With the increasing emphasis on health and hygiene, disinfection cabinets have become essential electrical appliances in households, catering establishments, medical institutions, and other settings. The control board, as the "brain" of the disinfection cabinet, directly determines the equipment's operational stability, disinfection efficiency, and safety performance. However, the working environment of disinfection cabinets poses severe challenges to the control board: during the high-temperature disinfection process, water vapor evaporates and condenses, resulting in high relative humidity (up to 85%-95%) inside the cabinet; grid voltage fluctuations (such as surge, spike, and undervoltage) caused by power grid load changes or lightning strikes can easily damage sensitive electronic components on the control board.

Statistical data shows that over 60% of disinfection cabinet failures are attributed to control board malfunctions, among which 35% are caused by humidity-induced corrosion and short circuits, and 25% by overvoltage damage. Therefore, strengthening the anti-humidity and overvoltage protection design of control boards is crucial to improving the overall reliability of disinfection cabinets, reducing after-sales maintenance costs, and enhancing user experience. This paper systematically explores the key technologies and implementation schemes for anti-humidity and overvoltage protection, aiming to provide practical design references for engineers in the field.

2. Failure Mechanisms of Disinfection Cabinet Control Boards Under Humid and Overvoltage Conditions

2.1 Failure Mechanisms Induced by Humidity

The high-humidity environment inside the disinfection cabinet mainly causes the following failures of the control board:

Electrochemical corrosion: Moisture penetrates the control board and combines with impurities (such as dust, residues) to form an electrolyte solution. The different electrode potentials of components (such as copper pads, solder joints, and chip pins) trigger electrochemical reactions, leading to corrosion of metal conductors, solder joint peeling, and increased contact resistance.

Short circuit and leakage: Condensed water droplets on the board surface cause short circuits between adjacent pins or tracks, resulting in abnormal operation of the control circuit; the insulation performance of PCB substrates and components degrades under high humidity, leading to leakage current increases and even insulation breakdown.

Component damage: Humidity intrusion into chips, capacitors, resistors, and other components causes internal parameter drift, reduced service life, or direct burnout. For example, electrolytic capacitors are prone to electrolyte leakage and capacity attenuation under high humidity, affecting the stability of the power supply circuit.

Signal interference: Moisture-induced changes in the dielectric constant of the PCB substrate and the surface impedance of components interfere with the transmission of analog signals (such as temperature/humidity detection signals), leading to inaccurate control of disinfection parameters.

2.2 Failure Mechanisms Induced by Overvoltage

Overvoltage in the power grid mainly includes transient overvoltage (such as lightning strikes, switching operations) and sustained overvoltage (such as grid voltage rise), which cause control board failures through the following paths:

Direct breakdown of components: The rated voltage of sensitive components on the control board (such as chips, diodes, and capacitors) is relatively low. When the input voltage exceeds the rated value, the components are easily broken down and damaged, resulting in the paralysis of the entire control system.

Burnout of power supply circuit: Overvoltage causes excessive current in the power supply module (such as voltage regulators, rectifier bridges), leading to overheating and burnout of components, and loss of power supply capacity.

Damage to control logic: Overvoltage may interfere with the logic level of the microcontroller (MCU), causing program runaway, false triggering of control signals, and abnormal operation of disinfection functions (such as incorrect start/stop of ultraviolet lamps or heating tubes).

3. Anti-Humidity Protection Design of Disinfection Cabinet Control Boards

3.1 Material Selection and PCB Design Optimization

PCB substrate selection: Prioritize moisture-resistant substrates such as FR-4 with high glass transition temperature (Tg ≥ 150℃) and low water absorption rate (≤ 0.15%), which can effectively resist moisture penetration and reduce the risk of insulation degradation.

Copper foil and solder mask optimization: Use thick copper foil (≥ 1oz) for PCB tracks to improve corrosion resistance; select high-quality solder mask ink with good moisture resistance and adhesion, ensuring full coverage of the board surface (excluding pads and component pins) to form a protective barrier against moisture.

Component selection: Choose moisture-proof