NOVEL WAFER LEVEL PACKAGES USING ANISOTROPIC CONDUCTIVE ADHESIVES (ACPs) AND NCPs FOR FLIP-CHIP ASSEMBLY ON ORGANIC SUBSTRATESAuthors: Kyung-Wook Paik, Il Kim, Ho-Young Son, and Chang-Kyu Chung
Company: Korea Advanced Institute of Science and Technology
Date Published: 1/24/2008 Conference: Pan Pacific Symposium
In this study, wafer level flip chip packages using pre-applied ACAs (denoted as ACA-WLPs) including ACFs(films) and ACPs(pastes) were investigated. In case of ACF-WLPs, after ACF pre-lamination on an electroplated Au bumped wafer, and subsequent singulation, and singulated chips were flip-chip assembled on an organic substrate using a thermo-compression bonding method. In addition, in case of ACP-WLPs, ACPs were also directly coated on an entire wafer, and then dried as ACFs. After the ACFs coating on a Si wafer, subsequent dicing and assembly processes are the same as the ACF-WLPs case. For both ACF-WLPs and ACP-WLPs, Au plated bumps were well assembled on Ni/Au metal pads of organic substrates. The electrical, mechanical properties and the reliabilities of ACA-WLPs were evaluated and compared with conventional ACF flip chip assemblies using ACFs applied on a substrate followed by a flip chip assembly using a thermo-compression method. A single bump contact resistance measurement was performed after thermal cycling, high temperature/humidity, and pressure cooker test. ACA-WLPs showed stable contact resistance of 5mohm per a bump, strong bump adhesion, and similar reliability behaviors compared with conventional ACF flip chip joints using a thermo-compression bonding.
As a summary, new ACA-WLPs were successfully demonstrated for flip chip assembly, and ACA-WLPs can be widely used for many flip chip assembly applications such as COB (Chip-on-Board), COF (Chip-on-Flex), COG (Chip-on-Glass), embedded chips, and 3-D chip stacking.
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