CA1249069A - Mass solderng system - Google Patents
Mass solderng systemInfo
- Publication number
- CA1249069A CA1249069A CA000521540A CA521540A CA1249069A CA 1249069 A CA1249069 A CA 1249069A CA 000521540 A CA000521540 A CA 000521540A CA 521540 A CA521540 A CA 521540A CA 1249069 A CA1249069 A CA 1249069A
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- solder
- tubular shell
- wave
- inner tubular
- shell
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Abstract
ABSTRACT
MASS SOLDERING SYSTEM
A soldering system is described in which a fluid stream is directed onto a solder board substantially immediately following the deposition of molten solder onto the boards. The apparatus includes a pair of concentric slotted tubular shells wherein one shell rapidly rotates relative to about the other to create a plurality of different angles of impingement of the air on each area of the bottom surface of the circuit board.
MASS SOLDERING SYSTEM
A soldering system is described in which a fluid stream is directed onto a solder board substantially immediately following the deposition of molten solder onto the boards. The apparatus includes a pair of concentric slotted tubular shells wherein one shell rapidly rotates relative to about the other to create a plurality of different angles of impingement of the air on each area of the bottom surface of the circuit board.
Description
MASS SOLDERING SysTEM
Backqround of the Invention The present invention is directed to an improvement in a mass soldering system of the type described in the 5 earlier United States patents of H.T. O'Rourke, Nos.
4410126 and 4401253. This prior patented system involves directing a hot air knife blast onto the bottom surface of a printed component~carrying circuit board, the air blast impingi.ng on the surface immediately after 10 the printed circuit board leaves a wave soldering system. The impinging air blast is reported to reduce the incidence of solder shorts, icicling and/or bridging, and has achieved widespread adoption.
In working with the previously patented system of 15 O'Rourke, it has been found that with certain types of components, different angles of air blast give optimum solder removal to prevent solder shorts, icicling and/or bridging.
Brief SummarY of the In ention In commonly owned U.S. Patent No. 4664308 issued May 12, 1987, there is described an improvement in the mass soldering system of the type described in the above mentioned patents of O'Rourke in which there is provided a pulsating or a sweeping air blast at a plurality of 25 different angles of impingement of the air on each area of the bottom surface of the circuit board as it leaves : the solder wave. As a result of the provision of a pulsating or a sweeping air blast, each area o-E the circuit board is subjected to hot air blasts coming from 30 a plurality of different angles so that, no matter what type of circuit element is connected to the board at any particular point, it will, at some time during the pulsating or sweeping motion of the air blast, be subjected to that angle which is optimum for removal of 35 the solder constituting potential solder shorts, icicles and/or bridges. The present invention provides an ~' , improved mechanism and means for achieving a continuously sweeping air blast.
In accordance with the present invention there is 5 provided an apparatus for mass joining with solder electrical and electronic components assembled on a circuit board wherein the components have leads which protrude therefrom. The apparatus comprises in combination: a wave soldering station adapted to provide 10 a wave of molten solder; means for transporting the circuit board across the solder whereby a quantity of molten solder may be deposited onto the circuit board underside and the protruding leads; and an excess solder removal station adjacent the wave soldering station.
15 The excess solder removal station is adapted to impinge a sweeping fluid blast of continuously varying angle of impingement directed towards the solder wave onto the bottom surface of the board sufficiently soon after it leaves the solder wave so that the solder is still 20 molten, the sweeping fluid blast having sufficient velocity to remove essentially all bridges and shorts but not sufficient velocity to adversely affect properly wetted joints, whereby each portion of the bottom surface of the board may be subjected to a sweeping 25 fluid blast from a plurality of different angles. The excess solder removal station comprising a first fixedly positioned inner or outer tubular shell having at least one inlet and having at least one open portion directed toward the point where the boards exit the wave, and a 30 second rotatably mQunted outer or inner tubular shell having a plurality of elongated spaced slots formed therein, means for rotating the outer tubular shell and fluid supply means for connection to the inlet, the outer tubular shell encompassing and rotating about the 35 inner tubular shell such that fluid emanating from the inner tubular shell will be directed by the open portion - 2a -of ~he inner tubular shell throuyh the slot of the outer shell to form a sweeping fluid blast.
Detailed Descri~tion of the Invention In order to more fully understand the invention, reference should be had to the following detailed description of a preEerred form of the invention, this description being largely based on the previously lo patented invention described in U,s, Patent 4410126, the disclosure of which is embodied herein in its entirety.
For a fuller understanding of the objects of the present invention, reference should be had to the following detailed description taken in connection with the 15 accompanying drawing in which like numerals depict like parts, and:-Fig.1 is a side elevational view partly in sectionof one form of soldering apparatus made in accordance with the present invention and which provides a sweeping 20 air blast of continuously varying impingement angle to the underside of a circuit board as it leaves the wave solder;
Fig. 2 is a side elevational view partly in section of a soldering apparatus showing a second embodiment of 25 the invention and providing a sweeping air blast of continuously varying impingement angle to the underside of a circuit board as it leaves the solder wave;
Fig. 3 is a top plan view partly in section of the sweeping air blast portion of the apparatus of Fig. 1;
FigO 4 is a top plan view partly in section of the sweeping air blast portion of ~he apparatus of Fig. 2.
