Manually Operated Soldering Apparatus

The present invention relates to a manually operated soldering apparatus. In particular, it relates to a selective soldering apparatus in which components can be selectively soldered to a printed circuit board (PCB).

Selective soldering apparatus is well known in the art and described for example in US-A-4651916, the contents of which are incorporated herein by reference. We have developed systems in which a solder bath is raised towards the underside of the PCB in order to dip the leads into the solder exiting from the solder nozzle. One example is described in WO2005/115889 the contents of which are incorporated herein by reference. Thus the board can be kept in a stationary plane. In our prior art apparatus, the apparatus is programmed to move the board and bath relative to one another to dip the leads to be soldered. An array of nozzles on a single plate may be used, as described in WO2005/115671 (the contents of which are incorporated herein by reference) for example, to perform soldering of all components in a single operation, or a board may be moved relative to a single nozzle to solder individual components as in WO2005/115889. hi these apparatus, a program must be developed for each type of board to be soldered, and in some cases individual thimble plates or nozzle assemblies developed for each board as well. This is time consuming and expensive and so such apparatus are not suited to low volume manufacture or low volume manufacturing runs.

In a first aspect of our invention we provide a manually movable frame which carries a PCB to be soldered. The frame is guided on rails to move in a single plane, in the X-Y directions. The board is moved, by the operator moving the frame, to position a lead or leads to be soldered over a solder nozzle. Operator controlled controls are used to effect vertical movement of the solder nozzle, or the complete bath, to dip the lead (s) into solder in the nozzle and effect the soldering operation. A fluxer may be provided, the

lead(s) to be soldered being positioned over the fluxer prior to soldering and flux being sprayed onto the leads and associated PCB track prior to soldering.

In one method of operation forming another aspect of this invention, the operator sequentially moves the board to position the lead(s) over the fluxer, a foot pedal or switch is operated to actuate the fluxer to spray flux onto the lead(s). The board is then moved to position the leads over the solder nozzle. A second foot pedal is operated to raise the nozzle or bath to dip the leads. It will be appreciate that manual switches could also be used, but we prefer to used foot pedals or foot operated switches to leave the operator in full manual control of the movable frame.

The interface between the foot pedals and fluxer and solder bath is preferably electronic. Thus, the solder bath may be controlled in various ways. Operation of the second foot pedal may cause the nozzle or bath to raise to dip the lead for a preset time, say 2 seconds, before lowering the nozzle or bath. A third pedal may be provided to raise the solder nozzle or bath to dip a lead, and then hold the nozzle in position while the board is drawn across the solder nozzle to solder a line of leads, of an electrical connector for example. In another embodiment, operation of a foot pedal causes the nozzle or bath to be raised to dip the lead(s) and the solder level in the nozzle is lowered (by reducing the solder pump speed, for example) before lowering the nozzle or bath itself. This technique is useful for drawing solder away from leads to prevent bridging. In another form the operator may be able to dip the lead or track to be soldered for a longer period of time to ensure feed through of solder when soldering a through hole on the board.

To align the PCB over the nozzle of the solder bath a light beam, such as a laser, may be aligned with the position of the solder nozzle when it is raised. Thus the board is moved, by moving the frame, to position the lead in the beam. The board is then held stationary by the operator and the soldering operation performed.

A second beam may be provided for aligning the board over the fluxer. Different coloured light beams can be used to facilitate distinguishing between the fluxer position and the solder nozzle position.

Often the position of a lead to be soldered is obscured by components on the other, upper side of the board. Thus in another aspect of our invention we provide a second frame on the movable frame for holding a second PCB parallel to and in register above the PCB being soldered. The second PCB corresponds to the first PCB and the location of leads or tracks to be soldered can be marked on the second PCB. However, no components are mounted on the second PCB. Thus, the operator can manoeuvre the frame so that the position, on the second board, of the lead or track to be soldered, is in the line of the beam. This will mean that the lead on the underneath board is in line with the solder nozzle. It will be appreciated that the second PCB could be replaced with some other template, but it is simplest to use a PCB corresponding to the one being soldered. The second PCB is preferably carried on a hinged frame for pivoting it vertically to allow replacement of the board being soldered.

Preferably, datum points on the frame and on the hinged frame carrying the second PCB are provided and the PCBs aligned against those. A PCB to be soldered may mounted in the movable frame and a datum point on the PCB positioned in the line of the light beam. The second 'dummy' board is then positioned in the second frame above the first PCB and its position adjusted until a datum point on the second board is in line with the beam. In this way any misalignment of the first and second boards can be compensated for, or if the light beam is not vertical, for example.

