1. “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:takahak@ide.titech.ac.jp http://www.ide.titech.ac.jp/~takahak/

2. Prior to this lecture... Activities of Japanese welding community • Organizations and their roles • Japanese system of education and certification • Movement around Asian Welding Federation

3. 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.

4. 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

5. 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 ?

6. 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 ?)

7. 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

8. 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）

9. Capillary action Wetting phenomenon • Surface tension or • Surface energy

10. Solidus Liquidus Solidus temperature • phase diagram • Equilibrium phase • Lever rule

12. example Soldering is key technology in micro-electronics assembly

13. example Soldering is key technology in micro-electronics assembly

14. example “flip chip” technology

15. Solders for electronics Eutectic phase • conventional solder • Sn-Pb (Sn-38Pb 180C) • lead free solders • Sn-Ag (Sn-3.8Ag 220C) • Sn-In • Sn-Bi • Sn-Zn • etc...

16. Wire bonding by Kaijo by H.Miyazaki, S.Saito, et.al...

17. Pb ( lead ) problem for health • Mental development index – age -> • Audition handicap - Pb in blood • Blood pressure - Pb in blood (positive correlation)

18. Solders for electronics eutectic phase • conventional solder • Sn-Pb (Sn-38Pb 180C) • lead free solders • Sn-Ag (Sn-3.8Ag 220C) • Sn-In • Sn-Bi • Sn-Zn • etc...

19. Sn-Ag-Bi-Sb-Cu • Sn-Ag-In • Sn-Ag-Bi-Cu • ... Solders for electronics • conventional solder • Sn-Pb (Sn-38Pb 180C) • lead free solders • Sn-Ag (Sn-3.8Ag 220C) • Sn-In • Sn-Bi • Sn-Zn • etc...

23. 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

25. example Al brazing

26. example Ni brazing

27. example Ag brazing of Stainless and Ceramics

28. 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

29. 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...

30. Diffusion bonding, Hot pressing, and Solid phase bonding Samples are • heated, and • pressed. • Sometimes metal sheet is inserted. “filler metal” ? in brazing

31. Another type of equipments • Hot Isostatic Pressing (HIP)

32. Example Ni alloy

33. Requirements for joining • to bring atoms near stable inter-atomic distance

34. Phenomena • Soldering and Brazing and also • Diffusion bonding • Hot pressing • Solid phase bonding • Wetting • Heat transfer • Dissolution • Flow • Diffusion • Deformation • Oxidation • Reduction • Solidification

35. 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...

36. 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)

37. 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

38. Brazing/Soldering temperature = Liquidus temp. + 50~100 K ( because of viscosity )

39. Brazing filler metals and solders • Brazing filler metals in Japanese Industrial Standards (JIS)

41. Fluxes and atmosphere Fluxes • Shielding • Reduction of surfaces Requirements • wettable • easily removable • never harmful Shielding gas Wettability

42. Set up and joint shape

45. Phenomena in brazing and soldering • Wetting ( Surface and interfacial tension ) • Conduction of heat • Dissolution • Flow • Diffusion • Deformation • Oxidation - reduction reaction • Solidification -> microscopic structure

46. Wetting driven by surface and interfacial tension • What determines equilibrium ( contact angle, meniscus, etc… ) ? • surface and interfacial tension • Young’s equation

47. 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.

48. 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,

49. 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

50. 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)