Fig. 5 is a side elevational view partly in section of a third embodiment of a soldering apparatus, made in accoxdance with the present invention, providing a 35 sweeping air blast of a continuously varying impingement ' ~:
angle ~o the underside of a circuit board as it leaves the solder wave;
Fig. 6 is a side elevational view partly in sect;on of a fourth embodimen~ of a soldering apparatus~ made in 5 accordance with the invention, provid;ng a sweeping air blast of a continuous varyin~ impingemen1: angle to the unders;de of a circuit board as it leaves the solder ~ave;
Fig. 7 is a side elevational view partly in section lOof a fifth embodiment of a wave soldering apparatus, made ;n accordance w;th the invention, provid;ng pulsating air blasts at a plurality of different imp;ngement angles to the unders;de of a circuit board as it leaves the solder wave;
Fig. 8 i5 a side elevational view partly in sect;on of a sixth embodiment of a wave soldering apparatus, made in accordance with the invention, providing a pulsating air blast of a continuously varying impingement angle to the underside of a circu;t board as 20it leaves the soLder wave; and Fig. 9 is a top plan view vf the staggered slot arrangement employed in the third embod;ment shown in Figure S.
In the following detailed description of the present 25;nvention, various terms such as components~ leads, solder, etc., shall have the same meaning as described in more detaiL in the above mentioned UnS~ Patent Nos.
4410126 and 4401253 of O'Rourke.
For convenience, Figures 1, 2 and S through 8 in the 30present ;nvention are illustrated as a modification of F;g. 2 of the above ment;oned U.S. No. Patent 4410126, and reference numerals employed ;n the pr~sent draw;ng are the same as those used in Fig~ 2 o~ the earlier U.S.
Patent No. 4410120.
Referr;ng to Figures 1 and 3 of the draw;ngs, the pr;nted c;rcuit board, after pass;ng through standard fluxing and preheat;ng stat;ons, is passed through a mass wave solder;ng stat;on 36. The components 24 may be mounted on the upper surface of the board w;th leads protruding downwardly through holes ;n the board and/or may be secured to the bottom surface of the board ~such as by means of an adhes;ve) w;th the leadls protrud;ng therefrom to contact lands on the board. In both cases lo the mass soldering stat;on completes the electrical and mechanical connections of the component leads to the board. The mass wave so~der;ng stat;on ;n~ludes a container of conventional des;gn ;nd;cated generally at 40 for hold;ng a supply of molten solder 42.
15 Convent;onal heat;ng means (not shown) may be secured to the bottom and/or s;de walls of conta;ner 40 or ;mmersed ;n the solder to heat and ma;nta;n the supply of solder 42 in molten condit;on.
A sump and nozzle assembly ;nd;cated generally at 44 20 ;5 disposed inter;orly of conta;ner 40. The sump and nozzle assembly 44 is of convent;onal des;gn and typically compr;ses a rounded bottom wall 46~ a pair of substant;ally vertically opposed end walls (not shown) and a pair of ;nclined side walls 52 and 54. The upper 25 ends of end walls and s;de walls 52 and 54 are spaced from one another to form a narrow elongated rectangular no~le or slot 56 wh;ch extends above the molten solder level ;n conta;ner 40 for a su;table distance, e.g~ one inch above the molten solder leveL.
Preferably, the sump also ;ncludes a pa;r of adjustable sluice plates 58A, s8e spaced from the sump s;de walls 52 and 54 for controlling solder overflow from the nozzle 56, eLg. ;n accordance w;th the teach;ngs of U~S~ Patent No~ 3398873 to Kenneth G.
35 Boynton and Howard W. Wegener. Completing the soldering station is a variable speed pump ~not shown) which communicates through an ;ntake orif;ce 59 in the lower end of sump and no7zle assembly ~ for pump;ng solder into the sump where ;t then rises and overflows the nozzle 56 as a stand;ng solder wave.
An ;mportant feature and cr;t;cal requirement of the present ;nvention ;s the ab;lity to relocate excess solder on, and/or remove excess solder from the bottom of the c;rcuit board, and from any interconnections~
o component leads and/or component bod;es carr;ed thereon, before the solder can solidify as shorts, ;cicles and/or bridges. This ;s accomplished by treat;ng the soldered c;rcu;t board and depending co~ponent leads at an excess solder re~oval station 6n. Excess soLder removal 15 station 60 follows soldering stat;on 36 immed;ately in-l;ne and is designed to relocate or blo~ off excess solder from the board unders;de before the solder solidifies as shorts, icicles and/or bridges. Solder removal station 60 comprises one or more fluid jets, 20 flu;d knives, slots, nozzles or the like and the apparatus is ind;cated generally at 62, from ~h;ch a heated flu;d stream, e.g. hot a;r, can be d;rected onto the unders;de of the board 20. Flu;d flow rate, -fluid pressure, and flu;d temperature and the t;me elapsed 25 between circu;t board emersion from the solder wave and beg;nning of contact by the fluid stream may vary widely depending on the board temperature, ambient temperature, melting po;nt o~ the solder, spec;f;c heat of flu;d and heat transfer coeff;cient of flu;d to the board, board 30size and shape, component dens;ty, amount of solder depos;ted and to be re~oved, conveyor speed, and distance bet~een the solder;ng station and the excess solder removal stat;on~ Preferably apparatus 62 is d;sposed prox;mate thè path of~travel of the boards.
