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1.
The microstructural and creep behavior of bulk 63SnPb37 and the Pb-free solder alloy Sn3.9Ag0.6Cu are reported and compared.
The Sn3.9Ag0.6Cu alloy showed much lower absolute creep rates than 63SnPb37. The size and distribution of the intermetallic
compound (IMC) coarsened with increasing creep temperature. A number of coarsened precipitates of Cu6Sn5 segregate around β-Sn grain boundaries. After creep at 80°C and 115°C. the β-Sn particles in the Sn3.9Ag0.6Cu alloy are strongly
aligned at approximately 45° to the uniaxial tension, parallel to the maximum shear-stress planes. The powerlaw-defined stress
exponent significantly increases with increasing stress in both the 63Sn37Pb and Sn3.9Ag0.6Cu alloys; therefore, the Dorn
model is unsuitable for these materials over large stress and temperature ranges. Both sets of experimental data were successfully
fit with the present power-law stress-dependent energy-barrier model and the Garofalo model. However, the application of the
present power-law stress-dependent energy model resulted in a significantly lower estimated variance as compared to the Garofalo
model. 相似文献
2.
The present paper compares the creep and microstructural changes during creep behavior of bulk and thin cast forms of Sn3.9Ag0.6Cu.
The processing parameters of the thin cast material were selected to result in a very fine microstructure analogous to what
occurs in very small size solder electronic interconnections. We found that the thin cast material is less creep resistant
than the bulk material. A comparison of Ag element maps between as-crept bulk and thin cast material shows that the relevant
climb process occurs in a very different environment in the bulk material as compared to the thin cast material. In the bulk
material, the relevant climb process occurs within a finely dispersed intermetallic compound (IMC) eutectic, which covers
broad areas within the material. In the thin cast material, the relevant climb process occurs primarily in the beta-Sn grains
that continuously surround isolated, coarse IMC particles. This resulted in the activation energy of the bulk material being
larger than that for the thin cast material. Finally, it is important to note that the strength deficiency of the thin cast
material is persistent—once the material is cast in thin cast form, it will remain weak in comparison to the bulk material.
Therefore, using data obtained from bulk material samples for the construction of thermomechanical models of very small scale
solder interconnections is likely to result in significant, intrinsic errors. 相似文献
3.
Paul T. Vianco Jerome A. Rejent Alice C. Kilgo 《Journal of Electronic Materials》2004,33(12):1473-1484
Compression creep tests were performed on the 95.5Sn-3.9Ag-0.6Cu (wt.%) solder. The specimens were aged prior to testing at
125°C, 24 h or 150°C, 24 h. Applied stresses were 2–40 MPa. Test temperatures were −25°C to 160°C. The 125°C, 24-h aging treatment
caused the formation of coarsened Ag3Sn particle boundaries within the larger ternary-eutectic regions. The 150°C, 24-h aging treatment resulted in contiguous
Ag3Sn boundaries in the ternary-eutectic regions as well as a general coarsening of Ag3Sn particles. The 125°C, 24-h aging treatment had only a small effect on the strain-time curves vis-à-vis the as-cast condition.
Negative creep was observed at 75°C for time periods >105 sec and stresses of 3–10 MPa. The creep kinetics exhibited a sinh term (stress) exponent, p, of 5.3±0.6 and an apparent-activation
energy, ΔH, of 49±5 kJ/mol when data from all test temperatures were included. A good data correlation was observed over the
[−25–125°C] temperature regime. Steady-state creep kinetics exhibited a greater variability in the [125–160°C] regime because
of the simultaneous coarsening of Ag3Sn particles. The aging treatment of 150°C for 24 h resulted in a more consistent stress dependence and better reproducibility
of the creep curves. Negative creep was observed in samples aged at 150°C for 24 h when tested at −25°C, 25°C, and 75°C. The
values of p and ΔH were 4.9±0.3 kJ/mol and 6±5 kJ/mol, respectively. Only a slight improvement in the data correlation was
observed when the analysis examined separated [−25−75°C] and [75–166°C] temperature regimes. Creep testing did not cause observable
deformation in any of the sample microstructures. 相似文献
4.
