Dissertations / Theses on the topic 'SAC405'

The master thesis analyses electrical conductivity of lead-free solder joints. The test method design for monitoring the electrical conductivity of the soldered joint is described in the practical part. Simulated BGA package with four pin (BGA4) is used for experiments. Tested PCBs are subjected to isothermal aging and current load. During isothermal aging is measured electrical conductivity and optical microscope is used for intermetallic layer (IMC) growth observation. Two types of surface finish (OSP and ENIG) are used for tests and three diameters of solder terminal balls (solder alloy SAC405). The influence of the ratio area connection / solder volume (ratio S / V) on lead-free solder joints conductivity was evaluated.

The theoretical part of dissertation is devoted to familiarization with the process of assembly and soldering of PCBs. There are described the selected types of lead-free solder paste, the various procedures of flux deposition, where the greater part is focuses to the printing through template. Also, I analyze the different procedures shouldering and soldering. I focused mainly on the mechanical mounting of SMD components soldering with help convection reflow and soldering in the vapor. In the practical part is described the design of the test PCB, methodology of assembly PCB and soldering various technologies with predefined settings. The analysis of the results is done by a non-destructive x-ray method and destructive micro-cut method. The x-ray method detects the position and size of the voids in the solder. This information is used for faster processing of micro-cut. The micro-cut method is included in the analysis for a more detailed examination of the solder joint. At the end of the thesis, there is a summary of the recommendation that the setting of the manufacturing process increases the quality of the brazed joint.

With the rapid development in electronic packaging due to product miniaturisation, the size of solder joints is decreasing considerably, thus the failure of solder interconnects induced by electro-migration (EM) and thermo-migration (TM) became a reliability concern. The incorporation of foreign reinforcement can effectively improve properties of the solder alloys. However, this presents an imperative need for a further investigation to elaborate the underlying fundamentals associated with the reliability of reinforced solders. In this study, the Sn-Ag-Cu (SAC) based solder alloy powders as matrix were incorporated with Fullerene (FNS), TiC and Ni-coated graphene (NG) reinforcements to form composite solders through powder metallurgical method. These composite solders were then characterised in terms of their microstructure, physical property, solderability, followed by a systematic investigation of their performance under isothermal ageing, current stressing and large thermal gradient, respectively. The results showed that three types of reinforcements were successfully incorporated into the solder matrix; with all reinforcements added being embedded in the solder matrix or around the intermetallic compounds (IMC). The average loss of FNS and TiC particles in the solders was approximately 80% after the initial reflow, while this was only 40% for NG particles. It has been observed that β-Sn and Ag3Sn in the SAC solder alloys can be refined by adding appropriate amount of FNS and TiC, which is beneficial to the wettability with a reduced coefficient of thermal expansion (CTE) with the minimal influence on the melting point and electrical resistivity of solder alloys. For the SAC alloys without reinforcements, obvious extrusion of interfacial IMC at the anode was present after 360 hours of current (1.5×104 A/cm2) stressing, while the changes of surface profiles of all reinforced solders were unnoticeable. Under the current stressing regimes, a continuous increase of interfacial IMCs at the anode of the original SAC alloys was observed, but decreased at the cathode with stressing time. For the composite solders, both anode and cathode showed a continuous growth of interfacial IMCs; the growth rates of IMCs at the anode were greater than that at cathode. In addition, NG and TiC were found to be most effective to retard the growth of Cu3Sn IMC under current stressing. A gradient in hardness across the stressed SAC joints was present, where it was harder at anode. However, no such obvious gradient was found in SAC/FNS and SAC/NG solder joints. FNS and NG were proven to be beneficial to prolong the service life of solder joints up to approximately 7.6% and 10.4% improvements, respectively. Thermal stressing made the interfacial IMC in the original SAC joints to grow at the cold end considerably; causing serious damage at the hot end after 600 hours under temperature gradient of 1240K/cm stressing; a large number of IMCs, cracks and voids appeared in the SAC solder joints. However, a uniform increase of IMCs at both sides in the composite solders was observed without apparent damages at the interfaces under the same thermal stressing conditions, indicating an effective reduction of the elemental migration in the reinforced solders. Although there were also some voids and IMCs formed in the composite solder joints after a long-term thermal stressing, the integrity of the composite solder joints was enhanced compared with the SAC alloys. During thermal stressing, the dissolution rate of Cu atom into the SAC solder joints was estimated to be 3.1×10-6 g/h, while the values for SAC/FNS, SAC/NG and SAC/TiC were only 1.22×10-6 g/h, 1.09×10-6 g/h and 1.67×10-6 g/h, respectively.