3sApparatus 62 of course must be spaced suff;ciently belo~
the path of travel of the boards to perm;t clearance of the Longest depend;ng lead~ etc. Inert gas may be used as the fluid, but prefer3bly the impinging fluid compr;ses air. The fluid should be pre-heated to a temperature above that of the molten solder ;n the soldering station (which for standard 63~37 solder i~
approximately 260C)o and preferably w;ll be pre-heated to a temperature in the range of about 280 C. to 400 C., more preferably about 370 C~ to 10 400 C. (measured at the outlet of apparatus 62). For 63/37 solder alloy, the preferred fluid preheat temperature ;s about 370 C. (measured at the outlet of slot 105, 205)~
The pulsating or sweeping flu;d stream impinging on 15 still molten solder contained on the underside of the circuit board, the interconnections, and the component leads and/or bod;es, relocates excess solder on, and~or blasts excess solder from the underside of the board~
;nterconnections, leads, and bod;es, and ;n do;ng so 20 also minimizes the possib;lity of solder briding or icicl;ng or short format;on upon sol;d;fication.
Referring to F;gures 1 and 3~ in one embodiment of the present invention, the fluid stream~ e.g~ a;r is suppl;ed by flu;d supply means, generally ind;cated by 2s 115, through ducting 116 ;nto one or both ends of inner tubular shell 110 ~hich is non-rotatable. The opposite end of inner tubular shell 110r ;f it ;s not used for supplying 3i r~ is sealed so that the air is only allowed to escape through an open portion or elongate slot 140.
30The open portion 140 is a rectangular portion ~hich has been cut out of the sidewall of the inner tubular shell 110, the length which ;s determined by the ~idth of the mass soldering ronveyor system and the width of which ;s determined by the desired maximum angle of impingement 3sfor the apparatus. Completely enclosing the inner tubular shelL 110 ;s an outer tubular shell 100 ~h;ch rotates about the ;nner shell 110 on bearings means 1Z0 (see Fig. 3)~ The outer tubular shell 100 has lony;tud;nal slots 105a~ br c~.~ wh;ch run lengthw;se 5 perpendicular to the c;r~umference of outer tubular shell 100, the length being substantially equal to the length of open portion 140 and the width be;ng narrow enough to prov;de a suff;c;ent flu;d veloc;ty. The slots 105 are equally spaced apart around the lOcjrcumference of tubuLar shell 100 such that only one slot 105, at any given time, is able to be pos;t;oned over open port;on 140. Seals 103 may be util;zed, depending upon the clearance bet~een the ;nner and ou~er shells, to ensure that the air, from inner tubular shell 15110, is suppl;ed only to the slot 105 pos;t;oned over open port1On 140. It may be desirable, depending on the total area of open portion 140, to prov;de an a;r distribut;on plate 150 to equal;ze the fluid flow being emitted out from open port;on 140 of the ;nner tubular 20shell 110, which teach;ng is well known ;n the air distribut;on art~
The ;nvent;on ~orks as follows~ As outer tubular shell 100 rotates by motor 132 driven dr;ve means, generally ;nd;cated as 135, about the open portion 140 25Of inner tubular shell 110~ air is d;rected through open portion 140~ and d;str;bution plate 150, and forced out through the slot 105a of the outer tubing 100 wh;ch is pos;t;oned over open portion 140~ S;nce outer tu~ular shell 100, along w;th slot 105a, are rotat;ng, the air 30blast forced through slot 105a ;s also g;ven a rotational s~eep;ng movement unt;l the slot 105a rotates past the tra;ling edge ~30 of open portion 1~0 and ;s no longer able to communicate with open portion 140~ At that ti~e, a subsequent slot 105b is then posit;oned 35Over the leading edge 125 of open portion 1~0 and ;
supplied with air to form a subsequent sweeping air blast. As this second slot 105b rotates over open port;on 1~0, the second a;r blast ;s also given a correspond;ng rotat;onal sweeping movement unt;l ;t no longer is positioned over any part of open port;on 1l~0 Th;s procedure is repeated as each subsequent slot 105c... ;s pos;t;oned over the Lead;ng edge 125 of open portion 140.
An alternat;ve embod;ment of the present ;nvent;on lO;S shown ;n F;gures 2 and 4. In the embod;ment shown ;n F;gures 2 and 4, the outer tubular shell 200 is f;xed ;n pos;t;on, and has an open port;on or elongate slot 240 d;rected toward the unders;de of the travel;ng boards 20 wh;le the ;nner tubular shell 210 ;s the rotat;ng member 15wh;ch generates the sweep;ng air blast. As can be seen by compar;ng the two embod;ments as shown, F;gures 3 and 4, open port;on 240 (F;gure 4~ ;s substant;ally wider than open portion 140 (Figure 3). Inner tubular shell 210 is rotatably dr;ven by su;table motor 232 dr;ven 20dr;ve means, generally ;nd;cated as 235~ The a;r ;s suppl;ed by way of flu;d supply meins 115 through ducting 116 and an air tight rotating joint indicated generally at 245 ints one or both end portions of inner rotat;ng shell 210~ The outer tubular sheLl may have 25seals 203 secured to the ins;de of outer tubular shell 200 along the perimeter of open port;on 240. The inner tubular shell 210 has slots 205a, b~ c... wh;ch run lengthwise, perpendicular to the c;rcumference of the inner tubular shell 210~ The slots 205 are spaced 30apart along ;ts circumference such that only one slot 205 is able to communicate with open portion 240, at any given time. Thus, a sweeping air blast controlled by slot 205 is also ob~ained by rotating inner tubing 210 in either the clockwise and counter-clockwise direction.
