Influence of nanoparticle addition on the formation and growth of intermetallic compounds (IMCs) in Cu/Sn-Ag-Cu/Cu solder joint during different thermal conditions (original) (raw)
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Intermetallics, 2013
This paper reports on the effects of adding Ni nanoparticles to a Sne3.8Age0.7Cu solder. The nanocomposite was prepared by manual blending of SAC solder paste with various percentages of Ni particles. Results showed that the addition of Ni nanoparticles did not bring any significant change in the onset melting temperature of the solder. An increase in the weight percentage of nanoparticles in the solder caused an increase of the wetting angle and a decrease of spreading rate. Moreover, the addition of Ni nanoparticles changed the interfacial intermetallic compound morphology from a scalloped structure into a planar type structure, enhanced the growth of (Cu,Ni) 6 Sn 5 and suppressed that of Cu 3 Sn. The concentration of Ni in (Cu,Ni) 6 Sn 5 was higher at the solder side compared with the substrate side. No nickel was detected in the Cu 3 Sn phase. Ni nanoparticle additions caused an increase in the interdiffusion coefficient in (Cu,Ni) 6 Sn 5 , but a reduction in Cu 3 Sn. All these effects found in the Ni nanoparticle doped solder are similar to the case when Ni is added as an alloying element. Hence, it is suggested that Ni nanoparticles dissolve into the molten solder and influence the intermetallic compound formation through conventional alloying effects.
2001 Proceedings. 51st Electronic Components and Technology Conference (Cat. No.01CH37220)
Although the primary driver for the current interest in developing lead-free soldering is global market pressure for more environmentally friendly products, the main concern continues to be lead contamination from end-of-life electronic products in landfill sites. In response to existing and impending legislation in Europe and Japan for the elimination of lead from electronic products, the industry has embarked on a number of studies in search of suitable lead-free alternatives. Several reports [1,2] have been published, but there are as yet no drop-in solutions with respect to reflow temperature, joint reliability and assembly costs. Our survey show that the SnAg -Cu alloy is one of the promising lead-free alloys currently being evaluated by industry. There are however a number of issues regarding the use of SnAg -Cu alloys, including the solderability and long-term reliability of the solder joints, which require further study. The lower solderability of SnAg -Cu solder can alter the interface and microstructure of the solder joint formed because of the differing reaction rates between the molten solder and substrate surface. This also has an impact on the nature and extent of the intermetallic compounds formed at the interface, as the intermetallic is generally more brittle than the base metal. This can negatively impact the solder joint reliability. In this paper we report a study on the effect of solder volume on intermetallic layer formation and thickness. For lead-free soldering this could prove to be very important, as a wide range of devices and components of varying joint size, e.g. plastic quad flat pack (PQFP), ball grid array (BGA), chip-scale packaging (CSP), and flip chip, may need to be assembled on a typical board. This means that the nature and thickness of the intermetallic layer formed for each joint size will be different. In the study, solder joints of different sizes representing different devices were used for evaluating the effect of solder volume on intermetallic compound formation. The layer thickness and microstructure were analyzed using scanning electron microscopy (SEM). SEM analysis was also carried out on joint micro-sections, which has undergone temperature cycling to evaluate the effect of intermetallic layer the joint reliability. Our results show that increasing the solder volume (and solder joint size) does not significantly affect the growth of the intermetallic layer thickness. Therefore the intermetallic layer thickness provides the lower limit for solder joint design for ultra-fine pitch flip-chip applications.
Science and Technology of Welding and Joining, 2008
This study investigates the influence of 0-1?5 wt-%Cu addition on the microstructure and the intermetallic compound (IMC) formation of the as soldered Sn-3Ag-1?5Sb-xCu (wt-%) solders and following thermal storage at 150uC for 0, 25, 200 and 600 h, with the intention of identifying the optimum Cu addition for industrial applications. The experimental results show that the melting point of Sn-3Ag-1?5Sb-xCu solder decreases with Cu addition. For Cu additions of 1?0 wt-% or higher, an IMC of Cu 6 Sn 5 particles is dispersed throughout the matrix, resulting in a dispersion strengthening effect, and its size increases with the levels of Cu addition increasing. The coarsened long strip like Cu 6 Sn 5 with a length of more than 100 mm growing from the upper interface of IMC layer into the solder matrix is observed in the solder with 1?5 wt-%Cu addition after thermal storage. Cu 6 Sn 5 grains in the IMC layer develop the ripening grains with a more hexagonal or polygonal shape and smooth edged flat surfaces instead of scallop shape. Additionally, the microhardness of each solder increases with Cu addition and decreases with increasing time of thermal storage at 150uC.
