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1.
The effects of Zn (1 wt.%, 3 wt.%, and 7 wt.%) additions to Sn-3.5Ag solder and various reaction times on the interfacial
reactions between Sn-3.5Ag-xZn solders and Cu substrates a during liquid-state aging were investigated in this study. The composition and morphological
evolution of interfacial intermetallic compounds (IMCs) changed significantly with the Zn concentration and reaction time.
For the Sn-3.5Ag-1Zn/Cu couple, CuZn and Cu6Sn5 phases formed at the interface. With increasing aging time, the Cu6Sn5 IMC layer grew thicker, while the CuZn IMC layer drifted into the solder and decomposed gradually. Cu5Zn8 and Ag5Zn8 phases formed at the interfaces of Sn-3.5Ag-3Zn/Cu and Sn-3.5Ag-7Zn/Cu couples. With increasing reaction time, the Cu5Zn8 layer grew and Cu atoms diffused from the substrate to the solder, which transformed the Ag5Zn8 to (Cu,Ag)5Zn8. The Cu6Sn5 layer that formed between the Cu5Zn8 layer and Cu was much thinner at the Sn-3.5Ag-7Zn/Cu interface than at the Sn-3.5Ag-3Zn/Cu interface. Additionally, we measured
the thickness of interfacial IMC layers and found that 3 wt.% Zn addition to the solder was the most effective for suppressing
IMC growth at the interfaces. 相似文献
2.
N. Dariavach P. Callahan J. Liang R. Fournelle 《Journal of Electronic Materials》2006,35(7):1581-1592
Soldering with the lead-free tin-base alloys requires substantially higher temperatures (∼235–250°C) than those (213–223°C)
required for the current tin-lead solders, and the rates for intermetallic compound (IMC) growth and substrate dissolution
are known to be significantly greater for these alloys. In this study, the IMC growth kinetics for Sn-3.7Ag, Sn-0.7Cu, and
Sn-3.8Ag-0.7Cu solders on Cu substrates and for Sn-3.8Ag-0.7Cu solder with three different substrates (Cu, Ni, and Fe-42Ni)
are investigated. For all three solders on Cu, a thick scalloped layer of η phase (Cu6Sn5) and a thin layer of ε phase (Cu3Sn) were observed to form, with the growth of the layers being fastest for the Sn-3.8Ag-0.7Cu alloy and slowest for the Sn-3.7Ag
alloy. For the Sn-3.8Ag-0.7Cu solder on Ni, only a relatively uniform thick layer of η phase (Cu,Ni)6Sn5 growing faster than that on the Cu substrate was found to form. IMC growth in both cases appears to be controlled by grain-boundary
diffusion through the IMC layer. For the Fe-42Ni substrate with the Sn-3.8Ag-0.7Cu, only a very thin layer of (Fe,Ni)Sn2 was observed to develop. 相似文献
3.
Morphology of intermetallic compounds formed between lead-free Sn-Zn based solders and Cu substrates
The morphologies of intermetallic compounds formed between Sn-Zn based solders and Cu substrates were investigated in this
study. The investigated solders were Sn-9Zn, Sn-8.55Zn-0.45Al, and Sn-8.55Zn-0.45Al-0.5Ag. The experimental results indicated
that the Sn-9Zn solder formed Cu5Zn8 and CuZn5 compounds on the Cu substrate, while the Al-containing solders formed the Al4.2Cu3.2Zn0.7 compound. The addition of Ag to the Sn-8.55Zn-0.45Al solder resulted in the formation of the AgZn3 compound at the interface between the Al4.2Cu3.2Zn0.7 compound and the solder. Furthermore, it was found that the cooling rate of the specimen after soldering had an effect on
the quantity of AgZn3 compound formed at the interface. The AgZn3 compound formed with an air-cooling condition exhibited a rougher surface and larger size than with a water-quenched condition.
It was believed that the formation of the AgZn3 compound at the interface occurs through heterogenous nucleation during solidification. 相似文献
4.
