Re: Dark deposit on pins near leaking SMD electrolytic caps
Physically, one layer, copper on top.toggle quoted messageShow quoted text
inner layer (* see note)
outer layer, copper on bottom.
That inner layer can be single sided or two sided, depending. I don't think that anything in the manufacturing process keeps it from being so. I've actually made 3 layer boards, although they're quite awkward without plated through holes.
One side of that inner layer can be missing, so yes, a 3 layer board. I guess it was cheaper to make for some reason, but that was then, long ago (in electron lives) then...
On 2/9/2021 11:33 PM, Jim Ford wrote:
3-layer boards? Never heard of them. Maybe you mean 3 dielectric layers and 4 metal layers? PCBs are built up from the inside out, starting with a core (fully cured dielectric sheet plated on both sides with copper foil) and adding more cores and/or prepregs (partially cured dielectric sheet plated on one side with copper) symmetrically on both sides until the stackup is done. Hence there is always an even number of (metal) layers. Always!