EP0000284B1 - Process and apparatus for reflowing solder of solder plated substrates and substrates formed thereby - Google Patents
Process and apparatus for reflowing solder of solder plated substrates and substrates formed thereby Download PDFInfo
- 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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- European Patent Office
- Prior art keywords
- chamber
- solder
- web
- substrate
- vapour
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- 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.)
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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.
Description
- 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.
- Several methods have been disclosed in the prior art for effecting solder reflow operations on printed circuits through the use of hot saturated vapors. One such method is briefly described in an article entitled "Solvent Vapor Solder Reflow" by E.G. Dingman, appearing in the IBM Technical Disclosure Bulletin, Vol. 13, No. 3, August 1970, at page 639. Dingman discloses use of boiling solvents to rapidly and selectively apply heat to small areas having high thermal conductivity to enable solder rework operations with materials and components that are heat sensitive. It seems readily apparent that Dingman does not address the problems of handling large and continuous flexible circuit webs or loss of the boiling solvent.
- One method for continuously handling printed circuits is disclosed in U.S. patent 3,866,307. In this method individual circuit boards are loaded onto a conveyor and passed through a receptacle containing hot saturated vapors of an expensive fluid and a wave soldering font. Individual circuit boards are heated by the vapors and skim the solder wave at a low point of the conveyor catenary. One problem resulting from the approach is that solder tends to pool at the low point of the catenary. Another problem is that despite attempts to retain the expensive fluid, substantial quantities are dragged out of the receptacle along with the conveyor and the circuit boards themselves.
- Another method disclosed in 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. However, in both embodiments significant quantities of the expensive primary fluid are still lost. Moreover, 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 somewhat related application of the use of hot vapors is disclosed in U.S. patent 3,737,499. The method is used for modifying plastics surfaces on articles of manufacture. An individual plastics article is inserted into a multi- compartmented chamber containing one or more vapor regions. The heated vapors impinge on the surfaces of the plastics articles and dissolve at least a molecular layer to remove any surface blemishes and produce a smooth, continuous finish. Like other procedures mentioned above, this also suffers loss of the vapor material through web dragout.
- Problems of the following kind are ameliorated by the invention.
- According to one aspect of the present invention there is provided 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.
- According to another aspect of the present invention there is provided 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.
- The use of a 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. Moreover, 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. 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 dragout; the plurality of reheat rollers and diffusion traps facilitate recapture and reuse of any residual traces of condensate on the continuous, flexible circuit web; and the machine can be advantageously elevated on its output side between an angle of 10 to 30 degrees to achieve a range of planar orientations of the web with respect to horizontal, to facilitate return of the recaptured working fluid to its reservoir, and to control the amount of solder slump. Specifically, the machine parameters, including slope, may be adjusted advantageously to process a wide variety of flexible circuits over a wide range of throughput speeds.
- The aforementioned aspects of the invention as well as others will be better understood upon consideration of the following detailed description and appended claims, taken in conjunction with the attached drawings of various illustrative embodiments in which:
- FIG. 1 illustrates a flexible circuit web having a number of electrically conductive patterns thereon and plated-through holes therethrough;
- FIG. 2A is a simplified embodiment illustrating the solder reflow process;
- FIG. 2B defines the shading codes used in FIG. 2A and all similarly shaded FIGS.;
- FIG. 3 is an alternate simplified embodiment illustrating the solder reflow process;
- FIG. 4 is a simplified perspective view of a solder reflow machine used in practicing the process, in particular, illustrating the slope adjustability feature and the threading aid feature;
- FIG. 5A is a sectional view along
line 5A-5A of FIG. 4 illustrating the various chambers and rollers utilized' in the solder reflow machine to practice the process; - FIG. 5B is a sectional view along line 58-58 of FIG. 5A illustrating the doghouse-like cooling arrangement;
- FIG. 6A- illustrates the main condenser adjustability, slope adjustment, and web tension control and drive system features;
- FIGS. 6B and 6C are partial cutaway views further showing condenser adjustability;
- FIG. 7 is a partial cutaway view illustrating wiper arrangements used at both the entry and exit ports of the machine to further aid in recapture of the working fluid; and
- FIG. 8 is a silicon-controlled rectifier circuit for maintaining uniform heating temperatures and for minimizing the temperature of the heating elements to thereby increase the lifetime of the working fluid.
