IF 2005M

No-Residue™ soldering flux

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.
Dip soldering is a technology used to solder surfaces by dipping/immersing them in liquid solder. It is mainly used for wires and cables and also for the leads of some electronic and mechanical components. Dip soldering applies a layer of solder on the surface that will provide a good solderability for the following soldering processes. The solderability of this layer is maintained very well during storage. Dip soldering can also be used in rework and repair of a PCB (Printed Circuit Board) to e.g. remove or resolder a through hole connector. The dipping process can be done manually or by an automated process. Before soldering the lead or wire is dipped in a soldering flux. To avoid flux residues after soldering, the dipping depth in the flux is usually lower or just as deep as the dipping depth in the solder. Depending on the solderability of the surfaces to be pre-tinned, different fluxes can be used. For surfaces that are hard to solder, like Ni, Zn, brass, heavily oxidized Cu,...usually water soluble fluxes are being used. They provide excellent solderability but can be and must be cleaned in a water based washing process afterwards, as the residues of these fluxes might create problems (like e.g. corrosion). For surfaces with normal solderability IF 2005C or PacIFic 2009M can be used. The soldering alloy in most cases is Sn(Ag)Cu based. The temperature of the soldering alloy is usually higher than for wave and selective soldering because this speeds up the process and the risk on damaging components is very limited. It is also possible that the dipping process needs to remove/burn off the coating of the Cu-wire to be tinned, this also requires higher temperatures. In general soldering temperatures vary from 300-450°C. These temperatures will oxydise the surface of the solder bath quite strongly. The use of Anti-Oxydant pellets can compensate for this oxydation. Some solder baths mechanically remove the top layer of the solder bath with a scraper just before the component is dipped into the solder. Dipping times very much depend on the thermal mass of the component to be soldered and usually are from 0,5s to 3s.
Selective soldering is a soldering technology in electronics manufacturing, typically used for PCB designs with mainly SMD (Surface Mount Device) components for reflow soldering and only a few through hole components that cannot pass through the reflow soldering process. These are usually thermally heavy mass components like e.g. big transfo's or thermally sensitive components like e.g. film capacitors, displays, connectors with sensitive plastic bodies, relays, etc... The selective soldering process allows to solder these through hole components without protecting or affecting the SMD components on the bottom side of the PCB. The selective soldering process is very flexible as the parameters can be programmed for each solder joint separately. The main limitation of the process however is the throughput or the production capacity. This can be considerately improved when using a low melting point alloy that allows for faster soldering speeds increasing production capacity up to 100% (double). The process starts with the application of a liquid flux that will deoxydize the surfaces to be soldered. This flux is applied by a micro jet or drop jet fluxer that shoots little drops. The correct calibration and programming of this fluxer is essential to get good soldering results. A common mistake is that flux is applied outside of the contact area of the soldering nozzle. This flux will remain as an unconsumed flux residue. For some fluxes and sensitive electronic circuits this can lead to increased leakage currents and failure in the field. It is advisable to use fluxes that are specifically designed for selective soldering and that are absolutely halogen free. The IPC classification for fluxes allows up to 500ppm of halogens for the lowest activitiona class but also these 500ppm can be critical, so absolutely halogen free is the key word. The next step in the process is preheating. This process step evaporates the solvents of the flux and provides heat to support good through hole wetting of the solder. Soldering is a thermal process and a certain amount of heat is needed to make a solder joint. This heat is needed from the bottom as well as from the top of the through hole component to be soldered. This heat can be provided by the preheating and by the liquid soldering alloy. Some basic machines do not have preheating, they will have to apply all heat through the liquid soldering alloy and in general they use higher temperatures for soldering. A preheating unit is usually a short wave IR (infrared) unit that applies the heat from the bottom side of the PCB. In most cases, the time and power of the preheating can be programmed. For thermally heavy boards and applications, top side preheatings exist. Usually they are hot air (convection) units where the teperature of the air can be programmed. When using this unit, it is important to know if there are any temperature sensitive components on the top side of the board that might be affected by this preheating. Several systems for soldering exist. The one where the PCB board is standing still and only the soldering nozzle is moving is definitely preferred as all G-forces should be avoided when the solder solidifies. In the soldering step, a liquid soldering alloy is pumped through a soldering nozzle.There are different nozzle sizes and shapes available, wide nozzles, small nozzles, long nozzles and short nozzles. Depending on the components to be soldered, one is preferred to another. In general wider nozzles and shorter nozzles give better heat transfer and are preferred. Smaller and longer nozzles can be used for situations with limited accessibility. Wettable nozzless are preferred to non wettable nozzles as they give a much more uniform flowing of the solder and more stable soldering results. Nitrogen flooding of the nozzle is advisable to have a stable flowing of the solder. The nitrogen is preferrably preheated because when not, it will cool down the solder and the PCB. The optimisation of the soldering program is essential for optimisation of the throughput/capacity of the selective soldering machine. This will focus on finding the minimal times and maximal speeds that give good through hole wetting in combination with no bridging.
