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1.
Mechanical fatigue characteristics of Sn-3.5Ag-X (X=Bi, Cu, Zn and In) solder alloys 总被引:6,自引:0,他引:6
In our previous study, the fatigue life of Sn-3.5Ag-Bi alloy was found to be dominated by the fracture ductility of the alloy
and to obey a modified Coffin-Manson’s law: (Δεp/2D)· N
f
α
, where Δεp is plastic strain range, Nf is fatigue life, and α and=C are nondimensional constants. In this study, copper, zinc, and indium are selected as the third
element, and the effect of these elements on the isothermal fatigue properties of Sn-3.5%Ag alloy has been investigated. The
relationship between fatigue life and crack propagation rate estimated from load drop curve during fatigue test is also discussed.
The addition of copper, indium, and zinc up to 2% slightly decreases the fatigue life of Sn-3.5Ag alloy due to the loss of
ductility, while the life still remains higher than that of tin-lead eutectic alloy. The modified Coffin-Manson’s equation
can also be applied to ternary Sn-3.5Ag-X. It is found that both ductility and fatigue life are significantly responsible
for the load drop rate of the alloy, which reflects the extent of crack propagation. The fatigue life of Sn-3.5Ag-X alloy
is therefore dominated not by the kinds and amount of third element but by the ductility of each alloy. 相似文献
2.
Mechanical fatigue of thin copper foil 总被引:1,自引:0,他引:1
The electrodeposited and the rolled 12 to 35 μm thick copper foils are subjected to the bending/unbending strain-controlled
flex fatigue over a wide range of strain amplitudes. The fatigue life is associated with an increase in electrical resistance
of the specimen beyond a preassigned threshold. For each foil type, in the rolled or as-deposited as well as in the (recrystallization-like)
annealed conditions, the inverse Coffin-Manson (C-M) relationship between strain amplitude (Δε/2) and fatigue life (Nf) is established in the high Δε/2 (low Nf) and the low Δε/2 (high Nf) regimes. The Nf, Δε/2, and C-M slopes (c,b) are utilized to calculate the cyclic strain hardening (n′) and fatigue ductility (Df) parameters. It is shown that for a given foil thickness, an universal relationship exists between Df and the strength (σ) normalized fatigue life (Nf/σ). The propagation of fatigue crack through the foil thickness and across the sample width is related to the unique fine
grain structure for each foil type: pancaked grains for the rolled foil and equiaxed grains for the electrodeposited foil.
The fatal failure corresponds to convergence of the through-thickness and the across-the-width fatigue cracks. The variations
in (i) electrical resistance, (ii) mid-thickness microhardness and grain structure and (iii) dislocation configurations with
fatigue are monitored. Except for a small but significant fatigue induced softening (or hardening), no convincing evidence
of strain localization (and the associated dislocation configurations generally observed for the bulk samples) has been found. 相似文献
3.
Yao Yao Semyon Vaynman Leon M. Keer Morris E. Fine 《Journal of Electronic Materials》2008,37(3):339-346
Sn-Ag-eutectic-based solders are replacing Sn-Pb eutectic solders in the electronics industry. The current paper extends the
recently developed approach based on phase transformation theory, micromechanics, and fracture mechanics to treat fatigue
crack nucleation and propagation for steels and alloys to predict fatigue crack propagation in solder alloys. To verify the
proposed method, fatigue experiments were conducted on Sn-3.5Ag solder alloys. Finite element analysis is performed to predict
the stress intensity factor range ΔK and the required energy U to increase the crack by a unit area. Unified creep-plasticity theory and a cohesive zone model are incorporated to predict
the creep and hysteresis effects on fatigue crack propagation in solder and the interfacial behavior between the solder alloy
and the intermetallic layer, respectively. With U determined numerically, the predicted fatigue crack propagation rate using phase transformation theory is compared with experimental
data for Sn-3.5Ag and Sn-37Pb eutectic solders. Reasonable agreement between theoretical predictions and experimental results
is obtained. 相似文献
4.
