GARTHWILSON wrote:
I'm laying out an '816 board. I thought of just soldering PLCCs directly to the board, but I would need space around them to solder them, meaning sockets wouldn't take any more room. Thru-hole sockets kind of precludes putting parts on both sides of the board right there, but SMT sockets cannot be hand-soldered. I'm also staying away from parts so small I'm not sure I could finish a board and not have soldering defects, so I don't think I want to try the PQFPs for this.
It is possible to hand solder SMT PLCC socket. With sufficient practice, the level of difficulty is comparable to hand soldering 0.5mm pitch QFP. I use a fine tip with 30 degree bend, Metcal STTC-026. The bend helps get around the plastic webbing of the SMT PLCC socket. SMT PLCC socket is bigger than PLCC IC, so you do need to allocate more space around a PLCC if you plan to use a socket.
BigEd wrote:
(We've mentioned before that PCB technology keeps moving on: for example, four layer boards are now much more affordable. In the same vein, I gather assembly is now affordable from some suppliers: they will deliver assembled, or partially-assembled, boards, if the parts in question are in their catalogue. I think it's worth considering this option, especially when there's some anticipated difficulty with some surface mounted components. A board which already has PLCCs or RAMs soldered in, and perhaps also tiny capacitors, maybe even sockets, can then be finished off when it turns up.)
SMT parts are generally cheaper and easier to obtain; pc boards with SMT parts are smaller thus faster & cheaper; and it is actually easier to solder SMT components than comparable through-hole parts once the soldering skill has developed. From cost point of view, if a designer is proficient with SMT soldering, I think an economical approach is to offer kits with SMT components already installed by the designer so the end users don't have to deal with SMT soldering.
Bill