GB2150064A

GB2150064A - Solder method and apparatus

Info

Publication number: GB2150064A
Application number: GB08429267A
Authority: GB
Inventors: Bernard Eric Thumwood
Original assignee: TREIBER AUTOMATION Ltd
Current assignee: TREIBER AUTOMATION Ltd
Priority date: 1983-11-23
Filing date: 1984-11-20
Publication date: 1985-06-26
Also published as: GB8331200D0; GB2150064B; GB8429267D0

Abstract

Apparatus 1 for applying solder to a circuit board or component (not shown) comprising nozzle means 2 adapted to form a wave 3 of solder which flows in a direction shown by arrow 'X', conveyor means having an upwardly inclined path 4 over the nozzle means 2 and adapted to move in a direction shown by arrow 'Y', opposite the direction 'X', and means in the form of an adjustable plate 5 which can adjust the relative disposition of the wave 3 and path 4 so as to provide a desired relation between them for contact of the circuit board member or component with the solder. <IMAGE>

Description

SPECIFICATION Solder method and apparatus The invention relates to a solder method and apparatus, particularly for soldering electrical circuit board members or components by passing the members or components through a standing wave of molten solder.

In proposed methods and apparatus for such soldering, solder is passed upwardly from a reservoir through an upwardly directed nozzle, to flow from the nozzle to form a wave before returning to the reservoir. Such prior methods and apparatus cannot be adjusted to take account of different types of boards or components being soldered. For example in some instances a flat board has to be soldered, while in another instance a board with particularly long depending pins may have to be soldered. The proposed equipment cannot readily accommodate these different boards or components.

It is accordingly an object of the invention to seek to mitigate the disadvantages of the prior art.

According to one aspect of the invention there is provided a method of applying solder to a circuit board member or component, comprising providing nozzle means adapted to form a wave of solder, passing a circuit board member or component along an upwardly inclined path in a direction opposite to the direction of flow of the wave and so that the wave and circuit board member or component come into contact, and providing means to adjust the relative disposition of the wave and path so as to provide a desired relation between them for contact of the circuit board member or component with the solder.

According to a second aspect of the invention there is provided apparatus for applying solder to a circuit board member or component, comprising nozzle means adapted to form a wave of solder, conveyor means having an upwardly inclined path over the nozzle means and adapted (in use) to move in a direction opposite to the direction of flow of the wave, and means to adjust the relative disposition of the wave and path so as to provide a desired relation between them for contact of the circuit board member or component with the solder.

The means may be substantially vertically adjustable plate over which the solder flows from the nozzle means to form the wave.

The plate may comprise a downstream extension of the nozzle means.

The plate may be adjustable manually, mechanically, electrically, electro-mechanically, pneumatually, hydraulically or any other suitable means.

The adjustment of the plate means may be controlled by numerical control such as computer controlled means.

Embodiments of the invention are hereinafter described, by way of example, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1,2 and 3 each show schematic vertical sectional views of respective first, second and third embodiments according to the invention; Figures 4 and 5 show to a larger scale fourth and fifth embodiments, respectively, according to the invention; and Figure 6 shows to a smaller scale than Fig.

5 that embodiment in use.

In the drawings, like parts are referred to by like reference numerals.

Referring to firstly Fig. 1 there is shown apparatus 1 for applying solder to a circuit board or component (not shown) comprising nozzle means 2 adapted to form a wave 3 of solder which flows in a direction shown by arrow 'X', conveyor means having an upwardly inclined path 4 over the nozzle means 2 and adapted to move in a direction shown by arrow 'Y', opposite the direction 'X', and means in the form of an adjustable plate 5 which can adjust the relative disposition of the wave 3 and path 4 so as to provide a desired relation between them for contact of the circuit board member or component with the solder.

The plate 5 is adjustable in a substantially vertical direction as shown by double-headed arrows 'Z'. The plate 5 is essentially of inverted channel shape and one limb 6 is secured for adjustable sliding movement in relation to the lip 7 of the fixed nozzle means 2. The adjustable plate 5 thus forms a downstream extension of the nozzle means 2.

