Replace Multilayer Ceramic Capacitor on Asrock Z97E-ITX/ac

[MrCommunistGen]

I initially posted this as a thread on Linus Tech Tips. I got some feedback, but not really to a level that gives me confidence in my next steps. Then I remembered about this forum that I'd used as a great reference for recapping an amp so I figured I'd reach out here. My question below is a combination of my original question as well as all of my findings in the other forum:


I just received a used Asrock Z97E-ITX/ac board that I purchased on eBay. According to the seller the board works. During unboxing I noticed that one of the Multilayer Ceramic Capacitors (I think it is an MLCC but someone also suggested it might be a fuse) on the back of the board behind the VRM is missing. I checked and it wasn't bouncing around inside the package -- that would be too easy.

(see attached board picture)

I've done a bit of board recapping - but only for electrolytic capacitors where reading the values off of the label is really easy. I have 0 experience with MLCCs.

I put a sacrificial CPU into the board (an i3-4150T FWIW) and the board seems to work. I was able to successfully install a clean copy of Windows and do some cursory stability testing.

Even though the board works, I'd still like to replace the cap, but I don't know the voltage, capacitance, ESR, etc of the existing caps that are there. Is my best bet to just pull one of the remaining caps off and check it? I have a multimeter that has a capacitance mode, but this is only going to get me one of the measurements I need.

Also, whether it is a cap or a fuse, its absence would seem to indicate that one of the voltage planes of the board has been decoupled from the CPU socket... or at the very least isn't being filtered properly(?).


My google-foo isn't good enough to find a board circuit diagram for this motherboard, though someone was able to find a repository of many OTHER boards here: Link. Honestly, if I just knew what kind of MLCC to buy I could easily get this done... If any of you are familiar with the YouTube creator "buildzoid" this seems like something he would know offhand.

I apologize if my explanations are lacking. Electronics are not my forte, but I'm eager to expand my knowledge. If you have a question or suggestion, I'm happy to try to help you help me!! I have an inexpensive but moderately capable multimeter and am happy to take some readings and report back if it will help.

Thanks!

Edit:
It is my plan to try to go through the diagrams of the other boards that are provided at the link to try to see if the specified cap is listed and if they all seem to use one of a similar rating. If so I might be able to infer what cap I should be using despite none of the Z97 boards seeming to use exactly the same VRM layout.

[R_J]

Re: Replace Multilayer Ceramic Capacitor on Asrock Z97E-ITX/ac

I would expect the cap. to be the same µf as the two to the left (all 6 are likely the same value) so you could remove one and check its value. I would suspect the voltage to quite low, check the voltage across the cap, it's likely under a few volts

[MrCommunistGen]

Re: Replace Multilayer Ceramic Capacitor on Asrock Z97E-ITX/ac

I would expect the cap. to be the same µf as the two to the left (all 6 are likely the same value) so you could remove one and check its value. I would suspect the voltage to quite low, check the voltage across the cap, it's likely under a few volts

With the board powered up, I'm reading 12.2V across one of the still connected caps by poking each side of it with my multimeter. It would appear that these are probably for input side filtering. The 12.2V reading is due to the pretty low end PSU I'm using on my test bench. Since the ATX spec allows for up to 12.6V, I imagine I'd want to get at least a 12V +/- 10% cap or one for 13V+ to avoid sending too high of a voltage through it.

As oriented in the attached picture, the left-hand pad for each of the capacitors reads 0 ohms to ground. The right hand side reads as a pretty big number that doesn't stay fixed at a single value. I haven't desoldered one of the caps yet, but that's planned for this evening after it cools down a bit. Even without pulling one of the caps off of the board, if I use the capacitance setting I get a reading of ~90μF +/- 1μF on each of the populated components. This leads me to believe that they are in fact capacitors (it has been suggested the might be fuses). I'll see about getting a true reading after desoldering one of them. And of course the holy grail would be to find some markings on the underside of the cap.

The nearest rating I can find on Mouser is for a 16V 100μF capacitor... and at least for low quantities they're NOT cheap for such a small part. It looks like getting that combination of voltage and relatively high capacitance is costly. Dropping the voltage down a notch to 10V or dropping capacitance down to 47μF each cut the cost roughly in half.

I'll report back after I know more.

[Per Hansson]

Re: Replace Multilayer Ceramic Capacitor on Asrock Z97E-ITX/ac

From your multimeter readings you can be sure it is not a fuse:
Just imagine what would happen if you put a fuse across something that has 12v potential to ground? That is a short, fuse go bye bye
This is probably a 10uF or thereabout MLCC.

[MrCommunistGen]

Re: Replace Multilayer Ceramic Capacitor on Asrock Z97E-ITX/ac

This is probably a 10uF or thereabout MLCC.

Right on the money!!

Short version:
Pulled off a cap and it measured right at ~10uF (10.2-10.3uF measured).

Long version:
I desoldered one of the caps, and then while trying to get the leads of my multimeter onto it with enough pressure to make good contact... it shot off onto the floor and disappeared forever. Since I'd probably killed the board anyway by removing a 2nd cap, I went for broke and pulled another one off and by being more careful was able to get a measurement on it that lined up with your 10uF estimate.

So... now I need at least 2 replacements. Any suggestions or guidance would be appreciated. For starters since at this point 2 capacitors are missing and I've desoldered a 3rd. Would it make sense to just replace all 6 so that they match?

Shopping at either Mouser or Digikey, it looks like I'd need to source a 16V 10uF MLCC -- of which there are MANY. There's tons of resources available for electrolytic capacitors, but I've been having trouble finding info on MLCCs.
These are some of the properties I'm hoping to get some advice on:

1. Are there any particular brands I should consider or avoid? Right now the brands I'm considering are TDK, Samsung, Taiyo Yuden, and Kemet.
   
2. I'm currently considering X5R and X7R rated caps . I'm leaning towards X7R just to make sure what I'm getting is good enough. This is just a guess and not based on any sort of experience.
   
3. I'm looking at +/-10% tolerance parts. +/-5% are pretty expensive and I feel like that level of tolerance is overkill... but again, I'm not an expert.
   
4. I think that these are 1206 (in inches) capacitors, but I'm going to get some digital calipers to measure for sure. I seem to only have really crappy rulers that aren't anywhere near precise enough to be.

Thanks for the assistance so far!

[R_J]

Re: Replace Multilayer Ceramic Capacitor on Asrock Z97E-ITX/ac

Any of those brands should be ok, as long as the cap fits the pads. They are not that critical.

[MrCommunistGen]

Re: Replace Multilayer Ceramic Capacitor on Asrock Z97E-ITX/ac

Back when I was initially thinking that the require capacitance was more like 100uF, it seemed obvious that I'd need a Class 2 MLCC because Class 1 MLCCs wouldn't have that high of capacitance at the required voltage and dimensions... but now that I'm only looking at 10uF so both Classes are available.

According to the wikipedia article:
Class 1 ceramic capacitors offer high stability and low losses for resonant circuit applications.
Class 2 ceramic capacitors offer high volumetric efficiency for buffer, by-pass, and coupling applications.

Based on my pretty limited knowledge of electronics and motherboard VRM design I think what I'm looking for is a Class 2... but I really don't know.

I would greatly appreciate any input or advice.