Fuse Wire Welding Failure: Fracture Analysis At 1.2 Times Rated Current

In power protection systems, the stability of fuses directly affects circuit operation. Under certain operating conditions, the weld joint of a drop out fuse fuse may break when the current is less than 1.2 times the rated current. This abnormal open circuit phenomenon is not an overload meltdown, but rather an early failure caused by welding process defects or thermal stress concentration.

Thermomechanical Fatigue at the Weld Joint

The connection quality between the fuse and the end cap determines the current conduction impedance. When there are defects such as incomplete welds, slag inclusions, or poor wettability at the weld joint, the local contact resistance will increase significantly.

• Local Temperature Rise Effect: Current passing through the high-resistance weld area generates abnormal Joule heating.

• Thermal Stress Cycling: The temperature gradient created by equipment start-up and shutdown causes creep in the solder.

• Intermetallic Compound Brittleness: An excessively thick IMC layer formed at the weld interface reduces the joint's vibration resistance.

This structural damage can lead to physical stress fracture before the current reaches the melting threshold.

Production Factors Affecting Reliability

The selection of fuse material and the matching of welding parameters are crucial. During the production process, fluctuations in welding pressure or uneven cooling rates can lead to internal microcracks. These microcracks gradually propagate under long-term load.

Environmental factors also accelerate the fracture process through thermal expansion and contraction. Prolonged exposure to vibrational environments or corrosive atmospheres significantly reduces the mechanical strength of damaged weld points.