Study of the Thermomechanical Inelastic Energy Response of Backward Compatible Solder Joints Made With Sn-3.8Ag-0.7Cu versus Reballed Sn37.0Pb Components

2011 ◽  
Author(s):  
Lorraine M. Renta ◽  
Ricky Valentin ◽  
Pedro Quintero ◽  
David Ma ◽  
Alan Hovland
Keyword(s):  
Energy Density ◽  
Solder Alloy ◽  
Bulk Solder ◽  
Thermal Cycles ◽  
Ball Grid Arrays ◽  
Physical Mechanisms ◽  
Snpb Solder ◽  
Solder Balls ◽  
Free Solder ◽  
Life Predictions

Conflicting results in reliability tests for backward compatible and Pb-free soldered assemblies has motivated RoHS-exempted industries to practice reballing. Reballing is the name given to the process of removing Pb-free solder balls from the copper (Cu) pads of the Ball Grid Array (BGA) components received through the supply chain and replacing them with SnPb solder balls. Recent studies on the subject of reballing have shown the possibility that the removed Pb-free solder ball leaves behind some intermetallic remnants of the Pb-free solder alloy and the Cu from the pads. A modeling approach based on physics of failure (PoF) is presented that quantifies the interactions between different thermal cycles applied to reballed Ball Grid Arrays (BGA) with remnants of the Pb-free solder alloy on the Cu pads. These resulting interactions are compared to backward compatible Sn-3.8 Ag-0.7Cu (SAC) balls soldered with eutectic SnPb paste for the same thermal cycles. For the latter, the risk of having improper mixing during the assembly process is also studied. The approach is formulated at the microscale, incorporating physical mechanisms of the intermetallics created with Cu, and at the macroscale, capturing the creep phenomenon of the bulk solder as dominant failure driver. Simulation results show that the reballed cases have higher inelastic energy density per cycle averaged over damage volume near the copper pads and that the inelastic energy density is higher across the bulk of the improperly mixed backward compatible solder balls when compared to properly mixed backward compatible solder balls. The results of this study permit extrapolation of laboratory results to field life predictions and to explore the design of accelerated re-balled or backward compatible BGA tests that relate better to application-specific usage environments.

Review on the effect of alloying element and nanoparticle additions on the properties of Sn-Ag-Cu solder alloys

2014 ◽  
Vol 26 (3) ◽  
pp. 147-161 ◽  
Author(s):  
Ervina Efzan Mhd Noor ◽  
Amares Singh
Keyword(s):  
Melting Temperature ◽  
Solder Alloy ◽  
Electronic Packaging ◽  
Environmental Concern ◽  
Bulk Solder ◽  
Solidification Temperature ◽  
Content Type ◽  
Snpb Solder ◽  
Packaging Industry ◽  
Sac Solder

