Laser 25
Interflux® Laser 25 for lead-free alloys is a halide free no-clean solder wire with extremely low spattering properties.
Suitable for
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Robot soldering is a technology used in electronics manufacturing to connect electronic or electro mechanical components to a carrier material. The components are usually through hole components and the carrier a PCB board. Robot soldering is mainly used in these cases where the standard soldering processes like reflow, wave and selective soldering cannot be used due to e.g. temperature sensitivity of the components and limited solderability of the surface. In general robot soldering is a rather slow soldering process, not really suitable for high volume productions. The soldering robot has a wettable soldering tip. The temperature of this soldering tip can be set to a certain temperature that will be determined by the used soldering alloy which is applied by means of a solder wire. The soldering tip is positioned on the surfaces to be soldered. The X-Y-Z positioning can vary from one system to another. In some cases the soldering tip is doing all the movement but in other cases the X-Y positioning is done by moving the PCB board. Some systems can also program the angle of soldering tip and from which side it accesses the solderable surfaces. This can be useful when accessibility to the solderable surfaces is limited by e.g. components that are already on the PCB board from a previous assembly/soldering process. In a first stage the soldering tip will preheat the surfaces to be soldered. To promote heat transfer, in general a bit of solder is already added to the contact interface of the soldering tip and the surfaces to be soldered. The liquid solder improves heat transfer and speeds up the process. The time of preheating will be determined by the thermal mass of the component and PCB board. After that, the correct volume of solder wire is added and the liquid soldering alloy will wet the surfaces to be soldered and the component and PCB board are connected with a solder joint. The main focal points of the robot soldering process are usually optimising soldering speed, limiting solder and flux spatters, limiting flux residue formation after soldering and limiting pollution of the soldering tip. A key parameter in this matter is the used solder wire and more specifically the flux that is contained within this solder wire. For faster soldering, often an activated (halogenated) solder wire from the 'L1' classification or higher is being used. Solder wires specifically designed for robot soldering exist. Beside fast soldering they will limit spatters, flux residue and soldering tip pollution. They also exist within the 'L0'-classification
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Laser soldering is a contactless soldering technology used in electronics manufacturing to connect electronic or electro mechanical components to a carrier material. The components are usually through hole components and the carrier a PCB board. Laser soldering is mainly used in these cases where the accessibility to the surfaces to be soldered is limited and a standard soldering robot with a soldering tip has no access. In general laser soldering is a faster soldering process than standard robot soldering but still not really suitable for high volume productions. The surfaces to be soldered are heated up by a laser beam that is applied by one or more laser diodes. Laser beams heat up the surfaces very quickly. More laser diodes give the opportunity to warm up the surfaces at different positions resulting in a more uniform heating. The solder is either already present as a deposited solder paste or added by means of a solder wire with flux inside. For most applications, solder wire is used. In laser soldering, the main focus is on time optimisation. Usually, a profile is created in three stages: preheating, soldering and holding. Therefore the capacity of the lasers and heating time can be adjusted. These settings depend on the thermal mass of the materials to be soldered and are often retrieved from experience. It is advisable to have a preheating of at least 300°C before feeding the solder wire. The amount of solder wire fed, depends on the volume of the solder joint. Beside fast soldering, other focal points of the laser soldering process are limiting solder and flux spatters and limiting flux residues after soldering. A key parameter in this matter is the used solder wire and more specifically the flux that is contained within this solder wire. For faster soldering, often an activated (halogenated) solder wire from the 'L1' classification or higher is being used. Solder wires specifically designed for laser soldering will also limit spatters and flux residue. They also exist within the 'L0'-classification.
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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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Spattering of a solder wire is caused by evaporation of flux chemistry contained within the solder wire. Flux chemistry substances passing into the gas phase create a pressure that at a certain moment is released as a small explosion that can be accompanied by some hot spatters of flux and alloy. These spatters are unwanted because they can create pollution and even short circuits on the electronic unit. Specifically lead-free solder wires are sensitive to this phenomenon because they have high melting points. This means that the temperature they need to reach to get to the liquid state is high and the higher the temperature, the higher the vapor pressure of the evaporating soldering flux. Some solder wires have been specifically designed to minimise this spattering phenomenon. They can be very interesting for robot soldering and laser soldering processes where spaterring is a known issue. But also for normal hand soldering of electronic units, a solder wire with low spattering properties can be interesting.