• Journal of the Microelectronics and Packaging Society
• /
• v.29 no.1
• /
• pp.35-41
• /
• 2022

In the era of Fifth-Generation (5G), technology requirements such as Artificial Intelligence (AI), Cloud computing, automatic vehicles, and smart manufacturing are increasing. For high efficiency of electronic devices, research on high-intensity circuits and packaging for miniaturized electronic components is important. A solder paste which consists of small solder powders is one of common solder for high density packaging, whereas an electroplated solder has limitation of uniformity of bump composition. Researches are underway to improve wettability through the addition of nanoparticles into a solder paste or the surface finish of a substrate, and to suppress the formation of IMC growth at the metal pad interface. This paper describes the principles of improving the wettability of solder paste and suppressing interfacial IMC growth by addition of nanoparticles.

• Journal of the Microelectronics and Packaging Society
• /
• v.24 no.1
• /
• pp.45-50
• /
• 2017

We investigated effect of Zn content on shear strengh of Sn-0.7Cu-xZn and OSP surface finished solder joints. Five pastes of Sn-0.7Cu-xZn (x=0, 0.5, 1.0, 1.5, 2.0 wt.%) solders were fabricated by mixing of solder powder and flux using planatary mixer. $180{\mu}m$ diameter solder balls were formed on OSP surface finished Cu electrodes by screen print method, and the reflow process was performed. The shear strength was evaluated with two high shear speeds; 0.01 and 0.1 m/s. The thickness of the intermetallic compound(IMC) layer was decreased with increasing Zn content in Sn-0.7Cu-xZn solder. The highest shear strength was 3.47 N at the Zn content of 0.5 wt.%. As a whole, the shear strength at condition of 0.1 m/s was higher than that of 0.01 m/s because of impact stress. Fracture energies were calculated by F-x (Force-displacement) curve during high speed shear test and the tendency of fracture energy and that of shear strength were good agreement each other. Fracture took place within solder matrix at lower Zn content, and fracture occured near the interface of OSP surface finished Cu electrode and solder at higher Zn content.

• Journal of the Microelectronics and Packaging Society
• /
• v.15 no.4
• /
• pp.51-57
• /
• 2008

In this paper, wetting and interfacial reaction properties for low Ag containing Sn-Ag-Cu Pb-free solder alloy, i.e., Sn-0.3Ag-0.7Cu were investigated and compared with those of Sn-1.0Ag-0.5Cu and Sn-3.0Ag-0.5Cu. Melting behavior and stress-strain curves of some Sn-xAg-xCu alloys were also measured using a differential scanning calorimeter(DSC) and a tensile test machine, respectively. In order to enhance insufficient wetting properties of Sn-0.3Ag-0.7Cu alloy, the improvement of wetting properties were analyzed by applying fluxes containing higher content of halide or indium adding of 0.2wt.% into the solder alloy. It was concluded that the small addition of indium is more effective for the improvement of wettability in low temperature range of $230{\sim}240^{\circ}C$ than applying flux containing higher content of halide.

• Korean Journal of Metals and Materials
• /
• v.46 no.1
• /
• pp.33-38
• /
• 2008

The interfacial reactions and shear strength of pure Sn solder bump were investigated with different under bump metallizations (UBMs) and reflow numbers. Two different UBMs were employed in this study: Cu and Ni. Cu6Sn5 and Cu3Sn intermetallic compounds (IMCs) were formed at the bump/Cu UBM interface, whereas only a Ni3Sn4 IMC was formed at the bump/Ni UBM interface. These IMCs grew with increasing reflow number. The growth of the Cu-Sn IMCs was faster than that of the Ni-Sn IMC. These interfacial reactions greatly affected the shear properties of the bumps.

