µ-dIFe 7

Suitable for

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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.
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  Reflow soldering

  Reflow soldering is the most used soldering process in electronics assembly. Mainly SMD (Surface Mount Device) components but also some through hole components are soldered in a reflow oven to a PCB (Printed Circuit Board) by means of a solder paste. The reflow oven is usually a forced convection oven but also vapor phase and IR ovens are possible. The first step of the process is to apply solder paste to the pads of the PCB or in case of through hole components in the through hole. This latter is called Pin in Paste (PiP) or intrusive reflow technology. The main application method is stencil printing but also dispensing and solder paste jetting are possible. Depending on the application method the solder paste will have a different consistency and comes in a different packaging. Solder paste is a mixture of a solder powder and a gel flux. The type of gel flux and the type of powder and in what ratios they are mixed, will determine the consistency of the paste. The solder powder is made of a certain soldering alloy and has a certain grain size (distribution). Finer grains size are used for smaller pitch components and smaller stencil apertures. Dispensing and even more jetting also require finer grain sizes. The gel flux contains substances to deoxydize the surfaces to be soldered. It also contains substances that will determine the consistency and the behavior of the solder paste in the process to a great extent. When stencil printing solder paste, an important parameter is that the solder paste keeps its printing properties during the time it will be on the stencil. This is often referred to as the stability of the solder paste. Solder paste stability is hard to quantify but can be estimated from the stencil life indication in the technical datasheet. After solder paste application SMD components  are placed on the solder paste with their solderable connections. In most cases, this is done with a Pick and Place machine. The solder paste needs to have enough adhesion force to keep the components in their place until soldering. A conveyor will transport the PCB through a reflow oven where the PCB board is submitted to a reflow soldering profile. This profile is created by the temperature settings of the different convection zones. They are usually situated as well from the top as from the bottom side.  Beside the temperature settings, in some cases also the convection rate of the zones can be programmed to get better or lower heat transfer, or when some high components experience too much force from the convection. It is the goal to get all components to soldering temperatures, which is determined by the used soldering alloy, without damaging or overheating temperature sensitive components. This can be a challenge for units with a large diversity of big and small components or an uneven Cu-distribution in the PCB board. In that perspective a low melting point soldering alloy substantially limits the risk of damaging or predamaging components and PCB boards. The speed of the conveyor will determine the time of the profile and the throughput of the oven. In most cases however the Pick and Place process is limiting the throughput.  Not all electronic components are suitable for reflow soldering. Some because of their thermal mass like e.g. big transfos or others because of their thermal sensitivity like e.g. some displays, connectors, relays, fuses,... These components are usually available as a through hole components and soldered in other processes like selective soldering, wave soldering, hand soldering, robot soldering, laser soldering,...
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  Lead-free soldering

Key advantages

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  Fast and easy application

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  Repeatable and selective paste volume

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  Reduced risk of bridging on μ-BGAs

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  Suitable for the ERSA Dip&Print Station

  The ERSA Dip&Print Station is part of a rework station for electronic components that are hard to repair with a standard (de)soldering station. For example Bottom Terminated Components (BTCs), like Ball Grid Arrays (BGAs), QFNs, DFNs, LGAs,...but also some J-lead and Gull wing ICs like QFPs and PLCCs are components that need a special rework station. The ERSA Dip&Print Station is designed to apply solder paste or flux gel to those components by means of stencil printing or dipping. The use of soldering chemistry that is specifically designed for this process is mandatory to get a good final result. For dipping, which can be used for components that have a stand-off between the body of the component and solderable leads, a special dipping solder paste is used which will give a repeatable quantity of solder on the leads that are dipped into the dipping paste. For stencil printing the same solder paste as for the SMT process can be used. A flux gel can be used for both stencil printing and dipping. A flux gel can only be used when enough solder is present to make a solder joint as is the case for e.g. BGAs.
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  For Ball Grid Arrays, J-lead and Gull Wing ICs

  Ball Grid Arrays (BGAs), J-lead and Gull wing ICs are components that are, because of their physical lay-out) difficult to rework with a normal (de)soldering station. In most cases rework and repair is done with a rework station that can simulate a reflow profile. The use of soldering chemistry that is specifically designed for this process is mandatory to get a good final result. Depending on the component that is being reworked and the process step, different types of soldering chemistry can have the preference. A flux gel is often used because of its large process window. Different viscosities of the flux gel will support different application methods, like dispensing, application by brush, stencil printing, pin transfer, dipping,... Liquid repair fluxes on the other hand allow very precise application with a flux pen with glass fibre tip and will give lower residue formation than gel fluxes. Low residue is sometimes required because of esthetic reasons but also when a conformal coating needs to be applied or for applications that can be sensitive to residues like e.g. high frequency electronics. Low residue will also facilitate the use of an Ersascope that is used to look underneath a BGA after soldering. The process window of liquid fluxes however is smaller than that of gel fluxes. Solder pastes can also be used for rework and repair of Ball Grid Arrays (BGAs) but certainly for J-lead and Gull wing ICs that need the extra solder for the solder joint. For stencil printing the same solder paste as for the SMT process can be used. For dipping, which can be used for components that have a stand-off between the body of the component and solderable leads, a special dipping solder paste is used which will give a repeatable quantity of solder on the leads that are dipped into the dipping paste. 
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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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  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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  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

Halide content

0,00%

Documents

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  TD micro dIFe 7 (PDF)

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