BigDumbDinosaur on Thu 6 Jan 2022 wrote:
90 degree corners in traces were an invitation to disaster.
Did that preclude designs where three wires meet at a point? With octagonal routing, two or more wires must meet at 90 degrees or worse.
AndrewP on Thu 6 Jan 2022 wrote:
90° bends could cause single integrity problems. I had no idea it was actually an old manufacturing process issue. In fairness I might have been told this by a radio astronomer as the department I was with had strong ties with the Hartebeesthoek Radio Telescope.
There was an amusing flap when physicists thought they detected particles going faster than the speed of light. They were quite thorough with equipment checks and measured all of their cable lengths quite accurately. I thought they programmed an FPGA wrong and latched timestamps from a rippling counter. However, the root cause was far more mundane. A corroded antenna cable caused signal skew on the GPS receiver.
It is plausible that similar problems could occur with poor etching.
plasmo on Thu 6 Jan 2022 wrote:
The "no 90 degree acid trap" prohibition was a valid concern in the last century, but not an issue anymore.
If the constraint isn't too onerous, is it worthwhile to follow? It would make a more robust design and possibly permit home etching.
plasmo on Thu 6 Jan 2022 wrote:
You can verify that by zooming in the image and see the corners of 7 mil traces are not over-etched.
I get uneasy about two row IDC and 20 wire per inch ribbon cable. 7 mil traces with equal spacing is 70 traces per inch.
plasmo on Thu 6 Jan 2022 wrote:
It is a rule that every board designer follow (except a few black sheep).
See username.
plasmo on Thu 6 Jan 2022 wrote:
It is like the "must wearing jacket in fancy restaurants" rule that everyone just follow.
Possibly elsewhere, I may write about my visit to Claridges dressed as a pink fairy. Shortly after that evening, someone was ejected from the wine bar for wearing a kilt. Tourist. For my experience, the staff are far more tolerant if a party orders £4000 of champagne.
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