Method for interconnecting a flip chip to a printed circuit substrate

A method for mechanically and electrically interconnecting a flip chip to a printed circuit substrate, the flip chip being of the type including a plurality of bonding pads defined on an active side thereof, at least a portion of the bonding pads having solder bumps formed thereon, the method comprising the steps of:

• (a) providing the printed circuit substrate as an adhesiveless metallized laminate having first and second circuit patterns defined on first and second sides of the adhesiveless metallized laminate, respectively, wherein the first side of the adhesiveless metallized laminate includes a plurality of active contact pads defined thereon in a footprint such that each active contact pad is arranged and configured to oppose a corresponding solder bump on the flip chip, and wherein at least one active contact pad includes an electrically conductive through hole for electrically interconnecting the first and second circuit patterns, and wherein the providing an adhesiveless metallized laminate step comprises the steps of:
• (1) providing a flexible polyimide dielectric film having a coefficient of thermal expansion substantially matched with that of copper;
• (2) forming through holes in the flexible polyimide dielectric film;
• (3) depositing copper on the flexible polyimide film to form first and second copper layers on opposing sides of the flexible polyimide dielectric film and to electrically interconnect the first and second copper layers by metallizing the through holes;
• and
• (4) etching the first and second copper layers on the flexible polyimide dielectric film to form the first and second circuit patterns;
• (b) providing solder paste on each active contact pad on the adhesiveless metallized laminate;
• (c) placing the flip chip on the adhesiveless metallized laminate such that the solder paste on each active contact pad is in registration with the corresponding solder bump on the flip chip to form an unsoldered chip-substrate assembly;
• and
• (d) heating the chip-substrate assembly such that the solder paste on each active contact pad reflows to form an electrical connection with the corresponding solder bump on the flip chip.

A method for mechanically and electrically interconnecting a flip chip to a printed circuit substrate, the flip chip being of the type including a plurality of bonding pads defined on an active side thereof, at least a portion of the bonding pads having solder bumps formed thereon, and the printed circuit substrate including an adhesiveless metallized laminate having first and second circuit patterns defined on first and second sides of the adhesiveless metallized laminate, respectively, wherein the first side of the adhesiveless metallized laminate includes a plurality of active contact pads defined thereon in a footprint such that each active contact pad is arranged and configured to oppose a corresponding solder bump on the flip chip, and wherein at least one active contact pad includes an electrically conductive through hole for electrically interconnecting the first and second circuit patterns, the method comprising the steps of:

• (a) providing solder paste on each active contact pad on the adhesiveless metallized laminate, including the step of controlling the volume of the solder paste such that the volume of solder paste located on each active contact pad is optimized as a function of the area of the active contact pad, the connected distance between the adhesiveless metallized laminate and the flip chip, and the volume of the corresponding solder bump;
• (b) placing the flip chip on the adhesiveless metallized laminate such that the solder paste on each active contact pad is in registration with the corresponding solder bump on the flip chip to form an unsoldered chip-substrate assembly;
• and
• (c) heating the chip-substrate assembly such that the solder paste on each active contact pad reflows to form an electrical connection with the corresponding solder bump on the flip chip.