“Soldering and Brazing” comparing withDiffusion bonding, Hot pressing, and Solid phase bonding Dr. Kunio TAKAHASHI - Associate professor, Dept. of International Development Engineering, Tokyo Institute of Technology,Tokyo 152-8552, Japan Phone/Fax:+81-3-5734-3915 E-Mail:email@example.com http://www.ide.titech.ac.jp/~takahak/
Prior to this lecture... Activities of Japanese welding community • Organizations and their roles • Japanese system of education and certification • Movement around Asian Welding Federation
About lecturer’s ... • Back ground welding ( what is this ? ) • Tokyo Institute of technology http://www.titech.ac.jp/ • Department of International Development Eng. Networkbeyond the border of engineering field (community) nation http://www.ide.titech.ac.jp/ Welcome to Japan Already, you have joined to our Network.
Welding Technology, as ”Inter-Field” Engineering based on • Plasma physics • Electronics/Electrical Eng. Power Source • Control (“self-controlled” is the best) = Heat sources • Thermal Eng. • Fluid dynamics • Material science • Fracture mechanics Physics of phenomena Standard Industry roles of Society • Plasma • e--beam • Laser • Joule’s heat • etc… Steels (Materials) - Making - Design
About this lecture “Brazing and Soldering …” • Basic knowledge based on physics • Phenomena • Comparison with other welding processes • What is and what is not clarified, theoretically ? • Recent progresses for physical understanding. so, • You will understand... • Why and How the process is used ? Experimental training • How the process can be modified ?
Contents of this lecture • Definition of brazing and soldering • Examples • Comparison with other welding processes • Heat sources • Brazing filler metals and solders • Fluxes and atmosphere • Set up and joint shape • Phenomena in brazing and soldering • Wetting ( surface and interfacial tension ) • Conduction of heat • Dissolution • Flow • Diffusion • Deformation • Oxidation - reduction reaction • Solidification -> microscopic structure • Exercise Please remember in your experimental training (Sept.19 ?)
Definition of the brazing and soldering. • Joint is heated • distributing filler metal between base materials, • by capillary action • below solidus temperature of base materials. • Sometimes the joint is pressed. example of brazing main engine LE7A H2A rocket
Filler metals • Brazing melting point of filler metal >723 K （ 450 C, 840 F） • Soldering melting point of filler metal <723 K （ 450 C, 840 F）
Capillary action Wetting phenomenon • Surface tension or • Surface energy
Solidus Liquidus Solidus temperature • phase diagram • Equilibrium phase • Lever rule
example Soldering is key technology in micro-electronics assembly
example Soldering is key technology in micro-electronics assembly
Solders for electronics Eutectic phase • conventional solder • Sn-Pb (Sn-38Pb 180C) • lead free solders • Sn-Ag (Sn-3.8Ag 220C) • Sn-In • Sn-Bi • Sn-Zn • etc...
Wire bonding by Kaijo by H.Miyazaki, S.Saito, et.al...
Pb ( lead ) problem for health • Mental development index – age -> • Audition handicap - Pb in blood • Blood pressure - Pb in blood (positive correlation)
Solders for electronics eutectic phase • conventional solder • Sn-Pb (Sn-38Pb 180C) • lead free solders • Sn-Ag (Sn-3.8Ag 220C) • Sn-In • Sn-Bi • Sn-Zn • etc...
Sn-Ag-Bi-Sb-Cu • Sn-Ag-In • Sn-Ag-Bi-Cu • ... Solders for electronics • conventional solder • Sn-Pb (Sn-38Pb 180C) • lead free solders • Sn-Ag (Sn-3.8Ag 220C) • Sn-In • Sn-Bi • Sn-Zn • etc...
