A semiconductor device has a semiconductor die having a plurality of die bump pad and substrate having a plurality of conductive trace with an interconnect site. A solder mask patch is formed interstitially between the die bump pads or interconnect sites. A conductive bump material is deposited on the interconnect sites or die bump pads. The semiconductor die is mounted to the substrate so that the conductive bump material is disposed between the die bump pads and interconnect sites. The conductive bump material is reflowed without a solder mask around the die bump pad or interconnect site to form an interconnect structure between the semiconductor die and substrate. The solder mask patch confines the conductive bump material within the die bump pad or interconnect site. The interconnect structure can include a fusible portion and non-fusible portion. An encapsulant is deposited between the semiconductor die and substrate.