We have found that another difficulty with manual control of the frame and board movement is the accuracy of movement away from the stationary position. Typically an operator needs to position the PCB to within about 0.5mm of the required location and to track under the light beam to this accuracy as well as a desired speed when soldering a line of leads. When moving from the stationary position there is greater friction or resistance to movement than when the frame is actually moving. Thus, when the board is positioned to solder a line of leads, the operator positions the first lead over the nozzle, raises the nozzle and moves the board to track the line of leads over the nozzle. However, the initial greater resistance to movement can result in the board moving too quickly over the nozzle in the first instance. In yet another aspect of the invention, we overcome this problem by providing a resilient friction member between the frame and the supporting structure. The friction member is fixed to one of the frame

and the supporting structure. As the frame is first moved, the resilient friction member is firstly deformed and then the frame, or the supporting structure, slides over the friction member. We have found that this allows the operator to exert a more constant speed of movement at the start of moving. Means may be provided for adjusting the pressure exerted by the friction member on the relatively moving frame or support structure. A friction member in the form of rubber or an elastomeric material is preferred. A closed cell foam may be used.

In yet another aspect of the invention, the movable frame is mounted to pivot about a horizontal axis. This allows the frame to be pivoted away from above the solder bath to allow maintenance of the bath. Preferably the frame pivots about an axis towards the rear of the machine relative to the operator. A supporting structure may include a rail which is removable to allow easier access to the solder bath and its removal. Preferably a front rail is removable.

In yet another aspect of the invention, by providing for the frame to be pivotable, we can arrange for the frame to be moved in a plane which is at an angle to the horizontal. Thus, the frame may be moved in a plane at a few degrees to the horizontal and the solder bath or nozzle can be replaced with a wave soldering machine. Thus the manually operated apparatus can be used for wave soldering, providing greater versatility.

In alternative form the movable frame may be mounted on electrically driven lead screws and may be moved by the operator controlling a joystick. In yet another form, the apparatus may include a programmable control for programmed movement of the frame and operation of the fluxing and soldering machines.

The manually operated apparatus of the invention is also useful for re-working boards which have been previously soldered, particularly for replacing a faulty component. A nozzle which matches the component lead arrangement is mounted in the apparatus. The board can be positioned over the nozzle and the nozzle or bath raised to reheat a soldered joint, solder can then be blown or sucked from the reheated joint.

The invention will be further described by way of example with reference to the accompanying drawings in which:

Figure 1 is a perspective view of an apparatus forming an embodiment of the invention;

Figure 2 shows the apparatus of Figure 1 in another configuration;

Figure 3 shows the apparatus of Figure 1 in yet another configuration;

Figure 4 illustrates schematically aspects of the embodiment of Figure 1, and

Figure 5 shows a friction member of the embodiment of Figure 1.

In Figure 1, a movable frame 10 comprises front and rear rails 12, 14 and side rails 16, 18. A .handle 20 for gripping by an operator to move the frame 10 is mounted on front rail 12. Within frame 10 are board support rails 22, 24, 26, 28 for supporting a PCB 30 which is to be soldered. Clips 32 hold the PCB against the rails 22, 24, 26, 28. Rail 24 is movable backwards and forwards within frame 10 to accommodate different sizes of board. Rail 24 carries a second frame 34 which carries a second or reference PCB 36. Frame 34 is hingedly mounted on rail 24 to move between a vertical position, shown in Figure 1, and a horizontal position above and parallel to board 30 (see Figure 4).

Shafts 38, 40 are mounted on side rails 16, 18. Shafts 38, 40 slide linearly in four bearings 42 (two can be seen in Figure 1) mounted on a sub-frame 44. Thus, frame 10 can be slid back and forth by an operator, shafts 38, 40 sliding in bearings 42.

At the rear, sub-frame 44 carries two bearings 46 which slide on a rear shaft 48. At the front, sub-frame 44 has front rail 44a which clips onto a bearing member slidingly mounted on a lateral forward shaft 50. Shafts 48, 50 are mounted on a stationary support framework. 52.

Thus, to move frame 10 and hence board 30 laterally, the operator slides frame 10 sideways, this carrying sub-frame 44 which slides on rails or shafts 48, 50. Hence

movable frame 10 is movable in the X-Y directions in a plane which, in use, is horizontal in Figure 1.

Below the level of frame 10 is a cabinet 60 which house a solder bath including a pump and nozzle as well known in the art and an electrically operated lifting mechanism which is controlled by one of two foot pedals 62, 64. A fluxing apparatus is also housed in the cabinet 60 and controlled by foot pedal 66 (see Figure 4).

Mounted above the movable frame 10 on an arm 70 cantilevered from framework 52 are two lasers 72, 74. Lasers 72, 74 are oriented to project a laser beam downwards on to the nozzle of the solder bath and the fluxer respectively (see Figure 4).