The nozzle means 2 has an internal inclined baffle 8 forming with a lip 9 opposite the lip 7 a secondary reservoir 10 to assist in providing a stable flow of solder both over the plate 5 and over the lip 9 as shown.

The nozzle means 2 is fed upwardly from a main reservoir or pot, not shown, the solder flowing out through the exit of the nozzle means over the plate to form the wave 3, and over the lip 9. The solder returns to the main reservoir or pot for re-circulation through the nozzle means 2. The wave 3 has a curved upper surface and decreases in thickness or depth as it flows under gravity from the exit of the nozzle means 2 as the solder flows at a constant speed upwardly out of the nozzle means 2. The circuit board members or components to be soldered pass on the conveyor along the path 4, contact the wave 3, and are soldered the required amount.

If for any reason it is desired to alter the relative positions of the wave 3 and path 4, for example because electrical circuit boards having depending contacts or pins of an increased length in relation to those previously being soldered, the conveyor. nozzle means, main reservoir and indeed volume of solder all remain fixed, but the plate 5 is adjusted in position vertically to a desired height by sliding the limb 6 in relation to the lip 7 and then clamping it in the new desired position as by releasable fastening means such as a nut and bolt arrangement. The limb may have an elongate slot which slides over the nut and bolt arrangement when the nut is slackened off for adjustment.The wave front is thus effectively raised or lowered by this operation and the practical result is that the exact position of the solder wave 3 is fixed in relation to any component parameter such as lead or pin length which may vary. This means that a relatively small amount of solder need be pumped through the nozzle means, so that the amount of oxide, or dross, formed on the surface of the wave is reduced, so reducing the likelihood of oxide occlusions being formed on the board member or component, which oxide can otherwise lead to poor electrical connections, local distortion and generally a poor quality. The method and apparatus embodying the invention obviate these disadvantages.

Fig. 2 shows an embodiment 20 similar to that of Fig. 1, but without the internal baffle 8.

Fig. 3 shows an embodiment 30 similar to that of Fig. 1, but in which the lip 9 is extended to provide a flat plate 31 with an upstanding lip or weir 32 over which the remainder 33 of the solder not forming the wave 3 flows to return to the main reservoir.

Referring now to Figs. 4 to 6, in the orientation shown the travel of the boards (not shown) to be soldered is from right to left as viewed, while in Fig. 6 the board travel is from left to right.

Fig. 4 shows apparatus 40 having a plate 41 which is of inverted channel section and is mounted for vertical adjustment on the lip 42 of the solder nozzle 43 of the apparatus 40.

One limb 44 of the channel section plate 41 is bifurcated and comprises two parallel limb parts 46 and 47 which are spaced apart a distance to accommodate as a sliding fit and lip 42 of the nozzle 43. The limb parts 46 and 47 are spaced apart by a spacer 48 to which they are secured as by spot welding.

The limb parts 46 and 47 and spacer 48 thus form a guide for guiding the plate 41 during vertical movement for adjusting its vertical position. The web 49 of the channel-section plate 41 is mounted on two spaced parallel screws 50 and 51 which are mounted in a fixed screw threaded block 52 secured to the frame of the apparatus 40.

The plate 41 has through holes 53 aligned with the heads of the screws 50 and 51.

The screws 50. 51 may be then extended and retracted to adjust the vertical spacing between the wave flowing over the plate 41 and the printed circuit boards, by inserting a suitable tool such as a screw-driver down through the solder and holes to engage the screwheads, to effect adjustment.

The limb 54 of the plate 41 also mounts a vertically adjustable weir 55, which can be adjusted in position as desired between a fully retracted position, shown in full line and a fully extended position shown in dashed lines.

This weir 55 when extended provides an initial crest to the solder wave for providing an initial soldering before main solder application takes place.

The nozzle 43 also has a rear reservoir 56 in which solder is received to provide a virtually stationary pool of solder on the exit side of the nozzle 43.

