3/11/2024 0 Comments Lead free solder reflow profileGranted, I didn't try doing the same thing with parts in BGA package - for those you will probable need some glue. Surface tension of molten solder is quite strong and keeps all these parts in place. I don't use any glue to hold bottom parts in place during second reflow, and so far no part has came off - I had everything from tiny 0201 to quite large "type D" (size 2917 IRC) sized parts (see first photo). Again, my comment was mostly referring to manual soldering of thru-hole parts after reflow. Once that is done, I make standoffs using M3 screws with some nuts, and then place components on the top side (take note of screws I used to make standoffs): As you can see, the top side has many parts, so by the time I placed them all the board will long be cooled down to ambient temperature. My board has only passives on the bottom side: So I place bottom side parts first and then reflow them. It's also often used for non-FR-based boards some of which are very sensitive to heating. Now - there is Bismuth-based low-temperature lead-free paste, but as far as I understand it is not recommended to be used for production - only for prototyping or repair/rework. But again, unless you absolutely have to use lead-free process, I'd suggest you to stick to leaded one as it's much more forgiving and has lower melting point. And when you do manual soldering, always leave enough time for things to coll down between repeated heating. As long as you don't overheat your board, internal structure (and thus trace impedance) will not be affected much my soldering, but I strongly advise against manual soldering unless it's absolutely necessary (like for thru-hole connectors). Quote from: asmi on January 07, 2018, 07:48:13 pm If you plan to do a reflow (even 2 reflows for double-sided placement of parts) as a primary soldering method (some manual soldering of thru-hole parts are OK), in my experience even cheapest Tg130 FR4 is going to be just fine for lead-free profiles. If you plan to do a reflow (even 2 reflows for double-sided placement of parts) as a primary soldering method (some manual soldering of thru-hole parts are OK), in my experience even cheapest Tg130 FR4 is going to be just fine for lead-free profiles.
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