Anti-Oxidant Pellets

Suitable for

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  Solder bath conditioning

  Solder bath conditioning is used for wave soldering solder baths or dip soldering/pre-tinning solder baths that are operating under atmospheric conditions (no closed nitrogen systems). The solder bath conditioning uses Anti-Oxydant pellets to prevent oxidation during operation of the solder bath and a de-oxidation oil to reduce the amount of dross that has been generated. This will result in a cleaner solder bath with better heat transfer and hence faster soldering. Solder bath conditioning will also reduce the risk on oxides ending up on the PCB board where they might create problems like micro bridging. Furthermore the solder consumption will be reduced drastically.  For solder baths up to 300°C, 1 pellet per kg of solder in the solder bath is added . When fresh solder is added to the bath, also 1 pellet per kg of added solder is added. For solder baths from 300°C-500°C, the dosage is 2 pellets per kg of solder in the solder bath/fresh addedd solder. For the de-oxidation oil following steps are done: For safety reasons, wear mouth mask, protective gloves and clothing. Gather the dross on one side of the machine. Poor a spoon of IF910 on the dross. Mix with two stainless steel spatulas until a black powder is formed. Remove the black powder. Repeat when necessary.
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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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  Pre-tinning

  Pre-tinning is a soldering technolgy used for wires and cables and also for the leads of some electronic and mechanical components. Pre-tinning 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. Pre-tinning is usually done by dipping the surface to be soldered in liquid solder, that usually is a lead-free Sn(Ag)Cu alloy. Some systems use a small wave of liquid solder or a nozzle that jets liquid solder to do the pre-tinning. The pre-tinning process can be done manually but in most cases is done in 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 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.
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  Rework & repair

  Rework and repair on an electronic unit can be performed on defective electronic units that return from the field but can also be necessary in an electronic production environment to correct defects in the assembly and soldering processes. Typical rework and repair actions involve the removal of solder bridging, adding of solder to poor through hole filled components or adding missing solder, replacing wrong components, replacing components that are placed in the wrong direction, replacing components that have defects related to the high soldering temperatures in the processes, adding components that were left out of the process due to e.g. availability or temperature sensitivity. The identification of these defects can be done by visual inspection, by AOI (Automated Optical Inspection), by ICT (In Circuit Testing, electrical testing) or by CAT (Computer Aided Testing, functional testing). A lot of repair operations can be done with a hand soldering station that has a (de)soldering iron with temperature setting. Solder is added by means of a solder wire that is available in several alloys and diameters and contains a flux inside. In some cases a liquid repair flux and/or a gel flux are used to make the hand soldering process easier. For bigger componnets, like BGAs (Ball Grid Array), LGA's (Land Grid Array) QFNs (Quad Flat No Leads), QFPs (Quad Flat Package), PLCCs( Plastic Leaded Chip Carrier),...a repair unit can be used that simulates a reflow profile. These repair units are available in different sizes and with different options. In most cases they contan a preheating from the bottom side that is usually IR (Infrared). This preheating can be controlled by a thermocouple that is placed on the PCB. Some units have a pick and place unit that facilitates the correct positioning of the component on the PCB. The heating unit is usually hot air or IR or a combination of these two. With the aid of thermocouples on the PCB, the heater is controlled to create the desired soldering profile. In some cases the challenge is to bring the component to soldering temperatures without remelting adjacent components. This can be difficult when the component to be repaired is big and has small components near to it. For BGAs with balls made of a soldering alloy, a gel flux can be used or a liquid flux with higher solid content. In this case the solder for the solder joint is provided by the balls. But also the use of a solder paste is possible. The solder paste can be printed on the leads of the component or on the PCB. This requires a different stencil for each different component. The BGA can also be dipped in a special dipping solder paste that first is printed in a layer with a stencil with one large aperture and a certain thickness. For QFNs, LGAs QFNs, QFPs, PLCCs,...solder needs to be added to make a solder joint. In some cases QFPs can be hand soldered but the technique requires experience so the use of a rework unit is preferred. QFPs and PLCCs have leads and can be used with a dipping solder paste. QFNs, LGA's QFNs who do not have leads but flat contacts cannot be used with a dipping solder paste dipped because their bodies would contact the solder paste. In this case the solder paste needs to be printed on the contacts or on teh PCB. In general it is easier to print solder paste on the component than on the PCB, especially when a so-called 3D stencil is used that has a cavity where the position of the component is fixed. Replacing through hole components can be done with a hand (de)soldering station. This is usually done by placing a hollow desoldering tip over the bottomside of the component lead that can suck away solder from the hole. The desoldering tip will have to heat all the solder in the through hole until it is fully liquid. For thermally heavy boards this can be very difficult. In this case, also the top side of the solder joint can be heated with a soldering iron.  Alternatively the board can be preheated over a preheating before the desoldering operation. Soldering the through hole component is usually done with a solder wire that contains more flux or alternatively extra rework flux is added to the through hole and/or on the component lead. For larger through hole connectors, a dip soldering bath can be used to remove the connector. If accessibilty on the PCB is limited a nozzle with its size adapted to the connector can be used. The use of flux in this operation is recommended.