By the indirect Archimedean method, the density and the density-temperature relationship of the Sn-40Pb eutectic alloy and
two Pb-free solders, Sn-57Bi and Sn-9Zn eutectic alloys, were measured from room temperature to about 250°C. The results showed
that the density-temperature dependence for each alloy in both solid and melting states can be fitted linearly as ρS(Sn-40Pb)=8.51−8.94×10−4(T−25°C), ρL(Sn-40Pb)=8.15−13.8×10−4(T−Tm); ρS(Sn-57Bi)=8.54−5.86 × 10−4(T−25°C), ρL(Sn-57Bi)=8.51−10.9×10−4(T−Tm); and ρs(Sn-9Zn)=7.22−7.78×10−4(T−25°C), ρL(Sn-9Zn)=6.89−5.88×10 −4(T−Tm), where the density unit was g/cm3. At the melting point, density of the melt of these solders is 8.15 g/cm3, 8.51 g/cm3, and 6.89 g/cm3, respectively. The density decreased 2.6% for Sn-40Pb eutectic alloy during melting, and 2.7% for Sn-9Zn eutectic alloy,
but increased 0.5% for Sn-57Bi eutectic alloy. The excess molar volume for these alloys after mixing at their melting point
is 0.03 cm3/mol for Sn-40Pb, 0.09 cm3/mol for Sn-57Bi, and 0.21 cm3/mol for Sn-9Zn. 相似文献
5.
Chaosuan Kanchanomai Yukio Miyashita Yoshiharu Mutoh 《Journal of Electronic Materials》2002,31(5):456-465
Low-cycle fatigue (LCF) tests on as-cast Sn-3.5Ag, Sn-3Ag-0.5Cu, Sn-3Ag-0.5Cu-1Bi, and Sn-3Ag-0.5Cu-3Bi solders was carried
out using a noncontact strain-controlled system at 20°C with a constant frequency of 0.1 Hz. The addition of Cu does not significantly
affect the fatigue life of eutectic Sn-Ag solder. However, the fatigue life was significantly reduced with the addition of
Bi. The LCF behavior of all solders followed the Coffin-Manson relationship. The fatigue life of the present solders is dominated
by the fracture ductility and can be described by the ductility-modified Coffin-Manson’s relationship. Steps at the boundaries
of dendrite phases were the initiation sites for microcracks for Sn-3.5Ag, Sn-3Ag-0.5Cu, and Sn-3Ag-0.5Cu-1Bi solders, while
for Sn-3Ag-0.5Cu-3Bi solder, cracks initiated along both the dendrite boundaries and subgrain boundaries in the dendrite phases.
The linking of these cracks and the propagation of cracks inside the specimen occurred both transgranularly through eutectic
phases and intergranularly along dendrite boundaries or subgrain boundaries. 相似文献
6.
We developed a new lead-free solder alloy, an Sn-Ag-Cu base to which a small amount of Ni and Ge is added, to improve the
mechanical properties of solder alloys. We examined creep deformation in bulk and through-hole (TH)␣form for two lead-free
solder alloys, Sn-3.5Ag-0.5Cu-Ni-Ge and Sn-3.0Ag-0.5Cu, at elevated temperatures, finding that the creep rupture life of the
Sn-3.5Ag-0.5Cu-Ni-Ge solder alloy was over three times better than that of the Sn-3.0Ag-0.5Cu solder at 398 K. Adding Ni to
the solder appears to make microstructural development finer and more uniform. The Ni added to the solder readily combined
with Cu to form stable intermetallic compounds of (Cu, Ni)6Sn5 capable of improving the creep behavior of solder alloys. Moreover, microstructural characterization based on transmission
electron microscopy analyses observing creep behavior in detail showed that such particles in the Sn-3.5Ag-0.5Cu-Ni-Ge solder
alloy prevent dislocation and movement. 相似文献
7.
Improved mechanical properties in new,Pb-free solder alloys 总被引:7,自引:0,他引:7
The mechanical properties of solders benefit from uniform dispersion of fine precipitates and small effective grain sizes.
Metallurgical methods of attaining such a beneficial microstructure have been investigated in two new, near-eutectic, Pb-free
solder alloys systems—Sn-Zn-In (m.p. ∼188°C) and Sn-Ag-Zn (m.p.∼217°C). It has been found that small alloying additions of
Ag dramatically improve the mechanical properties of the ternary Sn-8Zn-5In alloy. The improvement is attributed to the elimination
of the coarse and nonuniform distribution of plate-like dendrites and refining the effective grain size in the solidified
microstructure. Also, small amounts of Cu dramatically improve the ductility in the ternary Sn-3.5Ag-lZn alloy. The quaternary
Sn-3.5Ag-lZn-0.5Cu has better mechanical properties than the binary Sn-3.5Ag alloy because it has a uniform fine dispersion
of precipitates and a small effective grain size. The combination of high mechanical strength and high ductility is likely
to yield improved fatigue resistance properties in the interconnection of electronic components. 相似文献
8.
