EP0000284B1 - Verfahren und Einrichtung zum Wiederaufschmelzen des Lötmittels von lötbeschichteten Substraten und auf diese Weise hergestellte Substrate - Google Patents

Verfahren und Einrichtung zum Wiederaufschmelzen des Lötmittels von lötbeschichteten Substraten und auf diese Weise hergestellte Substrate Download PDF

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Publication number
EP0000284B1
EP0000284B1 EP78300100A EP78300100A EP0000284B1 EP 0000284 B1 EP0000284 B1 EP 0000284B1 EP 78300100 A EP78300100 A EP 78300100A EP 78300100 A EP78300100 A EP 78300100A EP 0000284 B1 EP0000284 B1 EP 0000284B1
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EP
European Patent Office
Prior art keywords
chamber
solder
web
substrate
vapour
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP78300100A
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English (en)
French (fr)
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EP0000284A1 (de
Inventor
Hans Hugo Ammann
Michael Ackman Oien
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AT&T Corp
Original Assignee
Western Electric Co Inc
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Filing date
Publication date
Application filed by Western Electric Co Inc filed Critical Western Electric Co Inc
Publication of EP0000284A1 publication Critical patent/EP0000284A1/de
Application granted granted Critical
Publication of EP0000284B1 publication Critical patent/EP0000284B1/de
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
    • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
    • H05K3/3494—Heating methods for reflowing of solder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K1/00—Soldering, e.g. brazing, or unsoldering
    • B23K1/012—Soldering with the use of hot gas
    • B23K1/015—Vapour-condensation soldering
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/03—Use of materials for the substrate
    • H05K1/0393—Flexible materials
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/04—Soldering or other types of metallurgic bonding
    • H05K2203/043—Reflowing of solder coated conductors, not during connection of components, e.g. reflowing solder paste
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/07—Treatments involving liquids, e.g. plating, rinsing
    • H05K2203/0756—Uses of liquids, e.g. rinsing, coating, dissolving
    • H05K2203/0776—Uses of liquids not otherwise provided for in H05K2203/0759 - H05K2203/0773
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/15—Position of the PCB during processing
    • H05K2203/1545—Continuous processing, i.e. involving rolls moving a band-like or solid carrier along a continuous production path
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
    • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
    • H05K3/3457—Solder materials or compositions; Methods of application thereof
    • H05K3/3473—Plating of solder

Definitions

  • This invention relates to a process and apparatus for reflowing solder of solder plated substrates and to substrates formed thereby and relates especially to a process and apparatus for reflowing solder plated flexible circuit substrates with negligible loss of heat transfer fluid.
  • U.S. patent 3,904,102 attempts to reduce loss of the expensive fluid by use of a less expensive vapor blanket atop the primary vapor zone.
  • One embodiment of this method utilizes batch processing techniques. A group of printed circuits is lowered into a receptacle containing the primary vapor zone and the secondary vapor blanket. In another embodiment a conveyor carries the individual circuits into the vapor zone.
  • significant quantities of the expensive primary fluid are still lost.
  • the second embodiment continues to suffer from solder pooling effects.
  • the first embodiment obviously is not readily adaptable for handling continuous webs of printed circuits.
  • a process for reflowing solder on a solder plated substrate in which the substrate is moved through a chamber containing a vapor the temperature of which is sufficient to melt and reflow the solder plating of said substrate, and characterised in that the substrate is moved through an interface between the said vapor and a liquid, the interface providing a seal to the chamber.
  • apparatus for carrying out a process of reflowing solder on a solder plated substrate, the apparatus comprising a chamber for containing a vapor the temperature of which is sufficient to melt and reflow the solder plating of a solder plated substrate and means for moving a solder plated substrate through said chamber, and characterised by a container for containing a liquid the temperature of which is less than the melting point temperature of the solder plating, the chamber and the container being arranged so that in use an interface between said vapor and said liquid provides a seal to said chamber through which the substrate is arranged to be moved.
  • liquid/vapor interface in accordance with the present invention can significantly reduce, if not virtually eliminate, loss of the expensive working fluid resulting from web dragout, diffusion and convection.
  • the invention is realized in an illustrative embodiment of a process and machine for processing a reflowable solder-plated flexible circuit web wherein the flexible circuit web is introduced into a first chamber having a vapor diffusion trap at an entry port and a liquid seal at an exit port.
