Issue link: https://iconnect007.uberflip.com/i/1513827
60 SMT007 MAGAZINE I JANUARY 2024 Matties: When you come across a defect like that, what's your process to remedy it? What do you need to do? A lot of them can be repaired with hand sol- dering tools, for example, capacitors, resistors, miniport USBs, and the like. Other defects need more time and effort. For BGA repair, the process is more complex and more steps are needed (Figure 1). Matties: Do you have an average amount of time that you would spend on each board for rework? Is that three minutes? Maybe 10 minutes? For hand soldering, it could be seconds or a few minutes. Depending on the thickness of your board, it's recommended to prebake the board for some minutes. It's a fast process, maybe one or two minutes. Remove the com- ponents—that's maybe less than 20 seconds. en the technician performs a clean-up, and it probably takes more time to replace again. For BGA repairs, it will depend on the pack- age size and the board complexity. Aer the rework reflow profile is ready, the rest of the process could vary between 30 minutes to two hours. And again, it will depend a lot on the skills and experience of the rework technician. Matties: I'm curious if you have data on boards that have been thoroughly inspected with SPI vs. relying on process alone. Which ones need more rework? Is there a case to be made for every board and panel being inspected? It's not necessary in my experience. We do SPI as part of rework development from time to time when we want to collect the solder paste volume data, but this is not typically done when the process is mature. Microscope inspection is enough for the technician to be sure that all the parts have coverage with flux or paste. Matties: We recently interviewed a company that says they're not doing any SPI because they have their process dialed in so well. It seems to me that SPI inspection does not add much cycle time, and minimizes the poten- tial of scrap, or a lot of repair time. Are there other strategies for minimizing rework? One very good practice is to inspect the first article to be sure you don't have an issue in the SMT line; that will help prevent a lot of issues. I know many companies that do that. Johnson: First article inspection could also give the design team the opportunity to critique it and maybe even spin the board one more time to increase manufacturability. How important is the role of the design team in trying to drive rework to zero? I consider it very important, especially when a design is very risky. An example would be a board designed with BGAs on the primary side and BGAs on the secondary side, just under the other one. With respect to rework, that's taking a big risk when trying to optimize the space. Matties: I'm curious about no-clean flux and how the cleaning process plays a role in Figure 1.