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An electronic assembly may consist of a printed circuit and various types of electrical components. Soldering to make the electrical/mechanical connection is a critical process. Both printed circuit and component leads must promote acceptable solder wetting if high reliability is to be obtained. Bulk purchasing of these items can lead to long periods of storage often in poor conditions. This paper describes some of the work which simulates storage conditions by accelerated ageing so that a prediction can be made as to whether solderability will be affected. Due acknowledgement is hereby made to the EIPC for their permission to publish this paper which was presented at a recent EIPC seminar.

There is at present much industry activity related to solderability testing. Test methods, test parameters, and accelerated ageing conditions are among the items being studied, but the bulk of the activity relates to component terminations, and not to printed wiring boards (PWBs). At Rockwell International's Collins Defense Communications, test programmes related to PWB ageing and solderability have been ongoing for several years. Data from natural ageing and from a variety of accelerated test methods have been compared. Results from several solderability test methods have also been compared. Recommendations are made for an accelerated ageing method and for solderability testing of PWBs.

The paper presents the results of extensive studies on circuit board solderability comparing wetting balance and IPC test methods through performance in vapour phase and wave soldering operations. The effects on solderability of key parameters are examined and compared with storage times of one year, and accelerated ageing using damp heat, dry heat and steam oxygen. An evaluation is made of tin‐lead alloys from 40/60 to 70/30 in solder coating thicknesses from 0·1 to 1·0 mil.

The service environment of urban polyethylene (PE) pipes has a crucial influence on their long-term safety and performance. Based on the application and structural performance analysis of PE pipe failure cases, this study aims to investigate the impact of organic substances in the soil on the aging behavior of PE pipes by designing organic solutions with different concentrations, which are based on the composition of organic substances in the soil environment, and periodic immersion tests.

Soil samples in the vicinity of the failed pipes were analyzed by gas chromatography-mass spectrometry, sensitive organic substances were screened and soaking solutions of different concentrations were designed. After the soaking test, the PE pipe samples were analyzed using differential scanning calorimetry, Fourier-transform infrared spectroscopy and other testing methods.

The performance difference between the outer surface and the middle of the cross section of PE pipes highlights the influence of the soil service environment on their aging. Different organic solutions can have varying impacts on the aging behavior of PE pipes when immersed. For instance, when exposed to amine organic solutions, PE pipes may have an increased weight and decreased material yield strength, although there is no reduction in their thermal or oxygen stability. On the contrary, when subjected to ether organic solutions, the surface of PE pipe specimens may be affected, leading to a reduction in material fracture elongation and a decrease in their thermal and oxygen stability. Furthermore, immersion in either amine or ether organic solutions may result in the production of hydroxyl and other aging groups on the surface of the material.

Understanding the potential impact of organic substances in the soil environment on the aging of PE pipe ensures the long-term performance and safety of urban PE pipe. This research approach will provide valuable insights into improving the durability and reliability of urban PE pipes in soil environments.

A significant number of integrated circuit (IC) package leads failing solderability tests also had a very thin eutectic solder coating. Poor solderability is attributed to degradation of this coating during various burn‐in times and temperatures. Techniques were developed to pre‐tin IC leads with lead‐rich solder (95Pb‐5Sn) as this finish had been reported in the literature to be particularly effective and superior to the eutectic composition in preserving solderability even after long ageing treatments. The present work has not confirmed those recommendations. In fact, surface analyses and various solderability tests performed on steam‐aged finishes demonstrate that 95Pb‐5Sn is not a viable alternative to 63Sn‐37Pb if standard spacecraft soldering practices are to be followed. Good solder wetting was always achieved if the artifically aged leads had a minimum eutectic coating thickness of 5–7 micrometres.

Today's electronic assembly manufacturing operations can be complex combinations of process steps such as IR reflow, wave soldering, special soldering of connectors or sensitive components, cleaning, rework, etc. Such multiple exposures to elevated temperatures and/or oxidising environments (e.g., aqueous cleaning) can have a negative effect on the solderability of printed wiring board (PWB) surfaces. This in turn may limit the effectiveness of subsequent soldering operations, such as wave soldering following an IR reflow step. The purpose of this study is to assess the impact of individual assembly process steps on the solderability of PWB surfaces. The PWB surfaces are initially treated with protective coatings of benzotriazole (BTA). The process steps investigated include: IR reflow in air and in nitrogen; vapour phase reflow; aqueous cleaning; adhesive cure; and wave soldering as a function of solder temperature and flux type. Meniscograph wettability testing is used to measure relative solderability changes, and Auger electron spectroscopy (AES) is used to monitor surface chemical changes, particularly oxide formation. The overall result is a body of fundamental information providing insight into optimisations of process flows, equipment operating specifications, process temperatures and selection of flux types.