Key advantages

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  Available in lead-free alloys

  Lead-free alloys are soldering alloys without Pb used to connect electronic components to PCB (Printed Circuit Board) boards in electronics manufacturing. In 2006 legislation restricted the use of lead (Pb) because of the risk that end-of-life electronics in land fills would pollute ground water and Pb would be introduced in the eco-system. When Pb is taken in by the human body, it is very hard to be removed and it is known to cause all kinds of (long term) health issues. In 2006 the use of lead (Pb) was restricted by legislation. For that reason, the industry was forced to look into alternatives without Pb. In the end, the industry standardised on Sn(Ag)Cu based soldering alloys. These alloys provided acceptable useability in the existing soldering processes in combination with sufficient mechanical reliabilty of the solder joints and good thermal and electrical properties. The main disadvantage of Sn(Ag)Cu alloys is their quite high melting points (or melting ranges) that result in quite high operating temperatures. This induces thermo-mechanical stress on the electronic unit in the soldering processes that can result in damage or predamage of some temperature sensitive PCB materials and components. Typical soldering temperatures in wave soldering are 250-280°C, in selective soldering 260-330°C and measured  peakT° in reflow 235-250°C. The most popular alloy is the Sn96,5Ag3Cu0,5 alloy with melting temperature around 217°C, often referred to as SAC305. Other versions are SnAg4Cu0,5, SnAg3,8Cu0,7, SnAg3,9Cu0,6,...The differences in melting point between these alloys and the differences in terms of mechanical, electrical and thermal properties are for most electronic applications and soldering processes non significant. Because of cost reasons, the one with lowest Ag-content has the preference and that is the SAC 305. Also because of cost reasons, there is a trend towards low Ag SnAgCu alloys like e.g. Sn99Ag0,3Cu0,7, Sn98,5Ag0,8Cu0,7,... often referred to as low SAC alloys. These alloys have a melting range in between 217°-227°C. This in most cases will require higher working temperatures in the soldering processes up to 10°C, which for some temperature sensitive components can be significant. The mechanical, electrical and thermal properties of the low SAC alloys differ a bit more from the standard SAC alloys. In general they have a lower thermal cycling (fatigue) resistance but for most electronics applications this is not significant. The required 10°C higher working temperature however is often a problem in reflow soldering because most electronic units will have one or more temperature sensitive components. Furthermore, in general SMD (Surface Mount Device) solder joints are weaker than through hole soldered solder joints and SAC alloys in general have rather poor thermal cycling resistance, specifically on thin solder joints. Considering all these paremeters, in most cases the choice will be made for the standard SAC alloys and not the low SAC alloys for reflow soldering. For wave soldering the story is a bit different. The wave solder bath with a lead-free soldering alloy generates quite a lot of oxides becuase of its high working temperature. This is why a lot of manufacturers chose for closed nitrogen machines. This however requires investment in infrastructure which not every manufacturer is willing or able to do. The oxides generated, in genral are being sold back to the manufacturer of the soldering alloy where they are being recycled. The total cost for the electronics manufacturer in this matter is quite high, cetainly with the high Ag soldering alloys like SAC305. That's why there is a tendency towards the use of low SAC and even SnCu alloys (without Ag). Also here the higher melting point will require an increase in operating temperature to get acceptable through hole filling. As in most cases the heat is applied from the bottom side and to the leads of the components, the temperature sensitive components on top of the board in general do not suffer too much from this. In terms of mechanical reliability of the low SAC and  SnCu alloy, this is less an issue because through hole soldered solder joints in general are much stronger than SMD joints. When (glued) SMD components are wave soldered on the bottom side of the PCB this can be different. Also when thermally heavy applications need to be soldered, the higher melting points can give a problem with good through hole fill and cases are known where the working temperature had to be raised so much that PCB material and some components from the top side were damaged. In those cases a low melting point soldering alloy is a good solution. Low melting point alloys that are SnBi based were never considered a viable alternative in the changeover from Pb containing to Pb free alloys because of there incompatibility with Pb and in the transition phase where still a lot of components and PCB materials contained Pb, it was impossible to use them. However since a couple of years the industry is starting reconsider the low melting point alloys because they have a lot of advantages and the risk on Pb contaminationhas become extremely low. A low melting point soldering alloy like e.g. LMPA-Q requires much lower operating temperatures than the standard lead-free soldering alloys. In reflow soldering it requires a peak T° of 190°C-210°C, in wave soldering the bath temperature typically is 220°C-230°C and in selective soldering, the working temperature typically is 240°C-250°C. This substantially reduces the risk of damaging temperature sensitive components and PCB materials and even facilitates the use of cheaper components and materials that are temperature sensitive. In reflow soldering the low melting point alloy also gives lower voiding on BTCs (Bottom Terminated Components). In general low melting point alloys have lower than 10% voiding where lead-free SAC alloys typically have 20-30% of voiding. In wave soldering the low melting point alloy allows for faster production speeds up to 70% and in selective soldering where the soldering of connectors can be done up to 50mm/s the total process time can be reduced by half, increasing the machine capacity with 100%. Furthermore the low melting point alloy does not have problems with good through hole fill on thermally heavy components. The use of nitrogen for wave and reflow soldering is possible but not required. The thermal, electrical and mechanical properties of the LMPA-Q low melting point alloy are sufficient for most electronic applications. Given all these advantages, many see the low melting point alloys as the future of electronics manufacturing.
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  Available in lead-based alloys

