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Printed Circuit Board Terminology
Published in Robert P. Hedden, Cost Engineering in Printed Circuit Board Manufacturing, 2020
Prior to actual soldering flux must be applied to the surfaces to be soldered. Flux is a chemical mixture that removes metal oxides and aids solder adhesion and wetting. Wetting is the proper, smooth, flow of solder on a surface, as opposed to balling up. There are two basic categories of flux: rosin based and water soluble. Rosin is extracted from pine trees and mixed with a solvent and activator to make the flux. Water-soluble fluxes are more active than rosin-based fluxes. They solder surfaces of poorer quality but are very corrosive and must be completely and quickly removed. Water-soluble fluxes are chemical mixtures and do not actually contain water in any great quantity. The flux residue must be neutralized with a chemical and washed away with water. Fluxes can be applied by wave, foam, brush, spray, or dip.
Water/Wastewater Conveyance
Published in Frank R. Spellman, Handbook of Water and Wastewater Treatment Plant Operations, 2020
The heat source normally used to solder is heated using an oxyacetylene torch or some other high-temperature heat source. Important soldering points to remember include: Always use the recommended flux when soldering.Make sure parts to be soldered are clean and their surfaces fit closely together.During the soldering process, do not allow the parts to move while the solder is in a liquid state.Be sure the soldering heat is adequate for the soldering job to be done, including the types of metal and the fluxes.Wash the solder work in hot water to stop later corrosive action.
Second and Third Level Packaging Considerations for the use of Electronic Hardware at Elevated Temperatures
Published in F. Patrick McCluskey, Richard Grzybowski, Thomas Podlesak, High Temperature Electronics, 2018
F. Patrick McCluskey, Richard Grzybowski, Thomas Podlesak
The Sn-Pb near-eutectic alloy melts at approximately 183°C and solder processing (joining the package to the board) is normally performed around 220°C. This solder has a two- phase structure: a tin-rich phase and a lead-rich phase. A Sn-Pb phase diagram showing the melting temperature as a function of composition is found in Figure 6.6 This solder wets metallized surfaces well provided the surfaces are clean. Flux is used to remove oxides on the metallized surfaces and assist in the spreading of the solder. As the solder wets and spreads over the surface, the tin reacts with the metallization to form an intermetallic compound that is indicative of a good bond. After solidification, near-eutectic Sn-Pb solder has excellent electrical conductivity. The solder also has adequate time-dependent deformation characteristics allowing it to take up strain caused by the difference in coefficients of thermal expansion of joined materials without damaging the component or board. The mechanical and thermomechanical stability of the alloy is sufficient for electronic packaging applications.
Review of microstructure and properties of low temperature lead-free solder in electronic packaging
Published in Science and Technology of Advanced Materials, 2020
Kai-Kai Xu, Liang Zhang, Li-Li Gao, Nan Jiang, Lei Zhang, Su-Juan Zhong
As we all know, rare earth elements (La, Pr, Nd, etc.) are called ‘vitamins’ of metal elements, A small amount of rare earth elements can change the properties of solder [31]. As a large country of rare earth, China is rich in rare earth. The study of rare earth elements has a profound impact on the properties of composite solder. Dong et al. [32] studied the wettability of Sn-58Bi composite solder by adding rare earth element Ce. The results showed that the melting point of the solder did not change significantly, but the wettability area of the composite solder reached the maximum when the content of Ce was 0.1 wt%. This is mainly because Ce is a surface active element with a large atomic radius. Ce element does not dissolve in the solder. It is usually dispersed on the solder surface, which reduces the surface tension between the solder and the flux, and makes the solder fully wetted in the base metal. Liu et al. [33] reported that adding 0.5 wt.% Ni nanoparticles to Sn-Bi-Ag solder can effectively improve the wettability of the composite solder. Nano Ni elements gather on the surface of the liquid solder to reduce the surface tension of the solder due to the strong surface activity of Ni nanoparticles, thus enhancing the fluidity of the liquid solder. Gain et al. [34] also found that the wetting area of Sn-Bi solder on Cu substrate was about 20% higher than that of Sn-Bi solder when Y2O3 nanoparticles were added to Sn-Bi solder.
Structure and properties of Sn-Cu lead-free solders in electronics packaging
Published in Science and Technology of Advanced Materials, 2019
Meng Zhao, Liang Zhang, Zhi-Quan Liu, Ming-Yue Xiong, Lei Sun
A large number of studies have shown that the wetting in the actual soldering process is related to the properties of the solder, but mainly depends on the role of the soldering fluxes [115–117]. Moreover, the influence of different kinds of flux on the wettability of solder is significant, for example, the differences in contact angles for Sn-0.7Cu and Sn-0.7Cu-0.3Ni solders by three different fluxes [111]. Under atmospheric conditions, the surface of the solder metal and substrate metal will be covered with a layer of the oxide film, which is very unfavourable to the spread of the solder melt on the substrate metal. In the soldering process, the use of fluxes can remove the oxides on the surface of the solder and substrate metal well, creating good conditions for the solder to infiltrate in the substrate metal. In addition, the flux can cover the substrate metal and the solder surface with a thin liquid layer to avoid the occurrence of secondary oxidation. Finally, it can enhance the fluidity and heat transfer capacity of the solder melt due to the activity of the flux. The fluxes should satisfy the following requirements as far as possible: (a) Dissolve or destroy the oxide film on the solder and substrate metal; (b) Suitable range of activity temperature; (c) Good thermal stability; (d) Small viscosity and density, good fluidity; (e) No malignant corrosion of solder joints; (f) Easy removal of post soldering residue; (g) Reasonable economy.
Optimization of A-TIG process parameters using response surface methodology
Published in Materials and Manufacturing Processes, 2018
Ravi Shanker Vidyarthy, Dheerendra Kumar Dwivedi, Vasudevan Muthukumaran
A possible interaction between base metal characteristics and flux composition has been described here by using the basic principles of heat conductivity and experimental evidence from the past investigations. The effectiveness of the flux depends on the base metal characteristics such as thermal conductivity and chemical composition. The thermal conductivity of the base metal affects the fractional amount of heat intact in the weld pool for the fusion as well as the solidification time. The higher the thermal conductivity, the more would be the heat loss through conduction and thus produce small fusion zone area compared to the less thermally conductive material. Less thermal conductive materials also exhibit higher solidification time, which results in more effective fluid flow against Marangoni convection in the weld pool. The average thermal conductivities of the ASS and FSS are approximately 16.5 Wm−1 K and 25 Wm−1K, respectively [30]. Hence, the heat dispersion should be more in FSS. Hence, higher thermal conductivity may be one of the potential reasons responsible for lower DOP in FSS compared to the ASS.