The effect of Ag content on the wetting behavior of Sn-9Zn-xAg on aluminum and copper substrates during soldering, as well as the mechanical properties and electrochemical corrosion
behavior of Al/Sn-9Zn-xAg/Cu solder joints, were investigated in the present work. Tiny Zn and coarsened dendritic AgZn3 regions were distributed in the Sn matrix in the bulk Sn-9Zn-xAg solders, and the amount of Zn decreased while that of AgZn3 increased with increasing Ag content. The wettability of Sn-9Zn-1.5Ag solder on Cu substrate was better than those of the
other Sn-9Zn-xAg solders but worse than that of Sn-9Zn solder. The wettability of Sn-9Zn-1.5Ag on the Al substrate was also better than
those of the other Sn-9Zn-xAg solders, and even better than that of Sn-9Zn solder. The Al/Sn-9Zn/Cu joint had the highest shear strength, and the shear
strength of the Al/Sn-9Zn-xAg/Cu (x = 0 wt.% to 3 wt.%) joints gradually decreased with increasing Ag content. The corrosion resistance of the Sn-9Zn-xAg solders in Al/Sn-9Zn-xAg/Cu joints in 5% NaCl solution was improved compared with that of Sn-9Zn. The corrosion potential of Sn-9Zn-xAg solders continuously increased with increasing Ag content from 0 wt.% to 2 wt.% but then decreased for Sn-9Zn-3Ag. The
addition of Ag resulted in the formation of the AgZn3 phase and in a reduction of the amount of the eutectic Zn phase in the solder matrix; therefore, the corrosion resistance
of the Al/Sn-9Zn-xAg/Cu joints was improved. 相似文献
5.
G. Ghosh 《Journal of Electronic Materials》2004,33(10):1080-1091
The interfacial reaction between two prototype multicomponent lead-free solders, Sn-3.4Ag-1Bi-0.7Cu-4In and Sn-3.4Ag-3Bi-0.7Cu-4In
(mass%), and Ag, Cu, Ni, and Pd substrates are studied at 250°C and 150°C. The microstructural characterization of the solder
bumps is carried out by scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis. Ambient temperature,
isotropic elastic properties (bulk, shear, and Young’s moduli and Poisson’s ratio) of these solders along with eutectic Sn-Ag,
Sn-Bi, and Sn-Zn solders are measured. The isotropic elastic moduli of multicomponent solders are very similar to the eutectic
Sn-Ag solder. The measured solubility of the base metal in liquid solders at 250°C agrees very well with the solubility limits
reported in assessed Sn-X (X=Ag, Cu, Ni, Pd) phase diagrams. The measured contact angles were generally less than 15° on Cu
and Pd substrates, while they were between 25° and 30° on Ag and Ni substrates. The observed intermediate phases in Ag/solder
couples were Ag3Sn after reflow at 250°C and Ag3Sn and ζ (Ag-Sn) after solid-state aging at 150°C. In Cu/solder and Ni/solder couples, the interfacial phases were Cu6Sn5 and (Cu,Ni)6Sn5, respectively. In Pd/solder couples, only PdSn4 after 60-sec reflow, while both PdSn4 and PdSn3 after 300-sec reflow, were observed. 相似文献
6.
Several near-eutectic solders of (1) Sn-3.5Ag, (2) Sn-3.0Ag-0.7Cu, (3) Sn-3.0Ag-1.5Cu, (4) Sn-3.7Ag-0.9Cu, and (5) Sn-6.0Ag-0.5Cu
(in wt.% unless specified otherwise) were cooled at different rates after reflow soldering on the Cu pad above 250°C for 60
sec. Three different media of cooling were used to control cooling rates: fast water quenching, medium cooling on an aluminum
block, and slow cooling in furnace. Both the solder composition and cooling rate after reflow have a significant effect on
the intermetallic compound (IMC) thickness (mainly Cu6Sn5). Under fixed cooling condition, alloys (1), (3), and (5) revealed larger IMC thicknesses than that of alloys (2) and (4).
