yes indeed. you can see them if you look at the side of the package with bright illumination. they get kinda squished but retain the overall ballness.
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Replying to @whitequark
ahh ok. but if they're allowed to melt why don't they become flat? is it just that there's not enough metal area on the BGA package and the solder prefers to stay as ball rather than flat? or something else?
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Replying to @alt_kia
precisely. solder has a very high surface tension (ever seen mercury? solder is basically the same over liquidus temp) and balls up anywhere it doesn't wet a surface, since that minimizes surface energy
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Replying to @whitequark
ty for explaining all this, i've never worked with any surface-mount parts
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Replying to @alt_kia
SMD can be easier than PTH even, and BGAs are easier than QFN and QFP. SMD parts self-align and can be reworked regardless of the number of pins
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Replying to @whitequark
i see how do i get started with these parts, what equipment do i need
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Replying to @alt_kia
i use stencils and vapor phase soldering personally but that's overkill; solder paste in a syringe and a hot air gun are sufficient for many jobs. i suggest getting junk PCBs and trying to rework random components on them without turning the PCB into char or melting stuff
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Replying to @alt_kia
using phase transition of a fluoropolymer liquid (Fluorinert) as a sort of thermostat. instead of an IR oven with a PID controller you rely on the fact that latent heat of condensation >> heat transferred by convection and radiation, and...
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Replying to @whitequark @alt_kia
the liquid only condenses on cold spots of the PCB. unlike IR reflow, VPS can rapidly heat the entire PCB to nearly exactly the same temperature even if you have componets with wildly different thermal mass, material, and reflectivity. it's amazing.
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the liquid is like 50 EUR per 100 ml though
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