The thermal property of lead-free Sn-8.55Zn-1Ag-XAl solder alloys and their wetting interaction with Cu 总被引:1,自引:0,他引:1
The wetting behaviors between the quaternary Sn-8.55Zn-1Ag-XAl solder alloys and Cu have been investigated with the wetting
balance method. The Al contents, x, of the quaternary solder alloys investigated were 0.01–0.45 wt.%. The results of differential
scanning calorimeter (DSC) analysis indicate that the solders exhibit a solid-liquid coexisting range of about 7–10°C. The
solidus temperature of the quaternary Sn-8.55Zn-1Ag-XAl solder alloys is about 198.2°C, while the liquidus temperatures are
205–207°C. The experimental results showed that the wettability of the Sn-8.55Zn-1Ag-XAl solder alloys is improved by the
addition of Al. The mean maximum wetting force of the solders with Cu is within 0.75–1.18 mN and the mean wetting time is
around 1.0–1.1 sec, better than the ∼1.3 sec of eutectic Sn-9Zn and Sn-8.55Zn-1Ag solder alloys. The addition of Al also depresses
the formation of ε-Ag-Zn compounds at the interface between Sn-8.55Zn-1Ag-XAl solders and copper. 相似文献
9.
Alloying effects in near-eutectic Sn-Ag-Cu solder alloys for improved microstructural stability 总被引:7,自引:0,他引:7
I. E. Anderson J. C. Foley B. A. Cook J. Harringa R. L. Terpstra O. Unal 《Journal of Electronic Materials》2001,30(9):1050-1059
This study included a comparison of the baseline Sn-3.5Ag eutectic to one near-eutectic ternary alloy, Sn-3.6 Ag-1.0Cu and
two quaternary alloys, Sn-3.6Ag-1.0Cu-0.15Co and Sn-3.6Ag-1.0 Cu-0.45 Co, to increase understanding of the beneficial effects
of Co on Sn-Ag-Cu solder joints cooled at 1–3 C/sec, typical of reflow practice. The results indicated that joint microstructure
refinement is due to Co-enhanced nucleation of the Cu6Sn5 phase in the solder matrix, as suggested by Auger elemental mapping and calorimetric measurements. The Co also reduced intermetallic
interface faceting and improved the ability of the solder joint samples to maintain their shear strength after aging for 72
hr at 150 C. The baseline Sn-3.5Ag joints exhibited significantly reduced strength and coarser microstructures. 相似文献
10.
Kanchanomai Chaosuan Miyashita Yukio Mutoh Yoshiharu 《Journal of Electronic Materials》2002,31(2):142-151
Low-cycle fatigue tests of as-cast Sn-Ag eutectic solder (96.5Sn/3.5Ag) were performed using a noncontact strain controlled
system at 20°C. The fatigue behavior followed the Coffin-Manson equation with a fatigue-ductility exponent of 0.76. Without
local deformation and stress concentration at contact points between the extensometer and the specimen surface in strain-controlled
fatigue tests, crack initiation and propagation behavior was observed on the specimen surface using a replication technique.
After failure, the longitudinal cross sections were also examined using scanning electron microscopy (SEM). Microcracks initiated
from steps at the boundary between the Sn-dendrite and the Sn-Ag eutectic structure and cavities along the boundaries especially
around the Ag3Sn particles. Stage II crack propagated in mixed manner with intergranular cracks along the Sn-dendrite boundaries and transgranular
cracks through the Sn-dendrites and the Sn-Ag eutectic structure. Propagation of stage II cracks could be expressed by the
relation of dac/dN = 4.7 × 10−11[ΔJ]1.5, where ac is the average crack length and ΔJ is the J-integral range. After fatigue tests, small grains were observed in Sn-dendrites
near the fracture surface. 相似文献
11.
Hsiao-Yun Chen Chih Chen Pu-Wei Wu Jia-Min Shieh Shing-Song Cheng Karl Hensen 《Journal of Electronic Materials》2008,37(2):224-230
Eutectic Sn-3.5wt.%Ag alloy is one of the most promising lead-free solders in low temperature processes for wafer bumping.
Near eutectic composition of deposited alloy films could be readily acquired by pulse electroplating with a proper combination
of active ingredients including K4P2O7, KI, Sn2P2O7, and AgI, as well as polyethylene glycol (PEG), with molecular weights of 200, 600, 2,000, and 4,000, as an inhibitive agent.
Pulse electroplating was carried out with current in alternating polarity to conduct electroplating and electropolishing sequentially.
