1. Originally, I asked for a list of your design specs in order of priority, but not getting very far.
These are useful to define and verify your design, so get. started.
2. I said hone your solder methods, you have gobs of cold solder joints. clean copper pads, tin the pads then tack on one end, solder finish the other after cold, the finish the tacked on joint. You are shorting out the top end layers out of 50-100 layers. That reduces C by poor solder temp control!!!
MTBF= ? @ xx 'C
V in min max
Efficiency
Load type, linear, reactive ? moving magnetic load, eg solenoid or motor
Vout I out peak
Step load, rise time
Voltage Tolerance
, ripple, Vpp
load regulatuon
input regulation
Power source impedance or what step load causes a 30% drop in input v.
max temp rise of hotspot? max ambient range?
Convection or conduction heat flow design? Rja=? worst case desired , consider 80'C max at max load and ambient
3. Next ESR and SRF analysis of every passive part from source thru convertor to load and calculation of zeros and poles (Laplacian not binary) thas Effective series Resistance and Series Resonant freqeuency for C and parallel self-resonant f, for L.
These MUST be much greater than switching freq, fSW
e.g. switching rate = fSW =340 kHz so SRF> 1.3MHz, this is negotiable to lower values if you use edge mount on PCB and/or use 50V caps
c3216x7r1e107k fs= below above fSW, no good,,also non-stock
50V better than 25V because any X7R MAY drop up to 90% C near rated voltage !!! such as 20V. So read da specs.
Factor C vs Vdc in derating, determine SRF and make it >2 fSW your switch rate higher the better
examine specs of ESR, SFR and $ for various 50V ceramic caps
https://product.tdk.com/info/en/documents/chara_sheet/C3216X5R1V226M160AC.pdf. READ and UNDERSTAND or ASK ok?
https://www.digikey.ca/product-detail/en/tdk-corporation/C3216X5R1V226M160AC/445-8045-1-ND/2792165
When I meant parallel caps, I was suggesting a low ESR plastic like 0.1uF with 10uF ceramic may work. but cost ESR and SRF with V & C value, size , temp, tolerance etc ALL affect cost