GB2063135A

GB2063135A - Soldering and desoldering apparatus

Info

Publication number: GB2063135A
Application number: GB8032785A
Authority: GB
Original assignee: Blacklock J W
Current assignee: Blacklock J W
Priority date: 1979-11-05
Filing date: 1980-10-10
Publication date: 1981-06-03
Also published as: GB2063135B

Abstract

An apparatus for inserting or removing a multi-pin solid state electronic device in or from a printed circuit board comprises a soldering head 2 disposed, in use, beneath the board and an insertion/removal head 3 aligned with head 2 above. The insertion/removal head 3 comprises spring loaded jaws and is urged upwardly by a spring so that when the solder retaining the pins of the solid state device has been made molten, the head 3 springs upwardly to automatically remove the device. An optical alignment apparatus can be provided enabling any position on the upper surface of the board to be aligned with the head 2 underneath and when using this optical alignment apparatus the insertion/removal head may be dispensed with. <IMAGE>

Description

SPECIFICATION Soldering and desoldering apparatus The present invention relates to a tool enabling a multi-pin solid state electronic device to be soldered into or desoldered from a printed circuit board and an associated optical alignment apparatus.

Tools of this nature already exist. One such tool consists of a soldering iron having a hollow bit which, in operation, is heated and has suction applied to it so that the solder round a soldered pin can be first made molten and then sucked away. This tool has very definite limitations, however, for its use demands a certain level of skill and as each pin must be individually treated the soldering or desoldering of a multi-pin device is lengthy, tedious and expensive. In another tool, the solder holding all the pins of a multi-pin device is simultaneously melted using a heated soldering head disposed beneath the board to which the device is connected. The device can then be grasped from above the board and pulled clear.This tool suffers from problems in alignment which can lead to the solder around the pins of the wrong device being heated with the result that attempts to withdraw the correct device from the board can lead to damage to the device (if it is not already reject) and/or to damage to the board itself.

One other drawback of both of these tools is that the board is subjected to excessive temperature rises and this can cause connecting conductive lines on the board to lift from the board and/or distort resulting in further damage to the board which can be difficult, if not impossible, to repair.

In accordance with one aspect of the invention there is provided a tool for effecting soldering and desoldering operations on a printed circuit board comprising a base for supporting the board, a soldering head in the base for applying heat to the underside of the board, and an alignment apparatus for enabling a part of the upper surface of the board to be aligned with the soldering head.

According to another aspect of the present invention, there is provided an optical alignment apparatus comprising means for directing and focusing a light image on a piece of equipment enabling the position of a particular part of the surface of an opaque object to be aligned with the piece of equipment after the object has been placed over the piece of equipment with the surface remote from the object by allowing the image previously focused to fall on the remote surface of the object so placed.

According to another aspect of the present invention, there is provided a method of aligning a part of the surface of an opaque object with a piece of equipment disposed on that side of the opaque object remote from the surface including the steps of focusing a light image on the piece of equipment to locate and record the position of the piece of equipment, placing the opaque object over the piece of equipment and adjusting the position of the object until the light image previously focused falls on the desired surface part of the opaque object.

A preferred embodiment of the tool may comprise any one or more of the following preferred features.

(a) The alignment apparatus comprises a multi pin device insertion/removal head disposed above and in line with the soldering head and movable between a first, rest, position and a second activated position in which the device is grasped and subjected to an upward force by the insertion/removal head so that when the solder is made molten on the pins of the device the device is automatically withdrawn from the board.

(b) The soldering head comprises a solid block of thermally conductive material defining a cavity in which an electrical heat source is disposed and two recesses in the upper face thereof for solder, (c) The recesses of (b) are lined with stainless steel to protect the material of the block from the corrosive influence of the solder, (d) The block is made of copper or aluminium, (e) The heat source is a high wattage vitreous resistor disposed in a ceramic tube filled with aluminium oxide, (f) The insertion/removal head of (a) comprises a pair of jaws which may be opened against a resilient force and then released around a solid state device under the action of the resilient force to grasp the device, (g) The jaws of (f) are at opposite free ends of a U-shaped piece of resilient metal which is connected at the base of the 'U' to one end of a shaft slidably mounted in a surrounding collar and a compression spring surrounds the shaft and is constrained to act between the collar and the underside of a knob connected to the shaft such that in the rest position the shaft is urged out of the collar by the spring and the jaws are withdrawn within a jaw retainer to urge the jaws together, the jaws being extendable by depressing the shaft in the collar against the action of the spring to push the jaws out of the retainer and allow them to open.

