-SNIP-
Following the interesting feedback from Nexus9090 regarding thermal management, I’ve been analyzing the Bitaxe setup through the lens of my professional background in QHSE (Quality, Health, Safety, and Environment).
While many focus solely on hashrate, we often overlook the Mean Time Between Failures (MTBF) of these small DIY boards. Here is a brief QHSE perspective on why the "Thermal Paste" upgrade is a safety and quality necessity, not just a performance tweak...
My recommendation for the community:
Always monitor your VRM temps alongside your ASIC. If you repaste, don't just chase the 11.25TH/s; use that thermal headroom to lower the overall stress on the board.
Just a little info.
Most semiconductors have a guaranteed working temperature of 125°C, but this is typically package and PCB layout dependent.
The VRM's that have sync FET switching on the NerdOAxe are rated to 125°C each guaranteed recommended max working temperature. If you're interested the datasheet for the sync rectifiers can be found here
https://www.ti.com/product/CSD95472Q5MCThe ASIC's (BM1370) on the other hand given the FR4 substrate packaging are more likely to have an upper limit of around 90°C, this is just because of the package and its poor thermal characteristics.
In my own tests with the (BM1397) ASIC a predecessor of the BM1370, I found that they became unreliable once you exceeded 70°C and very often would stop hashing all together beyond that temperature.
So for the most part, the VRM power stages definitely have plenty of headroom.
The ASIC on the other hand, less so.
The problem here is the packaging that BitMain chose to use for their ASICs, its cheap and prone to moisture ingress MSL3 would be my guess as to the package standard for moisture sensitivity. This is more of a problem at the assembly stage since moisture ingress can cause pop-corn or internal fractures that only become apparent after many thermal cycles. Given the build quality of these boards there's no guarantee that the material handling has been up to standard; I very much doubt the ASICs used are baked before assembly to drive out moisture so that'll have an impact on the devices life time.
In addition, the small exposed die area has limited thermal conductivity simply because of its size at 64mm.Sq. pushing 20Watts through that and dissipating it is hard work which is why good thermal paste is an absolute must for these devices.
In conclusion, Yes on the whole running the devices at a lower clock speed will prolong the lifetime of the devices, lower stresses throughout. But is it really that big a worry? probably not.
For me I'm not at all worried about pushing the board hard, that's what I bought it for. If it breaks I'll fix it, because I have the required skills in that department.
But for most people, keeping things steady at a lower speed is probably a safer bet.