  • the temperature of the flexible circuit web is controlled in the first chamber to a point below the solder eutectic temperature.
  • provision is included in the first chamber for positioning the flexible circuit web in a planar orientation for entry into a second chamber, containing a condensing vapor, at a point below the vapor-air interface. This condensing vapor is confined in the second chamber by the liquid seal.
  • the flexib!e circuit web Upon entry into the second chamber the flexib!e circuit web is exposed to the condensing vapor for a time sufficient to melt and reflow the solder while maintaining on the flexible circuit web a condensate film to aid in subsequently evaporatively cooling the flexible circuit web below the solder eutectic temperature. Residual traces of condensate on the flexible circuit web are recaptured and thereafter the flexible circuit web is removed through an exit port.
  • Such an embodiment of the present invention is advantageous in that the flexible circuit web undergoes a preheating operation during passage through the liquid seal; the liquid seal confines vapors of the expensive working fluid internal to the machine and keeps the solder below the eutectic temperature prior to entry into the condensing vapors; the flexible circuit web is positioned at low web tension in a planar orientation during passage through the vapor zone thereby virtually eliminating solder pooling on the web; oxidising environments are avoided during solder reflow operations; flux applicati.on and its subsequent removal are avoided; a sufficient vapor condensate film is retained on the flexible circuit web after exiting from the vapor zone to materially aid in evaporatively cooling the reflowed solder below its eutectic temperature before mechanically contacting surfaces which might redistribute the reflowed solder; the liquid seal at the entry side of the vapor chamber and a plurality of reheat rollers and diffusion traps at the exit side of the vapor chamber prevent significant loss of the .expensive working fluid through web
  • a flexible circuit web 100 is comprised of a dielectric substrate 101 onto which is bonded a patterned conductive foil 102.
  • the patterned conductive foil 102 is utilized to effect electrical circuit connections among a plurality of electric circuit components (not shown).
  • Conductive foil 102 can be advantageously bonded on one or both sides of flexible circuit web 100.
  • the patterns of conductive foil 102 are generally interconnected, for example, by one or more plated-through holes 103.
  • solder coating 104 is placed atop conductive foil 102 for several reasons.
  • solder coating 104 is used as an etch resist. In the etch resist application of solder coating 104, oftentimes understanding occurs near the edges of conductive foil 102. This leaves a solder lip projecting outwardly from conductive foil 102. Such lips are susceptible to fracture and the formation of slivers during handling or subsequent processing. These slivers of solder can cause shorts between electrical circuits, thereby causing circuit failure.
  • solder coating 104 inhibits oxidation and corrosion of conductive foil 102 to reduce the possibility of circuit failure through these mechanisms.
  • solder coating 104 enhances solder wetting of the circuit during subsequent solder assembly operations.
  • solder by virtue of the surface tension characteristics of solder, causes these solder lips, when molten, to draw up onto conductive foil 102.
  • a further advantage of reflow soldering is that on double-sided circuits, solder sometimes bridges gaps in conductive foil 102. These solder bridges may disguise defects in the circuit which might lead to subsequent failure. Solder reflow eliminates these bridges and exposes possible circuit defects.
  • Solder reflow also provides a means for perceiving solder wetability, and consequently provides a measure of acceptability for further processing.
  • An additional advantage of solder reflow is that it aids in improving the cosmetic appearance of the circuit, thereby enhancing customer acceptability.
  • FIG. 2A Illustrated in FIG. 2A is a simplified embodiment of a solder reflow machine 110.
  • the solder reflow machine 110 is comprised of an enclosure 120 having a top 121, a bottom 122, and a pair of sidewalls 123 and 124. The remaining two sidewalls are not shown in order to facilitate this description.
  • a baffle 125 extends upwardly from an intermediate point of bottom 122 to a point spaced apart from top 121.
  • Another baffle 126 extends downwardly from an intermediate point of top 121 to a point spaced apart from bottom 122. Baffles 125 and 126 separate enclosure 120 into four definable compartments.
  • first and second sumps, 127 and 128, and first and second chambers, 130 and 131 These compartments are hereinafter referred to, in the course of this conceptual description, as first and second sumps, 127 and 128, and first and second chambers, 130 and 131.
  • Chamber 130 spans sump 127 and a portion of sump 128.
