Hi everyone, and thanks in advance for the help. I’m making my first footprint, which is for a .1uF cap as seen here: [https://katalog.we-online.de/pbs/datasheet/865230640001.pdf]
It appears the overall footprint is a 4.3mm X 4.3mm square. When looking at the diagram, there’s 1mm between pads, but the illustration shows this as almost half the length of the 4.3mm overall body. Is it normal for illustrations to be THAT off, or am I just missing something. Thanks!
I zoomed in on the datasheet, and used an old fashioned ruler to measure distances on my monitor.
I measuree 105mm for the square outline and 45mm for “P”.
4.3/105*45 = 1.8428571428571427
Which is weird in these days, because those drawing tend to be generated from CAD files.
The drawing also “looks about right”, while a specified number for “P” as 1mm seems very narrow. This is enough of a conflict to become suspicious. I could also not find measurements for the land pattern “fw”, “fl” “pl” in the datasheet.
Most of all, I find the maximum ripple current of 1mA very small.
Electrolytics are the single most unreliable components (except for connectors which got frequently abused maybe) and why use an electrolytic for a 100nF capacitor at all?
Have you compared this datasheet with a similar capacitor from another brand?
That’s easy to do. I also like to have the components on hand when I’m designing footprints for them, so I can measure stuff myself when there is any doubt.
once per series 
Then the only thing that is changed in the datasheet for a particular part is the table which is text only and therefore much easier to script/read from a datasheet.
I am however missing the table that holds the values for the land pattern (for the dimensions Pl, fl and fw)
Aahrg, It’s like those webshops where they sell 100 different products, and the pictures of all of them are the same. Few days ago at Digikey pictures of rolls of solder looked suspiciously similar. And while the text on some of the pictures clearly stated “500gram” according to Digikey hou only get 454 gram of solder. The rest evapored in the imperial conversion.
The important thing is, when you have conflicting data, go search for another source to verify.
Thanks guys. I’ll look for another one. It’s supposed to be used for a decoupling cap for a programable LED, but the manufacturer gives no more direction than just the capacity. Would a ceramic be better suited? Thanks again.
Yeah, 0.1 uF is a quite small value for an electrolytic capacitor - and the physical dimensions of this particular one seem huge for its electrical capacitance. I’d look for a different manufacturer, or at least a later version of the Data Sheet.
In general, ceramic capacitors are nearly always used for values up to about 1.0 uF - especially for power supply decoupling applications. A film-type capacitor in that value range may be used in circuit locations where tolerance, temperature stability, or waveform distortion are critical parameters. (And some audiophile guys have a fear of microphonic effects by ceramic capacitors.) Almost the only time an electrolytic would be used in this application is when the 'lytic’s higher ESR and ESL are being used to enhance circuit stability and suppress parasitic oscillation.
Dale
i have a contact with Wurth via work, I could ask him if this is right.
In general ceramic caps are kind of standard when it comes to decoupling caps. No need to ask wuerth about that. Any experienced electrical engineer can attest to that. (meaning ask experienced guys in your own company first)
Only if you have two differently sized caps in parallel to deal with different frequencies will you start to introduce a different type of capacitor. But in most such cases you will choose tantal caps for this as they also have a higher ESR compared to ceramic but are much smaller.
I meant I could ask him to look into this part. Clearly the pad dimensions are missing and as stated 0.1µF in this package is a bit strange. i avoid electrolytics were possible and will be putting as much ceramic as i can in with some electrolytic bulk.
I did use a Wurth electrolytic specifically in a recent design as it’s a polymer one and has lower ESR and their red expert is quite good as they give details on frequency response to their parts and i was working on an EMC filter with prior knowledge of the particular range of concern.
In an Ideal world you can just send Wurth an E-mail that their datasheet is incomplete / inconsistend and they say thank you and fix it.
When I had a subscribtion to Circuit Cellar I once downloaded a PDF with missing pages. Send them an E-mail, and they promply made a new version in which at least half of the missing pages were added back. I should have send them another mail…
Well it sounds like anyone contacting them might be able to get it sorted. They do keep saying that they are “more than you expect”. The people i have dealt with so far have been very good but that is through work and they are obviously keen to expand their customer base.
This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.