Publications

This paper examines the effects of the time and temperature of the curing process and the effect of the pad surface material on the electrical resistance of joints formed using electrically conductive adhesives (ECA). Two types of isotropic ECA, composed of a bis-phenol epoxy matrix filled with silver flakes, were tested. The experimental data were processed in two ways, by performing full factorial experiments (FFE) of the 23 type and by using an L4 type Taguchi orthogonal array, and the results were then compared. It was found that the joint resistance is mainly affected by the curing temperature, and is less dependent on the curing time and the surface material. The interactions between these factors have been analyzed through FFE. The results showed that the Taguchi method is quite precise for the main factors, but is insufficiently accurate for processes with significant numbers of interactions.

Void is defined such as blow hole in the solder joint. Voids may degrade the mechanical and conductive properties of the solder joint and thus decrease the reliability. Article deals with influence of humidity on voids formation inside the solder joint structure. Experimental part was carried on testing samples, where we used three types of solder pastes (Sn62Pb36Ag2, Sn96.5Ag3Cu0.5 and Sn95.5Ag4Cu0.5), three types of reflow technology (hot air, vapor phase and infra radiation reflow technology) and three types of humidity environments. The inspection was made on X-ray and following diagnostic was made by image analysis with special software.

Electrically conductive adhesive with epoxy matrix and silver filler was used for forming of adhesive joints. The joints were at first aged at the humidity near 100 % for 300 hours. The joints were then loaded with the rectangular current pulses with the amplitude 10 A, 20 A and 50 A. The width of the pulses was 5 microseconds, the frequency 50 Hz. It was found that the pulses changed the joints resistance.

This paper presents a comparison of properties of BaTiO3 ceramics prepared by two different production methods:gas-stabilized plasma spraying (GSP) and spark plasma sintering (SPS).Samplesof both materials were evaluated by various techniques,the goal being to detect theCurie temperature of the ferroelectric transformation between the tetragonal and the cubic phase.All tests,resonant ultrasound spectroscopy,dielectric measurements,differential scanning calorimetry and temperature-resolvedX-ray diffraction (XRD), used in combination,proved the absence of this transformation in the case of GSPcoating up to 500 °C. Similarly,the tetragonal-to- orthorhombic transition temperature is shifted downwards,this transition probably taking place in a small fraction of the volume of coating. The SPS samples exhibit several anomalies, such as astrong anisotropy of relative permittivity, but their phase transformations were detected in the usual temperature ranges.

This paper presents a study of dielectric properties, namely the relative permittivity and loss factor dependence on the frequency of a weak electric field. Perovskite CaTiO3 was studied in the form of coatings and self-supporting plates made by plasma spraying. A conventional gas stabilised plasma gun (GSP) as well as a water stabilised plasma gun (WSP) were employed. It was observed that plasma sprayed titanates exhibit a strong relaxation of permittivity and loss factor decrease with a frequency rise. These properties are influenced by spray technique and spraying parameters, but the relaxation character in general is preserved in all cases. The volume resistivity of the samples was studied as well. Several aspects of the structural features of plasma deposits, especially the phase composition, porosity character, and their influence on dielectric properties are discussed.

The paper covers the area of a process risk analysis. A new approach based on the use of affinity diagram combined with fuzzy logic brings new light in this area. Combination of fuzzy logic and affinity diagram for a better solution of a risk analysis problem is presented in this paper. An affinity diagram for a process was created. Process steps, operations and potential failures in these parts of a process were estimated. Significance of the failures was described using fuzzy logic. This way made a deeper process analysis possible. Fuzzy logic combined with the affinity diagram provides in-depth review of the process and mainly shows the degree of an influence of the failures on further steps and operations of the process. It can detect occurrence of new failures as well. New approach based on combination of a risk analysis tool – affinity diagram – with support of fuzzy logic is generic and can be applied to any technological or production process.

Presented work shows the results of DSC measurement for six Sn based solders. The alloys Sn96Ag4, Sn99Cu1, Sn97Cu3, Sn96.5Ag3Cu0.5, Sn95.5Ag3.8Cu0.7 and Sn63Pb37 were studied in the temperature range from room temperature up to 400 °C. The transformation temperatures for melting as well as for solidification were influenced by the composition and thermal history of the alloys.

Titanium dioxide coatings were sprayed by WSP gun to form self-supporting bodies with a photocatalytically active surface. Prepared bodies were studied by XRD, HR-TEM, XPS, Raman spectroscopy, UV-VIS spectrophotometry and photocatalytic tests.Porosity was studied by image analysis also microhardness was measured.

XRD measurements were carried out on plasma sprayed titanates BaTiO3, CaTiO3, MgTiO3 and a mixture of last two. Samples were tested as dielectrics and volume resistivities of the materials were also summarized. Microwave microscopy was used for mapping of the dielectric response of selected samples. The results exhibit differences in the crystal structure between plasma sprayed coatings and feedstock powders.

This article deals with the mechanical stress of lead and lead free soldered joints. During usage of electrical equipment are found structural changes of soldered joints, which can lead to cracks or failure of the solder joints. In this article, the changes of the electrical resistance of dynamic and static stressed soldered joints (lead Sn62Pb36Ag2 and lead free Sn95,5Ag4Cu0,5) are compared.