Journal of Materials Engineering and Performance, 2007
This paper presents and discusses issues relevant to solidification of a chosen lead-free solder, the eutectic Sn-3.5%Ag, and its composite counterparts. Direct temperature recordings for the no-clean solder paste during the simulated reflow process revealed a significant amount of undercooling to occur prior to the initiation of solidification of the eutectic Sn-3.5%Ag solder, which is 6.5°C, and for the composite counterparts, it is dependent on the percentage of copper nanopowder. Temperature recordings revealed the same temperature level of 221°C for both melting (from solid to liquid) and final solidification (after recalescence) of the Sn-3.5%Ag solder. Addition of copper nanoparticles was observed to have no appreciable influence on melting temperature of the composite solder. However, it does influence solidification of the composite solder. The addition of 0.5 wt.% copper nanoparticles lowered the solidification temperature to 219.5°C, while addition of 1.0 wt.% copper nanoparticles lowered the solidification temperature to 217.5°C, which is close to the melting point of the ternary eutectic SnAg -Cu solder alloy, Sn-3.7Ag-0.9Cu. This indicates the copper nanoparticles are completely dissolved in the eutectic Sn-3.5%Ag solder and precipitate as the Cu 6 Sn 5 , which reinforces the eutectic solder. Optical microscopy observations revealed the addition of 1.0 wt.% of copper nanoparticles to the Sn-3.5%Ag solder results in the formation and presence of the intermetallic compound Cu 6 Sn 5. These particles are polygonal in morphology and dispersed randomly through the solder matrix. Addition of microsized copper particles cannot completely dissolve in the eutectic solder and projects a sunflower morphology with the solid copper particle surrounded by the Cu 6 Sn 5 intermetallic compound coupled with residual porosity present in the solder sample. Microhardness measurements revealed the addition of copper nanopowder to the eutectic Sn-3.5%Ag solder resulted in higher hardness.
Journal of Electronic Materials, 1999
Single shear lap joints were made with four different solders, Sn-Pb and Sn-Ag eutectic solders, and their composites containing about 20 vol.% in-situ Cu6Sn5 intermetallic phases about 3-8 micrometers in diameter. Two sets of experiments were performed: In the first set, all of the above four solder joints were aged at 150°C for periods ranging to 5000 h and the intermetallic growth was monitored periodically. In the second set, each of the above four solder joints was aged at five different temperatures for 4000 h. The interfacial layers between solders and the Cu substrate were examined using optical and scanning electron microscopy. The growth kinetics of intermetallic interfacial layers formed between solder and Cu substrate was characterized. The effect of in-situ Cu 6 Sn 5 intermetallic phases on the growth rate is discussed. The growth rate of the intermetallic layers in the eutectic Sn-Pb composite was slower for the first 150 h as compared to the eutectic Sn-Pb non-composite. The growth rate of the intermetallic layers were similar for both the eutectic Sn-Ag and eutectic Sn-Ag composite throughout the aging duration. The activation energies for Cu 6 Sn 5 layer growth for the eutectic Sn-Pb and Sn-Ag solder joints are evaluated to be 111 kJ/mol and 116 kJ/mol, respectively. The eutectic Sn-Pb and Sn-Ag composite solder joints exhibit higher activation energies of 161 kJ/mol and 203 kJ/mol.
