Circuit board structure and fabrication method of the same

A fabrication method of a circuit board structure, comprising the steps of:

• providing a carrier board with at least one surface formed with a circuit layer having a plurality of electrically connecting pads;
• forming a first solder mask on top of the carrier board and the circuit layer such that the first solder mask is higher than the top of the circuit layer, forming a plurality of first openings in the first solder mask by a patterning process to expose the electrically connecting pads;
• and
• forming a second solder mask on top of the first solder mask, forming a plurality of second openings in the second solder mask by a patterning process to correspondingly expose the electrically connecting pads beneath the first openings.

A fabrication method of a circuit board structure, comprising the steps of:

• providing a carrier board with at least one surface formed with a circuit layer having a plurality of electrically connecting pads;
• forming a first solder mask on top of the carrier board and the circuit layer;
• forming a second solder mask on top of the first solder mask;
• and
• forming, by a patterning process, a plurality of solder mask openings penetrating the second and the first solder masks to expose the electrically connecting pads.