Growth mechanism of intermetallic compounds and damping properties of Sn–Ag–Cu-1 wt% nano-ZrO2 composite solders

Nano-sized, nonreacting, noncoarsening ZrO₂ ceramic particles reinforced Sn–Ag–Cu composite solders were prepared by mechanically dispersing nano-particles into Sn–Ag–Cu solder and investigated their microstructure, kinetic analysis and mechanical properties i.e., shear strength, hardness and high temperature/mechanical damping characteristics. From microstructures evaluation, it was clear that composite solders containing ZrO₂ ceramic nano-particles significantly impact on the formation of intermetallic compounds (IMCs) at their interfaces as well as refined microstructure in the solder ball regions. The growth behavior of IMCs layer at the interfaces in composite solders was lower than that of plain Sn–Ag–Cu solders. Moreover, after long time aging, some microcracks were clearly observed at the interface due to the formation of excessive IMC layer and softening nature of plain Sn–Ag–Cu solder joints.     

Microstructure, thermal analysis and hardness of a Sn–Ag–Cu–1 wt% nano-TiO2 composite solder on flexible ball grid array substrates

Sn-Ag-Cu composite solders reinforced with nano-sized, nonreacting, noncoarsening 1 wt% TiO₂ particles were prepared by mechanically dispersing TiO₂ nano-particles into Sn-Ag-Cu solder powder and the interfacial morphology of the solder and flexible BGA substrates were characterized metallographically. At their interfaces, different types of scallop-shaped intermetallic compound layers such as Cu₆Sn₅ for a Ag metallized Cu pad and Sn-Cu-Ni for a Au/Ni and Ni metallized Cu pad, were found in plain Sn-Ag-Cu solder joints and solder joints containing 1 wt% TiO₂ nano-particles. In addition, the intermetallic compound layer thicknesses increased substantially with the number of reflow cycles. In the solder ball region, Ag₃Sn, Cu₆Sn₅ and AuSn₄ IMC particles were found to be uniformly distributed in the β-Sn matrix. However, after the addition of TiO₂ nano-particles, Ag₃Sn, AuSn₄ and Cu₆Sn₅ IMC particles appeared with a fine microstructure and retarded the growth rate of IMC layers at their interfaces. The Sn-Ag-Cu solder joints containing 1 wt% TiO₂ nano-particles consistently displayed a higher hardness than that of the plain Sn-Ag-Cu solder joints as a function of the number of reflow cycles due to the well-controlled fine microstructure and homogeneous distribution of TiO₂ nano-particles which gave a second phase dispersion strengthening mechanism.     

Effect of additions of ZrO2 nano-particles on the microstructure and shear strength of Sn-Ag-Cu solder on Au/Ni metallized Cu pads

Nano-sized, nonreacting, noncoarsening ZrO₂ particles reinforced Sn-3.0 wt%Ag-0.5 wt%Cu composite solders were prepared by mechanically dispersing ZrO₂ nano-particles into Sn-Ag-Cu solder. The interfacial morphology of unreinforced Sn-Ag-Cu solder and solder joints containing ZrO₂ nano-particles with Au/Ni metallized Cu pads on ball grid array (BGA) substrates and the distribution of reinforcing particles were characterized metallographically. At their interfaces, a Sn-Ni-Cu intermetallic compound (IMC) layer was found in both unreinforced Sn-Ag-Cu and Sn-Ag-Cu solder joints containing ZrO₂ nano-particles and the IMC layer thickness increased with the number of reflow cycles. In the solder ball region, AuSn₄, Ag₃Sn, Cu₆Sn₅ IMC particles and ZrO₂ nano-particles were found to be uniformly distributed in the β-Sn matrix of Sn-Ag-Cu solder joints containing ZrO₂ nano-particles, which resulted in an increase in the shear strength, due to a second phase dispersion strengthening mechanism. The fracture surface of unreinforced Sn-Ag-Cu solder joints exhibited a brittle fracture mode with a smooth surface while Sn-Ag-Cu solder joints containing ZrO₂ nano-particles ductile failure characteristics with rough dimpled surfaces.     

