ULTRASONIC SOLDERING OF Cu AND Al2O3 CERAMICS BY USE OF Bi-La AND Bi-Ag-La SOLDERS

This work deals with the effect of solder alloying with a small amount of lanthanum on joint formation with metallic and ceramic substrate. The Bi-Ag – based solder with 2 wt.% lanthanum addition and Bi solder with 2 wt.% lanthanum addition were studied. Soldering was performed by afluxless process on the air, by activation with a power ultrasound. It was found out that, during the process of ultrasonic soldering, lanthanum is distributed on the boundary, both with the copper and the ceramic substrate, which enhances the joint formation. The bond with Al2O3 ceramics is of an adhesive character, without the formation of a new contact interlayer

Soldering by the Active Lead-Free Tin and Bismuth-Based Solders

The chapter deals with Sn and Bi-In-based lead-free solders. The term “active solders” is used for the solders which contain one or more elements with enhanced affinity to some element contained in the substrate material. Mainly, Ti, In, lanthanides, etc. belong amongst the active metals. The role of an active element is to ensure a good wetting by a reactive decomposition of the surface layer of substrate. The perspective solders for joining the combined materials, as ceramics/metal, are mainly the tin-based, lead-free solders, which are enriched with titanium (usually up to 4 wt. %). The advantage consists in the fact that they offers a sufficient plasticity reserve, by what they are capable to compensate undesired residual stresses formed in the joint. Titanium also reacts with carbon, nitrogen or oxygen of the ceramic material, eventually it forms the intermetallic phases, which increase the strength of joint interface. The Sn-Ti, Sn-Ag-Ti and Bi-In-Sn solders were selected for the experiments. These solders were applied for fabrication of Al2O3 ceramics/Cu joints. The phase composition and microstructure of solders and soldered joints was analysed. Interactions in the interface of ceramic/solder and Cu substrate/solder were determined. The shear strength of soldered joints was measure

Characterization of soldering alloy type Bi-Ag-Ti and the study of ultrasonic soldering of silicon and copper

The aim of the research work was to characterize the soldering alloy type Bi-Ag-Ti and to study the direct soldering of silicon and copper. Bi11Ag1.5Ti solder has a broad melting interval. Its scope depends mainly on the content of silver and titanium. The solder begins to melt at the temperature of 262.5 degrees C and full melting is completed at 405 degrees C. The solder microstructure consists of a bismuth matrix with local eutectics. The silver crystals and titanium phases as BiTi2 and Bi9Ti8 are segregated in the matrix. The average tensile strength of the solder varies around 42 MPa. The bond with silicon is formed due to interaction of active titanium with the silicon surface at the formation of a reaction layer, composed of a new product, TiSi2. In the boundary of the Cu/solder an interaction between the liquid bismuth solder and the copper substrate occurs, supported by the eutectic reaction. The mutual solubility between the liquid bismuth solder is very limited, on both the Bi and the Cu side. The average shear strength in the case of a combined joint of Si/Cu fabricated with Bi11Ag1.5Ti solder is 43 MPa.Web of Science114art. no. 62

Study of wettability and solderability of SiC ceramics with Ni by use of Sn-Sb-Ti solder by heating with electron beam in vacuum

The aim of this research was to study the wettability and solderability of SiC ceramics by the use of an active solder of the type Sn5Sb3Ti in a vacuum by electron beam heating. This solder exerts a narrow melting interval, and only one thermal effect, a peritectic reaction, was observed. The liquidus temperature of the solder is approximately 243 degrees C. The solder consists of a tin matrix where the Ti-6(Sb,Sn)(5) and TiSbSn phases are precipitated. The solder wettability on a SiC substrate decreases with decreasing soldering temperature. The best wetting angle of 33 degrees was obtained in a vacuum at the temperature of 950 degrees C. The bond between the SiC ceramics and the solder was formed due to the interaction of Ti and Ni with silicon contained in the SiC ceramics. The formation of new TiSi2 and Ti3Ni5Si6 phases, which form the reaction layer and thus ensure the bond formation, was observed. The bond with Ni is formed due to the solubility of Ni in the tin solder. Two phases, namely the Ni3Sn2 and Ni3Sn phases, were identified in the transition zone of the Ni/Sn5Sb3Ti joint. The highest shear strength, around 40 MPa, was attained at the soldering temperature of 850 degrees C.Web of Science1515art. no. 530

