On Tuesday 01 February 2005 09:27, Roy J. Tellason wrote:
> On Tuesday 01 February 2005 09:30 am, Stefan Trethan wrote:
> > Dunno why they must torment us with such impossible packages.. What do
> > they want? Even smaller mobile phones? They need to ship them with
> > tweezers soon... Oh well, i guess a nice "phone enlarger adaptor"
> > aftermarktet.
A number of years ago, I designed a nice little "walky-talky" arrangement for
my wife and I to use when travelling on our motorcycles. Small little
package, clipped onto our helmets, VOX, walkman input, and so on.
Part of this of course required a headphone amp to drive some little speakers
mounted in the helmets.
Went to the National Semi site, did the parametric search and came up with a
suitable candidate. Went to Digikey, there it was, ordered a few.
When the order showed up a few days later, one of the plastic pouches was
empty ! The one with the headphone amp. I was about to get on the phone to
Digikey shipping and whine when something in the bag caught my eye. Closer
examination revealed that it was not a small spec of lint in the bag, but
there was in fact an IC in there.
Back to the NatSemi web site, to the end of the datasheet, stared at the
dimensional info and there realized my mistake. The dimensions I thought to
be in inches (with the decimal point mentally misplaced) were in MILLIMETERS.
I have now added a new criteria to the parts decision. Aside from function,
power, price, availability and so on,
the thing cannot be invisible.
If it's invisible, I have to continue looking. That's my new rule.
Alas, even the days of visible parts are numbered. I went to a seminar on PCB
design done by IBM about 10 years ago. At that time, they passed around a
part that looked a lot like a gull-wing RF transistor. Only the leads were
obviously not any metal I'd ever seen .. they looked almost like mylar,
giving off a weird moire effect when the light struck them just so.
Only under a microscope was it shown that the thing was an IC, with LOTS of
THIN leads coming out each side. The exact numbers escape me, but I think
the leads were .001" wide on .001" centers or something ridiculous like that.
Most of the crowd wanted to know how IBM produced a PCB to support a device
with that fine a pitch; I wanted to meet the poor R&D guy who had to solder
the first one to the prototype.
Alan
--
Alan Rothenbush
Academic Computing Services
Simon Fraser University
Burnaby, B.C., Canada
Before me things create were none, save things
Eternal, and eternal I endure.
All hope abandon ye who enter here.