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1.
The interfacial microstructure of electroless Ni-P/Sn-3.5Ag solder joints was investigated after reflow and high-temperature
solid-state aging to understand its interdependent growth mechanism and related kinetics of intermetallic compounds (IMCs)
at the interface. The reflow and aging results showed that mainly three IMC layers, Ni3Sn4, Ni2SnP, and Ni3P, formed during the soldering reaction. It was found that the Ni3Sn4 and Ni3P layers grow predominantly as long as the electroless Ni-P layer is present; however, once the Ni-P layer is fully consumed,
the Ni2SnP layer grows rapidly at the expense of the Ni3P layer. A transition in the Ni3Sn4 morphology from needle and chunky shape to scallop shape was observed after the solid-state aging of reflowed samples. The
kinetics data obtained from the growth of compound layers in the aged samples revealed that initially the growth of the Ni2SnP layer is controlled by diffusion, and subsequently by the rate of reaction after the Ni-P metallization is fully consumed.
It was found that complete transformation of the electroless Ni-P layer into a Ni3P layer results in the rapid growth of the Ni2SnP layer due to the dominating reaction of Sn with Ni3P. The apparent activation energies for the growth of Ni3Sn4, Ni2SnP, and Ni3P compound layers were found to be 98.9 kJ/mol, 42.2 kJ/mol, and 94.3 kJ/mol, respectively. 相似文献
2.
During the reflow process of Sn-3.5Ag solder ball grid array (BGA) packages with Ag/Cu and Au/Ni/Cu pads, Ag and Au thin films
dissolve rapidly into the liquid solder, and the Cu and Ni layers react with the Sn-3.5Ag solder to form Cu6Sn5 and Ni3Sn4 intermetallic compounds at the solder/pad interfaces, respectively. The Cu6Sn5 intermetallic compounds also appear as clusters in the solder matrix of Ag surface-finished packages accompanied by Ag3Sn dispersions. In the solder matrix of Au/Ni surface-finished specimens, Ag3Sn and AuSn4 intermetallics can be observed, and their coarsening coincides progressively with the aging process. The interfacial Cu6Sn5 and Ni3Sn4 intermetallic layers grow by a diffusion-controlled mechanism after aging at 100 and 150°C. Ball shear strengths of the reflowed
Sn-3.5Ag packages with both surface finishes are similar, displaying the same degradation tendencies as a result of the aging
effect. 相似文献
3.
Han-Byul Kang Jee-Hwan Bae Jae-Wook Lee Min-Ho Park Jeong-Won Yoon Seung-Boo Jung Cheol-Woong Yang 《Journal of Electronic Materials》2008,37(1):84-89
The interfacial reaction between a eutectic Sn-3.5wt.%Ag solder and an electroless nickel–immersion gold-plated Cu substrate
during reflow was examined by transmission electron microscopy (TEM). During the initial reflowing, the amorphous, electroless
Ni (P)-plated layer crystallized into two P-rich Ni layers: a Ni12P5 + Ni3P mixed upper layer and a Ni3P lower layer. No ternary Ni-Sn-P layer was observed in the initial stage. After subsequent reflow for 60 s, a ternary Ni2SnP layer (containing a small amount of the Ni3P phase) was formed between the Ni3Sn4 and P-rich Ni layers (Ni3P + Ni12P5 + Ni). 相似文献
4.
Effect of Interfacial Reaction on the Tensile Strength of Sn-3.5Ag/Ni-P and Sn-37Pb/Ni-P Solder Joints 总被引:2,自引:0,他引:2
This work investigates the effect of interfacial reaction on the mechanical strength of two types of solder joints, Sn-3.5Ag/Ni-P
and Sn-37Pb/Ni-P. The tensile strength and fracture behavior of the joints under different thermal aging conditions have been
studied. It is observed that the tensile strength decreases with increasing aging temperature and duration. Associated with
the tensile strength decrease is the transition of failure modes from within the bulk solder in the as-soldered condition
toward failures at the interface between the solder and the intermetallic compounds (IMCs). For the same aging treatment,
the strength of the Sn-3.5Ag/Ni-P joint degrades faster than that of Sn-37Pb/Ni-P. The difference between the two types of
joints can be explained by the difference in their interfacial reaction and growth kinetics. An empirical relation is established
between the solder joint strength and the Ni3Sn4 intermetallic compound thickness. 相似文献
5.
