AUTOMATIC SOLDERING DEVICE

Abstract: A method and device for automatic soldering of multiple intermittently arranged terminals; an automatic soldering method and device which prevents a bridging phenomenon occurring between the soldered terminals by sliding, virtually horizontally, the iron tip (27) of the soldering iron (25) which is held on the arrayed terminals after the application of the solder to those terminals, at right angles to the direction of the arrayed terminals, thus separating it from the arrayed terminals.

Description: Background of the Invention The present invention relates to an automatic soldering method and an automatic soldering device for arrayed terminals, in particular to an automatic soldering method and device ideal for soldering arrayed terminals on flat-pack ICs. Disclosure of Prior Art Recently, increasing use is being made of flat-pack ICs in which pins (terminals) are soldered on to the surface of a base plate, instead of being passed through holes drilled in the base plate to the underside and soldered to the underside of the plate as with conventional ICs in the past. Because there is no need to drill holes in the base plate of the IC, pins can be arrayed as multiple terminals at intermittent microscopic intervals, thus permitting the design of a smaller IC with a higher performance. Problems Solved by this Invention However, because the distance between the pins arrayed intermittently in these flat-pack ICs was microscopic, it was easy for "bridging" to occur during soldering, forming a bridge of solder between each pin. This made it difficult to automate the soldering process. Summary of the Invention This invention distinguishes itself from previous art by the provision of an automatic soldering method and device thereof which automatically solders arrayed terminals in a way that does not cause bridging. More specifically, this invention is designed to prevent the soldering together of terminals by releasing the iron tip of the soldering iron from the arrayed terminals after solder has been applied to the multiple intermittently arrayed terminals, by horizontally sliding the iron tip at right angles to the direction of the arrayed terminals. The other purposes, features and advantages of this invention will be clarified in the following description which refers to the attached drawings. Brief Description of the Drawings Fig. 1 shows a schematic plan view of a device which incorporates an automatic soldering device according to the first embodiment of the present invention. Fig. 2 is a side view of the device viewed from the direction of the arrow II in Fig. 1. Fig. 3 is a plan view of the positioning stage. Fig. 4 is a side view of the positioning pin mechanism. Fig. 5 is an overall side view showing the automatic soldering device with the extension frames closed. Fig. 6 is an overall side view of the automatic soldering device with the extension frames open. Fig. 7 is a side view viewed from the direction of the arrow VII in Fig. 5 (Note that the solder supply mechanism has been omitted). Fig. 8 is an enlarged view of the iron tip applying solder. Fig. 9 shows the tracks of the iron tip. Fig. 10 is an overall oblique view of the second embodiment of this invention, corresponding to Fig. 5. Fig. 11 is a side view of the entire automatic soldering device in Fig. 10, with its extension frames open. Fig. 12 is a side view viewed from the direction of the arrow X II in Fig.10 (with the solder supply mechanism omitted). Fig. 13 is an enlarged view of the iron tip in another embodiment of the invention. Fig. 14 is a cross-section view running in the direction X IV - X IV in Fig. 13. Fig. 15 is a plan view of the FPC and PCB in a third embodiment of the invention. Fig. 16 shows the FPC and PCB of Fig. 15 during soldering. Fig. 17 is a plan view of a flat-pack IC ; and Fig. 18 is a side view of the flat-pack IC shown in Fig. 17. Preferred Embodiment of the Invention The present invention will now be described with reference to the attached drawings. In the description which follows, the expressions indicating the direction of movement of the iron tip - "the direction at right angles to the arrayed terminals", and "direction of release from the flat pack IC" - are in practice the same direction. For the purposes of the description, the latter term will be used when the object being soldered is the flat pack IC, while the former will be used when the flat pack is not specified as the object of soldering. First Embodiment of the Invention The first embodiment of the current invention will be described on the basis of Figures 1 to 9 and Figures 17 and 18. First, the overall device incorporating the automatic soldering device for arrayed terminals of this invention will be described with reference to Figures 1 to 4. 