Comparative Study on the Effect of Surface Finish on Mechanical Properties of Solder Joints (original) (raw)
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Circuit World, 1999
An overview has been presented on the topic of alternative surface finishes for package I/Os and circuit board features. Aspects of processability and solder joint reliability were described for the following coatings: baseline hot‐dipped, plated, and plated‐and‐fused 100Sn and Sn‐Pb coatings; Ni/Au; Pd, Ni/Pd, and Ni/Pd/Au finishes; and the recently marketed immersion Ag coatings. The Ni/Au coatings appear to provide the all‐around best options in terms of solderability protection and wire bondability. Nickel/Pd finishes offer a slightly reduced level of performance in these areas which is most likely due to variable Pd surface conditions. It is necessary to minimize dissolved Au or Pd contents in the solder material to prevent solder joint embrittlement. Ancillary aspects that include thickness measurement techniques; the importance of finish compatibility with conformal coatings and conductive adhesives; and the need for alternative finishes for the processing of non‐Pb bearing s...
IEEE Transactions on Reliability, 2016
Reliability specifications for solder joints, as well as for all electronic components, have become a fundamental feature in the qualification of an electronic product. The relevance of these reliability features increases if new components or materials are considered. In this research activity, an accelerated thermal test on customized electronic boards was implemented for an early reliability evaluation; we therefore proposed a study on the reliability behavior of a solder joint by considering different surface finishes, and several component packages. A comparative study was carried out through the application of statistical methods. To this end, Weibull distributed data and non-linear mixed models were evaluated. More precisely, Weibull random-effects models were applied to compare different combinations of surface finishes, (e.g. Hot Air Solder Leveling, Electroless Nickel Immersion Gold, Immersion Tin) and alloys, (e.g. tin-silver-copper, tin-lead), connected to four types of components, also to evaluate how the type of package or the geometry of the joint may affect the reliability of the soldering. Therefore, the aim of this research is a statistical study of the reliability of solder alloys subjected to thermal aging tests by also taking different surface finishes of the printed circuit boards and different types of packaging into account. The study was carried out with two-by-two comparisons of alloy-surface finishes. By evaluating the statistical results, the tin-silver-copper alloy, with the considered finishes, demonstrates a higher reliability with respect to the boards soldered by the traditional combination of soldering alloy and surface finish.
Influence of Multiple Reflows and Surface Finishes on Solder Joint Resistivity
Acta Electrotechnica et Informatica, 2021
The main purpose of this paper is the analysis of the electrical resistivity of solder joints depending on various surface finishes and on the number of reflow processes. The electrical resistivity was determined after 1, 2, 3, 5 and 6 reflow cycles as a replacement for the basic accelerated aging test. In this article, various surface finishes are compared by measuring electrical resistivity of solder joints between two soldering pads. The influence of standard surface finishes (ENIG, Lead HASL, Lead-free HASL, Cu, ImSn) with the new developed surface finish based on SnAg7 is also compared. Measurements show that the electrical resistivity is dependent on surface finish type and the thickness of the solder joint. The results prove that the new developed surface finish based on SnAg7 is stable against multiple reflows and comparable to the surface finish based on Au. The new developed surface finish based on SnAg7 can be recommended as a replacement for other conventional surface fi...
Materials, 2014
The significant increase in metal costs has forced the electronics industry to provide new materials and methods to reduce costs, while maintaining customers' high-quality expectations. This paper considers the problem of most electronic industries in reducing costly materials, by introducing a solder paste with alloy composition tin 98.3%, silver 0.3%, and copper 0.7%, used for the construction of the surface mount fine-pitch component on a Printing Wiring Board (PWB). The reliability of the solder joint between electronic components and PWB is evaluated through the dynamic characteristic test, thermal shock test, and Taguchi method after the printing process. After experimenting with the dynamic characteristic test and thermal shock test with 20 boards, the solder paste was still able to provide a high-quality solder joint. In particular, the Taguchi method is used to determine the optimal control parameters and noise factors of the Solder Printer (SP) machine, that affects solder volume and solder height. The control parameters include table separation distance, squeegee speed, squeegee pressure, and table speed of the SP machine. The result shows that the most significant parameter for the solder volume is squeegee pressure (2.0 mm), and the solder height is the table speed of the SP machine (2.5 mm/s).
The trend of miniaturization, light weight, high speed and multifunction are common in electronic assemblies, especially, for portable electronic products. In particular, board-level solder joint reliability, in term of both mechanical (e.g., drop impact) and thermo-mechanical (e.g., thermal cycling) loads is of great concern for portable electronic products. The transition to lead-free solder happened to coincide with a dramatic increase in portable electronic products. SnAg -Cu (SAC) is now recognized as the standard lead-free solder alloy for packaging interconnects in the electronics industry. Hence, this study review the reliability of board-level SAC solders joints when subjected to drop impact and thermal cycling loading conditions from the viewpoints of mechanical and micro-structural properties of the bulk solder. The finding presented in this study indicates that the best SAC composition for drop performance is not necessarily the best composition for optimum thermal cycling reliability, thus the SAC solder alloys are limited in their potential applications in the electronic industries. This contribution has its value in giving information on possible developments and the suitability for the usage of SAC solder in portable electronic devices.