Extensive microstructural and kinetic studies on the formation and growth of the intermetallics of Sn-rich solder/Cu couples
have been reported. However, experimental data on the interdiffusion mechanisms during soldering reactions are limited and
in conflict. The interdiffusion processes for soldering of Sn-3.5Ag alloy/Cu couples were investigated by using the Cr-evaporated
surface as a reference line. At the beginning of soldering, Cu was observed to outdiffuse to the molten Sn−3.5Ag alloy until
saturation, and the Sn−Ag solder dissolved with Cu collapsed below the reference line. As a result, the scallop-shaped Cu6Sn5 intermetallic compound was formed at the newly-formed Sn−Ag−Cu solder/Cu interface below the original Cu surface. When the
soldered joint was reflowed at the lower temperature to suppress the Cu dissolution, the Cu6Sn5/Cu interface moved into the Cu substrate. Therefore, Sn is the dominant diffusing species for the intermetallic formation
during the soldering process, although the extensive Cu dissolution occurs at the early stage of soldering. 相似文献
6.
Hai-Tao Ma Jie Wang Lin Qu Ning Zhao A. Kunwar 《Journal of Electronic Materials》2013,42(8):2686-2695
A rapidly solidified Sn-3.5Ag eutectic alloy produced by the melt-spinning technique was used as a sample in this research to investigate the microstructure, thermal properties, solder wettability, and inhibitory effect of Ag3Sn on Cu6Sn5 intermetallic compound (IMC). In addition, an as-cast Sn-3.5Ag solder was prepared as a reference. Rapidly solidified and as-cast Sn-3.5Ag alloys of the same size were soldered at 250°C for 1 s to observe their instant melting characteristics and for 3 s with different cooling methods to study the inhibitory effect of Ag3Sn on Cu6Sn5 IMC. Experimental techniques such as scanning electron microscopy, differential scanning calorimetry, and energy-dispersive spectrometry were used to observe and analyze the results of the study. It was found that rapidly solidified Sn-3.5Ag solder has more uniform microstructure, better wettability, and higher melting rate as compared with the as-cast material; Ag3Sn nanoparticles that formed in the rapidly solidified Sn-3.5Ag solder inhibited the growth of Cu6Sn5 IMC during aging significantly much strongly than in the as-cast material because their number in the rapidly solidified Sn-3.5Ag solder was greater than in the as-cast material with the same soldering process before aging. Among the various alternative lead-free solders, this study focused on comparison between rapidly solidified and as-cast solder alloys, with the former being observed to have better properties. 相似文献
7.
8.
Chien-Sheng Huang Jenq-Gong Duh Yen-Ming Chen 《Journal of Electronic Materials》2003,32(12):1509-1514
Several international legislations recently banned the use of Pb because of environmental concerns. The eutectic Sn-Ag solder
is one of the promising candidates to replace the conventional Sn-Pb solder primarily because of its excellent mechanical
properties. In this study, interfacial reaction of the eutectic Sn-Ag and Sn-Pb solders with Ni/Cu under-bump metallization
(UBM) was investigated with a joint assembly of solder/Ni/Cu/Ti/Si3N4/Si multilayer structures. After reflows, only one (Ni,Cu)3Sn4 intermetallic compound (IMC) with faceted and particlelike grain feature was found between the solder and Ni. The thickness
and grain size of the IMC increased with reflow times. Another (Cu,Ni)6Sn5 IMC with a rod-type grain formed on (Ni,Cu)3Sn4 in the interface between the Sn-Pb solder and the Ni/Cu UBM after more than three reflow times. The thickness of the (Ni,Cu)3Sn4 layer formed in the Sn-Pb system remained almost identical despite the numbers of reflow; however, the amounts of (Cu,Ni)6Sn5 IMC increased with reflow times. Correlations between the IMC morphologies, Cu diffusion behavior, and IMC transformation
in these two solder systems will be investigated with respect to the microstructural evolution between the solders and the
Ni/Cu UBM. The morphologies and grain-size distributions of the (Ni,Cu)3Sn4 IMC formed in the initial stage of reflow are crucial for the subsequent phase transformation of the other IMC. 相似文献
9.
