Microstructural Characterisation of Bi-Ag-Ti Solder Alloy and Evaluation of Wettability on Ceramic and Composite Substrates Joined via Indirect Electron Beam Heating in Vacuum

The work deals with the study of Ti effect in solder type In10Ag4Ti on bond formation with the ceramic materials Al2O3, SiC and ZrO2. The aim of this research was to study the wettability and interfacial reaction between solder and ceramic substrates using the progressive hybrid technology - laser/ultrasound. The goniometric method was used for the solder wettability measurement. The wettability of the solder on the ceramic substrates at the temperature of 700°C attained the values from 17 to 34°. Structural analysis of the boundary between the solder and substrate was carried out by scanning electron microscopy. The planar analysis of elements in bonds between the ceramic substrates and solder revealed the presence of a higher concentration of Ti on the boundaries. The wetting of oxidic ceramic materials was assured by bonding of titanium with oxides from the substrate’s surface by the formation of a thin layer of TiO. The SiC substrate was wetted by In10Ag4Ti solder owing to the reaction of titanium with carbon and/or silicon by the formation of reaction layers TiC and TiSi. The reaction between titanium from the solder during soldering and ultrasonic activation provided wetting and interactions between the solder and the ceramic substrates.

PurposeThis study aims to investigate soldering of SiC ceramics by using Zn-Al-In-based solders and ultrasonic soldering. The focus was on the quality of soldered joints, examining the boundary of the solder/substrate joint and the strength of the fabricated joints. Moreover, the fractured surfaces of joints were assessed.Design/methodology/approachThe Zn-5Al base, which is considered for eutectic solder, was used in experiments. When manufacturing this solder, In was also added to at 1 Wt.%. The soldering of SiC substrates on a hot plate with ultrasonic assistance was performed.FindingsThe solder at room temperature consists of a primary segregated solid solution (Zn) and the binary eutectics (Zn) + (Al) with a high Al content and binary lamellar eutectic with a high Zn and In content non-uniformly distributed on the grain boundaries. The average tensile strength of the Zn5Al1In solder was 52 MPa. The ceramic material was wetted during soldering via reaction between the solder and the SiC substrate, with the formation of Al-Si reaction products. The thickness of the reaction layer on the boundary was 0.5–1.1 µm. The average strength of the soldered joint was 59 MPa. The obtained results confirmed the high efficiency of ultrasonic soldering in air.Originality/valueThis work has characterised Zn5Al1In soldering alloy and examining soldering SiC ceramics by a flux-less ultrasonic process. The analyses were oriented to assess the strength and structure of the solder and the soldered joints. Based on the achieved results, it is possible to predict the suitability of the solder alloy for flux-free soldering of SiC ceramics.

In this work, the soldering of Sn3.5Ag4Ti (Ce,Ga) active alloy filler with SiC substrates in different times was conducted to explore the soldering mechanisms at 250 °C in air. Experiment results showed that the microstructure and element distribution are closely related to the soldering time. A series of experiments were carried out at 250 °C, and the soldering times were set to be 1, 15, 30, 60 min, respectively. Cross-section of the solder joints were observed by a scanning electron microscopy (SEM) and the element distribution were analyzed by energy dispersive spectrometer (EDS). Results show that when the soldering time is 60 minutes, the Ti element is segregated at the SiC/SnAgTi interface. By theoretically analyzing the wetting behavior of the active solder at the SiC substrate, it could be inferred that the adsorption of the active element titanium at the SiC/solder interface plays a key role, which reduces the interface energy and drives the molten solder well wetting on the surface of SiC substrates at low temperature. The interfacial behavior of Ti between active solder and SiC substrate has been studied and bonding mechanism has been explored. Our understanding of the wettability of alloy solder on SiC, the diffusion kinetics of Ti element, and soldering mechanism provides the basic knowledge for the development of low temperature active soldering technology.

