GB2042957A

GB2042957A - An Improved Fluxing Unit for use in Soldering

Info

Publication number: GB2042957A
Application number: GB8004660A
Authority: GB
Original assignee: Frys Metals Ltd
Current assignee: Fernox Ltd
Priority date: 1979-02-14
Filing date: 1980-02-12
Publication date: 1980-10-01
Also published as: GB2042957B

Abstract

A fluxing unit for applying flux to components to be subjected to wave soldering includes a tank 10 for containing flux solution and a pump 12 for pumping the flux solution through a nozzle 14 from which it overflows as a wave or, as shown, a cushion of foam. A vessel 15 containing a hydrometer 16 is disposed alongside the tank and a valve-controlled by-pass line 19 is provided to enable flux solution to be pumped, when desired, to the vessel to test the solution density so as to determine when topping up of the flux solution with solvent is necessary. The vessel 15 may also contain a thermometer and be used to indicate when further flux solution should be added to the tank. The flux solution may comprise activated rosin in a solvent, e.g. isopropyl alcohol. <IMAGE>

Description

SPECIFICATION An Improved Fluxing Unit for Use in Soldering It is well known to apply solder to components, such for example as printed circuit boards, by wave soldering, i.e. by traversing the components in succession through a wave by solder overflowing from a nozzle. Before, however, the components reach the solder wave it is necessary to apply flux to them. This may be effected in either of the following ways.

The components may be traversed in succession through a wave fluxing unit of the wave type, which is generally similar to the soldering unit, having a slot-like nozzle extending transversely to the direction of travel of the components and through which flux is pumped upwardly to overflow as a wave through which the components pass. Alternatively a foam type fluxing unit may be employed, in which the flux is pumped upwardly into an outlet nozzle which contains at its lower end a mass of porous material known as a stone into which air is pumped under pressure so as to entrain air bubbles in the flux emerging from the nozzle and so form a stable cushion of foam above the nozzle through which the components are passed.

The flux used consists of a solution of fluxing agent, generally activated rosin, in a volatile solvent, e.g. isopropyl alcohol. In use of the fluxing unit the flux which overflows from the nozzle is recirculated to the pump but after a time there is a significant depletion in solvent, particularly in the case of a unit of the foam type, and it is necessary to top the flux up with solvent to restore it to the correct concentration.

Hitherto the practice has been to withdraw a sample of flux from the unit in a suitable vessel and transfer it to a transparent test cylinder in which its density is measured by a hydrometer and add further solvent to the flux in the unit as necessary in accordance with the indications of the hydrometer.

Attempts have been made to render such sampling unnecessary by immersing a hydrometer in the fluxing unit itself, but deposition of fluxing agent on the hydrometer from flux depleted in solvent has been found to render this impracticable.

The invention provides a fluxing unit, for applying flux to components to be subjected to wave soldering, comprising a tank to contain flux solution, a pump operable to pump the flux solution upwardly from the tank through a nozzle above the tank, a vessel disposed alongside the tank and containing a hydrometer, a pipe connecting the lower end of the vessel to the inlet of the pump and another pipe containing a valve and disposed between the outlet of the pump and the vessel to enable, by opening the valve, flux solution to be delivered by the pump from the tank to the vessel for testing by the hydrometer.

One embodiment of foam type fluxing unit according to the invention is illustrated in the accompanying drawing. It includes a tank 10 containing flux solution from which the solution is pumped by a pump 12 through a pipe 1 1, containing a normally open valve A, to a tray 1 7 disposed within the tank 10 and having a slot 14 at its upper end. Compressed air is blown from a pipe 18 into the tray 17 through a porous stone 13 at the base of the tray. Accordingly a cushion of foam is formed above the nozzle 14 through which the components to be fluxed are traversed by a conveyor (not shown), excess flux solution overflowing into the tank 10. The valve A is adjusted to maintain the height of the cushion at the desired value.

Alongside the tank 10 is a transparent test cylinder 15, which contains a hydrometer 16, and the lower end of which communicates with the pipe 1 1 by a pipe 19 containing a normally closed valve B. When it is desired to test the density of the flux solution, the valve B is opened to cause flux solution to be pumped into the cylinder 15 by the pump 12 and rise therein to the same level as in the tank 10. The level to which the hydrometer 16 floats can be read off on graduations on the hydrometer. The operator is provided with suitable tablets to indicate how much solvent should be added to restore the flux to the desired concentration when the hydrometer indicates a deviation from the correct density. The cylinder 1 5 may also contain a thermometer to enable any necessary temperature corrections to be made.

Preferably addition of solvent is made to the cylinder 15, which has a funnel shaped top, after closing the valve B. Such addition serves to wash flux from the hydrometer 1 6 and the wall of the cylinder 1 5 before any fluxing agent deposits thereon to any significant extent.

While periodic opening of the valve B for testing purposes will affect for a few moments the level of the foam cushion above the nozzle 14, it has been found unnecessary to change the setting of the valve A during the brief and infrequent testing periods.

The apparatus illustrated also enables the level of flux solution in the tank 10 to be tested with a view to determining when it is necessary to introduce fresh flux solution into the tank. This is achieved by shutting off the pump 12 momentarily with the valve B open. The level of solution in the tank can then be read on graduations on the cylinder 15.

As will be appreciated, the fluxing unit may, as an alternative, be a unit in which the flux solution is discharged by the pump through a nozzle as an overflowing wave rather than as a cushion of foam.