In this work, the melting characteristics and interfacial reactions of Sn-ball/Sn-3.0Ag-0.5Cu-paste/Cu (Sn/SAC305-paste/Cu) structure joints were studied using differential scanning calorimetry, in order to gain a deeper and broader understanding of the interfacial behavior and metallurgical combination among the substrate (under-bump metallization), solder ball and solder paste in a board-level ball grid array (BGA) assembly process, which is often seen as a mixed assembly using solder balls and solder pastes. Results show that at the SAC305 melting temperature of 217°C, neither the SAC305-paste nor the Sn-ball coalesce, while an interfacial reaction occurs between the SAC305-paste and Cu. A slight increase in reflow temperature (from 217°C to 218°C) results in the coalescence of the SAC305-paste with the Sn-ball. The Sn-ball exhibits premelting behavior at reflow temperatures below its melting temperature, and the premelting direction is from the bottom to the top of the Sn-ball. Remarkably, at 227°C, which is nearly 5°C lower than the melting point of pure Sn, the Sn-ball melts completely, resulting from two eutectic reactions, i.e., the reaction between Sn and Cu and that between Sn and Ag. Furthermore, a large amount of bulk Cu6Sn5 phase forms in the solder due to the quick dissolution of Cu substrate when the reflow temperature is increased to 245°C. In addition, the growth of the interfacial Cu6Sn5 layer at the SAC305-paste/Cu interface is controlled mainly by grain boundary diffusion, while the growth of the interfacial Cu3Sn layer is controlled mainly by bulk diffusion. 相似文献
10.
Hitoshi Sakurai Alongheng Baated Kiju Lee Seongjun Kim Keun-Soo Kim Youichi Kukimoto Seishi Kumamoto Katsuaki Suganuma 《Journal of Electronic Materials》2010,39(12):2598-2604
The microstructure resulting from Sn-3.5Ag soldering on an electroless Ni-P/Au pad using flux containing Zn(II) stearate was
investigated. The content of zinc compound in the flux was 0 wt.% (Z-0), 20 wt.% (Z-20) or 50 wt.% (Z-50). A study of the
interfacial microstructure revealed that both Z-20 and Z-50 fluxes yielded a thinner P-rich layer at the interface than did
the Z-0 flux. In addition, compared with the bulky Ni–Sn intermetallics of the Z-0 joint interface, refined interfacial intermetallic
compounds (IMCs) were observed when using Zn-containing fluxes, Z-20 and Z-50. Based on qualitative analyses of both Z-20
and Z-50 joint interfaces, it was presumed that their intermetallic layers would consist of Ni, Zn, and Sn. Additionally,
the Ni content in the IMC layer of the Z-50 joint was lower than that of the Z-20 joint. Electron probe microanalysis (EPMA)
of the initial Z-50 joint interface revealed Zn in the interfacial reaction layer, suggesting that Zn participated in the
reaction between solder and the surface finish at an early stage of soldering. Consequently, the supply of Zn from the flux
diminished Ni diffusion into the molten solder during heating. This effect may have caused a thin P-rich layer to form at
the joint interface. 相似文献
11.
Electroless Ni-P layers with three different P contents (6.1 wt.%, 8.8 wt.%, and 12.3wt.%) were deposited on copper (Cu) substrates.