The angle of ;mp;ngement may be var;ed over a ~;dn range~ preferably between about 30 and about 75, more preferably about 45 to about 65 by suitable selection of slot sizesD The angle of impingement of the air blast relat;ve to the c;rcu;t board should be cont;nuously rapidly varied over the aforesa;d range so that each port;on of the board ;s subjected to an a;r blast over a w;de range of angles. Preferably, the complete cycle of angles ;s repeated every 0.05 to 1.0 lo seconds, more preferably every 0.1 to 0.15 seconds.
Cycle t;me may read;ly be controlled by adjust;ng the rotational speed of the rotat;ng shells.
At leas~ four other poss;ble var;at;ons of the above disclosed embod;ments are foreseen each of which does 15 not depart from the sp;rit and scope of the present invent;on. These embod;ments are shown diagramatically in the draw;ngs, Figures 5 through 8, and are only briefly described below s;nce their detail description is more fully explained above in relation to the two 20other embodiments.
F;gure S discloses a third embodiment ;n which inner tubular shell 510 rotates inside of outer tubular shell S00 similar to the above-disclosed second embod;mentO
The major var;ations in this embod;ment is that inner 25tubular shelL 510 contains a plurality of staggered long;tud;nal slots 505 a, b, c, d ~a (as sho~n ;n Figure 9) instead of long, cont;nuous slots.
A var;ation of the th;rd embod;ment is shown in F;gure 6, wherein inner tubular shell 610 rotates ;nside 30Of a fixed box shell 600, instead of a tubular shelln The box shell 6ûO is completely sealed except for open portion 640 which controls and defines the owtput direction of the s~eeping air blasts.
lo A f;fth embodiment ;s d;sclosed ;n F;gure 7 where;n the outer tubular shell 700 conta;ns a plurality of smaller rectangular openings 74Qa, b, c, ~.., instead of a s;n~le large rectangular open portion. The inner 5 tubular shell 710 rotates inside of the outer tubular shell 7no and contains a plurality of longitudinal slots 705a~ b, c .... The slots 705 are arranged so that only one slot 705 can communicate with the open portion, rectangular open port;ons 740a, b, c~.., at any g;ven time. Therefore, a pulsating air blast is generated as the slots 705 communicate sequentially with the open portions 740.
A final embod;ment is disclosed in figure 8 ~herein an outer tubular shell 800, having a plurality o~ air 15foils 825 situated long;tudinally along the outer tubular shell and compr;sing the side wall of the tubular shell, rotates about a fixed inner tubular shell 810 having an open portion 840, directed toward the underside of a circuit board 20 to be treated. The air ~ foils 825, as they rotate about the slot 840, either deflect or allow the air to pass stra;ght through, thus resulting in a pulsating air blast to the unders;de of the circuit board 20.
Still other changes will be obvious to one sk;lled 25in the art. Accord;ngly, it is intended that all matter conta;ned in the above descript;on or shown in the accompanying drawings shall be interpreted in an illustrative and not ;n a limiting sense.
3a
Backqround of the Invention The present invention is directed to an improvement in a mass soldering system of the type described in the 5 earlier United States patents of H.T. O'Rourke, Nos.
4410126 and 4401253. This prior patented system involves directing a hot air knife blast onto the bottom surface of a printed component~carrying circuit board, the air blast impingi.ng on the surface immediately after 10 the printed circuit board leaves a wave soldering system. The impinging air blast is reported to reduce the incidence of solder shorts, icicling and/or bridging, and has achieved widespread adoption.
In working with the previously patented system of 15 O'Rourke, it has been found that with certain types of components, different angles of air blast give optimum solder removal to prevent solder shorts, icicling and/or bridging.
Brief SummarY of the In ention In commonly owned U.S. Patent No. 4664308 issued May 12, 1987, there is described an improvement in the mass soldering system of the type described in the above mentioned patents of O'Rourke in which there is provided a pulsating or a sweeping air blast at a plurality of 25 different angles of impingement of the air on each area of the bottom surface of the circuit board as it leaves : the solder wave. As a result of the provision of a pulsating or a sweeping air blast, each area o-E the circuit board is subjected to hot air blasts coming from 30 a plurality of different angles so that, no matter what type of circuit element is connected to the board at any particular point, it will, at some time during the pulsating or sweeping motion of the air blast, be subjected to that angle which is optimum for removal of 35 the solder constituting potential solder shorts, icicles and/or bridges. The present invention provides an ~' , improved mechanism and means for achieving a continuously sweeping air blast.
In accordance with the present invention there is 5 provided an apparatus for mass joining with solder electrical and electronic components assembled on a circuit board wherein the components have leads which protrude therefrom. The apparatus comprises in combination: a wave soldering station adapted to provide 10 a wave of molten solder; means for transporting the circuit board across the solder whereby a quantity of molten solder may be deposited onto the circuit board underside and the protruding leads; and an excess solder removal station adjacent the wave soldering station.
