EEVblog 1512 - Why Bypass Your PCB Like THIS? - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: November 02, 2022, 01:39:28 am
content: Why add bypass capacitors on a PCB like THIS?Answering a Twitter question:https://twitter.com/furan/status/1586889993234038786https://www.vgamuseum.info/index.php/cpu/item/993-s3-supersavage-ixc-sdr

author: Bud
author_rank: Super Contributor
timestamp: November 02, 2022, 04:18:15 am
content: PCB designers who do not know electronics ??Did I hear that right?

author: EEVblog
author_rank: Unknown
timestamp: November 02, 2022, 05:51:46 am
content: Quote from: Bud on November 02, 2022, 04:18:15 amYes, I knew several that came from a drafting background.PCB layout WAS drafting back in those days.

author: johnh
author_rank: Regular Contributor
timestamp: November 02, 2022, 08:56:51 am
content: The small company ( 5 people) that I worked at when I was getting work experience for the Certificate in Electronics back in 1978, had a pommy draftsman doing the PCB layout using Bishop tape

author: Kleinstein
author_rank: Super Contributor
timestamp: November 02, 2022, 09:02:42 am
content: If they have to stick to the rather large footprint with spacing, than the simple grid is close to the best one can do.There are still quite some 0 ohm resistors, that may or may not be required.In the 1990s there was a time when fast chip supposed to have even more than 1 cap per pin, but a whole sereis of 1 nF 10 nf 100 nF - I never really understood and at least with modern 100 nF caps in 0402 or separate GND and VCC planes, there is no really need for this anymore.

author: Fungus
author_rank: Super Contributor
timestamp: November 02, 2022, 09:43:56 am
content: Check for unconnected capacitors.If it was me I'd add dummy capacitors just to fill in the spaces if there were a couple of gaps left over after layout.

author: Brumby
author_rank: Unknown
timestamp: November 02, 2022, 10:49:52 am
content: Quote from: Fungus on November 02, 2022, 09:43:56 amAh ... Your artistic perfectionist is showing through.

author: EEVblog
author_rank: Unknown
timestamp: November 02, 2022, 11:42:13 am
content: Quote from: Fungus on November 02, 2022, 09:43:56 amAgreed, that would be compulsory on a grid layout like this.

author: Fungus
author_rank: Super Contributor
timestamp: November 02, 2022, 03:43:27 pm
content: Quote from: Brumby on November 02, 2022, 10:49:52 amEither that or my OCD.

author: free_electron
author_rank: Super Contributor
timestamp: November 02, 2022, 05:40:14 pm
content: Quote from: Bud on November 02, 2022, 04:18:15 amOh yes. Lots of them. The reverse is equally true... lots of engineers think they know how to do a board ...not ! dfm ? never heard of it .. what do you mean parts can crack if they are too close to the edge ? not my problem. Why cant i use smaller drills and place them closer ? WTF is CAF ? Can't you just slow down the conveyer to increase the barrell fill ? ok , ok i'll use a larger drill ... what do you mean the part now "pushes out" and why is there solder all over the topside ? can't you lower the wave pressure ? what is tombstoning ? what is head-in-pillow ? why do i have all these voids under my thermal pad ? can't you use a better paste that doesn't void ?The routing bit is the easy part... getting all other stuff right for production is a different story. sure, 1 or 10 boards is easy. try doing 10.000 boards or more a day with a maximum of 10 failures.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 02, 2022, 08:16:28 pm
content: (Just glancing in here, may be repeating some things.) Also familiar about that design, the via-in-pad suggestive of internal routing or planes. In particular I recall similar design practices on some old IBM network card (ISA Ethernet) I had, and on Tektronix boards particularly of the vintage of my TDS460. Especially for Tek I think, and, not sure about others, I think the priority for inner layer routing was a...reliability thing? Maybe frustrates RE too, I guess.Tim

author: thm_w
author_rank: Super Contributor
timestamp: November 03, 2022, 09:05:52 pm
content: Quote from: Kleinstein on November 02, 2022, 09:02:42 amThere are lots of 0 ohm yeah, definitely none of them are actually required as jumpers. Probably just placeholders for series termination, current measurement, etc.