Ersa has been engaged in the repair of electronic assemblies for 25 years. The focus here is particularly on the rework of highly polarized SMT components. In times of component shortages and interrupted supply chains, it is more important than ever to maintain the value already achieved…
Published in: Productronic 05/2022
Author: Jörg Nolte
Ersa has been engaged in the repair of electronic assemblies for 25 years. The focus here is particularly on the rework of highly polarized SMT components. In times of component shortages and interrupted supply chains, it is more important than ever to maintain the value already achieved, also in terms of sustainable management. Reviews and insights into this exciting technology are provided by Ersa Product Manager Jörg Nolte.
It all started in 1997 with the IR 500 A, the first infrared rework system from Ersa. It was developed together with the small Odenwald company Rewatronik in order to be able to safely desolder and solder the “Ball Grid Array” components (BGA), which were still new at that time. Very quickly, in a further cooperation with the Swiss placement specialist Essemtec, a suitable unit for component placement was designed, because fine-pitch components and those with hidden solder joints could not be placed precisely enough by hand. “When I joined Ersa in 2000, SMT/BGA repair was still in its early days,” reports Jörg Nolte, who is Ersa’s product manager for rework. He adds, “But then things progressed steadily, because they had backed the right horse – the spread of ball grid arrays in particular, which were initially difficult to master, increased steadily and with it the need for qualified rework.”
Today, the BGA belongs to the family of bottom terminated components (BTC), i.e. components with solder joints on the bottom side of the component. In the early years, the BGAs were often the most sensitive components of an assembly: If the thermal balance in the soldering process was not completely level, the package was deformed and bridging or other soldering defects often occurred as a result. And thus to more frequent failures and the need for repairs. The classical problem with the BGAs is and was too much stress in the solder joints of the corner balls and the associated microcracks. The re-melting of the BGA with the addition of a little flux remains a proven method of repairing such defects to this day. Even today, the followers of the BGA are sensitive to the relevant process parameters. “Micro Lead Frame” (MLF) components tend to float when the amount of solder used is inaccurate, resulting in open signal contacts. The list of error patterns and causes can be continued – the important thing is that safe repair processes have been established for all these cases.
Even today, you can find adventurous clips on the internet of people trying to swap processors and other components on circuit boards with the help of hot air guns. The soldering results: more than questionable. Ersa had to invest a lot of time and energy in convincing users of the infrared technology of its systems, from cell phone service centers to the electronics industry. Established manufacturers of hot gas rework systems also did everything they could at the time to torpedo IR technology. “It was claimed that components would get too hot, the process could not be controlled and reflective surfaces would not get hot, the user would be harmed by the IR radiation,” recalls Nolte of the verbal barriers of the early years.
The medium-wave and thus largely invisible radiant heat of the ceramic heaters, however, was convincing: Unlike quartz emitters, their radiation spectrum is perfectly suited to heat metals, plastics, ceramics and epoxy resins of a fixed assembly quickly and homogeneously. The temperature differences measured over a component (delta T) reached values of only 6 °C and below. It quickly became clear to many users that the sensor-guided process of a medium-wave IR rework system even has advantages over established techniques – the solder profile follows the specification very precisely due to precise temperature control. The components and assemblies are heated homogeneously and gently. Because no component-specific nozzles are required, there is an open view of the solder joints and the process can be observed by means of cameras.
During the introduction of lead-free solders in 2006, the melting temperatures of the solder alloys (leaded 183 °C, lead-free approx. 217 °C) increased the demands on the soldering equipment and rework systems. Higher temperatures resulted in smaller process windows, and many component materials had to follow suit. Precise process control became increasingly important.
The Ersa IR/PL 550 and its bigger brother IR/PL 650 shaped the industrial PCB repair of that time. As a technical innovation, the non-contact temperature measurement by means of a pyrometer was introduced for the first time in these systems. Due to the demands of repairing large and high-mass PCBs from the sector of IT infrastructure, the first truly large-format rework system was created for an American EMS provider in the form of the Ersa IR/PL 650 XL. Rework has been professionalized further since then, although some industries continue to exclude it. Studies such as the “Leitfaden Rework elektronischer Baugruppen” of the ZVEI (published in 2017) show that professional rework leads to reliable results if – as in the line process – all important parameters are met. “Often it is not the lack of confidence in the technical process, but it is the approval work associated with the repair that causes this reluctance,” says Jörg Nolte. At this point, a deeper cooperation between users, equipment manufacturers and institutions is desirable.
