a number (N) of light-emitting units, each of said light-emitting units including a number (n) of light-emitting chips each having a first terminal and a second terminal that have opposite polarities, where N is an integer greater than one, and n is an integer greater than or equal to three;

a number (a) of first metal pads electrically connected to said first terminals of said light-emitting chips, where a is an integer equal to or greater than one; and

a number (b) of second metal pads electrically connected to said second terminals of said light-emitting chips, where b is an integer equal to or greater than one,

wherein each of said light-emitting chips is electrically connected to one of the number (a) of first metal pads and one of the number (b) of second metal pads, and

wherein the numbers (N), (n), (a) and (b) satisfy an equation of a*b=n*N;

wherein:

the number (a) is equal to one;

each of said light-emitting units includes a common node among said first terminals of said light-emitting chips, and said common node is electrically connected to said first metal pad; and

each light-emitting chip included in each of said light-emitting units is electrically connected to a respective one of the said second metal pads;

each of said light-emitting units includes a red light-emitting chip, a green light-emitting chip and a blue light-emitting chip that are configured to emit red light, green light and blue light, respectively; and

the equation is simplified into b=3*N.