  • Chamber 131 spans the remainder of sump 128..
  • Each of chambers 130 and 131 has a port 132 and 133, respectively, associated therewith near top 121. Set apart from bottom. 122 in sump 128 is positioning roller 129.
  • a single noncorrosive working fluid 140 having a boiling point at atmospheric pressure sufficiently in excess of the liquidus temperature of the solder to be reflowed is contained in sumps 127 and 128 which, as noted previously, are separated from one another by baffle 125.
  • Baffle 125 is of sufficient height to keep the working fluid 140 contained in sumps 127 and 128 generally separated. However, baffle 125 is not so high that a portion of working fluid 140 in sump 128 cannot spill over into sump 127.
  • Heating elements 141 located in sump 127 boil working fluid 140 to produce a vapor more dense than air. The resulting vapor forms a vapor zone 142 which partially fills chamber 130.
  • the height of vapor zone 142 is controlled in chamber 130 by a plurality of condenser elements 143 and 144 along sidewall 123 and baffle 126, respectively.
  • flexible circuit web 100 passes over feed roller 150, enters port 133 in chamber 131, passes into working fluid 140, and is routed about roller 129.
  • the temperature of working fluid 140 in sump 128 is maintained below the solder eutectic temperature of solder coating 104 on web 100 by temperature control element 138. However, the temperature is high enought to perform some preheating of web 100.
  • web 100 with solder coating 104 thereon passes into vapor zone 142.
  • the heated vapors in vapor zone 142 condense onto the relatively cool web, thereby effectively heating web 100 to a temperature above the solder liquidus temperature, melting solder coating 104 and causing it to reflow.
  • web 100 is moved in a planar orientation at a selectable angle with respect to a horizontal plane. This orientation ensures that solder coating 104, after reflow, is maintained at a generally uniform thickness while in its molten state.
  • flexible circuit web 100 passes through cooling element 139, diffusion trap 134, and out through port 132 in first chamber 130 where it passes over a cooled discharge roller 151 to a take-up reel (not shown).
  • the cooling of discharge roller 151 is accomplished in a well-known manner and, hence, the details of such cooling are not specifically illustrated.
  • some form of cooling is desirable prior to web 100 being brought into contact with discharge roller 151.
  • sufficient quantities of vapor condensate are retained on web 100 such that during the remainder of the time web 100 is contained within chamber 130 the condensate film evaporatively cools the reflowed solder below its eutectic temperature.
  • Diffusion traps 134 and 135 are shown as simplified structures in FIGS. 2A and 3 so as not to overcomplicate the description at this point. A more specific structure of diffusion traps 134 and 135 will be described in reference to FIG. 5A.
  • flexible circuit web 100 is fed over roller 150 through port 132 in sidewall 123 and through diffusion trap 134 into chamber 130. Upon entry of web 100 into chamber 130, it is exposed to vapor zone 142. The hot vapors melt solder coating 104 on web 100, causing the solder to reflow. Following passage through vapor zone 142, web 100 passes through liquid seal 137 at exit port 136 separating chamber 130 from sump 128. Once in sump 128, web 100 is further cooled by passage through cooling elements 145.
  • positioning roller 129 in sump 128 is used in conjunction with roller 150 to control the orientation of web 100 during this phase of the process. It should be noted that in the embodiment illustrated in FIG. 2A similar positioning effects are achieved with comparable roller 151.
  • one significant feature is that during passage of web 100 through vapor zone 142, web 100 is maintained in a planar orientation. This orientation insures a relatively uniform thickness of the layer of solder coating 104 on web 100 following the reflow process.
  • Another feature is that the use of liquid seal 137 between sumps 127 and 128 significantly aids in preventing the loss of vapors of working fluid 140. Diffusion traps 134 and 135 at entry and exit ports 132 and 133 further aid in reducing the amount of loss of working fluid 140.
  • FIG. 4 The preferred embodiment for machine 110 used in implementing the solder reflow process is shown in FIG. 4 in outline form. Specifically illustrated is apparatus on machine 110 for aiding. in the threading of flexible circuit web 100 through the various chambers in the machine. Also specifically shown is apparatus which facilitates elevation of one end of machine 110 with respect to an opposite end thereof which apparatus controls the angle between a plane containing web 100- and a horizontal plane.
