RE: Cat Box

> Speaking of PLCCs. What are your thoughts on using SMT in small runs
> for
> things like vectorlist projects. DIPs are easy to assemble. PLCCs and
> other
> SMT devices in through hole sockets are, well, basically DIPs. But for
> small,
> <50 unit runs, can SMT be employed effectively? Can you imagine a CAT
> box with
> a BGA inside! I doubt it would be worth (or cost effective) sending
> them
> overseas. Have you considered this technology for any of your
> projects?
>
:-) Kev and I just had this discussion...

The obvious advantage of DIPs is that most anyone can work on them with
a minimum of fuss. For my projects, a lot of the cost can come from PCB
area, so making something surfacemount is desirable from a cost
standpoint (smaller PCB).

All is not rosey with surface mount though... By and large surface
mount parts are more expensive to buy in small quantities for
hobbiest-type projects. Then there's the problem of getting them on the
board. Not everyone has a reflow oven or Mantis microscope. :-)

I used surface mount ROMs on the Star Wars/ESB 3.1 kit and soldered
directly to the board. My experience has been that any surface mount
socket that's worth using is probably too expensive to buy. ;-) I've
got a 44 pin PLCC on the MultiPac which I have socketed for now with
some pretty nice looking through-hole sockets. We'll see how it
works...

I've got surface-mount rework stuff here at work which makes it a little
less of a pain to work on, but fine-pitch parts still suck to do by
hand. Having special PLCC/surface mount removal tips for your soldering
station is almost a necessity for surface mount work. (We have Metcal
irons here at work which are really nice, but spendy.)

The other downside of fine-pitch surface mount is that it's too fine to
run traces inbetween pins. That can make a two-layer board a lot bigger
(or push up the via count which increases you drill-hit charges).
Surface mount PLCC's are nice though-- still big enough to run traces
between pins, and no drill hits for the package which helps
manufacturing costs (at least on protos).

I still think it would be cool to make a "two-chip" Tempest or Ms.
Pacman out of a big FPGA and main CPU... ;-)

Diamond has an older pic and place machine that I think would be cool to
drag up here to Vancouver for ... Uhhhhh... Prototypes for
engineering... yeah... that's it... The shop next-door had a reflow
oven... I could almost do one-stop surface mount production without
having to spend big bucks. (Most outside shops charge on the order of
$12-20 per board to assemble something of ~100 part complexity. My
stuff's been small enough that I never bothered to have anyone quote
it...)

-Clay
Received on Tue Jul 21 17:51:24 1998