Joining Processes: Soldering, Brazing, Riveting and Mechanical Fastening
What the domain tests
Joining Processes tests soldering, brazing, riveting and mechanical fastening. You must select a joint for the service conditions, prepare surfaces, control heat and use fasteners correctly.
Core rules
- Soldering joins below about 450°C with a low-melting filler; brazing uses a filler above 450°C and gives a stronger, higher-temperature joint. Both rely on clean surfaces and flux.
- Flux removes oxide but must suit the work: rosin flux for electronics, not acid flux. Avoid overheating; overheated flux stops working.
- Capillary action draws filler into a close gap. Parts must be clean, close-fitting and heated evenly.
- Rivets form a permanent joint. Choose diameter for load and length for grip; the formed tail needs enough material for a head.
- Bolts and screws allow dismantling. Use washers, correct thread engagement and controlled torque; lock nuts or thread-locking compound resist vibration.
Worked example
Two 2 mm steel plates are to be riveted with 4 mm diameter rivets. Grip = 2 + 2 = 4 mm. A common allowance for a snap head is about 1.5d, so rivet length ≈ 4 + (1.5 × 4) = 10 mm. Drill the holes slightly larger than the rivet, clamp the plates, insert the rivet and form the head without over-thinning the shank.
Traps
Acid flux on electronic joints causes corrosion; a dry joint comes from insufficient heat or dirty metal. Wrong rivet length gives a loose or split joint. Do not over-torque small bolts or use a rivet where the joint must be dismantled.