The purpose of this paper is to present the results of a two-year long study carried out in order to evaluate the corrosion performance of mild steel bare bars (BB) and epoxy-coated rebar (ECR) in concrete under a simulated harsh environment of chlorides.

The blocks are subjected to Southern Exposure testing. The electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and Tafel plot are performed to measure the polarization resistance and corrosion current densities of these rebars. Knife-peel test was performed to assess the adhesion between epoxy and underlying steel after two years of exposure.

Mild steel BB showed a high corrosion current density of 1.24 µA/ cm² in Tafel plots and a very low polarization resistance of 4.5 kΩ cm² in LPR technique, whereas very high charge transfer resistance of 1672 and 1675 kΩ cm² is observed on ECR and ECR with controlled damage (ECRCD), through EIS technique, respectively. EIS is observed to be a suitable tool to detect the defects in epoxy coatings. After two years of immersion in 3.89 percent NaCl⁻ solution, the mild steel BB were severely corroded and a considerable weight loss was observed, whereas under heavy chloride attack, ECR showed no deterioration of epoxy coating and neither any corrosion of underlying steel. Results of this study show that the durability of reinforced concrete (RC) structures with respect to corrosion could be enhanced by using ECR, especially in harsh climatic conditions.

The corrosion performance of mild steel and ECR in concrete under a simulating splash zone environment is evaluated. EIS was used to evaluate the health of epoxy and corrosion state of underneath steel rebars. EIS was able to detect the defects in epoxy. The durability of RC structures could be enhanced in harsh climate regions by using ECR.

The industry trend towards higher density interconnect on PWBs has caused board fabricators to explore alternatives to the traditional hot air solder levelling (HASL) technology. Problems with pad planarity in the assembly of fine pitch devices with high I/O counts are well documented. Organic finishes based on substituted imidazoles address some of the assembly requirements, as do precious metal finishes such as gold and palladium. However, both types of solderable finish have limitations or undesirable characteristics. This paper discusses and compares other non‐precious metal systems as alternative solderable finishes. Immersion plating processes based upon bismuth and silver have been developed, and the data presented demonstrate that the solderability of these systems is superior to that of organic and palladium finishes. Test results on hole‐fill, solder‐spread and meniscograph (wetting balance) are extensively discussed in this study. Potential concerns over joint reliability and diffusion are addressed. The chemistry of these non‐precious metal systems also affords benefits to the PWB fabricator. These include increased yields, reduced costs and the elimination of soldermask compatibility issues. Considering possible future industry trends, a significant advantage of these materials is their full compatibility with lead‐free solders. Data on compatibility with solder replacements and wire‐bonding technology are also presented.

This paper aims to provide a deeper understanding of using filling materials that are used to fill gaps in wooden objects, and their response to changes in the surrounding environment to evaluate wood gap fillers and choose the best material. As a wide variety of materials, but most of them were unsuitable for filler mixtures. Specific materials were used, which can adapt to changes in wood size in response to changes in humidity. This research discusses the results of experiments that were conducted to determine how gap fillers composed of glass microballoons, microcrystalline cellulose and paper pulp fills are mixed with Klucel G, Paraloid B-72 and methyl cellulose as binders, and respond in various conditions.

It requires using several scientific and analytical techniques to provide a deeper understanding of filling materials characterization, dimensional stability, their shrinkage and study mechanical properties.

The analytical study of filling gaps in wooden objects with different filling materials allowed defining that the main drawbacks of the examined gap fillers were low water resistance, poor dimensional stability upon drying, or exposure to water vapor or liquid water, and fragility. Two types of gap fillers with high mechanical properties and pH values similar to those of wood were found to be appropriate for application on wooden archaeological artifacts.

The importance of the experimental study was to determine suitable filling materials and provide the basic characteristics of filling materials reversibility, workability, dimensional stability, lack of shrinkage, drying, ability to take color and be shaped, stability with aging, compatibility with wood in terms of behavior with changing humidity and non-toxicity. Also, strength properties or their likelihood to deform easily allowing changes in the shape of the wooden object during the movement of wood, either of which may be desirable in specific circumstances.

The possibility of the corrosion of metals due to contact with plastic materials has been known for a very long time. This is a matter of consequence, especially in the instrument and the lighter electrical sections of engineering industry. Therefore much attention has been given to the subject by technologists concerned in these fields.