Multilayered samples of Sn-3.5Ag/Ni-P/Cu stack were prepared and subjected to multiple reflows at 250°C. A tensile test was
performed to investigate the effect of P content on the solder joint strength. The low P samples exhibited the highest joint
strength after multiple reflows, while the strength of medium and high P samples decreased more rapidly. From interfacial
analysis, the Ni3Sn4 intermetallic compound (IMC) formed at the interface of low P sample was found to be more stable, while the one of medium
and high P samples spalled into the molten solder. The IMC spallation sped up the consumption of electroless Ni-P, leading
to the large formation of Cu-Sn IMCs. Fractographic and microstructural analyses showed that the degradation in solder joint
strength was due to the formation of layers of voids and growth of Cu-Sn IMCs between the solder and the Cu substrate. 相似文献
12.
13.
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
14.
The intermetallic compounds formed during the reflow and aging of Sn-20In-2.8Ag ball-grid-array (BGA) packages are investigated.
After reflow, a large number of cubic-shaped AuIn2 intermetallics accompanied by Ag2In precipitates appear in the solder matrix, while a Ni(Sn0.72Ni0.28)2 intermetallic layer is formed at the solder/pad interface. With further aging at 100°C, many voids can be observed in the
solder matrix and at the solder/pad interface. The continuous distribution of voids at the interface of specimens after prolonged
aging at 100°C causes their bonding strength to decrease from 5.03 N (as reflowed) to about 3.50 N. Aging at 150°C induces
many column-shaped (Cu0.74Ni0.26)6(Sn0.92In0.08)5 intermetallic compounds to grow rapidly and expand from the solder/pad interface into the solder matrix. The high microhardness
of these intermetallic columns causes the bonding strength of the Sn-20In-2.8Ag BGA solder joints to increase to 5.68 N after
aging at 150°C for 500 h. 相似文献
15.
It was reported in previous studies that the addition of Bi could improve the wettability and reduce the melting temperature
of Sn-Ag solders. This work investigates the effect of Bi on the interfacial reaction between Sn-Ag-xBi solders and the Cu substrate reflowed at 250°C for different times and thermally aged at 150°C for different durations.
Five types of Sn-Ag-based solders, Sn-3.7Ag-xBi (x = 0 wt.% to 4 wt.%), were used in this study. The microstructure of the interfacial Cu-Sn intermetallic compound (IMC) layers
between the solders and the Cu substrate was studied, and the thickness of the Cu-Sn IMCs in different solder/Cu systems has
been measured. It was found that the thickness of the Cu-Sn IMC layer decreased with increasing amount of Bi in both the reflow
and thermally aged condition. The effect of Bi addition on the interfacial reaction between the solder and the Cu substrate
was discussed based on the experimental results. 相似文献
16.
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
17.
B. A. Cook I. E. Anderson J. L. Harringa R. L. Terpstra J. C. Foley Ö. Ünal F. C. Laabs 《Journal of Electronic Materials》2001,30(9):1214-1221
The shear deformation behavior of two lead-free solder compositions, Sn-3.5Ag (wt.%) and Sn-3.6Ag-1.0Cu (wt.%), both on copper
substrates, was studied using an asymmetric four point bend technique. Four test joints were obtained from one master specimen
of each composition, and each joint was subject to progressive loading, up to the maximum shear strength of the joint. One
unstressed bar from each composition was retained as a reference. Each sample was metallo-graphically plished and lightly
etched, and examined in a field emission scanning electron microscope (SEM) before shearing. Sheared joints were then re-examined
in the SEM with no additional surface treatment. Compared with the traditional ring and plug method, the asymmetric four-point
bend (AFPB) technique subjects the joints to a condition of pure shear, while providing an opportunity for unambiguous observation
of microstructural features before and after shearing, without an intervening mechanical sectioning step. Shear banding in
the Sn-rich matrix and crack nucleation in the vicinity of the intermetallic interface were observed at low displacements
in the binary alloy. Evidence of non-homogeneous plastic flow in the matrix was seen at higher shear loading. No evidence
of brittle fracture was observed in the Sn-3.6Ag-1.0 Cu alloy, with elastic deformation at low stress levels giving rise to
plastic deformation at higher loading values. Results show that the AFPB technique is a viable approach to the study of shear
loading on solder joints. 相似文献
18.
