IPC criteria for flux residue in terminal soldering
Soldering is very common process in wire harness manufacturing, it's a critical method to connect the wire and terminals, and flux residue is common for soldering. Cleaning after soldering is a process to make sure the soldering quality is good and with a good cosmetic. So we normally follow IPC-A-620 to inspect the flux residue.
Flux residue may be present if it is no-clean flux residue that is not intended to be cleaned. (No illustrations)
Target - Class 1,2,3
• No visible flux residue.
Acceptable - Class 1
Process Indicator - Class 2,3
• Flux residue does not inhibit visual inspection.
• Flux residue does not inhibit access to test points of the assembly.
Acceptable - Class 1
Defect - Class 2,3
• Flux residue on, around, or bridging between noncommon conductors.
• Flux residue inhibits visual inspection.
• Flux residue inhibits access to test points of the assembly.
Defect - Class 1,2,3
• Wet, tacky, or excessive flux residues that may spread onto other surfaces.
• No-clean flux residue on any electrical mating surface that inhibits electrical connection.
4 Soldered Terminations
4.3.4 Cleanliness – Flux Residue
Target - Class 1,2,3
• There is an insulation clearance (C) of one diameter (D)
Between the end of the insulation and the top of the solder fillet.
Acceptable - Class 1,2,3
• The insulation clearance is two wire diameters (D) or less including insulation or 1.5 mm [0.060 in] (whichever is greater).
• Insulation clearance does not permit shorting to adjacent conductors.
• Insulation clearance is near zero.
