GB2261184A

GB2261184A - Wave soldering

Info

Publication number: GB2261184A
Application number: GB9223339A
Authority: GB
Inventors: Andrew Clarke; John Dalgleish
Original assignee: AUTOMATION Ltd
Current assignee: AUTOMATION Ltd
Priority date: 1991-11-06
Filing date: 1992-11-06
Publication date: 1993-05-12
Also published as: GB9223339D0; GB9123549D0

Abstract

In a wave soldering apparatus a nozzle 2 forms a solder wave beneath a predetermined path to be followed by the article such as a printed circuit board to be soldered and a device 3 within the nozzle is freely oscillatable in the range 0-9 Hertz for producing oscillations in the wave. 7 Hertz is a particularly suitable frequency. The device 3 is a rod supported on springs 7 whose tension is variable to adjust the frequency of oscillation. <IMAGE>

Description

CHIP EVES The invention relates to chip waves, particularly to waves formed in an apparatus and method for wave soldering printed circuit boards or the like.

In the past, oxide or dross production is produced by the solder waves used, leading to inefficient soldering.

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

According to a first aspect of the invention there is provided apparatus for wave soldering a printed circuit board or the like, comprising means for moving the board along a predetermined path so that at least a portion of the board passes through a solder wave formed beneath (as considered in use) the path by a nozzle, and associated with the nozzle a device freely oscillatable in the range 0 to 9 Hertz for producing oscillations in the wave.

The oscillations of the device being in the range 0 to 7 Hertz, preferably about 7 Hertz. This provides for optimum operation.

The device may be mounted in the nozzle by means oscillatable by flow of liquid solder past the device. The construction provides that the device is operated by the solder flow, and not by any additional motive means, which saves on energy and capital cost at least The means may comprise resilient means This is a relatively simple construction The resilient means may ca#orise a spring means at each side of the nozzle and the device may be a relatively rigid elongate member extending between and connected with the spring means.

The spring means may be mounted externally of the nozzle and respective housings. This is a relatively simple construction, whereby the springs are kept clear of the solder.

The tension of the spring means may be adjustable whereby to adjust the oscillations of the elongate member. This construction copes with varying solder flows.

The elongate member may comprise a bar According to a second aspect of the invention there is provided a process for wave soldering a printed circuit board or the like, comprising the steps of moving a board along a predetermined path and forming a solder wave of a desired configuration below the path, passing at least a portion of the board through the wave, and oscillating the wave in a range of oscillations up to about 18 Hertz.

The oscillations in the wave may be about 14 Hertz.

A nozzle of apparatus embodying the invention is hereinafter described, by way example, with reference to the accompanying drawings Fig.l is a schematic side elevational view, partly in section, of the nozzle of the apparatus according to the invention; and Fig.2 is a plan view of the nozzle of Fig.l, with part in section.

Referring to the drawings, there is shown apparatus 1 for wave soldering a printed circuit board or the like (not shown), comprising means (also not shown) for moving the board along a predetermined path so that at least a portion of the board passes through a solder wave formed beneath (as considered in use and as viewed in Fig.l) the path by a nozzle 2, and associated with the nozzle 2 a device 3 freely oscillatable in the range 0 to 9 Hertz for producing oscillations in the wave Typically, the device 3 oscillates at about 7 Hertz, i.e. producing oscillations of about 14 Hertz in the wave. There is thus a doubling of frequency between the oscillations of wave and device.

It will be understood that the nozzle 2 produces a relatively narrow turbulent wave upstream of the path, and that it is associated with a second nozzle 4 of the apparatus 1 downstream of the path. The second nozzle 4 and wave essentially complete the soldering process. However, the invention is concerned with the first nozzle 2, the wave of which is oscillatable by the device 3 in the form of an elongate member, or round bar in the embodiment, which extends across the whole width of the nozzle 2 at or in the mouth 5 thereof between converging walls 6 which define the nozzle 2 The bar 3 is freely mounted in, that it is not connected with separated motive means for causing its oscillation.Instead it is oscillatable by means in the form of springs 7 mounted at opposite ends of the bar 3, the springs 7 being external of the nozzle 2 and mounted in housings 8 secured to respective side cheeks 9 of the nozzle 2 The springs 7 are each adjustable in tension by a nut 10 mounted on a screw rod 11 projecting from the respective housing 8, the nut 10 being screwed up against an end wall 12 of the housing 8 to adjust the tension of the spring(s) 7 and hence the range in which the bar 3 oscillates.

In use, the nozzles 2, 4 are mounted in a pot of molten solder which by suitable pump means is caused to well up the nozzles 2 & BR< 4, overlow the upper edges thereof and flow back to the pot. In welling out of the nozzles, the solder assumes a wave configuration through which the circuit board being soldered passes. The bar 3 in the nozzle 2 lies in the path of the solder, effectively blocking flow. In order to overcome this, the solder forces its way past the sides 6 of the nozzle and resiliently mounted bar 3. This action causes the bar 3 to oscillate or resonate from side to side of the nozzle 2, so producing oscillations of 14 Hertz optrmin in the wave. This aids in filling in voids or the like in the board and/or adjacent components thereon where wetting is normally difficult. At the same time any nucleated gas bubbles in the solder are shifted, again leading to an improved soldering action. The nozzle 2 thus provides a substantially parallel resonance integral surface mount in that the oscillations are substantially parallel to the path of the board.

Claims

CLUBS

1. Apparatus for wave soldering a printed circuit board or the like comprising means for moving the board along a predetermined path so that at least a portion of the board passes through a solder wave formed beneath (as considered in use) the path by a nozzle, and associated with the nozzle a device freely oscillatable in the range 0 to 9 Hertz for producing oscillations in the wave.

2. Apparatus according to Claim 1, the oscillations of the device being in the range 0 to 7 Hertz 3. Apparatus according to Claim 2, the oscillations of the device being 7 Hertz.

4. Apparatus according to any preceding claim, the device being mounted in the nozzle by means oscillatable by flow of liquid solder past the device.

5. Apparatus according to Claim 4, the means comprising resilient means.

6. Apparatus according to Claim 5, the resilient means carising a spring means at each side of the nozzle and the device being a relatively rigid elongate member extending between and connected with the spring means.

7. Apparatus according to Claim 6, the spring means being mounted externally of the nozzle in respective housings.

8. Apparatus according to Claim 6 or Claim 7, the tension of the spring means being adjustable whereby to adjust the oscillations of the elongate member 7. Apparatus according to either of Claims 7 & 8, the elongate member comprising a bar.

10. Apparatus for wave soldering a printed circuit board or the like, substantially as hereinbefore described with reference to the accompanying drawings.

11. A process for wave soldering a printed circuit board or the like, comprising the steps of moving a board along a predetermined path, forming a solder wave of a desired configuration below the path, passing at least a portion of the board through the wave, and oscillating the wave in a range of oscillations up to about 18 Hertz.

12. A process according to Claim 11, the oscillations in the wave being about 14 Hertz 13 A process for soldering a printed circuit board or the like, substantially as hereinbefore described with reference to the accompanying drawings.