Today, convection reflow soldering is the preferred joining technique in the surface mounting of electronic assemblies worldwide. Combined with component development, it alone is able to guarantee the unstoppable and increasing integration density in mobile devices.
Cover story | published in: EPP 11/2019
Author: Rainer Krauss
Today, convection reflow soldering is the preferred joining technique in the surface mounting of electronic assemblies worldwide. Combined with component development, it alone is able to guarantee the unstoppable and increasing integration density in mobile devices. But even in classic areas such as power electronics, THT components are increasingly being transformed towards the world of surface mount technology (SMT).
Electronics production: increased demand for “low-void” joints
Ersa EXOS 10/26 vacuum reflow soldering system
Schematic diagram of the 4-part EXOS enables maximum throughput with optimum printed circuit board guidance, perfect synchronization and ideal transitions The EXOS scores in the vacuum module with its lubricant-free roller transport. Dual track transport for double the productivity is also available as an option
The medium-wave radiant heating system in the vacuum module ensures thermal stability and offers maximum flexibility in profile design
The complete vacuum unit is equipped with quick-release fasteners and mounted on a movable module, which can be removed from the system quickly and easilyOptimum temperature profile with vacuum
The vacuum chamber is heated by heating control circuits, in the chamber cover and in the chamber base. They can be set individually within certain permissible temperature ranges. In addition, the vacuum chamber has a self-sufficient, medium-wave radiant heating system which offers various advantages. The vacuum chamber is basically a very large thermal mass which, on the one hand, guarantees thermal stability during the soldering and vacuum process but, on the other hand, makes it more difficult to change the temperature level in this area. For example, with the help of the heating control circuits in the chamber base and chamber cover, a basic energy level can be created and in addition the profile is realized with the medium-wave heater. When changing the profile, only the medium-wave heater can be adjusted, thus significantly shortening the changeover times. Furthermore, it is generally possible to work with a lower temperature level in the chamber cover and chamber base, which goes a considerable way towards extending the service life of all the components present in this area such as bearings, seals and welds. The solution described offers maximum flexibility in profile design. As with all newly designed components, Ersa engineers designed the heating system with the best possible combination of functionality, process stability and service life in mind. Customer benefits and generation of added value for the customer are always paramount.
Maximum safety and ease of maintenance in the vacuum module
The vacuum parameters such as the target pressure level and the holding time at target pressure level can be controlled separately and can therefore be integrated into the reflow process for specific assemblies. Transmitted light sensors monitor the inlet and outlet areas of the vacuum chamber and thus ensure maximum process reliability. This ensures that there is no assembly in the movement area of the chamber cover. The sensors for this have been developed specially for the Ersa EXOS vacuum application. The drives for opening and closing the chamber are integrated into the upper part of the process tunnel and as a result are easily accessible for maintenance work.
The entire vacuum unit with pump, filters and valves was mostly integrated into the EXOS machine frame so that the additional footprint is very small (less than 2 m²). Maintenance work can be carried out conveniently outside the electronics production area because the complete unit is mounted on a separate, mobile module which can easily be removed from the system thanks to quick-release fasteners. Downtimes are thus reduced to the absolute minimum and machine availability is increased enormously because all components can be reached quickly and conveniently in this way.
Safe processes, maximum throughput, minimum footprint
Another feature of the modular EXOS is the transport system which is divided into four segments. Infeed, pre-heating zone with peak zone, vacuum module and cooling zone each has its own transport. Due to the separate transport in the infeed area, there is no need for an external input module. The optional dual track transport (for printed circuit board formats up to 400 x280 mm) enables maximum throughput with optimum PCB guidance, perfect synchronization and ideal transitions. The integrated infeed module ensures simultaneous loading of the EXOS with assemblies on both tracks so that they arrive in the vacuum chamber at the same time. Thanks to the dynamic transport speed in the cooling module, the assemblies leave the system at an even lower temperature, eliminating waiting times for further processing. Different chain types are available for transport, so that different requirements for edge support and weight of the assemblies can be implemented.
Highest assembly quality and machine availability thanks to roller transport
The vacuum chamber is equipped with a stable, easily exchangeable roller transport system that does not require lubricants. Thus, on the one hand an extremely low-maintenance method of transport was chosen, on the other hand there is no danger of lubricant deposition on the assembly during the vacuum process.
Ersa EXOS provides the perfect answer when vacuum reflow soldering requires a significant increase in the reliability of solder joints due to minimum void rates combined with greater system flexibility!
Ersa Reflow Soldering with vacuum – EXOS 10/26 in video
EXOS 10/26 in figures:
- Dimensions: 7,590 mm (l), 1,671 mm (w), 1,580 mm (h)
- Heating zone: 4,560 mm (9 preheating zones top + bottom)
- 2 peak zones top + bottom
- Vacuum module: 520 mm (reduces voids by almost 100%)
- Cooling zone (4 cooling zones top + bottom, 2,280 mm)
- Single transport (PCB format 400 x 630 mm) or dual track (400 x 280 mm)
Highlights of Ersa EXOS 10/26 – Convection reflow soldering system with vacuum chamber:
- Perfect synchronization and transitions due to four-part transport
- Maintenance-friendly and lubricant-free roller transport in the vacuum module
- Optimum accessibility of the vacuum chamber due to drives from above
- Optimum temperature profiles due to medium-wave radiant heaters in the vacuum module
- Maximum machine availability due to fast removal of the transport unit in the vacuum module
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