Solder Joint Reliability of SnAgCu Solder Refinished Components Under Temperature Cycling Test
… , IEEE Transactions on, 2011
SnAgCu (SAC) solder is being offered as a leadfree termination finish. SAC finish is obtained by dipping the terminals of components into molten SAC solder. However, the reliability of solder joints formed with SAC solder refinished components needs to be determined in order to evaluate the effects of the SAC solder refinishing process. In this paper, the strength of solder joints with SAC solder refinished thin small outline packages (TSOPs) was evaluated by the shear test. The reliability of solder joints formed with SAC solder refinished components, including TSOPs and resistors, was evaluated by a temperature cycling test. Original Sn finished components were used as a baseline for comparison. It was found that SAC solder refinishing increased solder joint strength. SAC solder refinishing decreased the fatigue life of solder joints of TSOPs and increased the fatigue life of resistors under temperature cycling conditions.
Factors affecting wettability and bond strength of solder joint couples
Pure and Applied Chemistry, 2000
The paper discusses the scientific understanding of the role of interfacial phenomena in joining of dissimilar materials using liquid-phase-assisted processes. From the example of the Sn-alloy/Cu system, it is demonstrated that interaction in the liquid solder/substrate couples is accompanied by a number of complex interfacial reactions leading to significant changes in the structure and chemistry of interfaces (solder/substrate, solder/environment, substrate/environment) and remaining solder layer that finally influence the mechanical properties of solder joints.
Effect of Solder Volume on Interfacial Reaction between SAC405 Solders and EN(B)EPIG Surface Finish
Advanced Materials Research, 2013
ABSTRACT The electronic packaging industry is now being driven towards smaller, lighter, and thinner electronic products but with higher performance and more functions. Thus, smaller solder ball sizes are needed for fine solder joint interconnections to fulfill these requirements. This study investigates the interfacial reactions during reflow soldering and isothermal aging between Sn-4.0Ag-0.5Cu (SAC405) and electroless nickel (boron)/ immersion palladium/immersion gold (EN(B)EPIG). Reliability of solder joint has also been investigated by performing solid state isothermal aging at 125 °C for up to 2000 hours. The results revealed that after reflow soldering, (Cu, Ni)6Sn5 IMC is formed between solder and substrate while after aging treatment another IMC was found between (Cu, Ni)6Sn5 and substrate known as (Ni, Cu)3Sn4. Aging time of solder joints resulted in an increase in IMC thickness and a change in morphology into more spherical, dense and with larger grain size. By using optical microscope, the average thickness of the intermetallics was measured and it found that the larger solder balls produced thicker IMC than the smaller solder balls during reflow soldering. However, after aging the smaller solders produced thicker IMC than the larger solders.
2009 59th Electronic Components and Technology Conference, 2009
The transition from tin-lead to lead free soldering in the electronics manufacturing industry has been in progress for the past 10 years. In the interim period before lead free assemblies are uniformly accepted, mixed formulation solder joints are becoming commonplace in electronic assemblies. For example, area array components (BGA/CSP) are frequently available only with lead free Sn-Ag-Cu (SAC) solder balls. Such parts are often assembled to printed circuit boards using traditional 63Sn-37Pb solder paste. The resulting solder joints contain unusual quaternary alloys of Sn, Ag, Cu, and Pb. In addition, the alloy composition can vary across the solder joint based on the paste to ball solder volumes and the reflow profile utilized. The mechanical and physical properties of such Sn-Ag-Cu-Pb alloys have not been explored extensively in the literature. In addition, the reliability of mixed formulation solder joints is poorly understood.
Forward and Backward Compatibility of Solder Alloys With Component and Board Finishes
IEEE Transactions on Electronics Packaging Manufacturing, 2007
The primary objective of the research presented in this paper is to qualify the reliability of mixed assemblies by comparing them to the conventional Sn-Pb assembly and completely Pb-free assembly. The research investigates both forward and backward compatibility in electronic assemblies using a design of experiments (DOE) approach. The investigation utilized a test vehicle containing an area array component (BGA169) and chip components (0603 resistors). Hot air solder leveling (HASL) and organic solderability preservative (OSP) surface finishes were used on the test vehicles to represent Sn-Pb and Pb-free alternatives, respectively. The assembled test vehicles were cut into two panels-one containing a resistor section for isothermal aging and the other containing a BGA and another resistor section for thermal shock. The assemblies were subjected to isothermal aging and thermal shock tests as per Interconnecting and Packaging Electronic Circuits/Joint Electronic Device Engineering Council (IPC/JEDEC) standards. The resistors were sheared in the "as-soldered" condition, and at various isothermal aging intervals and thermal shock cycles. In order to simulate an intermetallic failure in isothermal aging, a reduced shear height (20 m) was used for the shear test. The performance of the resistor solder joints were quantified in terms of the shear force. The performance of the ball grid array (BGA) solder joint during thermal shock testing was quantified in terms of the number of cycles to failure. Experimental results from shear analysis of resistor solder joints show that Pb-free alloy assemblies' performance is superior to those assembled using Sn-Pb alloy. Also, the ductile nature of the SnAg -Cu (SAC) alloy provides the joints a better fatigue life. With the area array components, Pb-free assembly joints outlived the traditional Sn-Pb joints when subjected to thermal shock loading. Among the mixed assemblies, backward-compatible assemblies (Pb-free bumps and Sn-Pb solder alloy) showed superior performance. The microstructural analysis of the solder joints indicate a uniform distribution of lead in the solder joint matrix Index Terms-Compatibility, lead-free, reliability, shear test, thermal aging, thermal shock. I. INTRODUCTION T RANSITION to Pb-free has necessitated the requirement for research on the reliability of mixed assemblies. Mixed assemblies are bound to be used during the transition period and