MOSFETs commonly found in GPUs?

[andrejr]

Do you have any suggestions on which MOSFETs to stock (from China, presumably, though Mouser/Digikey/Arrow are also OK) for repairing GPUs? Different varieties that occur on Geforce RTX 1060 and newer and Radeon RX470 and newer, I wouldn't want to repair older cards. So far, I guess that it'd make sense to get some single N/P MOSFETS in WDFN8, as well as pairs in the same package. I'm guessing that putting higher current, lower Rds MOSFETs instead of worse ones probably won't cause issues, as long as the pinout matches. In that light, what do you suggest I get to have on hand for quick fixes?

Recently a friend gave me a GPU to repair (an RTX2070), which was pretty easy to fix (2 blown MOSFETs). I realized there's nothing to it: just a bunch of buck converters and rail switches with MOSFETS, RAM and the processor chip itself (OK, yeah, flash for the bios, PCIE stuff too, but that stuff is unlikely to fail). This got me thinking I could do this as a side gig, I just need some parts in stock because both time and shipping costs for getting like 2 MOSFETs really sucks.

[thm_w]

You can search for card reviews and they will provide you with high res photos, eg 2060: https://www.techpowerup.com/review/evga-geforce-rtx-2060-ko/3.html
https://www.onsemi.com/pdf/datasheet/ncp302155-d.pdf

https://www.techpowerup.com/review/galax-geforce-rtx-2060-super-ex/4.html
https://datasheet.octopart.com/NTLTS3107PR2G-ON-Semiconductor-datasheet-162333.pdf ?

[RoGeorge]

It depends of the GPU model.
Buy only what you need, and when you need.

Right now it's not a good moment to stock on electronic parts, anyway.  Prices are already much higher than normal, so in the long term components will devalue, unless you plan to do short term price speculations, of course.

[AndyC_772]

I'm guessing that putting higher current, lower Rds MOSFETs instead of worse ones probably won't cause issues, as long as the pinout matches.

No, this isn't true. Lower Rds is, all other things being equal, achieved by making the channel wider, and that means higher gate capacitance. This in turn means that, in a switching circuit, the MOSFET spends more time in the transition region between fully off and fully on, which is where it dissipates the most power.

In any circuit there is a trade-off between switching losses, which depend on the gate driver strength and switching frequency, and the static conduction losses which depend on Rds(on). The best transistor for any given circuit is one that's the right size, not necessarily the biggest.

My advice? Buy the correct parts for each job as and when the job comes in. Buy a few spares whenever you order, and over time, you'll build up a small stock of the parts you actually needed. You'll also have spares on hand to replace any MOSFETS that fail again because there's a fault elsewhere - remember, components that are being used within their specifications rarely fail for no reason.

[rob77]

first of all i would not suggest to stock any mosfets or chips from china unless it's the only option. in most cases you'll get fake (cheap crappy mosfets marked as expensive ones)  or used parts (some of them survived the "bonfire" desoldering process, some not).

order from reputable distributors... availability is crap but you can still find suitable mosfets. as long as Ids, Vds, Rdson are same or better and gate capacitance are similar enough (roughly in the same ballpark) it will work.

i do repair laptop MBs for fun, and i just stock whatever fit's the bill and has the footprint for example.. dfn3x3 mosfets are on the scarce side nowadays (TME has 7 dfn3x3 models in stock out of ~ 50 listed) .. but i'm still able to find the "closest match".

[wraper]

first of all i would not suggest to stock any mosfets or chips from china unless it's the only option. in most cases you'll get fake (cheap crappy mosfets marked as expensive ones)  or used parts (some of them survived the "bonfire" desoldering process, some not).

Yeah, a while ago bought on aliexpress some on semi mosfets to repair a GPU. They were obviously sanded and relabeled, bottom pads looked suspicious too. Right away tested them and turned out half of them were already shorted and the rest which worked had about 2x higher RDS(on).

[andrejr]

Is it really that bad? I actually ordered some SMD JFETS, NOS discontinued 12mm Alpha pots, H1F3 opto-fets, hard to find jacks, all from China (either Ali or Ebay) in the last year, and almost everything worked fine. The only thing I had issues with are breadboards (poor quality, not matching pics). Am I just lucky? None of these even looked salvaged or relabeled, all came on tape. These components probably weren't in demand, though. Obviously, I buy from sellers that have good feedback and many sales, though I bet good reviews can be bought.

Sure, I can always order through regular suppliers, but the shipping is downright silly for some (Mouser, Digikey). I can also add cheap components to company orders, but my company orders maybe once or twice a month...

[rob77]

Is it really that bad?

it depends.. jelly bean stuff will be ok , but power mosfets will be most likely fake (cheaper ones relabeled as more expensive ones)... i have a bunch of fake IRF44 mosfets from china, they were dirt cheap , they work , but definitely fake.

obscure and hard to find chips will be fake or salvaged parts.. tape means nothing... i bough 5pcs of RT8243A (psu controller commonly used in HP laptops with 4/5th gen intel cpus) - they came in a cut tape, but each chip had different datecode, had some scratches and only 2 of them worked correctly

[nctnico]

Is it really that bad? I actually ordered some SMD JFETS, NOS discontinued 12mm Alpha pots, H1F3 opto-fets, hard to find jacks, all from China (either Ali or Ebay) in the last year, and almost everything worked fine. The only thing I had issues with are breadboards (poor quality, not matching pics). Am I just lucky? None of these even looked salvaged or relabeled, all came on tape. These components probably weren't in demand, though. Obviously, I buy from sellers that have good feedback and many sales, though I bet good reviews can be bought.

In addition to the very good advice AndyC_772 already has given: buy components from reputable sources if you respect your customers. In the end you are not doing them a favour by using wrong / fake parts. Likely you can upsell your services a bit by letting customers know that you are using genuine parts.

Last year I also received parts packed in tape which where obviously desoldered from boards. There just isn't a way for me to make a reliable product I can vouch for with such parts.

[jonsig]

Only parts i have stocked are FDMF3035 smartfets and 4C08/4C05 mosfets, they are common in the pascal architecture. Radeon cards use totally different random mosfets and i do not stock GDDR5x because you have multiple types flying around when dealing with older cards. It´s probably idea if you are dealing with high end ampere card , think GDDR6x is micron only, though im not sure.

I usually scrap mosfets and Vram from donor boards with 100% dead GPU. But have often sourced Ram/mosfets from ali- express, and have not seen failures yet after using them multiple times. But suspect inferior quality of the Vram. Because i had minor problems við Vram clock on "OC" gpu editions like GameRock