the unidirectional conveyance of the work piece has hot solder flowing towards it to increase the effective heat supply and exchange contact therebetween while heating up the work piece and assuring the burning of the insulation as it passes throuogh the upward flowing stream of hottest solder. Thereafter the work piece is moved downstream with the opposite current towards the cooling air blast which scavenges excess solder back into the spillage as the work piece leaves the solder and before the soldered joint hardens, and may be passed rapidly through more than one solder bath to assure adequate soldering without unduly heating the remainder of the work piece parts.  
  Various other andifuirther objects and advantages will appear from the description and claims which follow as related to the drawings in which:  
  FIG. I is a perspective of the complete soldering machine embodying tlfte invention;  
  FIG. 2 is a diagra jrnmatical illustration of the fluxing device and movemejlnt of the work piece with respect thereto; and  
  FIG. 3 is a diagraiinmatical illustration of the solder pot illustrating the operation and flow of the solder and air blast in the invention;  
  FIG. 4 is a perspective view of another embodiment of the invention involving a rectilineal feed with work pieces moved along guide tracks that support and shield the uninvolved piece parts;  
 FIG. 5 is a section taken on line 5-5 in FIG. 4;  
 FIG. 6 is a sectioii taken on line 66 in FIG. 5;  
  FIG. 7 is a longittidinal section taken on line 7-7 in FIG. 4 at one side of the work piece guide;  
  FIG. 8 is a longitudinal section similar to FIG. 7 but taken between the tracks of the guide;  
  FIG. 9 is a section taken on line 9 of FIG. 6 showing a bare wire connection; and  
  FIG. 10 is a view-similar to FIG. 9 showing an insulated wire make upjwith an eyelet connector.  
 DESCRIPTION PREFERRED EMBODIMENT As shown in FlG. l, the invention contemplates fluxing and soldering electrically conductive work pieces rotatively at successive stations indicated by the devices at 10 and 12, respectively. The devices are mounted on a work table 14 and are arranged preferably in a circular path that is transcribed by coplanar fixtures 16 carrying the work. The fixtures are located on the end of the spokes 18 of a turntable wheel 20 supported on a verticalshaft 22 that is rotated in the direction ofthe arrow 28&#39; by the motor 24 through the transmission 26 as later described herein. In event that more than one work piece 30 are at soldering stations at one time, a rectilineally moving conveyor may be employed to provide a heat-time constant for all work pieces.  
  The work pieces 30 that are carried by the fixtures are illustrated by an assembled component of universal motors in which insulated magnet wire 32 is wound in place beteen dielectric end members 34 that carry connector terminals 36 along their lower peripheral edges abut which the field-tap wire-loops 38 are quickly tied mechanically during the winding operation without need for stripping their plastic insulation.  
  The work pieces are secured to the fixtures with the lugs depending and disposed in a common plane to move successively from the feed station at 40 horizontally through the flux device 10 and then through the soldering station 12 to the piece discharge station 42 to solder the loops 38 to the lugs 36 in electrical conductive relation.  
  The work clearance levels of the two devices 10 and 12 as indicated at 44 are substantially the same so that the planar movement of the coplanar work pieces is devoid of any vertical excursions. Thus embodiments of the invention are greatly simplified.  
  The liquid flux and molten solder components being amenable to the passage of solid objects through them, their working levels areraised above the level 44 quite substantially for the tied wire loops 38 and the terminals 36 to freely pass therethrough and be coated thereby.  
 Fluxing Station For this purpose the fluxing device 10 illustrated in the embodiment shown comprises a central container 50 extending to the level 44 and having replenishing holes 52 in the bottom covered by a sintered metal porous disk 54. An overflow catch basin 56 surrounds the container 50 and the holes 52 permit the liquid levels to seek to equalize in the container and basin.  
