Non-Arc Welding Processes Resistive heating, chemical reactions, focused light and electrons, sound waves, and friction can also be used to join materials –Resistance welding –Oxy-Fuel Welding –Friction welding (&Solid State) –Laser and electron beam welding –Brazing and soldering –Plastics joining –Adhesive bonding Introduction

Brazing (B) and Soldering (S) In these processes, the base metals are heated but do not melt; only the filler metal melts –Brazing filler metals having a melting point above 840° F (450°C) –Soldering filler metals have a melting point below 840°F (450°C) Brazing and Soldering

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Application of Low Thermal Expansion Alloys Thermal expansion mismatch in metal- ceramic joints can lead to cracks in the ceramic Thermal expansion coefficients at 25°C (10 -6 mm / mm·°C) –Alumina, 8.8 –Nickel, 13.3 –Iron, 11.8 –Kovar, 5.0 Alumina substrate Kovar lid Silicon chip Brazed joints T

Brazing Specifications AWS A5.8 Specification for Brazing Filler Metal –8 well-defined groups (B) plus a vacuum grade (BV) BAg-1(44-46 Ag, Cu, Zn, Cd) BAu-1(37-38 Au, remainder Cu) BCuP-1( P, remainder Cu) –Standard forms: strip, sheet, wire, rod, powder –Joint design tolerances, generally ~ inches –Uses for each braze material AWS C3.3 Standard Method for Evaluating the Strength of Brazed Joints Brazing and Soldering

Balchin & Castner, “Health & Safety…”, McGraw Hill, 1993

Advantages Joins unweldable materials –Base metals don’t melt –Can be used on metals and ceramics Joined parts can be taken apart at a later time Batch furnace can easily process multiple parts Portable when joining small parts Brazing and Soldering

Limitations Joint tolerance is critical Lower strength than a welded joint Large parts require large furnaces Manual processes require skilled workers Flux Filler metal ring surrounded by flux Brazing and Soldering