Issue link: https://iconnect007.uberflip.com/i/1526114
24 SMT007 MAGAZINE I SEPTEMBER 2024 can be tested using rheometers, viscometers, and the like. Some jetting equipment suppli- ers are very involved in partnering with solder paste suppliers to optimize a solder paste for use in their jetting equipment. Jetted dot vol- ume, consistency, and repeatability over time are critical and must be tested using the jetting equipment. What are some common mistakes manufac- turers make when selecting solder paste, and how can they be avoided? Manufacturers tend to buy alternate solder pastes from their current supplier without an evaluation simply due to the need for a dif- ferent solder paste for a new PCBA or appli- cation. For example, if a new PCBA is to be built that includes smaller components than what are typically used, then Type 4 solder paste may not print adequately. Type 5 sol- der powder may be required, but the sol- der paste in use may not be optimized for Type 5 solder powder size. Unfore- seen issues can occur when using a sol- der powder that a solder paste was not designed for. It is also common for manufactur- ers to try existing solder pastes for alternate applications, which the solder paste was not designed for. For example, a manufacturer uses a solder paste in a standard print and reflow (SMT) application. en a dispensing machine is brought in to run specialized PCBAs, e.g., proto- types. e natural next step is to use a "dispensing version" of the print- able solder paste. Again, unfore- seen issues can occur because the solder paste was not formulated for that application. Another common mistake is for manufacturers to bring in an alter- nate solder paste with the goal of improving the process, and run it on a random PCBA that happens to be going through the line. e PCBA may not be challenging and may not show any dif- ference in solder paste performance. is typi- cally results in the manufacturer continuing to use the current solder paste and living with the disadvantages of it. Using an evaluation process is the ideal way to select a solder paste. Solder pastes should be evaluated and compared to existing solder pastes in the same application. If PCBA defects are the reason for acquiring another solder paste, then the evaluation should include test- ing on the PCBAs that show the defect. Quan- titative data should be gathered, and solder pastes ranked according to performance. In some cases, the data is weighted by category to give more value to what is most important to the user, and devalue the less important cat- egories. For example, a solder paste is evalu- ated for pauses in printing and voiding perfor- mance, but pauses in printing rarely occur in the normal production environment. en the pause in printing score may be weighted lower than voiding perfor- mance. Solder paste evaluations can be quite detailed and creative, including sup- plier details, shipping time, shelf life remaining when received, sten- cil life, various printing categories, various reflow categories, flux resi- due characteristics, and many other desired properties. Evaluations that give quantitative scores help manu- facturers to choose the best solder paste for their application. How do you foresee advancements in solder paste technology affect- ing the electronics manufacturing industry in the coming years? Solder paste technology is always progressing, including flux and solder alloy advancements. Flux advance- ments are targeted at solder paste performance improvements, and