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1.
Kyung-Seob Kim Nam-Kyu Kim Chung-Hee Yu Joong-Jung Kim Eui-Goo Chang 《Journal of Electronic Materials》2004,33(1):70-75
The joint strength and fracture surfaces of Sn-Pb and Au stud bumps for photodiode packages after isothermal aging were studied
experimentally. Aluminum/gold stud bumps and Cu/Sn-Pb solders were adopted and aged for up to 900 h to analyze the effect
of intermetallic compound (IMC) formation. The joint strength decreased with aging time. The diffraction patterns of Cu6Sn5, scallop-shaped IMCs, and planar-shaped Cu3Sn were characterized by transmission electron microscopy (TEM). The IMCs between Au stud bumps and Al pads was identified
as AlAu2. The formation of Kirkendall voids and the growth of IMCs at the solder joint were found to be a possible mechanism for joint
strength reduction. 相似文献
2.
The microstructure of the ultrasmall eutectic Bi-Sn solder bumps on Au/Cu/Ti and Au/Ni/Ti under-bump metallizations (UBMs)
was investigated as a function of cooling rate. The ultrasmall eutectic Bi-Sn solder bump, about 50 μm in diameter, was fabricated
by using the lift-off method and reflowed at various cooling rates using the rapid thermal annealing system. The microstructure
of the solder bump was observed using a backscattered electron (BSE) image and the intermetallic compound was identified using
energy dispersive spectroscopy (EDS) and an x-ray diffractometer (XRD). The Bi facet was found at the surface of the ultrasmall
Bi-Sn solder bumps on the Au/Cu/Ti UBM in almost all specimens, and the interior microstructure of the bumps was changed with
the solidification rate. The faceted and polygonal intermetallic compound was found in the case of the Bi-Sn solder bump on
the Au (0.1 μm)/Ni/Ti UBM, and it was confirmed to be the (Au1−x−yBixNiy)Sn2 phase by XRD. The intermetallic compounds grown form the Au (0.1 μm)/Ni/Ti UBM interface, and they interrupted the growth
of Bi and Sn phases throughout the solder bump. The ultrasmall eutectic Bi-Sn solder bumps on the Au (0.025 μm)/Ni/Ti UBM
showed similar microstructures to those on the Au/Cu/Ti UBM. 相似文献
3.
Yu-Chih Liu Wei-Hong Lin Hsiu-Jen Lin Tung-Han Chuang 《Journal of Electronic Materials》2006,35(1):147-153
During the reflow process of Sn-8Zn-20In solder joints in the ball grid array (BGA) packages with Au/Ni/Cu and Ag/Cu pads,
the Au and Ag thin films react with liquid solder to form γ3-AuZn4/γ-Au7Zn18 and ε-AgZn6 intermetallics, respectively. The γ3/γ intermetallic layer is prone to floating away from the solder/Ni interface, and the appearance of any interfacial intermetallics
cannot be observed in the Au/Ni surface finished Sn-8Zn-20In packages during further aging treatments at 75°C and 115°C. In
contrast, ε-CuZn5/γ-Cu5Zn8 intermetallics are formed at the aged Sn-8Zn-20In/Cu interface of the immersion Ag BGA packages. Bonding strengths of 3.8N
and 4.0N are found in the reflowed Sn-8Zn-20In solder joints with Au/Ni/Cu and Ag/Cu pads, respectively. Aging at 75°C and
115°C gives slight increases of ball shear strength for both cases. 相似文献
4.