5 is the flat pack IC automatic soldering device - "arrayed terminals automatic soldering device"- of this invention, mounted in an optional position on the head 7 of a freely moving and freely rotating robot arm 6. A detailed description of this automatic soldering device 5 will now be given. Base plate 2, with only the insulated parts on both sides on the belt, is being continuously conveyed by a free flow conveyor 8 which has two belts. 9 is a tray containing many flat pack ICs 1, both on upper and lower levels. The flat pack ICs 1 contained in the tray 9 are transported by the vacuum conveyor mechanism 10 (Fig. 7) of the automatic soldering device to the positioning stage 11. On this positioning stage 11, the flat pack ICs 1 conveyed by the tray 9 are pushed horizontally and from two intersecting directions, into the corner 13 by the pushing means 12, so that a flat pack IC 1 can be extracted from a precise position by the automatic soldering device. As indicated in Figure 3, the positioning stage 11 has two stages, right and left, to enable two flat pack ICs 1 of differing shapes and sizes to be positioned. In use, either one of the stages is used. For demonstration purposes, Figure 3 shows the right and left stages with flat pack ICs 1 of differing shapes and sizes. The flat pack IC 1 positioned on the positioning stage 11 is again lifted up by the vacuum conveyer mechanism 10 of the automatic soldering device 5, and are carried to a specified position on the base plate 2 which has been stopped by stopper 14 of the free flow conveyor 8. Base plate 2 stopped by stopper 14 is slightly raised by lifting means 8a to avoid friction with the belt. The stationary position of base plate 2 is made even firmer by the insertion of positioning pin 17 of the positioning pin mechanism 16 provided on the side of the free flow conveyor 8, in the small hole 15 on the side of the stationary base plate 2. Then, the flat pack IC 1 placed on the stationary base plate 2 is soldered to the printed circuit board wiring printed on the base plate 2, using the automatic soldering device 5. The above describes the overall construction of a device incorporating the automatic soldering device 5 of this invention. Figures 5 through 9 provide more details of the flat pack IC automatic soldering device. This automatic soldering device 5 is mounted on head 7 of robot arm 6, as described above, and the entire device can be moved in the four axial directions (X,Y,Z and ⊖ : forwards/backwards (the X arrow direction of Fig. 1), right/left (the Y arrow direction in Fig. 1), up/down (the X arrow direction indicated in Fig. 7) and rotationally (direction O indicated in Fig. 7). A support plate 18 is fixed to the head 7 of the robot arm 6 (Fig. 7), and on the support plate 18 are mounted a pair of extension frames with a solder supply mechanism 19, and a vacuum conveyor mechanism 10. The extension frames 20 are hinged onto the upper surface of support plates 18 by rotating hinges 21, and they swivel open and closed. The opening and closing is performed by the extension cam 22 provided on the support plate 18 rotating through the driving force of the motor 44 and pressing on the cam followers 23 attached to both extension frames 20 which are given additional power in their approach to each other. At the end of each extension frame 20 there is a soldering iron 25. This soldering iron 25 is supplied with additional power always in the downward direction by a spring which is not shown on the drawing. Further, the iron tip 27 of this soldering iron 25 is flattened at the end, its width having a length L (Fig. 17) which is appropriate to the side 28 of the flat pack IC 1 along which are arrayed multiply and intermittently pins 3 as terminals. The width of the iron tip 27 is set in accordance with the length L of the side 28 of the flat pack IC 1 to be soldered. When the flat pack IC 1 is rectangular, the solder tip is adjusted to the length of the longer side 28. Also the said extension frames 20 are provided with a solder supply mechanism 19 consisting of a rotational arm 29 and a horizontal slide arm 30. A rotational arm 29 is attached to the extension frame 20 at the rotational fulcrum 31. Each rotational arm 29 is also provided with a cam follower 34 corresponding to the sloping part 33 of the extension frame 20. By moving the whole rotational arm 29 upward using the air cylinder 24, this cam follower 34 is pushed by the sloping part 33, and they rotate apart. This rotational arm 29 also