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24 SMT007 MAGAZINE I FEBRUARY 2020 APC Printer Feedback Results The continued demand for smaller, lighter, and smarter electronic devices has led to an increasing use of smaller components. These shrinking packages force smaller aperture designs and finer solder paste, which have made stencil printing a highly-sophisticated process with a tremendous impact on produc- tion yields. It has been reported that 70% of all PCB assembly defects are primarily due to problems directly associated with the solder printing process. Manufacturers must ensure the optimal printing parameters are consis- tently applied during production. An enhanced solution, formed of interlink- ing software modules, can actively optimize the printing process by combining real-time printing information with SPI measurement data. More advanced software automatically performs design of experiment (DOE) intended to complete a detailed SPI result analysis using advanced diagnostic algorithms and noise fil- tering models and then recommends the ideal print parameters. The software triggers the SPI to send the information to the screen printer to automatically adjust the parameters. The max and min values for printing pressure, printing speed, and separation speed can be set when adjusting the printer parameters. Other software can use multiple anomaly- detection algorithms to actively optimize the print process and further reduce false calls. Ideally, the software will evolve to autono- mously generate optimized models and fine- tune the process parameters in real-time using actual results. While the software modules would each provide standalone process ben- efits, the combined power of an AI-powered software suite would ensure the highest pro- cess reliability and production flexibility with- out dedicated resources and expertise. APC Mounter Feedback Results With the benefits of printers communicating with SPI machines known, what about mount- ers and AOI? Connecting mounters with AOI delivers obvious benefits like improved yields, especially in high-density boards. The mounters use the received data to update the placement program, ensuring the components are placed onto the solder deposits rather than onto the substrate pads. This approach to placing compo- nents on the printed solder uses the self-align- ment principle to increase production yields and reduce defects. As shown in Figure 3, when sol- der is off pad and components are placed to the pre-defined placement location in the program, self-alignment is not effective. During reflow, components will shift off pad or bridge with other pads, causing rework or scrap. Alternatively, corrected placements will maximize the self-alignment principle. Mount- ing these microchips onto the solder paste instead of the pad will increase yields and quality. Figure 4 shows a set of test results. Using this advanced communication, the 3D AOI can feed corrected mounting position val- ues to mounters, which ensures the mounters place the components in the correct position. This improves process repeatability by auto- matically adjusting placements and identifying trends to make further positional corrections. Figure 3: Traditional chip placement onto pads before and after reflow. (Source: Panasonic System Solutions Company of North America-Process Automation, or PSSNA-PA) Figure 4: Controlled chip placement onto solder before and after reflow. (Source: Panasonic System Solutions Company of North America-Process Automation, or PSSNA-PA)