Claims

1. A fluxing unit, for applying flux to components to be subjected to wave soldering, comprising a tank to contain flux solution, a pump operable to pump the flux solution upwardly from the tank through a nozzle above the tank, a vessel disposed alongside the tank and containing a hydrometer, a pipe connecting the lower end of the vessel to the inlet of the pump and another

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION An Improved Fluxing Unit for Use in Soldering It is well known to apply solder to components, such for example as printed circuit boards, by wave soldering, i.e. by traversing the components in succession through a wave by solder overflowing from a nozzle. Before, however, the components reach the solder wave it is necessary to apply flux to them. This may be effected in either of the following ways. The components may be traversed in succession through a wave fluxing unit of the wave type, which is generally similar to the soldering unit, having a slot-like nozzle extending transversely to the direction of travel of the components and through which flux is pumped upwardly to overflow as a wave through which the components pass. Alternatively a foam type fluxing unit may be employed, in which the flux is pumped upwardly into an outlet nozzle which contains at its lower end a mass of porous material known as a stone into which air is pumped under pressure so as to entrain air bubbles in the flux emerging from the nozzle and so form a stable cushion of foam above the nozzle through which the components are passed. The flux used consists of a solution of fluxing agent, generally activated rosin, in a volatile solvent, e.g. isopropyl alcohol. In use of the fluxing unit the flux which overflows from the nozzle is recirculated to the pump but after a time there is a significant depletion in solvent, particularly in the case of a unit of the foam type, and it is necessary to top the flux up with solvent to restore it to the correct concentration. Hitherto the practice has been to withdraw a sample of flux from the unit in a suitable vessel and transfer it to a transparent test cylinder in which its density is measured by a hydrometer and add further solvent to the flux in the unit as necessary in accordance with the indications of the hydrometer. Attempts have been made to render such sampling unnecessary by immersing a hydrometer in the fluxing unit itself, but deposition of fluxing agent on the hydrometer from flux depleted in solvent has been found to render this impracticable. The invention provides a fluxing unit, for applying flux to components to be subjected to wave soldering, comprising a tank to contain flux solution, a pump operable to pump the flux solution upwardly from the tank through a nozzle above the tank, a vessel disposed alongside the tank and containing a hydrometer, a pipe connecting the lower end of the vessel to the inlet of the pump and another pipe containing a valve and disposed between the outlet of the pump and the vessel to enable, by opening the valve, flux solution to be delivered by the pump from the tank to the vessel for testing by the hydrometer. One embodiment of foam type fluxing unit according to the invention is illustrated in the accompanying drawing. It includes a tank 10 containing flux solution from which the solution is pumped by a pump 12 through a pipe 1 1, containing a normally open valve A, to a tray 1 7 disposed within the tank 10 and having a slot 14 at its upper end. Compressed air is blown from a pipe 18 into the tray 17 through a porous stone 13 at the base of the tray. Accordingly a cushion of foam is formed above the nozzle 14 through which the components to be fluxed are traversed by a conveyor (not shown), excess flux solution overflowing into the tank 10. The valve A is adjusted to maintain the height of the cushion at the desired value. Alongside the tank 10 is a transparent test cylinder 15, which contains a hydrometer 16, and the lower end of which communicates with the pipe 1 1 by a pipe 19 containing a normally closed valve B. When it is desired to test the density of the flux solution, the valve B is opened to cause flux solution to be pumped into the cylinder 15 by the pump 12 and rise therein to the same level as in the tank 10. The level to which the hydrometer 16 floats can be read off on graduations on the hydrometer. The operator is provided with suitable tablets to indicate how much solvent should be added to restore the flux to the desired concentration when the hydrometer indicates a deviation from the correct density. The cylinder 1 5 may also contain a thermometer to enable any necessary temperature corrections to be made. Preferably addition of solvent is made to the cylinder 15, which has a funnel shaped top, after closing the valve B. Such addition serves to wash flux from the hydrometer 1 6 and the wall of the cylinder 1 5 before any fluxing agent deposits thereon to any significant extent. While periodic opening of the valve B for testing purposes will affect for a few moments the level of the foam cushion above the nozzle 14, it has been found unnecessary to change the setting of the valve A during the brief and infrequent testing periods. The apparatus illustrated also enables the level of flux solution in the tank 10 to be tested with a view to determining when it is necessary to introduce fresh flux solution into the tank. This is achieved by shutting off the pump 12 momentarily with the valve B open. The level of solution in the tank can then be read on graduations on the cylinder 15. As will be appreciated, the fluxing unit may, as an alternative, be a unit in which the flux solution is discharged by the pump through a nozzle as an overflowing wave rather than as a cushion of foam. Claims

1. A fluxing unit, for applying flux to components to be subjected to wave soldering, comprising a tank to contain flux solution, a pump operable to pump the flux solution upwardly from the tank through a nozzle above the tank, a vessel disposed alongside the tank and containing a hydrometer, a pipe connecting the lower end of the vessel to the inlet of the pump and another pipe containing a valve and disposed between the outlet of the pump and the vessel to enable, by opening the valve, flux solution to be delivered by the pump from the tank to the vessel for testing by the hydrometer.

2. A fluxing unit according to claim 1 , which includes a tray in the tank which contains a porous stone through which the flux solution is pumped to the nozzle and means for blowing compressed air into the tray through the porous stone to form a cushion of foamed flux solution above the nozzle.

3. A fluxing unit according to claim 1, in which the vessel is a transparent cylinder with a funnel shaped top.

4. A fluxing unit according to claim 1, substantially as described herein with reference to the accompanying drawing.