has a horizontal slide arm 30 retained by a slide ball guide 35. This horizontal slide arm 30 is slided horizontally as a result of rotational torque from the pulse motor 36 provided on the side of the rotational arm 29 transmitted to the rack 37 and the pinion 38. At the end of this horizontal slide arm 30, the thread solder supply nozzle 39 for the provision of thread solder 47, and the end of the flux supply nozzle 40 for the supply of flux are held together (Figure 8). The thread solder supply nozzle 39 is connected to the thread solder feed unit 45 for the supply of thread solder 47. The flux supply nozzle 40 is connected to the flux supply dispenser 46. Therefore the adjoining parts of these thread solder supply nozzle 39 and the flux supply nozzle 40 slide horizontally forwards and backwards in the direction of the arrow X along the iron tip 27 of the soldering iron 25, permitting the supply of thread solder 47 and flux 26 one after another. The vacuum conveyer mechanism 10 is mounted on the said support plate 18 and is also connected to a vacuum suction device not shown in the drawing. The vacuum heads 41 of this vacuum conveyor mechanism 10 can be moved up and down and swiveled in and out in relation to soldering iron 25 using the two cylinders 42 and 43. The process of soldering using the automatic soldering device 5 constructed as described above will now be explained. First the head 7 is moved by the robot arm 6, the vacuum conveyor mechanism 10 of each retaining plate 18 is operated and the vacuum head 41 is positioned above the tray 9. Then using the cylinder 42 the vacuum head 41 is dropped and an optional flat pack IC 1 is extracted from the tray 9 using vacuum suction and moved to the positioning stage 11. The flat pack IC 1 moved to the positioning stage 11 is inserted in either of the stages shown on Fig. 3 and is pushed from two directions into corner 13 by the pushing means 12, positioned in an accurate "base position". This base position is used by the automatic soldering device 5 as the "starting position" for moving a flat pack IC 1 to a specified position on the base plate 2 which has already been stopped by the free flow conveyor 8. Next the automatic soldering device 5 which has been moved by the robot arm 6 above the positioning stage 11 begins automatic soldering processing. First, the vacuum head 41 of the vacuum conveyor mechanism 10 is drop ped to the base position (starting position) described above and extracts a flat pack IC 1 from the positioning stage 11 using vacuum suction. The entire automatic soldering device 5 is then moved above the specified soldering position on the base plate 2 which has been previously stopped on top of the free flow conveyor 8. The movement of the automatic soldering device 5 itself is completely computer controlled and at the point where it is positioned over the base plate, the iron tip 27 of the soldering iron 25 is already accurately positioned for soldering the base plate 2. Secondly, with the flat pack IC 1 still attached by suction to the vacuum head 41, it is moved by cylinder 43 in the direction of the arrow X from the back to the front (from right to left in Fig. 7) into position between the soldering irons 25. Then, the vacuum conveyor mechanism 10 descends using cylinder 42 and places the flat pack IC 1 onto the specified position of the base plate 2, where it stays positioned. Thirdly, the soldering iron 25 and the solder supply mechanism 19 descend by the descension of the automatic soldering device 5 itself, and the solder tip 27 of the soldering iron 25 is pushed against the first two sides, either of two opposing sides of square flat pack IC 1 i.e.28a, 28a, or 28b, 28b. The thread solder supply nozzle 39 and the flux supply nozzle 40 held at the end of the horizontal slide arm 30 of the solder supply mechanism 19 are positioned at one end of each of the iron tips 27 (front end 27a in Fig. 8). Thread solder 47 and flux 26 are then supplied from the ends of the thread solder supply nozzle 39 and the flux supply nozzle 40 respectively. Then, with the thread solder 47 and the flux 26 supplied from the thread solder supply nozzle 39 and the flux supply nozzle 40 to the solder tip 27 converging, it is slid horizontally backwards, (right in Fig. 8) along the iron tip 27 and moved up to the other end of the iron tip 27 (back side 27b in Fig. 8). The thread solder 47 and the flux 26 are thereby continuously and evenly applied to opposite sides 28a, 28b of the flat pack IC 1. Then, at the fourth stage, when the horizontal slide arm 30 has been slid horizontally from one end of the iron tip 27 to the other end, the extension