Electroless Ni/Immersion Au interconnects: Investigation of black pad in wire bonds and solder joints 总被引:1,自引:0,他引:1
Black Pad was observed on Electroless Ni/Immersion Au (ENIG) wire bond pads. Thick immersion Au on highly corroded electroless
Ni was detected. It was determined that the pads were electrically connected to the Cu ground plane due to a Ni bridge formed
inside normally open photovias. The mechanism of the bridge formation was verified and preventative actions were taken; it
was demonstrated that formation of Black Pad could be switched on and off. The mechanism of Black Pad formation is proposed
to be defective ENIG plating involving variation of both the electroless Ni and immersion Au plating processes. The intermetallic
structures of solder joints on the above pads were studied. The study was conducted on both defective and non-defective pads
to show differences in intermetallic structure and composition. Me2Sn4 and Me2Sn2 (Me=Cu, Ni, and Au) intermetallics were formed on non-defective pads, which nucleated on the Ni layer and grew inside the
molten solder. However, only the Me3Sn intermetallic was formed on defective pads inside the corroded Ni Layer. Both mechanisms of intermetallic formation were
found on pads with mildly corroded Ni and intermediate Au thickness (4.5–7 in). 相似文献
5.
During the reflowing of Sn-9Zn solder ball grid array (BGA) packages with Au/Ni/Cu and Ag/Cu pads, the surface-finished Au
and Ag film dissolved rapidly and reacted with the Sn-9Zn solder to form a γ3-AuZn4/γ-Au7Zn18 intermetallic double layer and ε-AgZn6 intermetallic scallops, respectively. The growth of γ3-AuZn4 is prompted by further aging at 100°C through the reaction of γ-Au7Zn18 with the Zn atoms dissolved from the Zn-rich precipitates embedded in the β-Sn matrix of Sn-9Zn solder BGA with Au/Ni/Cu
pads. No intermetallic compounds can be observed at the solder/pad interface of the Sn-9Zn BGA specimens aged at 100°C. However,
after aging at 150°C, a Ni4Zn21 intermetallic layer is formed at the interface between Sn-9Zn solder and Ni/Cu pads. Aging the immersion Ag packages at 100°C
and 150°C caused a γ-Cu5Zn8 intermetallic layer to appear between ε-AgZn6 intermetallics and the Cu pad. The scallop-shaped ε-AgZn6 intermetallics were found to detach from the γ-Cu5Zn8 layer and float into the solder ball. Accompanied with the intermetallic reactions during the aging process of reflowed Sn-9Zn
solder BGA packages with Au/Ni/Cu and Ag/Cu pads, their ball shear strengths degrade from 8.6 N and 4.8 N to about 7.2 N and
2.9 N, respectively. 相似文献
6.
With miniaturization of the interconnect solder bumps, high current density causes serious reliability issues (stress, electromigration etc.) in electronic packages. Through Au stud bumping on the chips and following reflow of solder to produce hybrid interconnects, the eletromigration resistance may be improved by the intermetallics formed inside them due to their barrier effects on the atoms migration. Here, microstructures and reliabilities of Au stud with serial amounts of Sn-0.7Cu solder paste were studied through controlling size of stencil printing aperture. After reflow, AuSn, AuSn2 and AuSn4 formed from the surface of Au stud bump to the solder. A layer of (Cu,Au)6Sn5 with thickness of 3 μm existed at the interface near the Cu substrate with a scallop shape similar to Cu6Sn5. The fraction of intermetallics to the mixed joints varied with the solder amount. Shear strength decreased slightly when comparing with the sole solder joint due to large amounts of brittle intermetallics. Thermal aging resulted in many Kirkendall voids generated at the interfaces of Au stud and the solder, which further decreased the shear strength. The effect of solder amount on microstructural evolution and fracture modes was discussed. The hybrid interconnects showed a good electromigration resistance. 相似文献
7.
Chin-Su Chi Hen-So Chang Ker-Chang Hsieh C. L. Chung 《Journal of Electronic Materials》2002,31(11):1203-1207
Ball-grid array (BGA) samples were aged at 155°C up to 45 days. The formation and the growth of the intermetallic phases at
the solder joints were investigated. The alloy compositions of solder balls included Sn-3.5Ag-0.7Cu, Sn-1.0Ag-0.7Cu, and 63Sn-37Pb.