Slow cooling produced an IMC buildup of thicker than 10 μm, while medium and fast cooling produced a thickness of thinner
than 5 μm. The inverse relationship between IMC thickness and shear strength was confirmed. All the fast- and medium-cooled
joints revealed a ductile mode (fracture surface was composed of the β-Sn phase), while the slow-cooled joints were fractured
in a brittle mode (fracture surface was composed of Cu6Sn5 and Cu3Sn phases). The effect of isothermal aging at 130°C on the growth of the IMC, shear strength, and fracture mode is also reported. 相似文献
7.
The creep behavior of Sn-1Ag-0.5Cu, Sn-2.5Ag-1Cu and Sn-4Ag-0.5Cu ball grid array (BGA) solder balls and 99.99% pure polycrystalline
bulk Sn was studied using impression creep and related to the microstructure. Sn-Ag-Cu solders generally consist of primary
dendrites/grains of β-Sn, and a eutectic microconstituent comprising fine Ag3Sn and Cu6Sn5 particles in β phase. With increasing concentrations of Ag and Cu in the alloy, the proportion of the eutectic microconstituent in relation
to the primary β phase increases. In pure Sn and Sn-1Ag-0.5Cu, the β grains form the continuous matrix, whereas in Sn-2.5Ag-1Cu and Sn-4Ag-0.5Cu, the eutectic microconstituent forms a continuous
network around the β grains, which form isolated islands within the eutectic. The steady-state creep behavior of the alloys was dominated by the
response of the continuous microstructural constituent (β-Sn or solid solution β for pure Sn and Sn-1Ag-0.5Cu, and the eutectic microconstituent for Sn-2.5Ag-0.5Cu and Sn-4Ag-0.5Cu). In general, the steady-state
creep rate decreased with increasing alloy content, and in particular, the volume fraction of Ag3Sn and Cu6Sn5 precipitates. The rate-limiting creep mechanism in all the materials investigated here was core diffusion controlled dislocation
climb. However, subtle changes in the stress exponent n and activation energy Q were observed. Pure Sn shows n = 5, Q = 42 kJ/mol, Sn-1Ag-0.5Cu shows n = 5, Q = 61 kJ/mol, whereas both Sn-2.5Ag-1Cu and Sn-4Ag-0.5Cu show n = 6 and Q = 61 kJ/mol. Rationalizations for the observed changes of n and Q are provided, based on the influence of the microstructure and the solute concentrations. 相似文献
8.
Microstructural modifications and properties of Sn-Ag-Cu solder joints induced by alloying 总被引:1,自引:0,他引:1
I. E. Anderson B. A. Cook J. Harringa R. L. Terpstra 《Journal of Electronic Materials》2002,31(11):1166-1174
Slow cooling (1–3°C/sec) of Sn-Ag-Cu and Sn-Ag-Cu-X (X = Fe, Co) solder-joint specimens, made by hand soldering, simulated
reflow in a surface-mount assembly to achieve similar as-solidified joint microstructures for realistic shear-strength testing,
using Sn-3.5Ag (wt.%) as a baseline. Consistent with predictions from a recent Sn-Ag-Cu ternary phase-diagram study, either
Sn dendrites, Ag3Sn primary phase, or Cu6Sn5 primary phase were formed during solidification of joint samples made from the selected near-eutectic Sn-Ag-Cu alloys. Minor
substitution of Co for Cu in Sn-3.7Ag-0.9Cu refined the joint-matrix microstructure by an apparent catalysis effect on the
Cu6Sn5 phase, whereas Fe substitution promoted extreme refinement of the Sn-dendritic phase. Ambient-temperature shear strength
was reduced by Sn dendrites in the joint microstructure, especially coarse dendrites in solute poor Sn-Ag-Cu, e.g., Sn-3.0Ag-0.5Cu,
while Sn-3.7Ag-0.9Cu with Co and Fe additions have increased shear strength. At elevated (150°C) temperature, no significant
difference exists between the maximum shear-strength values of all of the alloys studied. 相似文献
9.