cam 22 positioned in the center of the support plate 18 rotates, pressure is applied to the cam follower 23 of the extension frame 20, and the upper rotational hinged part 21 opens in the middle towards the direction separating the extension frames 20. Because the iron tip 27 is far enough away from the rotational hinged part 21, the iron tip 27 slides almost horizontally in relation to the flat pack IC 1. In other words because of the large distance from the rotational hinged part 21 to the iron tip 27, the tracks of the movement of iron tip 27 describe a large arc, and the tracks of the movement of iron tip 27 above the terminals (in practice pins 3) are almost horizontal. The entire automatic soldering device 5 is lifted up by the robot arm 6. The tracks of the iron tip 27 at that time are shown in Fig. 9. By making a horizontal slide track S in the direction away from the flat pack IC 1, the iron tip 27 applies an appropriate amount of thread solder 47 on pin 2 of flat pack IC 1 and the so-called "bridging phenomenon" wherein the melted solder 47 on each pin 3 joins together is prevented because the excess solder is carried away on the iron tip 27 and the thread solder 47 melted on the iron tip 27 does not spread very much because of surface tension. At this point the first two sides eg.28a, 28a of the flat pack IC 1 have been soldered. In the following fifth stage, the vacuum conveyer mechanism 10 releases its vacuum and draws upwards and the vacuum head 41 between the two soldering irons 25 is withdrawn and moves backward. In the sixth stage, the automatic soldering device 5 which has completed soldering the opposite sides 28a, 28a, and has been lifted up is carried to a cleaning de vice not shown in the drawing, where pressurized air is blown onto the soldering iron 25 in its open position, removing any traces of solder attached to the iron tip 27. During cleaning, the solder supply mechanism 19 is kept in position separated from the extension frame 20, so as not to hinder the cleaning of the soldering iron 25 which is mounted on the end of the extension frame 20. This open position in which the solder supply mechanism 19 is separated from the extension frame 20 is also convenient when replacing the soldering irons 25, and prevents the heating and melting of the thread solder 47 in the solder supply mechanism 19 by soldering ron 25 during non-soldering work. When cleaning is completed, in the seventh step, the automatic soldering device 5 is returned to its position above the base plate 2 and is lowered after rotating 90 degrees, and the remaining two sides 28b,28b of the flat pack IC 1 are soldered in the same manner as described above. Second Embodiment The second example of an embodiment of this invention will be described with reference to Figures 10 to 14. Description of those parts which are common to both inventions will be omitted from the description. First, in this embodiment, the iron tip 49 of the soldering iron 48 differs from the soldering iron 27 in the previous example in that it is narrower than the length of the side 51 of the flat pack IC 50. A cross section of the iron tip 49 shows, as in Fig. 14, that one side of it consists of an inclined part 52. Also the arm 54 of the solder supply mechanism 53 is joined to the rotational arm 55, and does not slide horizontally forwards and backwards (in the direction of arrows X) in relation to the soldering iron 48. In terms of the mounting of the head 57 on the robot arm 56, the mounting plate 59 which supports the vacuum conveyer mechanism 58 is attached to head 57. Therefore, the vacuum conveyer mechanism 58 is fixed in relation to the head 57. Also the upper part of support plate 61 which supports the self-rotating extension frame 60 is provided with a forwards and backwards rotating feed screw 63 in the pulse motor 62. This feed screw 63 screws into the upper part of the mounting plate 59 for the said vacuum conveyer unit 58, and through the pulse motor 62 rotating this feed screw 63 backwards and forwards, the whole support plate 61 can be made to move horizontally forwards and backwards (in the direction of the arrow X). In other words, the soldering iron 48 is slidable in relation to the vacuum conveyer unit 58, and slides only by an amount of strokes St corresponding to the length of the side 51 of the flat pack IC 50. The mounting plate 59 also has a opening 65 to prevent it interfering with the motor 64 which is provided on the support plate. Next the operation will be described. Up to the point where the flat pack IC 50 is placed in a specified position on the base plate 66 by the vacuum conveyer mechanism 58, operation