  Lead-based alloys are the traditional SnPb(Ag) based alloys that were used to connect electronic components to PCB (Printed Circuit Board) boards in electronics manufacturing before 2006. In 2006 legislation restricted the use of lead (Pb) because of the risk that end-of-life electronics in land fills would pollute groundwater and Pb would be introduced in the ecosystem. When Pb is taken in by the human body, it is very hard to be removed and it is known to cause all kinds of (long term) health issues. For this reason electronics manufacturing introduced lead-free soldering alloys. As the long term reliability of the lead-free alloys was at that point (2006) not yet established, some critical branches of the electronics industry like e.g. automotive, railway,medical, military,... were allowed to temporarily continue using the SnPb(Ag) alloys. But also in these branches the use of lead-based alloys is gradually being phased out. The most typical alloys for wave soldering were Sn60Pb40 and Sn63Pb37 with melting point around 183°C. This facilitated operating temperatures around 250°C. The oxydation behavior of the alloys was considered acceptable and the use of a closed nitrogen atmosphere like for lead-free alloys was not necessary. For reflow soldering, the most typical alloy was Sn62Pb36Ag2 with melting point around 179°C. The addition of Ag gives extra mechanical reliability to the SMD (Surface Mount Device) solder joints who are typically less strong than through solder joints. The alloy facilitated (measured) peak temperatures in between 200-230°C. The use of nitrogen in reflow was existing but certainly not as widespread as with lead-free alloys.
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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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  Reduces solder consumption

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  Reduced cost of production

Physical & chemical properties

Note

Anti-oxidant pellets are not recommended under closed inert atmospheres, nor for Ni-doped solder alloys.

Documents

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  TD Anti Oxidant Pellets (PDF)

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