This work is a research on the topic of reactive nanoparticles and their agitation into the solder paste, which it also describes. It describes in detail the properties of each solder alloys. It explains the creation of intermetallic layers in the soldering process and examines their structure. It also focuses on the evaluation and methodology of testing the properties of solder pastes. In the practical part, individual tests are performed with PF606 and PF610 solder paste.

碩士
義守大學
機械與自動化工程學系碩士班
98
The objective of this research is focused on an advanced electro-thermo coupling model which is developed to investigate the electromigration and electro-thermo-mechanical effects for SAC405 alloy on electronic packaging, especially on Package-on-Package (POP). POP packaging involves in Sn4.0Ag0.6Cu (SAC405) solder ball on package. For the past two decades, electromigration on Integrated Circuit (IC) packaging has been a serious reliability issue, which drives many researchers and engineers concentrated on this study. The current density arising in the Copper trace above SAC405 solder ball imply the hot spot where results in an electromigration along the current direction. Previous studies experimentally demonstrated that electromigration on the solder bump/solder ball is the most tenacious cause affected reliability. Copper ionic corrosion always occurs under high current density at leveled temperature. Working temperature and current density are the main factors which directly impact electromigration behaviors. Higher thermal resistance and lower resistivity implies higher anti-eletromigration capability. Current crowding is reported on the corner where geometry dramatically changes. In this research, electric analysis is first performed to evaluate the current density and current crowding and follow-by electro-thermo coupled design on the POP package. Because the current is crowded due to complex geometry of structure, a single solder ball and an entire bond wire are modeled to simply the problem. As electricity analysis is continued, the selected solder ball is electrified to observe the current crowding. Black’s equation is employed to determine the predicted equivalent life time for SAC405 solder ball. Material properties, such as electrical resistivity and temperature coefficient of resistance are crucial and vary from working temperature. Mesh density is required to evaluate the convergence for structure integrity. Finite element analysis reveal the maximum electro-thermo-mechanical stress is located at the regions where electromigration potentially occurs. Reliability on SAC405 solder ball is evaluated. Current crowding, temperature distribution and electro-thermo induced effective stress distribution are predicted. A series of comprehensive parametric studies were conducted in this research.

碩士
國立中山大學
機械與機電工程學系研究所
96
The fatigue-induced solder joint failure of surface mounted electronic devices has become one of the most critical reliability issues in electronic packaging industry. Prediction of the shape of solder joints has drawn special attention to the related development and engineering applications. Numerous solder joint models, based on energy minimization principle and analytical methods, have been proposed and developed. The methods are extensively utilized to the shape design of solder joint. However, it is important to find a suitable method to real applications. Herein, a series of experiments with different geometric parameters of SAC405 solder joints were carried out and the results were compared with the prediction by Surface Evolver Program. The changes of geometric shape with respect to different parameters of solder joint were also discussed. The influence of the geometric parameters, such as volume of solder joint, package weight, solder surface tension, and gravity force to the shape of solder joint were investigated. Two experiments with SAC405 solder balls were carried out. One is to observe the different reflowed geometry shape of solder balls with various volumes, and another is to observe the different reflowed geometry shape of solder balls with various loadings on them. The results show that the models made by Surface Evolver program are very similar to the real shapes observed by experiments, and the differences are between -3% ~ 6.5%. Thus, the results show that the predicted shapes are satisfactorily suitable. Finally, the predicted models by Surface Evolver program were also put into the ANSYS program, and preceded the fatigue life prediction due to thermal cycling tests. The comparison of the effect on fatigue life with respect to different geometry shapes is illustrated. The results show the shape of solder ball due to high loadings is better than that in thermal cycling tests.