Effect of displacement rate on ball shear properties for Sn–37Pb and Sn–3.5Ag BGA solder joints during isothermal aging

The interfacial reactions and ball shear properties of ball grid array (BGA) solder joints aged at 170 °C for up to 21 days were investigated with different displacement rates. Two different kinds of solders, Sn–37Pb and Sn–3.5Ag (all wt.%), and an electroplated Ni/Au BGA substrate were employed in this work. A continuous Ni₃Sn₄ intermetallic compound (IMC) layer was formed at the interfaces between both the Sn–37Pb and Sn–3.5Ag solders and the substrate during reflow. After aging, two different reaction layers, consisting of (Au_xNi_1−x)Sn₄ IMC and Pb-rich phase, were additionally observed between the Sn–37Pb solder and the Ni₃Sn₄ IMC layer. The thicknesses of these interfacial reaction layers increased with increasing aging time. After reflow, all the fractures occurred inside the bulk solder. The fracture location of the Sn–37Pb solder joints was shifted toward the solder/Ni interface with increasing aging time and displacement rate, whereas the fracture of the Sn–3.5Ag solder joints mainly occurred inside the bulk solder, irrespective of the aging time and displacement rate. Consequently, the shear properties of the Sn–37Pb solder joints significantly decreased with increasing aging time, whereas those of the Sn–3.5Ag solder joints slightly decreased. The tendency toward brittle fracture of the Sn–37Pb solder joints was intensified with increasing displacement rate. The shear properties of the ductile solder joints increased with increasing displacement rate, while the displacement until fracture, deformation energy and displacement rate sensitivity of the brittle solder joints significantly decreased with increasing displacement rate.     

Effects of fourth alloying additive on microstructures and tensile properties of Sn–Ag–Cu alloy and joints with Cu

The effects of the fourth elements, i.e., Fe, Ni, Co, Mn and Ti, on microstructural features, undercooling characteristics, and monotonic tensile properties of Sn–3 wt.%Ag–0.5 wt.%Cu lead-free solder were investigated. All quaternary alloys basically form third intermetallic compounds in addition to fine Ag₃Sn and Cu₆Sn₅ and exhibit improved solder structure. The precipitates of Sn–3Ag–0.5Cu (–0.1 wt.%X; X=Ni, Ti and Mn) alloy are very fine comparing with the other alloys. The effective elements for suppressing undercooling in solidification are Ti, Mn, Co and Ni. All quaternary bulk alloys exhibit similar or slightly larger tensile strengths; especially Mn and Ni can improve elongation without degrading strength. The interfacial phases of Sn–3Ag–0.5Cu (–0.1 wt.%X; X=Fe, Mn and Ti)/Cu joints are typical Cu₆Sn₅ scallops. Sn–3Ag–0.5Cu (–0.1 wt.%X; X=Ni and Co)/Cu joints form very fine Sn–Cu–Ni and Sn–Cu–Co scallops at interface. The Cu/Sn–3Ag–0.5Cu–0.1Ni/Cu joint exhibits improved tensile strength prior to thermal aging at 125 and 150 °C. The fracture surface of Cu/Sn–3Ag–0.5Cu/Cu joint exhibits mixture of ductile and brittle fractures, while Cu/Sn–3Ag–0.5Cu (–0.1X; X=Ni and Co)/Cu joints exhibit only brittle fracture at interface. The Sn–3Ag–0.5Cu–0.1Ni alloy is more reliable solder alloy with improved properties for all tests in the present work.     

Effect of nano Al2O3 particles doping on electromigration and mechanical properties of Sn–58Bi solder joints

In the present study, the effect of Al₂O₃ nanoparticles on performances of Sn–58Bi solder were investigated in aspects of electro-migratio, shear strength and microhardness. The experimental results show that the Al₂O₃ nanoparticles significantly improved microstructure and mechanical performances of solder joints. With the addition of 0.5 wt% Al₂O₃, the intermetallic compounds (IMC) reduced from 2.5 μm to 1.27 μm after 288 aging hours at 85 °C. Furthermore, after electromigration test under a current density of 5 × 10³ A/cm² at 85 °C, Bi-rich layers formed at the anode side of both Al₂O₃ doped and plain solder. Moreover, the addition of Al₂O₃ nanoparticles reduced the mean thickness of Bi-rich layer. In addition, the growth rate of the IMC layer of Al₂O₃ doped solder decreased by 8% compared with the plain solder. Besides, the Al₂O₃ doped solder exhibited better performance than plain solder in microhardness after different aging times. While, the addition of Al₂O₃ significantly impeded the degradation of the shear strength of solder joint after aging for 48 and 288 h. Furthermore, it was worth noting that the fracture surface of doped solder showed a typical rough and ductile structure. However, plain solder exhibited a relatively smooth and fragile surface.     

