![]() The "seasoning" aspect I came up with because I imagined that while there is a timeframe after which the applied paste is not useable anymore, there might be chemicals in there that make the paste easier to apply that might also cause this if reflowed immediately. Before using stencils I tried that once and it didn't create good results for small footprints for me like qfns. I have seen people manually applying paste for larger packages by just putting it on there in one pad-crossing line, as someone mentioned. I suspected the excessive spreading out to be unfavorable because it creates more stray solder particles left to be cleaned out and I have seen this more "sintering" looking like reflow process in more professional videos, as opposed to the running away of the paste. But my question wasn't really about my issues, but a general question based on the material I habe seen online. The datasheet for reference: I currently do have some bridging but it is due to my no experience and the stencils. Yes, of course! I'm currently using CHIPQUIK TS391SNL50 (SN96.5, Ag3.0, Cu0.5 with T4 balls). ![]() Is that a thing? 6) Different heating method? Oven (resistive heating with convention or no convection), IR, vaccum? It is a bit difficult googling this as google steers you towards the actual reflowing/melting temperature of the solder. (Temperature-wise mine is at room temperature when applying it) 4) The amount of paste (I have checked with my microscope, and it is not more/thicker than in the videos I have seen where it does not spread out) 5) "Seasoning" the paste by letting it rest for some time after application. 3) Different angle, speed and force when the paste is spread out over the stencil. 2) Different reflow profile, as in it stays longer or less in certain temperature ranges. Possible explanations for me: 1) Different paste. I'm currently just reflowing with hotair from below the board. I, too, have not managed to do this and instead always ended up with situation 1). ![]() I see 2) as more favorable as it reduces the chance of bridging, as well as less cleanup (because of less stray solder paste balls on the board). It immediately becomes this matte, dry paste, without spreading out and then reflows. Looking at paste reflowing videos on YT, I see two categories: 1) Where the paste spreads out (heavily) onto the solder mask during reflow and is then pulled back- 2) Where the paste does not spread out during reflow. Hello, I have been doing my first steps using stencils and paste, and I have a question I would like to ask, and some thoughts that came to mind as I tried to find reasons on my own. ![]()
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