AF 4818-PbF

Suitable for

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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.
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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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  Jet fluxing

  Jet fluxing or microjet fluxing or drop jet fluxing is a technology used in electronics assembly to selectively apply flux to the surfaces to be soldered in the selective soldering process and sometimes also in the wave soldering process. The flux is needed to deoxydise these surfaces. A nozzle shoots tiny drops of flux from a pressurised flux tank to the bottom side of a PCB board. The nozzle can be positioned in an X/Y plane (spot fluxing) or can be moving along a path in the X/Y plane (line fluxing). Usually the PCB is standing still during flux application but some stand alone systems like ICSF Select can apply the flux while the board is moving which can be important in a high volume wave soldering process. The volume of flux can be programmed and depending on the system is expressed in drops/s, Hz,... For spot fluxing the time can be programmed and for line fluxing the speed can be programmed. The goal of the jet fluxer is to apply flux to the surfaces to be soldered which are the surface of the pin of the component and the surface of the trough hole of the PCB. Depending on the size of component and the pin to hole ratio there are several ways to program the fluxer so that the flux will end up on the surfaces to be soldered. This requires some experience. It is also recommendable that no flux will be applied outside the area of contact with soldering nozzle in the soldering process. This flux will see no soldering heat and will be left on the board as an unconsumed flux residue. Depending on the used flux and the sensitivity of the electronic unit, these residues can be critical for the reliability of the electronic unit. In this matter it is important to use a flux from the 'L0' classification that additionnally is absolutely halogen free. Fluxes that are specifically designed for selective soldering like SelectIF 2040 and IF 2005C give the best chance to apply the flux only on the surfaces to be soldered in combination with the best soldering performance. Furthermore it is important that the positioning of the jet fluxer is calibrated on a regular basis to make sure that the nozzle is exactly there where it has been programmed to be. When there is doubt if the jet fluxer is depositing the flux where it is programmed to be deposited, a PCB board can be fluxed without the following preheating and soldering step. When the board exits the machine it can be inspected from the bottom side to verify the correct flux application. A problem that is is sometimes witnessed is blocking of the nozzle by dried up flux residues. Some systems verify if the flux is coming out of the nozzle but others not. In this matter it is advisable to use fluxes from the 'OR' classification, meaning that they do not contain rosin nor resin which are sticky substances that can cause this nozzle blocking. Also a regular cleaning of the nozzle is advisable. If a flux filter is present in the system, check that filter for obstruction on a regular basis. Do not increase flux tank pressure to solve a nozzle blocking problem.

Key advantages

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  Rosin based (colophony)

  Rosin also known as colophony is a natural product coming from trees. There are many kinds of rosins with very different properties but some general properties apply.  As a part of soldering chemistry, like soldering fluxes, solder pastes and solder wires, in general, rosin provides a large process window in the soldering process. This means that in general it is able to withstand longer times and higher temperatures than e.g. a resin.  An advantage of the rosin in a liquid flux is that in general it tends to leave less solder balls on the solder mask after wave or selective soldering. Furthermore the rosin residue will give a certain protection against atmospheric moisture. This can provide an extra chance to pass climatic reliability tests. This protection capacity however degrades in time.  On the other hand, rosin contained in a liquid soldering flux can also have some disadvantages. It increases the risk on blocking the spray nozzle or jet nozzle of wave and selective soldering machines. The residues left in the machine and on carriers are quite hard to clean off. Residues left on the PCB board can interfere with electrical pin testing (ICT, In Circuit Testing) and create a contactproblem causing a false reading/false error. In some cases this can lead to obstruction of the production flow. When some of the rosin containing flux spray accidentally ends up on contacts of e.g. a connector, a switch/relay/contactor with a partial open housing or on carbon contacts or on contact pattern on the PCB, this can also lead to contact problems. Rosin residues in general have poor compatibility with conformal coatings. After thermal cycling the conformal coating can start showing cracks where atmospheric moisture can penetrate and condensate. Considering all the above, weighing the advantages of rosin in liquid soldering fluxes against the disadvantages, there is an ongoing tendency to chose for liquid fluxes without rosin. 'OR' classified fluxes do not contain rosin.  Rosin is very often used in solder wire because of its wide process window in time and temperature.  The disadvantage is that rosin tends to discolor with temperature and leave visually heavy residues. When the solder wire is used for reworking electronic PCB boards, this residue is for some electronic manufacturers non desirable, as they do not like their customers to see that rework has been done on a PCB. Cleaning of these rosin residues requires special cleaning agents and is a time consuming process. In this case manufacturers can chose for an RE classified solder wire like IF 14. The residues are minimal and can be brushed away with a dry brush. Rosin is also used in solder pastes. Beside giving a good process window in time and temperature, it also provides a good stability of the solder paste on the stencil. This will facilitate a stable printing process and hence stable soldering results and defect rates. The discoloration of the rosin in reflow soldering is not so prominent as it is with a solder wire because the temperatures in reflow soldering are lower than in hand soldering. Still the rosin residue has poor compatibility with conformal coating and in time after thermal cycles it might show cracks or detatching of the conformal coating. Although most manufacturers will apply the conformal coating over the solder paste residues, for optimal results it is advisable to clean off the solder paste residues. Giving the benefits of colophony described above, most solder pastes contain colophony.
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  Large process window in time and temperature

