burnt capacitor on motherboard - Page 1
Forum section: electronics / repair

author: hakinen
author_rank: Newbie
timestamp: November 27, 2024, 11:37:43 am
content: Hi all,I got a supermicro motherboard (X10QBi) from ebay but during transportation 7 pcs(805) and 2pcs smaller caps ripped off from the backside of the board, i found 6 of the 805 size caps inside the box but rest was gone.i tried to repair the board by measuring the fallen caps with an LCR meter(4 of them was between 9-9.7uF, one of them was 16uF and the last one was 6.5uF), since most of them was around 10uF i ordered 10uF 16V 10% x5R 805 SMD caps and soldered them, could not solder or measure the smaller ones so i left them as it is.when i powered the board everything worked as it should be, entered the bios to check the components(nvmes, rams etc.) one at a time, after couple restarts one of the caps(C1437) near the cpu 4(at the front side) exploded during boot, i cleaned the cap and pads and power it on again to see what is working and what is not. MB powered on normally again, i checked all the pcies, cpus, rams, boards installed etc. everything was working fine.Today i wanted to try to install the OS(windows pro workstation), when i turn on the power, another cap(C1436) which is next to blown cap exploded but MB was still working full capacity and i was able to install the OS.Then i wondered if these one by one exploding caps are somehow related to the caps i soldered at the backside so with a multimeter i checked if they are connected as it seems they are connected to two caps at the back which i soldered(C1234 and C1235). I am a newbie in electronics so i wonder if some of you guys can help me find out what is wrong and how to fix it.I already contacted with supermicro support and they are not willing to help.the interesting thing is, the caps i soldered are not burning but some other caps are burning one by one. I stoped powering on the MB not to burn more caps or damage the hardware.Thanks in advance for your help.

author: CaptDon
author_rank: Super Contributor
timestamp: November 27, 2024, 01:51:54 pm
content: I can almost assure you when you soldered the new caps you thermally stressed them causing cracks across the multi-layers (MLCC) and they finally dead shorted and blew up. This is par for the course when MLCC caps get reworked or reflowed. Hand soldering MLCC caps needs a very skilled careful hand and lots of prior experience and knowing what is and isn't acceptable stress levels. I've seen hundreds of failures exactly like yours. You can create both infant mortality failures and long term unreliability when you hand rework MLCC caps. Perhaps you should have filed a damaged in transit claim? How do you knock SMD devices off a board if packaged correctly? Sounds like a start to finish FAIL.

author: hakinen
author_rank: Newbie
timestamp: November 27, 2024, 02:35:38 pm
content: Thank u for your reply CaptDon,Well ebay seller did his part ok i guess, there was a forwarder company involved for the shipping, i think they repack the board for some reason and it was not wrapped in a bubble etc. just tossed in a box with some small foams so it was moving in the package freely and i think thats some sort of intentional thing..anyhow i think u are right about what is happening, i checked the burnt caps(at the front) and the ones i soldered at the back closely today which u can see in the attached images, explosions(most probably because of the shorts of 2 or more caps i soldered at the back) burnt the protective layer under the first copper layer and the one below it is visible, i am checking for the shorts and will remove the 2 caps(i soldered back) or all, which are related with this set of caps and try to resolder new ones back more carefully. By the way in close up images from the sides they all look to me as shorted by means of solder, they all look ok from top but from side the view is frightening if i am seeing correctlyfor the burnt ones, there is an identical set of components at the left side of the board, i can desolder one of the caps check its value and order new ones similar to that and solder back, also i will try to put a protective layer of epoxy or polyurethane between the layers to isolate them.i have regular ersa soldering station and also a heater with a solder paste, i didnt use the heater cause i thought it would melt the other component's solders too if i apply it more than enough or harm the pcb but the situation is worse now.. so which way do u advice me to go or do u have any tips for not to harm the mlcc caps during soldering? or make a proper soldering?by the way do u think the values of the caps i put at the back may harm the board? i mean am i right to choose 10uF 16v ones? because there is 10v,20v,50v ones too i just choose the middle for the voltage value.Thanks again,Hakan

author: coromonadalix
author_rank: Super Contributor
timestamp: November 27, 2024, 03:39:01 pm
content: ugliest soldering i've seen?

author: CaptDon
author_rank: Super Contributor
timestamp: November 27, 2024, 04:02:09 pm
content: I concur!! That much solder dragging that much heat along was an immediate death sentence to those caps!!

author: hakinen
author_rank: Newbie
timestamp: November 27, 2024, 08:17:35 pm
content: it was not for a beauty contest coromonadalix but thanks for the input

author: tooki
author_rank: Super Contributor
timestamp: November 27, 2024, 09:04:52 pm
content: The problem is that motherboards are boards with lots of layers, and all that copper sucks away heat. So you need a powerful iron, but above all, you need to use supplemental board heating.

author: wraper
author_rank: Unknown
timestamp: November 27, 2024, 09:21:27 pm
content: Quote from: CaptDon on November 27, 2024, 01:51:54 pmYes, because of that it's much safer to solder them with hot air rather than with soldering iron.

author: hakinen
author_rank: Newbie
timestamp: November 27, 2024, 09:29:26 pm
content: Hi tooki,thanks for your reply,well i removed some caps i soldered and measured them with lcr meter and found out that none of them was harmed, they are all intact and i can read their capacitance with the meter. so it means i didnt apply much heat because i was quick while soldering thats why the solders are weird. I didnt crack or harm them with heat but i may done bad soldering which can cause short. Its just that after soldering i checked the pads and caps for short circuit with multimeter(continuity function) and there were no shorts and i trusted it.i will make the solders with liquid solder(solder paste) this time, one drop on the pads and will put the cap in place then will heat it with a small heat gun, i hope i will get better/clean results.Any of u guys know about mlcc cap. values? is my choice 10uF 16v is good as replacement caps for the ones at the back?

author: DimitriP
author_rank: Super Contributor
timestamp: November 27, 2024, 10:38:10 pm
content: The motherboards' CPU compatibility leaves me very unexcited:

author: hakinen
author_rank: Newbie
timestamp: November 27, 2024, 11:30:31 pm
content: Quote from: DimitriP on November 27, 2024, 10:38:10 pmthis MB accepts 4pcs 8890 V4 which are multiprocessing units; 24 cores runs at 2.2ghz, 4x24 u have 96 cores. mb accepts 12TB DDR4 ECC ram these are server grade products not newest tech but more than enough price-performance tech for a workstation especially if u are going to run some simulations, it has pcie 3.0 slots for anykind of upgrade, with nvme raid0 pcie cards it will outperform many newest single processor(not multi processing) mbs. also with aom-sxmv board which accepts 4pcs V100 gpu(also good in simulation running) and it can be connected to this mb with 2 pcie x16 slots and rtx a4000 will run the 3pcs 32" 4k displays.So, its a pretty good desktop workstation i think

author: DimitriP
author_rank: Super Contributor
timestamp: November 28, 2024, 12:54:51 am
content: Can't argue with 12 TB RAM if it's gonna be used for something other than "bragging rights".As for price/performance, without knowing price of the "whole thing" and the performance goal, there are too many (both) variables missing.If nothing else it will keep the room warm

author: hakinen
author_rank: Newbie
timestamp: November 28, 2024, 01:16:24 pm
content: Quote from: DimitriP on November 28, 2024, 12:54:51 amwell together with 4pcs v100 it will definitely keep the room warm in full load(simulation), but during regular use(3d modelling-designing etc.) it will act cool like Clint Eastwoodif and only if i make it work steadyanyway i already find a replacement from China for 1500CNY, if i can not make it work steady than i will get another one from there.