碩士
國立交通大學
工學院精密與自動化工程學程
100
This study concentrates on the soldering reactions and the mechanical response between Sn-1.0Ag-0.5 and Sn-3.0Ag-0.5Cu lead-free solders and ENEPIG surface finish. In order to investigate mechanical property of this two different alloy, the samples are firstly stored in high temperature condition then tested with two difference shear rate, i.e., ball shear test(0.0001 m/s) and high speed ball shear test(1 m/s). The results indicated that both shear strength in difference shear rate of Sn-1.0Ag-0.5Cu joints lower than Sn-3.0Ag-0.5Cu, however, the fracture resistance ability is better at high speed ball shear test. Keywords: ENEPIG, Ball shear test, High speed ball shear test.

碩士
國立臺灣科技大學
材料科技研究所
97
The BGA package is an important electronic connecting technology in electronic packaging industry. Due to the hurt of lead (Pb), the lead-free solders have become an important issue now. Sn-Ag-Cu (SAC) alloys are popular lead-free solders and widely use in electronic packaging industry, then Ni and Ge have been added into SAC solders in order to improve its wettability and oxidation resistivity. In the soldering process, because of the chemical potential gradient and the local equilibrium between solders and substrates, intermetallic compounds (IMCs) were formed at the interface. IMC formation can enhance bonding between the electronic device and substrate, but excessive growth of IMC can have detrimental effects on the long-term reliability of soldered points. However, the microelectronic industry is moving toward small size which requires local heating reflow methods like laser reflow. This study investigate the interfacial reactions and mechanical property between Sn-4.0Ag-0.5Cu (wt%) and Sn-4.0Ag-0.5Cu-0.05Ni-0.01Ge (wt%) lead free solders with Au/Ni(P)/Cu substrate by CO2 laser reflow. These results would compare with the same systems under a conventional hot-air reflowing method in the oven. After reflow, the samples were aged at 150℃ for up to 1000 hours. Under CO2 laser reflowing, mixtures of the (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 phases and (Ni, P, Cu) solid solution were formed at the interface. After taking a long period of heat-treatment, the (Cu,Ni)6Sn5 + (Ni,Cu)3Sn4 were still observed at the interface. But, the (Ni, P, Cu) solid solution disappeared as increasing reaction times. The experimental results compared with the same couples by conventional hot-air reflowing at 240℃, two layer structures, the (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 phases, were formed at the interface. The IMCs spalling off the interface could be observed in SACNG/Au/Ni/Cu reaction couple. In addition, the grain morphology of the IMC reaction couples by hot-air reflowing was a polyhedron-type structure. This is due to long solidification process providing the enough time to make the IMC grain grow and ripen. Because of rapidly solidification of alloys in the reaction couples by CO2 laser, elements did not have enough time to diffuse then to form distinct IMC grain. Thus, the indistinct IMC grains formed at the interface. The result indicated their grain morphology were strongly dependent on the reflowing methods. The mechanical property test indicated that the shear strength is independent to annealing time. The mechanical strength of solder joints by the laser reflowing technique is very similar to that by the hot-air reflowing method.