(h) The insertion/removal head is pivotally mounted above and in line with the soldering head, (i) The pivot of the pivotal mounting of (h) is in substantially the same plane as the upper surface of the soldering head, (j) The insertion/removal head is reciprocably mounted above and in line with the soldering head, (k) One or more pieces of resilient material are disposed on the base adjacent the soldering head to act as a resilient support for a printed circuit board, (I) The resilient material of (k) is rubber or closed or open cell foamed synthetic plastics material.

In order that the invention may be more clearly understood, one embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which :- Figure 1 shows a diagrammatic plan view of a solid state device removal and soldering tool, Figure 2 is a diagrammatic partial cross section taken along the line Il-Il in Figure 1, Figure 3 is a diagrammatic partial cross-section taken along the line Ill-Ill in Figure 1, Figure 4 is a detail view of an insertion/removal head forming part of the tool of Figure 1, Figure 5 is a detail view of a soldering head forming part of the tool of Figure 1, and Figure 6 illustrates an optical alignment apparatus for use with the soldering and desoldering tool of Figures 1 to 5.

Referring to Figures 1 to 3, the tool basically comprises a base, indicated generally by the reference numeral 1, a soldering head indicated generally by the reference numeral 2, and an insertion removal head indicated generally by the reference numeral 3.

The base may be made of any suitable material such as, for example, sheet form aluminium or moulded synthetic plastics material. The upper surface 4 of the base is plane and defines an aperture 5 which accommodates the soldering head 2. At the end of the base 1 remote from the aperture 5 a support 6 is provided to which a boom 7 is pivotally connected.

The boom 7 is shown partially cut away in Figure 1 so as not to obscure the soldering head 2. From Figure 3 it can be seen that the free end of the boom 7 supports the removal head directly above and in vertical alignment with the soldering head 2. It can also be seen from Figure 3 that the pivot point 8 of the boom 7 and the upper surface of the soldering head 2 are in substantially the same horizontal plane.

Surrounding the aperture 5 are four strips 9 of resilient material. These strips are preferably of an open cell foamed synthetic plastics material, but they may equally well be of other material such as rubber. These strips provide a support for a printed circuit board to be operated on.

Referring to Figure 4 the insertion removal head 3 is shown in greater detail. This comprises a pair of jaws constituted by the free ends of the arms of a U-shaped piece 40 of spring steel. This piece 40 is connected by a screw connection to the lower threaded end of a shaft 41, the upper of which terminates in a knob 42. The shaft 41 slidably extends through a collar 43 which is connected at its lower end to a stirrup 44 having two substantially rigid downwardly depending legs 45. The legs 45 are disposed for slidable movement in a casing 46 and a compression spring 47 surrounds the shaft 41 and is constrained to act between the upper surface of the collar 43 and the lower surface of the knob 42. Two distance pieces 48 lie respectively alongside the upper parts of the legs 45 and are connected to the casing 46.

In the rest position of the removal head 3 shown the jaws of the piece 40 are open. The head can therefore be placed over the device to be removed from a printed circuit board and the jaws closed over the device to lock the head 3 in the device. The device will generally be a dual-in-line integrated circuit (DILIC). The jaws are locked over the device by pushing the casing 46 down over the legs 45. The distance pieces 48 move with the casing and effectively push the jaws of the piece 40 inwards. By this action, the spring 47 is compressed as the shaft 41 and knob 42 move downwardly with the piece 40 and with respect to the collar 43. An upward force is therefore applied to the grasped device by the spring 47 acting on the shaft 41 with the top of the collar 43 being used by the spring as a reaction surface.

Referring to Figure 5, the soldering head comprises a solid block 50 of material of good thermal conductivity. Aluminium or copper is preferred. The block 50 defines a bore 51 which houses a high wattage electrical resistor 52. The space 53 between the resistor 52 and the walls of the bore 51 is packed with paste material also of good thermal conductivity such as aluminium oxide. Insulated electrical leads 54 are connected to opposite ends respectively of the electrical resistor. The upper surface of the block 50 is formed with two relatively shallow cavities 57. These cavities are filled with solder in use and to prevent corrosive action by the solder in the material of the block 50 the cavities 57 are lined at 55 with a tinnable protective material such as stainless steel.The soldering head is supported on a column 56 so that the level of the upper surface of the head is just below the upper surface of the material strips 9 and substantially in the same horizontal plane as the pivot point 8 as previously mentioned.

In use, the tool is switched on to provide current to the head 3 and the cavities 57 are filled with molten solder. The removal head 3 of the tool is then aligned with the device to be removed and the jaws of the head 3 are closed over the device as described previously. The bottoms of the legs 45 abut the surface of the printed circuit board (PCB) adjacent the device and the jaws apply an upward force to the device. The board is then pressed down by hand over the soldering head 2 against the resilient strips 9 so that the pins of the device are immersed in the molten solder filled cavities 57 of the head. Heat is therefore applied to the solder surrounding the pins of the device to melt the solder and once this solder has been melted the device is automatically withdrawn due to the upward force being applied to it by the removal head 3.The jaws of the head 3 can then be opened to retrieve the device.