  A large process window in time and temperature is usually needed when soldering components and PCBs (Printed Circuit Boards) with heavy thermal mass. These boards and components require a lot of heat to get them to soldering temperatures. This takes time and in some soldering process also requires elevated temperatures. The soldering chemistry will have to withstand/survive these increased times and elevated temperaures.  The biggest challenge is soldering heavy thermal mass through hole components on a heavy thermal mass PCB. On a through hole the required heat for soldering is needed on both sides of the board. This heat is usually applied only from one side and will have to pass through the board to the other side. If the PCB board has many Cu-layers, thick Cu-layers, and layers that are fully connected to the through hole barrel, a lot of heat will be deviated to the side and more heat will have to be applied to the board to get enough heat on the other side. In some processes the heat is applied from both sides of the board in a preheating. This will facilitate trough hole soldering on these thermally heavy electronic units.  However if there are temperature sensitive components present on the side where the preheating is applied, care must be taken not to overheat and (pre)damage those components
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  High temperature resistant

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  Absolutely halogen free

  Absolutely halogen free soldering chemistry contains no intentionally added halogens nor halides. The IPC classification allows up to 500ppm of halogens for the lowest 'L0' classification. Soldering fluxes, solder pastes and solder wires from this class are often referred to as 'halogen free'. Absolutely halogen free soldering chemistry goes one step further and does not contain this 'allowed' level of halogens. Specifically in combination with lead-free soldering alloys and on sensitive electronic applications, these low levels of halogens have been reported to cause reliability problems like e.g. too high leakage currents.  Halogens are elements from the periodic table like Cl, Br, F and I. They have the physical property that they like to react. This is very interesting from the point of view of soldering chemistry because it is intended to clean off oxides from the surfaces to be soldered. And indeed halogens perform that job very well, even hard to clean surfaces like brass, Zn, Ni,...or heavily oxidized surfaces or degraded I-Sn and OSP (Organic Surface Protection) can be soldered with the aid of halogenated fluxes. Halogens provide a great process window in solderability. The problem however is that the residues and reaction products of halogenated fluxes can be problematic for electronic circuits. They usually have high hygroscopicity and high water solubility and give an increased risk on electro migration and high leakage currents. This means a high risk on malfunctioning of the electronic circuit. Specifically with lead-free soldering alloys there are more reports that even the smallest levels of halogens can be problematic for sensitive electronic applications. Sensitive electronic applications are typically high resistance circuits, measuring circuits, high frequency circuits, sensors,...That's why the tendency is to move away from halogens in soldering chemistry in electronics manufacturing. In general when the solderability of the surfaces to be soldered from component and PCB (Printed Circuit Board) are normal, there is no need for these halogens. Smartly designed absolutely halogen free soldering products will provide a large enough process window to clean the surfaces and get a good soldering result and this in combination with high reliability residues. 
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  Reduced solder ball formation