The solder-ball pads were a copper substrate with an Au/Ni surface finish. Microstructural analysis was carried out by electron
microprobe. The results show that a ternary phase, (Au,Ni)Sn4, formed with Ni3Sn4 in the 63Sn-37Pb solder alloy and that a quaternary intermetallic phase, (Au,Ni)2Cu3Sn5, formed in the Sn-Ag-Cu solder alloys. The formation mechanism of intermetallic phases was associated with the driving force
for Au and Cu atoms to migrate toward the interface during aging. 相似文献
8.
Characterization of small-sized eutectic Sn-Bi solder bumps fabricated using electroplating 总被引:1,自引:0,他引:1
We studied the effects of the cooling rate during the reflow process on the microstructure of eutectic Sn-Bi solder bumps
of various sizes fabricated by electroplating. To fabricate eutectic Sn-Bi solder bumps of less than 50 μm in diameter, Sn-Bi
alloys were electroplated on Cu pads and reflowed at various cooling rates using the rapid thermal annealing system. The interior
microstructure of electroplated bumps showed a fine mixture of Sn-rich phases and Bi-rich phases regardless of the cooling
rate. Such an interior microstructure of electroplated bumps was quite different from the reported microstructure of vacuum-evaporated
bumps. Ball shear tests were performed to study the effects of the cooling rate on the shear strength of the solder bumps
and showed that the shear strength of the bumps increased with increasing cooling rate probably due to the reduced grain size.
Soft fractures inside the solder bump were observed during the ball shear test regardless of the cooling rate. 相似文献
9.
The intermetallic compounds formed in Sn3Ag0.5Cu and Sn3Ag0.5Cu0.06Ni0.01Ge solder BGA packages with Ag/Cu pads are investigated.
After reflow, scallop-shaped η-Cu6Sn5 and continuous planar η-(cu0.9Ni0.1)6Sn5 intermetallics appear at the interfaces of the Sn3Ag0.5Cu and Sn3Ag0.5Cu0.06Ni0.01Ge solder joints, respectively. In the
case of the Sn3Ag0.5Cu specimens, an additional ε-Cu3Sn intermetallic layer is formed at the interface between the η-Cu6Sn5 and Cu pads after aging at 150°C, while the same type of intermetallic formation is inhibited in the Sn3Ag0.5Cu0.06Ni0.01Ge
packages. In addition, the coarsening of Ag3Sn precipitates also abates in the solder matrix of the Sn3Ag0.5Cu0.06Ni0.01Ge packages, which results in a slightly higher
ball shear strength for the specimens. 相似文献
10.
T. H. Chuang S. Y. Chang L. C. Tsao W. P. Weng H. M. Wu 《Journal of Electronic Materials》2003,32(3):195-200
The intermetallic compounds formed at the interfaces between In-49Sn solder balls and Au/Ni/Cu pads during the reflow of In-49Sn
solder, ball-grid array (BGA) packages are investigated. Various temperature profiles with peak temperatures ranging from
140°C to 220°C and melting times ranging from 45 sec to 170 sec are plotted for the reflow processes. At peak temperatures
below 170°C, a continuous double layer of intermetallics can be observed, showing a composition of Au(In,Ni)2/Au(In,Ni). Through selective etching of the In-49Sn solders, the intermetallic layer is made up of irregular coarse grains.
In contrast, a number of cubic-shaped AuIn2 intermetallic compounds appear at the interfaces and migrate toward the upper domes of In-49Sn solder balls after reflow
at peak temperatures above 200°C for longer melting times. The upward floating of the AuIn2 cubes can be explained by a thermomigration effect caused by the temperature gradient present in the liquid solder ball.
The intermetallic compounds formed under various reflow conditions in this study exhibit different types of morphology, yet
the ball shear strengths of the solder joints in the In-49Sn BGA packages remain unaffected. 相似文献
11.
