Hey all, this is my first PCB and I'd really appreciate some experienced eyes on it. It takes 18V in, generates 5V and 3.3V rails, and drives 4 series LEDs at constant current with PWM dimming, all controlled over a CAN bus. It's a 4-layer board (Signal / GND / 3V3 / Signal) built around an STM32F103C8T6 18V goes into an LMR51420 buck for 5V, which feeds a KTD2505R constant-current boost LED driver running 4 LEDs at 333mA, and an LM1117 LDO derives 3.3V for the MCU and a TCAN334 CAN transceiver with SWD and UART headers for programming and debug (I also added a USB just in case). I would appreciate any feedbacks. what are the 100% must-fix changes you'd make and what are some improvements that aren't critical now but you think I should know for next designs?

Thanks

 

did you do rulle check? several places look way too close such as circled.
also why place mcu oscillator so close to buck converter?

 

Please take panic mode's advice into account. Look for DRC errors and correct if any. Here is a PCB Design Rule Check guide that you can follow. It covers all basic info about DRC and DFM.

 

Try to avoid right angle turns on traces, better beveled or curved.


Be careful with vias in the middle of a track, they can seriously affect the effective track width
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Don't connect decoupling or bulk storage caps with thin traces, try to keep all power traces the same dimensions and as direct/close as possible. Avoid vias in decoupling traces, esp to the HF filter capacitor, it adds an inductor where you don't want one. If you can't avoid it use 2 or 3 vias together. Here, link C7 directly to the tab of the VR, then drop the via directly off that for the 3.3v feed elsewhere. Put the touching but not 'in' the trace and link with a track the same size as the via. Do the same for ground vias, keep them close and don't use a thin track.
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