Maintaining added value and avoiding unnecessary rejects due to a bridge at a QFP or BGA is the first level of sustainable behaviour. The “right to repair” called for by the EU Commission forms the basis for avoiding electronic waste and also for advancing electronics production on the way to conserving resources and moving toward a circular economy. In industry and in service centers worldwide, thousands of circuit boards are processed with Ersa rework systems every day, thus saving them from being uncontrollably scrapped in some cases!
Ersa has also defined sustainability on another level: While quite a few rework system suppliers have appeared and disappeared over the past 25 years, Ersa has also become established in the electronics industry in this segment. Long-term customer relationships, an exemplary worldwide service and very long spare parts availability, even for products that have already been discontinued, bear witness to this philosophy. Much to the delight of Product Manager Jörg Nolte: “Today, we receive wear part requests for devices that were sold 15 years ago – that’s great!”
Ersa goes hybrid and automatic
Hybrid technology makes its way into Ersa rework systems with the manually operated HR 100 and the automatic HR 600 rework system. The proven IR heating technology is supported here in the area of the top radiators by means of convection. This makes even better use of the thermal energy emitted by the radiator and heats the target component more quickly. Disadvantages known from hot air systems, e.g. the blowing away of the smallest chip components, do not occur because very low air volumes are used.
The HR 600, introduced in 2012, also addresses an important customer request: more automation! For the first time, the desoldering process, component placement and soldering process are linked in such a way that the operator of the device has hardly any influence on the subsequent result. Process reliability and repeatability are coming into focus. The special feature of the HR 600, which in its updated version is still one of the most popular repair systems today, is automated component placement. With the help of two cameras, image processing and a high-precision axis system, the target component is automatically positioned precisely on the circuit board and then soldered in automatically as well. For productivity and process reliability in this process, the HR 600/2 represents a milestone.
The new generation
In the meantime, the Ersa Rework portfolio has gained further members: “Starting with the HR 500, today´s product range up to the HR 600 XL covers practically all relevant customer requirements of the worldwide markets and industries,” Jörg Nolte summarizes the positioning of the Ersa brand. The newer systems are convincing both in terms of their technology and in terms of the requirement for a standardized software platform. “The user hardly has to get re-accustomed when switching from one system to the other – everything is designed in the same way,” outlines Nolte. Ersa was relatively late in bringing the technology into the company with the first HR 550, which was developed completely in-house. Jörg Nolte: “It was a big learning curve for us, of course, but we now have all the engineering expertise and can therefore react much better to market trends. Especially in software engineering, this is a key factor today.” In the flagship of the product line, the HR 600 XL, it was thus possible to implement functional extensions and optimizations requested by customers quickly and with high quality – with an extended bottom heater, the system can now process assemblies up to a size of 625 x 1,250 mm, and with large heating heads, components with edge lengths of over 100 mm!
And what’s next?
When asked whether everything is done after 25 years, Jörg Nolte smirks and explains: “In principle, yes, but development continues. And that’s a good thing. Because contrary to all forecasts, assemblies will foreseeably have to be reworked.” An automatic residual solder removal system is currently being launched for the HR 600 XL. In the field of sensor technology, we are working on the optimization of non-contact measuring technology.
Further topics on the accuracy of the systems, the development of heating technology, additional automation and the connection of the devices to Manufacturing Execution Systems (MES) are also on the roadmap. This makes rework a valuable part of the production process in the sense of sustainable production. Yes, even the currently heavily used term of artificial intelligence has already been discussed. And, of course, the processing of new component designs must be kept in mind, as must the costs for manufacturing the systems. When asked what he is most excited about 25 years of Ersa Rework systems, Nolte responds: “It feels good that we are giving our customers useful tools!” And in the future, what will be next? Certainly a lot more from the Rework section, because contrary to many predictions, PCBs will continue to be reworked in the future …
Reasons for the rework of electronic assemblies:
- The component is defective.
- The wrong component has been placed.
- The component was assembled in the wrong orientation.
- The component was soldered badly (bridges, open solder joints etc.).
- The component is programmed badly.
- A component is saved for re-use (Recycling).
- A change is made to the board (Redesign).
- Assembly is built up as a sample and one or more components are refitted (Prototyping).
- Tests are performed on the assembly, e.g. cross swapping (Testing).
- Data of a component from a defective board must be saved (forensics).
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