Referring now to Figs. 5 and 6, the apparatus 60 shown is similar to that of Fig. 4 in that the plate 61 has a guide formed at limb 62 by limb parts 63 and 64 and a spacer 65 and in that the web 66 is mounted on two spaced vertically screws 67 and 68 under aligned holes in the plate the screws being mounted in a block 69. The vertical adjustment is shown by the arrow 70 in Fig. 6, which also shows the flow of the solder as it wells out of the nozzle 71 flows over the plate 61 and an opposite lip 72 to the solder at level 73 in the apparatus. The apparatus 60 includes an inclined plate 74 spaced from the limb 72 of the plate 61 which when the position provides the additional wave profile shown for soldering electronic components known as "chips". The plate 74 is removable, and is mounted as by a nut and bolt arrangement (not shown).In both apparatuses 40 and 60 the respective nozzle 43 and 71 includes suitable baffles 75 for providing a desired flow of solder upwardly to the exit of the nozzle, to flow over the vertically adjustable plate 41 or 61.

In every embodiment, the adjustable plate 5 can be adjusted manually, or mechanically or by any other suitable means. Moreover, in a numerically-controlled soldering process, the position of the plate 5 can be adjusted automatically by means which are computer-controlled, it merely being necessary to key into the computer the relevant parameters of the board or component being soldered for the means to be actuated to adjust the position of the plate 5 to provide the exact position of the wave 3 for the particular soldering operation.

In the embodiments of Figs. 1 to 3 the upper surface of the solder waves 3 is shown curved upwardly for clarity. In actual practice, the waves have a convex configuration in cross-section as considered in the direction of flow of the waves in the direction of arrow "X", as shown in Fig. 6.

Claims

1. A method of applying solder to a circuit board or component, comprising providing nozzle means adapted to form a wave of solder, passing a circuit board member or component along an upwardly inclined path in a direction opposite to the direction of flow of the wave and so that the wave the circuit board member or component come into contact, and providing means to adjust the relative disposition of the wave and path so as to provide a desired relation between them for contact of the circuit board member or component with the solder.

2. A method according to Claim 1, comprising adjusting the substantially vertical spacing of the wave and path.

3. A method according to Claim 2, comprising adjusting the vertical spacing automatically.

4. A method according to Claim 2 or Claim 3, comprising effecting the vertical adjustment mechanically.

5. A method according to Claim 1, substantially as hereinbefore described with reference to the accompanying drawings.

6. Apparatus for applying solder to a circuit board member or component, comprising nozzle means adapted to form a wave of solder, conveyor means having an upwardly inclined path over the nozzle and adapted (in use) to move in a direction opposite to the direction of flow of the wave, and means to adjust the relative disposition of the wave and path so as to provide a desired relation between them for contact of the circuit board member or component with the solder in use.

7. Apparatus according to Claim 6, the means comprising a substantially vertically adjustable plate over which the solder flows from the nozzle means to form the wave in use.

8. Apparatus according to Claim 7, the plate comprising a downstream extension of the nozzle means.

9. Apparatus according to Claim 8, the plate having a limb which is adjustably mounted to a lip of the nozzle means.

10. Apparatus according to Claim 9, the limb being adjustable in relation to the lip by sliding.

11. Apparatus according to Claim 10, the limb being secured in an adjusted position by releasable fastening means.

12. Apparatus according to Claim 10 or Claim 11, in which the limb is mounted on an external surface of the lip.

13. Apparatus according to any of Claims 9 to 12, the plate being of inverted channel shape.

14. Apparatus according to any of Claims 6 to 13, the plate being connected to automatic means for automatic adjustment thereof.

15. Apparatus according to Claim 14, the automatic means being mechanical means.

16. Apparatus according to Claim 14 or Claim 15. the automatic means being numerically controlled means.

17. Apparatus according to any of Claims 8 to 16, the nozzle including a baffle inclined with respect to a lip opposite the lip including the plate.

18. Apparatus according to any of Claims 8 to 16, the nozzle including a further plate directed away from the adjustable plate on the opposite side of the nozzle.

19. Apparatus according to Claim 18, the further plate being fixed.

20. Apparatus according to Claim 18 or Claim 19, for further plate terminating in an upstanding plate over which solder flows in use.

21. Apparatus for applying solder to a circuit board member or component substantially as hereinbefore described with reference to the accompanying drawings.