碩士
國立中興大學
化學工程學系所
102
The main trend for the world is looking for environmentally friendly material and saving energy in order to preserve the limited resources on Earth. Thermoelectric materials have the characteristic of converting heat and electricity back and forth, so it has already been widely used in our life. The good Z value (figure of merit) of bismuth telluride has made it the most popular choice in low temperature usage, but the concern is that the formation of intermetallic compound SnTe during the reaction of bismuth telluride with solder Sn will affect the electrical property and reliability. The problem can be solved by either adding some metals into the solder or electroplating a Ni diffusion barrier layer between solder and bismuth telluride in order to suppress the formation of intermetallic compound SnTe. This study investigates the interfacial reactions of three different solders (SAC105, SAC305, and LF35) with N (Bi2Te2.7Se0.3) type and P (Bi0.5Sb1.5Te3) type substrates. The experiment runs with different reflow times under the constant temperature of 250oC and obtains the relationship between reaction time and the thickness of intermetallic compound for further exploring the growth mechanism. The result shows the combination of N type substrate with LF35 solder has higher intermetallic compound thickness and the main diffusion elements are Bi and Te for forming SnTe and BiTe intermetallic compounds. On the other hand, P type substrate with SAC305 solder has the lowest intermetallic compound thickness and the main diffusion elements are Sb and Te for forming SnTe and SbSn intermetallic compounds. Hence, the kinetic n value can be derived from the thickness of intermetallic compound to assume the reaction mechanism.

碩士
中華大學
機械工程學系碩士在職專班
101
The continuous development of IC has the electronic components thin, compact and versatile which makes our lives more convenient. As one of the most important components in the electronics, solder ball can not only enable telecommunications but also strengthen its mechanical structure, therefore, the reliability of solder ball becomes a discussion topic of the researchers. This paper mainly discusses SAC305 lead-free solder ball in the fatigue life prediction of WLCSP package, and uses existing experimental data and finite element simulation results to deduce the fatigue life prediction equation for SAC305 Anand mode in the destruction indicator of accumulated plastic work density. In order to meet the demand of researchers lack of the finite element model analysis techniques for structural analysis to complete the common WLCSP package with the solder ball distribution of peripheral array or global array, the program code of ANSYS finite element model was created. Users can enter the desired analyzed geometry, while material parameters and thermal cyclic loading with a set of user-defined values can be amended by the designer at discretion. Both WLCSP packages were Module A with the solder ball distribution of peripheral array and a chip length of 6mm as well as Module B with the solder ball distribution of global array and a chip length of 8mm, respectively, and successfully carry out validation of the program code of ANSYS finite element model. Existing experimental data include the four different chip package thicknesses (400, 550, 715, 815 m) of thermal shock Module A and the chip package thickness (400 m) of thermal recycling Module B. Based on limited data and known from Schubert's solder ball failure mode analysis, the accumulated creep strain energy density range (W) and the accumulated von Mises creep strain range () for thermal cycle and third cycle of thermal shock of both WLCSP packages are respectively linear by taking logarithm; W and for different loads are parallel, showing good correlation. But Schubert's fatigue life prediction equation has errors of a certain degree, resulting from the difference in SAC305 solder ball characteristics. In the thermal shock loads, the experiment life and analysis results are treated with the least square linear regression method to get two fatigue life prediction modes for two different fatigue failure indices having a difference between life expectancy and experimental error of 8% or less. Thus deduce the life prediction mode for two different fatigue failure indices for thermal cycle loading, which can be used to predict the simulation experiment life. Finally by use of the above-mentioned simulation experiment life and the actual experiment life, in the Anand mode, the accumulated creep strain energy density range (W) is obtained, and also, the least square linear regression method is used to get the solder ball life prediction equation for thermal cycle and thermal shock, showing that there is a small error with the life expectancy. The author applied the above-mentioned solder ball life prediction equation to another WLCSP which is divided into a conventional standard design and new Ankor type design. The large difference between them is whether the copper post of solder ball is contact with green paints. After two packages were treated with thermal shock and thermal cycle analysis, the author found that there is also a small error between the actual experiment fatigue life and the simulation experiment fatigue life.