- A
flexible circuit web 100, as shown in FIG. 1, is comprised of adielectric substrate 101 onto which is bonded a patternedconductive foil 102. The patternedconductive 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 offlexible circuit web 100. On double-sided circuits, the patterns ofconductive foil 102 are generally interconnected, for example, by one or more plated-throughholes 103. - In manufacturing flexible printed circuits, a
solder coating 104 is placed atopconductive foil 102 for several reasons. First, in numerous applications,solder coating 104 is used as an etch resist. In the etch resist application ofsolder coating 104, oftentimes understanding occurs near the edges ofconductive foil 102. This leaves a solder lip projecting outwardly fromconductive 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. Second,solder coating 104 inhibits oxidation and corrosion ofconductive foil 102 to reduce the possibility of circuit failure through these mechanisms. Third,solder coating 104 enhances solder wetting of the circuit during subsequent solder assembly operations. - Implementation of reflow soldering, 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 inconductive 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.
- Illustrated in FIG. 2A is a simplified embodiment of a
solder reflow machine 110. This simplified version facilitates an understanding of the details of the solder reflow process. Thesolder reflow machine 110 is comprised of anenclosure 120 having a top 121, a bottom 122, and a pair ofsidewalls baffle 125 extends upwardly from an intermediate point of bottom 122 to a point spaced apart fromtop 121. Anotherbaffle 126 extends downwardly from an intermediate point of top 121 to a point spaced apart frombottom 122.Baffles separate enclosure 120 into four definable compartments. 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 spanssump 127 and a portion ofsump 128.Chamber 131 spans the remainder ofsump 128.. Each ofchambers port top 121. Set apart from bottom. 122 insump 128 is positioningroller 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 insumps baffle 125.Baffle 125 is of sufficient height to keep the workingfluid 140 contained insumps baffle 125 is not so high that a portion of workingfluid 140 insump 128 cannot spill over intosump 127.Heating elements 141 located insump 127boil working fluid 140 to produce a vapor more dense than air. The resulting vapor forms avapor zone 142 which partially fillschamber 130. The height ofvapor zone 142 is controlled inchamber 130 by a plurality ofcondenser elements sidewall 123 and baffle 126, respectively. - As illustrated in FIG. 2A,
flexible circuit web 100 passes overfeed roller 150, entersport 133 inchamber 131, passes into workingfluid 140, and is routed aboutroller 129. The temperature of workingfluid 140 insump 128 is maintained below the solder eutectic temperature ofsolder coating 104 onweb 100 bytemperature control element 138. However, the temperature is high enought to perform some preheating ofweb 100. - After passage around
roller 129,web 100 withsolder coating 104 thereon passes intovapor zone 142. The heated vapors invapor zone 142 condense onto the relatively cool web, thereby effectively heatingweb 100 to a temperature above the solder liquidus temperature, meltingsolder coating 104 and causing it to reflow. During reflow,web 100 is moved in a planar orientation at a selectable angle with respect to a horizontal plane. This orientation ensures thatsolder coating 104, after reflow, is maintained at a generally uniform thickness while in its molten state. - Following passage through
vapor zone 142,flexible circuit web 100 passes throughcooling element 139,diffusion trap 134, and out throughport 132 infirst chamber 130 where it passes over a cooleddischarge roller 151 to a take-up reel (not shown). The cooling ofdischarge roller 151 is accomplished in a well-known manner and, hence, the details of such cooling are not specifically illustrated. To prevent solder smearing, some form of cooling is desirable prior toweb 100 being brought into contact withdischarge roller 151. In this embodiment, after passage throughvapor zone 142 sufficient quantities of vapor condensate are retained onweb 100 such that during the remainder of thetime web 100 is contained withinchamber 130 the condensate film evaporatively cools the reflowed solder below its eutectic temperature. - Escape of any vapors of working
fluid 140 throughports ports - In the alternate embodiment shown in FIG. 3,
