When highly sophisticated lighting technology assemblies for the automotive industry or complex microprocessor controls for machine and plant engineering are required, there is one name that quickly comes to mind: Herkules-Resotec…

Cover story | published in Productronic 4-20
Author: Michael Haas
When highly sophisticated lighting technology assemblies for the automotive industry or complex microprocessor controls for machine and plant engineering are required, there is one name that quickly comes to mind: Herkules-Resotec. The company, which is based in Baunatal in the heart of Germany, develops, programs and manufactures customer-specific solutions for OEM and serial products – at automotive level, in other words: with 0 ppm fault strategy. Since July, the northern Hesse company has been relying on a further soldering plant from system supplier Ersa to help them achieve this: a vacuum reflow soldering system EXOS 10/26.
Zero parts per million as target and requirement leaves little room for compromise. Herkules-Resotec doesn’t even need that; rather, the EMS service provider has taken the high requirements and incorporated them in its own philosophy: “Our strength is the implementation of customer ideas in electronics in such a way that they result in successful products on the basis of absolutely reliable functionality,” says Günter Reginka, one of three managing directors at Herkules-Resotec. The linchpin of this approach are state-of-the-art SMD equipping lines, where assemblies are manufactured in reproducibly consistent top quality, independent of the batch size – from the individual prototype through to large-scale production. Customers from the automotive industry in particular value the reliability of the assemblies from Herkules-Resotec – but industries such as general machine and plant construction, print post-processing, medical technology and industrial electronics also benefit.
The core competence of the Automotive Division in Baunatal is LED processing – the 80-strong Herkules-Resotec team manufactures everything from daytime running lights through indicators, brake lights and rear lights to ambient lighting – all in top quality and in large-scale production. Products for industry include high-mass components for power electronics such as MOS-FET (metal-oxide-semiconductor field-effect transistor) and IGBT (insulated-gate bipolar transistor).
For these, the production of the solder connection in the reflow soldering process is controlled centrally and reliably, because the development of the components with their increasing miniaturisation and enhanced functionality makes high demands on the characteristics of the solder connection. In addition, the entire process chain and thus further factors must be monitored, starting from the solder paste through the stencil printing process to the reflow soldering furnace in combination with the parameters used. Herkules-Resotec, which has been manufacturing electronics since 1985, has first-class production conditions – not least due to the energy-optimised production hall with ideal material and work flows newly opened in 2018.
Major influence: void share in the soldering spot
Yet back to the assembly: alongside the electrical connection, heat dissipation behaviour is decisive for LEDs and power components. High-power LEDs generate a very high energy density in operation, which must be dissipated mainly via the surface of the soldering spots into the printed circuit board. The main factor of influence is the void share of the soldering spot – consequently the share of gas inclusions which form in the soldering spots during remelting of the solder paste. Depending on size and position, these “voids” reduce the cross-section of the joint, which leads to significantly reduced heat dissipation in the case of BTC power semiconductors or LEDs. The faulty spots contained are thus not good heat conductors (in the worst case this leads to component failure), which is why the void share must be limited to a minimum. Component manufacturers specify thermal limit values in their data sheets, which are used by developers to define the maximum permissible void shares of a soldering spot to avoid exceeding the maximum temperature of the components in operation. The common upper limit is 25% maximum – if the permissible temperature is exceeded, components can become damaged and the service life of parts can be shortened. This is all the more probable the closer to the limit range of their application the components are operated. Better dissipation through a reduced void share to between 10 and 15% counters this effect. The void share can also be pushed to less than 5%, although the process time is then extended accordingly.
Herkules-Resotec and Ersa: high know-how potential
Data basis for transparent production
Highlights Ersa EXOS 10/26
- Perfect synchronisation and transitions thanks to four-section conveyor
- Maintenance-friendly and lubricant-free roller conveyor in the vacuum module
- Optimum access to the vacuum chamber through drives from above
- Optimum temperature profiles through medium-wave radiant heaters in the vacuum module
- Maximum machine availability thanks to fast removal of the conveyor unit in the vacuum module
- Innovative Ersa SMART ELEMENTS cleaning system