Purpose – The aim of the present study was to gather and review all the important properties of the Sn–Ag–Cu (SAC) solder alloy. The SAC solder alloy has been proposed as the alternative solder to overcome the environmental concern of lead (Pb) solder. Many researchers have studied the SAC solder alloy and found that the properties such as melting temperature, wettability, microstructure and interfacial, together with mechanical properties, are better for the SAC solder than the tin – lead (SnPb) solders. Meanwhile, addition of various elements and nanoparticles seems to produce enhancement on the prior bulk solder alloy as well. These benefits suggest that the SAC solder alloy could be the next alternative solder for the electronic packaging industry. Although many studies have been conducted for this particular solder alloy, a compilation of all these properties regarding the SAC solder alloy is still not available for a review to say. Design/methodology/approach – Soldering is identified as the metallurgical joining method in electronic packaging industry which uses filler metal, or well known as the solder, with a melting point < 425°C (Yoon et al., 2009; Ervina and Marini, 2012). The SAC solder has been developed by many methods and even alloying it with some elements to enhance its properties (Law et al., 2006; Tsao et al., 2010; Wang et al., 2002; Gain et al., 2011). The development toward miniaturization, meanwhile, requires much smaller solder joints and fine-pitch interconnections for microelectronic packaging in electronic devices which demand better solder joint reliability of SAC solder Although many studies have been done based on the SAC solder, a review based on the important characteristics and the fundamental factor involving the SAC solder is still not sufficient. Henceforth, this paper resolves in stating all its important properties based on the SAC solder including its alloying of elements and nanoparticles addition for further understanding. Findings – Various Pb-free solders have been studied and investigated to overcome the health and environmental concern of the SnPb solder. In terms of the melting temperature, the SAC solder seems to possess a high melting temperature of 227°C than the Pb solder SnPb. Here, the melting temperature of this solder falls within the range of the average reflow temperature in the electronic packaging industry and would not really affect the process of connection. A good amendment here is, this melting temperature can actually be reduced by adding some element such as titanium and zinc. The addition of these elements tends to decrease the melting temperature of the SAC solder alloy to about 3°C. Adding nanoparticles, meanwhile, tend to increase the melting temperature slightly; nonetheless, this increment was not seemed to damage other devices due to the very slight increment and no drastic changes in the solidification temperature. Henceforth, this paper reviews all the properties of the Pb-free SAC solder system by how it is developed from overcoming environmental problem to achieving and sustaining as the viable candidate in the electronic packaging industry. The Pb-free SAC solder can be the alternative to all drawbacks that the traditional SnPb solder possesses and also an upcoming new invention for the future needs. Although many studies have been done in this particular solder, not much information is gathered in a review to give better understanding for SAC solder alloy. In that, this paper reviews and gathers the importance of this SAC solder in the electronic packaging industry and provides information for better knowledge. Originality/value – This paper resolves in stating of all its important properties based on the SAC solder including its alloying of elements and nanoparticles addition for further understanding.

Wettability and Bond Shear Strength of Sn-9Zn Lead-Free Solder Alloy Reflowed on Copper Substrate

2015 ◽  
Vol 830-831 ◽  
pp. 215-218 ◽  
Author(s):  
Sanjay Tikale ◽  
Mrunali Sona ◽  
K.N. Prabhu
Keyword(s):  
Shear Strength ◽  
Solder Alloy ◽  
Copper Substrate ◽  
Bulk Solder ◽  
Lead Free ◽  
Lead Free Solder ◽  
Reflow Time ◽  
Bond Shear Strength ◽  
Lead Free Solder Alloy ◽  
Free Solder

Lead-free solders are environment friendly and are in great demand for microelectronic applications. In the present study, Sn-9Zn lead free solder alloy was solidified on Cu substrate for different reflow times from 10 to 1000s. The influence of reflow time on wetting, formation of intermetallic compounds (IMCs) and bond shear strength was studied using dynamic contact angle analyzer, bond tester and scanning electron microscopy. The results indicate that, the wettability of the solder alloy increased with increase in reflow time. Microstructure study revealed the presence of Cu5Zn8 and CuZn5 IMCs at the interface. The thickness of an IMC increased with increase in the reflow time. The mean thickness of about 11μm for Cu5Zn8 IMC layer was observed for the reflow time of 1000s. The thickness of CuZn5 layer increased up to a reflow time of 100s and decreases thereafter. The bond shear strength increased up to 100s and decreased with increase in reflow time. The decrement in shear strength at higher reflow time is mainly due to excessive thickness of Cu5Zn8 IMC layer and diffusion of Sn from bulk solder towards the substrate. The excessive thick IMC layer exhibited pre micro-cracks led to the brittle failure of bond under the influence of shear stress.