flexible circuit web 100 is fed overroller 150 throughport 132 insidewall 123 and throughdiffusion trap 134 intochamber 130. Upon entry ofweb 100 intochamber 130, it is exposed tovapor zone 142. The hot vapors meltsolder coating 104 onweb 100, causing the solder to reflow. Following passage throughvapor zone 142,web 100 passes throughliquid seal 137 atexit port 136separating chamber 130 fromsump 128. Once insump 128,web 100 is further cooled by passage throughcooling elements 145. - To insure that
web 100 is maintained in a planar orientation during its passage throughvapor zone 142,positioning roller 129 insump 128 is used in conjunction withroller 150 to control the orientation ofweb 100 during this phase of the process. It should be noted that in the embodiment illustrated in FIG. 2A similar positioning effects are achieved withcomparable roller 151. - Additional cooling is provided following passage of
web 100 aroundroller 129, so that upon emerging fromsump 128,solder coating 104 onweb 100 is well below its euctectic temperature. At this point,web 100 is withdrawn fromchamber 131 throughdiffusion trap 135 and out throughport 133 where it passes overroller 151 and is taken up by a take-up reel (not shown). - Regardless of which embodiment is used, these embodiments being shown in FIGS. 2A and 3, one significant feature is that during passage of
web 100 throughvapor zone 142,web 100 is maintained in a planar orientation. This orientation insures a relatively uniform thickness of the layer ofsolder coating 104 onweb 100 following the reflow process. Another feature is that the use ofliquid seal 137 betweensumps fluid 140. Diffusion traps 134 and 135 at entry andexit ports fluid 140. - 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 onmachine 110 for aiding. in the threading offlexible circuit web 100 through the various chambers in the machine. Also specifically shown is apparatus which facilitates elevation of one end ofmachine 110 with respect to an opposite end thereof which apparatus controls the angle between a plane containing web 100- and a horizontal plane. - To aid in threading
flexible circuit web 100 through the various chambers inmachine 110, there are affixed to sidewall 123 a pair ofpulleys roller 150 andpulleys roller 151, are affixed totop 121. Additional idler pulleys 158 and 159 are affixed tosidewall 124. Similar idler pulleys (not shown) are affixed to the ends ofrollers 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 asimilar transport member 163.Transport members - In order to drive
transport members pulleys 154 and 1 55 ashaft 149 which has affixed thereon, at an intermediate point along its length, a drive pulley 147.Motor 146, mounted onsidewall 123, is coupled to drive pulley 147 by drive belt 148. Whenmotor 146 is actuated,shaft 149 rotates, and this rotation forcestransport members machine 110. - Coupled to transport
members bar 165.Bar 165, when fastened to transportmembers flexible circuit web 100 to be looped therearound and fastened onto itself. Upon actuation ofmotor 146,web 100 is carried viatransport members machine 110. Onceflexible circuit web 100 is threadably inserted through the various chambers inmachine 110,motor 146 is stopped and bar 165 can be removed fromtransport members flexible circuit web 100 can be brought into engagement with a take-up reel (not shown). Onceweb 100. is threadably inserted intomachine 110, the solder reflow process becomes continuous merely by fastening oneflexible circuit web 100 to another by means such as stapling the two webs together. - To facilitate elevation of one end of
machine 110, for a purpose to become apparent subsequently,machine 110 has abottom edge 192 affixed to frame 170 bypivot 171.Elevation strut 172, pivotally mounted to oppositebottom edge 191 ofmachine 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 ofstrut 172 . to frame 170 atong plurality ofapertures 173. Once the appropriate elevation is selected, strut 172 is held juxtaposed theappropriate aperture 173 by a holding pin (not shown). - The preferred embodiment of
machine 110 is shown in cross sectional view in FIG. 5A.Flexible circuit web 100 entersmachine 110 by downwardly deflecting wiper assembly 177 atentry port 133. Wiper assembly 177, similar to that shown in FIG. 7, along withbaffles 180 and 181 and the close spacing alongdiffusion trap 135, virtually prevent escape of any workingfluid 140 frommachine 110 at the point of entry offlexible circuit web 100. Following passage throughdiffusion trap 135,web 100 is immersed intofluid 140 insump 128 and is passed aroundroller 129.Roller 129positions web 100 for entry intochamber 130 so thatweb 100 will encountervapor zone 142 in a planar orientation below the vapor air interface. Moreover,temperature control element 138 controls the temperature offluid 140 so that it preheatssolder coating 104 onweb 100 to just below the solder eutectic temperature. In the event the temperature offluid 140 is sufficiently high so as to generate any vapors, these vapors, upon exposure todiffusiuon trap 135, are condensed into liquid form. Consequently,troughs 195 are provided at lower ends ofdiffusion trap 135 so that any recondensed vapors are returned tosump 128. rather than forming onweb 100. - After passing around
