• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.20 no.2
• /
• pp.187-192
• /
• 2011

UBM(Under Bump Metallurgy) is very important for successful realization of Flip-Chip technology. In this study, it is investigated the interfacial reactions between various Sn-Ag solder alloys and Ni-P/Au UBM and Cu plate finish. It is also evaluated the shear strength by using the micro shear-punch test method for Sn-37Pb alloy, binary and ternary alloys of environment-friendly Pb-free solder alloys which are applied in the electronic packages. In terms of interfacial microstructure, the Pb-free solder joints have thicker IMCs than the Sn-Pb solder joints. The thickness of IMC is related to Reflow time. The IMC has been observed to grow with the increase in Reflow time. As a result of the shear test, in case of Max. shear strength, Pb-free solder showed the highest strength value and Sn-37Pb showed the lowest strength value 10 be generally condition of Reflow time.

• Journal of the Microelectronics and Packaging Society
• /
• v.17 no.1
• /
• pp.55-61
• /
• 2010

An impact bending test method was used to evaluate the reliability for the solder joint of lead-free solder ball. In order to standardize the test method, the four point impact bending test was applied under the conditions of various frequencies and amounts of +/-amplitude respectively. Effects on the results were analysed. The optimum condition for impact bending test achieved in this study was the frequency of 10 Hz, and the amplitude of (+12/-1)~(+15/-1). 3 kinds of surface finishes Cu-OSP (Organic Solderability Preservative), ENIG (Electroless Nickel Immersion Gold), and ENEPIG (Electroless Nickel, Electroless Palladium, Immersion Gold) were used. Fracture surface showed that cracks were initiated and fractured along the intermetallic layer in the case of surface finishes of Cu-OSP and ENIG, while in the case of ENEPIG the cracks were initiated and propagated in the solder region.

• Journal of Welding and Joining
• /
• v.32 no.3
• /
• pp.74-80
• /
• 2014

Due to environmental regulations (RoHS, WEEE and ELV) of the European Union, electronics and automotive electronics have to eliminate toxic substance from their devices and system. Especially, reliability issue of lead-free solder joint is increasing in car electronics due to ELV (End-of-Life Vehicle) banning from 2016. We have prepared engine control unit (ECU) modules soldered with Sn-40Pb and Sn-3.0Ag-0.5Cu (SAC305) solders, respectively. Degradation characteristics of solder joint strength were compared with various conditions of automobile environment such as cabin and engine room. Thermal cycle test (TC, $-40^{\circ}C$ ~ ($85^{\circ}C$ and $125^{\circ}C$), 1500 cycles) were conducted with automotive company standard. To compare shear strength degradation rate with eutectic and Pb-free solder alloy, we measured shear strength of chip components and its size from cabin and engine ECU modules. Based on the TC test results, finally, we have known the difference of degradation level with solder alloys and use environmental conditions. Solder joints degradation rate of engine room ECU is superior to cabin ECU due to large CTE (coefficient of thermal expansion) mismatch in field condition. Degradation rate of engine room ECU is 50~60% larger than cabin room electronics.

• Journal of the Korean Society of Safety
• /
• v.27 no.6
• /
• pp.7-13
• /
• 2012

A lack of study on the dynamic tensile strengths of Sn-based solder joints at high strain rates was the motivation for the present study. A modified miniature Charpy impact testing machine instrumented with an impact sensor was built to quantitatively evaluate the dynamic impact strength of a solder joint under tensile impact loading. This study evaluated the tensile strength of lead-free solder ball joints at strain rates from $1.8{\times}10^3s^{-1}$ and $8.5{\times}10^3s^{-1}$. The maximum tensile strength of the solder ball joint decreases as the load speed increases in the testing range. This tensile strength represented that of the interface because of the interfacial fracture site. The tensile strengths of solder joints between Sn-3.0Ag-0.5Cu and copper substrate were between 21.7 MPa and 8.6 MPa in the high strain range.