The solder joint microstructures of immersion Ag with Sn-xZn (x = 0 wt.%, 1 wt.%, 5 wt.%, and 9 wt.%) solders were analyzed and correlated with their drop impact reliability. Addition of
1 wt.% Zn to Sn did not change the interface microstructure and was only marginally effective. In comparison, the addition
of 5 wt.% or 9 wt.% Zn formed layers of AgZn3/Ag5Zn8 at the solder joint interface, which increased drop reliability significantly. Under extensive aging, Ag-Zn intermetallic
compounds (IMCs) transformed into Cu5Zn8 and Ag3Sn, and the drop impact resistance at the solder joints deteriorated up to a point. The beneficial role of Zn on immersion
Ag pads was ascribed to the formation of Ag-Zn IMC layers, which were fairly resistant to the drop impact, and to the suppression
of the brittle Cu6Sn5 phase at the joint interface. 相似文献
10.
In this study, the contact angles of four lead-free solders, namely, Sn-3.5Ag, Sn-3.5Ag-4.8Bi, Sn-3.8Ag-0.7Cu, and Sn-0.7Cu
(wt.%), were measured on copper substrates at different temperatures. Measurements were performed using the sessile-drop method.
Contact angles ranging from 30° to 40° after wetting under vacuum with no fluxes and between 10° and 30° with rosin mildly
activated (RMA) and rosin activated (RA) fluxes were obtained. The Sn-3.5Ag-4.8Bi exhibited the lowest contact angles, indicating
improved wettability with the addition of bismuth. For all soldering alloys, lower contact angles were observed using RMA
flux. Intermetallics formed at the solder/Cu interface were identified as Cu6Sn5 adjacent to the solder and Cu3Sn adjacent to the copper substrate. The Cu3Sn intermetallic phase was generally not observed when RMA flux was used. The effect of temperature on contact angle was dependent
on the type of flux used. 相似文献
11.
Moon Gi Cho Sung K. Kang Da-Yuan Shih Hyuck Mo Lee 《Journal of Electronic Materials》2007,36(11):1501-1509
The effects of Zn additions to Sn-0.7Cu and Sn-3.8Ag-0.7Cu (all in wt.% unless specified otherwise) Pb-free solders on the
interfacial reactions with Cu substrates were investigated. The study was focused on the intermetallic compound (IMC) growth,
Cu consumption and void formation as a function of thermal aging and solder composition. Four different kinds of Cu substrates
(high-purity Cu, oxygen-free Cu, vacuum-sputtered Cu, and electroplated Cu) were prepared to compare their interfacial reaction
behaviors with Zn-added solders. Thermal aging was performed at 150°C for up to 1000 h to accelerate the interfacial reactions
between solders and Cu substrates. Growth of IMCs (Cu6Sn5 and Cu3Sn) in Zn-added solders was slower than those without Zn additions. The growth of the Cu3Sn phase, in particular, was drastically reduced in the Zn-added solders on all four Cu substrates. On an electroplated Cu
substrate, numerous voids were observed in the Cu3Sn phase for Sn-Cu and Sn-Ag-Cu solders aged at 150°C for 1000 h. However, these voids were largely eliminated in the Zn-added
solders. On the other three Cu substrates, the conditions which produce a high density of voids were not found after aging
both solders with and without Zn. The Cu consumption with Zn-added solders was also significantly lower. The beneficial effects
of Zn additions on interfacial reaction behaviors are reported, and the corresponding mechanisms in suppressing void formation
and Cu consumption due to Zn additions will be discussed. 相似文献
12.