Nanoparticles of SnAgCu lead-free solder alloy with an equivalent melting temperature of SnPb solder alloy

2009 ◽  
Vol 484 (1-2) ◽  
pp. 777-781 ◽  
Author(s):  
Yulai Gao ◽  
Changdong Zou ◽  
Bin Yang ◽  
Qijie Zhai ◽  
Johan Liu ◽  
...  
Keyword(s):  
Melting Temperature ◽  
Solder Alloy ◽  
Lead Free ◽  
Lead Free Solder ◽  
Snpb Solder ◽  
Lead Free Solder Alloy ◽  
Free Solder

Thermal Shock and Drop Test Behaviour of Area Array Packages in Forward and Backward Compatible Assemblies

2009 ◽  
Author(s):  
Bankeem V. Chheda ◽  
Sathishkumar Sakthivelan ◽  
S. Manian Ramkumar ◽  
Reza Ghaffarian
Keyword(s):  
Solder Ball ◽  
Lead Free ◽  
Lead Free Solder ◽  
Mechanical Shock ◽  
Lead Frame ◽  
Shock Test ◽  
Area Array ◽  
Snpb Solder ◽  
Solder Balls ◽  
Free Solder

With lead-free implementation it is important to examine the behaviour of the solder joint at the component level and at the board level. Assembly related issues along with component reliability are the main focus of this experimental research. This experimental study aims to evaluate the mechanical integrity of solder joints comprising of both lead-free and SnPb alloys. Lead-free and SnPb solder pastes were used to assemble the components. This will allow us to check the forward and the backward compatibility of the solder alloys. The test vehicle considered for this study contained a variety of components such as ultra chip scale package (UCSP192), package on package (PoP), plastic ball grid array (PBGA-676 & 1156), very thin chip array BGA (CVBGA432), thin small outline package (TSOP-40 & 48), dual row micro-lead frame (DRMLF), micro-lead frame (MLF-36 & 72), and chip resistors (0201, 0402, 0603). The scope of this paper is limited to the performance evaluation for area array packages only. Solder ball alloy for the area array packages included SAC 305, SAC405, SAC105, SnAg and SnPb. Three different PCB surface finishes, electroless nickel immersion gold (ENIG), SnPb hot air solder level (HASL), and immersion silver (ImAg) were used. Different solder ball alloys and surface finish combinations provided good comparison data for investigating the assembly performance. The PCB assemblies were subjected to mechanical shock test in the as-soldered condition and also after 200 and 500 thermal shock cycles at −55 to 125°C. For the mechanical shock test, the assemblies were subjected to 30 drops from a height of 3 ft, generating an average G force of 485N. After each drop the components were checked for the continuity of the total daisy chain. The number of drops for the first failure was used in analyzing the performance of the components for various combinations. Since each component had many independent daisy chains, the failure of the individual daisy chains was later used in determining the location of the failure and how it progressed. Two sets of test vehicles were assembled. One set comprised of components with lead-free solder balls of different composition (SAC305, SAC405, SAC105, SnAg) and the other set comprised of components with lead-free solder balls and SnPb solder balls (SAC305, SAC405, SnPb). This mix of alloy composition provided adequate data for comparison. It was critical to optimize the process in order to enable the melting of the mix of alloys. The area array package performance was evaluated when assembled with lead-free and SnPb solder paste. Some of the assemblies were cross-sectioned after the tests and the microstructure of the solder joint was analyzed to study the possible cause for assembly failure.

scholarly journals Study on Creep Damage in Sn60Pb40 and Sn3.8Ag0.7Cu (Lead-Free) Solders in c-Si Solar PV Cell Interconnections under In-Situ Thermal Cycling in Ghana

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 441
Author(s):  
Frank Kwabena Afriyie Nyarko ◽  
Gabriel Takyi ◽  
Francis Boafo Effah
Keyword(s):  
Energy Density ◽  
Creep Strain ◽  
Thermal Cycle ◽  
Creep Damage ◽  
Temperature Cycle ◽  
Solder Interconnection ◽  
Snpb Solder ◽  
Pv Modules ◽  
Free Solder ◽  
Density Methods