This research aimed to study a Bi-Ag-Mg soldering alloy and the direct soldering of Al2O3 ceramics and Ni-SiC composites. Bi11Ag1Mg solder has a broad melting interval, which mainly depends on the silver and magnesium content. The solder starts to melt at a temperature of 264 °C. Full fusion terminates at a temperature of 380 °C. The microstructure of the solder is formed by a bismuth matrix. The matrix contains segregated silver crystals and an Ag (Mg, Bi) phase. The average tensile strength of solder is 26.7 MPa. The boundary of the Al2O3/Bi11Ag1Mg joint is formed by the reaction of magnesium, which segregates in the vicinity of a boundary with a ceramic substrate. The thickness of the high-Mg reaction layer at the interface with the ceramic material was approximately 2 μm. The bond at the boundary of the Bi11Ag1Mg/Ni-SiC joint was formed due to the high silver content. At the boundary, there were also high contents of Bi and Ni, which suggests that there is a NiBi3 phase. The average shear strength of the combined Al2O3/Ni-SiC joint with Bi11Ag1Mg solder is 27 MPa.

Relationship between wettability and interfacial reaction for Sn10Ag4Ti on Al 2O 3 and SiC substrates

Wetting and interfacial behavior of Cu–Al/SiC systems: Influences of Si ion implantation and Al concentration

The Ghawar field in Eastern Saudi Arabia contains the largest accumulation of carbonate reservoirs in the world. The majority of wells in the field produce from the Arab-D reservoir, an Upper Jurassic limestone sealed by anhydrite. Oil production from the field started approximately 55 years ago. Water injection started in the 1970's. Long before water injection was considered for the reservoir, the evaluation of wettability was considered essential. Our present day evaluation of Arab-D wettability takes into account a long historical record of wettability measurements and production history. The procedures, results and caveats of the original measurements have changed slightly but they also show a strong consistency fifty years later. Wettability indices obtained from initial tests, Amott, and USBM methods generally indicate neutral to slightly oil-wet character for cores processed and tested in a preserved state. Comparisons with restored state cores did not indicate major differences. Over the years fluids used in coring operations and core preservation have shown little impact on the observed results. Local variations in wettability indicating mixed wettability and oil-wet tendencies can be observed when tar is present in a significant amount and in areas high on structure. The combination of methods from advanced SEM observations, to qualitative contact angle measurements, to relative permeability results all point to a common wettability value.

We have performed 2D X-ray diffraction mapping of the SiC lattice basal plane orientation over full 2” SiC substrates. Measurements of the omega angle were made in two perpendicular directions <11-20> and <1-100>, which gives the complete vectorized tilt of the basal planes. The Mapping revealed two characteristic bending behaviors on measured commercial wafers. The first is characterized by large variations in omega angle across the wafer in both crystallographic directions. The continuously changing omega angle in both directions gives the wafer an apparent rotationally symmetric bending which is concave towards the growth direction. The second characteristic behavior is seen in wafers with lower degree of omega angle variation. The variations in this type of wafers are not changing linearly, but are bending the basal planes with two-fold symmetry.

Growth of AlN films on SiC substrates by RF-MBE and RF-MEE

Surface chemistry and mechanical behavior of silicon carbide and silicon nitride implanted with titanium to high fluences and high temperatures

Bonding mechanism in ultrasonic-assisted soldering of ZrO2 and 304 stainless steel using a micro-alloyed active solder alloy

The purpose of this present study was to evaluate the effect of vacuum (i.e., 10−5 mbar) heat treatment at 300 to 1100 °C on morphological, thermo-optical, mechanical and tribological properties of 75 μm thin SS304 foils. Microstructural, morphological and surface properties of the foils were characterized by field emission scanning electron microscopy (FESEM), profilometry, x-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) measurement techniques, respectively. The x-ray diffraction (XRD) was employed to identify the phase of SS304 foils after different heat treatment temperatures. Thermo-optical properties such as solar absorptance (αs), reflectance (ρs) and IR emittance (εir) were also evaluated. The nanomechanical properties i.e., nanohardness (H) and Young’s modulus (E) of as-received and heat treated SS304 foils were evaluated by the nanoindentation technique. Tribological and tensile properties i.e., yield strength (σy) and percentage of elongation of different heat treated foils were also investigated by single pass scratch tests and universal testing machine, respectively. Noteworthy grain growth of SS304 was observed beyond vacuum heat treatment temperature of 700 °C. As a consequence, the magnitudes of both H and E data of SS304 were significantly decreased beyond the vacuum heat treatment temperature of 700 °C. Further, the hardness data followed the well known Hall–Petch relationship. On the other hand, the tribological property of SS304 was significantly deteriorated beyond the vacuum heat treatment temperature of 700 °C. The tensile strength of the foils was also altered after the heat treatment.