15 The excess solder removal station is adapted to impinge a sweeping fluid blast of continuously varying angle of impingement directed towards the solder wave onto the bottom surface of the board sufficiently soon after it leaves the solder wave so that the solder is still 20 molten, the sweeping fluid blast having sufficient velocity to remove essentially all bridges and shorts but not sufficient velocity to adversely affect properly wetted joints, whereby each portion of the bottom surface of the board may be subjected to a sweeping 25 fluid blast from a plurality of different angles. The excess solder removal station comprising a first fixedly positioned inner or outer tubular shell having at least one inlet and having at least one open portion directed toward the point where the boards exit the wave, and a 30 second rotatably mQunted outer or inner tubular shell having a plurality of elongated spaced slots formed therein, means for rotating the outer tubular shell and fluid supply means for connection to the inlet, the outer tubular shell encompassing and rotating about the 35 inner tubular shell such that fluid emanating from the inner tubular shell will be directed by the open portion - 2a -of ~he inner tubular shell throuyh the slot of the outer shell to form a sweeping fluid blast.
Detailed Descri~tion of the Invention In order to more fully understand the invention, reference should be had to the following detailed description of a preEerred form of the invention, this description being largely based on the previously lo patented invention described in U,s, Patent 4410126, the disclosure of which is embodied herein in its entirety.
For a fuller understanding of the objects of the present invention, reference should be had to the following detailed description taken in connection with the 15 accompanying drawing in which like numerals depict like parts, and:-Fig.1 is a side elevational view partly in sectionof one form of soldering apparatus made in accordance with the present invention and which provides a sweeping 20 air blast of continuously varying impingement angle to the underside of a circuit board as it leaves the wave solder;
Fig. 2 is a side elevational view partly in section of a soldering apparatus showing a second embodiment of 25 the invention and providing a sweeping air blast of continuously varying impingement angle to the underside of a circuit board as it leaves the solder wave;
Fig. 3 is a top plan view partly in section of the sweeping air blast portion of the apparatus of Fig. 1;
FigO 4 is a top plan view partly in section of the sweeping air blast portion of ~he apparatus of Fig. 2.
Fig. 5 is a side elevational view partly in section of a third embodiment of a soldering apparatus, made in accoxdance with the present invention, providing a 35 sweeping air blast of a continuously varying impingement ' ~:
angle ~o the underside of a circuit board as it leaves the solder wave;
Fig. 6 is a side elevational view partly in sect;on of a fourth embodimen~ of a soldering apparatus~ made in 5 accordance with the invention, provid;ng a sweeping air blast of a continuous varyin~ impingemen1: angle to the unders;de of a circuit board as it leaves the solder ~ave;
Fig. 7 is a side elevational view partly in section lOof a fifth embodiment of a wave soldering apparatus, made ;n accordance w;th the invention, provid;ng pulsating air blasts at a plurality of different imp;ngement angles to the unders;de of a circuit board as it leaves the solder wave;
Fig. 8 i5 a side elevational view partly in sect;on of a sixth embodiment of a wave soldering apparatus, made in accordance with the invention, providing a pulsating air blast of a continuously varying impingement angle to the underside of a circu;t board as 20it leaves the soLder wave; and Fig. 9 is a top plan view vf the staggered slot arrangement employed in the third embod;ment shown in Figure S.
In the following detailed description of the present 25;nvention, various terms such as components~ leads, solder, etc., shall have the same meaning as described in more detaiL in the above mentioned UnS~ Patent Nos.
4410126 and 4401253 of O'Rourke.
For convenience, Figures 1, 2 and S through 8 in the 30present ;nvention are illustrated as a modification of F;g. 2 of the above ment;oned U.S. No. Patent 4410126, and reference numerals employed ;n the pr~sent draw;ng are the same as those used in Fig~ 2 o~ the earlier U.S.
Patent No. 4410120.
Referr;ng to Figures 1 and 3 of the draw;ngs, the pr;nted c;rcuit board, after pass;ng through standard fluxing and preheat;ng stat;ons, is passed through a mass wave solder;ng stat;on 36. The components 24 may be mounted on the upper surface of the board w;th leads protruding downwardly through holes ;n the board and/or may be secured to the bottom surface of the board ~such as by means of an adhes;ve) w;th the leadls protrud;ng therefrom to contact lands on the board. In both cases lo the mass soldering stat;on completes the electrical and mechanical connections of the component leads to the board. The mass wave so~der;ng stat;on ;n~ludes a container of conventional des;gn ;nd;cated generally at 40 for hold;ng a supply of molten solder 42.
15 Convent;onal heat;ng means (not shown) may be secured to the bottom and/or s;de walls of conta;ner 40 or ;mmersed ;n the solder to heat and ma;nta;n the supply of solder 42 in molten condit;on.
A sump and nozzle assembly ;nd;cated generally at 44 20 ;5 disposed inter;orly of conta;ner 40. The sump and nozzle assembly 44 is of convent;onal des;gn and typically compr;ses a rounded bottom wall 46~ a pair of substant;ally vertically opposed end walls (not shown) and a pair of ;nclined side walls 52 and 54. The upper 25 ends of end walls and s;de walls 52 and 54 are spaced from one another to form a narrow elongated rectangular no~le or slot 56 wh;ch extends above the molten solder level ;n conta;ner 40 for a su;table distance, e.g~ one inch above the molten solder leveL.
