Ultra-fine coaxial cable structure
The structure of the ultra-fine coaxial cable developed for mobile phones is that the center conductor is a 42AWG (7 / 0.025mm) concentric twisted silver-plated copper alloy wire, and the outer conductor of the horizontally wound package is (about 20 / 0.03mm) tin-plated copper Alloy wire. Both the insulating layer and the outer sheath are made of soluble polytetrafluoroethylene (PFA), because the fluoroplastic has a relatively low dielectric constant, which is suitable for high-frequency transmission, can reduce the influence of radiated noise, and can improve the flexibility of the cable itself.
Fig. Cross section photo of ultra-fine coaxial cable
Table. Structures of several common types of ultra-thin coaxial cables
Figure 4. Very fine coaxial structure
Copper alloy conductor
With the emergence of mobile phones with complicated structures such as sliders and two-axis rotary types, the requirements for bending resistance and twist resistance of ultra-thin coaxial cables on the rotating shaft have been greatly increased. The internal and external conductors of cables are required to be able to From the low deformation area (elastic deformation) to the high deformation area (plastic deformation), it must show good bending resistance.
Semi-rigid tin-indium-copper NN alloy wire (Cu-0.19mass% Sn-0.2mass% In), under the same drawing conditions, the bending life of this NN alloy wire is more than 10 times that of pure copper wire (TPC), In addition, this NN alloy is a solid solution alloy, has no impurities, has a very clean structure, and has excellent tensile properties.
The slab of the NN alloy wire is manufactured by the American Southern Wire SCR continuous casting and tying equipment. Low-oxidation technology is used during casting to suppress the oxidation of alloying elements, so it prevents wire breaks during extremely fine wire drawing due to impurities generated by oxidation of alloying elements. In addition, a sieve is installed during casting to filter out small impurities such as mixed refractory materials, which improves the quality of materials. In addition, through the dust-free management of the wire drawing production line, foreign matter is prevented from being mixed in during the wire drawing. And improved the intermediate heat treatment conditions and silver plating conditions.
Table 3. General characteristics of NN alloy wire
Note: Wire diameter Ф0.1mm
Table 4. Composition, electrical and mechanical properties of stranded conductors of NN alloy wire (silver-plated)
Note: AWG (American Wire Gauge)
5. Stranding, oblique wrapping and extrusion
WG (7 / 0.025mm) silver-plated copper alloy wire for the center conductor is generally twisted using a single twist twister with single twist twister, and its uniform wire tension and wire length are stable to twist. The essential.
The inclined shielded conductor between the insulation and the sheath uses a Spiral Shield Machine, which requires dozens of extremely thin wire high-speed inclined packages (3,000RPM). The requirements for the device's tension control capability are very strict. The requirements for electrical properties such as low dielectric constant and withstand voltage characteristics of thin coaxial cable insulation and outer sheath, as well as mechanical properties such as heat resistance and bending resistance at the end processing, the resin flow was selected during ultra-thin extrusion Good soluble polytetrafluoroethylene PFA. The cable insulation extrusion line is equipped with high-precision wire tension control equipment to ensure stability during mass production.