Electrolytic Capacitor Silkscreen - Page 1
Forum section: electronics / general

author: JtroTechAB
author_rank: Contributor
timestamp: October 29, 2018, 05:02:33 am
content: What is the IPC standard silkscreen or PCB marking for electrolytic capacitor.

author: JtroTechAB
author_rank: Contributor
timestamp: October 29, 2018, 10:17:50 am
content: what is the correct way to show the silkscreen or pcb marking of electrolytic capacitor in order to show its polarityanyone, any replies?

author: Gribo
author_rank: Frequent Contributor
timestamp: October 29, 2018, 01:58:40 pm
content: Usually (from LP viewer 10.5), it is a filled circle near pin 1, and a component's outline that has chamfered corners near pin 1.

author: floobydust
author_rank: Super Contributor
timestamp: October 29, 2018, 03:13:42 pm
content: I see many different styles for polarity marking. This is what I use.Most important is you can see the polarity marking outside the capacitor, after it is installed.Altium wrongly uses the part outline as a square.So component placement (clearance rule) gets all messed up with circular-shaped parts.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 29, 2018, 08:02:46 pm
content: IPC doesn't care about silkscreen; 2221A says to reserve space for designators and not to hide information under components, but doesn't make any statements about what a component should look like.It's perfectly producible to leave minimal silk. 80s Tektronix had hardly any: rare if any designators even, mostly a plus to indicate polarized capacitors. Modern high density builds don't afford much space to silkscreen, for obvious reasons.Personally, I use a circle with a plus to one side and a minus on the other (actually an arc segment, mimicking the polarity mark on the sleeve). The half-shaded style is fine too, and there's a concentric arcs style I think that's more European in origin.I don't like the half-solid style, the white balance is just so awful. But as you can see, that's an aesthetic statement, nothing more technical than that.Tim

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 29, 2018, 08:18:15 pm
content: Yes there is no "right" way to do it.I usually just put a "+" near the positive pin. The rest depends on the size of the cap and the density of the board.The cap's "shape", or outline, on silkscreen is only useful while routing the board (in which case it can be put on another layer instead of silkscreen) really. It doesn't add any value (except maybe aesthetics? that's all relative) after that.Again, once the caps are assembled, there are marks on them so any marks on silkscreen are basically useless at this stage, except maybe the polarity mark which can help visual inspection (although that can be done with reference pictures or even be automated).

author: tycz
author_rank: Regular Contributor
timestamp: October 30, 2018, 12:21:48 am
content: Quote from: SiliconWizard on October 29, 2018, 08:18:15 pmIt's useful for the factory worker who stuffs the cap into the board and the technician who repairs it when it fails. It's also good idea to put a large marking around the negative pin. This makes it very easy to identify a correctly placed cap by visually matching it with the big negative stripe on the body of the cap.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 30, 2018, 03:09:32 am
content: Quote from: tycz on October 30, 2018, 12:21:48 amAssuming it's hand assembled. And even so, if you're dealing with radial caps, I don't know how useful that would be. Given that you respect polarity, there's pretty much only one way to insert a radial, vertical cap, at least on the XY plane! Same for axial caps. Maybe the only case it could help is if you use radial caps, mount them horizontally and require a specific placement or pin length. I personally don't like mounting radial caps horizontally, but YMMV.And if you're repairing, you can just copy the original placement.A minimal indication like a simple circle or rectangle (depending on mounting orientation) helps locating the placement (without it it will take a little more time to spot it visually, I agree), but you don't need anything fancy and if your polarity mark is clear, no need for fancy shapes underside the cap imo. Factory workers usually use various automated or semi-automated tools to help place components and rely only marginally on silkscreen markings, unless maybe they work in a basement.

author: Deridex
author_rank: Regular Contributor
timestamp: November 02, 2018, 10:50:06 am
content: For THT-Caps i simply add a + near the positive pin.For the SMD ones i simplay paint the outline of the cap.So far i did not get any negative feedback about it. Neither from a supplier or from or own ppl that assmble it by hand.

author: nctnico
author_rank: Super Contributor
timestamp: November 03, 2018, 12:35:57 pm
content: Quote from: Deridex on November 02, 2018, 10:50:06 amA little bit off-topic: it is a good custom to place all polarised capacitors (electrolytic, tantalium, etc) and diodes in the same direction. This makes it very easy to spot assembly errors. Yes, even in the age of P&P these error do happen.