If desired a replacement device can now be resoldered into the position previously occupied by the removed device. The High friction nature of the strips 9 retains the PCB in the same position and the replacement device can then be inserted in the vacant holes in the board left by the moved device and the board lifted to allow the solder to solidify around the pins of the new device.

It will be appreciated that with the above described arrangement heat is only applied to the printed circuit board in the locality in which it is actually required and for the minimum time period. The upward force to which the device to be removed is subjected during the desoldering process means that as soon as the solder surrounding the pins of the device is molten the device is removed, thus enabling the board to be lifted under the resilient action of the strips 9 from the soldering head 2. In this way, the possibility of accidental damage to the board is reduced.

Referring to Figure 6, the optical alignment apparatus is fixed to the base 1 of the tool in which soldering and desoldering head 2 is housed. The alignment apparatus comprises an upright support 60 fixed to the base 1. A substantially horizontal boom 61 is adjustably mounted on the support 60 and may be fixed in a desired adjusted height position by means of the grub screw 62. The boom 61 supports a projector unit 63. This unit 63 compris es a light source 64, a slide mount 65, and a lens array 66 (the unit 63 may be a photographic enlarger or slide projector appropriately modified).

In use, a slide carrying an image of the molten solder areas of the soldering head 2 is inserted in the slide mount 65 and the light source illuminated to project an image of these areas onto the real molten solder areas of the head 2. Focusing of the image on the areas is achieved by appropriate height positioning of the boom 61 and/or adjustment of the lens array 66. After focusing a printed circuit board is placed over the head and the light image now projected on the board precisely identifies the position of the soldering head 2 underneath and enables any component or set of holes on the board to be precisely aligned with the head 2. This precise and accurate alignment greatly facilitates soldering and desoldering operations. The removal head 3 previously described can be made adjustable and aligned with the light image or can be dispensed with altogether.On component insertion, the component is simply placed into position indicated by the light image and then soldered into position using the soldering head 2.

It will also be appreciated that the above embodiments have been described by way of example only and that many variations are possible without departing from the scope of the invention. For example, the temperature of the soldering head can be thermostatically controlled. In one such arrangement, a thermocouple would be embedded in the block 50 of the head and the signals from this thermo-couple used to control the power fed to the electrical resistor in the head. Suitable control circuitry might, for example, include a triac, the firing mark space ratio of which could be varied to give the required power supply level to the resistor. Also, some indication could advantageously be provided indicating when the power supply to the head was switched on. A light emitting diode would be suitable for this purpose.

Claims

1. Atool for effecting soldering and desoldering operations on a printed circuit board comprising a base for supporting the board, a soldering head in the base for applying heat to the underside of the board, and an alignment apparatus for enabling a part of the upper surface of the board to be aligned with the soldering head.

2. Atool as claimed in Claim 1, in which the alignment apparatus comprises a multi pin device insertion/removal head disposed above and in line with the soldering head and movable between a first, rest, position and a second activated position in which the device is grasped and subjected to an upward force by the insertion/removal head so that when the solder is made molten on the pins of the device the device is automatically withdrawn from the board.

3. A tool as claimed in Claim 1 or 2, in which the soldering head comprises a solid block of thermally conductive material defining a cavity in which an electrical heat source is disposed and two recesses in the upper face thereof for solder.

4 A tool as claimed in Claim 3, in which the recesses are lined with stainless steel to protect the material of the block from corrosive influence of the solder.

5. Atool as claimedsin Claim 3 or 4, in which the block is made of copper or aluminium.

6. A tool as claimed in Claim 3,4 or 5, in which the heat source is a high wattage vitreous resistor disposed in a ceramic tube filled with aluminium oxide.

7. Atool as claimed in Claim 2 or in any of Claims 3 to 6 when appendant to Claim 2, in which the insertion/removal head comprises a pair of jaws which may be opened against a resilient force and then released around a solid state device under the action of the resilient force to grasp the device.

8. A tool as claimed in Claim 7, in which the jaws are at opposite free ends of a U-shaped piece of resilient metal which is connected at the base of the 'U' to one end of a shaft slidably mounted in a surrounding collar and a compression spring surrounds the shaft and is constrained to act between the collar and the underside of a knob connected to the shaft such that in the rest position the shaft is urged out of the collar by the spring and the jaws are withdrawn within a jaw retainer to urge the jaws together, the jaws being extendable by depressing the shaft in the collar against the action of the spring to push the jaws out of the retainer and allow them to open.