Effect of Ag micro-particles content on the mechanical strength of the interface formed between Sn–Zn binary solder and Au/Ni/Cu bond pads

In this study, addition of Ag micro-particles with a content in the range between 0 and 4 wt.% to a Sn–Zn eutectic solder, were examined in order to understand the effect of Ag additions on the microstructural and mechanical properties as well as the thermal behavior of the composite solder formed. The shear strengths and the interfacial reactions of Sn–Zn micro-composite eutectic solders with Au/Ni/Cu ball grid array (BGA) pad metallizations were systematically investigated. Three distinct intermetallic compound (IMC) layers were formed at the solder interface of the Au/electrolytic Ni/Cu bond pads with the Sn–Zn composite alloys. The more Ag particles that were added to the Sn–Zn solder, the more Ag–Zn compound formed to thicken the uppermost IMC layer. The dissolved Ag–Zn IMCs formed in the bulk solder redeposited over the initially formed interfacial Au–Zn IMC layer, which prevented the whole IMC layer lifting-off from the pad surface. Cross-sectional studies of the interfaces were also conducted to correlate with the fracture surfaces.     

The reliability study of selected Sn–Zn based lead-free solders on Au/Ni–P/Cu substrate

Since both Ag and In are important melting point depressants in Sn–Zn based solders, a series Sn–Zn based solders with various amounts of Ag and In additions was studied in the experiment. The melting behavior of solder alloys, wetting characteristics, coefficients of thermal expansion, microstructural evolution and long-term reliability of the selected Sn–Zn based solder on Au/Ni–P metallized copper substrate were examined. Based on the experimental result, there is little change in the melting range of Sn–Zn based solder alloys by minor addition of Ag. On the contrary, the melting point of Sn–Zn based alloys can be effectively decreased by In additions. However, the difference between solidus and liquidus temperature is broadened as the increment of In into Sn–Zn based solders. 76Sn–9Zn–15In has the lowest liquidus temperature among all alloys, and it can effectively bond the Au/Ni–P metallized copper substrate. The microstructure of 76Sn–9Zn–15In alloy soldered at 200 °C for 20 min is primarily comprised of Sn–In γ phase and needle-like ZnO₂. Since there is no flux usage during soldering, zinc oxide cannot be avoided even the process performed under 2×10⁻² mbar vacuum environment. It is also noted that there is no interfacial reaction layer between 76Sn–9Zn–15In and Au/Ni–P metallized copper substrate after soldering. However, there is a reaction layer between 76Sn–9Zn–15In and substrate as the soldered specimen aged at 90 °C for 168 h. Its chemical composition is close to Zn-rich γ phase (NiZn₃) alloyed with minor Sn, In, Cu and P. For the specimen further aged at 90 °C for 336 h, there are cracks along the interface between solder alloy and electroless Ni–P layer. The oxidation of the interfacial Zn-rich γ phase plays an important role in deterioration of the bonding between 76Sn–9Zn–15In and Au/Ni–P metallized copper substrate.     

The formation and growth of intermetallic compounds and shear strength at Sn–Zn solder/Au–Ni–Cu interfaces

The microstructures and shear strength of the interface between Sn–Zn lead-free solders and Au/Ni/Cu interface under thermal aging conditions was investigated. The intermetallic compounds (IMCs) at the interface between Sn–Zn solders and Au/Ni/Cu interface were analyzed by field emission scanning electron microscopy and transmission electron microscopy. The results showed the decrease in the shear strength of the interface with aging time and temperature. The solder ball with highly activated flux had about 8.2% increased shear strength than that with BGA/CSP flux. Imperfect wetting and many voids were observed in the fracture surface of the latter flux. The decreased shear strength was influenced by IMC growth and Zn grain coarsening. In the solder layer, Zn reacted with Au and then was transformed to the β-AuZn compound. Although AuZn grew first, three diffusion layers of γ-Ni₅Zn₂₁ compounds were formed after aging for 600 h at 150 °C. The layers divided by Ni₅Zn₂₁ (1), (2), and (3) were formed with the thickness of 0.7 μm, 4 μm, and 2 μm, respectively.     

