全铜通孔柔性LED封装热学性能仿真分析

柔性基板封装(COF)是一种新型LED封装形式。本研究在柔性基板中的高分子绝缘层(PI)中添加全铜通孔,通过有限元仿真分析全铜通孔对LED封装热学性能的影响。研究结果表明：在柔性LED封装中,PI层热阻最大,是导致芯片结温高的主要因素。PI层中全铜通孔的添加使PI层热阻大幅降低,显著提升LED封装的垂直散热能力。基于仿真计算结果,建立了PI层中添加全铜通孔数量与LED封装热阻间的对应关系。针对本研究中的封装结构,采用8*8 的全铜通孔阵列对LED封装的热学性能提升效果显著。     

Non-conductive film with Zn-nanoparticles (Zn-NCF) for 40 μm pitch Cu-pillar/Sn–Ag bump interconnection

Non-conductive film with Zn nano-particles (Zn-NCF) is an effective solution for fine-pitch Cu-pillar/Sn–Ag bump interconnection in terms of manufacturing process and interfacial reliability. In this study, NCFs with Zn nano-particles of different acidity, viscosity, and curing speed were formulated and diffused Zn contents in the Cu pillar/Sn–Ag bumps were measured after 3D TSV chip-stack bonding. Amount of Zn diffusion into the Cu pillar/Sn–Ag bumps increased as the acidity of resin increased, as the viscosity of resin decreased, as the curing speed of resin decreased, and as the bonding temperature increased. Diffusion of Zn nano-particles into the Cu pillar/Sn–Ag bumps are maximized when the resin viscosity became lowered and the solder oxide layer was removed. To analyze the effects of Zn-NCF on IMC reduction, IMC height depending on aging time was measured and corresponding activation energies for IMC growth were calculated. For the evaluation of joint reliabilities, test vehicles were bonded using NCFs with 0 wt%, 1 wt%, 5 wt%, and 10 wt% of Zn nano-particles and aged at 150 °C up to 500 h. NCF with 10 wt% Zn nano-particle showed remarkable suppression in Cu₆Sn₅ and (Cu,Ni)₆Sn₅ IMC compared to NCFs with 0 wt%, 1 wt%, and 5 wt% of Zn nano-particles. However, in terms of Cu₃Sn IMC suppression, which is the most critical goal of this experiment NCFs with 1 wt%, 5 wt%, and 10 wt% showed an equal amount of IMC suppression. As a result, it was successfully demonstrated that the suppression of Cu–Sn IMCs was achieved by the addition of Zn nano-particles in the NCFs resulting an enhanced reliability performance in the Cu/Sn–Ag bumps bonding in 3D TSV interconnection.