• Journal of the Microelectronics and Packaging Society
• /
• v.9 no.4
• /
• pp.1-9
• /
• 2002

The metallurgical reaction properties between the pad consisted of 0.5 $\mu\textrm{m}$Au/5 $\mu\textrm{m}$Ni/Cu layers on a conventional ball grid array (BGA) substrate and In-15 (wt.%)Pb-5Ag solder ball were characterized during the reflow process and solid aging. During the reflow process of 1 to 5 minutes, it was observed that thin $AuIn_2$ or Ni-In intermetallic layer was formed at the interface of solder/pad. The dissolution rate of the Au layer into the molten solder was about $2\times 10^{-3}$ $\mu\textrm{m}$/sec which is remarkably low in comparison with a eutectic Sn-37Pb solder. After solid aging treatment for 500 hrs at $130^{\circ}C$, the thickness of $Ni_{28}In_{72}$ intermetallic layer was increased to about 3 $\mu\textrm{m}$ in all the conditions nevertheless the initial reflow time was different. These result show that In atoms in the solder alloy were diffused through the $AuIn_2$ phase to react with underlaying Ni layer during solid aging treatment. From the microstructural observation and shear tests, the reaction properties between In-15Pb-5Ag alloy and Au/Ni surface finish were analyzed not to trigger Au-embrittlement in the solder joints unlike Sn-37Pb composition.

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

• Korean Journal of Materials Research
• /
• v.19 no.6
• /
• pp.337-343
• /
• 2009

In this study, we optimized Pb-free Sn/Ni plating thickness and conditions were optimized to counteract the environmental regulations, such as RoHS and ELV(End-of Life Vehicles). The $B_{10}$ life verification method was also suggested to have been successful when used with the accelerated life test(ALT) for assessing Pb-free solder joint life of piezoelectric (PZT) ceramic resonator. In order to evaluate the solder joint life, a modified Norris-Landzberg equation and a Coffin-Manson equation were utilized. Test vehicles that were composed of 2520 PZT ceramic resonator on FR-4 PCB with Sn-3.0Ag-0.5Cu for ALT were manufactured as well. Thermal shock test was conducted with 1,500 cycles from $(-40{\pm}2)^{\circ}C$ to $(120{\pm}2)^{\circ}C$, and 30 minutes dwell time at each temperature, respectively. It was discovered that the thermal shock test is a very useful method in introducing the CTE mismatch caused by thermo-mechanical stress at the solder joints. The resonance frequency of test components was measured and observed the microsection views were also observed to confirm the crack generation of the solder joints.

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.3
• /
• pp.43-49
• /
• 2019

In this study, a new approach using graphene oxide (GO) powder-composited Sn-3.0Ag-0.5Cu(in wt.%) solder paste for improving the bending reliability of solder joints between a flexible substrate and small outline package (SOP) was suggested. The GO addition slightly affected the melting temperature, however, the change in the melting temperature was not significant. Meanwhile, we observed the addition of GO could suppress IMC growth and IMC thickness of solder joint during the reflow process. Moreover, the cyclic bending test was also performed for evaluation of reliability in solder joint and we could improve the cyclic bending reliability of solder joint by adding GO powders. For 0.2 wt.% of GO added to the solder joint, the bending lifetime was increased to 20% greater than that without GO. Pull strength and ductility of the solder joint with GO were also higher than those of the joint without GO and it was assumed that this effect by adding GO could contribute to improve cyclic bending reliability of solder joint.

• Journal of Welding and Joining
• /
• v.31 no.1
• /
• pp.6-10
• /
• 2013

• Journal of the Microelectronics and Packaging Society
• /
• v.18 no.4
• /
• pp.1-9
• /
• 2011

Understanding the void characterization in the solder joints has become more important because of the application of lead free solder materials and its reliability in electronic packaging technology. According to the JEDEC 217 standard, it describes void types formed in the solder joints, and divides into some categories depending on the void position and formation cause. Based on the previous papers and the standards related to the void, reliability of the BGA solder joints is determined by the size of void, as well as the location of void inside the BGA solder ball. Prior to reflow soldering process, OSP(organic surface preservative) finished Cu electrode was exposed under $85^{\circ}C$/60%RH(relative humidity) for 168 h. Voids induced by the exposure of $85^{\circ}C$/60%RH became larger and bigger with increasing aging times. The void position has more influence on mechanical strength property than the amount of void growth does.