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

Characterizing the soldering alloy type Zn-Al-Cu and study of ultrasonic soldering of Al7075/Cu combination

The aim of the research was to characterize the soldering alloy type Zn-Al-Cu and study the fluxless ultrasonic soldering of the combination of aluminum alloy type Al7075 with copper substrate. The Zn-Al-Cu solder is of the close-to-eutectic type with two phase transformations: the eutectic transformation at 378 degrees C and the eutectoid transformation at 285 degrees C. The solder microstructure is formed of a matrix composed of the solid solutions of aluminum (Al) and zinc (Zn) in which the copper phases CuZn4 and CuAl2 are precipitated. The shear strength of the soldering alloy type Zn5Al with copper addition reaches values from 167 to 187 MPa and it depends on the copper content in the solder. The bond with aluminum alloy type Al7075 is formed due to the solubility of Al in zinc solder at the formation of solid solution Al. Contrary to this observation, the bond with the copper substrate is in this case formed due to the interaction of zinc and aluminum with the copper substrate. Two new intermetallic phases, namely Al(Cu,Zn)(2) and Cu3.2Zn0.7Al4.2, were formed. The average shear strength of Al7075/Zn5Al3Cu/Cu joints attained was 134.5 MPa. For comparison, the Cu/Zn5Al3Cu/Cu joint attained an average shear strength of 136.5 MPa.Web of Science111art. no. 2

Characterizing the Soldering Alloy Type In–Ag–Ti and the Study of Direct Soldering of SiC Ceramics and Copper

The aim of the research was to characterize the soldering alloy In–Ag–Ti type, and to study the direct soldering of SiC ceramics and copper. The In10Ag4Ti solder has a broad melting interval, which mainly depends on its silver content. The liquid point of the solder is 256.5 °C. The solder microstructure is composed of a matrix with solid solution (In), in which the phases of titanium (Ti3In4) and silver (AgIn2) are mainly segregated. The tensile strength of the solder is approximately 13 MPa. The strength of the solder increased with the addition of Ag and Ti. The solder bonds with SiC ceramics, owing to the interaction between active In metal and silicon infiltrated in the ceramics. XRD analysis has proven the interaction of titanium with ceramic material during the formation of the new minority phases of titanium silicide—SiTi and titanium carbide—C5Ti8. In and Ag also affect bond formation with the copper substrate. Two new phases were also observed in the bond interphase—(CuAg)6In5 and (AgCu)In2. The average shear strength of a combined joint of SiC–Cu, fabricated with In10Ag4Ti solder, was 14.5 MPa. The In–Ag–Ti solder type studied possesses excellent solderability with several metallic and ceramic materials

Characterization of Sn-Sb-Ti solder alloy and the study of its use for the ultrasonic soldering process of SiC ceramics with a Cu-SiC metal-ceramic composite

The aim of this research was to characterize soldering alloys of the type Sn-Sb-Ti and to study the ultrasonic soldering of SiC ceramics with a metal-ceramic composite of the type Cu-SiC. The Sn5Sb3Ti solder exerts a thermal transformation of a peritectic character with an approximate melting point of 234 & DEG;C and a narrow melting interval. The solder microstructure consists of a tin matrix, where the acicular constituents of the Ti-6(Sb,Sn)(5) phase and the sharp-edged constituents of the TiSbSn phase are precipitated. The tensile strength of the soldering alloy depends on the Ti content and reaches values from 34 to 51 MPa. The average strength of the solder increases with increasing Ti content. The bond with SiC ceramics is formed owing to the interaction of titanium, activated by ultrasound, with SiC ceramics, forming the (Ti,Si)(6)(Sb,Sn)(5) reaction product. The bond with the metal-ceramic composite Cu-SiC is formed owing to the solubility of Cu in a tin solder forming two phases: the wettable eta-Cu6Sn5 phase, formed in contact with the solder, and the non-wettable epsilon-Cu3Sn phase, formed in contact with the copper composite. The average shear strength of the combined joint of SiC/Cu-SiC fabricated using the Sn5Sb3Ti solder was 42.5 MPa. The Sn-Sb-Ti solder is a direct competitor of the S-Bond active solder. The production of solders is cheaper, and the presence of antimony increases their strength. In addition, the application temperature range is wider.Web of Science1421art. no. 636