The reliability of chip scale package (CSP) components against mechanical shocks has been studied by employing statistical,
fractographic, and microstructural research methods. The components having high tin (Sn0.2Ag0.4Cu) solder bumps were reflow
soldered with the Sn3.8Ag0.7Cu (wt.%) solder paste on Ni(P)|Au- and organic solderability preservative (OSP)-coated multilayer
printed wiring boards (PWBs), and the assemblies were subjected to the standard drop test procedure. The statistically significant
difference in the reliability performance was observed: the components soldered on Cu|OSP were more reliable than those soldered
on Ni(P)|Au. Solder interconnections on the Cu|OSP boards failed at the component side, where cracks propagated through the
(Cu,Ni)6Sn5 reaction layer, whereas interconnections on the Ni(P)|Au boards failed at the PWB side exhibiting the brittle fracture known
also as “black pad.” In the first failure mode, which is not normally observed in thermally cycled assemblies, cracks propagate
along the intermetallic layers due to the strong strain-rate hardening of the solder interconnections in drop tests. Owing
to strain-rate hardening, the stresses in the solder interconnections increase very rapidly in the corner regions of the interconnections
above the fracture strength of the ternary (Cu,Ni)6Sn5 phase leading to intermetallic fracture. In addition, because of strain-rate hardening, the recrystallization of the as-soldered
microstructure is hindered, and therefore the network of grain boundaries is not available in the bulk solder for cracks to
propagate, as occurs during thermal cycling. In the black pad failure mode, cracks nucleate and propagate in the porous NiSnP
layer between the columnar two-phase (Ni3P+Sn) layer and the (Cu,Ni)6Sn5 intermetallic layer. The fact that the Ni(P)|Au interconnections fail at the PWB side, even though higher stresses are generated
on the component side, underlines the brittle nature of the reaction layer. 相似文献
12.
Jung-Mo Kim Jae-Pil Jung Y. Norman Zhou Jong-Young Kim 《Journal of Electronic Materials》2008,37(3):324-330
Ultrasonic bonding of Si-dice to type FR-4 printed circuit boards (PCB) with Sn-3.5wt.%Ag solder at ambient temperature was
investigated. The under-bump metallization (UBM) on the Si-dice comprised Cu/Ni/Al from top to bottom with thicknesses of
0.4 μm, 0.4 μm, and 0.3 μm, respectively. The pads on the PCBs consisted of Au/Ni/Cu with thicknesses of 0.05/5/18 μm, sequentially from top to bottom. Solder was supplied as Sn-3.5wt.%Ag foil rolled to 100 μm thickness, and inserted in the joints. The ultrasonic bonding time was varied from 0.5 s to 3.0 s, and the ultrasonic power
was 1400 W. The experimental results showed that reliable joints could be produced between the Si-dice and the PCBs with Sn-3.5wt.%Ag
solder. The joint breaking force of “Si-die/solder/FR-4” increased with bonding times up to 2.5 s with a maximum value of
65 N. A bonding time of 3.0 s proved to be excessive, and resulted in cracks along the intermetallic compound between the
UBM and solder, which caused a decrease in the bond strength. The intermetallic compound produced by ultrasonic bonding between
the UBM and solder was confirmed to be (Cu, Ni)6Sn5.
An erratum to this article can be found at 相似文献
13.
Hyoung-Joon Kim Jong-Soo Cho Yong-Jin Park Jin Lee Kyung-Wook Paik 《Journal of Electronic Materials》2004,33(10):1210-1218
The main purposes for developing low-alloyed Au bonding wires were to increase wire stiffness and to control the wire loop
profile and heat-affected zone length. For these reasons, many alloying elements have been used for the various Au bonding
wires. Although there have been many studies reported on wire strengthening mechanisms by adding alloying elements, few studies
were performed on their effects on Au bonding wires and Al pad interfacial reactions. Palladium has been used as one of the
important alloying elements of Au bonding wires. In this study, Au-1wt.%Pd wire was used to make Au stud bumps on Al pads,
and effects of Pd on Au/Al interfacial reactions, at 150°C, 175°C, and 200°C for 0 to 1200 h thermal aging, were investigated.