The effect of substrate surface roughness on the fracture toughness of Cu/96.5Sn-3.5Ag solder joints
The effects of substrate surface roughness, joint thickness, time above liquidus, and testing temperature on the chevron notch
fracture toughness of Cu/96.5Sn-3.5Ag solder joints are investigated. Of these four variables,only the surface roughness of the copper surfaces to be soldered has a significant effect. A minimum fracture toughness is obtained
when the average surface roughness, Ra, is between 0.2 and 1.0 μm. This encompasses the surface roughnesses produced by many cold forming operations. Decreasing
the roughness to 0.04 μm increases the fracture toughness from 4.7 to 11.0 MPa√m, an improvement of 135%. Increasing the roughness
to 2.0 μm increases the fracture toughness to 8.8 MPa√m, an improvement of 80%. We attribute these effects to the increased
growth stresses that develop in the brittle intermetallic layer when the size scale of individual intermetallic particles
is comparable to the size of the roughness features of the substrate. Two models that describe how these growth stresses might
develop are provided. 相似文献
19.
Ja-Myeong Koo Bui Quoc Vu Yu-Na Kim Jong-Bum Lee Jong-Woong Kim Dae-Up Kim Jeong-Hoon Moon Seung-Boo Jung 《Journal of Electronic Materials》2008,37(1):118-124
The microstructural evolution, die shear strength, and electrical resistivity of Cu/Sn-3.5Ag (wt.%)/Cu ball grid array (BGA)
solder joints were investigated after 1 to 10 reflows using scanning electron microscopy (SEM), transmission electron microscopy
(TEM), electron probe microanalysis (EPMA), bonding testing, and a four-point probe station. A Cu6Sn5 intermetallic compound (IMC) was formed at both the upper and lower interfaces after one reflow. The IMC thickness increased
at the lower interface with increasing reflow number, whereas the IMC morphology and thickness remained virtually unchanged
at the upper interface, irrespective of the reflow number. The amount of Cu6Sn5 IMC contained in the solder ball increased with increasing reflow number. These microstructural evolutions with increasing
reflow number strongly affected the mechanical and electrical properties of the solder joint. 相似文献
20.
The 0.2Co + 0.1Ni dual additives were used to dope a Sn-3.5Ag solder matrix to modify the alloy microstructure and the solder
joint on an organic solderability preservative (OSP) Cu pad. The refined microstructure of the Sn-3.5Ag-0.2Co-0.1Ni solder
alloy or the reduced β-Sn size was attributed to the depressed undercooling achieved by the Co-Ni addition. After soldering
on the OSP Cu pad, a large Ag3Sn plate was formed at the Sn-3.5Ag/OSP solder joint, whereas it was absent at the Sn-3.5Ag-0.2Co-0.1Ni/OSP solder joints.
With isothermal aging at 150°C, large Ag3Sn plates formed at the Sn-3.5Ag/OSP solder joint were still observed. A coarsened and dispersed Ag3Sn phase was found in the solder joints with Co-Ni additions as well. Compared to Cu6Sn5, the (Co,Ni)Sn2 intermetallic compound showed much lower microhardness values. However, (Co,Ni)Sn2 hardness was comparable to that of the Ag3Sn phase. Pull strength testing of Sn-3.5Ag-0.2Co-0.1Ni/OSP revealed slightly lower values than for Sn-3.5Ag/OSP during aging.
Such results are thought be due to the phase transformation of (Co,Ni)Sn2 to (Cu,Co,Ni)6Sn5. 相似文献