I am not an engineer but that board design looks crazy to me. Why on earth would there be 26 chips on 1 side of the PCB and 3 on the other side.
That looks like it would be a disaster to cool and the traces look whacky with the square layout of the chips on the side with 26.
Who told you that these three chips require cooling ?
26 chips go with thermal paste to heatsink , such as Antminer S5.
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Have you question, I will try to answer
But where to take the S3 owners screws and springs for it ?
I see that it is only suitable for Antminer S5 upgrade, not for S1, S3 or C1, where the blades are the other way around.