roller 129,web 100 is routed throughpassageway 136 separatingsump 128 fromvapor zone 142.Passageway 136 is formed bybaffle 126 which extends from top 121 downwardly to a point spaced apart frombottom 122. To preclude escape of vapors fromchamber 130; the fluid insump 128 is maintained at a level just abovepassageway 136. Hence,web 100 enterschamber 130 throughliquid seal 137. -
Vapor zone 142 inchamber 130 is generated by boilingfluid 140 insump 127 byheating elements 141. The temperature ofheating elements 141 is controlled in order to maintain fluid 140 in contact with them at a nearly uniform temperature. This is effected by makingheating 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 influid 140 and this, in turn, improves the usable lifetime offluid 140. - Control of the height of the vapor air interface is effected by
condenser elements chamber 130 containingvapor zone 142. The location ofcondenser elements machine 110 and the speed of travel ofweb 100 fixes the time of exposure ofsolder coating 104 onweb 100 tovapor zone 142. -
Baffles soldering coating 104 during its passage throughvapor zone 142. This results in a more uniform exposure ofweb 100 to the hot vapors ofvapor zone 142 and this in turn results in an improved cosmetic appearance offlexible circuit web 100 because the presence of air in the vicinity of the reflowed solder tends to oxidize the solder thereby dulling the finish. In order to prevent any droplets offluid 140 from enteringvapor zone 142, ademister unit 197 is provided insump 127. - During the passage of
flexible circuit web 100 throughvapor zone 142, the hot vaporsheat solder coating 104 above its liquidus temperature causing the solder to reflow. Sinceweb 100 is maintained in a planar orientation during this passage the effects of solder slumping are reduced andsolder coating 104 is provided with a more uniform distribution. Moreover, by controlling the transit time and planar angle ofweb 100 as it passes throughvapor zone 142, sufficient condensate is allowed to form onweb 100. - The formation of this condensate materially aids in the cooling of
web 100 as it passes betweenupper condenser element 184 andlower condenser element 185. Cooling at this point is desirable in order to bring the temperature ofsolder coating 104 below its eutectic temperature prior to its being brought into contact withroller 167. -
Upper condenser element 184, as shown in FIG. 5B, has a doghouse-like shape so that any condensate driven offweb 100 onto this condenser is prevented from dripping back ontoweb 100. To achieve this effectupper condenser element 184 includes oppositely directedmembers flexible circuit web 100. - As a first step in prohibiting escape of vapors of working
fluid 140,baffle 203 separateschamber 130 from the follow-on stages used to recapture any residual traces offluid 140 which may have a tendency to escape through web dragout. Following cooling by virtue of doghouse-shapedcondenser elements web 100 engages a plurality ofreheat rollers 167 through 169 and a corresponding plurality of diffusion traps 186, 190, and 134, respectively.Roller 167 anddiffusion trap 186 are separated fromroller 168 anddiffusion trap 190 bybaffles roller 168 anddiffusion trap 190 are separated fromroller 169 anddiffusion trap 134 bybaffles - Upon engagement of
web 100 with each ofrollers 167 through 169, it is reheated to a temperature just below the eutectic temperature ofsolder coating 104. This reheating vaporizes any residual traces of condensate offluid 140 so that upon enteringdiffusion traps web 100. The presence ofbaffles 187 through 189 ensures that with each successive stage lesser amounts of condensate are available for removal frommachine 110 by web dragout. - To facilitate return of the recaptured condensate to
sump 127 each of diffusion traps 186, 190 and 134 are provided withtroughs 195 at their lower extremities.Troughs 195 reduce the possibility of recaptured condensate coming into contact withweb 100. - Following passage of