Properties of low temperature Sn–Ag–Bi–In solder systems

The metallurgical and mechanical properties of Sn–3.5 wt%Ag–0.5 wt%Bi–xwt%In (x = 0–16) alloys and of their joints during 85 °C/85% relative humidity (RH) exposure and heat cycle test (−40–125 °C) were evaluated by microstructure observation, high temperature X-ray diffraction analysis, shear and peeling tests. The exposure of Sn–Ag–Bi–In joints to 85 °C/85%RH for up to 1000 h promotes In–O formation along the free surfaces of the solder fillets. The 85°C/85%RH exposure, however, does not influence the joint strength for 1000 h. Comparing with Sn–Zn–Bi solders, Sn–Ag–Bi–In solders are much stable against moisture, i.e. even at 85 °C/85%RH. Sn–Ag–Bi–In alloys with middle In content show severe deformation under a heat cycles between −40 °C and 125 °C after 2500 cycles, due to the phase transformation from β-Sn to β-Sn + γ-InSn₄ or γ-InSn₄ at 125 °C. Even though such deformation, high joint strength can be maintained for 1000 heat cycles.     

Interfacial microstructure and shear strength of Ag nano particle doped Sn-9Zn solder in ball grid array packages

Sn-9Zn solder joints containing Ag nano particles were prepared by mechanically mixing Ag nano particles (0.3, 0.5 and 1 wt%) with Sn-9Zn solder paste. In the monolithic Sn-Zn solder joints, scallop-shaped AuZn₃ intermetallic compound layers were found at their interfaces. However, after the addition of Ag nano particles, an additional uniform AgZn₃ intermetallic compound layer well adhered to the top surface of the AuZn₃ intermetallic compound layer was found. In addition, in the solder ball region, fine spherical-shaped AgZn₃ intermetallic compound particles were observed as well as Zn-rich and β-Sn phases. With the addition of Ag nano particles, the shear strengths consistently increased with an increase in the Ag nano particle content due to the uniform distribution of fine AgZn₃ intermetallic compound particles. The shear strength of monolithic Sn-Zn and 1 wt% Ag nano particle content Sn-Zn solder joints after one reflow cycle were about 42.1 MPa and 48.9 MPa, respectively, while their shear strengths after eight reflow cycles were about 39.0 MPa and 48.4 MPa, respectively. The AgZn₃ IMCs were found to be uniformly distributed in the β-Sn phase for Ag particle doped Sn-9Zn composite solder joints, which result in an increase in the tensile strength, due to a second phase dispersion strengthening mechanism. The fracture surface of monolithic Sn-Zn solder exhibited a brittle fracture mode with a smooth surface while Sn-Zn solder joints containing Ag nano particles showed a typical ductile failure with very rough dimpled surfaces.     

Microstructure and shear strength evolution of SnAg/Cu surface mount solder joint during aging

The effect of aging at 150°C on the microstructure and shear strength of SnAg/Cu surface mount solder joint has been investigated with comparison to 62Sn36Pb2Ag/Cu. It is found that the diffusion coefficient of intermetallic compounds at SnAg/Cu interface is smaller than that of intermetallic compounds at SnPbAg/Cu interface at 150°. The shear strength of SnAg solder joint is higher and decreases at a smaller rate during aging compared to that of SnPbAg solder joint. The fracture surface analysis shows that as the aging time increases, the fracture takes place along the solder/Cu₆Sn₅ interface with an extension toward the Sn−Cu intermetallic layer.     

Characteristics of Sn8Zn3Bi solder joints and crack resistance with various PCB and lead coatings

Reliability of QFP (quad flat package) solder joints after thermal shock was investigated for PCB’s and connecting leads plated with several different alloy coatings before soldering. Sn–8 wt%Zn–3 wt%Bi (hereafter, Sn–8Zn–3Bi) was selected as a solder, and FR-4 PCB’s finished with Cu/Sn, Cu/OSP and Cu/Ni/Au were used as substrates. The leads of the QFP were Cu plated with Sn–10 wt%Pb, or Sn, or Sn–3 wt%Bi. The QFP chips were mounted on the substrates using a Sn–8Zn–3Bi solder paste and reflowed in air atmosphere. The pull strength and microstructure for the soldered leads of QFP were evaluated before and after thermal shock testing. The leads plated with Sn or Sn–3Bi showed approximately 40–50% higher pull strength than the reference value of a Sn–37%Pb solder joint for all PCB-finishes. However, in the case of leads coated with Sn–10Pb, the pull strength of the leads soldered to a Sn-finished PCB was 21% lower than the reference value. In microstructure analysis of the joints with Sn–10Pb-plated leads, cracks were found along the bonded interface for Sn-finished PCB. The cracks were believed to start from the low melting temperature phase, 49.38 wt% Pb–32.58 wt%Sn–18.03 wt%Bi, found around the crack, and then propagated through Cu–Zn intermetallic compound. Meanwhile, even when using Sn–10Pb-plated leads, the PCB’s finished with Cu/Ni/Au coating had about 30% higher strength than the reference value, and cracks were hardly found on the soldered joint. Thus, even with Sn–10Pb-plated leads the Cu/Ni/Au-finished PCB’s were evaluated to be as reliable as the reference joint.     

