Influence of Multiple Reflows and Surface Finishes on Solder Joint Resistivity (original) (raw)
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Comparative Study on the Effect of Surface Finish on Mechanical Properties of Solder Joints
2023 46th International Spring Seminar on Electronics Technology (ISSE), 2023
We present the results of an experimental study comparing the effect of PCB surface finishes on the mechanical properties of soldered joints: maximum strength, strain hardening area, necking area (tendency to brittle failure), and energy consumed to break the joint. For the study, 4 types of standard PCB surface finishes were used, which we compare with various non-standard SnAg-based surface finishes. The measurements were carried out through shear tests. Failure mode, strength and fracture energy data, and analysis of the strain hardening area of brittle failure or necking were supplemented by microscopic SEM analyses of surfaces after failure. Our results show the influence of the surface finish type on the joints' quality and reliability when applying SAC 305 solder after one and 5 reflows. Our previous analyzes showed that the SnAg5 surface finish had demonstrably better wettability. Still, a comparative study of the surface finish's effect on the joints' mechanical properties showed that the SnAg7 surface finish shows better properties even after repeated reflow processes. In both cases, the SnAg surface finish group has comparable properties to the ENIG finish.
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.
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...
Effect of surface finish on the wettability and electrical resistivity of Sn-3.0Ag-0.5Cu solder
IOP Conference Series: Materials Science and Engineering, 2019
The effect of different surface finish with Sn-3.0Ag-0.5Cu (SAC305) solder was successfully investigated. The SAC305 solder was fabricated by using casting method and solder was placed on copper substrate that coated with different surface finish. The soldering process was carried out by using F4N reflow oven followed up with the mounted and metallographic steps. Wettability of SAC305 solder was observed through contact angle formed between solder and four different surface finish located on the copper substrate. Subsequently, the electrical resistivity of solder was studied by conducted the four-point probes. The results of wettability test was found to be in the accepted range which is below 45° for all different surface finish. In terms of electrical resistivity, the results showed that the ImAg surface finish had enhanced the electrical conductivity of SAC305 lead-free solder.
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
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.
Influence of intermetallic compounds growth on properties of lead-free solder joints
2012 35th International Spring Seminar on Electronics Technology, 2012
influence of these IMCs on properties of soldered joints. The test specimens of printed circuit boards (PCBs) with different surface finishes were made for this experiment. Tin_G (galvanic tin), Tin_C (immersion tin), Cu (pure copper), OSP (organic solderability preservative) and ENIG (electroless nickel immersion gold) surface finishes were chosen. The soldered joints were created on the test specimens by reflow soldering process concretely vapour-phase soldering. The surface mount solder joints of LCCC resistor of size 1206 were studied. Two lead-free solder paste and one tin-lead solder paste were chosen for research of IMCs and their influence on properties of soldered joints. The test specimens were exposed to elevated aging for research of IMCs growth in solder joint. The specimens were thermal stressed in hot air oven at the temperature of 150°C for a periods of 0, 1, 2, 4, 8, and 16 days. The shear test was used for research of IMCs growth influence on strength of soldered joints. The results of analysis of IMCs in solder joints using confocal and metallographic microscopes and the results of shear strength measurement will be presented in this article.
Surface finish effect on reliability of SAC 305 soldered chip resistors
Soldering and Surface Mount Technology
Purpose ‐ The purpose of this paper is to assess the long-term reliability of lead-free Sn96.5Ag3.0Cu0.5 (SAC305) under accelerated temperature cycling (ATC) conditions. Test vehicles consisted of commercial 2512 ceramic chip resistors soldered to printed circuit boards (PCBs) using three different Pb-free surface finishes: organic solderability preservative (OSP), immersion silver (IAg) and electroless nickel immersion gold (ENIG). Design/methodology/approach ‐ Two populations of solder joints were monitored continuously during a thermal cycle of 0°C to 100°C with a ramp rate of 10°C/min and a 30?min dwell at the temperature extremes. One population was cycled to 2,500 cycles, the other population was cycled to 8,250 cycles. Failures were defined in accordance with the IPC-9701A industry test guidelines and failure data are reported as characteristic life, ?. Microstructural evolution was characterised using metallographic techniques and back-scattered scanning electron microscopy ...
Solder joints properties assessment in the terms of 4P Soldering Model
2011 IEEE 17th International Symposium for Design and Technology in Electronic Packaging (SIITME), 2011
The challenges for the companies involved in conception, development and/or manufacturing of electronic products are the lead-free technology with its increased melting temperature of the solder alloy and trend to reduce the solder materials cost by usage of lead-free solder pastes with low silver content. Defining the elements Pad-Paste-Pin-Process as Key Process Input Variables (KPIV) in terms of 4P Soldering Model concept [1, 3], the solder joints are result of KPIV synergistically interactions and correlations, with consequences over their microstructure. In the paper, taking into consideration the cooling rate influence over intermetallic compounds formation and microstructure, are presented the investigations over electrical, and mechanical properties of solder joints resulted from Vapour Phase Soldering (VPS) process in terms of 4P Soldering Model. Maintaining PAD and PIN of KPIV as references were study the solder joints properties determined by PASTEs as function of cooling rate parameters of VPS PROCESS. The results of the studies performed and presented in the paper will be used for improving process control in order to minimize losses on VPS lines, to reduce defects numbers and rework time in order to achieve “zero defects production”.
2017
Soldering technology has made tremendous strides in the past halfcentury. Whether structural or electronic, all solder joints must provide a level of reliability that is required by the application. This Part 1 report examines the effects of filler metal properties and the soldering process on joint reliability. Solder alloy composition must have the appro priate melting and mechanical properties that suit the product’s assembly process(es) and use environment. The filler metal must also optimize solderability (wetting and spreading) to realize the proper joint geometry. The soldering process also affects joint reliability. The choice of flux and thermal profile support the solderability performance of the molten filler metal to successfully fill the joint clearance and complete the fillet. Base material and/or surface finish dissolution can alter the filler metal composition, which together with the interface reaction, affect the longterm mechanical performance of the solder joi...