  • rollers 123 To aid in threading flexible circuit web 100 through the various chambers in machine 110, there are affixed to sidewall 123 a pair of pulleys 154 and 155. Idler pulleys 156 and 157 at the end of roller 150 and pulleys 160 and 161 at the end of roller 151, are affixed to top 121. Additional idler pulleys 158 and 159 are affixed to sidewall 124. Similar idler pulleys (not shown) are affixed to the ends of rollers 129, 167, 168, and 169 internal to machine 110.
  • Looped around pulleys 154, 156, 158, and 160 is a continuous, flexible transport member 162, and looped around pulleys 155, 157, 159, and 161 is a similar transport member 163.
  • Transport members 162 and 163 may be advantageously, for example, continuous cables, chains or the like.
  • a shaft 149 which has affixed thereon, at an intermediate point along its length, a drive pulley 147.
  • Motor 146 mounted on sidewall 123, is coupled to drive pulley 147 by drive belt 148.
  • shaft 149 rotates, and this rotation forces transport members 162 and 163 to threadably traverse the various chambers in machine 110.
  • Bar 165 when fastened to transport members 162 and 163, enables flexible circuit web 100 to be looped therearound and fastened onto itself.
  • web 100 is carried via transport members 162 and 163 and bar 165 through machine 110.
  • motor 146 is stopped and bar 165 can be removed from transport members 162 and 163.
  • flexible circuit web 100 can be brought into engagement with a take-up reel (not shown).
  • the solder reflow process becomes continuous merely by fastening one flexible circuit web 100 to another by means such as stapling the two webs together.
  • machine 110 has a bottom edge 192 affixed to frame 170 by pivot 171.
  • Elevation strut 172 pivotally mounted to opposite bottom edge 191 of machine 110, permits raising edge 191 relative to edge 192. Adjustment of the slope between an angle of 10 to 30 degrees is readily implemented by changing the attachment position of strut 172 . to frame 170 atong plurality of apertures 173. Once the appropriate elevation is selected, strut 172 is held juxtaposed the appropriate aperture 173 by a holding pin (not shown).
  • FIG. 5A The preferred embodiment of machine 110 is shown in cross sectional view in FIG. 5A.
  • Flexible circuit web 100 enters machine 110 by downwardly deflecting wiper assembly 177 at entry port 133.
  • Wiper assembly 177 similar to that shown in FIG. 7, along with baffles 180 and 181 and the close spacing along diffusion trap 135, virtually prevent escape of any working fluid 140 from machine 110 at the point of entry of flexible circuit web 100.
  • web 100 is immersed into fluid 140 in sump 128 and is passed around roller 129.
  • Roller 129 positions web 100 for entry into chamber 130 so that web 100 will encounter vapor zone 142 in a planar orientation below the vapor air interface.
  • temperature control element 138 controls the temperature of fluid 140 so that it preheats solder coating 104 on web 100 to just below the solder eutectic temperature. In the event the temperature of fluid 140 is sufficiently high so as to generate any vapors, these vapors, upon exposure to diffusiuon trap 135, are condensed into liquid form. Consequently, troughs 195 are provided at lower ends of diffusion trap 135 so that any recondensed vapors are returned to sump 128. rather than forming on web 100.
  • passageway 136 separating sump 128 from vapor zone 142.
  • Passageway 136 is formed by baffle 126 which extends from top 121 downwardly to a point spaced apart from bottom 122. To preclude escape of vapors from chamber 130; the fluid in sump 128 is maintained at a level just above passageway 136. Hence, web 100 enters chamber 130 through liquid seal 137.
  • Vapor zone 142 in chamber 130 is generated by boiling fluid 140 in sump 127 by heating elements 141.
  • the temperature of heating elements 141 is controlled in order to maintain fluid 140 in contact with them at a nearly uniform temperature. This is effected by making heating elements 141 such that they have a uniform resistance per unit of length. This uniform resistance ensures that a proportionate reduction in power will produce a proportionate reduction in heat flux. The reduction in heat flux results in fewer hot spots being formed in fluid 140 and this, in turn, improves the usable lifetime of fluid 140.
  • Control of the height of the vapor air interface is effected by condenser elements 143 and 144 positioned along enclosing surfaces of chamber 130 containing vapor zone 142.
