Overview of Selected Issues Related to Soldering

The formation of defects and imperfections in the soldering process can have many causes, which primarily include a poorly setup technological process, inappropriate or inappropriately used materials and their combinations, the effect of the surroundings and design errors. This chapter lists some examples of errors that can occur in soldering, while review is devoted to selected defects: non-wettability of the solder pads, dewetting, wrong solder mask design, warpage, head-in-pillow, cracks in the joints, pad cratering, black pad, solder beading, tombstoning, dendrites, voids, flux spattering from the solder paste, popcorning and whiskers

Electrochemical migration of lead-free solders and Ag-based electrically conductive adhesives in NaCl solution

In this article, the electrochemical migration of lead-free solders and electrically conductive adhesives with an Ag content of more than 70% was studied by using a water drop test in NaCl solution. The results of solder pastes were compared with the results of electrically conductive adhesives. It was found that some solder pastes with a low Ag content have a lower susceptibility to electrochemical migration than, for example, solder paste Sn42Bi58. The highest resistance to corrosion has a conductive adhesive CRM-1033B with an Ag content of 75%. Resistance and voltage during the water drop test. From the measured values, it was determined that the values of resistance and voltage decrease with dendrite growing. X-ray spectroscopy was also performed to determine the chemical elemental composition of dendrites. It was found that the dominant element of the dendrite of solder pastes was Sn. In the case of electrically conductive adhesives, Ag was the main element of the dendrite

Introduction of wild MAP species into the field culture

Althea officinalis L., Dracocephalum moldavica L., Gentiana lutea L., Rhodiola rosea L., and Valeriana officinalis L. are the species of wild medicinal plants which are not very commonly grown in field culture. The methods and practical experiences of their multiplication and growing in a field nursery in Olomouc (the Czech Republic) are explained and shown in the manuscript

Evacuation in the Context of Pandemic

Článek se zabývá evakuací obyvatelstva v současných pandemických podmínkách. Cílem článku není poskytnout jasné odpovědi a řešení na otázky, které v nynější komplikované době v oblasti evakuace vznikají. Cílem je informovat o problémech, které nastaly v důsledku pandemie COVID-19 a otevřít odbornou diskusi v této problematice, které by mohla přinést možná řešení současné ztížené situace.This article deals with the evacuation of our population in the current pandemic conditions. The article should not provide clear answers and solutions to questions that arise due to the current complicated time in the field of evacuation. The aim of the article is to inform about the problems that have arisen as a result of the COVID-19 pandemic and to open an expert discussion on this issue. This discussion could bring possible solutions to the current difficult situation

Experimental implementation of the optimal linear-optical controlled phase gate

We report on the first experimental realization of optimal linear-optical controlled phase gates for arbitrary phases. The realized scheme is entirely flexible in that the phase shift can be tuned to any given value. All such controlled phase gates are optimal in the sense that they operate at the maximum possible success probabilities that are achievable within the framework of any postselected linear-optical implementation. The quantum gate is implemented using bulk optical elements and polarization encoding of qubit states. We have experimentally explored the remarkable observation that the optimum success probability is not monotone in the phase.Comment: 4 pages, 5 figures, 1 tabl

Genetic resources of Thymus vulgaris L. and T. vulgaris x T. Marschallianus Willd. in the Czech Republic

Two varieties of Thymus vulgaris L. (´Krajový´ and ´Winter´) and three its hybrids with T. Marschallianus Will. (variety ´Mixta´ and two accessions of variety ´Lemona´) were evaluated according the Draft Descriptor List Thymus vulgaris L. and analysed for the essential oil content and composition in years 2014 and 2015. All evaluated accessions were found morphologically and/or chemically different. Varieties ´Krajový´, ´Winter´ and ´Mixta´ were assessed as a thymol type with the thymol (39.1 – 69.6 %), o-cymene (6.3 – 24.9 %) and γ-terpinene (2.75 – 13.8 %) as main oil components. The two accessions of ´Lemona´ variety were found significantly different each other: one of them (income No. 3239) was assessed as a terpineol type with the terpineol acetate (75.7 %) and α-terpineol (16.9 %) as main oil components and the other one (income No. 2757) as a geraniol type with the geranyl acetate (±42.4 %) and geraniol (±20.8 %) as main oil components. Only the accession with income No. 3239 was proved as a ´Lemona´ variety due its citral (±9.3 %) content, though even this content is too small compare to original ´Lemona´ where about 20 % of citral was declared