As a result, alloy films with grains of less than 1 μm and uniform surface morphology can be obtained. The addition of PEG was necessary for the stabilization of the plating baths
to promote a wider process window for the desirable eutectic composition. Electrochemical characterization established that
PEG with molecular weight of 4,000 exhibited the strongest inhibition behavior. In contrast, PEG with molecular weight of
200 demonstrated the least interference. Energy dispersive X-ray and differential scanning calorimeter data confirmed the
formation of eutectic alloy as a function of deposition current density. X-ray diffraction results indicated that a biphasic
structures of β-Sn and ε-Ag3Sn was present in the as-deposited film. 相似文献
12.
C. M. L. Wu M. L. Huang J. K. L. Lai Y. C. Chan 《Journal of Electronic Materials》2000,29(8):1015-1020
A new lead free alloy, Sn-6Bi-2Ag-0.5Cu, has been developed by mechanical alloying and has great potential as a lead-free
solder system. Initial trials on the manufacture of solder joints with this alloy revealed that a high quality bond with copper
could be formed. Its melting range of 193.87°C to 209.88°C is slightly higher than that of eutectic tin-lead solder. Examination
of the microstructure of the as-soldered joints revealed that it mainly consists of small bismuth (1 μm to 2 μm) and Ag3Sn (1 μm) particles finely dispersed in a nearly pure tin matrix with a small amount of η-Cu6Sn5 particles. The Cu-Sn intermetallic compound (IMC) layer formed at solder-copper interface is the η-Cu6Sn5 phase with grain size of 2 μm. The shear strength of the solder joint is higher than that of Sn-37Pb or Sn-3.5Ag. Under shear
loading, fracture occurred at IMC layer-solder interface as well as in the bulk of solder. 相似文献
13.
Low-cycle, lap-shear fatigue behavior of Sn-based, Pb-free solder alloys, Sn-3.5Ag, Sn-3.5Ag-Cu, Sn-3.5Ag-Bi, and Sn-0.7Cu,
were studied at room temperature using specimens with printed circuit board (PCB)/solder/PCB structure under total displacement
of ±10 μm, 12 μm, 15 μm, and 20 μm. The fatigue lives of various solder joint materials, defined as 50% load drop, were correlated
with the fracture paths and analyzed using the Coffin-Manson relation, Morrow’s plastic-energy dissipation model, and Solomon’s
load-drop parameter. The Sn-3.5Ag, Sn-0.7Cu eutectics, and Sn-3.5Ag-Cu ternary alloys showed the same level of fatigue resistance,
while Bi-containing alloys showed substantially worse fatigue properties. Cross-sectional fractography revealed cracks initiated
at the solder wedge near the solder mask and subsequently propagated into the solder matrix in the former group of alloys,
in contrast with the crack propagation along the solder/under bump metallurgy (UBM) interfaces in the Sn-3.5Ag-Bi alloys.
Inferior fatigue resistance of Bi-containing alloys was ascribed to high matrix hardness, high stiffness, possible Bi segregation
to the interface, and high residual stress in the interfacial area. 相似文献
14.
The eutectic Sn-Ag solder alloy is one of the candidates for the Pb-free solder, and Sn-Pb solder alloys are still widely
used in today’s electronic packages. In this tudy, the interfacial reaction in the eutectic Sn-Ag and Sn-Pb solder joints
was investigated with an assembly of a solder/Ni/Cu/Ti/Si3N4/Si multilayer structures. In the Sn-3.5Ag solder joints reflowed at 260°C, only the (Ni1−x,Cux)3Sn4 intermetallic compound (IMC) formed at the solder/Ni interface. For the Sn-37Pb solder reflowed at 225°C for one to ten cycles,
only the (Ni1−x,Cux)3Sn4 IMC formed between the solder and the Ni/Cu under-bump metallization (UBM). Nevertheless, the (Cu1−y,Niy)6Sn5 IMC was observed in joints reflowed at 245°C after five cycles and at 265°C after three cycles. With the aid of microstructure
evolution, quantitative analysis, and elemental distribution between the solder and Ni/Cu UBM, it was revealed that Cu content
in the solder near the solder/IMC interface played an important role in the formation of the (Cu1−y,Niy)6Sn5 IMC. In addition, the diffusion behavior of Cu in eutectic Sn-Ag and Sn-Pb solders with the Ni/Cu UBM were probed and discussed.
The atomic flux of Cu diffused through Ni was evaluated by detailed quantitative analysis in an electron probe microanalyzer
(EPMA). During reflow, the atomic flux of Cu was on the order of 1016−1017 atoms/cm2sec in both the eutectic Sn-Ag and Sn-Pb systems. 相似文献
15.
