Very long wave 640×512 FPAs with 25 μm pixel pitch and cutoff wavelength of 13.23 μm， 14.79 μm respectively at 77 K were prepared by the arsenic ion implanted p-on-n planar junction technology. The basic performance and dark current of the FPAs are characterized and analyzed. The results show that the quantum efficiency of the VLWIR 640×512 FPAs with λ_c （77 K） =13.23 μm is 55%， the average NETD is 21.5 mk， with an operability of 99.81%； The quantum efficiency of the VLWIR 640×512 FPAs with λ_c （77 K） =14.79 μm is 45%， the average NETD is 34.6 mK， with an operability of 99.28%. The R₀A figures of merit at liquid nitrogen temperature are 19.8 Ω·cm² and 1.56 Ω·cm² respectively， which reaches the predicted value of the "rule07" heuristic law， and the device noise is mainly limited by current shot noise. The results show that the performances of FPAs are at the state of the art.