There is a saying that cobblers have the worst shoes and plumbers have leaking faucets. So, what about the automation of an automation technology provider? It is rare for manufacturers to be able to use any innovation immediately in their own production processes. On the one hand, new solutions must ultimately meet the latest challenges, and on the other hand, the timing has to be right in order to implement them during ongoing operations. At its site in Beierfeld, Germany, Turck has now been able to directly implement a recently launched innovation, and automate the handling of solder pastes in its electronics production.
The company in Beierfeld operates an SMT production facility for printed circuit boards, in addition to many other production lines. SMT stands for ‘surface mounted technology’ and refers to a production process in which components such as resistors or capacitors are soldered directly onto a circuit board – in contrast to the traditional THT (through-hole technology) process, in which components are inserted through holes in the circuit board with small wire pins and then soldered. In the SMT process, solder paste is applied very thinly (<150 micrometres) to the circuit boards with printers. The printed circuit board is then fitted with the components and soldered in the subsequent reflow process.
Climatic conditions of the solder pastes influence quality
To achieve the best possible quality of the solder joint, the solder paste must be stored within a certain temperature range. Moreover, opened containers must not be used for more than 30 days in total. Before processing in the printer, they must be stored at room temperature for at least four hours before the containers can be opened.
After this acclimatisation stage, to prevent condensation, the paste must be mixed for another 60 to 90 seconds – and it must be shaken, not stirred. On average, the paste must only be processed at 23-27°C and a humidity of 40-60% (depending on the manufacturer). After the printed circuit boards have been printed, no more than eight hours must elapse before the circuit boards are soldered in the oven.
All in all, therefore, a number of parameters must be observed, for which any manual control using handwritten notes requires a great deal of attention and care. As with all human processes, there is no such thing as 100% certainty in manual solder paste inspection. There may be a loss in quality if the specified parameters are not observed exactly. The paste does not then optimally fulfil its task of facilitating the melting process and preventing oxidation, and more scrap is produced.
The production managers in Beierfeld wanted to automate, and thus optimise, the tracking of solder pastes. Last but not least, the ISO 9001 and IATF 16949 certifications, with which Turck Beierfeld must comply as a supplier to the automotive industry, stipulates continuous tracking of the processes and preliminary products.
Manual tracking of solder pastes
The storage times in the refrigerator were previously manually recorded by scanning the paste containers. Removal and opening were recorded with notes on the containers or with documentation sheets. The refrigerators already had internal temperature monitoring, but did not record trends, only triggering an email to logistics when the temperature exceeded or fell below the defined range.
Together with his team and project manager Linda Galle, Christian Seliger, who is responsible for the Research and Development business unit at the Beierfeld site, planned and implemented the automated recording and documentation of paste handling. “In order to be able to achieve rapid project successes, even during ongoing operations, we divided the project into several stages,” says Galle. “With our Plan-Do-Check-Act approach, we ensure that each stage is completed successfully before starting the next one.”
In the first stage, the first task was to monitor and centrally document the climatic conditions in the refrigerators, the printers, and the workstation for preheating. If there are any critical values, the system must generate appropriate messages or alarms. RFID-supported recording of the solder paste containers and a connection to a manufacturing execution system (MES) will be implemented in the next stage of the project.
The monitoring of the climate in the refrigerators was implemented with Turck’s IM18-CCM50 condition monitoring system. One of these control cabinet guards, with an integrated Linux computer, is located in each of the five refrigerators. With their integrated sensors, they detect the distance to the refrigerator door and the temperature in the cabinet. The devices are also able to measure air humidity, but this is not important in this application, since only closed paste containers are in the refrigerators.
The temperature and humidity in the printers, on the other hand, are very relevant, so the CMTH combined temperature-humidity sensor records these variables. Each of the three standalone solder paste printers has one of these condition monitoring sensors, and another sensor records the conditions at the workstation where the pastes are stored for acclimatisation. Each CMTH sensor is connected to a compact TBEN-S IO-Link master, which transmits the data to the production network. The TBEN-L5-SE-M2-managed IP67 switch also integrates all IM18-CCM50s into the production network.
With their open Linux operating system, the IM18-CCM50 devices are designed for the installation of OEM software, allowing users to implement their own software solutions. They form the brain of the system, which handles the storage and the communication with the sensors, the network and the Turck Cloud. To monitor the refrigerators, only network drivers and scripts for collecting sensor data are installed on the condition monitoring platform. The IM18-CCM50 transmits the data of the integrated sensors as well as the CMTH sensors directly via Ethernet to the Turck Cloud.
Clear dashboards in the Turck Cloud display climatic conditions
This first project phase of solder paste tracking is automated to ensure that the temperatures in the refrigerators, at the acclimatisation workstation, and in the printers comply with the specifications. The times when the pastes are stored and removed are currently still documented by hand or recorded by scanning the QR codes on the containers. If humidity or temperature increase, this is indicated to the employees on the dashboard in the Turck Cloud. Long-term trends can also be identified in addition to the current values. In future, it would be possible for the MES to be connected to implement trend detection and analyse correlations between data series.
“The condition monitoring solution based on the IM18-CCM that has now been implemented was only the first step on the way to fully automated monitoring of the storage and use of solder pastes. In the follow-up project, we will connect our MES and thus complete the digitalisation and automation of our production. In this way, we can maintain quality at the highest level, even when operating at maximum capacity, and thereby avoid unnecessary costs due to overlaid solder pastes,” Seliger sums up.
Outlook: RFID-supported, seamless solder paste tracking
In the second expansion stage, the tracking of pastes will be implemented directly with RFID tags on each container, which at the same time enables the recording of correct acclimatisation before opening the containers. Since the IM18-CCM devices then communicate directly with the MES, which controls the production orders for the printers, the system can immediately check whether the paste container used has been correctly stored and acclimatised before the PCBs are printed, or block use if the required conditions have not been maintained. If all data is available in the MES, further information could also be obtained from it, for example, to uncover weak points and sources of errors.
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