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1.
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
2.
High strain-rate drop impact tests were performed on ball grid array (BGA) packages with lead-free Sn-3.8Ag-0.7Cu solder (in
wt.%). Plated Ni and Cu under-bump metallurgies (UBMs) were used on the device side, and their drop test performances were
compared. Failure occurred at the device side, exhibiting brittle interfacial fracture. For Ni UBM, failure occurred along
the Ni/(Cu,Ni)6Sn5 interface, while the Cu UBM case showed failure along the interface between two intermetallics, Cu6Sn5/Cu3Sn. However, the damage across the package varied. For Cu UBM, only a few solder balls failed at the device edge, whereas
on Ni UBM, many more solder bumps failed. The difference in the failure behavior is due to the adhesion of the UBM and intermetallics
rather than the intermetallic thickness. The better adhesion of Cu UBM is due to a more active soldering reaction than Ni,
leading to stronger chemical bonding between intermetallics and UBM. In our reflow condition, the soldering reaction rate
was about 4 times faster on Cu UBM than on Ni UBM. 相似文献
3.
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
4.
The effects of various elements of substrate metallization, namely, Au, Ni, and P, on the solder/under-bump metallization
(UBM), (Al/Ni(V)/Cu) interfacial reactions in flip-chip packages during multiple reflow processes were systematically investigated.
It was found that Au and P had negligible effects on the liquid-solid interfacial reactions. However, Ni in the substrate
metallization greatly accelerated the interfacial reactions at chip side and degraded the thermal stability of the UBM through
formation of a (Cu,Ni)6Sn5 ternary compound at the solder/UBM interface. This phenomenon can be explained in terms of enhanced grain-boundary grooving
on (Cu,Ni)6Sn5 in the molten solder during the reflow process. This could eventually cause the rapid spalling of an intermetallic compound
(IMC) from the solder/UBM interface and early failure of the packages. Our results showed that formation of multicomponent
intermetallics, such as (Cu,Ni)6Sn5 or (Ni,Cu)3Sn4, at the solder/UBM interface is detrimental to the solder-joint reliability. 相似文献
5.
The intermetallic compound (IMC) evolution and the thermal–mechanical reliability of Sn–3.0Ag–0.5Cu (SAC305) solder joints were studied using air-to-air thermal shock testing of 100-μm-pitch peripheral-row flip chip assemblies. Flip chips assembled on organic substrates were subjected to air-to-air thermal shock testing between −55 °C and 125 °C, and the samples were removed at regular intervals for cross-sectioning and failure analysis. It was seen that on the die side, after 2000 cycles, all of the (Cu,Ni)3Sn4 had transferred to (Cu,Ni)6Sn5 due to strong cross-pad interaction between the chip-side Ni pad and substrate-side Cu pad, and thus, there was no premature solder cracking possibly due to the absence of dual IMC structure. On the substrate-side Cu interface, the Cu3Sn growth was hindered, and thus there was very little increase in Kirkendall voids in the Cu3Sn after 2000 cycles. Therefore, there was no premature brittle failure in the intermetallic. Failure analysis shows that the cracks in the outermost corner solder joint started to form after 2000 cycles near the chip-side pad, and the cracks propagated in the solder matrix around the IMC like a ring to create solder open. From the experimental data, crack propagation rate equation parameters and characteristic mean life were determined. 相似文献
6.
《Microelectronics Reliability》2015,55(8):1234-1240
The interfacial reactions and failure modes of the solder joints for flip-chip light emitting diode (LED) on electroless nickel/immersion gold (ENIG) and Cu with organic solderability preservatives (Cu-OSP) surface finishes were investigated in this study. The experimental results demonstrate that the interfacial reactions in the Au/Sn–Ag–Cu(SAC)/ENIG and Au/SAC/Cu systems are different but the failure mechanisms of the two types of solder joints are similar during the shear test. For the Au/SAC/ENIG system, the Au layer on the surface finish of the diodes dissolved into the molten solder and transformed into a continuous (Au, Ni)Sn4 IMC layer at the diode/solder interface during reflow and the interfacial IMC at the solder/ENIG interface is dendritic Ni3Sn4 IMC grains which are surrounded by (Au, Ni)Sn4. For the Au/SAC/Cu system, however, no IMC layers can be observed at the diode/solder interface. The interfacial IMC at the solder/Cu interface is (Cu, Au)6Sn5 and a Cu3Sn IMC layer at the (Cu, Au)6Sn5/Cu interface. Tiny (Au, Cu)Sn4 IMC grains distribute in the solder layer and surround the (Cu, Au)6Sn5 grains. For the two types of systems, the primary failure mode for the cathode is due to the broken of the Si-based insulation layer which led to a high residue stress and poor connection between the Si-based layer and the solder layer. Meanwhile, the failure of the solder joint for the anode is mainly because of the failure of the solder layer under the conductive via. The crack generally forms at this area and then propagated along the diode or the diode/solder interface. 相似文献
7.