is the same as described for the previous embodiment. Then the iron tip 49 of the soldering iron 48 is pushed into position at the first (front) terminal pin 67a on the first two opposite sides of flat pack IC 50, and at the same time, the solder supply nozzle 63 and the flux supply nozzle 69 are positioned relative to each other. Then while supplying thread solder 70 and flux 32 to the iron tip 49 from the thread solder supply nozzle 68 and the flux supply nozzle 69, the iron tip 48 is moved towards pin 67b on the other (back) terminal side by the rotation of the said feed screw 63. As shown, the thread solder 70 is applied from the outside of the soldering iron 48, but the melted thread solder 70 is also circulating in the other side of the soldering iron 48, and each of the pins 67 are accurately soldered in succession by the movement of the soldering iron 48. When the soldering iron 48 is moving, it forms a sloping part 52 as previously described at one en d of the iron tip 49 , and at the other end, in the direction of movement of the iron tip 49, thus effectively preventing bridging as described. The reason for the construction of the iron tip 49 in a deformed sloping part 52 as shown in the cross section is so that when moving the iron tip 49 over the area to be soldered, pins 67 while continuing to supply thread solder 70 and flux 78, and then soldering them, only the necessary amount, and no more, of solder is applied, and bridging does not occur. The reason for, and mechanism by which, bridging is prevented when the iron tip 49 is shaped as the inclined part 52 is not entirely clear. However the inventor has proved through various experiments that while slight variations in the prevention of bridging occur with different shapes of the inclined part 52, an inclined part 52 shaped as shown in Fig. 14 is most effective for preventing occurrence of bridging. Then, once the iron tip 49 reaches the last pin 67b, the extension frame 60 opens as in the previous embodiment and the iron tip 49 of the soldering iron 48 is made to slide almost horizontally in a direction away from the flat pack IC 50. This is designed to prevent bridging in the vicinity of the pins 67b on the far terminal side. Remaining operations are the same as in the previous embodiment. In the above description, a slide mechanism with a feed screw 63 was employed to move the soldering iron 48 horizontally. However, the same device can be employed to move the soldering iron 48 horizontally, by moving the whole robot arm device 56 horizontally. In this case however, the flat pack IC 50 must be already attached to the base plate 66. Third Embodiment Figures 15 and 16 depict a third embodiment of this invention. In this embodiment, the device for soldering does not employ extension frames 20, 60 as in both embodiments 1 and 2. Instead it suffices to have "a single soldering iron" 75 which can supply thread solder 77 and flux 78, and which can move horizontally by means of a robot arm. Also in this embodiment, a soldering iron 75 with a broad iron tip 27 is used, as shown in Fig. 8, but of course, a soldering iron with a narrow iron tip 49 as shown in Fig. 13 can also be used. In this embodiment example, we will describe a case involving soldering of the copper terminals 72 of an FPC (flexible printed circuit) 71 to the copper wiring terminals 74 of a PCB (printed circuit board) 73. First, each of the terminals 72 of the FPC 71 are overlaid on the wiring terminals 74 of the PCB 73. Then the iron tip 76 of the soldering iron 75 is pushed against the overlaid part as shown in Fig. 8. Then thread solder 77 and flux 78 are supplied to the iron tip76. Once thread solder 77 has been supplied, the robot arm slides the soldering iron 75 horizontally at right angles to the arrayed terminals 72 and wiring terminals 74 (left to right in Fig. 15). In this way, the terminals 72 of FPC 71 are accurately soldered to the wiring terminals 74 of PCB 73, without a "bridge" forming. As described above, the method of soldering arrayed terminals in the present invention is effective in permitting accurate soldering of terminals without creating a bridge between them, because the iron tip of the soldering iron is made to slide horizontally at right angles to the arrayed direction of the terminals. Further, the automatic soldering device for arrayed terminals of the present invention automatically performs soldering through its extension frames, soldering iron and soldering mechanism. It is effective in markedly improving the efficiency of soldering compared with the manual methods previously used, and also guaranteeing consistent quality in the result.

