As a key component of electrical signal control, the stability of signal PCB relay's performance directly affects the reliability of the circuit system. The packaging process not only plays the role of fixing and protecting internal components, but also is the first line of defense against the invasion of external pollutants such as moisture and dust. Good packaging technology and moisture-proof and dust-proof performance improvement strategies can effectively avoid relay contact oxidation, short circuit and other faults, extend product life, and ensure the accuracy and stability of signal transmission.
At present, signal PCB relay mainly adopts three processes: injection molding, potting and surface mounting (SMT). Injection molding wraps the relay with molten plastic through a mold to form a solid shell. It has high sealing and mechanical strength and is suitable for mass production; the potting process is to fill the gap between the relay and the shell with liquid packaging material, and form a gapless sealing layer after curing. It has a significant effect on blocking moisture and dust, but the cost is high and it is not conducive to maintenance; the SMT process directly solders the relay on the PCB board through solder paste. The package size is small and the signal transmission loss is low, but it needs to be matched with a sealing rubber ring or coating to assist in improving the protection performance.
Moisture intrusion can cause oxidation of relay contacts, reduced insulation performance, and even short circuits. To improve moisture resistance, first of all, in terms of material selection, use packaging materials such as epoxy resin and silicone rubber with low water absorption; secondly, optimize the injection molding process, strictly control the mold accuracy, reduce the shell gap, and some high-end products will also add waterproof strips at the shell joints; thirdly, a potting glue with hydrophobic properties can be used in the potting process to form a dense waterproof layer on the surface of the relay; in addition, vacuum drying and nitrogen protection technology are introduced to remove internal moisture before packaging and isolate external moisture to further enhance moisture resistance.
Dust particles entering the interior of the relay may cause poor contact of the contacts or jamming of mechanical parts. Improving dust resistance requires both structural design and sealing treatment. In terms of structural design, labyrinth sealing grooves, dust-proof nets and other structures are used to prevent dust from entering; in terms of surface treatment, nano-scale dust-proof coatings are sprayed to prevent dust from adhering to the surface of the relay; for SMT-packaged relays, three-proof paint (moisture-proof, mildew-proof, and salt spray-proof) is used for comprehensive coating after welding to form a dust-proof protective film, while also enhancing moisture-proof and corrosion-proof capabilities.
A single packaging process or protective measure is often difficult to meet the needs of complex environments, so composite protection processes have gradually become the mainstream. For example, the injection molding package is combined with the potting process, and the basic shell is first formed by injection molding, and then the key parts are potted to achieve double protection; in terms of material selection, plastics with high mechanical strength are used in combination with high-performance sealants to take into account both firmness and sealing. In addition, by integrating temperature and humidity sensors in the packaging design, the internal environment is monitored in real time. Once moisture or dust is detected to exceed the standard, the heating dehumidification or dust cleaning mechanism is automatically triggered to further enhance the protection effect.
A complete quality inspection and verification system is an important guarantee to ensure that moisture-proof and dust-proof performance meet the standards. During the production process, air tightness test, salt spray test, wet heat aging test and other methods are used to simulate extreme environments to test the relay. For example, the sealing performance of the shell is tested by a helium mass spectrometer leak detector, and the electrical performance under different humidity conditions is tested using a constant temperature and humidity chamber; before the product leaves the factory, a long-term reliability test is also carried out to verify the effectiveness of the packaging process and protection strategy to ensure that the product meets industrial application standards.
The packaging process and moisture-proof and dust-proof performance improvement of signal pcb relay is a systematic project that requires the coordinated innovation of comprehensive material science, process technology and testing methods. With the development of technologies such as 5G and the Internet of Things, the reliability requirements for relays are constantly increasing. In the future, the packaging process will develop towards higher precision and stronger protection, such as the application of nano-level packaging materials and the research and development of intelligent self-healing coatings, which will provide a solid guarantee for the stable operation of electrical control systems.