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
16.
S. R. Agnew A. Yu. Vinogradov S. Hashimoto J. R. Weertman 《Journal of Electronic Materials》1999,28(9):1038-1044
This study investigates discrepancies regarding cyclic softening of Cu processed by severe plastic deformation (SPD). All
samples softened if the microhardnesses before and after fatiguing are compared. However, the effect decreases if the strain
amplitude is small, Δεp <1 × 10−3). Samples with equiaxed subgrains were more resistant to softening and thermal recovery. All samples had “persistent” shear
bands except those tested at the highest amplitudes, Δεp >1 × 10−2. Cu processed by SPD exhibits an enhanced fatigue life at low amplitudes. However, low thermal stability, potential for softening,
and poor low-cycle properties discredit this advantage. 相似文献
17.
Yoshiharu Kariya Yasunori Hirata Masahisa Otsuka 《Journal of Electronic Materials》1999,28(11):1263-1269
Quad Flat Pack (QFP) Leads/Sn-3.5Ag-X (X=Bi and Cu) joint was thermally cycled between 243 K and 403 K or 273 K and 373 K,
and both metallographic examination and mechanical pull test were performed to evaluate thermal fatigue damage of the joint.
The addition of bismuth drastically degrades the thermal fatigue resistance of Sn-3.5Ag solder. On the other hand, the pull
strength of Sn-3.5Ag-Cu solder joints slightly decreased with increasing number of thermal cycles, though it still remains
higher in comparison to that for conventional Sn-37Pb or bismuth containing solder joint. The behavior observed here reflects
the isothermal fatigue properties of bulk solder, because thermal fatigue crack initiates at the surface of solder fillet
and propagates within the fillet in an early stage of fatigue damage. Furthermore, the lead phases lying at the interface
between lead-frame and bismuth containing solder joint may promote the crack propagation at the interface, resulting in the
extremely low thermal fatigue resistance of the joint. 相似文献
18.
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
19.
Ching-Feng Yang Sinn-Wen Chen Kuan-Hsien Wu Tsung-Shune Chin 《Journal of Electronic Materials》2007,36(11):1524-1530
Sn-Zn-Bi alloys are promising Pb-free solders. Interfacial reactions between the Sn-8wt.%Zn-3wt.%Bi (Sn-13.80at.%Zn-1.62at.%Bi)
alloy and the Cu, Ag, and Ni substrates are examined. Two different kinds of substrates, the bulk plate and the electroplating
layer, are used, and the reactions are carried out at 250°C and 220°C. Although the Zn content is only 13.8 at.%, two Zn-Cu
compounds, γ-Cu5Zn8 and ε-CuZn5 phases, are formed in the Sn-13.80at.%Zn-1.62at.%Bi/Cu couples. The ε-CuZn5 phase is scallop shaped, and the γ-Cu5Zn8 phase is planar. In the Sn-13.80at.%Zn-1.62at.%Bi/Ag couples, three Zn-Ag compounds are observed, and they are ε-AgZn3, γ-Ag5Zn8, and ζ-AgZn phases. In the Sn-13.80at.%Zn-1.62at.%Bi/Ni couples, a Zn-Ni compound, γ-Ni5Zn21 phase, is formed. Similar results are found in the couples prepared with an electroplating layer: the reaction phases are
the same, but the growth rates are different. 相似文献
20.
Iver E. Anderson Jason W. Walleser Joel L. Harringa Fran Laabs Alfred Kracher 《Journal of Electronic Materials》2009,38(12):2770-2779
Elemental (X) additions to Sn-3.5Ag-0.95Cu (SAC3595) solder were developed with minimal (<0.25 wt.%) concentration to avoid
pro-eutectic Ag3Sn blades by reducing undercooling (ΔT) and to eliminate thermal-aging-induced embrittlement. Calorimetry and microstructure results on simple Cu/Cu joints identified
0.21Zn, 0.10Mn, and 0.05Al as sufficient to reduce undercooling below that for SAC3595 and to eliminate Ag3Sn blades. A 211°C melting onset for the X = Mn alloys also suggested the discovery of a new quaternary eutectic. Shear testing
and microstructure analysis of larger joints showed that 0.05Al and 0.21Zn additions resulted in reduced as-soldered strength
(30 MPa), like Sn-0.95Cu, but all joints showed ductile failure at about 30 MPa after 1000 h at 150°C. 相似文献