Bobbin, is the main structure of transformer, which provides winding space for copper wire in transformer and fixed core in transformer.

The selection of transformer skeleton should consider the following aspects:

(1) A ready-made skeleton of the same type and different specifications in shape;

(2) There must be a reasonable gap between the core and the core;

(3) The wall thickness of the insulated part of the coil conductor shall not be less than 0.64 mm;; and

(4) The supporting plate structure supporting the weight of the transformer and the fixed pin shall have sufficient mechanical strength to withstand impact, collision, welding without breaking or deformation;

(5) There shall be clear positioning marks and product marks on the skeleton, which shall be in the corresponding parts specified;

(6) PBT the skeleton, pin and skeleton of the material are formed once in injection molding, and the pin should be designed to prevent the stripping structure in the inner part of the skeleton (large head, bending, knurling, etc);

(7) The needle must be of sufficient strength and rigidity, while ensuring weldability, generally using a rigid CP line, the coating may be silver or tin cerium alloy, the thickness of the coating should be greater than 0.07 mm;; and

(8) The number of pins in the transformer and the process slot are determined according to the requirements of the switching circuit. The center distance between the pins is generally designed to be 5 mm, In order to make the installation error-free, the distance between foot 1 and foot 2 can be increased to 7.5 mm. 3.2 The selection or design of the framework of the switching transformer is different from the framework of the general transformer. In addition to being the insulation and supporting material for the coil, it also assumes the installation and fixing function of the whole transformer. Therefore, in addition to meeting the insulation requirements, the materials for making the skeleton should also have considerable tensile strength and impact resistance. In order to withstand the welding heat of the pin, the thermal deformation temperature should be higher than 380, and the flame retardant and easy to process. Ideal material to meet the above requirements is switch transformer skeleton special PBT plastic and wood powder. The shape of switch transformer skeleton is vertical. That is, the pins are at one end of the core, when the height is limited, there is also a horizontal, that is, the core