Three proof processing flow for optocoupler packaging

1, Preprocessing stage
Substrate cleaning
Slag removal and cleaning: Use board cleaning water (alcohol is prohibited) to thoroughly remove any residual flux, dust, or oil on the PCBA after soldering, ensuring that the surface is free of ion contamination.
Drying treatment: After cleaning, it should be thoroughly dried in an oven at 80-100 ℃ (≥ 30 minutes) to avoid residual moisture affecting the adhesion of the coating
Sensitive area masking protection
Contact point protection: For areas such as test points and connectors that do not require coating, use high-temperature resistant latex masking tape or customized tape discs to cover them (ensuring that the tape is free of silicides to prevent anti wetting).
Efficiency optimization: It is recommended to use automated selective coating equipment during mass production to avoid low manual coating efficiency
2, Three proof coating process
Material selection
Common types:
Epoxy resin: Excellent insulation (high CTI value), resistant to chemical corrosion, but poor toughness.
Polyurethane (such as Loctite US2350): resistant to high and low temperatures (-40 ℃ to 150 ℃), strong impact resistance, suitable for potting and surface coating
Organosilicon: Temperature resistance (-60 ℃ to 200 ℃), but weak adhesion.
Optical requirements: If it involves transparent areas (such as inside optocouplers), epoxy resin with a transmittance greater than 91% should be selected.
Application of sealant
Structural isolation: For multi-channel optocouplers, high-voltage insulation glue (such as Loctite UF3808) can be filled into the pre formed cavities of the upper and lower modules, and then heated and cured to achieve full sealing.
Stress control: Low stress glue is preferred to avoid packaging cracking caused by temperature changes
Rework and repair
If maintenance is required after curing, the coating needs to be partially dissolved (such as wettin