Igor Kostolný

Research of Fluxless Soldering of High-Purity Aluminium with Solders Type Zn-Al

The aim of work consists in the study of interactions on solder/substrate boundary in fluxless soldering of Al with 4N purity by ultrasound activation. The ZnAg6Al6 and ZnAl4 solders were used in experiments. The soldering parameters were as follows: soldering temperature from 400 oC to 420 oC, acting time of ultrasonic vibrations 5 to 20 s, ultrasound frequency 40 kHz. Soldered joints were assessed by optical light microscopy, EDXmicroanalysis and XRD analysis. It was found out that the ZnAg6Al6 solder is composed of αAl, βZn solid solutions and AgZn3phase. The ZnAl4solder consists of βZn primary solid solution and a lamellar eutectic Zn-Al structure. The main mechanism of joint formation between the solders type Zn-Al and Al substrate during soldering consists in eutectic reaction between the liquid Zn and solid Al. An eutectic βZn-αAl mixture was observed on the joint boundary in case of both solders. In case of Al/ZnAg6Al6 joint also AgZn3intermetallic compound was observed in the transition zone.

Study of Direct Bonding Ceramics with Metal Using Sn2La Solder

The aim of this research was to study the direct bonding of ceramic materials, mainly Al2O3 and selected metals, with primary attention given to Cu substrate. Soldering was performed with Sn-based solder alloyed with 2% La. We found that the bond formation between Sn2La solder and Al2O3 occurs at the activation of lanthanum phases in solder by ultrasound. Lanthanum in the solder becomes oxidised in air during the soldering process. However, due to ultrasonic activation, the lanthanum particles are distributed to the boundary with ceramic material. A uniformly thin layer containing La, 1.5 µm in thickness, is formed on the boundary with Al2O3 material, ensuring both wetting and joint formation. The shear strength with Al2O3 ceramics is 7.5 MPa. Increased strength to 13.5 MPa was observed with SiC ceramics.

Investigation of Flux-Less Soldering of Metal Matrix Composite and Ceramics by Use of Zn Solder

The work was dealing with direct soldering of Al2O3 ceramics and a metal/ceramic composite (MMC) with Al matrix. The joints were fabricated by application of flux-less process by use of a hot plate at the assistance of ultrasound with frequency of 40 kHz. The experiments were performed by use of Zn6Al6Ag solder. Wetting was attained on both substrates. The joints of a good quality were fabricated. The soldering temperature was 420 °C. The microstructural studies of interface have revealed a transient zone of Al dissolving on the side of MMC and formation of Zn oxides on the side of ceramics, which were responsible for bond formation.

Effect of in Addition on Microstructure and Properties of Zn-5Al Solder

The effect of In addition on melting behaviors, microstructure and properties of Zn-5Al solder were investigated. It was found that addition of In decreasing the melting point of Zn-5Al solder. XRD analysis confirmed the presence of Indium in form of α-Zn+β-In solid solution. The segregation of In on grain boundary was observed. Segregation of In on grain boundary caused a significant decrease of strength of the Zn-5Al-In solder compared to Zn-5Al.

Laser Beam Ultrasonic Assisted Fluxless Soldering of Ceramics Using Bi-Ag-La Solder

The work dealt with the soldering of ceramic substrates by the application of laser beam heating using ultrasound assistance. The joints were fabricated at a laser beam power of 2 kW and ultrasound frequency of 40 kHz. The Bi11Ag2La alloy was applied as the solder, which wetted both substrates, namely Al2O3 and ZrO2. Wetting of the ZrO2 substrate was significantly better, attaining a wetting angle of 45.5°. In the case of Al2O3 the wetting angle attained just 73° under the same conditions. Neither a new transition layer, nor any contact interlayer were observed on the interface in either substrate. In spite of that, the fabricated joints achieved satisfactory quality and showed no cracks or irregularities.

