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While it’s still hot wipe it with a paper towel to take away any residues. In fact, you'll be able to in all probability just warmth the board and wipe it with a wad of paper towel that you dipped in your flux+solderpaste mixture.
And for many designers, going from 250 micron diameter PTV to 350 and even four hundred micron diameter PTV isn't practical. When speaking about PTVs and failure, the primary mechanism of concern is barrel fatigue. Barrel fatigue is the circumferential cracking of the copper plating that types the PTV wall. The fatigue happens due to the differential growth of copper plating (~17 ppm/˚C) and the printed board (between 45 to seventy five ppm/˚C). The knee is the transition space from the pad to the wall.
IPC 6013 has far more stringent requirements for the knee space than the wall. For example some small plating voids are allowed within the side wall space for a Class 1 and Class 2 circuits, but zero voids are allowed in the knee space for both of those lessons. Check together with your producer for his or her minimal drill dimension and minimal annular ring for the manufacturing process they will use.
As for tinning, the chemical mixtures are a little bit of a pain to get. When the board comes out of the printer, it’s solely coated in ink. But despite the attention, PTV architecture truly has the least influence, especially given the realistic limitations with regard to what you possibly can change. For instance, moving from 250 microns to 300 microns diameter on a 3 mm board, 50˚C temp cycle, will lead to approximately 20% enchancment. That’s nice, nevertheless it doesn’t actually give you the sort of margin that makes the issue go away fully.
While many diagrams depict the knee as a nicely-outlined point, it is truly a radiused space. The knee is an important space to view as a result of many times plating adhesion points will manifest themselves as cracks at or around the knee.