  A flux reservoir 62 surrounds the bottom of the basin 56 where soldering flux having a vaporizing temperature higher than that of the wire insulation is heated by an electric heater 68 to a constant liquid viscosity as controlled by an adjustable thermostat 64. The bottom of the basin is in communication with the reservoir through openings 66, and with the container 50 through openings 52.  
  A source of air under pressure is introduced to the container 50 by the conduit 58 as controlled by a flow adjustment valve 60 and a porous disk 54, preferably made of sintered powder stainless steel or bronze, is located in the bottom of the central container 50 over the openings 52 and conduit 58. The disk is preferably provided with 25 micron openings and with the replenishing flux moving therethrough along with the air. the comminuted air operates to convert the liquid flux in contact therewith into foam indicated at 70 in the central chamber 50 above the disk as both are broken up into minute units. The air present levitates the foam bodily.  
  An advantage of the embodiment illustrated arises by being able to provide an optimum coating and to minimize the dross which will occur at the solder station. Given equal liquid levels, preferably low. in the relationship described, the minute air bubbles leaving the disk at the start will foam the flux above it to a predetermined height but the weight of the foam column is still substantially the same as though liquid levels were present even though the foam extends well above the liquid level. This may be high enough to bathe the wire terminals. However, if the liquid present between air particles is more viscous and cooler the level of the foam would be heavier yet and may not be high enough to extend above the level 44 of the container. Continued air flow and lack of flux could cause dry bubbling that could create an air cavity raising the foam above it higher and continuing to prevent replenishing liquid flux flow, resulting in irregular fluxing conditions. On the other hand, an air bubbler covered at all times with liquid flux tends to produce coarse bubbles with thick walls between bubbles that provide on the work pieces an excess of flux that is unnecessary and ultimately becomes objectionable dross.  
  However, with the present invention the flux is brought to and kept at a predetermined temperature so that its viscosity with respect to the disk is constant and any replenishing flux needed is preferably received through the disk along with the minute air bubbles. Such maintains foam continuity of the column and the central portion is easily forced above the level 44 a substantial distance as at 72 before the marginal portions spill over the edge at the level 44. Accordingly, additional air can be supplied and additional liquid flux would be supplied at the same time to prevent minute units of air from recollecting without enough liquid flux to hold a foam. Thereby the effect of substantial variations in the tube height above liquid flux replenishing level are overcome including pressure changes of the air and any special care required to maintain the upward bulge of the foam at 72 to flux contacts 36 passing therethrough. Only the temperature of the flux and the setting of the air valve is involved in the present invem tion to assure a continuing desired height of the foam bulge 72 above the level 44 to attain maximum results with minimum waste of flux.  
 Soldering Station At the soldering station 12, or stations, a long and narrow solder applicator trough 80 of a height greater than the level 44 is provided that is elongated&#39;in the direction of the arrow 82. The end walls 84 are cut down to the level 44 for the top edges thereof to form weirs 85 and 87. The upper portion of the side walls then form retaining walls 86 confining solder overflow to the weirs. The trough is received in an overflow tank 88 and a drain 90 therefrom leads to the inlet of a large capacity pump P driven by a speed controlled shaft 91 (FIG. 4). The outlet 92 of the pump extends through a thermostatically controlled electric heater 94 in heat exchange relationship therewith and terminates in an upwardly directing opening located approximately in the center of the trough 80 and well below the level 44. The pump is driven at a speed to supply hot solder in sufficient quantity to provide a spillage of solder over the weirs of a height as much as five-eighths inch. Thus the heated solder Welling up at the center 96 of the trough divides to flow in opposite directions over the weirs.  