9. A tool as claimed in Claim 2, or in any of Claims 3 to 8 when appendant to Claim 2, in which the insertion/removal head is pivotally mounted above and in line with the soldering head.

10. A tool as claimed in Claim 9, in which the pivot of the pivotal mounting is in substantially the same plane as the upper surface of the soldering head.

11. A tool as claimed in Claim 2 or in any of Claims 3 to 8 when appendant to Claim 2, in which the insertion/removal head is reciprocably mounted above and in line with the soldering head.

12. Atool as claimed in any preceding claim, in which one or more pieces of resilient material are disposed on the base adjacent the soldering head to act as a resilient support for a printed circuit board.

13. A tool as claimed in Claim 12, in which the resilient material is rubber or closed or open cell foamed synthetic plastics material.

14. A tool as claimed in Claim 1, in which the alignment apparatus is optical.

15. A tool for enabling a multi-pin solid state electronic device to be removed from a printed circuit board substantially as hereinbefore described with reference to Figures 1 to 5, or to these figures with the modification of Figure 6 of the accompanying drawings.

15. Atool as claimed in Claim 14, in which the optical alignment apparatus comprises means for directing and focusing a light image on the soldering head to locate and record the position of this head.

16. Atool for enabling a multi-pin solid state electronic device to be removed from a printed circuit board substantially as hereinbefore described with reference to Figures 1 to 5, or to these figures with the modification of Figure 6 of the accompanying drawings.

17. An optical alignment apparatus comprising means for directing and focusing a light image on a piece of equipment enabling the position of a particular part of the surface of an opaque object to be aligned with the piece of equipment after the object has been placed over the piece of equipment with the surface remote from the object by allowing the image previously focused to fall on the remote surface of the object so placed.

18. A method of aligning a part of the surface of an opaque object with a piece of equipment disposed on that side of the opaque object remote from the surface including the steps of focusing a light image on the piece of equipment to locate and record the position of the piece of equipment, placing the opaque object over the piece of equipment and adjusting the position of the object until the light image previously focused falls on the desired surface part of the opaque object.

19. An optical alignment apparatus substantially as hereinbefore described with reference to Figure 6 of the accompanying drawings.

20. A method of aligning a part of the surface of an opaque object with a piece of equipment substantially as hereinbefore described with reference to the accompanying drawings.

New claims or amendments to claims filed on 2.2.81 Superseded claims 1-20 New or amended claims:- 1-15

1. A tool for effecting soldering and desoldering operations on a printed circuit board comprising a base for supporting the board, a soldering head in the base for applying heat to the underside of the board, and an optical alignment apparatus for enabling a part of the upper surface of the board to be aligned with the soldering head.

2. A tool as claimed in Claim 1, in which, in addition, a removal head is provided for removing a component on the board, released by application of the soldering head.

3. Atool as claimed in Claim 1 or 2, in which the soldering head comprises a solid block of thermally conductive material defining a cavity in which an electrical heat source is disposed and two recesses in the upper face thereof for solder.

4. Atool as claimed in Claim 3, in which the recesses are lined with stainless steel to protect the material of the block from the corrosive influence of the solder.

5. A tool as claimed in Claim 3 or 4, in which the block is made of copper or aluminium.

6. A tool as claimed in Claim 3,4 or Sin which the heat source is a high wattage vitreous resistor disposed in a ceramic tube filled with aluminium oxide.

7. A tool as claimed in Claim 2 or in any of Claims 3 to 6 when appendant to Claim 2, in which the removal head comprises a pair of jaws which may be opened against a resilient force and then released around a solid state device under the action of the resilient force to grasp the device.

8. Atool as claimed in Claim 7, in which the jaws are at opposite free ends of a U-shaped piece of resilient metal which is connected at the base of the 'U' to one end of a shaft slidably mounted in a surrounding collar and a compression spring surrounds the shaft and is constrained to act between the collar and the underside of a knob connected to the shaft such that in the rest position the shaft is urged out of the collar by the spring and the jaws are withdrawn within a jaw retainer to urge the jaws together, the jaws being extendable by depressing the shaft in the collar against the action of the spring to push the jaws out of the retainer and allow them to open.

9. A tool as claimed in Claim 2, or in any of Claims 3 to 8 when appendant to Claim 2, in which the removal head is pivotally mounted above and in line with the soldering head.

11. Atool as claimed in Claim 2 or in any of Claims 3 to 8 when appendant to Claim 2, in which the removal head is reciprocably mounted above and in line with the soldering head.

14. Atool as claimed in any preceding Claim, in which the optical alignment apparatus comprises means for directing and focusing a light image on the soldering head to locate and record the position of this head.