Preferably, the sump also ;ncludes a pa;r of adjustable sluice plates 58A, s8e spaced from the sump s;de walls 52 and 54 for controlling solder overflow from the nozzle 56, eLg. ;n accordance w;th the teach;ngs of U~S~ Patent No~ 3398873 to Kenneth G.
35 Boynton and Howard W. Wegener. Completing the soldering station is a variable speed pump ~not shown) which communicates through an ;ntake orif;ce 59 in the lower end of sump and no7zle assembly ~ for pump;ng solder into the sump where ;t then rises and overflows the nozzle 56 as a stand;ng solder wave.
An ;mportant feature and cr;t;cal requirement of the present ;nvention ;s the ab;lity to relocate excess solder on, and/or remove excess solder from the bottom of the c;rcuit board, and from any interconnections~
o component leads and/or component bod;es carr;ed thereon, before the solder can solidify as shorts, ;cicles and/or bridges. This ;s accomplished by treat;ng the soldered c;rcu;t board and depending co~ponent leads at an excess solder re~oval station 6n. Excess soLder removal 15 station 60 follows soldering stat;on 36 immed;ately in-l;ne and is designed to relocate or blo~ off excess solder from the board unders;de before the solder solidifies as shorts, icicles and/or bridges. Solder removal station 60 comprises one or more fluid jets, 20 flu;d knives, slots, nozzles or the like and the apparatus is ind;cated generally at 62, from ~h;ch a heated flu;d stream, e.g. hot a;r, can be d;rected onto the unders;de of the board 20. Flu;d flow rate, -fluid pressure, and flu;d temperature and the t;me elapsed 25 between circu;t board emersion from the solder wave and beg;nning of contact by the fluid stream may vary widely depending on the board temperature, ambient temperature, melting po;nt o~ the solder, spec;f;c heat of flu;d and heat transfer coeff;cient of flu;d to the board, board 30size and shape, component dens;ty, amount of solder depos;ted and to be re~oved, conveyor speed, and distance bet~een the solder;ng station and the excess solder removal stat;on~ Preferably apparatus 62 is d;sposed prox;mate thè path of~travel of the boards.
3sApparatus 62 of course must be spaced suff;ciently belo~
the path of travel of the boards to perm;t clearance of the Longest depend;ng lead~ etc. Inert gas may be used as the fluid, but prefer3bly the impinging fluid compr;ses air. The fluid should be pre-heated to a temperature above that of the molten solder ;n the soldering station (which for standard 63~37 solder i~
approximately 260C)o and preferably w;ll be pre-heated to a temperature in the range of about 280 C. to 400 C., more preferably about 370 C~ to 10 400 C. (measured at the outlet of apparatus 62). For 63/37 solder alloy, the preferred fluid preheat temperature ;s about 370 C. (measured at the outlet of slot 105, 205)~
The pulsating or sweeping flu;d stream impinging on 15 still molten solder contained on the underside of the circuit board, the interconnections, and the component leads and/or bod;es, relocates excess solder on, and~or blasts excess solder from the underside of the board~
;nterconnections, leads, and bod;es, and ;n do;ng so 20 also minimizes the possib;lity of solder briding or icicl;ng or short format;on upon sol;d;fication.
Referring to F;gures 1 and 3~ in one embodiment of the present invention, the fluid stream~ e.g~ a;r is suppl;ed by flu;d supply means, generally ind;cated by 2s 115, through ducting 116 ;nto one or both ends of inner tubular shell 110 ~hich is non-rotatable. The opposite end of inner tubular shell 110r ;f it ;s not used for supplying 3i r~ is sealed so that the air is only allowed to escape through an open portion or elongate slot 140.
30The open portion 140 is a rectangular portion ~hich has been cut out of the sidewall of the inner tubular shell 110, the length which ;s determined by the ~idth of the mass soldering ronveyor system and the width of which ;s determined by the desired maximum angle of impingement 3sfor the apparatus. Completely enclosing the inner tubular shelL 110 ;s an outer tubular shell 100 ~h;ch rotates about the ;nner shell 110 on bearings means 1Z0 (see Fig. 3)~ The outer tubular shell 100 has lony;tud;nal slots 105a~ br c~.~ wh;ch run lengthw;se 5 perpendicular to the c;r~umference of outer tubular shell 100, the length being substantially equal to the length of open portion 140 and the width be;ng narrow enough to prov;de a suff;c;ent flu;d veloc;ty. The slots 105 are equally spaced apart around the lOcjrcumference of tubuLar shell 100 such that only one slot 105, at any given time, is able to be pos;t;oned over open port;on 140. Seals 103 may be util;zed, depending upon the clearance bet~een the ;nner and ou~er shells, to ensure that the air, from inner tubular shell 15110, is suppl;ed only to the slot 105 pos;t;oned over open port1On 140. It may be desirable, depending on the total area of open portion 140, to prov;de an a;r distribut;on plate 150 to equal;ze the fluid flow being emitted out from open port;on 140 of the ;nner tubular 20shell 110, which teach;ng is well known ;n the air distribut;on art~
The ;nvent;on ~orks as follows~ As outer tubular shell 100 rotates by motor 132 driven dr;ve means, generally ;nd;cated as 135, about the open portion 140 25Of inner tubular shell 110~ air is d;rected through open portion 140~ and d;str;bution plate 150, and forced out through the slot 105a of the outer tubing 100 wh;ch is pos;t;oned over open portion 140~ S;nce outer tu~ular shell 100, along w;th slot 105a, are rotat;ng, the air 30blast forced through slot 105a ;s also g;ven a rotational s~eep;ng movement unt;l the slot 105a rotates past the tra;ling edge ~30 of open portion 1~0 and ;s no longer able to communicate with open portion 140~ At that ti~e, a subsequent slot 105b is then posit;oned 35Over the leading edge 125 of open portion 1~0 and ;
supplied with air to form a subsequent sweeping air blast. As this second slot 105b rotates over open port;on 1~0, the second a;r blast ;s also given a correspond;ng rotat;onal sweeping movement unt;l ;t no longer is positioned over any part of open port;on 1l~0 Th;s procedure is repeated as each subsequent slot 105c... ;s pos;t;oned over the Lead;ng edge 125 of open portion 140.