  • the location of condenser elements 143 and 144, which elements are adjustable as shown most clearly in FIGS. 6B and 6C, along with the elevation angle of bottom edge 191 (Fig. 4) of machine 110 and the speed of travel of web 100 fixes the time of exposure of solder coating 104 on web 100 to vapor zone 142.
  • Baffles 182 and 183 are positioned just below the vapor air interface to decrease the amount of convection air interacting with soldering coating 104 during its passage through vapor zone 142. This results in a more uniform exposure of web 100 to the hot vapors of vapor zone 142 and this in turn results in an improved cosmetic appearance of flexible circuit web 100 because the presence of air in the vicinity of the reflowed solder tends to oxidize the solder thereby dulling the finish.
  • a demister unit 197 is provided in sump 127.
  • this condensate material ly aids in the cooling of web 100 as it passes between upper condenser element 184 and lower condenser element 185. Cooling at this point is desirable in order to bring the temperature of solder coating 104 below its eutectic temperature prior to its being brought into contact with roller 167.
  • Upper condenser element 184 has a doghouse-like shape so that any condensate driven off web 100 onto this condenser is prevented from dripping back onto web 100.
  • upper condenser element 184 includes oppositely directed members 201 and 202, as shown in FIG. 5B, which members are oriented at a common angle with respect to a plane containing flexible circuit web 100.
  • baffle 203 separates chamber 130 from the follow-on stages used to recapture any residual traces of fluid 140 which may have a tendency to escape through web dragout.
  • web 100 engages a plurality of reheat rollers 167 through 169 and a corresponding plurality of diffusion traps 186, 190, and 134, respectively.
  • Roller 167 and diffusion trap 186 are separated from roller 168 and diffusion trap 190 by baffles 187 and 188.
  • roller 168 and diffusion trap 190 are separated from roller 169 and diffusion trap 134 by baffles 188 and 189.
  • each of diffusion traps 186, 190 and 134 are provided with troughs 195 at their lower extremities. Troughs 195 reduce the possibility of recaptured condensate coming into contact with web 100.
  • exit port 132 Following passage of web 100 around reheat roller 169 and through diffusion trap 134, it emerges through exit port 132.
  • diffusion trap 134 is coupled to exit port 132 by baffles 205 and 206 which are spaced closely together.
  • exit port 132 is equipped with a wiper assembly 178, as shown in FIG. 7, which further provides for removal of any traces of vapor of fluid 140 carried by web 100.
  • condenser elements 143 and 144 are adjustable so that along with the speed of travel of web 100 and the angle of elevation of bottom edge 191 with respect to bottom edge 192 of machine 110, the exposure time of solder coating 104 to vapor zone 142 can be accurately controlled. The manner of adjustment of condenser elements 143 and 144 will be considered subsequently.
  • FIG. 6A Illustrated in FIG. 6A is apparatus for transporting flexible circuit web 100 through machine 110 such that web 100 is maintained in a planar orientation at low web tension during its passage through vapor zone 142.
  • motor 220 mounted on top 121, shown only in FIG. 6A for clarity, drives discharge roller 151 and intermediate rollers 167 through 169 by drive chains 221.
  • variably adjustable tension roller 251 is used to control the tension in web 100 as it is fed from supply roller 250.
  • Tension roller 251 is coupled to pneumatic constant load device 253 by tension control arm 252. Coupled to tension control arm 252 is tension arm position sensor 254.
  • tension arm position sensor 254 detects this change in position of tension control arm 252 and as a result an electrical signal is produced which causes drive motor 220 to slow down.
  • the decrease in rotational speed of drive motor 220 arrests the imbalance between the feed rate and machine output speed, thereby effectively controlling the amount of web looped around tension roller 251 so that the tension in web 100 is held nearly constant during its passage through machine 110.
  • bottom edge 191 of machine 110 is adjustable with respect to bottom edge 192.
  • This elevation adjustability aids in providing a more uniform thickness to solder coating 104 following the solder reflow process without the detrimental effects caused by solder slump. inherent in catenary feed arrangements.
  • This elevation adjustability further aids in controlling the amount of vapor condensate remaining on web 100 as it rises above the vapor air interface for evaporative cooling.
  • Control of the height of vapor zone 142 is achieved by the adjustability of condenser elements 143 and 144.
  • Each of condenser elements 143 and 144 includes movable pans 230 and 230' for housing the condenser elements themselves.
