Why is the circuit so squiggly?

Hi all,
Something that's been bothering me for years (I clearly have no life)...

Why are traces on  printed circuit boards sometimes very squiggly, when there's an obvious shorter, straighter path.

I've attached a picture of a PC RAM card that shows what I mean.


Picture of Why is the circuit so squiggly?
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Time; it may be a small unit of time, but a signal takes time to travel through a circuit.

In fast switching synchronized circuits a signal leaves one point and must arrive at different points at the same. If the wires are different lengths the signal arrives at the different points at different times.

The squiggly wires assure the signal coming from one point arrive at the different points all at the same time.

Morgantao (author)  Josehf Murchison6 months ago

Yeah, that's what I suspected.

Seems like each trace goes to one of the memory chip's leads, and since they all start at the bus bar at the bottom of the chip (Not seen in the picture), it would make sense to make the closer ones take a longer path.

Is time a measure of current motion OR is current flow a measure of time ?

Time is a creation of convenience.

Is that why when your rushed there is never enough and when waiting for something it expands forever?

iceng rickharris6 months ago

TIME is like a river and you couldn't step into the same river twice..

Unless you walked down stream at the same speed as the river.

Close: Zen Buddhism Philosophy

"Time is like a river, you cannot step on the same water twice."

Thanks, I was referring, to a memory, of a Second City or Beyond the Fringe old time radio comedy sketch where a bunch of unemployed philosophers were meeting agaraff at an Italian riverside bistro and one said ;

"Time is like a river, you cannot step on the same water twice."

Where one zany philosopher was heard to say that ;

"unless there is a water bug going upstream at the same speed as the river flows down." When another commented ;

"but the water skater would be older and therefore be a different bug."

When the concept of a going down stream at the same speed as the river was presented.. Whereupon a philosopher tossed a log into the river, to see how fast it was flowing. Then he ran and stepped into the river by the log, ran and stepped into the river, ran and stepped..... Eventually ran out into the Aegean Sea and was drowned !

The conversation then moved on to Zeno's Paradox, as I recall..

Kind of looks like they are trying to keep all the tracks the same length. What sort of device is the board out of?

Ok I didn't read your question properly its a ram card.

Basically, the wiggle is used in situations where there are two or
more (fast) signals that should be synchronized, so that they are not
delayed relative to each other due to different track lengths.

This is extremely important for signals that have a clock line
because, for example, on a system with various data lines, if some of
the data lines are longer than others, when the clock pulse occurs it is
possible that not all the signals have reached the receiver for the
data being transmitted.

On the image you can see that the inner tracks are the ones that are
wiggled, because if they were straight they would be shorter than the
outer ones.

But I guess some of the wiggles on this particular board are also to prevent stray inductivities.
Apart from getting a proper length for the timing signals the wiggles also make sure the trace is not acting like an antenna in this particular area.
So instead of a straight trace allowing a signal to build up, the wiggles cause the signal to cancel out on itself.
Can't find the link anywhere now but was on a website some time ago that showed how microprocessors evolved over the years.
On some of the enlarger CPU pics you could find similar wiggles.
When we use quite high frequencies to drive our CPU or Memory signal quality is often the hardest part of the entire design process....

Morgantao (author)  Downunder35m6 months ago

Downunder35m, that makes sense, to some extent, but if look at Bluetooth and WiFi antennas, you often see they are kinda squiggly themselves. The squiggly part can also act as a booster, so the antenna could be shortened to fit in a mobile device.

That said, I guess whoever designs the squiggly parts on both antennas and computer chips knows what they're doing :)

iceng6 months ago

Don't forget there are other layer traces to contend with and it is desirable to avoid static and inductive coupling.. Putting a ground plane between each layer gets too expensive.

Besides this was designed by an engineering of Nazca descendant :)

steveastrouk6 months ago

It takes a finite time for the signal to travel down the line. The speed of light is roughly 300mm/Nanosecond, in vacuum. On FR4 laminate, it might be 150mm/nanosecond. Not insignificant at RAM clock speeds.

rickharris6 months ago

Most circuit boards are calculated by a computer program. There may be reasons for the "squiggles" e.g. it could be some kind of antenna (aerial) for communications, it may be a low value resistor or it may be maintaining separation between high voltage and low voltage sides of the PCB.

The board may be several layers thick so the squiggles may be going round other tracks you can't see. In general if the tracks could be shorter and straight they would be.