- ໂດຍ WFsensors
Moisture is a major hidden threat to pressure sensors. It can get in by condensation, absorption or through tiny gaps, changing the electrical and mechanical properties of sensor elements and causing drift, slower response or permanent failure. This piece covers practical measures across design, manufacturing and maintenance to prevent and remove moisture, aimed at engineers and technical decision-makers. It emphasises a pragmatic “physical barrier + active management” approach and refers to the supplied image of a small SMD pressure sensor (with a vent hole) to illustrate common structural risks.
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1. Direct effects of moisture on sensor sensitive elements
When a sensor’s sensitive element is exposed to high humidity or condensation, its resistance, insulation resistance and the elastic properties of strain elements can change, causing calibration drift and more noise. Moisture accumulates at material interfaces — in resin, glass fibre layers and on board edges — and that can make conductors or circuits damp, increasing the chance of leakage or short circuits and eventually leading to functional failure. For thin-film or micro-mechanical sensing structures, moisture uptake changes mechanical stress and raises hysteresis, so accuracy and response time suffer. The SMD pressure sensor pictured, once mounted on a PCB without adequate protection, can let moisture concentrate around its small vent hole and exposed pads, speeding up the degradation of the sensitive element.
How absorption and condensation break conductive paths
When water condenses on or inside a sensor, previously insulating gaps can become liquid bridges and cause micro shorts or leakage currents. Absorption also alters capacitance and resistance around potting materials, adhesives and vias, which affects filtering and signal bandwidth. For PCB pressure sensors and SMD packages this is especially critical: tiny solder joints or trapped moisture in vias can go through many wet/dry cycles with temperature change, causing irreversible damage over time.
2. How moisture gets in — assembly and process risks
Moisture doesn’t have a single entry method. Cold surfaces, moisture in the air during assembly and sudden expansion of trapped moisture during baking are all common causes. In PCBs with different via densities, trapped moisture dries at different rates; a heavily saturated board can take hundreds of hours at elevated temperature to fully dry out. If board moisture is too high during soldering, internal water expansion at reflow temperatures can create tiny cracks or delamination, reducing long-term reliability.
Condensation, assembly and baking dynamics
In cold conditions, device surfaces cooler than ambient will fog up just like a window, and that leads to condensation. If assembly environments aren’t humidity-controlled, water vapour can be trapped before sealing; even later drying steps can push moisture deeper into layers. Baking removes moisture but heating can also make trapped water expand suddenly and move into deeper layers, making it harder to remove later. That’s why storage, assembly and soldering processes must work together to control board moisture and ambient humidity.
3. Design stage: block moisture paths from the outset
At the design stage you should prioritise building a physical barrier. Choose the right ingress protection rating for the application, and combine mechanical seals with breathable waterproof solutions so you can sample air without letting liquid water or bulk vapour in. For sensors that need to sense pressure, fit a gas-permeable but water-blocking membrane on any intake so the sensor can “breathe” yet remain protected. Inside the cavity, leave space for a desiccant and an access point for maintenance, so field servicing and drying are straightforward.
Housing seals, vent membranes and internal moisture control
Use O-rings, threaded seals or laser welding to reduce gaps to a minimum. Fit vent membranes that let gas through but stop liquid water. Add desiccant packs or hydrophobic coatings inside the cavity to protect PCB surfaces. For the SMD sensors shown in the image, apply solder mask and coverage layers on the PCB side, and design physical barriers around sensitive areas to limit where moisture can collect.
4. Manufacturing and process: reduce uptake and boost packaging reliability
During manufacturing, material choice and surface treatment can greatly improve moisture resistance. Nano-scale coatings give a thin, uniform protection layer without compromising thermal performance — unlike thick potting — and they tackle water, salt fog and insulation problems. Potting and flexible sealing remain important, especially where shock or mechanical protection is needed. Crucially, control board moisture before soldering: for high-temperature reflow (around 260°C) boards should be under 0.1% moisture, and for lower-temperature reflow (around 230°C) under 0.2%, or you risk moisture expansion creating cracks or layer separation.
Nano coating, potting and solder moisture control
PECVD and similar nano coating techniques form dense, even films over chips and PCBs to fight moisture and contaminants. Compared with bulk epoxy potting, nano coatings are thin, easier to rework and often about 20% cheaper in some workflows. Potting compounds like silicone gel also protect delicate MEMS strain gauges while offering mechanical cushioning. Process control should include moisture level checks and baking records so every board meets the soldering threshold and the risk of internal damage from reflow is minimised.
5. Operation & maintenance: actively manage moisture risk
Field management matters just as much. Regular replacement or topping-up of cavity desiccants, checking seals and confirming vent membranes are clear are basic maintenance tasks. For critical systems, embed a tiny humidity sensor inside the cavity to monitor moisture and trigger alerts if thresholds (for example >60% RH) are exceeded. Remote arrangements that keep the electronics in a dry enclosure and stream data wirelessly reduce exposure. Also, tune calibration schedules and use humidity compensation algorithms where needed to reduce measurement error caused by ambient swings.
Desiccant upkeep, humidity sensing and remote protection
Adjust maintenance intervals to the environment: high-humidity sites need more frequent desiccant changes and shorter calibration cycles. Built-in cavity humidity sensors let the device warn operators before damage occurs, enabling timely maintenance and averting long-term drift. For PCB and SMD sensors, design consumable moisture protection as replaceable modules so field teams can swap components without full device disassembly, cutting downtime.
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Moisture is a slow, hidden killer for sensitive sensor elements and must be tackled in design, manufacturing and operation. The recommended approach is a robust physical barrier (sealed housing, vent membranes, sensible cavity layout) plus active measures (desiccants, cavity humidity monitoring, strict moisture control before soldering). For SMD and PCB pressure sensors, integrating micro humidity sensing and easily serviceable moisture control parts will greatly extend life and preserve accuracy. Choose solutions based on environment, maintenance ability and cost, always prioritising long-term electrical and mechanical stability of the sensitive element.
The above introduction only scratches the surface of the applications of pressure sensor technology. We will continue to explore the different types of sensor elements used in various products, how they work, and their advantages and disadvantages. If you’d like more detail on what’s discussed here, you can check out the related content later in this guide. If you are pressed for time, you can also click here to download the details of this guides ຂໍ້ມູນ PDF ຜະລິດຕະພັນ PDOR Air.
For more information on other sensor technologies, please ເຂົ້າເບິ່ງຫນ້າສັນຍາລັກຂອງພວກເຮົາ.