Evaluation of Thermal Shock Characteristic and Wettability of Melt Pb-Free Solder about Al2O3/Fe Composites

Purpose The impact strength of solder joint under high strain rate was evaluated by board level test method. However, the impact shear test of single solder bump was more convenient and economical than the board level test method. With the miniaturization of solder joints, solder joints were more prone to failure under thermal shock and more attention has been paid to the impact reliability of solder joint. But Pb-free solder joints may be paid too much attention and Sn-Pb solder joints may be ignored. Design/methodology/approach In this study, thermal shock test between −55°C and 125°C was conducted on Sn-37Pb solder bumps in the BGA package to investigate microstructural evolution and growth mechanism of interfacial intermetallic compounds (IMCs) layer. The effects of thermal shock and ball diameter on the mechanical property and fracture behavior of Sn-37Pb solder bumps were discussed. Findings With the increase of ball size, the same change tendency of shear strength with thermal shock cycles. The shear strength of the solder bumps was the highest after reflow; with the increase of the number of thermal shocks, the shear strength of the solder bumps was decreased. But at the time of 2,000 cycles, the shear strength was increased to the initial strength. Minimum shear strength almost took place at 1,500 cycles in all solder bumps. The differences between maximum shear strength and minimum shear strength were 9.11 MPa and 16.83 MPa, 17.07 MPa and 15.59 MPa in φ0.3 mm and φ0.4 mm, φ0.5 mm and φ0.6 mm, respectively, differences were increased with increasing of ball size. With similar reflow profile, the thickness of IMC decreased as the diameter of the ball increased. The thickness of IMC was 2.42 µm and 2.17 µm, 1.63 µm and 1.77 µm with increasing of the ball size, respectively. Originality/value Pb-free solder was gradually used to replace traditional Sn-Pb solder and has been widely used in industry. Nevertheless, some products inevitably used a mixture of Sn-Pb and Pb-free solder to make the transition from Sn-Pb to Pb-free solder. Therefore, it was very important to understand the reliability of Sn-Pb solder joint and more further research works were also needed.

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Evolution of microstructure and failure mechanism of lead-free solder interconnections in power cycling and thermal shock tests

Microelectronics Reliability ◽

10.1016/j.microrel.2006.07.095 ◽

2007 ◽

Vol 47 (7) ◽

pp. 1135-1144 ◽

Cited By ~ 54

Author(s):

T. Laurila ◽

T. Mattila ◽

V. Vuorinen ◽

J. Karppinen ◽

J. Li ◽

...

Keyword(s):

Thermal Shock ◽

Failure Mechanism ◽

Lead Free ◽

Lead Free Solder ◽

Power Cycling ◽

Free Solder ◽

Evolution Of Microstructure

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Correlation Between Pin Misalignment and Crack Length in THT Solder Joints

Archives of Metallurgy and Materials ◽

10.1515/amm-2017-0154 ◽

2017 ◽

Vol 62 (2) ◽

pp. 1063-1066

Author(s):

A. Molnar ◽

M. Benke ◽

Z. Gacsi

Keyword(s):

Crack Propagation ◽

Crack Length ◽

Thermal Shock ◽

Solder Joints ◽

Lead Free ◽

Temperature Profiles ◽

Lead Free Solder ◽

Solder Alloys ◽

Free Solder

AbstractIn this manuscript, correlations were searched for between pin misalignments relative to PCB bores and crack propagation after cyclic thermal shock tests in THT solder joints produced from lead-free solder alloys. In total, 7 compositions were examined including SAC solders with varying Ag, Cu and Ni contents. The crack propagation was initiated by cyclic thermal shock tests with 40°C / +125°C temperature profiles. Pin misalignments relative to the bores were characterized with three attributes obtained from one section of the examined solder joints. Cracks typically originated at the solder/pin or solder/bore interfaces and propagated within the solder. It was shown that pin misalignments did not have an effect on crack propagation, thus, the solder joints’ lifetime.