web 100 aroundreheat roller 169 and throughdiffusion trap 134, it emerges throughexit port 132. To further inhibit escape of any vapor offluid 140,diffusion trap 134 is coupled to exitport 132 bybaffles exit port 132 is equipped with awiper assembly 178, as shown in FIG. 7, which further provides for removal of any traces of vapor offluid 140 carried byweb 100. - It should be noted that during passage of
web 100 throughvapor zone 142,web 100 is maintained in a planar orientation even at low web tensions. This effect is achieved withrollers input roller 150 and discharge roller 151 (Fig. 4). The manner in which this effect is achieved will become clear upon consideration of FIG. 6A. Moreover, as noted above,condenser elements web 100 and the angle of elevation ofbottom edge 191 with respect tobottom edge 192 ofmachine 110, the exposure time ofsolder coating 104 tovapor zone 142 can be accurately controlled. The manner of adjustment ofcondenser elements - Illustrated in FIG. 6A is apparatus for transporting
flexible circuit web 100 throughmachine 110 such thatweb 100 is maintained in a planar orientation at low web tension during its passage throughvapor zone 142. In particular,motor 220 mounted ontop 121, shown only in FIG. 6A for clarity, drivesdischarge roller 151 andintermediate rollers 167 through 169 bydrive chains 221. To control the tension inweb 100 as it is fed fromsupply roller 250, variablyadjustable tension roller 251 is used.Tension roller 251 is coupled to pneumaticconstant load device 253 bytension control arm 252. Coupled totension control arm 252 is tensionarm position sensor 254. - If the feed rate of
web 100 intomachine 110 slows down relative to the machine output speed, the amount ofweb 100 looped aroundtension roller 251 decreases andtension control arm 252 swings in an upward direction. Simultaneously, tensionarm position sensor 254 detects this change in position oftension control arm 252 and as a result an electrical signal is produced which causes drivemotor 220 to slow down. The decrease in rotational speed ofdrive motor 220 arrests the imbalance between the feed rate and machine output speed, thereby effectively controlling the amount of web looped aroundtension roller 251 so that the tension inweb 100 is held nearly constant during its passage throughmachine 110. - To further insure that
web 100 passes throughvapor zone 142 in a planar orientation,bottom edge 191 ofmachine 110 is adjustable with respect tobottom edge 192. This elevation adjustability aids in providing a more uniform thickness tosolder 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 onweb 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 ofcondenser elements condenser elements 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 viashafts 231 and 231' tohand cranks 232 and 232', respectively. - Since
condenser elements sump 127 without coming into contact withflexible circuit web 100. To achieve this end pans 230 and 230' are provided withtelescoping tubes 235 and 235' which couple pans 230 and 230' directly tosump 127 regardless of the position ofcondenser elements sump 127. This arrangement has the further effect of minimizing the production of excessively hot vapors needed to maintainvapor zone 142 and this, in turn, increases the useful lifetime of workingfluid 140. - 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 atexit port 132.Flexible membranes edges exit port 132 byrigid members web 100 emerges fomexit port 132,membranes web 100. This seal prevents any convective loss of vapor due toweb 100 dragging out the mixture of air and vapor existing neardiffusion trap 134. - As noted previously,
heating elements 141 are used to control the boiling rate offluid 140 and to avoid the production of hot spots thereby increasing the lifetime offluid 140. Besides makingheating 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 filtercapacitors 291. Following eachcapacitor 291 there is a parallel circuit comprised ofdiode 292 and a silicon controlledrectifier 293.Diode 292 provides rectification of the AC power and silicon controlledrectifier 293, by virtue of a trigger bias voltage coupled thereto, fairly accurately controls the amount of rectified power supplied toheating elements 141. This arrangement insures that allheating elements 141 are activated uniformly which, in turn, virtually eliminates hot spots influid 140 thereby increasing its useful lifetime. - In all cases it is to be understood that the above-described embodiments are but representative of many possible specific embodiments which can be devised readily in accordance with the principles of the disclosed invention.
