what's the difference between these things and BGAs?
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Replying to @alt_kia
you don't have solder balls you have solid solder plates. in theory. in practice you have fuck all working because there's a bubble somewhere and you still need an x-ray to even discover it but then you can't rework the goddamn thing anyway
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Replying to @whitequark
wait so to confirm with BGA package, the solder balls *stay* as balls even after the thing gets soldered?
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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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once you can desolder those awful thin flat cable / flex PCB molex connectors without them yellowing or bending you're ready for almost anything. if you avoid connectors (or solder them with an iron) it's way easier though, ICs don't really care so long as PCB doesn't delaminate
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Replying to @whitequark @alt_kia
at least I've seriously abused passives and ICs and I have never actually destroyed any with hot air. plenty of PCB casualties though
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Replying to @whitequark @alt_kia
Relatively slow digital ICs are very hardy, analog parts can have parameter drift if overheated for _too_ long. Also I've seen at least one MEMS package pop, but there were extenuating circumstances. In general risk is low IMO.
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