In flip chip technology, Al/Ni(V)/Cu under-bump metallization (UBM) is currently applicable for Pb-free solder, and Sn−Ag−Cu
solder is a promising candidate to replace the conventional Sn−Pb solder. In this study, Sn-3.0Ag-(0.5 or 1.5)Cu solder bumps
with Al/Ni(V)/Cu UBM after assembly and aging at 150°C were employed to investigate the elemental redistribution, and reaction
mechanism between solders and UBMs. During assembly, the Cu layer in the Sn-3.0Ag-0.5Cu joint was completely dissolved into
solders, while Ni(V) layer was dissolved and reacted with solders to form (Cu1−y,Niy)6Sn5 intermetallic compound (IMC). The (Cu1−y,Niy)6Sn5 IMC gradually grew with the rate constant of 4.63 × 10−8 cm/sec0.5 before 500 h aging had passed. After 500 h aging, the (Cu1−y,Niy)6Sn5 IMC dissolved with aging time. In contrast, for the Sn-3.0Ag-1.5Cu joint, only fractions of Cu layer were dissolved during
assembly, and the remaining Cu layer reacted with solders to form Cu6Sn5 IMC. It was revealed that Ni in the Ni(V) layer was incorporated into the Cu6Sn5 IMC through slow solid-state diffusion, with most of the Ni(V) layer preserved. During the period of 2,000 h aging, the growth
rate constant of (Cu1−y,Niy)6Sn5 IMC was down to 1.74 × 10−8 cm/sec0.5 in, the Sn-3.0Ag-1.5Cu joints. On the basis of metallurgical interaction, IMC morphology evolution, growth behavior of IMC,
and Sn−Ag−Cu ternary isotherm, the interfacial reaction mechanism between Sn-3.0Ag-(0.5 or 1.5)Cu solder bump and Al/Ni(V)/Cu
UBM was discussed and proposed. 相似文献
13.
This study aims to investigate the reaction of Sn-xAg-0.5Cu (x = 1.0 wt.% and 3.0 wt.%) solders on Cu-yZn (y = 0 wt.%, 15 wt.%, and 30 wt.%) substrates at 250°C for 0.5 min, 2 min, and 10 min, respectively. Cu and Zn atoms dissolve
from the Cu-yZn substrates into the molten solders during reflow, leading to variation of the solder composition. It was revealed that
such composition variation altered the microstructure of the solders. The coarsening of the eutectic region and the decrease
of large-sized Cu6Sn5 compounds inside the Sn-1.0Ag-0.5Cu solder on both Cu-15Zn and Cu-30Zn substrates were correlated with this elemental redistribution.
In addition to the solder matrix, the interfacial reaction was also affected by Zn dissolution. For a Zn concentration of
15 wt.% to 30 wt.% in the Cu-Zn substrate, formation of Cu3Sn was suppressed. An increase of the Zn content in Cu6(Sn,Zn)5 at the solder/Cu-30Zn interface resulted in the formation of a new Cu(Zn,Sn) phase. It was demonstrated that the microstructural
variation and the phase evolution in the solder joints were controlled by the reflow time and the Zn concentration in the
Cu-yZn substrate. 相似文献
14.
Guh-Yaw Jang Jeng-Gong Duh Hideyuki Takahashi Szu-Wei Lu Jen-Chuan Chen 《Journal of Electronic Materials》2006,35(9):1745-1754
Sn-Ag-Cu solder is a promising candidate to replace conventional Sn-Pb solder. Interfacial reactions for the flip-chip Sn-3.0Ag-(0.5
or 1.5)Cu solder joints were investigated after aging at 150°C. The under bump metallization (UBM) for the Sn-3.0Ag-(0.5 or
1.5)Cu solders on the chip side was an Al/Ni(V)/Cu thin film, while the bond pad for the Sn-3.0Ag-0.5Cu solder on the plastic
substrate side was Cu/electroless Ni/immersion Au. In the Sn-3.0Ag-0.5Cu joint, the Cu layer at the chip side dissolved completely
into the solder, and the Ni(V) layer dissolved and reacted with the solder to form a (Cu1−y,Niy)6Sn5 intermetallic compound (IMC). For the Sn-3.0Ag-1.5Cu joint, only a portion of the Cu layer dissolved, and the remaining Cu
layer reacted with solder to form Cu6Sn5 IMC. The Ni in Ni(V) layer was incorporated into the Cu6Sn5 IMC through slow solid-state diffusion, with most of the Ni(V) layer preserved. At the plastic substrate side, three interfacial
products, (Cu1−y,Niy)6Sn5, (Ni1−x,Cux)3Sn4, and a P-rich layer, were observed between the solder and the EN layer in both Sn-Ag-Cu joints. The interfacial reaction
near the chip side could be related to the Cu concentration in the solder joint. In addition, evolution of the diffusion path
near the chip side in Sn-Ag-Cu joints during aging is also discussed herein. 相似文献
15.