Claims: 1. A method of soldering arrayed terminals characterized by the pushing of the iron tip of a soldering iron against multiple terminals which are arrayed intermittently, suppl ying solder to the solder tip and then, after soldering, the almost horizontal sliding of the iron tip at right angles to the direction of the arrayed terminals, before release of the soldering iron. 2. The row terminal soldering method as claimed in Claim 1 characterized by the iron tip of the soldering iron being pushed against the arrayed terminals furnished plurally and intermittently along the side of a flat pack IC positioned on a base plate, and then solder being supplied to the iron tip, and then after soldering, sliding the iron tip almost horizontally in the direction away from the flat pack IC, before releasing the soldering iron. 3. The row terminal soldering method as claimed in Claim 2 characterized when the iron tip is flat and at least broader than the length of the side of the flat pack IC, by the pushing of the said iron tip against the arrayed terminals, and applying solder to the iron tip and then soldering, before sliding the iron tip almost horizontally in the direction away from the flat pack IC. 4. The row terminal soldering method as claimed in Claim 2 characterized when the iron tip is narrower than the length of the side of the flat pack IC, by the pushing of said iron tip against the terminals at one end of the side of the flat pack IC, and while continuing to supply solder to the iron tip, moving the relevant iron tip towards the terminals on the other end of the side. 5. An automatic soldering device for arrayed terminals characterized by being fitted with a pair of extension frames which swivel together and apart mutually, and which are mounted on a support plate fixed in an optional position to the head of a freely moving and freely rotating robot arm, and soldering irons which are mounted respectively on the end of the said extension frames, and a solder supply mechanism which freely supplies thread solder to the iron tip of the soldering iron. 6. The automatic soldering device for arrayed terminals as claimed in Claim 5 characterized by being fitted with a pair of extension frames which mutually approach and separate and which are mounted on a support plate which is fixed to the head of a freely moving and freely rotating robot arm, and soldering irons which are mounted on the ends of said extension frames, and a solder supply mechanism which is designed to approach and retreate in relation to these extension frames, and which freely supplies thread solder to the iron tip of the soldering iron, and a vacuum conveyer mechanism which is mounted on the said retaining plate and which extracts the flat pack IC using vacuum suction and conveys and positions it. 7. The automatic soldering device for arrayed terminas as claimed in Claim 6 characterized when the iron tip is flat and at least broader than the length of the side of the flat pack IC, by the solder supply mechanism sliding horizontally freely in relation to the soldering iron, while supplying thread solder to the iron tip of the soldering iron which is pushed against the arrayed terminals of the flat pack IC. 8. The automatic soldering device for arrayed terminals as claimed in Claim 6 characterized when the iron tip is narrower than the length of the side of the flat pack IC, by the free movement of the iron tip of the soldering iron from the terminals at one end of the side of the flat pack IC towards the terminals at the other end, and also by the free supply of solder to the iron tip in conjunction with that movement. 9. The automatic soldering device for arrayed terminals as claimed in Claim 8 in which the soldering iron is fitted, at one end of the iron tip, and at the far end of the direction of movement of the iron tip, with an iron tip which in cross section forms a deformed inclined part.

Inventors: KAWAGUCHI, SEIJI
Applicants: APOLLO SEIKO LTD.
Application year: 1987
Main classification: B23K1
IPC codes: H05K13, H05K3