ICSF Curve

Suitable for

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  Spray fluxing

  Spray fluxing is a technology used in electronics assembly to apply flux to the PCB board in the wave soldering process. The flux is needed to deoxydise the surfaces to be soldered. The advantage of spray fluxing is that there is little to no contact of the flux in the system with the air  and the flux quality does not need to be monitored. In most systems the flux is being pumped directly fom the flux drum or from a flux tank through a nozzle where it is mixed with pressurized air to form a spray cone/spray beam. The spray nozzle is moving from left to right while the PCB is transported above it. The goal is to apply a uniform layer of flux over the (bottom side) surface of the PCB as well as in the through holes. The physical construction of the spray nozzle in combination with a certain air pressure will determine the spray cone and spray width . This spray width will determine how fast that the nozzle will have to travel from left to right to get a uniform spray pattern at a given transport speed of the PCB. The transport speed of the PCB is usually determined by the desired throughput but limited by the thermal mass of the PCB. It is always advisable to spray from both sides of the nozzle movement to overcome shadow effects of deep pockets of PCB carriers or SMD components on the bottom side. The air pressure has to be set in this way that the spray cone has enough power to get the flux into the through holes. Too high air pressure however can cause flux being pressed in between the carrier and the PCB where it is shielded from wave contact and it will remain as an unconsumed flux residue on the PCB board. Too high air pressure can also cause components with a loose pin-to-hole ratio components to be displaced and more flux pollution in the machine.  To verify the correct setting for a uniform spray pattern a carton can be used instead of the PCB that will be removed from the machine before the preheating and checked for a uniform discoloration. Systems where the flux nozzle is driven by a (stepper) motor in general are more smooth than systems that use a pneumatic cylinder and give a better chance on a uniform spray pattern.  To find the correct settings for good through hole flux wetting a paper can be applied on top of the non populated PCB board. It will be removed from the machine before the preheating and checked for discoloration on every position where there is a through hole. This methodology however does not test a tight pin-to-hole ratio because the components are not present but in many cases can be a good indication for a correct setting.  The correct flux volume is this volume of flux that gives good soldering results and provides the lowest residue formation. This volume can vary substantially from one PCB board to another. The best way to find this optimal flux volume is by trial and error. A rather high flux volume where the PCB board is visually wet but no flux drips off the board can be used as a starting point. Then the flux volume can be stepwise reduced untill soldering defects appear like bridging, icycling (spikes), webbing,... Then go back to the previous setting that did not show these soldering defects.  The settings for this optimal volume of flux can then be applied to a test PCB that is weighed before and after fluxing. It is advisable to do this several times and calculate an average value.  This value can then be used to do a regular process stability with that test PCB.  Flux nozzles made from stainless steel are preferred to plated nozzles because they have a higher compatibility with water based fluxes. Water based fluxes, in general are more sensitive to the correct spray fluxer settings than alcohol based fluxes.  It is advisabe to use a flux from the 'OR L0' classification that additionnally is absolutely halogen free. These fluxes give the lowest residue formation on the PCB board and provide the highest reliability of the residues remaining on the PCB board.  Furthermore, they give the lowest risk on ICT (In Circuit Test) contact problems, on flux nozzle blocking and are easiest to be cleaned from the machine and carriers.
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  Wave soldering

  Wave soldering is a bulk soldering process used in electronics manufacturing to connect electronic components to a PCB board. The process is typically used for through hole components but can also be used for soldering of some SMD (Suface Mount Device) components that are glued with an SMT (Surface Mount Technology) adhesive to the bottom side of the PCB before passing through the wave soldering process. The wave soldering process comprises three main steps : Fluxing, preheating and soldering. A conveyor transports the PCBs through the machine. The PCBs can be mounted in a frame to avoid adjusting the conveyor width for every different PCB.  Fluxing is usually done by means of a spray fluxer but also foam fluxing and jet fluxing are possible. The liquid flux is applied from the bottomside of the PCB on the surface and in the trough holes. The purpose of the flux is to deoxydize the solderable surfaces of the PCB and components and allow the liquid soldering alloy to make an intermetallic connection with those surfaces resulting in a solder joint.   The preheating has three main functions. The solvent of the flux needs to be evaporated as it loses its function once its has been applied and it can lead to soldering defects like briding and solder balling when it contacts the solder wave in a liquid state. Water based fluxes in general need more preheating to evaporate than alcohol based fluxes. The second function of the preheating is to limit the thermal shock when the PCB contacts with the liquid solder of the solder wave. This can be important for some SMD components and PCB materials. The third function of the preheating is to promote through hole wetting of the solder. Because of the temperature difference between the PCB board and the liquid solder, the liquid solder will be cooled down when going up the through hole. Thermally heavy boards and components can draw away so much heat from the liquid solder that it is cooled down to the solidification point where it freezes before it gets to the top. This is a typical problem when using Sn(Ag)Cu alloys. A good preheating limits the temperature difference between PCB board and liquid solder and hence reduces the cool down of the liquid solder when going up the through hole. This gives a better chance that the  liquid solder will reach the top of the through hole.  In a third step the PCB board is passed over a solder wave. A bath filled with a soldering alloy is heated up to soldering temperature. This soldering temperature depends on the used soldering alloy. The liquid alloy is pumped through channels up into a wave former. There are several types of wave formers. A traditional setup is a chip wave combined with a laminar main wave. The chip wave jets solder in the direction of the PCB movement and allows to solder the back side of SMD components that are shielded of wave contact in the laminar wave by the body of the component itself is. The laminar main wave flows to the front but the adjustable back plate is positioned like this that the board will push the wave into a back flow. This will avoid the PCB being dragged through the reaction products of the soldering. A wave former that is gaining popularity is the Wörthmann-wave that combines the function of the chip wave and the main wave in one wave. This wave is more sensitive to the correct setting and bridging. Because of the fact that lead-free soldering alloys need high working temperatures and tend to oxydise quite strongly, a lot of wave soldering processes are done in a nitrogen atmosphere. A new market tendency and the considered by some as the future of soldering is the use of a low melting point alloy like e.g. LMPA-Q. LMPA-Q needs less temperature and reduces oxydation. It also has some cost related benefits like reduced electricity consumption, reduced wear ot of carriers and no need for nitrogen. It also reduces the thermal impact on electronic components and PCB materials.

Key advantages

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  2 Flux supply modules

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  Encoder calibration function

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  Low level flux alarm

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  Clean, ergonomic design

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  Special flux pump

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  For rosin fluxes

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  Double Venturi, clog-free spray nozzle

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  Retrofits into most fluxing systems

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  Touch screen programming

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  For alcohol-based fluxes

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  For water fluxes