• Journal of Welding and Joining
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• v.26 no.5
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• pp.43-48
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• 2008

Characteristics of Sn-1.7%Bi-0.7%Cu-0.6%In (hereafter, SBIC) lead-free solder was investigated in this study. The results from SBIC were compared to other lead-free solders such as Sn-3.5%Ag-0.7%Cu (hereafter, SAC), Sn-0.7%Cu (hereafter, SC), and lead-bearing Sn-37%Pb (hereafter, SP) alloy. Tensile properties of bulk solder, wettability, spreading index, bridge and dross were evaluated. As experimental results, tensile strength and elongation of SBIC was 62.5MPa and 21.5%, respectively. The tensile strength was comparable to that of SP solder. The wetting time of SBIC was 1.2 sec at $250^{\circ}C$, and its wetting properties including wetting force were as good as the SAC alloy. However, wettability of the SC was not so good as the SBIC and SAC. The spreading index of SBIC at $250^{\circ}C$ was 71 %, and it was similar level to those of SAC and SC solders. Bridging was not found for all solders of SBIC, SAC and SC in the range from 240 to $260^{\circ}C$. In dross test at $250^{\circ}C$ for an hour, the amount of dross produced from SBIC was about 57% compared to that from SAC.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.2
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• pp.47-53
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• 2000

The fluxless wetting properties of TSM-coated glass substrate were evaluated by the wetting balance method. We could estimate the wettability of the TSM with new parameters obtained from the wetting balance test for one side-coated specimen. It was more effective in wetting to use Cu as a wetting layer and Au as a protection layer than to use Au itself as a wetting layer. The SnSb solder showed better wettability than SnAg, SnBi, and SnIn solders. The contact angle of the one side-coated glass substrate to the Pb-free solders could be calculated from the farce balance equation by measuring the static force and the tilt angle.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.63-69
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• 2007

We investigated interconnection processes using Cu vias for MEMS sensor packages. Ag paste layer was formed on a glass substrate and used as a seed layer for electrodeposition of Cu vias after bonding a Si substrate with through-via holes. With applying electrodeposition current densities of $20mA/cm^2\;and\;30mA/cm^2$ at direct current mode to the Ag paste seed-layer, Cu vias of $200{\mu}m$ diameter and $350{\mu}m$ depth were formed successfully without electrodeposition defects. Interconnection processes for MEMS sensor packages could be accomplished with Ti/Cu/Ti line formation, Au pad electrodeposition, Sn solder electrodeposition and reflow process on the Si substrate where Cu vias were formed by Cu electrodeposition into through-via holes.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.152-159
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• 2007

When the electronics are tested with thermal shock for Pb-free solder joint reliability, there are temperature conditions with use environment but number of cycles for test don't clearly exist. To obtain the long term reliability data, electronic companies have spent the cost and times. Therefore this studies show the test method and number of thermal shock cycles for evaluating the solder joint reliability of electronic components and also research bonding strength variation with formation and growth of intermetallic compounds (IMC). SMD (surface mount device) 3216 chip resistor and 44 pin QFP (quad flat package) was utilized for experiments and each components were soldered with Sn-40Pb and Sn-3.0 Ag-0.5 Cu solder on the FR-4 PCB(printed circuit board) using by reflow soldering process. To reliability evaluation, thermal shock test was conducted between $-40^{\circ}C\;and\;+125^{\circ}C$ for 2,000 cycles, 10 minute dwell time, respectively. Also we analyzed the IMCs of solder joint using by SEM and EDX. To compare with bonding strength, resistor and QFP were tested shear strength and $45^{\circ}$ lead pull strength, respectively. From these results, optimized number of cycles was proposed with variation of bonding strength under thermal shock.

• Journal of Technologic Dentistry
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• v.24 no.1
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• pp.65-71
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• 2002

This study was performed to observe the microhardness change of the surface and the bonding strength between the porcelain and alloy specimens in order to investigate the effects of appended indium, tin and copper on interfacial properties of Au-Pd-Ag alloys. The hardness of castings was measured with a micro-Vicker's hardness tester. The interfacial shear bonding strength between alloy specimen and fused porcelain was measured with a mechanical testing system(MTS 858.20). The microhardness of Au-Pd-Ag alloy was increased by adding indium and tin, but not increased by adding copper. The shear bonding strength of Au-Pd-Ag-Sn alloy and Au-Pd-Ag-Cu alloy showed 87MPa, 57MPa. The higher concentration of adding elements showed the higher shear bonding strength.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.09a
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• pp.233-241
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces strictly related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.37-42
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• 2001

The concerns of the toxicity and health hazard of lead in solders have demanded the research to find suitable lead-free solder alloys. It was discussed that effect of the intermetallic formation and structure on the reliability of solder joints. In this study, lead-free solder alloys with compositions of Sn/3.5Ag/0.75Cu, Sn/2.0Ag/0.5Cu/2.0Bi were applied to the 48 $\mu$BGA packages. Also, the lead-free solder alloys compared with eutectic Sn/37Pb solder using shear test under various aging temperature. Common $\mu$BGA with solder components was aged at $130^{\circ}C$, $150^{\circ}C$ and $170^{\circ}C$. And the each temperature applied to 300, 600 and 900 hours. The thickness of the intermetallics was measured for each condition and the activation energy for their growth was computed. The fracture surfaces were analyzed using SEM (Scanning Electron Microscope) with EDS (Energy Dispersive Spectroscopy). These results for reliability of lead-free interconnections are discussed.

• Journal of Welding and Joining
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• v.29 no.5
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• pp.90-94
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• 2011

Ag metallic particles from nano-scale to submicron-scale are combined with organic solvent to provide fine circuits and interconnection. Ink-jet printing with Ag nano particle inks demonstrated the potentials of the new printed electronics technology. The bonding at the interface between the Ag wiring layer and the various substrates is very important. In this study, the details of interfaces in Ag wiring are investigated primarily by microstructure observation. By adjusting the materials and sintering conditions, nicely formed interfaces between Ag wiring and Cu, Au or organic substrates are achieved. In contrast, transmission electron microscope (TEM) image clearly shows interface debonding between Ag wiring and Sn substrate. Sn oxides are formed on the surface of the Sn plating. The formation of these is a root cause of the interface debonding.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.207-208
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• 2009

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.921.1-921.1
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• 2006