Journal of Electronic Packaging, 2016
The sandwich structure Cu/Sn/Cu solder joints with different thicknesses of the solder layers (δ) are fabricated using a reflow solder method. The microstructure and composition of the solder joints are observed and analyzed by scanning electron microscopy (SEM). Results show that the thickness of intermetallic compound (IMC) and Cu concentration in the solder layers increase with the decrease of δ after reflow. During thermal aging, the thickness of IMC does not increase according to the parabolic rule with the increase of aging time; the solder joint thickness affects markedly the growth rate of IMC layer. At the beginning of thermal aging, the growth rate of IMC in the thinner solder joints (δ ≤ 25 μm) is higher than that in the thicker ones (δ ≥ 30 μm). The growth rate of IMC (δ ≤ 25 μm) decreases in the thinner solder joints, while increases in the thicker solder joints (δ ≥ 40 μm) and is nearly invariable when the δ equals to 30 μm with aging time extending. The growth rate of...
The effect of adding Zn into the Sn–Ag–Cu solder on the intermetallic growth rate
Journal of Materials Science: Materials in Electronics, 2014
Due to toxicity of lead in the commercial solder, lead-free solders were proposed. Among the potential leadfree solders, the SnAg -Cu solders were considered as a potential replacement. To further improve the solder properties, a fourth element was added into the SnAg -Cu solder. The present study investigates the effect of different weight percentage of Zn (up to 0.7 wt%) into the Sn-3.5Ag-1.0Cu solder on intermetallic and growth rate (k) after long time thermal aging. The solders were prepared using powder metallurgy method and X-ray diffraction analysis shows that there were Cu 6 Sn 5 , Cu 3 Sn, CuZn and Ag 3 Sn phases present after solder preparation. The solders were reacted with Cu substrate at 250°C for 1 min and aged at 150°C until 1,000 h. The morphology of the intermetallic was observed under scanning electron microscope and the elemental distribution was confirmed by energy dispersive X-ray. Intermetallic thickness and growth kinetic result show that the additions of 0.4 % zinc is sufficient in retarding the Cu 6 Sn 5 and Cu 3 Sn intermetallic growth.
Journal of Electronic Materials, 2003
Intermetallic-layer formation and growth in Pb-free solder joints, during solder reflow or subsequent aging, has a significant effect on the thermal and mechanical behavior of solder joints. In this study, the influence of initial intermetallic morphology on growth rate, and kinetics were examined in a Sn-3.5Ag solder reflowed on Cu. The initial morphology of the intermetallic was tailered by cooling in water, air, or furnace conditions. Solder aging was conducted at 100°C, 140°C, and 175°C and aged for 0-1,000 h. Cooling rate, aging temperature, and aging time played an important role on microstructure evolution and growth kinetics of Cu 6 Sn 5 (η) and Cu 3 Sn (ε) intermetallic layers. Prior to aging, faster cooling rates resulted in a relatively planar Cu 6 Sn 5 layer, while a nodular Cu 6 Sn 5 morphology was present for slower cooling. Intermetallic-growth rate measurements after aging at various times, indicated a mixed growth mechanism of grain-boundary and bulk diffusion. These mechanisms are discussed in terms of the initial intermetallic thickness and morphology controlled by cooling rate, diffusion kinetics, and the competition between Cu 6 Sn 5 and Cu 3 Sn growth.
Influence of intermetallic compounds growth on properties of lead-free solder joints
2012 35th International Spring Seminar on Electronics Technology, 2012
influence of these IMCs on properties of soldered joints. The test specimens of printed circuit boards (PCBs) with different surface finishes were made for this experiment. Tin_G (galvanic tin), Tin_C (immersion tin), Cu (pure copper), OSP (organic solderability preservative) and ENIG (electroless nickel immersion gold) surface finishes were chosen. The soldered joints were created on the test specimens by reflow soldering process concretely vapour-phase soldering. The surface mount solder joints of LCCC resistor of size 1206 were studied. Two lead-free solder paste and one tin-lead solder paste were chosen for research of IMCs and their influence on properties of soldered joints. The test specimens were exposed to elevated aging for research of IMCs growth in solder joint. The specimens were thermal stressed in hot air oven at the temperature of 150°C for a periods of 0, 1, 2, 4, 8, and 16 days. The shear test was used for research of IMCs growth influence on strength of soldered joints. The results of analysis of IMCs in solder joints using confocal and metallographic microscopes and the results of shear strength measurement will be presented in this article.