The role of the insulator is to make contact to maintain the correct location arrangement, and make contacts with the contact, the contact between the parts and between the shell insulated from each other. Therefore, insulation must have good electrical properties, mechanical properties and molding process performance. With the widespread use of high-density, small terminal block, the effective wall thickness of the insulator is increasingly thin. Insulation materials, plastic injection molds, precision molding process more restrictive and burdensome requirements. Due to the reason of the insulator surface or within the metal of extra material, surface dust, flux and other contamination from moisture, organic material precipitates and harmful gases adsorbed film and the surface water film fuse to form ion conductive channels, moisture absorption, mold, insulation material aging, will cause a short circuit, leakage, breakdown, insulation resistance and low insulation undesirable phenomena.
   
Not only insulation insulator, usually protruding contacts to provide accurate and protection, also have to install positioning, locking on the device's function. Fixed bad, the light of reliable contact caused by momentary power failure, the disintegration of a serious product. terminal block of a dissolution of the terminal block in the state of mating, due to the materials, design, craft and other reasons led to the power structure is not reliable between the plug and socket, the normal separation between the pin and jack, it will cause the control system transmission and signal control of the serious consequences of the interruption. Unreliable due to the design, material selection errors, the molding process to select improper heat treatment, mold, assembly, welding process is of poor quality, the assembly is not in place will result in fixed bad.
   
In addition, because the coating from the skin corrosion, bumps, molded case fly side, rupture, contact rough machining, deformation causes the appearance of non-performing terminal block due to the positioning locking with the size of ultra-poor processing quality, consistency, and the total separation the force is too large and other causes of bad swap, is also a common disease. These types of failures are generally able to test and use timely detection removed.