碩士
國立中央大學
化學工程與材料工程學系
101
This study investigates electromigration in Bi2Te3 thermoelectric (TE) material systems and the effectiveness of the diffusion barrier under current. The influences of the interfacial reaction by electromigration and Peltier effect were decoupled in this research. n- and p-type Bi2Te3 were connected to SAC305 solders and different current densities at various temperatures were applied. The Bi2Te3 samples were fabricated by the Spark Plasma Sintering (SPS) technique and electroless Ni-P was deposited at the solder/TE interfaces. The results elucidate the importance of the Ni diffusion barrier to the joint reliability. Different intermetallic compound (IMC) layers including (Cu, Ni)6Sn5 and NiTe formed at solder/Ni-P and Ni-P/substrate interfaces, respectively. The results show that the mechanism of compound growth was dominated by electromigration at low current density and dominated by Peltier effect at high current density.

碩士
國立中興大學
化學工程學系所
105
In the past decades, lead (Pb) has been questioned about its impact on the issues of environmental protection. Environmental experts continue to warn that Pb has harmful effects on human health. So, in the 70s and 80s, the United States and many other countries have legislated against the use of Pb paint in the building regulations. However, the rapid increase in the number of electronic waste products brings new urgent issue in the Pb usage. In response to this increasingly serious environmental problem, the European Union in 2003 announced the Restriction of Hazardous Substances (RoHS) directive. The RoHS became effective in July 2006, and since then the use of lead, mercury, and cadmium in the electronic products sold to the European market was prohibited. Lead has excellent electronic and mechanical properties, so it has been long-term widely used in semiconductor packaging and circuit boards. However, the impact of lead on the environment is questioned, coupled with the RoHS directive that banned lead, mercury and cadmium in the manufacturing of the electronic products. These new regulations push the semiconductor industry to overcome the problem caused by the increase of the reflow soldering temperature. Due to the high melting point of lead-free solder, the use of new solder components must withstand higher temperatures, while still ensuring product life and reliability. This study investigates the interfacial reactions of two different solders (SAC105 and LF35) with electroplated copper substrates. The experiment runs with 30 seconds reflow time under the constant temperature of 260 ℃ and the samples are placed into an oven at different temperatures (150 ℃ and 200 ℃) for different reaction times (24 h, 72 h, 144 h, 600 h, 1000 h). The mechanical strength of the solder/Cu samples is also investigated and compared.

碩士
國立成功大學
材料科學及工程學系碩博士班
98
Solder joints may be damaged by external force during using of electronic packaged products, so the mechanical strength of joints between the solder and the substrate is important to the reliability of electronic package. The aim of the study is to explore the effect of Pt addition on tensile strength of reflowed Cu/SAC305/Cu joints. The results show that the interfacial IMC layer phase of SAC305 changes from Cu6Sn5 into (Cu,Pt)6Sn5 after adding Pt into SAC305. The Pt addition can make the interfacial IMC layer grows uniformly, not like that of SAC305 growing faster in local. In the same reflow time, SAC305-xPt (0.03Pt and 0.05Pt) have the thicker interfacial IMC layer than SAC305, and the strength of joints is reduced by the Pt addition. Besides, as the reflow time increases (5 min to 60 min), the fracture location of SAC305 turns from the mixture of IMC-Solder zone to IMC zone. The fracture location of 0.03Pt exhibits Solder zone while the fracture location of 0.05Pt exhibits the mixture of IMC-Solder zone in both reflow time. Among the three types of fracture location, the fracture location which exhibits IMC zone corresponds to the highest joint strength. Comparing the microstructure of solder alloys with the tensile test data, the (Pt,Cu)Sn4 can be observed and the resistance to plastic deformation descends after adding Pt into SAC305. Therefore, adding Pt into SAC305 causes softening of the solder alloys and then makes the fracture location of solder joints moves from the interfacial IMC layer to the solder matrix.

