Hello SHADOWua
Both LPC11U14FBD48 and LPC11U35FBD4 belong to NXP's LPC11U series, use ARM Cortex-M0 cores, and share the same 48-LQFP package and pin-to-pin compatiable. This means, from hardware aspect, you don't need to change PCB if replace LPC11U14FBD48 with LPC11U35FBD4.
LPC11U35 has 64KB Flash and 10KB RAM, while LPC11U14 has 32KB Flash and 6KB RAM. LPC11U14 memory and resource addresses are all defined in LPC11U35. So theorilly, LPC11U14FBD48 firmware can work on LPC11U35FBD4.
Hope this helps,
Jun Zhang