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The purpose of this paper is to investigate the laser soldering of fine pitch quad flat package (QFP) devices using lead‐free solders and solder joint reliability during thermal cycling.

QFP devices were selected as the test vehicles and were soldered with four alloy types, Sn37Pb, Sn3.5Ag, Sn3.8Ag0.7Cu and Sn3.8Ag0.7Cu0.03Ce. The experimental samples were QFP‐256 devices with lead‐free solder paste on the printed circuit boards. The packages were dried for 24 h at 125°C prior to reflow soldering. Soldering experiments on the QFP devices were carried out with an infrared (IR) reflow soldering oven and a diode laser (DL) soldering system. Reflow soldering was performed at peak temperatures of 210°C (SnPb), 240°C (SnAgCu and SnAgCuCe) and 250°C (SnAg), as determined on the boards. Pull testing was adopted to evaluate the tensile strength of the four solders using an STR–1000 micro‐joint strength tester.

The tensile force of the QFP micro‐joints increased as laser intensity increased when it was less than an “optimal” value. The maximum tensile force of the QFP micro‐joints was gained when the laser intensity had increased to 2,165, 2,127, 2,165 and 2,064 W/cm², depending on the alloy used. The thermal fatigue performance of three lead‐free solder joints, SnAgCuCe, SnAgCu and SnAg, was determined to be superior to that of the eutectic SnPb alloy. After soldering without thermal cycling tests, the fracture morphology of soldered joints exhibited characteristic toughness fracture with both of the soldering methods. After 700 thermal cycles, the fracture mechanism was also toughness fracture, nevertheless, the dimples became large. The fracture morphology of the soldered joints subjected to 1,500 thermal cycles indicated brittle intergranular fracture on the fracture surface and no intense plastic deformation appeared before fracture with IR soldering. For DL soldering, the pull fracture model of the SnAgCuCe was completely ductile in the soldered joint with 1,500 thermal cycles.

The paper usefully investigates the influence of laser intensity on the tensile strength of different soldered joints and the solder joint reliability during thermal cycling.

Over the past few decades, several base isolation systems have been developed to enhance the performance of structures under extreme earthquake shaking intensities. Recently, to achieve high energy dissipation capabilities, a new generation of multi-stage friction pendulum (FP) bearings known as the “Quintuple Friction Pendulum (QFP)” was introduced in the literature. With the help of its five effective pendula and nine operational regimes, this bearing's major benefits stem from its ability to accomplish complicated multi-stage adaptive behavior with smoothed loading and unloading when subjected to lateral forces.

Within the assessment context, five finite element models of reinforced concrete frames supported on QFP isolators with different properties will be developed in OpenSees. Thereafter, a set of 60 earthquakes will be analyzed using the nonlinear time history analysis approach, and the impact of each ground motion record's properties will be evaluated.

Overall, the study's findings have demonstrated that the characteristics of the isolator, combined with the type of earthquake being applied, have a substantial impact on the isolator's behavior.

Currently, no studies have examined the energy distribution of structural systems equipped with this type of isolation system while considering the influence of earthquake characteristics. Thus, this study is intended to extend the findings available in the literature by discussing and illustrating the distribution of strong ground motions input energy into highly nonlinear base-isolated systems that account for the bearing and superstructural materials' nonlinearity, geometric nonlinearity and leakage-prevented viscous damping nonlinearity. Besides, it investigates the influence of various earthquake characteristics on the energy dissipation of such buildings.

The reliability of 0.4 mm pitch, 28 mm body size, 256‐pin plastic quad flat pack (QFP) no‐clean and water‐clean solder joints has been studied by temperature cycling and analytical analysis. The temperature cycling test was run non‐stop for more than 6 months, and the results have been presented as a Weibull distribution. A unique temperature cycling profile has been developed based on the calculated lead stiffness, elastic and creep strains in the solder joint, and solder data. Also, the thermal fatigue life of the solder joints has been estimated and correlated with experimental results. Furthermore, a failure analysis of the solder joints has been performed using scanning electron microscopy (SEM). Finally, a quantitative comparison between the no‐clean and water‐clean QFP solder joints has been presented.

The purpose of this paper is to describe the board level reliability test results of four IC packages with lead‐free balls/platings, soldered with lead‐free solder paste, during thermal cycling. The board level reliability test results of tin‐lead balled/plated packages soldered with lead‐free solder paste have also been included for comparison.

Four different packages, i.e. ball grid array (BGA), chip scale package (CSP), quad flat package (QFP) and thin small outline package (TSOP), were assembled on a test printed circuit board (PCB) as the test vehicle. Lead‐free and tin‐lead BGA/CSP packages were equipped with Sn‐3.0Ag‐0.5Cu and Sn‐37Pb solder balls, respectively. The lead‐frames of lead‐free QFP/TSOP leaded‐packages were plated with Sn‐58Bi and those of tin‐lead QFP/TSOP leaded‐packages, Sn‐37Pb. The lead‐free solder paste used in this study was Sn‐3.0Ag‐0.5Cu. Two kinds of surface finishes, immersion gold over electroless nickel (Au/Ni) and organic solderability preservative, were used on the PCBs. The test PCBs were thermal cycled 5,000 times within the temperature range of −40 to 125°C and electrically monitored during the thermal cycling.

