• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2007.04a
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• pp.49-65
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• 2007

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.11a
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• pp.54-54
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• 2004

• Proceedings of the KWS Conference
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• 2002.05a
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• pp.266-268
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• 2002

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.277-278
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• 2001

• Journal of the Microelectronics and Packaging Society
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• v.13 no.1 s.38
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• pp.23-29
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• 2006

Ultrasonic soldering of Si-wafer to FR-4 PCB at ambient temperature was investigated. The UBM of Si-substrate was Cu/ Ni/ Al from top to bottom with thickness of $0.4{\mu}m,\;0.4{\mu}m$, and $0.3{\mu}m$ respectively. The pad on FR-4 PCB comprised of Au/ Ni/ Cu from top to bottom with thickness of $0.05{\mu}m,\;5{\mu}m$, and $18{\mu}m$ respectively. Sn-3.5wt%Ag foil rolled to $100{\mu}m$ was used for solder. The ultrasonic soldering time was varied from 0.5 s to 3.0 s and the ultrasonic power was 1,400 W. The experimental results show that a reliable bond by ultrasonic soldering at ambient temperature was obtained. The shear strength increased with soldering time up to a maximum of 65 N at 2.5 s. The strength decreased to 34 N at 3.0 s because cracks were generated along the intermetallic compound between Si-wafer and Sn-3.5wt%Ag solder. The Intermetallic compound produced by ultrasonic soldering between the Si-wafer and the solder was $(Cu,Ni)_{6}Sn_{5}$.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.77-86
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• 2008

The reliability of leaded and lead-free solders of BGA type packages on a printed circuit board was investigated by employing the standard drop test and 4-point bending test. Tested solder joints were examined by optical microscopy to identify associated failure mode. Three-dimensional finite element analysis(FEM) with ANSYS Workbench v.11 was carried out to understand the mechanical behavior of solder joints under the influence of bending or drop impact. The results of numerical analysis are in good agreement with those obtained by experiments. Packages in the center of the PCB experienced higher stress than those in the perimeter of the PCB. The solder joints located in the outermost comer of the package suffered from higher stress than those located in center region. In both drop and bending impact tests, the lead-free solder showed better performances than the leaded solders. The numerical analysis results indicated that stress and strain behavior of solder joint were dependent on various effective parameters.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.17-22
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• 2013

We investigated the optimum bonding conditions for thermo-compression bonding of electrodes between flexible printed circuit board(FPCB) and rigid printed circuit board(RPCB) with Sn-58Bi solder as interlayer. In order to figure out the optimum bonding conditions, peel test of FPCB/RPCB joint was conducted. The peel strength was affected by the bonding conditions, such as temperature and time. The fracture energies were calculated through F-x (Force-displacement) curve during peel test and the relationships between bonding conditions and fracture behaviors were investigated. The optimum condition for the thermo-compression bonding with Sn-58Bi solder was found to be temperature of $195^{\circ}C$ and time of 7 s.

• Journal of Welding and Joining
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• v.20 no.4
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• pp.505-509
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• 2002

Pb is considered to be eliminated from solder, due to its toxicity. However, melting temperatures of most Pb-free solders are known higher than that of Sn37Pb. Therefore, there is a difficulty to apply Pb-free solders to electronic industry. Since Sn3Ag8Bi5In has relatively lower melting range as $188~200^{\circ}C$, on this study. Wettability and soldering characteristics of Sn3Ag8Bi5In solder in BGA were investigated to solve for what kind of problem. Zero cross time, wetting time, and equilibrium force of Sn3Ag8Bi5In solder for Cu and plated Cu such as Sn, Ni, and Au/Ni-plated on Cu were estimated. Plated Sn on Cu showed best wettability for zero cross time, wetting time and equilibrium farce. Shear strength of the reflowed joint with Sn3Ag8Bi5In ball in BGA was investigated. Diameter of the ball was 0.5mm, UBM(under bump metallurgy) was $Au(0.5\mu\textrm{m})Ni(5\mu\textrm{m})/Cu(18\mu\textrm{m})$ and flux was RMA type. For the reflow soldering, the peak reflow temperature was changed in the range of $220~250^{\circ}C$, and conveyor speed was 0.6m/min.. The shear strength of Sn3Ag8Bi5In ball showed similar level as those of Sn37Pb. The soldered balls are aged at $110^{\circ}C$ for 36days and their shear strengths were evaluated. The shear strength of Sn3Ag8Bi5In ball was increased from 480gf to 580gf by aging for 5 days.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.1-10
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• 2023

Recently, as the demand for high-performance computers and mobile products increases, semiconductor packages are becoming high-integration and high-density. Therefore, in order to transmit a large amount of data at once, micro bumps such as flip-chip and Cu pillar that can reduce bump size and pitch and increase I/O density are used. However, when the size of the bumps is smaller than 70 ㎛, the brittleness increases and electrical properties decrease due to the rapid increase of the IMC volume fraction in the solder joint, which deteriorates the reliability of the solder joint. Therefore, in order to improve these issues, a layer that serves to prevent diffusion is inserted between the UBM (Under Bump Metallization) or pillar and the solder cap. In this review paper, various studies to improve bonding properties by suppressing excessive IMC growth of micro-bumps through additional layer insertion were compared and analyzed.

• Journal of Welding and Joining
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• v.25 no.2
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• pp.82-88
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• 2007

Sn-3.0Ag-0.5Cu lead fee solder was generally utilized in electronics assemblies. But it is insufficient to research about activation energy(Q) that is applying to evaluate the solder joint reliability of environmental friendly electronics assemblies. Therefore this study investigated Q values which are needed to IMC formation and growth of Sn-3.0Ag-0.5Cu/Cu and Sn-40pb/Cu solder joints during aging treatment. We bonded Sn-3.0Ag-0.5Cu and Sn-40Pb solders on FR-4 PCB with Cu pad$(t=80{\mu}m)$. After reflow soldering, to observe the IMC formation and growth of the solder joints, test specimens were aged at 70, 150 and $170^{\circ}C$ for 1, 2, 5, 20, 60, 240, 960, 15840, 28800 and 43200 min, respectively. SEM and EDS were utilized to analysis the IMCS. From these results, we measured the total IMC$(Cu_6Sn_5+Cu_3Sn)$ thickness of Sn-3.0Ag-0.5Cu/Cu and Sn-40Pb/Cu interface, and then obtained Q values for the IMC$(Cu_6Sn_5,\;Cu_3Sn)$ growth of the solder joints.