(1) Poor contact
The metal conductor inside the terminal is the core part of the terminal, which transmits the voltage, current or signal from the external wire or cable to the corresponding contact of the matching connector. Therefore, the contacts must have excellent structure, stable and reliable contact retention and good electrical conductivity. Due to the unreasonable structural design of the contact parts, the wrong selection of materials, the unstable mold, the excessive processing size, the rough surface, the unreasonable surface treatment process such as heat treatment and electroplating, improper assembly, poor storage and use environment and improper operation and use, the contact parts will be damaged. Contact parts and mating parts cause poor contact.

(2) Poor insulation
The function of the insulator is to keep the contacts in the correct position, and to insulate the contacts from each other, and between the contacts and the housing. Therefore, the insulating parts must have excellent electrical properties, mechanical properties and process forming properties. Especially with the widespread use of high-density and miniaturized terminals, the effective wall thickness of the insulator is getting thinner and thinner.
(3) Poor fixation
The insulator not only has the function of insulation, but also usually provides protection for the protruding contacts, and also has the function of installation and positioning, and the function of locking and fixing it on the equipment. Poorly fixed, the light one affects the reliability of the contact and causes an instant power failure, and the serious one is the disintegration of the product.