碩士
國立成功大學
材料科學及工程學系
102
The lead-free solders of Sn-1Ag-0.5Cu (SAC105) and Sn-xNi (x = 0.2, 0.5, 1 wt.%) were used in photovoltaic (PV) ribbons in this study that included two parts. First, the properties of solders contained microstructure, melting point and mechanical properties. Second part, the applicability of solders in PV module assessed their applicability by peeling test and interface microstructure. In order to accelerate experiment with high current density, which simulated the actual application how the interface transition of IMC affected the volume resistance of PV modules. After the electric test with high current density for 72 hours, all of silver layer transformed into Ag3Sn in positive zone. The formation of (Cu,Ni)6Sn5 at Sn-1Ni/Cu interface was prevented the formation of Cu3Sn and retarded the growth of IMC during the electric test. Although the PV ribbon of Sn-1Ni could inhibit the growth of IMC, but the thickness of IMC formed was larger during dipping and reflowing process, so the PV module of Sn-1Ni was still high volume resistance after electric test for 72 hours. Therefore, the addition of low Ni content PV ribbons could inhibit the generation of Cu3Sn phase and the thinness of IMC formed at Solder/Cu interface, so the photovoltaic module of Sn-0.2Ni had the lowest volume resistance than other PV modules. In terms of cost and application considerations for the PV ribbons of Sn-0.2Ni had potential. Keywords: Sn-Ni, Sn-Ag-Cu, Photovoltaic module, IMC

碩士
國立中央大學
化學工程與材料工程學系
102
Surface finishes containing Co and Pd are new candidates for printed circuit boards. This study investigated the solid state interfacial reaction between Sn-3.0Ag-0.5Cu Pd-free solders and four different Co-based surface finishes, such as electroless Co (EC), electroless Co/immersion Au (ECIG), electroless Co/electroless Pd (ECEP), and electroless Co/electroless Pd/immersion Au (ECEPIG). The results showed that the thickness of the total intermetallic compound thickness could be affected by the spalling and the growth of the compounds in four different Co-based surface finishes. (Co,Cu)6Sn5 and (Co,Cu,Pd)6Sn5 would form at the interfaces between the solder and (Co,Cu)Sn3 or (Co,Cu,Pd)Sn3. Prolonging the aging time or raising the aging temperature would result in the increase of the (Co,Cu)6Sn5 and (Co,Cu,Pd)6Sn5.

碩士
國立成功大學
材料科學及工程學系碩博士班
97
The formation of intermetallic compounds (IMCs) helps to provide good metallurgical bonding between solders and substrate in the microelectronic packing applications. Previous reports pointed out that the tensile stress is a main cause induces the fracture of solder joints during the Ball Pull tests. Owing to the above-mentioned reasons, this study attempts to find out an optimal interfacial IMCs growing condition between SAC305 and copper substrate through performing the solid-state bonding process with 210�薡 IMCs growth treatments and different time (5, 7.5, 9, 10, 15, 20 hrs). The variation of interfacial adhesion strength, bonding reliability and failure behaviors were examined. Tensile tests were applied to measure the interfacial adhesive strength of SAC305/Cu bonding. The tensile test results have obvious difference with different IMCs growth treatment time. With 7.5~10 hrs IMCs growth treatment, average adhesive strength are around 20MPa and much higher than others. Besides, the results of Weibull analysis of 7.5, 9, 10 hrs show the adhesive strength and the bonding reliability are decreased with increasing heating time, and 7.5 hrs specimens has the highest characteristic strength of SAC305/Cu interfacial bonding, less data fluctuation and a left-shift wear-out failure model of increasing failure rate (IFR). As the result, the optimal IMCs growing condition is 7.5 hrs. From the cross-sectional observation of SEM and Weibull model, the cracks propagate through the Cu6Sn5 IMCs layer can help reliability and adhesive strength increase. Besides, according to the results of EPMA analysis, the forming of Ag3Sn at the interface of SAC305/Cu is propagate with IMCs growth treatment time and it may be one of the reasons that average adhesive strength is decease with IMCs growth treatment time.