copper traces to nowhere on MSI motherboard

Just to clarify.

If it was an antenna then it certainly would not have had a guard track
on the outside.

Sorry Paul, I didn't say it was an antenna, funny place to put one I
must admit..... I did say, "if it was and antenna", just to clarify.


The shape has gotta to be adding either coupling, inductance or
capacitance... they wouldn't do it to make the board look pretty, no
vias means no connections.

davy

On 12/15/2012 4:27 PM, davy wrote:
Just to clarify.

If it was an antenna then it certainly would not have had a guard track
on the outside.

Sorry Paul, I didn't say it was an antenna, funny place to put one I
must admit..... I did say, "if it was and antenna", just to clarify.


The shape has gotta to be adding either coupling, inductance or
capacitance... they wouldn't do it to make the board look pretty, no
vias means no connections.

davy



Small brain fart time,

I remember some folks that chased 'easter eggs' inside integrated
circuit chips. Art in the Art. maybe this is a case of someone
designing a PC trace as an 'easter egg' ? Just because they could?

hp wrote:
On 12/15/2012 4:27 PM, davy wrote:
Just to clarify.

If it was an antenna then it certainly would not have had a guard track
on the outside.

Sorry Paul, I didn't say it was an antenna, funny place to put one I
must admit..... I did say, "if it was and antenna", just to clarify.


The shape has gotta to be adding either coupling, inductance or
capacitance... they wouldn't do it to make the board look pretty, no
vias means no connections.

davy



Small brain fart time,

I remember some folks that chased 'easter eggs' inside integrated
circuit chips. Art in the Art. maybe this is a case of someone
designing a PC trace as an 'easter egg' ? Just because they could?


You'd be fired pretty fast, if you did that today.

The thing is, too many people get to inspect your work
and comment on it, before it gets into production. Whether it's
a PCB design, or a chip design, it's pretty hard to hide something
like that and get away with it.

In our chip fab, we had an inspection process, that included
a "public display" of your handiwork. It allowed virtually
anyone in the fab, to notice visual defects in designs. And
they did find things. That's what used to amaze me about the
whole process, is the amount of errors that were found by
other designers casually glancing at the finished design. So
the public display idea, was an approved technique for
improving chip quality. (This was back in an era, when the
geometry wasn't quite as tiny as it is today. The plot would be
too big, to display a 3 billion transistor chip. It would cover
the entire employee parking lot, and waste way too much paper.)

*******

That structure was put in that PCB for a purpose. If I were to
do that at work today, I'd have to get two other people
(Library guy and layout guy) in on it, so right there,
two other people know I'm screwing around. So five minutes
from now, my boss knows. And later, we'd get a call from
the PCB shop, asking us if we were serious about that squiggle,
and could they remove it. So lots of busy-bodies would find out.
That squiggle was "signed off, up and down the line".

I had a guy at the PCB shop, actually *change* one of my
designs, without telling me. So sometimes, these guys get
a little carried away. You wouldn't get your Sparkle Pony
drawing past *that* guy at the PCB shop. Five minutes later,
he's phoning my boss.

Paul

One thing though.
Covering as much copper area as possible saves on the etchant... makes
it last longer, sure wouldn't get as 'slushy', I had some Ferric
Chloride that lasted well over a year it became like soggy porridge, I
don't know about the other stuff, Sodium Persulphate.

Merry Christmas all and have a Happy New Year!

davy

davy wrote:
One thing though.
Covering as much copper area as possible saves on the etchant... makes
it last longer, sure wouldn't get as 'slushy', I had some Ferric
Chloride that lasted well over a year it became like soggy porridge, I
don't know about the other stuff, Sodium Persulphate.

Merry Christmas all and have a Happy New Year!

davy

Yes, but there are fill patterns (crosshatch or lattice) you
can use for that. The layout guy is supposed to balance the fill of
copper on the layers, so that there is less warping in
processing. If you put "air" on one side of the board, and
a solid copper (unetched) plane on the other side of the PCB,
it'll warp on you, and be bowed in the center. And the stackup
is also supposed to be symmetric. There's lots of symmetry in
PCB design requirements.

http://www.multi-circuit-boards.eu/e...r-balance.html

We actually had a guy at a local PCB shop, who'd come in and give
a lecture on PCB design. Lasted about two hours and an excellent talk.
PCB shops give a fair amount of feedback, which helps ensure less
loss of productivity because someone isn't familiar with the details.

*******

I used to use the ferric chloride at home. Never had a problem with it.
Just don't dump it down your copper plumbing pipes :-) I used to
etch in styrofoam meat trays. So the trays that hamburger comes in,
you save those and they can be used for etching PCBs.