Claims (10)
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 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0000284A1 EP0000284A1 (en) | 1979-01-10 |
EP0000284B1 true EP0000284B1 (en) | 1980-10-29 |
Family
ID=25208932
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP78300100A Expired EP0000284B1 (en) | 1977-07-01 | 1978-06-29 | Process and apparatus for reflowing solder of solder plated substrates and substrates formed thereby |
Country Status (8)
Country | Link |
---|---|
US (1) | US4115601A (en) |
EP (1) | EP0000284B1 (en) |
JP (1) | JPS5826194B2 (en) |
CA (1) | CA1081550A (en) |
DE (1) | DE2860255D1 (en) |
ES (1) | ES471324A1 (en) |
IE (1) | IE46960B1 (en) |
IT (1) | IT1096957B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3223471A1 (en) * | 1981-06-23 | 1983-01-20 | The HTC Corp., 01742 Concord, Mass. | DEVICE FOR CONTINUOUS STEAM PHASE TREATMENT OF WORKPIECES |
Families Citing this family (24)
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US4315042A (en) * | 1978-07-14 | 1982-02-09 | Hybrid Technology Corporation | Solder removal technique |
DE3064754D1 (en) * | 1979-07-09 | 1983-10-13 | Electrovert Ltd | Method and apparatus for vapour phase soldering |
JPS58197A (en) * | 1981-06-25 | 1983-01-05 | 日本メクトロン株式会社 | Method and device for soldering flexible circuit board |
JPS5822768U (en) * | 1981-08-04 | 1983-02-12 | 上村工業株式会社 | Reflow processing equipment for printed circuit boards |
US4558524A (en) * | 1982-10-12 | 1985-12-17 | Usm Corporation | Single vapor system for soldering, fusing or brazing |
FR2553186B1 (en) * | 1983-10-11 | 1988-10-14 | Piezo Ceram Electronique | IMPROVEMENTS IN MACHINES FOR HEATING ARTICLES OR PRODUCTS BY CONDENSATION OF STEAM THEREON |
FR2556083B1 (en) * | 1983-10-11 | 1986-04-25 | Piezo Ceram Electronique | IMPROVED MACHINE FOR HEATING AN ARTICLE OR PRODUCT BY CONDENSATION OF STEAM THEREON |
US4685605A (en) * | 1984-05-25 | 1987-08-11 | The Htc Corporation | Continuous solder system |
US4697730A (en) * | 1984-05-25 | 1987-10-06 | The Htc Corporation | Continuous solder system |
DE3673880D1 (en) * | 1985-06-08 | 1990-10-11 | Nippon Dennetsu Keiki Kk | STEAM PHASE SOLDERING DEVICE. |
JPS6224859A (en) * | 1985-07-24 | 1987-02-02 | Kenji Kondo | Soldering device |
US4766677A (en) * | 1986-05-27 | 1988-08-30 | Detrex Chemical Industries, Inc. | Method and apparatus for vapor phase soldering |
US4805828A (en) * | 1987-01-23 | 1989-02-21 | Rockwell International Corporation | Thermally durable surface mounted device printed wiring assemblies and apparatus and method for manufacture and repair |
US4801069A (en) * | 1987-03-30 | 1989-01-31 | Westinghouse Electric Corp. | Method and apparatus for solder deposition |
US4762264A (en) * | 1987-09-10 | 1988-08-09 | Dynapert-Htc Corporation | Vapor phase soldering system |
US4782991A (en) * | 1987-11-24 | 1988-11-08 | Unisys Corporation | Hot liquid solder reflow machine |
US5030805A (en) * | 1990-02-20 | 1991-07-09 | Minnesota Mining And Manufacturing Company | Condensation heating apparatus |
US5452401A (en) | 1992-03-31 | 1995-09-19 | Seiko Epson Corporation | Selective power-down for high performance CPU/system |
US5542596A (en) * | 1994-12-20 | 1996-08-06 | United Technologies Corp. | Vapor phase soldering machine having a tertiary cooling vapor |