Problems Pb free solder • Melting point problemsin processes almost solved • Viscosity • Corrosion still under R/D • Heating iron in iron soldering • Solder bath in reflow soldering
The highest technology is never used for space development. • The highest technology is the combination of conventional technologies. • Optimization & breakthrough are based on scientific understanding
Comparison with other welding or joining processes • melting base materials ex. arc welding, resistance welding, etc… • adding molten metals between base materials ex. brazing, soldering, etc... • not melting base materials ex. solid phase bonding, hot pressing, etc...
Diffusion bonding, Hot pressing, and Solid phase bonding Samples are • heated, and • pressed. • Sometimes metal sheet is inserted. “filler metal” ? in brazing
Another type of equipments • Hot Isostatic Pressing (HIP)
Requirements for joining • to bring atoms near stable inter-atomic distance
Phenomena • Soldering and Brazing and also • Diffusion bonding • Hot pressing • Solid phase bonding • Wetting • Heat transfer • Dissolution • Flow • Diffusion • Deformation • Oxidation • Reduction • Solidification
Heat sources for brazing and soldering • Oxyfuelgas flame :Torch brazing/soldering , braze welding • Arc plasma :Arc brazing, braze welding • Joule’s heat :Resistance brazing • Induction heat :Induction brazing • Hot iron :Iron soldering • Ultrasonic wave :Ultrasonic soldering • Infrared ray :Infrared soldering • Laser beam :Laser beam soldering etc...
Other terminology for brazing and soldering Atmosphere • Atmospheric brazing/soldering • Vacuum brazing • Furnace brazing • Dip brazing/soldering ex. of dip soldering • Metal bath brazing/soldering (in molten solder bath) • Salt bath brazing/soldering (in flux)
Other terminology Procedure • Abrasion tinning & re-flow • Re-flow soldering • Diffusion brazing/soldering • Transient Liquid Phase bonding ambiguous Diffusion bonding ( Hot pressing ) ? • Liquid phase diffusion bonding : iso-thermal solidification • Eutectic bonding : no filler metal and intent to melt base materials ex. Re-flow used in electronics
Brazing/Soldering temperature = Liquidus temp. + 50~100 K ( because of viscosity )
Brazing filler metals and solders • Brazing filler metals in Japanese Industrial Standards (JIS)
Fluxes and atmosphere Fluxes • Shielding • Reduction of surfaces Requirements • wettable • easily removable • never harmful Shielding gas Wettability
Phenomena in brazing and soldering • Wetting ( Surface and interfacial tension ) • Conduction of heat • Dissolution • Flow • Diffusion • Deformation • Oxidation - reduction reaction • Solidification -> microscopic structure
Wetting driven by surface and interfacial tension • What determines equilibrium ( contact angle, meniscus, etc… ) ? • surface and interfacial tension • Young’s equation
Surface and interfacial tension (Surface tension is interfacial tension between material and vacuum.) • Surface ( interfacial ) tension • ex. soap film • ex. soap bubble • Force on meniscus Laplace equation • Effect of gravity on meniscus on shape of fillet • Curvature changes with height.
Surface (interfacial) tension and Surface (interfacial) energy • Internal energy and entropy • 1st law and 2nd law of thermodynamics • For bulk, therefore • Variables for unit area of surface • For arbitrary area of surface, Therefore,
Relation between Surface (interfacial) tension and Surface (interfacial) energy • Surface contribution of internal energy is important. • at 0 K, Surface ( interfacial ) tension Surface ( interfacial ) energy Surface ( interfacial ) entropy
Theoretical approach for Electronic theory surface tension at 0 K (quantum mechanics) • Shifted step potential K.Takahashi, and T.Onzawa, Physical Review B, 48, 5689 (1993) • Stabilized jellium J.P.Predew, H.Q.Tran and E.D.Smith, Phys. Rev. B, 42, 11627 (1990). • SCF-jellium N.D.Lang and W.Kohn, Phys. Rev. B, 1, 4555 (1970). comparison by K.F.Wojciechovski, Surface Science, 437, 285-288 (1999)