The largest PCB I ever did at home, was for a keyboard. I built
my own keyboard, for my first computer. The PCB was double sided,
but being a "home manufacturing" process, there were no plated holes.
So if you did a "via", it meant inserting a wire, and soldering it top
and bottom. When soldering, you'd do the vias first, then populate
the components.

The hardest part of the keyboard project, was getting the key assembly
(unit with a couple hundred "legs" on the bottom), to line up with the
holes in the PCB. What a nightmare. But, I eventually got it aligned
and plopped into place. The circuit on the PCB was a keyboard matrix
scanner (so one big chip does the circuitry).

The weakest link, in my home PCBs, was protecting the copper. I've
had corrosion on some of those PCBs so bad, it ate right though
the tracks (takes about ten years to happen). In school, we
had a plating solution (AgNO3 based), that you'd apply after etching.
That would put silver plate (electroless) on the two sides of the PCB,
and provide some protection. But that solution, isn't something you'd
use at home (poisonous). The brew was home-made by the techs in the shop,
and as well as silver nitrate, it also had a hint of, I think it was
sodium cyanide. There were a couple other compounds added for stability.
The solution did a pretty good job, considering the crudeness
of the process. Those PCBs would likely last longer than the
ones I made at home. Silver nitrate by itself wouldn't give you
a good plating job, but the additional chemicals gave a "fine"
deposition. If you used silver nitrate by itself, you'd likely
get flakes deposited.

Paul

A day or so ago I was reading somewhere on the net... they actually do
this, fill blanks areas to balance the board - to stop it from warping,
I thought of fiber glass, now that's gonna take some warping, could be
it's something that carried over to when they started to use glass
boards, this is new to me.

Some Hitachi CRT TV sets were a pain at warping right across the middle,
the heavy stuff, transformers and such were sat on a plastic frame at
that, mind you this wasn't glass board, many was truly visible. they
sagged that bad.

PCB designing is a art and job in itself with loads of rules to follow.

davy

On Sat, 22 Dec 2012 05:26:12 -0500, Paul wrote:


The weakest link, in my home PCBs, was protecting the copper. I've had
corrosion on some of those PCBs so bad, it ate right though the tracks
(takes about ten years to happen).

The easiest way to do that, of course, is to solder plate the copper.
Most of the fast turn PCB houses will do that for you. A high
reliability commercial board will have something more elaborate such as
ENIG (electroless nickel under immersion gold). A few years ago, some
vendors were having trouble with the ENIG process where the nickel got
contaminated during the process and you ended up with what was known as
'black pad', where the nickel-tin bond would fracture; this was a
particular problem on BGA balls where you could not inspect for it. We
switched to immersion silver for a short time, but that was a case where
the solution was worse than the problem.. ANY improper handling of the
board would cause severe solderability issues. We quickly went back to
ENIG with a trusted vendor, and have not had any issues since.

Of course, for years, almost all boards were treated with HASL (hot air
solder leveling). Some fabricators abandoned HASL due to RoHS concerns,
but there is a lot of focus on lead-free HASL processes today for
commodity circuit boards. We don't use it, because what we make is not a
low cost commodity.

David wrote:
On Sat, 22 Dec 2012 05:26:12 -0500, Paul wrote:

The weakest link, in my home PCBs, was protecting the copper. I've had
corrosion on some of those PCBs so bad, it ate right though the tracks
(takes about ten years to happen).

The easiest way to do that, of course, is to solder plate the copper.
Most of the fast turn PCB houses will do that for you. A high
reliability commercial board will have something more elaborate such as
ENIG (electroless nickel under immersion gold). A few years ago, some
vendors were having trouble with the ENIG process where the nickel got
contaminated during the process and you ended up with what was known as
'black pad', where the nickel-tin bond would fracture; this was a
particular problem on BGA balls where you could not inspect for it. We
switched to immersion silver for a short time, but that was a case where
the solution was worse than the problem.. ANY improper handling of the
board would cause severe solderability issues. We quickly went back to
ENIG with a trusted vendor, and have not had any issues since.

Of course, for years, almost all boards were treated with HASL (hot air
solder leveling). Some fabricators abandoned HASL due to RoHS concerns,
but there is a lot of focus on lead-free HASL processes today for
commodity circuit boards. We don't use it, because what we make is not a
low cost commodity.


Yeah, we used HASL too.

And the boards we made, were "armor plated" in terms of quality.
Very hard to damage them with clumsy soldering iron work. Not
like the motherboard I tried to repair here at home.

I realized when I was making home made boards, that they
weren't the best. But what came as a surprise, is how
much they suffered over the years. I never expected the
degree of corrosion I was seeing, with the bare copper.

Paul

... or use clear protective lacquer that you can solder through such as
Electrolube ERCPL200H

davy