DE19826520C1 (en) * | 1998-06-15 | 1999-12-02 | Helmut Walter Leicht | Process for controlling heat transfer to a workpiece in vapor phase soldering |
JP2000244108A (en) * | 1999-02-22 | 2000-09-08 | Senju Metal Ind Co Ltd | Soldering of printed board, soldering equipment for printed board, and cooling equipment therefor |
US20100308103A1 (en) * | 2009-06-08 | 2010-12-09 | Tyco Electronics Corporation | System and method for vapor phase reflow of a conductive coating |
US9930789B2 (en) | 2010-04-12 | 2018-03-27 | Seagate Technology Llc | Flexible printed circuit cable with multi-layer interconnection and method of forming the same |
ITUB20152805A1 (en) * | 2015-08-03 | 2017-02-03 | Piaggio & C Spa | Rotating shaft device |
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US3067056A (en) * | 1959-10-15 | 1962-12-04 | Robert K Remer | Improvements in printing with ink composition having volatile solvents |
US3346413A (en) * | 1964-10-12 | 1967-10-10 | Hooker Chemical Corp | Method and apparatus for coating wire and solvent recovery |
DE1546009B2 (en) * | 1966-09-03 | 1971-04-29 | GT Schjeldahl Co , Northfield, Minn (V St A) | METHOD OF MANUFACTURING PRINTED CIRCUITS |
US3704165A (en) * | 1967-07-06 | 1972-11-28 | Brown Eng Co Inc | Solder leveling method |
US3707762A (en) * | 1970-10-29 | 1973-01-02 | North American Rockwell | Methods of using fluxes in joining metal surfaces |
BE787366A (en) * | 1971-08-09 | 1973-02-09 | Dow Chemical Co | METHOD OF MODIFYING THE SURFACE CONDITION OF PLASTICS |
US3904102A (en) * | 1974-06-05 | 1975-09-09 | Western Electric Co | Apparatus and method for soldering, fusing or brazing |
SE424518B (en) * | 1973-09-07 | 1982-07-26 | Western Electric Co | PROCEDURE AND DEVICE FOR SOFT, MOLDING OR HARDWARE |
US3866307A (en) * | 1973-09-07 | 1975-02-18 | Western Electric Co | Method for soldering, fusing or brazing |
US4032033A (en) * | 1976-03-18 | 1977-06-28 | Western Electric Company, Inc. | Methods and apparatus for heating articles |
-
1977
- 1977-07-01 US US05/812,230 patent/US4115601A/en not_active Expired - Lifetime
-
1978
- 1978-06-27 CA CA306,313A patent/CA1081550A/en not_active Expired
- 1978-06-29 EP EP78300100A patent/EP0000284B1/en not_active Expired
- 1978-06-29 DE DE7878300100T patent/DE2860255D1/en not_active Expired
- 1978-06-30 ES ES471324A patent/ES471324A1/en not_active Expired
- 1978-06-30 IE IE1327/78A patent/IE46960B1/en unknown
- 1978-06-30 IT IT25259/78A patent/IT1096957B/en active
- 1978-07-01 JP JP53079279A patent/JPS5826194B2/en not_active Expired
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3223471A1 (en) * | 1981-06-23 | 1983-01-20 | The HTC Corp., 01742 Concord, Mass. | DEVICE FOR CONTINUOUS STEAM PHASE TREATMENT OF WORKPIECES |
Also Published As
Publication number | Publication date |
---|---|
IE46960B1 (en) | 1983-11-16 |
ES471324A1 (en) | 1979-02-01 |
US4115601A (en) | 1978-09-19 |
IT7825259A0 (en) | 1978-06-30 |
JPS5418070A (en) | 1979-02-09 |
CA1081550A (en) | 1980-07-15 |
IE781327L (en) | 1979-01-01 |
JPS5826194B2 (en) | 1983-06-01 |
EP0000284A1 (en) | 1979-01-10 |
DE2860255D1 (en) | 1981-01-29 |
IT1096957B (en) | 1985-08-26 |
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