An alternat;ve embod;ment of the present ;nvent;on lO;S shown ;n F;gures 2 and 4. In the embod;ment shown ;n F;gures 2 and 4, the outer tubular shell 200 is f;xed ;n pos;t;on, and has an open port;on or elongate slot 240 d;rected toward the unders;de of the travel;ng boards 20 wh;le the ;nner tubular shell 210 ;s the rotat;ng member 15wh;ch generates the sweep;ng air blast. As can be seen by compar;ng the two embod;ments as shown, F;gures 3 and 4, open port;on 240 (F;gure 4~ ;s substant;ally wider than open portion 140 (Figure 3). Inner tubular shell 210 is rotatably dr;ven by su;table motor 232 dr;ven 20dr;ve means, generally ;nd;cated as 235~ The a;r ;s suppl;ed by way of flu;d supply meins 115 through ducting 116 and an air tight rotating joint indicated generally at 245 ints one or both end portions of inner rotat;ng shell 210~ The outer tubular sheLl may have 25seals 203 secured to the ins;de of outer tubular shell 200 along the perimeter of open port;on 240. The inner tubular shell 210 has slots 205a, b~ c... wh;ch run lengthwise, perpendicular to the c;rcumference of the inner tubular shell 210~ The slots 205 are spaced 30apart along ;ts circumference such that only one slot 205 is able to communicate with open portion 240, at any given time. Thus, a sweeping air blast controlled by slot 205 is also ob~ained by rotating inner tubing 210 in either the clockwise and counter-clockwise direction.
The angle of ;mp;ngement may be var;ed over a ~;dn range~ preferably between about 30 and about 75, more preferably about 45 to about 65 by suitable selection of slot sizesD The angle of impingement of the air blast relat;ve to the c;rcu;t board should be cont;nuously rapidly varied over the aforesa;d range so that each port;on of the board ;s subjected to an a;r blast over a w;de range of angles. Preferably, the complete cycle of angles ;s repeated every 0.05 to 1.0 lo seconds, more preferably every 0.1 to 0.15 seconds.
Cycle t;me may read;ly be controlled by adjust;ng the rotational speed of the rotat;ng shells.
At leas~ four other poss;ble var;at;ons of the above disclosed embod;ments are foreseen each of which does 15 not depart from the sp;rit and scope of the present invent;on. These embod;ments are shown diagramatically in the draw;ngs, Figures 5 through 8, and are only briefly described below s;nce their detail description is more fully explained above in relation to the two 20other embodiments.
F;gure S discloses a third embodiment ;n which inner tubular shell 510 rotates inside of outer tubular shell S00 similar to the above-disclosed second embod;mentO
The major var;ations in this embod;ment is that inner 25tubular shelL 510 contains a plurality of staggered long;tud;nal slots 505 a, b, c, d ~a (as sho~n ;n Figure 9) instead of long, cont;nuous slots.
A var;ation of the th;rd embod;ment is shown in F;gure 6, wherein inner tubular shell 610 rotates ;nside 30Of a fixed box shell 600, instead of a tubular shelln The box shell 6ûO is completely sealed except for open portion 640 which controls and defines the owtput direction of the s~eeping air blasts.
lo A f;fth embodiment ;s d;sclosed ;n F;gure 7 where;n the outer tubular shell 700 conta;ns a plurality of smaller rectangular openings 74Qa, b, c, ~.., instead of a s;n~le large rectangular open portion. The inner 5 tubular shell 710 rotates inside of the outer tubular shell 7no and contains a plurality of longitudinal slots 705a~ b, c .... The slots 705 are arranged so that only one slot 705 can communicate with the open portion, rectangular open port;ons 740a, b, c~.., at any g;ven time. Therefore, a pulsating air blast is generated as the slots 705 communicate sequentially with the open portions 740.