Paul T. Vianco Jerome A. Rejent Alice C. Kilgo 《Journal of Electronic Materials》2004,33(11):1389-1400
The compression creep behavior was studied for the ternary solder alloy 95.5Sn-3.9Ag-0.6Cu in the as-cast condition. Samples
were tested under stresses of 2–45 MPa and temperatures of −25–160°C. There was a significant variability in the creep curve
shape, strain magnitude, and steady-state strain-rate properties. A multivariable linear-regression analysis of the steady-state
strain-rate data, using the sinh-law stress representation, indicated two mechanisms distinguished by low- and high-temperature
regimes of −25–75°C and 75–160°C, respectively. The sinh-law stress exponent (n) and apparent-activation energy (ΔH) in the
−25–75°C regime were 4.4 ± 0.7 kJ/mol and 25 ± 7 kJ/mol (63% confidence intervals), respectively. Those same parameters in
the 75–160°C regime were 5.2±0.8 kJ/mol and 95±14 kJ/mol, respectively, for the high-temperature regime. The values of ΔH
suggested a short-circuit diffusion mechanism at low temperatures and a lattice or bulk-diffusion mechanism at high temperatures.
The stress dependency of the steady-state strain rate did not indicate a strong power-law breakdown behavior or a threshold
stress phenomenon. Cracks and grain-boundary sliding were not observed in any of the samples. As the creep temperature increased,
a coarsened particle boundary and particle depletion zone formed in the region of fine Ag3Sn particles that existed between the Sn-rich phase areas. The coarsened particle boundary, as well as accelerated coarsening
of Ag3Sn particles, were direct consequences of the creep deformation process. 相似文献
5.
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
6.
L. Snugovsky C. Cermignani D. D. Perovic J. W. Rutter 《Journal of Electronic Materials》2004,33(11):1313-1315
Early studies of Ag-Sn and Cu-Sn binary alloys showed very low values, 0.04 wt.% for Ag and 0.0063 wt.% for Cu, for the solid
solubility of these elements in Sn at the eutectic temperature. In recent work on “as-cast” Sn-Ag-Cu solder alloys, much higher
values have been reported for the Ag and Cu content of the Sn phase. In the present study, wavelength dispersive x-ray microprobe
measurements made on a near-equilibrium sample confirmed the earlier solubility values. It was concluded that higher values,
some of which are reported in the current paper, represent nonequilibrium, supersaturated solid solutions. 相似文献
7.
The anomalous microstructural,tensile, and aging response of thin-cast Sn3.9Ag0.6Cu lead-free solder
In this study, bulk and thin-cast samples were produced with an identical Sn3.9Ag0.6Cu composition. The thin-cast material
exhibited a much finer as-quenched microstructure than the bulk material with the intermetallic compound (IMC) phase restricted
to a thin network. Both the bulk and thincast materials continually softened during room-temperature aging, while both materials
initially softened and then subsequently hardened when aged at 120°C and 180°C. The thin-cast material was in all cases significantly
softer than the bulk material, and responded to aging as if it were bulk material aged at a higher temperature. These results
have significant implications for the elevated temperature application of Sn3.9Ag0.6Cu. 相似文献
8.