It was found that the tin‐lead balled/plated BGAs, CSPs, QFPs and TSOPs soldered with lead‐free solder paste showed serious board level reliability risks as their abilities to withstand thermal cycling stresses are much weaker than those of entirely lead‐free assemblies. Neither package nor surface finish was found to have any effects on the board level reliability of test vehicles with lead‐free balled/plated BGAs, CSPs, QFPs and TSOPs. Metallographic examinations were conducted to investigate the effect of thermal cycling on the failure modes of solder joints.

The paper is of value by contributing to research in the use of lead‐free solder paste with lead‐containing packages in the industry. Currently, there is a deficiency of knowledge in this area.

The purpose of the work is to investigate the feasibility of using anisotropically conductive adhesives to join surface‐mount devices as solder replacement. The results from a literature and market survey are reported. Based on industrial demands, two anisotropically conductive adhesives were chosen for the experimental work. During the experimental work, the conductive adhesive joints were produced at various curing conditions. The joints were characterised by shear testing and electrical resistance measurement after ageing at 20, 70 and 120°C to 1000 hours. Optical and scanning electron microscopy were used to characterise the adhesive joints. In addition to this, temperature cycling tests, humidity test and pull tensile tests were used to qualify the adhesive joint reliability and quality. From the results of the present work, it can be concluded that the anisotropically conductive adhesive A joints are stable in the 85°C/85% RH environment and therefore have better corrosion resistance than adhesive B joints. Neither of the adhesives can pass temperature cycling from −55 to 125°C for 1000 cycles according to military standard 883C.

Rapid feedback on the effect of changes in materials or assembly process parameters on solder joint quality is essential in process optimisation for fine pitch surface mount solder assembly. This is particularly the case where the demands of high volume production do not allow lengthy experimentation to be carried out on the production line. The greater precision and care required in analysis of fine pitch solder joints places a further constraint on the speed at which the analysis can be carried out. The techniques of microstructural analysis, solder joint mechanical strength testing and short duration environmental stress testing must be used to meet a rapid turnaround quality and reliability analysis requirement and to maximise the amount of information obtained from each stage of the analysis. Three case studies are detailed which demonstrate the use of these techniques in a high volume production context to provide rapid feedback on joint quality. The case studies have been selected for presentation not only to demonstrate the analysis techniques but also because they address issues which are of current interest due to the increased usage of fine pitch packages in production and the constraints on the use of solvents for cleaning of circuit boards. The studies are:

Solvent‐clean and no‐clean mass reflow processes of 0.4 mm pitch, 28 mm body size, 256‐pin fine pitch quad flat packs (QFPs) are presented. Emphasis is placed on fine pitch parameters such as printed circuit board (PCB) design, solder paste selection, stencil design, printing technology, component placement, mass reflow, cleaning and inspection. Furthermore, cross‐sections of component/PCB assemblies from both processes have been thoroughly studied using scanning electron microscopy (SEM).

This paper aims to detail the qualification of alternative substrate materials and reliability aspects for quad flat no lead (QFN) packages for highly stressed electronic devices, e.g. for use in automotive applications.

Detailed information is given on the advanced climatic and mechanical requirements that electronic devices have to withstand during life cycle testing to qualify for the automotive industry. Studies on the suitability of high‐temperature thermoplastics as substrate materials for printed circuit boards and the qualification of QFN packages for advanced requirements are described. In addition, information on cause‐effect relationships between thermal and vibration testing are given.

With respect to adhesion of metallization on high‐temperature thermoplastics and the long‐term stability of the solder joints, these substrate materials offer potential for use in electronic devices for advanced requirements. In addition, the long‐term stability of the solder joints of QFN packages depends on the design of the landings on the PCB and the separation process of the components during manufacturing.

The paper covers only a selection of possible high‐temperature thermoplastic materials that can be used in electronics production. Also, this paper has a focus on the new packaging type, QFN, in the context of qualification and automotive standards.

The paper details the requirements electronic devices have to meet to be qualified for the automotive industry. Therefore, this contribution has its value in giving information on possible substrate alternatives and the suitability for the usage of QFN components for highly stressed electronic devices.

This paper describes the influence of soldering parameters on solder joint quality and reliability of 0.65 mm pitch QFP technology. Soldering process parameters such as soldering temperature, conveyor speed and board size have systematically been varied using factorial experimental analysis. Solder joint quality has been characterised in terms of solder ball formation, open joints and porosity behaviour. Equipment used includes microfocus X‐ray non‐destructive testing apparatus, optical and scanning electron microscope. The reliability of solder joints has been investigated by temperature cycling from −55 to + 125°C for 1000 cycles. The time per cycle was approximately 1 hour. The results from the present work show that pad layout on the printed circuit board (PCB) and the quality of pretinning during PCB production have a considerable influence on the solder joint yield. No failures have been observed during temperature cycling. This indicates that 0.65 mm (25 mil) pitch QFP components have very high reliability in respect of temperature cycling and are extremely compliant for absorbing the thermal stress developed during temperature cycling.