Underfilling efficiency by modifying the substrate design of flip chips

A method for underfilling a chip;

• providing a substrate;
• forming a solder mask over the substrate;
• forming a metal trace structure within the solder mask;
• the metal trace structure including a channel therein for the receipt of underfill;
• the metal trace structure further including a central portion with arms radiating outwardly therefrom, dividing the solder mask into separate areas;
• the substrate, solder mask and metal trace structure comprising a substrate structure;
• providing a chip having a series of solder bumps formed on the underside of the chip;
• the solder bumps being arranged in a pattern including openings;
• placing the underside of the chip onto the substrate structure wherein the openings in the solder bump design overlie the substrate structure's metal trace structure;
• and
• introducing underfill into the metal trace structure so that the underfill flows from the metal trace structure between the solder bumps in the solder bump design to underfill the chip.