A system for effectively curing dry film ink throughout its thickness on circuit boards being made applies an exposure system, a circuit board, and a method for making the circuit board. The exposure system includes a plurality of mixed light sources with different wavelengths within a range of 365 nm to 440 nm, the mixed light sources can output at least three different wavelengths of light each of substantially a single wavelength and a fourth source of light able to output light of a spectrum of wavelengths, the ranges of light being between 365 nm and 440 nm.