Solder joint reliability evaluation of chip scale package using a modified Coffin–Manson equation

Thermal cycle tests were performed for chip scale package (CSP) solder joints with Sn–37mass%Pb under several thermal cycle conditions. Under the conventional thermal cycle conditions, which heat up to approximately 100 °C, microstructure coarsening occurred and solder joints were fractured. The thermal fatigue lives followed the modified Coffin–Manson equation. The exponential factors m and n, and the activation energy Q in that equation were evaluated as 0.33, −1.9 and 15.5 kJ/mol, respectively. When the maximum temperature is room temperature and the temperature range is very narrow, the solder joint fracture occurred without microstructure coarsening, and the thermal fatigue life does not follow the modified Coffin–Manson equation.     

Study on low-Ag content Sn–Ag–Zn/Cu solder joints

The eutectic Sn–Ag–Cu solder is the most popular lead free solder. But reliability and cost issues limit its application. On the other hand, Sn–Ag–Zn system has many advantages comparing with Sn–Ag–Cu. In this paper, interfaces of Sn–xAg–1Zn/Cu and Sn–2Ag–xZn/Cu (x = 1, 2, 3), Sn–2Ag–2.5Zn/Cu and Sn–1.5Ag–2Zn/Cu solders joints were studied to understand effects of Ag and Zn contents. Results show that shearing strength of as-reflowed Sn–2Ag–2Zn/Cu and Sn–1.5Ag–2Zn/Cu joints is higher than other joints. Because of the strong Cu–Sn reaction and the formation of Ag₃Sn, the Sn–Ag–Zn series solder joints are not suitable for use above 150 °C temperature. After 250 °C soldering for 4 h, while the Zn content increased from 1 wt% to 2 wt%, the interfacial IMC of Sn–Ag–Zn/Cu altered from Cu₆Sn₅ to Cu₅Zn₈. The Cu₅Zn₈ interface has higher shearing strength than Cu₆Sn₅ interface. Relationships among microstructure, strength and aging condition are discussed.     

Effect of aging on the microstructure and shear strength of SnPbAg/Ni-P/Cu and SnAg/Ni-P/Cu solder joints

The effect of aging on the microstructure and shear strength of 62Sn36Pb2Ag/Ni-P/Cu and SnAg/Ni-P/Cu surface mount solder joints was investigated. An intermetallic (IMC) layer of Ni₃Sn₄ forms at the interface between both solders and the Ni-P barrier layer and it thickens with aging time, with a decrease in the thickness of remaining Ni-P layer. The SnAg solder joint initially has a greater shear force than that of SnPbAg, but it drops dramatically after 250 h aging, and fracture occurs at the Ni-P/Cu interface afterwards, although it initiates in the solder in the initial stage of aging. The fracture in SnAg solder joint may arise from the excessive depletion of Ni characterized by a rapid accumulation of P in the remaining Ni-P layer, which results in a poor adhesion between the Ni-P layer and the Cu substrate. However, for the SnPbAg solder joint, the shear force initially decreases rapidly then asymptotically approaches a minimum, and fracture occurs from inside solder toward the solder/Ni-P interface. SnPbAg solder joint keeps relatively higher shear strength compared to SnAg solder joint after long term aging even though it decreases with aging time.     