Wettability of Soldering Alloys at Heating by Electron Beam

The aim of research consisted in the study of wettability of Sn-based solders on ceramic Al2O3 material by heating with electron beam without flux application. The Sn-based solders alloyed with active elements as Ti, La, Ce and Ga were applied for soldering. The active elements contained in solder volume oxidise during soldering in air. This problem can be eliminated by application of electron beam in vacuum. Soldering consisted of 15 minutes heating to desired temperature then dwelling on this temperature for 5 minutes and a slow cooling down in vacuum. The desired soldering temperature was 950 °C. The best wettability on Al2O3 substrate was achieved with SnAg3,5Ti4(Ce,Ga) solder, with wetting angle of 62°. The interactions between the solder and substrate were identified in the joint interface, ensuring the creation of a stable bond.

Wettability of Selected Lead-Free Solders for Higher Application Temperatures

The work deals with the research of wettability of lead-free solders for higher application temperatures. For the research of wettability, SnSb5, ZnAl4, ZnAl6Ag6 and BiAg11 solders were used on Ag, Cu and Ni substrates. The measurement was carried out in a controlled atmosphere by trigonometric method. Zn based solders wets none of the examined substrates. SnSb5 solder wets only Cu substrate with wetting angle of 54o. Soldering alloy BiAg11 wets all substrates, wherein the best results (23 o) was achieved on Ag substrate.

Effect of in Addition to Zn-5Al Solder on Microstructure and Properties of Solder Joints

The effect of In addition to Zn-5Al on the interfacial reaction behaviors and mechanical properties of solder joints were investigated. It was found that addition of In decreasing the melting point of Zn-5Al solder. The segregation of In on grain boundary was observed. CuZn5 and Cu5Zn8 intermetallic phases were observed at joint interface. Segregation of In on grain boundary caused a significant decrease of strength of the Zn-5Al-In solder compared to Zn-5Al. Addition of 1% In to Zn-5Al solder resulted in a reduction of shear strength of 14 MPa. The interfacial microstructure, shear strength and fracture surfaces of Zn-5Al/Cu and Zn-5Al-1In/Cu solder joints were studied.

Wettability of Soldering Alloys Heated by Electron Beam

The aim of research consisted in the study of wettability of Sn-based solders on ceramic Al2O3 material by heating with electron beam, without flux application. The Sn-based solders alloyed with active elements such as Ti, La, Ce and Ga were applied for soldering. The active elements contained in solder oxidise in air during soldering. This problem can be eliminated by the application of an electron beam in a vacuum. Soldering consisted of 15 minutes heating to desired temperature, followed by dwelling on this temperature for 5 minutes and slowly cooling in a vacuum. The desired soldering temperature was 950 °C. The best wettability on Al2O3 substrate was achieved with SnAg3, 5Ti4 (Ce, Ga) solder, with a wetting angle of 62°. The interactions between the solder and substrate were identified in the joint interface, ensuring the creation of a stable bond.

Influence of Alloying Elements in ZnAl5 Based Alloys on Melting Temperature, Tensile Strength and Vickers Hardness

The aim of work consist in the investigation of the influence of alloying elements in ZnAl5 alloy on thermal and mechanical properties. The ZnAl5Cu (1-3), ZnAl5Mg (1-3), ZnAl5Ag (1-5) and ZnAl5In1(Ga1) solder alloys were used experiments. Solders were assessed by DSC analysis and by measuring tensile strength and Vickers hardness. It was found out that by adding of alloying elements, the melting temperature is decreasing. The opposite was observed in the case of ZnAl5Mg (1-3) alloys. By adding of In or Ga to ZnAl5, tensile strength and Vickers hardness are decreasing. Addition of Ag (1-5) resulted in increasing of tensile strength and Vickers hardness. In case of ZnAl5Cu (1-3) and ZnAl5Mg (1-3) solder, decreasing of tensile strength and increasing of Vickers hardness was observed.