Foam 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 technology has mainly been replaced by spray fluxing but does offer some advantages. It provides good and equal flux wetting of the PCB and through holes and it is a simple and cheap unit with no moving parts. The disadvantages are that the applied flux volume cannot be varied and is always maximal. Furthermore it is an open system with evaporation of the flux solvent and potential absorption of water from the air (typical for alcohol based fluxes) that requires monitoring of the solid content or density of the flux and adjusting with flux thinner. Also pollution from the boards that pass through the flux can affect the foaming ability and properties of the flux. A foam stone with very fine holes (~10-20µm) is mounted in a nozzle which is submerged in flux. Pressurised air is pushed through the foam stone to create a foam that will move up the nozzle. The PCB board is transported through the foam that exits the nozzle. The foam will fall back into the flux tank. The flux tank and nozzle are usually made out of stainless steel but can also be made out of a solvent resistent plastic like HDPE. Some important parameters are: The pressurised air needs to be free from water and oil, an oil and water separator are required. The length of the foam stone is preferrably as big as the nozzle to get an equal foam formation across the nozzle. It is advisable that the top of the foam stone is kept submerged at least 3 cm underneath the flux surface. To keep the flux level in the tank stable, some systems will use an overflow system where the flux will be pumped around and in some cases is filtered. Avoid that foam stone will make contact with the air as flux residues can dry and block the holes. If that happens, the foam stone needs to be cleaned in a solvent or be replaced. The flux nozzle opening is preferrably 8-10mm. Adjust the air pressure until a smooth foam formation is achieved. The contact of the foam with the PCB can be checked with a glass plate. With this glass plate also the setting of the air knife can be checked. The air knife is a tube with drilled holes that are preferrably 1 mm in diameter and 5mm apart from eachother. This will create an even air curtain with pressurised air. The air knife is mounted behind the foam fluxer under an angle so that the air curtain will blow off excessive flux from the PCB that will fall back into the flux tank. On the glass plate no dry stripes may be formed. If this is the case the air pressure on the air knife needs to be reduced. No flux drops may fall off the glass plate after that it has passed the air knife. If this is the case the air pressure on the air knife needs to be increased. Most water based fluxes are not suitable for foaming. PacIFic 2010F is a water based flux specifically designed for foaming.
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.
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

No-residue ™ is a soldering flux technology that is designed in this way that everything can evaporate in the soldering process, so that no flux residues are left after soldering. This results in extremely clean boards with very high compatibility with ICT testing and conformal coating. In practice, it is possible that due to other variables in the process, like the PCB solder mask, the carrier, the components, solder paste or solder wire residues, the solder wave,...some residue will be present after soldering. In any case, a No-residue ™ soldering flux will give the lowest risk on residue formation after soldering.
