Exposed solder joints, sensor terminals and connectors corrode when bare metal sits in humid air. A thin, clear sealant coat over the joint keeps moisture out. Micron 3307 Protektor Acrylic Sealant is a soft, clear acrylic sealant whose page says it protects exposed electrical solders, connections, PCBs and sensors from moisture, humidity, corrosion and fungal growth, and can be sprayed, brushed or dipped. For full-board coverage to a MIL specification, use Micron 3100 conformal coating instead.
Why it happens
- Exposed metal at joints in a humid environment. Solder joints and terminals outside a sealed enclosure pick up moisture, and corrosion starts at the metal surface.
You will see green corrosion on joints, and faults in sensors and connectors that appear in humid or damp conditions.
How to fix it
- Exposed solder joints, sensor terminals or connectors, by brush or dip: Micron 3307 Protektor Acrylic Sealant, 1 L. Its page describes a thin, transparent, non-yellowing barrier that resists moisture and humidity, inhibits corrosion, provides a non-conductive layer, contains antifungal properties and dries quickly.
- Full-board aerosol coating to a MIL specification: Micron 3100 Protektor Conformal Coating, which its page says conforms to IPC-CC-830B / MIL-I-46058C.
The 3307 page does not give step-by-step directions or a temperature range. Follow the TDS. A general approach:
- Power off and disconnect.
- Clean the joints so the sealant bonds to clean metal. Micron 3400 PCB Cleaner is listed for cleaning contact points on wires and terminals.
- Let everything dry fully.
- Mask anything that must stay unsealed, such as mating faces of connectors.
- Apply an even coat by brush or dip, covering the whole joint.
- Let it dry before handling or powering.
What to avoid
- Clean joints before sealing (3400). Sealing over flux or corrosion traps it.
- Do not seal the mating surfaces of connectors; they need metal-to-metal contact.
- Do not present the sealant as protection against electric shock. It is a moisture and corrosion barrier.
- 3100 aerosol propellant is flammable (stated): coat unpowered boards, ventilate, and keep away from ignition.
- Follow the label and SDS for 3307 handling and ventilation.
When to ask an expert
Hand off if:
- you need immersion protection or an IP rating, which calls for potting or enclosure design, not a sealant coat;
- the sensor is safety-critical, such as on a vehicle braking or airbag system;
- corrosion has already eaten into the joint, which needs re-soldering or replacement first.
FAQ
What is the difference between a sealant and a conformal coating?
Both protect electronics from moisture. 3307 is a soft, clear sealant suited to sealing specific joints and components by brush or dip. 3100 is an aerosol conformal coating for whole boards, with IPC-CC-830B / MIL-I-46058C stated.
Will the sealant turn yellow?
Its page describes it as transparent and non-yellowing.
Can I seal a sensor connector?
The page lists sensors and connectors. Seal the joints and terminals, not the mating faces of the connector itself.
Can I apply it in the field, not just in the factory?
The page says it can be sprayed, brushed or dipped and dries quickly, and mentions brush-on bottles for industrial and DIY use. Field repairs are fine as long as the joint is clean, dry and unpowered first.
Do I need to remove the sealant to re-solder later?
Some sealant will need removing at the joint before re-soldering. The 3307 page does not name a remover, so ask Micron before planning rework.
What temperature can 3307 handle?
The page mentions protection over a wide temperature range but gives no figures. Ask Micron if your joint runs hot.
See the product: Micron 3307 Protektor Acrylic Sealant. Related: 3100 Protektor Conformal Coating, 3400 Protektor PCB Cleaner. More electronics fixes: electronics hub.