Best Practice: Herkules-Resotec
Absolute quality in LED
0 ppm error strategy with vacuum reflow soldering
When it comes to highly sophisticated lighting technology assemblies for the automotive industry or microprocessor controls in mechanical engineering, a name quickly comes into play: Hercules-Resotec. The company from Baunatal develops, programs and manufactures customer-specific solutions for OEM and series products at automotive level. For this purpose, the North Hesse company has been relying on Ersa hardware again since mid-2019: an EXOS 10/26 vacuum reflow soldering system.
Zero parts per million as a goal, little room for compromise. Neither does EMS service provider Herkules-Resotec need to: “Our strength is to translate customer ideas into electronics in such a way that successful products are created on the basis of absolutely reliable functionality,” says Günter Reginka, one of three managing directors. The lynchpin of this approach are state-of-the-art SMD assembly lines, on which batch size-independent assemblies are produced in reproducible top quality. Customers from the automotive world in particular appreciate the reliability of assemblies from Herkules-Resotec, but also general mechanical and plant engineering, print post-processing, medical technology and industrial electronics.
Automotive core competence in Baunatal is LED processing – from daytime running lights, indicators, brake lights and taillights to ambient lighting, Herkules-Resotec produces quality in large series. The industrial products are complemented by mass-produced power electronics components such as metal oxide semiconductor field effect transistors (MOS-FET) and bipolar transistors (IGBT). For this purpose, the production of the reflow soldering connection must be reliably mastered throughout the entire process, because the development of the components with increasing miniaturization makes high demands. At Herkules-Resotec, the production hall, which was opened in 2018, offers ideal material and workflow and provides the best production conditions.
Significant influence: Void content in the solder joint
In addition to the electrical connection, the heat dissipation behavior of LEDs and power components is decisive. During operation, high-power LEDs generate a very high energy density, which is mainly dissipated into the circuit board via the surface of the solder joints. The void portion of the solder joint is a significant influencing factor here – depending on size and position, these “voids” reduce the cross-section of the joint, which leads to considerably reduced heat dissipation in BTC power semiconductors or LEDs, for example. In relation to the thermal limit values of the component manufacturers, developers define the maximum permissible void content of a solder joint in order not to exceed the maximum operating temperature of the components. The common upper limit is 25% – if exceeded, components can be damaged and the service life of the components shortened. A better dissipation capability by reducing the void content to 10 to 15% counteracts this effect.
Highlights Ersa EXOS 10/26
- Perfect synchronization and transitions through four-part transport
- Maintenance-friendly and lubricant-free roller transport in the vacuum module
- Optimum accessibility to the vacuum chamber through drives from above
- Optimum temperature profiles due to medium wave radiant heaters in the vacuum module
- Highest machine availability through quick removal of the transport unit in the vacuum module
- Innovative Ersa SMART ELEMENTS cleaning system
Herkules-Resotec and Ersa: High know-how potential
Against this background, Herkules-Resotec invested in a reflow oven with a vacuum soldering chamber: an Ersa EXOS 10/26 with eleven conventional heating zones, three heating circuits for the vacuum chamber and four cooling zones. The modular system convinced with features such as four-segment transport system with infeed, preheating zone with peak zone, vacuum module and cooling module, each with its own transport.
The same applies to the medium wave emitters in the vacuum process with stable temperature profiles – the heat transfer of the EXOS, based on the technically advanced Ersa multi-jet convection technology, guarantees a minimum ΔT with the lowest possible energy consumption. In the vacuum chamber itself, a stable, easily exchangeable and lubricant-free roller conveyor is used – the best conditions for low-maintenance transport and zero lubricant deposit on the assembly.
Almost the entire soldering technology of the electronics production at Herkules-Resotec comes from Ersa – the beginning was marked by an EWS 330 wave soldering machine, from 2004 on HOTFLOW 2 machines were installed. From 2014, one HOTFLOW 3/14 followed in a 2-year cycle, before the EXOS 10/26 expanded the Herkules-Resotec machine park. Thanks to intelligent features, the Ersa EXOS 10/26 allows “void-free” production to be carried out particularly economically – with an LED module produced on it, the void rate dropped from 8.5% to an impressive 0.5%!
As a pilot user of the EXOS 10/26, Herkules-Resotec provided important information on productivity, traceability, service and maintenance. In terms of productivity, for example, the vacuum soldering system must achieve the same throughput as the classic reflow process. Key point maintenance friendliness: The entire vacuum unit with pump, filters and valves is largely integrated in the machine room, so that the additional footprint is less than 2 m2 – pending maintenance work can be conveniently carried out outside the electronics production area, as the complete unit is mounted on a separate, movable module. Downtimes are reduced to an absolute minimum.
Data basis for transparent production
Traceability was an absolute must for Herkules-Resotec – the Management Execution System (MES) enables traceability down to component level. For the EXOS, in addition to the furnace zone temperatures, the vacuum level achieved and the process times used are also included – all data is provided by the MES data interface. Another important requirement was predictive maintenance, in which maintenance intervals are adapted to throughput and performance. The reflow system “knows” exactly how long the vacuum pump was active and signals when an oil change is due. Elementary for a three-shift operation like Herkules-Resotec!