Disclosed is a lighting device with flipped side-structure of LEDs, which allows emitted lights to travel in parallel with the mounting surface. Single or plural LED chips are mounted on a substrate with their side surfaces facing the substrate surface. The lighting device can be further combined with optical protrusions on the substrate to form a light module for reflecting and mixing lights emitted from the LED chips. It does not require a conventional wire bonding process. The packaging structure also resolves the heat dissipation problem of the LEDs. Electrostatic discharge protection circuits can be included in the light module if desired. The invention achieves good uniformity and high intensity of the combined lights with desired chromaticity.