Effect of Recrystallization on β to α-Sn Allotropic Transition in 99.3Sn-0.7Cu wt. % Solder Alloy Inoculated with InSb

The effect of recrystallization of 99.3Sn-0.7Cu wt % solder alloy on the allotropic transition of β to α-Sn (so-called tin pest phenomenon) was investigated. Bulk samples were prepared, and an InSb inoculator was mechanically applied to their surfaces to enhance the transition. Half of the samples were used as the reference material and the other half were annealed at 180 °C for 72 hours, which caused the recrystallization of the alloy. The samples were stored at -10 °C and -20 °C. The -Sn to α-Sn transition was monitored using electrical resistance measurements. The expansion and separation of the tin grains directly during the -Sn to α-Sn transition process were studied using scanning electron microscopy. The recrystallization of the alloy suppresses the tin pest phenomenon considerably since it decreased the number of defects in the crystal structure where heterogeneous nucleation of -Sn to α-Sn transition could occur. In the case of InSb inoculation, the spreading of the transition towards the bulk was as fast as the spreading parallel to the surface of the sample

Betonica officinalis L. in the Czech Republic. II. Seed production and quality and variability of total polyphenols content

S u m m a r y the vriability of seed quality (1000-seed weight, germination capacity) and content of polyphenols were studied in situ and ex situ in Wood Betony (Betonica officinalis) from 10 natural sites of Czech Republic. the statistically significant differences in almost all studied characters were found between the plants from these localities in situ as well as ex situ in field cultivation in olomouc. the cultivation of this species is convenient and also production of seeds was satisfactory in the isolation cages with bumble-bees as pollinators. In average 60.0±47.4 g of seeds per 20 plants were reached with 1000-seed weight 1.3±0.1 g and germination capacity 35.6±27.4 %. this seed quality was found to be comparable with naturally produced one. the content of total polyphenols ranged from 16.7 to 33.3 mg.g -1 in dry matter. wide range of disorders, especially as a nervine and tonic for treating maladies of the head and as an external application to wounds MaterIalS and MethodS Plant material For B. officinalis populations study, 10 natural sites in 4 protected landscape areas (or in the neighbouring localities) in the Czech Republic were chosen -the plant material used was the same as for previous article "Betonica officinalis L. in the Czech Republic. I. Variability of morphological characteristics" Seed production In order to test the possibilities of seed production 20 plants coming from some original localities were kept isolated during the flowering period in 2009, it means from mid-may till the end of flowering. technical isolation was realised by mobile isolation cages of size 2.0 x 3.0 x 1.7 m (width x length x high) covered by silon net. the bumble bees in small bumble-bee colonies were used as pollinators. When the seeds became mature (the beginning of September), whole plants were harvested by hand and dried in field drier of controlled airflow. then seeds were crumbled by hand, cleaned on sieves and then carefully cleaned by hands and the 1000-seed weight was measured. the number of seeds was calculated with use of seed counter. the same method was also used for testing of germination capacity of seeds produced in controlled conditions. this experiment was started on 2.11.2009 and lasted for 82 days. total content of polyphenols the total content of polyphenols was analysed in mixed sample from each group of plants separately and all the plant samples from the field nursery were prepared the same way for the evaluation of active substances content: the full flowering stems were harvested by hand, dried in the temperature lower than 35°C (drying house with controlled air circulation) and grinded by laboratory homogenizer. each sample representing the locality and the source stage (mother plants/seeds) was mixed with the all plants of the group. the content of total polyphenols was measured by spectroscopy -a colour precipitate reaction of polyphenols with Folin-Ciocalteau phenol reagent assay was used Statistical evaluation Statistical evaluation of obtained data was done by anova, one-factor analysis of variance with level of importance α=0.05 resp. 0.01. reSultS and dIScuSSIon Seed quality the quality of seeds collected at the natural localities was tested after drying and cleaning. the 1000-seed weight varied from 0.594 g (České Středohoří -mentaurov in 2005) to 1.3142 g (České Středohoří -malečov in 2004) (tab