  Solder balls are small balls of soldering alloy that remain on the solder mask of the PCB (Printed Circuit Board) after wave, selective or reflow soldering. They are non desirable but often present. They are usually caused by more parameters. In wave soldering the biggest parameter is the solder mask. The tendency of a solder mask to 'generate' solder balls depends on its surface structure which is a property of the solder mask itself. Furthermore the correct curing parameters of the solder mask in PCB (Printed Circuit Board) manufacturing needs to be respected. Poor curing may result in more solder balls. A second parameter is the flux. Some fluxes have more tendency to solderballing than others. In general, the higher solid content fluxes and fluxes from the 'RO'- classification generate less solder balls. Water based fluxes in general generate more solder balls than alcohol based fluxes but special versions of water based fluxes exist that provide lower solder balling than alcohol based fluxes like PacIFic 2009MLF and PacIF 2009MLF-E. In the process it is important to have correct flux application setting in combination with the right preheating setting to minimise solder balling. Too much flux, or flux that has been pushed in between the carrier and the PCB can be hard to dry off in the preheating and can generate solder balls upon wave contact. Too low preheating settings in this matter can also be problematic, certainly with water based fluxes. A hot air convection preheating can help to evaporate flux solvents. Another parameters is the solder wave. Turbulent waves generate more solder balls. Turbulence can be caused by the type of wave former itself (like e.g. a chip wave or a Wörthmannwave) or by bad settings or dross pollution in the wave former. The physical construction of the PCB board and carrier can also create extra turbulence. PCBs with a lot of components on the solder side and carriers with small and deep pockets will create extra turbulence. In selective soldering also the solder mask is the main parameter for solder balls and the differences between fluxes are similar to wave soldering. In this process the miniwave itself is turbulent and often is used to solder connectors who create an extra turbulence. This results in the fact that in general the selective soldering process is even more sensitive to solderballs than wave soldering. In reflow soldering, the main cause of solder balls is the solder paste printing process. If solder paste ends up outside the wettable solder pads this can result in solder balls after reflow. The reason for this can be numerous: The horizontal positioning of the PCB (Printed Circuit Board) underneath the stencil was not correct, the vertical alignment of PCB and stencil was not correct (not parallel). The pressure of the PCB against the stencil was not high enough, the squeegee pressure was too high, the printing speed was too low, there was no stencil aperture reduction, there was a deviation in the PCB, the temperature in production was too high (>30°C), accumulating residues due to too long intervals for stencil cleaning, a solder paste that slumps after printing, An oxidized solder paste,... Some solder pastes can be more sensitive to generate solder balls when they are outside the wettable pad than others. Another cause of solder balling can be the Pick and Place unit. When the vertical force when placing the component is too high, this can result in the paste being squashed and ending up outside of the wettable pad. Unfortunately, not all Pick and Place machines are easily adjustable in this matter. The soldering profile might als contribute to solderballs. Soak zones between 100-150°C are known to cause some solder pastes to slump and end up outside of the pad. This however can be very different from one solder paste to another. Vapor phase ovens in general are also a bit more sensitive to create solder balls as the liquid that condensates on the vapor can cause the solder paste to slump. Also here, there can be quite a big difference between one solder paste and the other. Another phenomenon where a solder ball is sticking to the side of a chip component is called solder beading or mid chip solder balling. This is mainly caused by too much solder paste and the non wettable part of the component lead that is contacting with the solder paste. The excessive solder paste will remain as a solder ball sticking to the side of the chip component. A thinner stencil, a higher stencil aperture reduction and a special stencil aperture design are used to solve the problem of solder beading.
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  For both SnPb and lead-free processes

  In 2006 legislation restricted the use of lead (Pb) in electronics manufacturing.  However there were a lot of exemptions formulated, mainly due to the lack of long time reliablity experience with the lead-free alloys. This resulted in a lot of electronics manufacturing sites that were using both lead-free and Pb containing alloys in their soldering processes. For wave and selective soldering, a lot of electronic manufacturers desired the use of  the same flux chemistry with both types of soldering alloys. This was because they were familiar with the chemistry in terms of reliability. Also introducing new materials in a manufacturing can require a lot of paper work, extra storage capacity, etc...Although the lead-free alloys require higher operating temperatures than the Pb-containing alloys, by increasing the applied flux quantity in a lot of cases the same flux chemistry can be used for both alloys. However in some cases, usually when soldering electronic units with high thermal mass, it is not possible to use the same flux for both soldering alloys. In these cases, usually a flux with higher solid content is needed. A lot of solder wires and solder pastes are available with the same flux for both lead-free and SnPb-alloys.
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  Alcohol based (VOC)

