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26 SMT Magazine • November 2014 feaTure ing and desoldering processes are operated au- tomatically. introduction Rework had a shadowy existence over the past 10 or 15 years. It was hard to accept that zero-failure production was, and currently is, a myth. But those in electronic production know that production failures have been present and will continue to exist. They have tried to get faulty assemblies to work, while others did not know how rework was accomplished and how the quality of the rework operators could ever be controlled. With the SMT process standardized and widely understood, some experts have started to look closer at the side processes, including touch-up and repair of assemblies. Moreover, the introduction of bottom-terminated com- ponents, such as BGAs, has created a push for improved rework and repair activities. Another driver was the RoHS lead-free directive enacted in Europe in 2006, with formerly easy-to-han- dle rework activities struggling with smaller process windows and new materials. All in all, the responsible personnel recognized these challenges and requested more stable and re- peatable rework equipment from the suppliers. A more detailed look at production costs led many customers to ask for better automated, fully controlled rework machines, prompting the development of new rework systems to sat- isfy such requirements. A detailed technical de- scription of an example of this type of rework system follows. current technologies The hot-air gun used for BGA repair has been declared obsolete by some in the indus- try, but in reality, they are still in the drawer. For more than 20 years, the suppliers of profes- sional rework equipment have been presenting a battalion of different systems to remove and install bottom-terminated components and other SMDs. In the area of energy transmission for the soldering and desoldering processes, the territory was split up into "hot gas" and "infra- red radiation," but the means for component placement stayed the same. There was very lit- tle innovation in terms of alignment and place- ment of components onto the substrates. The current component placement technol- ogies can be divided into three major groups: 1. Placement with optical beam splitter 2. Placement with alignment tool 3. Vision placement Other than in pick-and-place machines, during rework mostly only one component needs to be relocated onto a specific position on the PCB. CAD or Gerber data is often not available and most systems are not yet capable of handling such electronic information. In or- der to achieve a precise component handling and placement, all of these methods do require figure 1: The component placement procedure, with two cameras generating images. new PLacement tecHnoLogy For rework systems continues