  • Pans 230 and 230' can be moved advantageously in either a generally vertical or generally horizontal direction, as appropriate. To effect this movement pans 230 and 230' are coupled via shafts 231 and 231' to hand cranks 232 and 232', respectively.
  • condenser elements 143 and 144 provide direct cooling, it is desirable that any condensate forming thereon be returned directly to sump 127 without coming into contact with flexible circuit web 100.
  • pans 230 and 230' are provided with telescoping tubes 235 and 235' which couple pans 230 and 230' directly to sump 127 regardless of the position of condenser elements 143 and 144 with respect to sump 127. This arrangement has the further effect of minimizing the production of excessively hot vapors needed to maintain vapor zone 142 and this, in turn, increases the useful lifetime of working fluid 140.
  • FIG-. 7 Additional measures used to prevent the loss of fluid 140 are represented by the wiper arrangement shown in FIG-. 7 and briefly discussed earlier. Specifically illustrated in cross sectional form is the wiper arrangement at exit port 132. Flexible membranes 260 and 261 are affixed in overlapping alignment along edges 262 and 263, respectively, of exit port 132 by rigid members 264 and 265. As web 100 emerges fom exit port 132, membranes 260 and 261 are flexed outwardly forming a seal about web 100. This seal prevents any convective loss of vapor due to web 100 dragging out the mixture of air and vapor existing near diffusion trap 134.
  • heating elements 141 are used to control the boiling rate of fluid 140 and to avoid the production of hot spots thereby increasing the lifetime of fluid 140. Besides making heating elements 141 such that they have a uniform resistance per unit of length, the power to them is controlled so that a proportionate reduction in power produces a proportionate reduction in heat flux. This result is achieved by the silicon controlled rectifier circuit illustrated in FIG. 8.
  • Three phase, 60 cycle AC commercial power on lines L1, L2 and L3 is coupled through fuses 290 to filter capacitors 291. Following each capacitor 291 there is a parallel circuit comprised of diode 292 and a silicon controlled rectifier 293. Diode 292 provides rectification of the AC power and silicon controlled rectifier 293, by virtue of a trigger bias voltage coupled thereto, fairly accurately controls the amount of rectified power supplied to heating elements 141. This arrangement insures that all heating elements 141 are activated uniformly which, in turn, virtually eliminates hot spots in fluid 140 thereby increasing its useful lifetime.

Claims (10)

1. Verfahren zum Rückfließenlassen von Lot (104) auf einem lotplattierten Substrat (100), bei dem das Substrat (100) durch eine Kammer (130) hindurchbewegt wird, die einen Dampf (142) bei einer Temperatur enthält, welche für ein Schmelzen und Rückfließenlassen der Lotplattierung (104) des Substrates ausreichend ist, dadurch gekennzeichnet, daß das Substrat (100) durch eine Grenzfläche (137) zwischen dem Dampf (142) und einer Flüssigkeit hindurchbewegt wird, wobei die Grenzfläche eine Abdichtung für die Kammer (130) bildet..
2. Verfahren wie in Anspruch 1 beansprucht, bei dem das Substrat (100) in einer im wesentlichen geraden Linie durch den in der Kammer (130) enthaltenen Dampf (142) hindurchbewegt wird.
3. Verfahren wie in Anspruch 1 oder Anspruch 1 beansprucht, bei dem das Substrat (100) durch die Kammer (130) und durch eine weitere Kammer (131) hindurchbewegt wird, wobei die weitere Kammer (131) eine Flüssigkeit (140) enthält, deren Temperatur niedriger als die Temperatur des Schmelzpunktes der Lotplattierung (104) ist, und die Flüssigkeit/Dampf-Grenzfläche (137) zwischen der Kammer (130) und der weiteren Kammer (131) vorgesehen ist.
4. Verfahren wie nach Anspruch 3 beansprucht, bei dem ein flexibles Substrat (100) durch die weitere Kammer (131) hindurchbewegt wird, bevor es durch die Kammer (130) hindurchbewegt wird.
5. Lotplattiertes Substrat, dessen Lotplattierung (104) dazu gebracht worden ist entsprechend einem Verfahren, wie dieses in einem der Ansprüche 1 bis 4 beansprucht ist, rückzufließen.