The development of a constitutive model for predicting the thermal-mechanical fatigue (TMF) of 95.5Sn-3.9Ag-0.6Cu (wt.%) Pb-free
solder interconnects requires the measurement of time-independent mechanical and physical properties. Yield stress was measured
over the temperature range of −25–160°C using strain rates of 4.2 × 10−5 s−1 and 8.3 × 10−4 s−1. The yield-stress values ranged from approximately 40 MPa at −25°C to 10 MPa at 160°C for tests performed at 4.2 × 10−5 s−1. The faster strain rate and specimen aging had a limited impact on the yield stress. The true stress/true strain curves indicated
that dynamic-recovery and dynamic-recrystallization processes took place in as-cast samples exposed to temperatures of 125°C
and 160°C, respectively, while tested at a strain rate of 4.2 × 10−5 s−1. Aging the sample prior to testing, as well as a faster strain rate, mitigated both phenomena. Dynamic Young’s modulus values
ranged from 55 GPa at −50°C to 35 GPa at 200°C, while the coefficient of thermal expansion (CTE) increased from approximately
12 × 10−6°C−1 to 24 × 10−6°C−1 for the same temperature range. The aging treatment had little effect on either Young’s modulus or the CTE. 相似文献
10.
Zn-Al-Mg-Ga alloys as Pb-free solder for die-attaching use 总被引:1,自引:0,他引:1
Zn-based alloys have been investigated to replace Pb-5%Sn solder for die-attaching use. We have found that a Zn-4%Al-3%Mg-3%Ga
alloy has a 309°C solidus and a 347°C liquidus. A die-attaching test was done with preforms of this alloy, Ag-plated lead-frames,
and Au-plated dummy dies. Good die-attaching with a small amount of voids can be achieved at 320°C or higher. In subsequent
reliability tests, no failure was observed until 1000 cycles between −65°C and 150°C or until 1000 h at 85°C and 85% humidity.
Although the poor workability and poor ability of stress relaxation at room temperature of this alloy may somewhat limit its
application areas, this solder is the first Pb-free solder for die-attaching use to our knowledge. 相似文献
11.
The experimental tensile creep deformation of bulk Sn-3.8Ag-0.7Cu solder at temperatures between 263 K and 398 K, covering
lifetimes up to 3,500 h, has been rationalized using constitutive equations that incorporate structure-related internal state
variables. Primary creep is accounted for using an evolving internal back stress, due to the interaction between the soft
matrix phase and a more creep-resistant particle phase. Steady-state creep is incorporated using a conventional power law,
modified to include the steady-state value of internal stress. It is demonstrated that the observed behavior is well-fitted
using creep constants for pure tin in the modified creep power law. A preliminary analysis of damage-induced tertiary creep
is also presented. 相似文献
12.
Young-Doo Jeon Kyung-Wook Paik Adreas Ostmann Herbert Reichl 《Journal of Electronic Materials》2005,34(1):80-90
Using the screen-printed solder-bumping technique on the electroless plated Ni-P under-bump metallurgy (UBM) is potentially
a good method because of cost effectiveness. As SnAgCu Pb-free solders become popular, demands for understanding of interfacial
reactions between electroless Ni-P UBMs and Cu-containing Pb-free solder bumps are increasing. It was found that typical Ni-Sn
reactions between the electroless Ni-P UBM and Sn-based solders were substantially changed by adding small amounts of Cu in
Sn-based Pb-free solder alloys. In Cu-containing solder bumps, the (Cu,Ni)6Sn5 phase formed during initial reflow, followed by (Ni,Cu)3Sn4 phase formation during further reflow and aging. The Sn3.5Ag solder bumps showed a much faster electroless Ni-P UBM consumption
rate than Cu-containing solder bumps: Sn4.0Ag0.5Cu and Sn0.7Cu. The initial formation of the (Cu,Ni)6Sn5 phase in SnAgCu and SnCu solders significantly reduced the consumption of the Ni-P UBM. The more Cu-containing solder showed
slower consumption rate of the Ni-P UBM than the less Cu-containing solder below 300°C heat treatments. The growth rate of
the (Cu,Ni)6Sn5 intermetallic compound (IMC) should be determined by substitution of Ni atoms into the Cu sublattice in the solid (Cu,Ni)6Sn5 IMC. The Cu contents in solder alloys only affected the total amount of the (Cu,Ni)6Sn5 IMC. More Cu-containing solders were recommended to reduce consumption of the Ni-based UBM. In addition, bump shear strength
and failure analysis were performed using bump shear test. 相似文献
13.