A final embod;ment is disclosed in figure 8 ~herein an outer tubular shell 800, having a plurality o~ air 15foils 825 situated long;tudinally along the outer tubular shell and compr;sing the side wall of the tubular shell, rotates about a fixed inner tubular shell 810 having an open portion 840, directed toward the underside of a circuit board 20 to be treated. The air ~ foils 825, as they rotate about the slot 840, either deflect or allow the air to pass stra;ght through, thus resulting in a pulsating air blast to the unders;de of the circuit board 20.
Still other changes will be obvious to one sk;lled 25in the art. Accord;ngly, it is intended that all matter conta;ned in the above descript;on or shown in the accompanying drawings shall be interpreted in an illustrative and not ;n a limiting sense.
3a
Claims (14)
1. An apparatus for mass joining with solder electrical and electronic components assembled on a circuit board wherein said components have leads which protrude therefrom, and comprising in combination: a wave soldering station adapted to provide a wave of molten solder; means for transporting said circuit board across said solder whereby a quantity of molten solder may be deposited onto said circuit board underside and said protruding leads; and an excess solder removal station adjacent said wave soldering station, said excess solder removal station adapted to impinge a sweeping fluid blast of continuously varying angle of impingement directed towards the solder wave onto the bottom surface of the board sufficiently soon after it leaves the solder wave so that the solder is still molten, the sweeping fluid blast having sufficient velocity to remove essentially all bridges and shorts but not sufficient velocity to adversely affect properly wetted joints, whereby each portion of the bottom surface of the board may be subjected to a sweeping fluid blast from a plurality of different angles, said excess solder removal station comprising a first fixedly positioned inner tubular shell having at least one inlet and having at least one open portion directed toward the point where said boards exit said wave, and a second rotatably mounted outer tubular shell having a plurality of elongate spaced slots formed therein, means for rotating said outer tubular shell and fluid supply means for connection to said inlet, said outer tubular shell encompassing and rotating about said inner tubular shell such that fluid emanating from said inner tubular shell will be directed by the open portion of the inner tubular shell through the slot of the outer shell to form a sweeping fluid blast.
2. An apparatus of claim 1, wherein said fluid blast is swept through an angle between about 30° and 75°.
3. An apparatus of claim 2, wherein said fluid blast is swept through an angle between about 45° and 65°.
4. An apparatus of claim 2, wherein a complete sweep of angles is repeated every 0.05 to 1.0 seconds.
5. An apparatus of claim 4, wherein a complete sweep of angles is repeated every 0.1 to 0.15 seconds.
6. An apparatus of claim 1, wherein said fluid comprises air, and includes means for heating said air to above the temperature of the molten solder prior to directing the air onto said board.
7. An apparatus according to claim 1, wherein said plurality of elongate spaced slots is substantially equally spaced around the circumference of said outer tubular shell, substantially parallel to the axis of said shell.
8. An apparatus for mass joining with solder electrical and electronic components assembled on a circuit board wherein said components have leads which protrude therefrom, and comprising in combination: a wave soldering station adapted to provide a wave of molten solder; means for transporting said circuit board across said solder whereby a quantity of molten solder may be deposited onto said circuit board underside and said protruding leads; and an excess solder removal station adjacent said have soldering station, said excess solder removal station adapted to impinge a sweeping fluid blast of continuously varying angle of impingement directed towards the solder have onto the bottom surface of the board sufficiently soon after it leaves the solder wave so that the solder is still molten, the sweeping fluid blast having sufficient velocity to remove essentially all bridges and shorts but not sufficient velocity to adversely affect properly wetted joints, whereby each portion of the bottom surface of the board is subjected to a sweeping fluid blast from a plurality of different angles, said excess solder removal station comprising a first fixedly positioned outer shell, having at least one open portion directed toward the point where said boards exit said wave, and a second rotatably mounted inner tubular shell having at least one inlet and having a plurality of elongate spaced slots formed therein, means for rotating said inner tubular shell and fluid supply means for connection to said inlet, said inner tubular shell being encompassed by and rotating inside said outer shell such that fluid emanating from said inner tubular shell will be directed by the slot of the inner tubular shell through the open portion of the outer shell to form a sweeping fluid blast.
9. An apparatus of claim 8, wherein said fluid blast is swept through an angle between about 30° and 75°.
10. An apparatus of claim 9, wherein said fluid blast is swept through an angle between about 45° and 65°.
11. An apparatus of claim 9, wherein a complete sweep of angles is repeated every 0.05 to 1.0 seconds.
12. An apparatus of claim 11, wherein a complete sweep of angles is repeated every 0.1 to 0.15 seconds.
13. An apparatus of claim 9, wherein said fluid comprises air, and includes means for heating said air to above the temperature of the molten solder prior to directing the air onto said board.
14. An apparatus according to claim 9, wherein said plurality of elongate spaced slots are substantially equally spaced around the circumference of said inner tubular shell, substantially parallel to the axis of said shell.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000521540A CA1249069A (en) | 1986-10-28 | 1986-10-28 | Mass solderng system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000521540A CA1249069A (en) | 1986-10-28 | 1986-10-28 | Mass solderng system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1249069A true CA1249069A (en) | 1989-01-17 |
Family
ID=4134226
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000521540A Expired CA1249069A (en) | 1986-10-28 | 1986-10-28 | Mass solderng system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1249069A (en) |
-
1986
- 1986-10-28 CA CA000521540A patent/CA1249069A/en not_active Expired
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