This study investigates the effects of various reaction times and Cu contents on the interfacial reactions between Sn-9Zn-xCu alloys and Ni substrates. After aging at 255°C for 1 h to 3 h, the Ni5Zn21 and Cu5Zn8 phases formed at the interface of Sn-9Zn/Ni and Sn-9Zn-1wt.%Cu/Ni couples, respectively. The (Ni,Zn)3Sn4 phase was found in the Sn-9Zn-4wt.%Cu/Ni couple, and the (Cu,Ni)6Sn5 and Cu6Sn5 phases formed, respectively, in the Sn-9Zn-7wt.%Cu/Ni and Sn-9Zn-10wt.%Cu/Ni couples. As the reaction time was increased
from 5 h to 24 h, the (Cu5Zn8 + Ni5Zn21) phases replaced the Cu5Zn8 phase to form in the Sn-9Zn-1wt.%Cu/Ni couple; the (Ni,Zn)3Sn4 phase formed in the Sn-9Zn-4wt.%Cu/Ni couple, and (CuZn + Cu6Sn5) formed in the Sn-9Zn-10wt.%Cu alloys. Experimental results indicate that intermetallic compound (IMC) formation in Sn-9Zn-xCu/Ni couples changes dramatically with reaction time and Cu content. The Sn-Zn-Ni, Sn-Cu-Ni, and Sn-Zn-Cu ternary isothermal
sections greatly help us to understand the IMC evolutions in the Sn-9Zn-xCu/Ni couples. 相似文献
16.
The 0.2Co + 0.1Ni dual additives were used to dope a Sn-3.5Ag solder matrix to modify the alloy microstructure and the solder
joint on an organic solderability preservative (OSP) Cu pad. The refined microstructure of the Sn-3.5Ag-0.2Co-0.1Ni solder
alloy or the reduced β-Sn size was attributed to the depressed undercooling achieved by the Co-Ni addition. After soldering
on the OSP Cu pad, a large Ag3Sn plate was formed at the Sn-3.5Ag/OSP solder joint, whereas it was absent at the Sn-3.5Ag-0.2Co-0.1Ni/OSP solder joints.
With isothermal aging at 150°C, large Ag3Sn plates formed at the Sn-3.5Ag/OSP solder joint were still observed. A coarsened and dispersed Ag3Sn phase was found in the solder joints with Co-Ni additions as well. Compared to Cu6Sn5, the (Co,Ni)Sn2 intermetallic compound showed much lower microhardness values. However, (Co,Ni)Sn2 hardness was comparable to that of the Ag3Sn phase. Pull strength testing of Sn-3.5Ag-0.2Co-0.1Ni/OSP revealed slightly lower values than for Sn-3.5Ag/OSP during aging.
Such results are thought be due to the phase transformation of (Co,Ni)Sn2 to (Cu,Co,Ni)6Sn5. 相似文献
17.
The reliability of adhesion strength of the Sn-9Zn-1.5Ag-0.5Bi/Cu during isothermal aging has been investigated. Due to the
growth and decomposition of the intermetallic compound (IMC), the adhesion strength varies with aging at 150°C from 100, 400,
and 700–1,000 h as wetted at 250°C for 60 sec. The IMC layers are determined at the Sn-9Zn-1.5Ag-0.5Bi/Cu interface by an
x-ray diffractometer (XRD), an optical microscope (OM), a scanning electron microscope (SEM), an energy-dispersive spectroscope
(EDS), and a transmission electron microscope (TEM). The adhesion strength has been investigated by the pull-off test. The
results show that the Cu6Sn5, Cu5Zn8, and Ag3Sn IMCs are identified at the Sn-9Zn-1.5Ag-0.5Bi/Cu interface as aging. The adhesion strengths are 12.44±0.58, 8.57±0.43,
5.50±0.78, 4.32±0.78, and 3.32±0.43 MPa for aging times of 0 h, 100 h, 400 h, 700 h, and 1,000 h, respectively. 相似文献
18.
Immersion Ag is a promising candidate Pb-free surface finish on printed circuit boards (PCBs). For flexible PCB and optoelectronic
packaging, solid-state bonding rather than reflow is commonly used to join the chips to the PCB with Sn-based solders, after
which the immersion Ag layer remains at the joint interface and participates in the interfacial reactions at the solder joints.
