Browsing by Author "Pan, Hung-Chun"

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An Investigation of Diffusion Barrier Characteristics of an Electroless Co(W, P) Layer to Lead-Free SnBi Solder
(2011-03-01)
Pan, Hung-Chun
;
Hsieh, Tsung-Eong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Diffusion barrier characteristics for eutectic SnBi solder/electroless Co(W,P) couples were investigated via liquid-state aging at 250 degrees C and solid-state aging at 120 degrees C. At the couple interface, CoSn(3) intermetallic compound (IMC) spallation was observed for the SnBi/amorphous Co(W,P) couple subjected to liquid-state aging. In contrast, no spallation of IMCs was observed for the SnBi/amorphous Co(W,P) couples subjected to solid-state aging. For the SnBi/polycrystalline Co(W,P) couple, a thick IMC layer was observed adjacent to a tungsten-enriched amorphous interfacial layer regardless of aging conditions. IMC formation in all samples indicated that Co(W,P) is essentially a sacrificial barrier to SnBi solder. However, amorphous Co(W,P) might also exhibit stuffed-type barrier behavior due to its relatively high phosphorus (P) content. Analytical results indicated that the P content in Co(W,P) is a crucial factor affecting the structural evolution at the SnBi/electroless Co(W,P) interface.
Diffusion barrier characteristics and shear fracture behaviors of eutectic PbSn solder/electroless Co(W,P) samples
(2012-01-25)
Pan, Hung-Chun
;
Hsieh, Tsung-Eong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Diffusion barrier characteristics, activation energy (E(a)) of IMC growth and bonding properties of amorphous and polycrystalline electroless Co(W,P) (termed as alpha-Co(W,P) and poly-Co(W,P)) to eutectic PbSn solder are presented. Intermetallic compound (IMC) spallation and an nano-crystalline P-rich layer were observed in PbSn/alpha-Co(W,P) samples subjected to liquid-state aging at 250 degrees C. In contrast, IMCs resided on the P-rich layer in PbSn/alpha-Co(W,P) samples subjected to solid-state aging at 150 degrees C. Thick IMCs neigh-boring to an amorphous W-rich layer was seen in PbSn/poly-Co(W,P) samples regardless of the aging type. alpha-Co(W,P) was found to be a sacrificial- plus stuffed-type barrier while poly-Co(W,P) is mainly a sacrificial-type barrier. The values of E(a)'s for PbSn/alpha-Co(W,P) and PbSn/poly-Co(W,P) systems were 338.6 and 167.5 kJ/mol, respectively. Shear test revealed the ductile mode dominates the failure in both alpha- and poly-Co(W,P) samples. Analytical results indicated the high P content in electroless layer might enhance the barrier capability but degrade the bonding strength. (C) 2011 Elsevier B.V. All rights reserved.
Diffusion Barrier Characteristics of Electroless Co(W,P) Thin Films to Lead-Free SnAgCu Solder
(2011)
Pan, Hung-Chun
;
Hsieh, Tsung-Eong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Diffusion barrier and bonding characteristics of amorphous and polycrystalline electroless Co(W,P) layers (alpha-Co(W,P) and poly-Co(W,P)) to SnAgCu (SAC) solder were investigated. In the SAC/alpha-Co(W,P) sample subjected to liquid-state aging at 250 degrees C, the spallation of intermetallic compound (IMC) into solder, a nano-crystalline P-rich layer at SAC/Co(W,P) interface, and the recrystallized Co(W,P) containing Co(2)P precipitates were observed. As to the SAC/alpha-Co(W,P) sample subjected to solid-state aging at 150 degrees C, a thick IMC layer neighboring to the P-rich layer formed at the solder/Co(W,P) interface. Liquid-state aging resulted in an IMC mixture without spallation whereas solid-state aging induced a layer-like IMC in SAC/poly-Co(W,P) samples. Amorphous W-rich layers were also observed in SAC/poly-Co(W,P) samples and it could not inhibit subsequent alloy reactions in the samples. Analytical results indicated the alpha-Co(W,P) is a sacrificial-plus stuffed-type barrier whereas the poly-Co(W,P) is mainly a sacrificial barrier. The activation energies of IMC growth were 110.7 and 81.8 kJ/mol for SAC/alpha-Co(W,P) and SAC/poly-Co(W,P) samples, respectively. High P content in alpha-Co(W,P) was found to degrade the bonding strength to the solder as revealed by the shear test and the control of P content would be a key issue for electroless plating layer applied to under bump metallurgy as the diffusion barrier. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.004111jes] All rights reserved.
Investigation of electroless Co(W,P) thin film as the diffusion barrier of underbump metallurgy
(2008)
Wu, W. C.
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Hsieh, Tsung-Eong
;
Pan, Hung-Chun
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The plating characteristics of an electroless cobalt-tungsten-phosphorus [Co(W,P)] layer and its capability to serve as a diffusion barrier of underbump metallurgy (UBM) for flip-chip Cu-IC are investigated. Increasing the pH of the plating solution in a range of 7.6-9.0 decreased the rate of deposition, increased the phosphorus content, altered the structure from polycrystalline to amorphous, and decreased the surface roughness of Co(W,P) films. The barrier capability of Co(W,P) to eutectic PbSn solder was evaluated by means of liquid- and solid-state aging tests. In specimens subjected to tests of these two types, a P-rich layer presented in between solder and unreacted Co(W,P), demonstrating the sacrificial barrier behavior of Co(W,P). Transmission electron microscopy (TEM) analysis of specimens subjected to liquid-state aging indicated the supersaturated P atoms, and the Co2P consequently formed, might aggregate at grain boundaries of the P-rich layer, thus enabling the stuffed-type barrier capability of the Co(W,P) layer. TEM, scanning electron microscopy, and energy-dispersive spectrometer characterizations of specimens subjected to solid-state aging revealed that the reaction of solder and Co(W,P) implies a formation of CoSn2 and CoSn3 intermetallic compounds (IMCs) and a mixture of various IMCs in P-rich layer. Our experimental results demonstrated a satisfactory barrier property of electroless Co(W,P), heralding promising applications in UBM structures for flip-chip Cu-IC. (C) 2008 The Electrochemical Society.