Tensile properties and stress-controlled fatigue fracture behaviors of Cu/Sn-4Ag solder joints aged at 180°C for different
times were systematically investigated. It was found that the tensile strength of the solder joints decreased with increasing
aging time and that the fracture mode changed from ductile to brittle. The fatigue life of the solder joints also decreased
with increasing aging time. For most of the solder joints, fatigue cracks tended to initiate around the Cu/Cu6Sn5 interfaces due to the strain incompatibility and local strain concentration on a micro-scale, and they then propagated within
the solder proximately along the Cu/Cu6Sn5 interfaces. The samples aged for␣different times or tested under different stress amplitudes had similar fractography morphologies,
which consisted mainly of a propagation region, covered by solder, and a final fracture region. Based on the experimental
observations above, the corresponding interfacial fatigue failure mechanisms were discussed in terms of different influencing
factors. 相似文献
8.
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
9.
Kejun Zeng Mike Pierce Hiroshi Miyazaki Becky Holdford 《Journal of Electronic Materials》2012,41(2):253-261
To obtain the desired performance of Pb-free packages in mechanical tests, while the solder composition should be carefully
selected, the influence of metals dissolved from the soldering pad or under bump metallization (UBM) should also be taken
into account. Dissolved metals such as Cu can alter the intermetallic compound (IMC) formation, not only at the local interface
but also on the other side of the joint. The high rate of interfacial cracking of Sn-Ag-Cu solder joints on Ni/Au-plated
pads is attributed to the high stiffness of the solder and the dual IMC structure of (Cu,Ni)6Sn5 on Ni3Sn4 at the interface. Approaches to avoid this dual IMC structure at the interface are discussed. A rule for selecting the solder
alloy composition and the pad surface materials on both sides of the joints is proposed for ball grid array (BGA) packages. 相似文献
10.
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
11.
The Cu pillar is a thick underbump metallurgy (UBM) structure developed to alleviate current crowding in a flip-chip solder
joint under operating conditions. We present in this work an examination of the electromigration reliability and morphologies
of Cu pillar flip-chip solder joints formed by joining Ti/Cu/Ni UBM with largely elongated ∼62 μm Cu onto Cu substrate pad metallization using the Sn-3Ag-0.5Cu solder alloy. Three test conditions that controlled average
current densities in solder joints and ambient temperatures were considered: 10 kA/cm2 at 150°C, 10 kA/cm2 at 160°C, and 15 kA/cm2 at 125°C. Electromigration reliability of this particular solder joint turns out to be greatly enhanced compared to a conventional
solder joint with a thin-film-stack UBM. Cross-sectional examinations of solder joints upon failure indicate that cracks formed
in (Cu,Ni)6Sn5 or Cu6Sn5 intermetallic compounds (IMCs) near the cathode side of the solder joint. Moreover, the ~52-μm-thick Sn-Ag-Cu solder after long-term current stressing has turned into a combination of ~80% Cu-Ni-Sn IMC and ~20% Sn-rich
phases, which appeared in the form of large aggregates that in general were distributed on the cathode side of the solder
joint. 相似文献
12.
W. Fredriksz 《Journal of Electronic Materials》2005,34(9):1230-1241
Heat sink very-thin quad flat package no-leads (HVQFN) packages soldered with Sn-3.8Ag-0.7Cu on metallized laminate substrates
have been put to thermal aging. Temperatures from 140°C to 200°C for times up to 30 weeks were applied. The solder joint microstructure
develops intermetallic compound layers and voids within the solder. Due to this, the mechanical reliability of the HVQFN inner
lead solder joints is degraded. The intermetallic layers are of the type (Cu, Y)6Sn5, with Y=Ni, Au or Ni+Au, as well as Cu3Sn, and follow a power law with aging time: X=C·tn, where n=0.4 to 1.9 depending on temperature. The voids within the solder are attributed to Sn depletion of the solder in
favor of the growth of (Cu,Ni)6Sn5. They are more pronounced the less the solder volume is in proportion to the intermetallic diffusion area. The amount of
voids is quantified as a percentage of the residual solder. The time to reach the failure criterion of 50%, i.e., t50%, is related to the absolute temperature according to an Arrhenius equation with an activation energy Ea=0.95 eV. This equation is used for determination of the maximum allowable temperature at a certain required operating lifetime. 相似文献
13.
The effects of adding a small amount of Cu into eutectic PbSn solder on the interfacial reaction between the solder and the
Au/Ni/Cu metallization were studied. Solder balls of two different compositions, 37Pb-63Sn (wt.%) and 36.8Pb-62.7Sn-0.5Cu,
were used. The Au layer (1 ± 0.2 μm) and Ni layer (7 ± 1 μm) in the Au/Ni/Cu metallization were deposited by electroplating.
