(1) Characteristics of flux solder paste used in free-clean process
1 Non-toxic, no serious odor, no environmental pollution, safe operation.
2 Does not contain halides, no corrosion.
3 Has a high enough surface insulation resistance.
4 Good solderability, less solder ball soldering defects.
5 There are few residues after welding, and the board surface is dry and not sticky.
6 Has online testing capability after welding.
7 Ion residues should meet the free-clean requirements.
(2) Requirements for free-clean liquid flux
1 Appearance: transparent liquid, no precipitation, no strong irritating odor.
2 Solid content: no more than 2%.
3 Halogen content: 0.
4 Fluxability: expansion rate is greater than 80%.
5 Bronze mirror test: Pass.
6 Surface insulation resistance: greater than 1.0x10 (11) Ω.
(3) Reference technical specifications of PCB used in free-clean process
1 PCB solderability test method can be wet weighed according to IPC-EIA JSTD003B and national standard GB-T4677.
2 Surface contamination test. In general, use a magnifying glass that is visually or more than 4 times, and use the light to detect the contamination of the PCB surface. No external contamination such as ash, fingerprints, oil stains, rosin, slag or other materials is allowed on the board surface.
3.PCB bare board (before pcb assembly) surface insulation resistance test method,
(4) Reference technical specifications of components used in free-clean process
1. Component solderability test.
(5) Reference technical specifications of solder alloys used in free-clean processes
1 Alloy composition