The authors are exploring the feasibility of the plasma synthesis of highly-adherent films of alumina and chromia on SiC and FeAl substrates. A magnetically-filtered cathodic arc plasma deposition technique is used in which a high density metal plasma (Al or Cr) is formed and deposited on the substrate in the presence of a low pressure gaseous oxygen background. The substrate is simultaneously repetitively pulse biased, providing a means of controlling the incident ion energy. In the early stages of the process the ion energy is held in the keV range so as to produce atomic mixing at the film-substrate interface (ion stitching), and in the latter stages of deposition the energy is reduced to {approximately}200 eV (IBAD range) to provide a means of controlling the film structure and morphology. Films that are dense and highly adherent can be formed in this way. The authors have produced near-stoichiometric films of alumina and chromia on small SiC and FeAl substrates and characterized the films in a number of ways, including RBS, X-ray diffraction and adhesion, and we`ve also done some preliminary temperature cycling experiments. The alumina films are of thickness from 0.2 to 1.5.{micro}, amorphous prior to heat treatment, and show an {alpha}-alumina phase after heat treating at 1,000 C for up to 16 hours. The film substrate adhesion is typically greater then {approximately}70 MPa prior to heating, and initial results indicate that the films maintain their adhesion after repetitive cycling in temperature between ambient and 1,000 C. Here they describe the plasma processing method and outline the experimental results obtained to-date.

The effects of strong‐acid treatment on an epitaxial graphene film on a SiC substrate are investigated to confirm its stability and compatibility with conventional semiconductor device fabrication processes. An epitaxial graphene film is treated with a strong acid in the form of piranha solution (H2O2 + H2SO4), which is conventionally used in washing processes for the silicon‐based technology. Raman spectroscopy, Hall measurements, and contact angle measurements are carried out before and after piranha treatment. Raman mapping results show no drastic changes before and after piranha treatment. In particular, the D band is not observed after the piranha treatment. From Hall measurements, the electron mobility slightly increases from 920 to 1420 cm2 V−1 s−1 after five piranha treatments. The contact angle is almost constant before (72.8°) and after five piranha treatments (75.2°). These results indicate that the epitaxial graphene film is quite stable under piranha treatment.

The aim of the research was to characterize the soldering alloy type Zn-Mg-Sr and direct the soldering of SiC ceramics with Cu-SiC-based composite. It was investigated whether the proposed composition of the soldering alloy was appropriate for soldering those materials at the defined conditions. For the determination of the solder melting point, TG/DTA analysis was applied. The Zn-Mg system is of the eutectic type with a reaction temperature of 364 °C. The effect of strontium on the phase transformation was minimal, owing to its lower content. The microstructure of the soldering alloy type Zn3Mg1.5Sr is formed of a very fine eutectic matrix containing segregated phases of strontium—SrZn13 and magnesium—MgZn2 and Mg2Zn11. The average tensile strength of the solder is 98.6 MPa. The tensile strength was partially increased by solder alloying with magnesium and strontium. The SiC/solder joint was formed due to the distribution of magnesium from the solder to the boundary with the ceramics at the formation of a phase. Owing to soldering in air, oxidation of the magnesium took place and the oxides formed were combined with the silicon oxides that remained on the surface of the ceramic material—SiC. Thus, a strong bond based on oxygen was obtained. An interaction between the liquid zinc solder and the copper matrix of the composite substrate took place at the formation of a new phase—γCu (Cu5Zn8). The shear strength was measured on several ceramic materials. The average shear strength of the combined SiC/Cu-SiC joint fabricated with Zn3Mg1.5Sr solder was 62 MPa. When soldering similar ceramic materials mutually, a shear strength of as much as around 100 MPa was observed.