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The purpose of this paper is to study the effect of conformal coating on the thermal cycling reliability of anisotropically conductive adhesive film (ACF) joined flip chip components on FR‐4 and polyimide (PI) substrates.

Test chips were joined using flip chip technology and an anisotropically conductive adhesive. The conformal coating used was parylene C and it was applied using the vapour deposition polymerisation method. The reliability of ACF joined flip chip components on FR‐4 and PI substrates was evaluated using −40/+85°C thermal cycling testing. Test lots with and without parylene C coating were studied. Additionally, one test lot with initial moisture inside the coating layer and a PI substrate was subjected to the test. The reliability results were analyzed using Weibull analysis and failure analysis was performed to study the failure mechanisms using cross sectioning and optical and scanning electron microscopy.

The results show a clear difference between the FR‐4 and PI substrate materials. PI substrate material proved to be reliable enough to withstand the thermal cycling testing. Two different occurrences of the first failures are seen and analyzed with FR‐4 substrates. The conformal coating layer did not seem to impair the reliability. Parylene C coating proved to be a reliable choice to protect, and even improve, the thermal cycling reliability of flip chip devices.

Usually, conformal coatings are studied in humidity tests. However, it is also vital to know whether the conformal coatings affect the reliability in thermal cycling and there is a lack of reliability studies in this area. This paper gives reliability data for conformal coating users about the influence of thermal cycling.

Thermal insulation is important to achieve energy efficiency in a buildings’ lifespan while maintaining comfort. Traditionally, the majority of insulation in buildings is man-made petroleum based products with limited or no-end life usage. However, from an environmental and economic sustainability perspective, they are not sustainable as natural resources are finite and in danger of run-out. Furthermore, they are also highly influenced by the increasing price and the ongoing scarcity of fossil fuel oils. The paper aims to discuss these issues.

This paper introduces soap based insulation from recycled materials as a sustainable alternative to petroleum counterparts. The methodology is lab based experimentation and iterative tests. The phased based research process for the incremental development of the soap based thermal insulation is explained.

Findings reveal that soap based insulation can be one possible way forward in the quest for natural and sustainable thermal insulation from recycled products to preserve and conserve the sustainable environment.

Thus, the paper provides a unique environmentally friendly approach as an alternative to those existing petroleum counterparts for thermal insulation in buildings.

Thermal issues are becoming increasingly serious with the scaling down of integrated circuits and the increasing density brought in by advanced packaging techniques. Consequently, thermal issues need to be considered during both design and test. The present paper addresses thermal testing, and more specifically thermal transient testing.

The purpose of this work is to undertake a comparison of accelerated test regimes for assessing the reliability of solder joints, in particular those made using lead‐free solders.

Identical samples of 1206, 0805 and 0603 resistors were subjected to six different cycling regimes to investigate the effect of thermal excursions, ramp rates and temperature dwells.

The most damage to joints was found to be caused by thermal cycling between −55 and 125°C, with a 10°C/min ramp rate and 5 min dwells. Large thermal excursions were shown to give faster results without compromising the failure mode.

Similar degrees of damage in the lead‐free solder joints were experienced from thermal shock regimes with ramp rates in excess of 50°C/min. However, these regimes, although faster to undertake, appeared to cause different crack propagation modes than observed with the thermal cycling regimes. However, these differences may be small and thermal shock testing may still be used to differentiate between, or enable ranking of, the effects of changes to materials or processes on the reliability of the solder joints. Hence, it is envisaged that if a wide range of conditions are to be tested a first sift can be completed using thermal shock, with the final work using typical thermal cycling conditions.

The difference between the SAC (95.5Sn3.8Ag0.7Cu) and SnAg (96.5Sn3.5Ag) solder alloy results across all types of cycles showed very little difference in the rates of joint degradation.

This paper compares relative reliability (remaining shear strength) of three chip components soldered with two lead‐free alloys based on various thermal cycling conditions.

