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the components held in position by a multi- axis articulated robot equipped with a rotary vacuum head. A key issue when re-tinning fine-pitch sur- face mount devices such as QFPs and no-lead QFNs is to maintain coplanarity across all leads to ensure consistent solder distribution and limit the potential for bridging. X-ray flu- orescence (XRF) testing can be used to ver- ify solder thickness, in addition to alloy com- position, when determining if a coplanarity issue exists. Fine-pitch QFPs pose certain challenges but can be successfully tinned with proper process controls in place. ese components may range from 6 mm x 6 mm up to 50 mm x 50 mm with a lead pitch as small as 0.012" making the margin for error very small. Given the tight spacing and delicate nature of these leads, there is the potential for bridging and lead damage when tinning these types of components. Using a controlled automated system with these fine-pitch components will provide significant improvement in achieving consistent and reliable outcomes with limited defects. Following the robotic hot solder dip pro- cess, all re-tinned devices should be cleaned in a batch wash or cleaning system, using the appropriate solvent or aqueous cleaning agent to remove any residual flux r esidues. S ubse- quently, components should be dry baked for the applicable component moisture sensitiv- ity level (MSL). is s hould b e f ollowed b y solderability testing per J-STD-002. Ultrasonic cleaning is another common cleaning method that should be used cau- tiously. Semiconductor devices can be poten- tially damaged by cavitation resulting from certain frequencies in ultrasonic cleaners which is unsuitable for cleaning electronic components. Ultrasonic cleaners meant for other applications, such as cleaning of small mechanical parts, should not be used for cleaning these components. If an ultrasonic cleaner is used, it should be a continuous variable frequency (CVF) type designed spe- cifically for cleaning of electronics. In conclusion, the component lead tinning process is essential for enhancing solderabil- ity and ensuring the reliability of electronic assemblies. While traditional manual meth- ods using a single static solder pot may seem cost-effective, they are fraught with challenges that can negatively impact the quality of work, including the transfer of contaminants and the creation of de-wetted solder joints. To achieve optimal results, employ- ing advanced techniques like the robotic hot solder dip process is strongly recom- mended. is method provides better con- trol over the re-tinning process, safeguards against contamination, and ensures a con- sistent, high-quality intermetallic bond. By adhering to industry standards and utilizing proper equipment, manufacturers can signif- icantly improve solderability and reliability, ultimately leading to more dependable elec- tronic components and assemblies. SMT007 Future columns will delve deeper into each aspect of the lead tinning process, providing further insights, and best practices to enhance quality and performance in the assembly of electronic devices. Nash Bell is president of BEST, Inc. To read past columns from this company, click here. 76 SMT007 MAGAZINE I APRIL 2025 Nash Bell