The engineer designs the protection scheme according to the protection grade of the product, and then selects the protective equipment. After selection, the electronic protection equipment will be installed after arrival. Taking the polymer self-recovery fuse provided by Shuokai Electronics, an agent of Shunhai Technology, as an example, the installation precautions of the self-recovery fuse are explained in detail as follows.
Precautions for installation of polymer PPTC self-recovery fuse: Avoid large mechanical stress on device chip.
Analysis: Polymer PTC devices will be accompanied by the thermal expansion of the polymer itself. Under certain installation conditions, if both ends of the device chip are subjected to great pressure, extrusion, distortion and bending, the thermal expansion phenomenon will be limited. Then the electrical function of the device will be affected, and the protection device may not be protected under fault conditions. In the initial design, the designer should consider leaving a certain space around the protection device chip.
Precautions for installation of polymer PPTC self-recovery fuse II: Avoid chemical pollution of equipment.
Analysis: Some types of oils, solvents, oils, fuels, industrial cleaning chemicals, colloidal volatiles, silicon-based oils and electrolytes may have negative effects on equipment performance, which designers should consider when using.
Precautions for installation of polymer PPTC self-recovery fuse III: Precautions for welding.
Analysis: When wave soldering or reflow soldering is needed, the specified operation flow should be followed.
When it is necessary to use spot welding (resistance welding) to connect with the terminals of polymer PTC devices, in order to ensure the electrical performance of PTC devices, the spot welding points should be controlled to be more than 2mm at the edge of the chip, and the welding spatter must be guaranteed not to contact the PTC chip. And the welding conditions will not heat the PTC device beyond its maximum temperature.
When manual welding is required, avoid over-high welding temperature and heat PTC equipment to a point exceeding its maximum working temperature. Meanwhile, the welding time should be controlled. Strict welding process operation specifications shall be stipulated for operators.
Precautions for installation of polymer PPTC self-recovery fuse 4: Avoid short circuit of non-encapsulated devices.
Analysis: When using unpackaged PTC devices, if there is conductive device contamination between the edge of PTC devices and the fixer. Such as metal chips or tin balls. May lead to oxidation and combustion failures.
Precautions for installation of polymer PPTC self-recovery fuse V: Other precautions.
Analysis: Operation exceeding the maximum rating of the equipment or improper use will lead to equipment damage, and may lead to electric fox or burning. The device is suitable for protection against accidental overcurrent or overtemperature fault. Failures should not occur repeatedly or last too long.
Conclusion: Self-recovery fuses can be used in electronic products such as computers and their external equipment, mobile phones, battery packs, telecommunication and network equipment, transformers, industrial control equipment, automobiles, etc., and play an overcurrent or overtemperature protection role.