After reflow, the solder joints were aged at 160°C for times ranging from 0 h to 2,000 h. For solder joints without Cu added
(37Pb-63Sn), a thick layer of (Au1−xNix)Sn4 was deposited over the Ni3Sn4 layer after the aging. This thick layer of (Au1−xNix)Sn4 can severely weaken the solder joints. However, the addition of 0.5wt.%Cu (36.8Pb-62.7Sn-0.5Cu) completely inhibited the
deposition of the (Au1−xNix)Sn4 layer. Only a layer of (Cu1-p-qAupNiq)6Sn5 formed at the interface of the Cu-doped solder joints. Moreover, it was discovered that the formation of (Cu1-p-qAupNiq)6Sn5 significantly reduced the consumption rate of the Ni layer. This reduction in Ni consumption suggests that a thinner Ni layer
can be used in Cu-doped solder joints. Rationalizations for these effects are presented in this paper. 相似文献
14.
Ti/Ni(V)/Cu underbump metallization (UBM) is widely used in flip-chip technology today. The advantages of Ti/Ni(V)/Cu UBM
are a low reaction rate with solder and the lack of a magnetic effect during sputtering. Sn atoms diffuse into the Ni(V) layer
to form a Sn-rich phase, the so-called Sn-patch, during reflow and aging. In this study, the relationship between interfacial
reaction and mechanical properties of the solder joints with Ti/Ni(V)/Cu UBM was evaluated. Sn-3.0Ag-0.5Cu solder was reflowed
on sputtered Ti/Ni(V)/Cu UBM, and then the reflowed samples were aged at 125°C and 200°C, respectively. (Cu,Ni)6Sn5 was formed and grew gradually at the interface of the solder joints during aging at 125°C. The Sn-patch replaced the Ni(V)
layer, and (Ni,Cu)3Sn4 was thus formed between (Cu,Ni)6Sn5 and the Sn-patch at 200°C. The Sn-patch, composed of Ni and V2Sn3 after reflow, was transformed to V2Sn3 and amorphous Sn during aging. Shear and pull tests were applied to evaluate the solder joints under various heat treatments.
The shear force of the solder joints remained at 421 mN, yet the pull force decreased after aging at 125°C. Both the shear
and pull forces of the solder joints decreased during aging at 200°C. The effects of aging temperature on the mechanical properties
of solder joint were investigated and discussed. 相似文献
15.
The morphological and compositional evolutions of intermetallic compounds (IMCs) formed at three Pb-free solder/electroless
Ni-P interface were investigated with respect to the solder compositions and reflow times. The three Pb-free solder alloys
were Sn3.5Ag, Sn3.5Ag0.75Cu, and Sn3Ag6Bi2In (in wt.%). After reflow reaction, three distinctive layers, Ni3Sn4 (or Ni-Cu-Sn for Sn3.5Ag0.75Cu solder), NiSnP, and Ni3P, were formed on the electroless Ni-P layer in all the solder alloys. For the Sn3.5Ag0.75Cu solder, with increasing reflow
time, the interfacial intermetallics switched from (Cu,Ni)6Sn5 to (Cu,Ni)6Sn5+(Ni,Cu)3Sn4, and then to (Ni,Cu)3Sn4 IMCs. The degree of IMC spalling for the Sn3.5Ag0.75Cu solder joint was more than that of other solders. In the cases of
the Sn3.5Ag and Sn3Ag6Bi2In solder joints, the growth rate of the Ni3P layer was similar because these two type solder joints had a similar interfacial reaction. On the other hand, for the Sn3.5Ag0.75Cu
solder, the thickness of the Ni3P and Ni-Sn-P layers depended on the degree of IMC spalling. Also, the shear strength showed various characteristics depending
on the solder alloys and reflow times. The fractures mainly occurred at the interfaces of Ni3Sn4/Ni-Sn-P and solder/Ni3Sn4. 相似文献
16.
G. Ghosh 《Journal of Electronic Materials》2004,33(3):229-240
The reactive interdiffusion between a Sn-3.0wt.%Ag-0.7wt.%Cu solder and thin-film Ti/Ni/Ag metallizations on two semiconductor
devices, a diode and a metal-oxide-semiconductor field-effect transistor (MOSFET), and a Au-layer on the substrates are studied.
Comprehensive microanalytical techniques, scanning electron microscopy, transmission electron microscopy (TEM), and analytical
electron microscopy (AEM) are employed to identify the interdiffusion processes during fabrication and service of the devices.
