Effect of flip chip bonding parameters on microstructure at the interconnect interface and shear properties of 64.8Sn35.2Pb microbumps were investigated in this work.Results show that the main intermetallic compound(I...Effect of flip chip bonding parameters on microstructure at the interconnect interface and shear properties of 64.8Sn35.2Pb microbumps were investigated in this work.Results show that the main intermetallic compound(IMC)at the interconnect interface is(Ni,Cu)_(3)Sn_(4)phase,and meanwhile a small amount of(Cu,Ni)_(6)Sn_(5)phase with a size of 50−100 nm is formed around(Ni,Cu)_(3)Sn_(4)phase.The orientation relationship of[-1-56](Ni,Cu)_(3)Sn_(4)//[152](Cu,Ni)_(6)Sn_(5)and(601)(Ni,Cu)_(3)Sn_(4)//(-201)(Cu,Ni)_(6)Sn_(5)is found between these two phases,and the atomic matching at the interface of the two phases is low.The highest shear force of 77.3 gf is achieved in the 64.8Sn35.2Pb microbump at the peak temperature of 250℃and parameter V1 because dense IMCs and no cracks form at the interconnect interface.Two typical fracture modes of microbumps are determined as solder fracture and mixed fracture.The high thermal stress presenting in the thick IMCs layer induces crack initiation,and cracks propagate along theα/βphase boundaries in the Sn-Pb solder under shear force,leading to a mixed fracture mode in the microbumps.展开更多
Flexible implantable electrodes provide unprecedented opportunities for gentle mechanical interaction with soft neural tissues to acquire stable electrophysiological signals and reduce risk of tissue inflammatory resp...Flexible implantable electrodes provide unprecedented opportunities for gentle mechanical interaction with soft neural tissues to acquire stable electrophysiological signals and reduce risk of tissue inflammatory response.Most electrocorticography(ECoG)electrodes adopt polymer film or silicone as substrate,with thickness sacrifice or poor micromachining precision,respectively.Besides,the distance of recessed electrode site to cortical surface leads to signal degradation.Here,we report a 3D polyimide-based electrode array on soft microbumps(height,327µm),with buffering contact capability and reliable mechanical strength that alleviates the mismatch from dental cement or cranial window.We demonstrate the reshaping processes of conventional 2D sites(diameter,200µm)into 3D protruding structure by stress-free preforming and silicone casting.The 3D soft microbump electrodes(SMBE)remain well undergoing whether cyclic voltammetry scanning or cyclic compression.The acute implanted SMBE array has shown sensitive response to whisker pulling and insusceptible stability by external force of anesthetic rats.展开更多
Metallurgical challenges in controlling the microstructural stability of Cu and solder microbumps in 3D IC packaging technol-ogy are discussed. Using uni-directional 【111】 oriented nanotwinned Cu, the controlled gro...Metallurgical challenges in controlling the microstructural stability of Cu and solder microbumps in 3D IC packaging technol-ogy are discussed. Using uni-directional 【111】 oriented nanotwinned Cu, the controlled growth of oriented Cu6Sn5 on the nanotwinned Cu and its transformation to Cu3Sn without Kirkendall voids have been achieved. In order to join a stack of Si chips into a 3D device, multiple reflows of solder microbumps may be required; we consider localized heating to do so by the use of self-sustained explosive reaction in multi-layered Al/Ni thin films of nano thickness. It avoids re-melting of those solder joints which have been formed already in the 3D stacking structure.展开更多
基金Project(U2341254)supported by Ye Qisun Science Foundation of National Natural Science Foundation of ChinaProject(52475406)supported by the National Nature Science Foundation of ChinaProject(2024CY2-GJHX-32)supported by the Key R&D Program of Shaanxi Province,China。
文摘Effect of flip chip bonding parameters on microstructure at the interconnect interface and shear properties of 64.8Sn35.2Pb microbumps were investigated in this work.Results show that the main intermetallic compound(IMC)at the interconnect interface is(Ni,Cu)_(3)Sn_(4)phase,and meanwhile a small amount of(Cu,Ni)_(6)Sn_(5)phase with a size of 50−100 nm is formed around(Ni,Cu)_(3)Sn_(4)phase.The orientation relationship of[-1-56](Ni,Cu)_(3)Sn_(4)//[152](Cu,Ni)_(6)Sn_(5)and(601)(Ni,Cu)_(3)Sn_(4)//(-201)(Cu,Ni)_(6)Sn_(5)is found between these two phases,and the atomic matching at the interface of the two phases is low.The highest shear force of 77.3 gf is achieved in the 64.8Sn35.2Pb microbump at the peak temperature of 250℃and parameter V1 because dense IMCs and no cracks form at the interconnect interface.Two typical fracture modes of microbumps are determined as solder fracture and mixed fracture.The high thermal stress presenting in the thick IMCs layer induces crack initiation,and cracks propagate along theα/βphase boundaries in the Sn-Pb solder under shear force,leading to a mixed fracture mode in the microbumps.
基金support received from the Science and Technology Innovation 2030-Major Project(2022ZD0208601,2022ZD0208600)National Natural Science Foundation of China(62204204,62104056)+2 种基金Innovation Capability Support Program of Shaanxi(2024RSCXTD-7)NaturalScience Basic Research Plan in Shaanxi Province of China(2023JC-XJ-07)support from Dr.Honglai Xu,Mr.Yuxiang Hong from Neuracle Medical Technology(Shanghai)Co.,Ltd.,Mr.Xiaowang Zhao from LPKF Shanghai Co.,Ltd.,staffs from Wenzhou Institute of Hangzhou Dianzi University and Xi'an LEADMEMS SCI&-TECH Co.,Ltd。
文摘Flexible implantable electrodes provide unprecedented opportunities for gentle mechanical interaction with soft neural tissues to acquire stable electrophysiological signals and reduce risk of tissue inflammatory response.Most electrocorticography(ECoG)electrodes adopt polymer film or silicone as substrate,with thickness sacrifice or poor micromachining precision,respectively.Besides,the distance of recessed electrode site to cortical surface leads to signal degradation.Here,we report a 3D polyimide-based electrode array on soft microbumps(height,327µm),with buffering contact capability and reliable mechanical strength that alleviates the mismatch from dental cement or cranial window.We demonstrate the reshaping processes of conventional 2D sites(diameter,200µm)into 3D protruding structure by stress-free preforming and silicone casting.The 3D soft microbump electrodes(SMBE)remain well undergoing whether cyclic voltammetry scanning or cyclic compression.The acute implanted SMBE array has shown sensitive response to whisker pulling and insusceptible stability by external force of anesthetic rats.
文摘Metallurgical challenges in controlling the microstructural stability of Cu and solder microbumps in 3D IC packaging technol-ogy are discussed. Using uni-directional 【111】 oriented nanotwinned Cu, the controlled growth of oriented Cu6Sn5 on the nanotwinned Cu and its transformation to Cu3Sn without Kirkendall voids have been achieved. In order to join a stack of Si chips into a 3D device, multiple reflows of solder microbumps may be required; we consider localized heating to do so by the use of self-sustained explosive reaction in multi-layered Al/Ni thin films of nano thickness. It avoids re-melting of those solder joints which have been formed already in the 3D stacking structure.