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Effect of Dwell Times and Ramp Rates on the Thermal Cycling Reliability of Pb-Free Wafer-Level Chip Scale Packages: Experiments and Modeling

Electronic and Photonic Packaging, Electrical Systems Design and Photonics, and Nanotechnology ◽

10.1115/imece2006-13376 ◽

2006 ◽

Cited By ~ 1

Author(s):

S. Chaparala ◽

J. M. Pitarresi ◽

M. Meilunas

Keyword(s):

Finite Element ◽

Thermal Cycling ◽

Thermal Shock ◽

Dwell Time ◽

Experimental Testing ◽

Lead Free ◽

Temperature Extremes ◽

Wafer Level ◽

Ramp Rate ◽

Free Solder

Lead-free (Pb-free) solder has seen increasing use in interconnect systems for electronic packages due to legislative and marketing pressures. The NEMI selected eutectic Sn3.9Ag0.6Cu alloy (or a close variation near eutectic Sn3.5Ag1.0Cu used in this study) is a leading Pb-free substitute for the Sn/Pb solder candidate. The reliability of this Pb-free solder alloy under accelerated thermal cycling and thermal shock testing as a function of testing parameters such as dwell time and ramp rate is critical in qualifying the performance of these Pb-free alternatives with the traditionally used Sn37Pb solder This paper presents the reliability of Pb-free solder joints in wafer level chip scale packages (WLCSPs), which are extensions of flip-chip packaging technology to standard surface mount technology, with external dimensions equal to that of the silicon device [1]. The reliability of these packages under both liquid-to-liquid thermal shock (LLTS) testing and accelerated air-to-air thermal cycling (AATC) conditions, as a function of dwell times and ramp rates is evaluated using extensive experimental testing in combination with finite element analysis. Besides, two asymmetric cycles in which the cold and hot dwell times differ at two temperature extremes were studied. Along with the Pb-free solder, some test vehicles were built using eutectic Sn-Pb solder and evaluated for comparison purposes. Experimental results show that an increase in ramp rate does not adversely affect the solder joint reliability in the case of Pb-free solder. The reliability of lead-free WLCSPs was highly dependent upon the dwell time at the temperature extremes, with this dependency being considerably greater for the lead-free allow than for Sn/Pb at 0°C and 100°C. Accelerated test results show that increasing the dwell time from 280 to 900 seconds reduced the N63.2 of the Sn/Pb samples by 12% and the Pb-free samples by 65%. Reliability during asymmetric cycles resulted in a trend that is similar in two cases studied. A predictive equation was developed to evaluate the characteristic life of the package with respect to the dwell time. Non-linear, finite element (FE) modeling was conducted using temperature dependent creep constitutive relations for the Pb-free solder to understand the experimental trends observed. The FE results predicted the same trend of the package reliability as observed experimentally, with respect to the changing dwell and ramp times. The finite element predictions demonstrated reasonable correlation with the experimental observations.

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Improvement in Thermomechanical Reliability of Low Cost Sn-Based BGA Interconnects by Cr Addition

Metals ◽

10.3390/met8080586 ◽

2018 ◽

Vol 8 (8) ◽

pp. 586 ◽

Cited By ~ 3

Author(s):

Junghwan Bang ◽

Dong-Yurl Yu ◽

Ming Yang ◽

Yong-Ho Ko ◽

Jeong-Won Yoon ◽

...

Keyword(s):

Thermal Shock ◽

Solder Joints ◽

Low Cost ◽

Thermal Shock Test ◽

Shock Condition ◽

Joint Reliability ◽

Cu3sn Layer ◽

Kirkendall Voids ◽

Free Solder ◽

Thermomechanical Reliability

The exemption of Pb-bearing automobile electronics in the End of Life Vehicle (ELV) directive has recently expired, bring an urgent need to find Pb-free alloys that can maintain good performance under high-temperature and vibration conditions for automobile application. In this study, a new lead-free solder, Sn-0.7Cu-0.2Cr (wt.%) alloy, was developed. To evaluate the thermomechanical reliability of the new solder alloy in automobile electronics, a thermal shock test was performed. The results show that the presence of Cr in solder inhibits the growth of interfacial Cu3Sn layer and the formation of Kirkendall voids, which effectively improves the joint reliability under intense thermal shock condition compared with the commercial SAC305 and SC07 solders. Specifically, the shear strength of the Sn-0.7Cu-0.2Cr/Cu solder joints was higher by 23% and 44% than that of SAC305 and SC07 solder joints after 2000 cycles of thermal shock at 1 m/s shear speed.

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