  As the connector terminals 36 with the insulated wires thereon enter the solder over the weir 85 and move upstream of the current 98 fresh hot solder is brought into heat exchange with the terminals and rapidly heats them. By the time the center 96 is reached the wire insulation is vaporized off of the wire with nonvaporizing flux replacing the insulation in contact with the bare wire ends. As the connector terminals move from the center in the direction of the other of the two currents. as indicated at 100, the solder spreads in bonding contact with the fluxed bare metal of the wire and connectorsas timed to occur just before they pass over the other weir 87. At this time a blast of air 102A from a nozzle 104A is directed against the metal parts and the solder that is spilling over the weir 87. This blast cools the supporting parts of the connections and when the connections leave the solder, any surplus molten solder clinging thereto is driven back into the spillage for reheating and recycling. The solder remaining that economically coats the connection is frozen for solidification and immediate use or packaging of the work piece.  
  As shown in FIG. 4 the invention further contemplates rectilineal movement of the work pieces 130 along the edges 102 ofa U-shaped channel 101 serving as tracks to conduct them through station 110 for fluxing. and one or more stations 112 for soldering, as propelled therealong in the direction of the arrow 128 by push rods 116 secured to endless chains 105. The endless chains can return below or above the equipment illustrated. If below, one chain can be used and diverges from the channel where the rods 116 relinquished the work pieces.  
  The work pieces 130 shown that are carried by the tracks 102 are illustrated as stator and armature elements 104 and 105. respectively, of an electric motor assembled in a housing 106 which journals the armature at its upper driving end 107 and carries a dielectric mounting plate 135 at the lower commutator end, upon which brush holders 133 and connectors 136 are mounted as held in place by assembly screws 129.  
  As viewed in FIGS. 9 and 10 each connector 136 comprises a pair of connected sleeve rivets with one rivet portion 136A riveted to the insulation plate at its edge as at 137 and the other rivet portion 1368 having its tubular portion 136T extending downwardly below the plate 135. The extensions 136T receive coil leads 138 and wire connectors 139 that are terminally inserted and soldered therein. The flared upper end of the tubular portion 136T serves as a funnel 136F guiding the ends of the wires as they are inserted in place and the wires are either terminally bent or wrapped around the eyelet. The ends of the magnet coil wires 132, as shown in FIG. 9, have an insulation coating and the heavier lead wires shown in FIG. 10 are terminally stripped bare of insulation and crooked as at 139C to hold their inserted position until they are soldered in place. The rivets receive either one or both wires for a soldered electrical junction and along with the rivets, the brush holders 133 have downwardly bent eyeletted tabs 137 which extend below the level of the mounting board 135, it being noted that they connect with the brush holders at the level of the mounting board 135 as seen in FIGS. 6 and 7.  
  Referring to FIG. 6, two parallel broken lines 139 are shown to indicate paths on the mounting plate 135 which will accommodate the tracks 102 when the work piece 130 is placed thereon as shown in FIG. 4. Thus, as shown in FIGS. 5, 7 and 8, the armature. assembly screws 129, and brush holders 133 which extend below the mounting plate are received protectively between the side walls 103 of the channel member 101 while the depending connector elements 137 and 136T are disposed outside of the channel side walls 103 where they will pass through the flux foam and the currents 98 and of the that is flowing solder flowing above the level of the weirs 87.  
  In this embodiment, structure and operation are simplified by the channel 101 extending through the solder pots 12 with the walls 103 thereof providing the spaced retaining walls 186 extending through the center of the pots and the retaining side walls 86 serving as outside walls disposed at a height equal to that of the tracks 102.  
  Although the use of two soldering pots increases the number of piece parts processed by moving them faster, it has been found that with the sleeve rivets, the first soldering operation removes wire insulation, fluxes the bared metal and wets the sleeves and the bared wires with a coat of solder. With the second soldering operation, additional solder is deposited with the wetting solder to close the eyelet openings with an economical cross wall of solder which holds the wires solidly in place and provides a substantial electrical conductivity through solder between the wires substantially without reliance on the metal of the eyelet. Thereby juncture conductively is consistently high throughout the circuits with easily handled rivets having thin walls or tinned alloys whose circular shape contributes to strength in the assembly of the motor unit.  
