Hall sensors are an important type of magnetic field sensing device widely used in fields such as automotive electronics, industrial control, and consumer electronics. Due to its use of non airtight packaging, it is highly susceptible to external media and mechanical impacts in harsh environments such as high temperature, humidity, oil, vibration, etc. without effective protection. Therefore, potting and conformal coating are key components in the reliability design of Hall sensors.
Sealing: Injecting sealing material into the interior of the shell to form a complete package, providing electrical insulation, protection, and mechanical reinforcement;
Coating overlay: forming a thin film layer on the surface of PCB or sensitive components, mainly used for moisture, dust, and basic chemical protection.
1、 Environmental and mechanical protection methods
- The function of sealing
Sealing can effectively eliminate the following risks:
Environmental and chemical risks: such as moisture, oil, corrosive gases;
FOD (foreign object debris) protection: to prevent debris from falling and causing short circuits;
Mechanical shock and vibration protection: Improve structural reliability and prevent fatigue of solder joints and pins.
In some PCB free application scenarios, the pins of Hall sensors are directly soldered to the mold body. If there is a lack of encapsulation protection, vibration will cause the solder joints to be fragile and there is a risk of failure. At this time, the sealing material not only plays an electrical insulation role, but also significantly improves mechanical stability. - The function of coating coating
Main functions of coating coating:
Environmental and chemical protection;
Foreign object protection;
Provide limited vibration protection in light load environments.
Compared to encapsulation, coatings are more suitable for low stress or space constrained scenarios.
2、 Encapsulation in PCB free applications
Shallow sealing: suitable for scenarios with strict magnetic gap requirements (such as Hall elements with very small spacing between magnets). The encapsulation layer only covers sensitive areas, reducing mechanical impact and FOD risks, but the active surface of the sensor is usually exposed.
Side view of Hall sensor
Deep sealing: When the environment is harsh or requires high-strength mechanical protection, deep sealing is used. The components are covered as a whole, forming a sturdy barrier that can resist vibration, impact, and medium corrosion. 
Notes:
Before sealing, Z-axis fixation is required to avoid air gaps between the sensor chip and the housing;
Deep sealing requires ensuring that the sleeve height is sufficient to fully cover the IC with polymer;
For shallow sealing, adhesion can be improved by surface roughening grooves.
3、 Encapsulation in PCB applications
The main function of encapsulation in Hall sensors with PCBs is to:
Protect PCB circuits and solder joints from moisture and corrosion;
Enhance overall anti vibration and anti impact performance;
Combining coating technology to achieve composite protection.
4、 Selection of sealing materials
The performance of the sealing material directly determines the reliability of the Hall sensor. Common performance requirements include:
Working temperature range: Stable physical and electrical characteristics should be maintained throughout the entire application temperature range.
Adhesion: It should have good adhesion on both thermoplastic and thermosetting substrates.
Coefficient of thermal expansion (CTE): It should be as close as possible to the plastic casing to avoid cracking or peeling during thermal cycling.
Hardness: It needs to be hard enough to withstand impact and vibration, but not too brittle.
Water absorption rate: Low water absorption rate can prevent electrical performance degradation.
Chemical resistance: resistant to transmission oil, fuel, brake fluid and other media.
Viscosity and flowability: Low viscosity facilitates filling complex cavities and avoids bubbles.
Curing characteristics: It is necessary to ensure complete curing and exhaust, and deep cavities can be filled step by step.
Recommended materials
PUR 1680 A/B two-component solvent-free elastomer resin:
It can be cured at room temperature or by heating, and has flexibility after curing;
Low viscosity, good flowability, capable of deep filling;
Excellent low-temperature characteristics and weather resistance;
High electrical insulation, moisture-proof and waterproof;
Strong adhesion to most metals and plastics;
Green and environmentally friendly, free from heavy metals.
Typical applications: Casting and sealing of electronic components such as communication equipment, transformers, power modules, ignition controllers, sensors, etc.
Tags: pur 1680 · Sensor Sealing Protection · Polyurethane Sealing Adhesive · Hall Sensor Sealing Adhesive
