I don't exactly understand your last question. As a bottom end, use a low temp (~100✬) electric oven to dry them before reflow. Avoid any contact with moisture while in stock. Water activity, yep, I had some bad experiences with PCBs and CIs. The board reflow procedure may use an infrared (IR) or a convection heating process. BGA components having noncollapsible balls (high-temperature solder 90 percent Pb/10 percent Sn, with a melting point of 302✬) typically will have few or no induced voids because the ball solder never melts during the reflow profile. Traditional lead-bearing solder pastes (such as 63Sn37Pb). Therefore, reflow profile development is important as a contributor to void formation. I have no direct experience with N2, sorry. Two options are available for reflow soldering of lead-free sphere BGA packaged components to printed circuit board (PCB) assemblies: Tin-based, lead free solder paste (recommended method). Be aware to isolate electrically each thermocouple to the copper layers. Try to use the smallest thermocouple possible. I've seen colleagues drilling the BGA itself too, but I would suggest this as a last resort. Yes, drill the PCB from the bottom side, right below the BGA. 5 After welding, lift the hot air nozzle up and remove the surface assembly board. 4 Turn on the heating power, adjust the amount of hot air, and start reflow welding of the BGA device. As a rule of thumb, keep BGAs with a clearance of at least 20mm on all directions. 3 Fasten the hot air nozzle on the BGA device, and be sure uniform distance around the device. It is recommended to understand these events during the PCB design stage with a careful placement. We've seen uneven temperatures close to high mass density components, such as ferrites, connectors, heat sinks, big electrolytics, etc. You must have access to X-ray machine for good analysis and several kits to burn, at least 20 to achieve trustable results.īlack bodies tend to absorb energy faster. I agree that without the right tools, knowledge and experience, it is a headache. The most accurate methodologies are destructive. The pads were constructed by immersion Au. The substrate was a FR4 laminate with pad diameter of 650 m, but a solder mask opening of about 850 m. Actually BGA are not more difficult to solder, but more complex to setup properly. Tweet Perhaps the most challenging components to thermocouple are BGAs, since the area of reflow is hidden underneath the component. Three sets of BGA solder joints, were prepared by assembly of the solder balls on the substrate which involved fluxing the substrate, placing the balls onto the pads and reflow soldering. You can expect the solder balls of a BGA package to shrink by about a third after reflow.For example, if the solder balls have a height of 0.3mm before. You might want to add some flux which will improve soldering but this is not a must. OK, let's go by parts (as Jack would say). In fact, if you add solder paste you will probably get some pins shorted.
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