A method for forming a printed circuit board includes providing a substrate including a first device region, a second device region and a dicing channel region between the first device region and the second device region. A first circuit is formed on the substrate. An insulating layer is formed on the first circuit and the substrate. At least one build-up circuit is formed on the insulating layer. A photoresist layer is formed on the at least one build-up circuit. An image transferring process is performed to pattern the photoresist layer to form a dam structure in the dicing channel region. A solder mask layer is formed on the at least one build-up circuit. The dam structure is removed to form a trench in the solder mask layer.