RA 25010

Suitable for

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  Hand soldering

  Hand soldering is a technology in electronics manufacturing that uses a hand (de)soldering iron to make a solder joint or to desolder a component from a PCB board. The process is mostly used in rework and repair but also to solder single components that have been left out of the bulk soldering process (reflow or wave soldering). This can be due to the availability or the temperature sensitivity of these components. The soldering iron usually is part of a soldering station that has a power supply that controls the temperature of the soldering iron. This temperature can be set according to the used soldering alloy and usually is between 320°C-390°C. The soldering iron has an exchangeable soldering tip that can be chosen according to the component to be soldered. For optimal heat transfer the biggest possible soldering tip is recommendable, certainly when soldering (heavy thermal mass) through hole components. For soldering thermally heavy components and boards, the power of the soldering station is also important to keep the set temperature of the soldering tip. In rework and repair, changing the soldering tip for every different component is not realistic and only a few soldering tips are used. Soldering tips exist to solder several surface mount solder joints in a row like for e.g. SOICs (Small Outline Integrated Circuit) and QFPs (Quad Flat Package). To promote heat transfer and flowing of the solder, the soldering tips are wettable, meaning that they make an interaction with the soldering alloy. During soldering these tips will oxidize and they can loose their wettability which will obstruct heat transfer. This can be avoided by cleaning the soldering tip with e.g. a tip tinner. After some time the soldering tips will also wear out and will need to be replaced. The life time of the soldering tip can be optimised by avoiding the use of abrasive or agressive soldering tip cleaners or by avoiding mechanically cleaning the soldering tip with e.g. steel wool or sand paper. The use of an absolutely halogen free tip tinner is advisable.  In hand soldering, the solder for the solder joint is usually provided by a solder wire. A solder wire is available in several diameters and several alloys, and has a certain quantity of a certain type of flux inside.  The alloy is usually the same or a similar alloy as the bulk soldering process (reflow, wave or selective soldering). The diameter is chosen according to the size of the solder joint. The flux content in the solder wire is usually determined by the thermal mass of the component and board to be soldered. (Heavy thermal mass) through hole solder joints need more flux. More flux content will also give more visual flux residue after soldering. Sometimes extra flux is needed which in most cases is a liquid rework and repair flux but also can be a gel flux.  The type of flux/ solder wire is determined by the solderability of the surfaces to be soldered. With normal solderability of electronic components and PCB boards an absolutely halogen free 'L0' type of flux/solder wire is advisable. In general a hand soldering operation is performed like this: Set the temperature of the soldering tip according to the used soldering alloy. For lead-free alloys, the advised working temperature is between 320°C and 390°C. For more dense metals like Nickel, the temperature may be elevated to 420°C. The use of a good soldering station is important. Use a soldering station with a short response time and with enough power for your application. Choose the correct soldering tip: to reduce the thermal resistance, it is important to create a large as possible contact area with the surfaces to be soldered. Heat up both the surfaces simultaneously. Slightly touch with the solder wire, the point where soldering tip and the surfaces to be soldered meet (the small quantity of solder ensures a drastic lowering of the thermal resistance). Add subsequently without interruption, the correct amount of solder close to the soldering tip without touching the tip. This will reduce the risk on flux spitting and premature flux consumption!

Key advantages

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  Increased activity

  Increased activity of a soldering product can be needed for surfaces with poor solderability like e.g. brass, unprotected Ni, Oxidised Ag, Cu that was not micro-etched,...or surfaces with degraded solderability like e.g. I-Sn that was stored too long or did see too much heat, Cu-OSP that passed a lead-free reflow profile too long ago,...An indication of the activity of a soldering product is their classification. The most popular and accepted classification for soldering products is the IPC. L0 is the lowest activation class and the standard, it should be suitable for all normal quality conventional surfaces used in electronics assembly. L1 is the lowest activation class but with a halogen content up to 0,5%. These halogens will in most cases already give a better result on many of the previously mentioned surfaces with poor or degraded solderability. The other activation classes are M0 and M1 and H0 and H1. M stands for Medium and H stands for High. 0 stands for up to 500ppm of halogens for both M0 and H0. 1 stands for up to 2% of halogens for the M1 class and for H1 more than 2% of halogens are allowed. Soldering products of the H class are to be treated with care as they can be corrosive and need to be cleaned off, preferrably in a automatised cleaning process.
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  Increased wetting ability

  The wetting ability of a soldering product refers to how well the activation of the soldering product is able to clean off oxides from the surfaces to be soldered. These oxides need to be removed to enable the liquid soldering alloy to penetrate the surfaces to be soldered. When the quality of the surfaces to be soldered in electronics manufacturing is normal, it is possible to use a soldering product from the lowest activation class L0. In general, only when surfaces are degraded or when the base metal is hard to solder, then a product with a higher activity or increased wetting ability is used. Such surfaces can be for example chemical Sn that was applied too thin or stored too long before soldering, components or PCB boards that were stored too long in hot and humid conditions and are heaviliy oxidised, non protected Ni, brass,... Another possible reason for using a product with increase wetting ability is ease-of-use. For example a solder wire with increased wetting ability in general will provide faster soldering and is not so sensitive to the correct handling required to produce a good hand soldered solder joint. In high volume hand soldering operations for electronc units that have not so high requirements to the residues after soldering, solder wires with increase wetting ability are often used. Also for robot soldering and laser soldering solder wires with increase wetting ability are often used because in general they have better properties for these processes.
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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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  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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  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.