  Referring to FIG. 8, it is to be noted that the depth of the channel 101 accommodates in a protective way a wide miscellany of lengths of depending non-soldered elements on work pieces. However, since the level of the solder is quite close to that of the tracks 102, it is desirable to avoid any flux or solder fumes and splatter contaminating important elements such as the commutator 105 and brush holder 133 where contact conductivity with brushes is important. A blower B is therefore utilized having a nozzle 140 which provides for an inflow of air at 120 in the channel under sufficient pressure to rise and flow outwardly to disperse any fumes or splatter harmlessly away from the non-soldered parts where the work pieces are passing through a critical zone such as that associated with the first solder pot following the fluxing of the work pieces.  
 Consideration By way of example involving work pieces shown, and not by way of limitation, the distance between weirs is approximately 3 inches; the depth of the spillage is approximately one-half inch which will accommodate terminal connectors of a wide range of heights; the total time of immersion of the connectors is approximately 0.07 minutes thereby providing some tolerance that safeguards conductor wires from being damaged; the air blast is heavy enough to blow excess solder off before it is cooled and enough air strikes the connectors exposed above the level of the molten solder to freeze the solder; the vapor dispersing air also cools depending parts (FIG. 5) which receive heat radiated from the walls of the conveyor channel 101; the temperature of the molten solder engaging the connectors is approximately 750 F; The insulation of the copper wire has the characteristics associated with an inner coating of polyurethane with an outer jacket of nylon both of which are essentially vaporized at 750F leaving only a byproduct that tends to clean or brighten the molten solder as distinguished from contaminating it.  
  As mentioned, the air comminuting disk 54 is preferably of stainless steel or bronze because these metals wash clean as the flux and air passes therethrough. Since the flux application is in an above room temperature environment that varies a great deal depending on air circulation designed to protect workers, it is preferred to heat the flux to a freely flowable condition at constant temperature rather than thin the flux with a liquid that vaporizes with heat. Vaporization not only would thicken but also chills the remainder with the latent heat of vaporization depletion.  
  The porosity of the disk 54 is approximately mi crons and although the air passing through it is comminuted to minute bubbles, the presence of flux in the body of the disk, and preferably moving with the air, has the advantage of initiating a fine foam at the exit surface of the disk. The thickness of the disk is between /a and 4 inch; the air inlet area therefor is inch and the applied air pressure is filtered and regulated to less than 1 psi. with a valve controlling the flow. The remaining upstream area of the disk is exposed to flux under a mild hydraulic pressure so that with such pressure and capillary action the flux flows to wet the downstream area of the disk. As the bubbles leave that area. they replace foam that has been depleted by the work pieces or by overflow. The adjustments of flux temperature and air pressure, once set, provide a constancy of performance that is free of normal variations in the hydraulic level of flux during flux depletion and replenishment.  
  Thus a temperature-time relation can be employed to burn away flux coated wire insulation and solder the bared wire without any contamination of an excellent, electrically conductive wire-terminal joint.  
  Although the viscosity of the flux can be controlled by dilution. reliance on this alone is not as satisfactory as controlling heat. However, heat and dilution can supplement one another to stabilize temperature in an environment where environmental heat-up, cool-off and drafts can cause appreciable changes with a hot soldering pot in close proximity.  
  Having described preferred embodiments of the invention it will be seen how various arrangements and modifications including devices that have a minimum of adjustable controls can be made without departing from the spirit and scope of the invention.  
 What is claimed is:  
  l. The method of mechanically soldering an electrical terminal connection carried by a workpiece com prising flowing a bed of heated molten solder over colevel spaced weirs and providing therebetween at a constant level in opposite directions from the center of an elongated laterally confined substantial area at a uniform level over colevel spaced weirs of restricted width at a predetermined depth,  
 progressively passing solder accepting terminals on a workpiece in a horizontal plane within said depth across one weir in an upstream direction into and through said center and downstream out of said molten solder across the other weir in said horizontal plane, and  
 directing a blast of air towards said other weir and the terminal connections as they progressively leave the molten solder across said other weir to scavenge back to the molten solder the excess molten solder thereon, and hardening the solder bond on the terminals while cooling the workpiece and the atmosphere above the molten solder around the workpiece.  
