Solderless Flip Chip Using Polymer Flip Chip ProcessesA reliable and manufacturable flip chip infrastructure continues to develop worldwide.

A reliable and manufacturable flip chip infrastructure continues to develop worldwide. Significant advances in equipment, processes for flip chip interconnect, and long term reliability of the flip chip assemblies are causing a shift from chip and wire interconnect to non-packaged direct chip attach.
Miniaturized packages, higher density electronics and higher speed are the motivating forces for the true chip size, low inductance electrical interconnection that flip chip offers. As shown in Table 1, the ability to form a high input-output (I/O) packaging concept with low contact resistance, low capacitance, and low lead inductance will drive the microelectronics industry conversion from chip and wire to flip chip.
Flip chip interconnect technology will become the ultimate surface mount (SMT) technique in the 21st century, replacing BGA, μBGA, and CSP, which are best categorized as transition packages. All of these will use flip chip for electrically attaching the integrated circuit (IC) to the package substrate, until cost and space needs require eliminating the package altogether.

The three basic technologies underlying most of the hundreds of flip chip interconnect techniques are anisotropic materials, metallic bump technology, and isotropic conductive polymers. The process and reliability information which follows here focuses on the isotropic conductive polymer approach, or PFC® process. This process uses silver (Ag) filled thermoset and thermoplastic polymers, in combination with stencil printing processes, to form polymer bump interconnects for flip chip integrated circuit (IC) devices.
The following discussion of under-bump metallization (UBM) over aluminum, bump formation processes, and overall reliability of flip chip devices compares the relative performance of the thermoset and thermoplastic polymers which form the primary electrical interconnection.