Thermal Compression Bonding (TCB)
APS has developed and patented the Thermal Compression Bonding process with Low CTE No-flow underfill (TCB-NFU) and Pillar Bump. This technology is deemed an ideal solution for high pin count device in flip chip BGA package for graphic, routers, CPU and chipset applications. It has been successfully demonstrated on packages with die sizes up to 22mm x 22mm and >5000 I/Os with both Sn/Pb eutectic and lead-free bump metallurgies.

The TCB-NFU process is as follows:

1.	A low CTE (silica-filled) NFU is pre-dispensed onto the substrate.
2.	A pillar (with reflowable solder cap) bumped die is then picked and aligned to the substrate bond pads.
3.	Heat and mechanical force is applied to the die. During this process, heat is applied to melt the solder caps on the pillar bumps, mechanical force is applied to push the silica fillers away from the joint area and finally, the fluxing component in the NFU, removes the oxide from the solder and bond pad. In the event, solder joints are being formed. Typical process time required for joint formation is 5secs.
4.	The package is then sent for postcure to cure the NFU. Typical postcure time is about 60mins @ 150C.

The TCB-NFU process has these advantages:

1.	High and consistent interconnect yield is achieved via the combination of fluxing capability from NFU, mechanical force and temperature from the Flip Chip bonder.
2.	Gaseous by-products which cause voids are eliminated, since the NFU is not exposed to high temperatures during the TCB process.
3.	Utilizing TCB process, the NFU formulation window widens many-folds. Hence, there is no need to trade-off in physical and mechanical properties of the NFU, to meet yield and voiding requirements. The NFU used can be engineered to ensure maximum reliability & processability, and Silica fillers can be incorporated.
4.	TCB is low cost process as it removes need for several equipment such as Reflow and Deflux.

Additionally, APS has developed a proprietary NFU material (P-Bond LR-9000 series) specifically recommended for use with the TCB process. This material has unique properties, such as, excellent high temperature stability and exceptional fluxing strength. In addition, it is also engineered with superior mechanical properties to ensure good package reliability. This material is compatible with both Sn/Pb eutectic and lead-free bump metallurgies. Please refer to the Material – No Flow Underfill page for more details.

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