Light emitting diode chip scale packaging structure and direct type backlight module

A light emitting diode chip scale packaging structure, comprising:

• a light emitting diode chip;
• a wavelength converting layer disposed on the light emitting diode chip and directly contacting the light emitting diode chip, wherein the wavelength converting layer comprises phosphor powders;
• a diffusion structure covering the light emitting diode chip and the wavelength converting layer, wherein a ratio of a height of the diffusion structure to a width of the diffusion structure is 1:2 to 5:4;
• and
• a lens covering the diffusion structure, wherein an outer surface of the lens is a free-form surface, a material of the lens is different from a material of the diffusion structure:
• wherein a curve of the outer surface of the lens in a cross-sectional view substantially complies with a polynomial of:
• Z=Σi=0nαi*yi
• a center point of the curve corresponding to the light emitting diode chip is a zero point of y-z coordinate axes, z is a variable of a vertical axis of the curve, y is a variable of a horizontal axis of the curve, ai is a constant coefficient in a term of ith degree, and 3<n≤6, wherein the diffusion structure comprises an encapsulant and a plurality of first diffusion particles doped in the encapsulant, the first diffusion particles comprise polystyrene (PS), poly-methyl methacrylate (PMMA), polycarbonate (PC), titanium oxide, silicon oxide, aluminum oxide, zirconium oxide, or combinations thereof, a particle size of the first diffusion particles is equal to or less than 50 nm, the lens has a first refractive index, the diffusion structure has a second refractive index, and the second refractive index is larger than the first refractive index by at least 0.2.