The Cu alloying effect in the Sn(Cu) solder line has been studied. The Sn0.7Cu solder line has the most serious electromigration
(EM) damage compared to pure Sn and Sn3.0Cu solder lines. The dominant factor for the fast EM rate in Sn0.7Cu could be attributed
to the relatively small grain size and the low critical stress, i.e., the yielding stress of the Sn0.7Cu solder line. Also,
we found that the shortest Sn0.7Cu solder line, 250 μm, has the most serious EM damage among three solder lines of different
lengths. The back stress induced by EM might not play a significant role on the EM test of long solder lines. A new failure
mode of EM test was observed; EM under an external tensile stress. The external stress is superimposed on the stress profile
induced by EM. As a result, the hillock formation was retarded at the anode side, and void formation was enhanced at the cathode. 相似文献
14.
Sn whisker formation on Sn(Cu) finishes has been studied. (1) With respect to the thickness effect, we found that Sn whisker
density for pure Sn and Sn0.7Cu finishes has a linear relationship with the finish thickness. The safety thickness for Sn
and Sn0.7Cu finishes is about 10 μm and 20 μm, respectively. (2) With respect to the alloying effect, we found that Sn whisker
formation could be retarded by increasing Cu content in the Sn(Cu) finishes. We conclude that the Cu additives could reduce
the two major driving forces of the Sn whisker formation, i.e., metal underlayer dissolution and thermal stress. The Cu additives
self-formed a Cu-Sn compound barrier layer, which effectively prevents the reaction and dissolution with the metal underlayer.
On the other hand, the Cu additives precipitated out as Cu-Sn compound in the Sn(Cu) finish layer, which is believed to be
the reason for smaller values of the coefficient of thermal expansion (CTE) for Sn(Cu) alloys. The smaller CTE values results
in a lower thermal stress level in the Sn(Cu) finishes. 相似文献
15.
Jae-Yong Park Rajendra Kabade Choong-Un Kim Ted Carper Steven Dunford Viswanadham Puligandla 《Journal of Electronic Materials》2003,32(12):1474-1482
This paper illustrates the influence of Au addition on the phase equilibria of Sn-Ag-Cu (SAC) near-eutectic alloys and on
the interface reaction with the Cu substrate. From the thermal and microstructural characterization of Sn-3.8Ag-0.7Cu alloys
containing various amounts of Au, it is found that the Au promotes the formation of a quaternary-eutectic reaction at 204.5°C
± 0.3°C. The equilibrium phases in the quaternary-eutectic microstructure are found to be AuSn4, Ag3Sn, βSn, and Cu6Sn5. While the addition of Au to Sn-3.8Ag-0.7Cu alloys is also found to increase liquidus temperature and the temperature ranges
of the phase equilibria field for primary phases, such influences from Au are found to be less pronounced when the alloys
were reacted with the Cu substrate. Because of the formation of the Au-Cu-Sn-ternary interface intermetallic, it is found
that a majority of Au added to the solder is drained from the melt. The drainage of Au reduces the impact of Au on the phase
equilibria of the solder alloys in the joint. It is further found that the involvement of Au in the interface reaction results
in a change of the interface phase morphology from the conventional scallop structure to a compositelike structure consisting
of (AuCu)6Sn5 grains and finely dispersed, βSn islands. 相似文献
16.
运用莱卡显微镜、扫描电镜和能谱分析等手段,研究了稀土元素La的添加量对Sn3.5Ag0.5Cu钎料及其与Cu基体焊接后微观组织及性能的影响。结果表明:添加不同含量的稀土La均能使钎料及其与Cu基体焊接后组织与性能得到改善,其中以w(La)达到0.05%时为最优,显微硬度及剪切强度分别提高14%和10.7%。键参数函数计算结果表明La具有"亲Sn"倾向,可细化钎料组织,降低IMC(界面金属间化合物)的长大驱动力。 相似文献
17.
