The Ersa Webinars at one glance:
With the successful English webinar premiere “Technological possibilities in selective mini-wave soldering”, system supplier Ersa successfully opened its online channel also for English-speaking customers and interested parties. At the same time this was the starting signal for the upcoming webinars. The 3,500 Ersa selective systems installed worldwide impressively demonstrate the great potential of this soldering technology, which offers users a wide range of options for solving individual applications. The range of modules on the customer side is in no way inferior to this – it ranges from fingernail-sized sensor boards to high-layer multilayers and power electronics with 400 and more amperes on the PCB. Ersa Process Technology Manager Jürgen Friedrich explained how high-performance electronics are created from multiple requirements in a one-hour web presentation.
The aim of the selective soldering process is a 100% solder penetration, the avoidance of solder bridges in plug connectors and a no-clean process. The greatest challenge is to master the variance that results from different pin diameters. It ranges from 8 mm down to fine pitch components with 1.27 mm pitch and 0.3 mm pins, flexible PCBs with 200 µm need to be mastered just as much as high-layer thick copper boards with 4x 400 µm inner layers and 2x 100 µm outer layers. The soldering process itself is divided into flux application, preheating (heating of components) and soldering (production of solder joints). Unlike wave soldering, selective soldering relies on multidrop fluxing with precise and defined flux application. The flux can thus be applied in points or in webs, and the flux quantity per solder joint is individually and freely programmable.
During preheating, the flux carrier medium evaporates and part of the soldering heat is transferred to the assembly – Ersa uses IR emitters as standard. These can be controlled from 0 to 100% without inertia, and different temperature profiles can be programmed and controlled in four time windows. Depending on the board format, preheating modules can be adapted to the length of the assemblies in order to effectively preheat assemblies and save energy at the same time. A maximum of two preheating modules can be used in front of the soldering module, for “thick” boards the preheating can take two to 2½ minutes. The preheating temperature makes an important contribution to covering the soldering heat requirement, especially for multilayer and power electronics.
The absolute heart of the soldering system is the soldering module – where solder joints are formed. Here, the soldering result can be positively influenced by optimally balancing the parameters solder temperature and wetting time, thus enabling optimum energy transfer into the assembly. Often a balancing act, 285 °C should not be exceeded, as this is the specified limit for many base materials of the PCB. Once the soldering process is defined, the boundary conditions of the workpiece, i.e. the assembly, must also be examined. What is the solder heat requirement, solder heat resistance, heat traps, pin geometry, pad diameter – all questions that need to be answered during the layout phase.
After the presentation, the speaker answered numerous questions, for example about freely adjustable preheating, power electronics, solder analysis, x/y speed for fine pitch components and solder bridge-free results. Selective soldering is a broad field, more in-depth exchange is done on a bilateral basis. “We are always happy to provide support for your selective projects and hope to have provided you with relevant information for your current day-to-day business,” said Jürgen Friedrich to the over 50 participants of the webinar.