Cross-sectional scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electron probe microanalysis
(EMPA) were performed to identify intermetallic compound (IMC) phases and Pd behavior at the Au/Al bonding interface. According
to experimental results, the dominant IMC was Au5Al2, and a Pd-rich layer was at the Au wire and Au-Al IMC. Moreover, Au-Al interfacial reactions were significantly affected
by the Pd-rich layer. Finally, bump shear tests were performed to investigate the effects of Pd-rich layers on Au wire bond
reliability, and there were three different failure modes. Cracks, accompanied with IMC growth, formed above a Pd-rich layer.
Furthermore, in longer aging times, fracture occurred along the crack, which propagated from the edges of a bonding interface
to the center along a Pd-rich layer. 相似文献
14.
The present work studies the microstructure and microstructural evolution of small volumes of nominally eutectic Au-Sn solder
on Cu. The study includes solder bumps 140–145 μm in diameter and 55–65 μm tall deposited on Cu-plated Si, and solder joints
60 μm in diameter and 25 μm in height that join Cu-plated ceramic and polymide substrates. The results show that the microstructure
is strongly affected by the addition of Cu from the substrate during reflow, which produces a thick intermetallic layer along
the interface. In the case of the joints, normal processing produces a coarse microstructure that includes only a few grains
between thick intermetallic coatings. Aging at high temperature causes a further monotonic increase in Cu content, which alters
the intermetallic structure at the interfaces and can lead to intermetallic bridging across the joint. Thermal fatigue tests
suggest that cyclic deformation breaks up the intermetallic structure, increasing the rate of Cu addition to the joint, but
refining the apparent grain size. 相似文献
15.
In order to investigate the fracture behavior of Sn–3.0Ag–0.5Cu solder bump, solder balls with the diameter of 0.76 mm were soldered on Cu pad in this study, then high speed impact test and static shear test of solder bumps were carried out to measure the joint strength of the soldering interface. The effect of isothermal aging on joint strength as well as fracture behavior of solder bumps was investigated, and the composition of the fracture surface was identified by means of EPMA. The results indicate that the fracture is inside the bulk solder in low speed shear test regardless of the aging effect, thus the maximum load reflects the solder strength rather than the interfacial strength. It is also found that under 1 m/s impact loading, the crack initiation position is changed from solder/Cu6Sn5 interface to Cu3Sn/Cu interface after long time isothermal aging, and the fracture occurs inside the bulk solder accompanying with intermetallic compound in both of the as-soldered and aged joints. The thickened multiple IMC layers during isothermal aging account for the degraded impact resistance, and the change of the solder matrix is another factor for reduced impact resistance owing to Sn residue on the fracture surface. 相似文献
16.
Interfacial reactions and mechanical properties of the ball-grid-array (BGA) solder joints using monolithic eutectic SnPB
and Cu-cored solder balls after reflow and solid-state annealing were investigated. The Cu cores of three different sizes
were used in the solder joints. The incorporation of a Cu core into the BGA solder joint effectively inhibits the (Au1−xNix)Sn4 regrouping and the (Cu1−x−yAuxNiy)6Sn5 phase is formed at the joint interface instead. Growth of the intermetallic compounds formed in the monolithic and Cu-cored
solder joints approximately obeys the parabolic law. In the Cu-cored solder joints, the larger the Cu core is, the slower
the intermetallic compounds grow. The size effect of the Cu core on the intermetallic compound growth results from the inconsistent
amount of the outer solder layer. Shear and tensile strengths of the Cu-cored solder joints decrease with increasing solid-state
annealing time, and do not have a noticeable relationship with the Cu-core size. Shear and tensile tests also show that the
mechanical strength of the Cu-cored solder joint is better than that of the monolithic solder joint. 相似文献
17.