The correlation between interfacial reactions and mechanical strengths of Sn(Cu)/Ni(P) solder bumps has been studied. Upon
solid-state aging, a diffusion-controlled process was observed for the interfacial Ni-Sn compound formation of the Sn/Ni(P)
reaction couple and the activation energy is calculated to be 42 KJ/mol. For the Sn0.7Cu/Ni(P), in the initial aging, a needle-shaped
Ni-Sn compound layer formed on Ni(P). Then, it was gradually covered by a layer of the Cu-Sn compound in the later aging process.
Hence, a mixture layer of Ni-Sn and Cu-Sn compounds formed at the interface. For the Sn3.0Cu/Ni(P), a thick Cu-Sn compound
layer quickly formed on Ni(P), which retarded the Ni-Sn compound formation and resulted in a distinct Cu-Sn compound/Ni(P)
interface. The shear test results show that the mixture interface of Sn0.7Cu bumps have fair shear strengths against the aging
process. In contrast, the distinct Cu-Sn/Ni(P) interface of Sn3.0Cu solder bumps is relatively weak and exhibits poor resistance
against the aging process. Upon the reflowing process, the gap formation at the Ni(P)/Cu interface caused a fast degradation
in the interfacial strength for Sn solder bumps. For Sn0.7Cu and Sn3.0Cu solder bumps, Ni3P formation was greatly retarded by the self-formed Cu-Sn compound layer. Therefore, Sn(Cu) solder bumps show better shear
strengths over the Sn solder bump. 相似文献
18.
A joint between Sn95.5Ag4Cu0.5 (mass%) solder and an Ag/Pd thick film was soldered by dipping at 260°C for 3–30 sec. Shrinkage
voids and Sn grain growth were characterized as well as their transformation kinetics. Void shrinkage occurred in the zone
near the top surface of the joint. Shrinkage was always accompanied by colonies of ternary/quaternary meta-eutectic that were
the regions solidified last in the joint. The Sn grains accumulated into two bands across the joint during solidification:
one was transverse through the thickness and the other was parallel to the solder pad. 相似文献
19.
The solderability of 95.5Sn-3.9Ag-0.6Cu solder on oxygen-free high-conductivity (OFHC) copper and Au-Ni-plated Kovar was examined
as a function of flux and process temperature. The three solder fluxes included a rosin-based (R) material, a rosin mildly
activated (RMA) flux, and a low-solids (LS) flux. The solderability metric was the contact angle, θC, measured by a meniscometer and wetting-balance techniques. The wetting rate and time to maximum force parameters were also
documented. In most cases, the contact angles for the 95.5Sn-3.9Ag-0.6Cu solder alloy, regardless of the type of flux or temperature,
were higher then those for the 63Sn-37Pb eutectic-solder alloy, indicating a less “solderable” surface. 相似文献
20.
M. S. Yeh 《Journal of Electronic Materials》2002,31(9):953-956
The Sn-20In-2.8Ag solder alloy is a potential lead-free solder for replacing the traditional Sn-Pb solders. In this study,
the mechanical properties of the bulk material are reported by tensile test at various strain rates and temperatures. The
Sn-20In-2.8Ag solder possessed a solidus and liquidus between 170.8°C and 195.5°C. The ultimate tensile strength (UTS) and
elongation were 59.3 MPa and 50.2% at a strain rate of 10−3 s−1 at room temperature. Moreover, the UTS of this alloy decreased, but its elongation increased, with increasing testing temperature.
Stress exponents of Sn-20In-2.8Ag alloy varied from 6.5 at room temperature to 4 at 100°C, and the activation energy for creep
was 51.0 kJ/mol at the higher temperature range from 50°C to 100°C. The typical intergranular creep fracture mode was observed
in Sn-20In-2.8Ag solder during tensile creep deformation. 相似文献