  Alcohol based soldering fluxes are liquid fluxes  that have alcohol(s) as their principal solvent(s). The majority of liquid fluxes used in electronics manufacturing are still alcohol based. The main reasons are their historical use and hence market share and their in general larger process window compared to water based fluxes. Water based fluxes have numerous advantages to alcohol based fluxes, like lower consumption, no VOC (Volatile Organic Compound)-emmissions, no fire hazard, no need for special transport and storage, lower smell in the production area,...However a lot of electronic manufacturers seem to prefer the larger process window of alcohol based fluxes to the advantages of water based fluxes. Alcohol based fluxes in general are less sensitive to the correct spray fluxer settings to get a good flux application on the surface and in the through holes. Furthermore they are more easily evaporated in the preheating and give less risk on remaining solvent drops creating solder balls, solder splashes or bridging upon wave contact. Another parameter that is complicating the implementation of water based fluxes is that changing a flux in some cases can be a time consuming and costly process. It usually involves homologation testing and approval of end customers. Specifically for EMS (Electronic Manufacturing Servivces = subcontractors) this can be a challenge. Some countries have already implemented legislation that limits the VOC-emission of factory chimneys or imposes taxes on VOC emissions. This appears to be an extra incentive to change to water based fluxes. A recent development forced a lot of manufacturers to look into water based fluxes. The COVID-pandemia in the beginning of 2020, suddenly increased the demand for alcohol based desinfectants to that extent that at a certain moment the availability of alcohols on the market was pretty much non existing. Luckily the industry that produces alcohols was able to ramp up their volumes just in time to avoid electronic manufacturers to fall without fluxes to operate their soldering machines.
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  No-clean - no post cleaning needed

  When a soldering product is labelled No-clean, this means that  soldering product has passed reliability testing like a Surface Insulation Resistance(SIR) test or an electro(chemical) migration test. These tests are designed to test the hygroscopic properties of the residues of the soldering product under elevated temperature and high relative moisture conditions. No-clean is an indication that the residues can remain on the electronic unit after the soldering process without being cleaned. This will apply for by far most of the electronic applications. For very sensitive electronic applications, which are typically high resistance electronic circuits, high frequency electronic circuits, etc... it is possible that cleaning of the electronic unit is necessary. It is always the responsibility of the electronic manufacturer to judge wether cleaning is necessary or not.
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  RoHS compliant

  RoHS stands for Restriction of Hazard Substances. It is a European directive: Directive 2002/95/EC. It restricts the use of some substances that are considered Substances of Very High Concern (SHVC) in electrical and electronic equipment for the territory of the European Union. A listing of these substances can be found below: Please note that this info is subject to change. Always check the website of the European Union for most recent information: https://ec.europa.eu/environment/topics/waste-and-recycling/rohs-directive_nl https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32011L0065 1. Cadmium and cadmium compounds  2. Lead and lead compounds  3. Mercury and mercury compounds(Hg)  4. Hexavalent chromium compounds(Cr)  5. Polychlorinated biphenyls (PCB)  6. Polychlorinated naphthalenes (PCN)  7. Chlorinated paraffins (CP)  8. Other chlorinated organic compounds  9. Polybrominated biphenyls (PBB)  10. Polybrominated diphenylethers (PBDE) 11. Other brominated organic compounds  12. Organic tin compounds (Tributyl tin compounds, Triphenyl tin compounds)  13. Asbestos  14. Azo compounds  15. Formaldehyde  16. Polyvinyl chloride (PVC) and PVC blends  17. Decabrominated diphenyl ester (from 1/7/08)  18. PFOS : EU directive 76/769/EEC (not allowed in a concentration equal to or higher than 0.0005% by mass) 19. Bis(2-ethylhexyl) phthalate (DEHP)  20. Butyl benzyl phthalate (BBP)  21. Dibutyl phthalate (DBP)  22. Diisobutyl phthalate 23. Deca brominated diphenyl ester (in electrical and electronic equipment) Other countries outside of the European Union have introduced their own RoHS legislation, which is to a great extent very similar to the European RoHS. 

Physical & chemical properties

Compliance

RO L0 to EN and IPC standards

Solid content

5%

Halide content

0,00%

Documents

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  TD AF 4818 PbF (PDF)

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