Referring to Figure 2, this shows the apparatus configured for maintenance of the solder bath or fluxer. The sub-frame 44 has been undipped from the front shaft 50. Thus, sub-frame 44 can be pivoted back, around shaft 48, carrying frame 10 with it. A handle 80 on sub-frame 44 provides for safety control. A front rail 82 carrying shaft 50 is removed, allowing an operator full access to cabinet 60 and the solder bath and fluxer housed within.

In figure 3, the rail 82 has been replaced, but in a higher position than in Figure 1. Thus, sub-frame 44 is sloped at an angle of about 7 degrees to the horizontal. Hence frame 10 will be slid back and forth in a plane at this angle. The angle is chosen to suit a wave soldering operation. Wave soldering is well known in the art. To perform wave soldering, a board is drawn across a wave of solder, along a plane angled to the horizontal, typically at 5 to 10 degrees to the horizontal. The solder bath in cabinet 60 can be replaced by a suitable wave soldering apparatus, or the solder bath fitted with an appropriate nozzle to effect wave soldering.

Figure 4 shows schematically the operation of the soldering apparatus. The board 30 to be soldered is held in movable frame 10. Reference board 36 is positioned above board 30 and in register with it. Board 30 carries components to be soldered to it. Board 36 has the same track pattern as board 30, but carries no components.

Lasers 72, 74 emit collimated beams 72a, 74a vertically downwards on to board 36. Prior to positioning boards 30, 36, lasers 72, 74 are aligned so the beam 72a will intercept or shine on to the tip 90' of the nozzle 92 of solder bath 94 when the bath 94 is in the raised position, shown in doted outline in Figure 4. Thus, with boards 36, 30 in place, when the beam 72a shines on to a track portion or lead hole in board 36, the board 30 will be positioned with the same lead hole (and its associated component lead) over the position of the nozzle outlet 90', when bath 94 is raised.

Similarly, beam 74a is aligned with the outlet 96 of fluxer 98. Fluxer 98 issues a spray and so alignment with the fluxer is less critical.

It can be seen that foot pedals 62, 64, 66 are connected to a processor 100 which will control the fluxer 98 and solder bath 94 in response to operation of the pedals 62, 64, 66.

The operation of bath 94 and pumping solder through nozzle 92 and outlet 90' to achieve a soldering operation is well known in the art and need not be described here. Reference can be made to the aforementioned specifications and the apparatus and methods described therein.

Referring to Figure 5, this shows a friction member 100 which is mounted between a rail 40 and sub-frame 44. Friction member 100 comprises an elastomeric pad 102 of closed cell foam mounted in a cylinder 104 held in sub-frame 44. Pad 102 presses on rail 40 and so provides resistance to the movement of the rail relative to the sub-frame 44. As frame 10 is slid backwards or forwards, i.e. moving relative to the sub-frame 42, the elastomeric pad 102 initially deforms and then the rail 40 slides across the pad 102. We have found that this enables an operator to move the frame more smoothly from a stationary position.

Pad 102 is mounted on a screw 106 in cylinder 104 to allow adjustment of the pressure of the pad on the rail 40.

A friction member may be provided on the other rail 38 as well and to achieve a similar effect for lateral movement, a friction member is mounted on frame 44 and bears against rail 48.

As noted above, datum points may be provided on frame 10 and hinged frame 34 to align the boards, for example a corner point. However the laser beams may also be used to align the boards. Board 30 is positioned first with the laser beam on a datum point on the board and then board 36 positioned, and then board 36 positioned.

Shafts 18 and rail 48 may be replaced by, or coupled to, electrically driven threaded shafts 18', 48'and ballscrews (or leadscrew arrangements), bearing 42', 46' being configured as ballscrews to engage with the driven shafts 18', 48'. Bearing 42' is fixed to sub frame 44 and bearing 46' is fixed to frame 52. The shafts 18', 48' can then be rotated electrically under the manual control of a joystick 112 controlled by the operator. This is illustrated schematically in Figure 6. By using stepper motors 108, 110 to rotate the shafts 18', 48' it is possible to provide a learning mode for the apparatus. The operator operates a switch, not shown, to instruct processor 100 to learn the sequence of operations. The operator then operates the soldering apparatus manually, moving the board 30 by means of joystick 112 to operate motors 108, 110 via processor 100. As the board 30 is positioned, pedals 62, 64, 66 are operated as necessary to flux and solder the board 30. The sequence of operations is stored in processor 100. (The steps of the stepper motors 108, 110 between each fluxing and soldering operation being counted). A new board is then positioned in place of board 30, and aligned using datum points on the board and frame 10, and processor 100 then repeat the sequence of board movements and soldering operations by issuing control instructions to the motors 108, 110 and to the fiuxer and solder bath (Figure 6).