Isothermal aging characteristics of Sn–Pb micro solder bumps

The shear strength of the under bump metallurgy (UBM) structure in both the high-melting solder bump and low-melting solder bump after aging were evaluated. Scanning electron microscopy and transmission electron microscopy were examined in the intermetallic compounds (IMCs) and bump joint profiles at the interface between solder and UBM. In 900 h aging experiments, the maximum shear strength of Sn–97wt.%Pb and Sn–37wt.%Pb decreased by 25% and 20%, respectively. The growth of Cu₆Sn₅ and Cu₃Sn was ascertained by the aging treatment. The crack path changes from the interior of a solder to the IMC interface. Compare with the Cu–Sn IMC, the amount of Ni–Sn IMC was small. The Ni layer is considered as the diffusion barrier.     

Reliability study of Sn–Ag–Cu–Ce soldered joints in quad flat packages

The reliability of Sn–Ag–Cu–Ce lead-free soldered joints in quad flat packages under thermal cycling was investigated based on finite element simulation and experiments. The stress and strain response of fine pitch QFP device lead-free soldered joints were analyzed using finite element method based on Garofalo–Arrhenius model. The simulated results indicate that the creep distribution is not uniform, the heel of joints is the maximum creep strain concentrated sites. And comparisons were then made with experimental results of the cracks observed in the Sn–Ag–Cu–Ce soldered joints subjected to the temperature cycled experiment. In addition, the relative mechanical and metallurgical factors, which dominate the failure of soldered joints, were utilized to analyze the phenomena. The fracture surfaces indicate that crack initiate and propagate along the interface among bulk Cu₆Sn₅ phases in Sn–Ag–Cu–Ce soldered joints.     

The influence of Sn–Cu–Ni(Au) and Sn–Au intermetallic compounds on the solder joint reliability of flip chips on low temperature co-fired ceramic substrates

The formation of intermetallic compounds in the solder joint of a flip chip or chip scale package depends on the under bump metallurgy (UBM), the substrate top surface metallisation, the solder alloy and the application conditions. To evaluate the influence of intermetallic compounds on the solder joint reliability, a detailed study on the influence of the UBM, the gold finish thickness of the substrate top surface metallisation, the solder alloy and the aging conditions has been conducted. Flip chips bumped with different solder alloys were reflow-mounted on low temperature co-fired ceramic substrates. The flip chip package was then aged at high temperature and a bump shear test followed to examine the shear strength of the solder joint at certain aging intervals. It was found that the type of UBM has a great impact on the solder joint reliability. With Ni(P)/Au as the UBM, well-documented gold embrittlement was observed when the gold concentration in the eutectic SnPb solder was about 3 wt%. When Al/Ni(V)/Cu was used as the UBM, the solder joint reliability was substantially improved. Copper dissolution from the UBM into the solder gives different intermetallic formations compared to Ni(P)/Au as UBM. The addition of a small amount of copper in the solder alloy changed the mechanical property of the intermetallic compound, which is attributed to the formation of Sn–Cu–Ni(Au) intermetallic compounds. This could be used in solving the problem of the AuSn₄ embrittlement. The formation and the influence of this Sn–Cu–Ni(Au) intermetallic phase are discussed. The gold concentration in the solder joint plays a role in the formation of intermetallic compounds and consequently the solder joint reliability, especially for the Sn–Ag–Cu soldered flip chip package.     

Drop impact reliability testing for lead-free and lead-based soldered IC packages

Board-level drop impact testing is a useful way to characterize the drop durability of the different soldered assemblies onto the printed circuit board (PCB). The characterization process is critical to the lead-free (Pb-free) solders that are replacing lead-based (Pb-based) solders. In this study, drop impact solder joint reliability for plastic ball grid array (PBGA), very-thin quad flat no-lead (VQFN) and plastic quad flat pack (PQFP) packages was investigated for Pb-based (62Sn–36Pb–2Ag) and Pb-free (Sn–4Ag–0.5Cu) soldered assemblies onto different PCB surface finishes of OSP (organic solderability preservative) and ENIG (electroless nickel immersion gold). The Pb-free solder joints on ENIG finish revealed weaker drop reliability performance than the OSP finish. The formation of the brittle intermetallic compound (IMC) Cu–Ni–Sn has led to detrimental interfacial fracture of the PBGA solder joints. For both Pb-based and Pb-free solders onto OSP coated copper pad, the formation of Cu₆Sn₅ IMC resulted in different failure sites and modes. The failures migrated to the PCB copper traces and resin layers instead. The VQFN package is the most resistant to drop impact failures due to its small size and weight. The compliant leads of the PQFP are more resistant to drop failures compared to the PBGA solder joints.