6. Apparatur zum Durchführen eines Verfahrens zum Rückfließenlassen von Lot (104) auf einem lotplattierten Substrat (100), wobei die Apparatur eine Kammer (130) zur Aufnahme eines Dampfes (142), dessen Temperatur für ein Schmelzen und Rückfließenlassen der Lotplattierung (104) ausreichend ist, und eine Einrichtung (129, 150, 151) zum Bewegen eines lotplattierten Substrates (100) durch die Kammer (130) aufweist gekennzeichnet durch einen Behälter (131) zur Aufnahme einer Flüssigkeit (140), deren Temperatur niedriger als die Temperatur des Schmelzpunktes der Lotplattierung (104) ist, wobei die Kammer (130) und der Behälter (131) so ängeordnet sind, daß beim Gebrauch eine Grenzfläche (137) zwischen dem Dampf (142) und der Flüssigkeit (140) eine Abdichtung für die Kammer (130) bildet, durch welche das Substrat (100) hindurch zu bewegen ist.
7. Apparatur wie nach Anspruch 6 beansprucht, bei der die Einrichtung (129, 150, 151) zum Bewegen des lotplattierten Substrates (100) durch die Kammer (130) hindurch für eine Bewegung des Substrates (100) in einer im wesentlichen geraden Linie ausgelegt ist.
8. Apparatur wie in Anspruch 6 oder Anspruch 7 beansprucht, bei der der Behälter (131) die Form einer weiteren Kammer (131) annimmt, in der eine Walzeneinrichtung (129) vorgesehen ist, um die das flexible Substrat (100) herumgeführt wird, wobei die Walzeneinrichtung (129) unterhalb des beabsichtigten Flüssigkeitsoberflächenniveau angeordnet ist, wodurch das Substrat (100) dazu gebracht wird, einen Weg zu durchqueren, der durch die Flüssigkeit (140) der weiteren Kammer (131), durch die Flüssigkeit/Dampf-Grenzfläche (137) zwischen den beiden Kammem (130, 131) und in einer im wesentlichen geraden Linie durch den Dampf (142) der den Dampf enthaltenden Kammer (130) verläuft.
9. Apparatur wie in Anspruch 8 beansprucht, bei der die den Dampf enthaltende Kammer (130) eine Heizeinrichtung (141) zum Heizen einer eingebrachten Flüssigkeit (140), um den Dampf (142) zu erzeugen, und eine Kondensationseinrichtung (143, 144) zum Bestimmen des Dampfpegels in der Kammer (130) aufweist.
10. Apparatur wie in Anspruch 8 oder Anspruch 9 beansprucht, bei der die Dampf enthaltende Kammer (130) und die weitere Kammer (131) mit einer Substrat-Einlaß/Auslaßeinrichtung (132, 133) und mit einer Einrichtung (134, 135, 139, 177, 178) versehen ist, die der Einlaß/Auslaßeinrichtung (132, 133) zugeordnet ist, um einen Verlust an Flüssigkeit/Dampf (140, 142) durch die Einlaß/Auslaßeinrichtung hindurch zu verhindern.
EP78300100A 1977-07-01 1978-06-29 Verfahren und Einrichtung zum Wiederaufschmelzen des Lötmittels von lötbeschichteten Substraten und auf diese Weise hergestellte Substrate Expired EP0000284B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US05/812,230 US4115601A (en) 1977-07-01 1977-07-01 Flexible circuit reflow soldering process and machine
US812230 1985-12-23

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EP0000284A1 EP0000284A1 (de) 1979-01-10
EP0000284B1 true EP0000284B1 (de) 1980-10-29

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US (1) US4115601A (de)
EP (1) EP0000284B1 (de)
JP (1) JPS5826194B2 (de)
CA (1) CA1081550A (de)
DE (1) DE2860255D1 (de)
ES (1) ES471324A1 (de)
IE (1) IE46960B1 (de)
IT (1) IT1096957B (de)

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Also Published As

Publication number Publication date
JPS5418070A (en) 1979-02-09
IT7825259A0 (it) 1978-06-30
JPS5826194B2 (ja) 1983-06-01
US4115601A (en) 1978-09-19
DE2860255D1 (en) 1981-01-29
ES471324A1 (es) 1979-02-01
EP0000284A1 (de) 1979-01-10
IT1096957B (it) 1985-08-26
IE781327L (en) 1979-01-01
IE46960B1 (en) 1983-11-16
CA1081550A (en) 1980-07-15

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