(1) characteristics of flux paste used in cleaning free process
① non toxic, no serious smell, no environmental pollution, safe operation.
② no halide, no corrosive effect.
③ there is enough high surface insulation resistance.
④ good weldability and few welding defects.
⑤ there is less residue after welding, and the board surface is dry and not sticky.
⑥ online test ability after welding.
⑦ ion residues shall meet the requirements of no cleaning.
(2) requirements for cleaning free liquid flux
① appearance: transparent liquid, no precipitation, no strong odor.
② solid content: no more than 2%.
③ halogen content: 0
④ weldability: the expansion rate is more than 80%.
⑤ copper mirror test: passed.
⑥ surface insulation resistance: greater than 1.0x10 (11) Ω.
(3) reference technical indexes of PCB used in cleaning free process
① PCB solderability test method can be used by wetting weighing method according to ipc-eia jstd003b and gb-t4677.
② surface contamination test. In general, use a visual or more than 4 times magnifying glass, and detect PCB board pollution with the help of light. The board surface is not allowed to have ash pressing, hand printing, oil stain, rosin, glue residue or other external pollution.
③ test method for surface insulation resistance of PCB light board (before PCB assembly)
(4) reference technical indexes of components used in cleaning free process
① component solderability test.
② component clean level test. It can also refer to the test method and standard of PCB light plate before assembly.
(5) reference technical indexes of solder alloy used in cleaning free process
① alloy composition