Colophony, also called rosin, is a substance derived from trees that is typically used in soldering fluxes. It can be used in liquid fluxes as well as in gel fluxes. Colophony containing fluxes can be identified by the denomination 'RO' in the IPC classification. Colophony in general provides a good process window in time and temperature but has a number of disadvantages depending on the application that the colophony containing flux is used in. In liquid fluxes for wave and selective soldering, the colophony will give an increased risk on blocking the nozzle of spray and micro jet flux application systems, resulting in more maintenance and higher risk on bad soldering results. The residues of a rosin (=colophony) based flux in the soldering machine and on tools and carriers are quite hard to remove and a solvent based cleaner is usually needed. When the flux with colophony accidentally ends up on the contacts of a connector or contact comb structures like for a remote control or in electro mechanical contactors / relays / switches, it is known to give contact problems and malfunctioning of the electronic unit in the field. Furthermore the residues of the flux that remain on the board can give contact problems with electrical pin testing ( ICT= In Circuit Testing) which can result in delays in production because of false errors. This usually requires cleaning of the PCB and/or the test pins. These expensive test pins are rather fragile and sensitive to be damaged by cleaning. Furthermore the residues of a rosin flux are known not to be compatible with conformal coatings in time. The rosin residue forms a separation layer between the PCB and conformal coating that in time can cause detaching of the conformal coating and also cracking, especially when the electonic unit experiences a lot of temperature cycles (warming up and cooling down). For those reasons fluxes without colophony and more specifically fluxes from the 'OR' classification are generally used for wave and selective soldering. Colophony can also be used in solder wires. Although the colophony provides a good process window in time and temperature, it is very sensitive to discoloration when heated. The discoloration will depend on the type of colophony and the temperature it has seen. As soldering tip temperatures are usually quite high, the colophony in the solder wire will give quite heavy visual residue formation around the solder joints. This will distinguish them from the other solder joints made in reflow, wave and selective soldering. When this is not desirable a cleaning operation needs to be performed. Furthermore the fumes of a colophony containing solder wire are considered hazardous. A fume extraction is mandatory but anyway advisable for any hand soldering operation. Colophony containg wires are still being used quite a lot but colophony free solder wires and more specifically solder wires from the 'RE' classification are gaining importance. Colophony 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.
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.
ICT stands for In Circuit Testing. It is an electrical test method for electronic circuit boards after assembly and soldering. It uses test pins to contact with the PCB board and measure the presence and the correct electrical value of electronic components. A common problem in this process is bad contacts caused by residues of the soldering flux, the solder paste, the solder mask or other substances. This will cause a false error, meaning that a problem is reported where there is no problem. This can result in serious obstructions in the production flow of an electronics assembly.The problem is more prominent when measuring small resistors and with small test pads. Some soldering fluxes contain substances that leave a uniform layer, they can cause a bad contact or can assemble on the test pins and after a while give a bad contact. The cleaning of those test pins needs to be done carefully as they are fragile and expensive. In this matter, it is important to avoid the use of soldering fluxing that contain substances that might create these residues. Usually they are classified as 'RO' or 'RE' according IPC, meaning they contain a natural rosin or a synthetic resin. 'OR' classified fluxes are preferred. Solder pastes are virtually always classified as 'RO' or 'RE'. They need a rosin (colophony) or resin because of their required consistency for stencil printing. This means that they will always leave a residue that can interfere with electrical testing. If and how much they will interfere depends a lot from the solder paste itself. There can be noticeable differences between one solder paste and another.
A conformal coating is a protection layer often used on electronics devices that are submitted to harsh atmospheres. In most cases the conformal coating is applied on the electronic unit without previous cleaning. Some residues of the soldering process and the soldering products can have a negative effect on the long term adhesion of the protection layer on the electronic unit. This will usually result in small cracks where atmospheric moisture can penetrate and condensate, potentially resulting in increased leakage currents or (chemical) electro migration. However some soldering products have a high compatability with conformal coatings. Soldering products that leave little residues and are classified as 'OR' usually have a high compatibility with conformal coatings.
A brushable residue left by a soldering product can be moved with a dry brush without the aid of a solvent. Most residues of soldering products can only be moved by dissolving them with a suitable solvent or cleaning liquid. The advantage of a brushable residue is that the cleaning operation is much quicker and easier. This quality is very much appreciated in visual control and rework and repair after the soldering process in electronics manufacturing.
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.
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.
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.
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.