This article comprises Chapter 6 from the recently published book ‘An Engineer’s Guide to Flexible Circuit Technology by J. Fjelstad

The purpose of this paper is to deal with performance verification of thermal insulation fillings that are used for outer clothes into cold environments. Thermal properties of filling materials (down and three sophisticated fillings) were tested under condition approaching real weather conditions in Middle Europe.

In the paper, modern method of thermal resistance Rct measurement, by Sweating Guarded-Hotplate system, was compared with method of Technical University of Liberec (TUL method). The TUL method shows good results and it is applicable even at ambient temperatures below zero, which fully corresponds to real application of the insulation filling.

Evaluation of fibre battings were carried out even at temperatures below the freezing point, which is important for simulation of actual application of these filling structures. The highest thermal resistance of goose down confirm that natural materials have their irreplaceable position, especially in application into clothes for extreme conditions.

There does not include effect of the humidity change on thermal insulation properties. It will be subject of further research of authors.

The investigation of thermal insulation properties were carried out under conditions approaching real application of tested materials, namely, at low ambient temperature.

The mechanical integrity of solder joint interconnects in PWB assemblies with micro ‐ BGA, chip scale, and LGA packages are being questioned as the size and pitch decrease. Three‐point cyclic bend testing provides a useful tool for characterizing the expected mechanical cycling fatigue reliability of PWB assemblies. Cyclic bend testing is useful for characterizing bending issues in electronic assemblies such as repetitive keypad actuation in cell phone products. This paper presents the results of three‐point bend testing of PWB assemblies with fine pitch packages. The methodology of materials analyses of the metallurgy of solder interconnects following mechanical bending and thermal cycle testing is described.

In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In Part 2, mechanisms of damage and degradation of components and soldered joints during soldering, transport and field life have been discussed, the most important mechanism being low cycle fatigue of the solder metal. In this third part, the determination of the fatigue life expectancy of soldered joints is discussed. Accelerated testing of fatigue is needed, as the possibilities of calculations are strongly limited. A temperature cycle test under specified conditions is proposed as a standard. A model is worked out for the determination of the acceleration factor of this test. A compilation of a number of solder fatigue test results, generated in the author's company, is presented.

The purpose of this paper is to examine the long-term reliability of an anisotropic conductive adhesive (ACA) attached polyethylene terephthalate (PET) flex-on-board (FOB) assembly for industrial application used in harsh environments. In addition, the possibility of reducing reliability testing time was studied.

A−40/+125°C thermal cycling test with 5- and 14-minute soak times was used to study the reliability. To study the functionality of the FOB assembly during testing, a real-time resistance measurement was used together with a 90° peel strength test. Failure analysis was performed on samples using scanning electron microscopy and cross sectioning.

No failures or noticeable increase in the measured resistance values were seen during testing. The peel strength, however, decreased significantly with both soak times used. The highest drop in the mechanical strength occurred at the start of the temperature cycling tests. The time spent at the high temperature extreme seemed to have a greater impact on the peel strength than the number of temperature cycles. The failure mode of peel tested samples changed due to temperature cycling from interfacial delamination to cohesive failure. The temperature cycling was also observed to induce voiding inside the adhesive.

The paper illustrates the applicability of ACA attached PET flex in high reliability industrial applications. Additionally, testing methods for high reliability adhesive interconnections are discussed. Especially, the effect of temperature cycling soak time on peel test results and reliability testing time is studied.

This paper's purpose is to review the design of a flip chip thermal test vehicle.

Design requirements for different applications such as thermal characterization, assembly process optimization, and product burn‐in simulation are outlined and the design processes of different thermal test chip structures including the temperature sensor and passive heaters are described in detail. The design of fireball heater, a novel test chip structure used for evaluating the effectiveness of heat spreading of advanced thermal solutions, is also explained.

Describes the design considerations and processes of the package substrate and printed‐circuit board with special emphasis on the physical routing of the thermal test chip structures. These design processes are supported with thermal data from various finite‐element analyses carried out to evaluate the capability and limitations of thermal test vehicle design.

The validation and calibration procedures of a thermal test vehicle are presented in this paper.