Thanks for your time to reply me.
As I understand the right way is that the PCB have to heat in his overall area in order to avoid warping (like bimetallic strip). The boards that I would place would be:
24.5cm x 30.5cm (ATX Motherboard)
30.5cm x 30cm (E-ATX Motherboard)
28cm x 43cm (CNC Motherboard - 2 FPGA processor)
22cm x 9cm (Inverter PCB - 1 FPGA processor)
The only that I found and fits the "28cm x 43cm (CNC Motherboard - 2 FPGA processor)" is the JBC preheater "PHXLE-2KA" (Max PCB 51 x 61cm) where is quite expensive . Also, the next larger one where has an affordable price for me it the "Hakko FR872" but it has heating area 350x286mm. I would like to ask that if I buy the hako FR872 and a part of the PCB is out of the heating area will result to bend the PCB? I have seen a friend to do this method with the "Quick 854 infrared preheater" with the "22cm x 9cm (Inverter PCB - 1 small size FPGA processor - size 23x23mm) without bending (maybe by a chance not bending) but I would like your opinion. If anyone knows a large preheating plate please tell me.
PHXLE Preheater for PCBs up to 51 x 61 cm / 20 x 24"
https://www.jbctools.com/phxle-preheater-for-pcbs-up-to-51-x-61-cm-20-x-24-product-1835.htmlFR-872
https://www.hakko.com/english/products/hakko_fr872.htmlQuick 854ESD – PCB Preheater 600W 13x13cm
https://quick-global.eu/product/quick-854esd-pcb-preheater-600w-13x13cm/