  2. The method of soldering a mechanical connection between connector terminals on a workpiece and insulated wire mechanically connected thereto including,  
 successively moving the connection through a flux bath and progressively and horizontally through a horizontally elongated bi-directionally flowing solder bath spaced from the workpiece, burning off the insulation in the solder bath and solder bonding the connection in said solder bath, and  
 scavenging excess solder from the solder bonded connection back to the molten solder and cooling the workpiece by a blast of air directed towards the bath and space between said bath and workpiece as the bonded connections progressively leave the solder bath.  
  3. The method recited in claim 2 including discharging the flowing solder over two weirs in opposite directions at approximately the same level, and  
 reheating said discharged solder and returning said reheated solder upwardly to the bath between the weirs in a column whose width is approximately less than a third of the distance between the weirs.  
  4. The method recited in claim 2 comprising moving the work pieces from the flux bath in a horizontal plane directly to the solder bath.  
  5. The method recited in claim 2 in which said flux for said bath is heated to predetermined temperature in a liquid state, and  
  9 comminuting said liquid and air in intimate relation in minute amounts to provide a foam extending into the path of said connection.  
  6. The method of claim 2 in which the molten solder flows in opposite directions over spillways in directions substantially aligned with the direction of movement of the connections between the spillways.  
  7. The method of claim 2 in which the molten solder intermediate the spillways is initially elevated approximately one-half inch above the weirs towards a workpiece passing above said solder intermediate the spillways.  
  8. The method of solder bonding mechanically associated parts including the step of passing laterally through two oppositely flowing spillways of molten solder and through flowing molten solder intermediate the spillways the lower end of a thin wall sleeve rivet connector terminal depending from a board spaced above said molten flowing solder providing an air gap with wires extending therethrough at least one of which is insulated and removing the insulation below the rivet to bare the wires,  
 directing an upwardly flowing current of heated molten solder into contact with said depending terminal. and,  
 solder bonding and setting the connections to close the lower opening of the terminal with solder to provide substantial electrical conductivity between the wires through the solder.  
  9. The method of solder bonding insulated connector wire ends disposed in a depending thin wall sleeve rivet connector terminal having a sharp edge depending from a support including the steps of passing the terminal and wire ends laterally through a body of molten solder flowing in one direction with the support spaced from the solder, vaporizing the insulation and tinning the wire ends and connector without overspread of the solder,  
 passing the tinned wire ends and terminal through a 10 body of molten solder spaced from the support and flowing in another direction to fill the lower end of the sleeve terminal with solder as an electrical conductor between the wires, and  
 blasting the soldered parts laterally thereto with air as they leave the body of molten solder to scavenge excess solder from the soldered parts and drive it back into the body without splatter for reheating and recirculation.  
  10. The method of solder bonding mechanically associated connections having insulated wire and extending from a dielectric body including the steps of heating and raising molten solder from a-reservoir centrally between and to a level above two spaced weirs,  
 confining the molten solder to flow horizontally elongated distances in opposite directions to the weirs over which the molten solder spills back to the reservoir,  
 successively moving the connections colevel with that of the molten solder andin depending relation through a flux bath and unindirectionally over one weir through the flowing solder with an air gap between the body and molten solder,  
 burning off the insulation, vaporizing the flux and removing dross and debris back to the reservoir with solder flowing in one direction, solder bonding and setting the connections with the molten solder flowing in the other direction,  
 cooling said body and scavenging excess solder from the bonded connections as the connections exit from the solder over the other weir coincident with a timed blast of air directed at the space between the body and molten solder.  
  11. The method of claim 10 in which the total width of both spillways is less than a third of the circumference of the exposed area of said horizontal flow of the molten solder.