Issue link: https://iconnect007.uberflip.com/i/1526114
22 SMT007 MAGAZINE I SEPTEMBER 2024 Solder paste gives optimal performance a few days aer manufacturing, and solder paste performance degrades with age. Storing sol- der paste sealed in the original packaging in a cooler reduces the reaction rate between the flux and the solder powder and extends the performance life. Temperatures higher than refrigerated tem- perature, air exposure, and mixing all acceler- ate chemical reactions within the solder paste. ese reactions decrease the performance of the solder paste to the point of becoming unus- able in extreme cases. Some solder pastes are more "reactive" than others, which may lead to shorter shelf, stencil, and working life. Proper storage and handling are critical for these solder pastes to extend the performance life. Could you share some insights on how to evaluate the compatibility of solder pastes with different soldering processes and equipment such as jetting? Evaluations of solder paste for an application like jetting typically start by using the solder paste in the equipment on a test PCB. is is sometimes called alpha testing. is can be done internally if the solder paste manufacturer has the equipment, or externally at an equip- ment manufacturer or a user of the equipment. Ideally the candidate solder paste is tested and compared to an existing solder paste that is used in the application. If any incompatibility is found with the solder paste in that applica- tion, then alternate solder pastes may be eval- uated, or a new solder paste formulated. e alternate or new solder pastes will go through the same initial testing (alpha) in the process/ equipment. Once a solder paste is found to be compati- ble in a process, then the next stage is to have the solder paste tested at a PCBA manufac- turer (beta site). is normally involves using the solder paste on "real" PCBAs. QC inspec- tion of the PCBAs may be more intense than standard production quality control to be sure the candidate solder paste is working well. Again, it is best to compare the performance of the candidate solder paste to an existing sol- der paste for that process. e way to measure compatibility of a sol- der paste with a process/equipment is deter- mined by the application. In the case of jet- ting, solder paste must function with smaller solder powder sizes like Type 6 or 7. e rhe- ology of the solder paste is key for jetting, and