A numerical study on the creep damage in soldered interconnects in c-Si solar photovoltaic cells has been conducted using equivalent creep strain, accumulated creep strain and accumulated creep energy density methods. The study used data from outdoor weathering of photovoltaic (PV) modules over a three-year period (2012–2014) to produce temperature cycle profiles that served as thermal loads and boundary conditions for the investigation of the soldered interconnects’ thermo-mechanical response when exposed to real-world conditions. A test region average (TRA) temperature cycle determined in a previous study for the 2012–2014 data was also used. The appropriate constitutive models of constituent materials forming a typical solar cell were utilized to generate accurate material responses to evaluate the damage from the thermal cycles. This study modeled two forms of soldered interconnections: Sn60Pb40 (SnPb) and Sn3.8Ag0.7Cu (Pb-free). The results of the damage analysis of the interconnections generated from the thermal cycle loads using accumulated creep strain method showed that the Pb-free solder interconnection recorded greater damage than that of the SnPb-solder interconnection for the TRA, 2012, 2013 and 2014 temperature cycles. The percentage changes from SnPb to Pb-free were 57.96%, 43.61%, 44.87% and 45.43%, respectively. This shows significant damage to the Pb-free solder under the TRA conditions. Results from the accumulated creep energy density (ACED) method showed a percentage change of 71.4% (from 1.3573 × 105 J/mm3 to 2.3275 × 105 J/mm3) in accumulated creep energy density by replacing SnPb-solder with Pb-free solder interconnection during the TRA thermal cycle. At the KNUST test site in Kumasi, Ghana, the findings show that Sn60Pb40 solder interconnections are likely to be more reliable than Pb-free solder interconnections. The systematic technique employed in this study would be useful to the thermo-mechanical reliability research community. The study also provides useful information to PV design and manufacturing engineers for the design of robust PV modules.

Stress Relaxation and Fatigue Characterisation of Eutectic SnPb Solder Alloy

2011 ◽  
Vol 462-463 ◽  
pp. 530-534
Author(s):  
Mohd Amin Hashim ◽  
A. Rahmat
Keyword(s):  
Stress Relaxation ◽  
Solder Alloy ◽  
Semiconductor Industry ◽  
Fatigue Tests ◽  
Bulk Solder ◽  
Creep Stress ◽  
Snpb Solder ◽  
Single Temperature ◽  
Binary Eutectic ◽  
Eutectic Snpb

Soldering is the most important joining technology in the semiconductor industry, especially for IC chip packaging. The binary eutectic SnPb alloy had been in used for decades, before regulations and restriction on the usage of lead in solders was imposed. Thus, replacing SnPb solder alloy with Pb-free solders has also been an issue in the electronic industry. The previously used SnPb alloy was in used due to several reasons, namely (a) it has low melting temperature (183oC) and solidified at a single temperature to form eutectoid composition, (b) binary in composition and is readily available commercially and (c) many researches had been undertaken in the previous decades. Creep, stress relaxation and fatigue tests were conducted on eutectic SnPb solder alloy in order to study the alloy mechanical characteristics, and hence a suitable Pb-free solder alloy could be chosen as a replacement alloy. In this study, creep, stress relaxation and fatigue tests were conducted on eutectic SnPb solder alloy at 30oC and 50oC, respectively. The study showed that stress relaxation in the alloy decayed instantaneously to zero-value when cycling was done at R=-1 and that cycling was done at 600 cycle per minute (CPM) which enable fatigue test to be conducted on the bulk solder alloy. A non-zero stress relaxation value will result in the alloy to failed predominantly due to creep and fatigue failure will not be observed.

A review: Effect of nanoparticles addition on the properties of Sn-Ag-Cu lead free solder alloy

2021 ◽  
Author(s):  
M. N. Ervina Efzan ◽  
M. M. Nur Haslinda ◽  
M. M. Al Bakri Abdullah
Keyword(s):  
Solder Alloy ◽  
Lead Free ◽  
Lead Free Solder ◽  
Lead Free Solder Alloy ◽  
Free Solder
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