Solder joint samples composed of a Sn/Ag/Cu trilayer on flexible PCBs were prepared to study the interfacial reactions at
150°C and 200°C. Three phases, Ag3Sn, Cu6Sn5, and Cu3Sn, were sequentially formed at the interface. Remarkable change of the morphology of the Ag3Sn phase was observed during thermal aging. The thickness of the immersion Ag layer was found to have significant effects
on the growth rates of the Cu6Sn5 and Cu3Sn phases and the void formation in the Cu3Sn phase. 相似文献
19.
Solid-state intermetallic compound layer growth between copper and 95.5Sn-3.9Ag-0.6Cu solder 总被引:4,自引:0,他引:4
Long-term, solid-state intermetallic compound (IMC) layer growth was examined in 95.5Sn-3.9Ag-0.6Cu (wt.%)/copper (Cu) couples.
Aging temperatures and times ranged from 70°C to 205°C and from 1 day to 400 days, respectively. The IMC layer thicknesses
and compositions were compared to those investigated in 96.5Sn-3.5Ag/Cu, 95.5Sn-0.5Ag-4.0Cu/Cu, and 100Sn/Cu couples. The
nominal Cu3Sn and Cu6Sn5 stoichiometries were observed. The Cu3Sn layer accounted for 0.4–0.6 of the total IMC layer thickness. The 95.5Sn-3.9Ag-0.6Cu/Cu couples exhibited porosity development
at the Cu3Sn/Cu interface and in the Cu3Sn layer as well as localized “plumes” of accelerated Cu3Sn growth into the Cu substrate when aged at 205°C and t>150 days. An excess of 3–5at.%Cu in the near-interface solder field
likely contributed to IMC layer growth. The growth kinetics of the IMC layer in 95.5Sn-3.9Ag-0.6Cu/Cu couples were described
by the equation x=xo+Atnexp [−ΔH/RT]. The time exponents, n, were 0.56±0.06, 0.54±0.07, and 0.58±0.07 for the Cu3Sn layer, the Cu6Sn5, and the total layer, respectively, indicating a diffusion-based mechanism. The apparent-activation energies (ΔH) were Cu3Sn layer: 50±6 kJ/mol; Cu6Sn5 layer: 44±4 kJ/mol; and total layer: 50±4 kJ/mol, which suggested a fast-diffusion path along grain boundaries. The kinetics
of Cu3Sn growth were sensitive to the Pb-free solder composition while those of Cu6Sn5 layer growth were not so. 相似文献
20.
Hai-Tao Ma Jie Wang Lin Qu Ning Zhao A. Kunwar 《Journal of Electronic Materials》2013,42(8):2686-2695
A rapidly solidified Sn-3.5Ag eutectic alloy produced by the melt-spinning technique was used as a sample in this research to investigate the microstructure, thermal properties, solder wettability, and inhibitory effect of Ag3Sn on Cu6Sn5 intermetallic compound (IMC). In addition, an as-cast Sn-3.5Ag solder was prepared as a reference. Rapidly solidified and as-cast Sn-3.5Ag alloys of the same size were soldered at 250°C for 1 s to observe their instant melting characteristics and for 3 s with different cooling methods to study the inhibitory effect of Ag3Sn on Cu6Sn5 IMC. Experimental techniques such as scanning electron microscopy, differential scanning calorimetry, and energy-dispersive spectrometry were used to observe and analyze the results of the study. It was found that rapidly solidified Sn-3.5Ag solder has more uniform microstructure, better wettability, and higher melting rate as compared with the as-cast material; Ag3Sn nanoparticles that formed in the rapidly solidified Sn-3.5Ag solder inhibited the growth of Cu6Sn5 IMC during aging significantly much strongly than in the as-cast material because their number in the rapidly solidified Sn-3.5Ag solder was greater than in the as-cast material with the same soldering process before aging. Among the various alternative lead-free solders, this study focused on comparison between rapidly solidified and as-cast solder alloys, with the former being observed to have better properties. 相似文献