S. Choi T. R. Bieler J. P. Lucas K. N. Subramanian 《Journal of Electronic Materials》1999,28(11):1209-1215
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 Cu6Sn5 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 Cu6Sn5 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. 相似文献
18.
The intermetallic compounds (IMCs) formed during the reflow and aging of Sn3Ag0.5Cu and Sn3Ag0.5Cu0.06Ni0.01Ge solder BGA
packages with Au/Ni surface finishes were investigated. After reflow, the thickness of (Cu, Ni, Au)6Sn5 interfacial IMCs in Sn3Ag0.5Cu0.06Ni0.01Ge was similar to that in the Sn3Ag0.5Cu specimen. The interiors of the solder balls
in both packages contained Ag3Sn precipitates and brick-shaped AuSn4 IMCs. After aging at 150°C, the growth thickness of the interfacial (Ni, Cu, Au)3Sn4 intermetallic layers and the consumption of the Ni surface-finished layer on Cu the pads in Sn3Ag0.5Cu0.06Ni0.01Ge solder
joints were both slightly less than those in Sn3Ag0.5Cu. In addition, a coarsening phenomenon for AuSn4 IMCs could be observed in the solder matrix of Sn3Ag0.5Cu, yet this phenomenon did not occur in the case of Sn3Ag0.5Cu0.06Ni0.01Ge.
Ball shear tests revealed that the reflowed Sn3Ag0.5Cu0.06Ni0.01Ge packages possessed bonding strengths similar to those of
the Sn3Ag0.5Cu. However, aging treatment caused the ball shear strength in the Sn3Ag0.5Cu packages to degrade more than that
in the Sn3Ag0.5Cu0.06Ni0.01Ge packages. 相似文献
19.
In this work we studied the initial microstructure and microstructural evolution of eutectic Au-Sn solder bumps on Cu/electroless
Ni/Au. The solder bumps were 150–160 m in diameter and 45–50 m tall, reflowed on Cu/electroless Ni/Au, and then aged at 200°C
for up to 365 days. In addition, Au-Ni-Sn-alloys were made and analyzed to help identify the phases that appear at the interface
during aging. The detailed interfacial microstructure was observed using a transmission electron microscope (TEM). The results
show that the introduction of Au from the substrate produces large islands of-phase in the bulk microstructure during reflow.
Two Au-Ni-Sn compounds are formed at the solder/substrate interface and grow slowly during aging. The maximum solubility of
Ni in the—phase was measured to be about 1 at.% at 200°C, while Ni in the-phase is more than 20 at.%. The electroless Ni layer
is made of several sublayers with slightly different compositions and microstructures. There is, in addition, an amorphous
interaction layer at the solder/electroless Ni interface. 相似文献
20.
The latest three-dimensional (3D) chip-stacking technology requires the repeated stacking of additional layers without remelting
the joints that have been formed at lower levels of the stack. This can be achieved by transient liquid-phase (TLP) bonding
whereby intermetallic joints can be formed at a lower temperature and withstand subsequent higher-temperature processes. In
order to develop a robust low-temperature Au/In TLP bonding process during which all solder is transformed into intermetallic
compounds, we studied the Au/In reaction at different temperatures. It was shown that the formation kinetics of intermetallic
compounds is diffusion controlled, and that the activation energy of Au/In reaction is temperature dependent, being 0.46 eV
and 0.23 eV for temperatures above and below 150°C, respectively. Moreover, a thin Ti layer between Au and In was found to
be an effective diffusion barrier at low temperature, while it did not inhibit joint formation at elevated temperatures during
flip-chip bonding. This allowed us to control the intermetallic formation during the distinct stages of the TLP bonding process.
In addition, a minimal indium thickness of 0.5 μm is required in order to enable TLP bonding. Finally, Au/In TLP joints of ∅40 μm to 60 μm were successfully fabricated at 180°C with very small solder volume (1 μm thickness). 相似文献