During the reflow process of both diode and MOSFET devices, (1) the Ag layer dissolves in the liquid solder; (2) two intermetallics,
(Ni,Cu)3Sn4 and (Cu,Ni)6Sn5, form near the back metal/solder interface; and (3) the Au metallization in the substrate side dissolves in the liquid solder,
resulting in precipitation of the (Au,Ni,Cu)Sn4 intermetallic during solidification. During solid-state aging of both diode and MOSFET solder joints at 125°C and 200°C,
the following atomic transport processes occur: (1) interdiffusion of Cu, Ni, and Sn, leading to the growth of a (Ni,Cu)3Sn4 layer until the Ni layer is completely consumed; (2) interdiffusion of Au, Cu, Ni, and Sn through the (Ni,Cu)3Sn4 layer and unconsumed Ni layer to the Ti layer to form a solid solution; and (3) further interdiffusion of Au, Cu, Ni, and
Sn through the (Ni,Cu)3Sn4 layer to from an (Au,Ti,Ni,Cu)Sn4 layer. The growth of the latter layer continues until the entire Ti layer is consumed. 相似文献
17.
Yoon Jeong-Won Kim Sang-Won Koo Ja-Myeong Kim Dae-Gon Jung Seung-Boo 《Journal of Electronic Materials》2004,33(10):1190-1199
The interfacial reactions between two Sn-Cu (Sn-0.7Cu and Sn-3Cu, wt.%) ball-grid-array (BGA) solders and the Au/Ni/Cu substrate
by solid-state isothermal aging were examined at temperatures between 70°C and 170°C for 0 to 100 days. For the Sn-0.7Cu solder,
a (Cu,Ni)6Sn5 layer was observed in the samples aged at 70–150°C. After isothermal aging at 170°C for 50 days, the solder/Ni interface
exhibited a duplex structure of (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4. For the Sn-3Cu solder, only the (Cu,Ni)6Sn5 layer was formed in all aged samples. Compared to these two Sn-Cu solders, the Cu content in the (Cu,Ni)6Sn5 layer formed at the interface increased with the Cu concentration in the Sn-xCu solders. And, the shear strength was measured
to evaluate the effect of the interfacial reactions on the mechanical reliability as a function of aging conditions. The shear
strength significantly decreased after aging for 1 day and then remained nearly unchanged by further prolonged aging. In all
the samples, the fracture always occurred in the bulk solder. Also, we studied the electrical property of Cu/Sn-3Cu/Cu BGA
packages with the number of reflows. The electrical resistivity increased with the number of reflows because of an increase
of intermetallic compound (IMC) thickness. 相似文献
18.
Effects of the gold thickness of the surface finish on the interfacial reactions in flip-chip solder joints 总被引:1,自引:0,他引:1
Y. L. Lin W. C. Luo Y. H. Lin C. E. Ho C. R. Kao 《Journal of Electronic Materials》2004,33(10):1092-1097
The effects of Au thickness on the flip-chip solder joints with Cu/Ni/Al underbump metallurgy (UBM) on one end and the Au/Ni
surface finish on another was studied. Two different thicknesses, 0.1 μm and 0.65 μm, were used for the surface finish. After
assembly, the joints were subjected to thermal aging at 150°C. The difference in Au thickness had a strong effect on the consumption
rate of the Ni layer in the UBM as well as on the failure mode of the solder joints. When the Au layer was thin (0.1 μm),
the dissolved Cu from the Cu/Ni UBM was able to inhibit the formation of AuSn4. When the Au layer was thick (0.65 μm), the dissolved Cu was not able to inhibit the formation of AuSn4. These AuSn4 enhanced the Ni consumption rate of the UBM. The presence of a large amount of AuSn4 inside the solder also weakened the solder because of the Au embrittlement effect. In view of these observations, the gold
thickness on the Au/Ni surface finish must be kept to the minimum controlled in order to prolong the service life of flip-chip
packages. 相似文献
19.
Cu6Sn5 and Cu3Sn are common intermetallic compounds (IMCs) found in Sn–Ag–Cu (SAC) lead-free solder joints with OSP pad finish. People typically attributed the brittle failure to excessive growth of IMCs at the interface between the solder joint and the copper pad. However, the respective role of Cu6Sn5 and Cu3Sn played in the interfacial fracture still remains unclear. In the present study, various amounts of Ni were doped in the Sn–Cu based solder. The different effects of Ni concentration on the growth rate of (Cu, Ni)6Sn5/Cu6Sn5 and Cu3Sn were characterized and compared. The results of characterization were used to evaluate different growth rates of (Cu, Ni)6Sn5 and Cu3Sn under thermal aging. The thicknesses of (Cu, Ni)6Sn5/Cu6Sn5 and Cu3Sn after different thermal aging periods were measured. High speed ball pull/shear tests were also performed. The correlation between interfacial fracture strength and IMC layer thicknesses was established. 相似文献