• Journal of the Korean Society of Safety
• /
• v.30 no.6
• /
• pp.7-11
• /
• 2015

The present study investigates the impact shear strength of thermal aged Sn-3Ag-0.5Cu lead-free solder joints at impact speeds ranging from 0.5 m/s to 2.5 m/s. The specimens were thermal aged for 24, 100, 250 and 1000 hours at $100^{\circ}C$. The experimental results demonstrate that the shear strength of the solder joint decreases with an increase in the load speed and aging time. The shear strength of the solder joint aged averagely decreased by 43% with an increase in the strain rate. For the as-reflowed specimens, the mode II stress intensity factor ($K_{II}$) of interfacial IMC between Sn-3.0Ag-0.5Cu and a copper substrate also was found to decrease from $1.63MPa.m^{0.5}$ to $0.97MPa.m^{0.5}$ in the speed range tested here. The degradations in the shear strength and fracture toughness of the aged solder joints are mainly caused by the growth of IMC layers at the solder/substrate interface.

• Proceedings of the KWS Conference
• /
• 2006.10a
• /
• pp.199-201
• /
• 2006

The wetting balance test was carried out to compare the wettability of Sn-Xwt%Cu($0{\sim}3$wt%) solders. And, IMCs which were formed at interface between solders and substrates were investigated by using XRD(x-ray diffractometer), SEM(scanning electron microscope) and EDS(energy dispersive spectroscope). The value of ${\gamma}_[fl}$ and(${\gamma}_{fs}-{\gamma}_{ls}$) had a tendency to increase with increasing wetting temperature. The activation energy that was calculated between the bare Cu substrate and flux was increased in the following order Sn-0.7wt%Cu(68.42 kJ/mol);Sn-3.0wt%Cu(72.66 kJ/mol);100wt%Sn solder(94.53 kJ/mol).

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.3
• /
• pp.51-56
• /
• 2014

The reliability of solder joint is significantly affected by the property of surface finish. This paper reports on a study of high speed shear energy and failure mode for Sn-4.0wt%Ag-0.5wt%Cu (SAC405) solder joints with the time of Pd activation. The nodule size of electroless Ni-P deposit increased with increasing the time of Pd activation. The roughness (Ra) of electroless Ni-P deposit decreased with increasing the time of Pd activation. Then, with $HNO_3$ vapor, the quasi-brittle and brittle mode of SAC405 solder joint decreased with increasing the time of Pd activation. This results indicate that the increase in the Pd activation time for Electroless Ni/ Electroless Pd/ Immersion Au (ENEPIG) surface finish play a critical role for improving the robustness of SAC405 solder joint.

• Proceedings of the KWS Conference
• /
• 2005.06a
• /
• pp.19-21
• /
• 2005

The ball shea. tests for ball grid array (BGA) and flip chip packages were carried out with different displacement rates to find out the optimum condition of the displacement rate for this test. The BGA packages consisted of two different kinds of solder balls (eutectic Sn-37wt.%Pb and Sn-3.5wt.%Ag) and electroplated Au/Ni/Cu substrate, whereas the flip chip package consisted of electroplated Sn-37Pb solder and Cu UBM. The packages were reflowed up to 10 times, or aged at 443 K up to 21 days. The variation of the displacement rate resulted in the variations of the shear properties such as shear force, displacement rate at break, fracture mode and strain rate sensitivity. The increase in the displacement rate led to the increase of the shear force and brittleness of solder joints.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2003.11a
• /
• pp.63-67
• /
• 2003

Electromigration characteristics of $SnAg_3Cu_{0.7}$ and eutectic SnPb solder were studied using thin stripe-type test structures. Significant changes in the microstructure of two solders were observed after electromigration test, in which the temperature and the current density were varied from 90 to $110^{\circ}C$ and from $4.0\times10^4\;A/cm^2\;to\;9.2\times10^4\;A/cm^2$. In SnAgCu solders, hillocks were main]y observed near the anode end. From resistance measurements, it was calculated that the activation energy of the SnAgCu solder for electromigration was 1.04 eV And in eutectic SnPb without the effect of pads, while depleted region was found near cathode end, Sn-rich hillocks were observed near the anode end. During eutectic SnPb electromigration, it were observed that electromigration behavior had two migration modes.

• Proceedings of the KWS Conference
• /
• 2003.05a
• /
• pp.34-36
• /
• 2003