Special Circuit - Coil PCB - PCB Motor

Coil PCB is a component similar to an inductor made by drawing a coil directly on the PCB board with an alignment. Because this process has the characteristics of good voltage resistance, good consistency, flexible wiring and strong current carrying capacity, it is widely used in the antenna field.

Coil PCB manufacturing process

Wire Forming Technology

Photolithography and etching techniques are used to accurately build coil routes on the substrate.The process begins with the uniform application of photoresist on the surface of the copper-clad board, followed by exposure and development to precisely transfer the pre-designed coil pattern onto the resist. Then, the etching solution is used to precisely remove the excess copper foil, leaving only the designed coil traces. In the manufacture of high precision PCB coils, fine control of parameters such as exposure time,etchant concentration and temperature is essential to ensure that the width and spacing of the coil lines meet the design requirements, and to achieve line width accuracy control within ±0.05mm.

Layer pressing process

Multi-layer coil pcb,layer pressing is the core link. This step involves the completed line of the inner layer board, insulation layer and outer layer of copper foil, etc. in accordance with the established order of stacking, and then in the high-temperature and high-pressure environment for pressing, to promote the close combination of the layers. Typically, the lamination temperature is maintained at 170 to 200°C, the applied pressure is in the range of 200 to 400 psi, and the time required varies from 60 to 120 minutes depending on the thickness of the board and the number of layers. Ensuring that there are no air bubbles or delamination between layers during the lamination process is critical to maintaining the electrical properties and mechanical strength of the coil pcb.

Drilling and Copper Plating Process

The drilling step is designed to create through holes for electrical connectivity between the different layers. Once the holes are drilled, copper plating is applied, where a layer of copper is deposited on the wall of the hole to ensure that the through-hole has good electrical conductivity. The thickness of the copper plating layer is generally between 10 and 25 microns, and the hole diameter of the through-hole can be accurately controlled to within ±0.1mm. In the coil pcb manufacturing,the location of the through-hole and hole diameter accuracy for the coil and other circuit components of the reliable connection is critical, directly affecting the overall circuit performance.

Surface treatment technology

Common surface treatments include spray tin,immersion gold and OSP (organic solderability protection flux). Spray tin treatment can enhance the soldering performance of the coil pcb,immersion gold is known for its excellent oxidation resistance and contact resistance stability,while OSP can effectively prevent the copper surface oxidation within a certain period of time, to facilitate the subsequent welding and assembly operations. For example, in automotive electronics and other applications with stringent requirements for soldering reliability,immersion gold processing is more common,and the thickness of the gold layer is usually controlled between 0.05 and 0.15 microns.

Coil Planning

The shape of the coil, the number of turns, the width of the wires and the spacing between the wires are key factors that have a significant impact on the performance of PCB coils. Round coils provide a more uniform magnetic field distribution, while rectangular coils are more efficient in terms of space utilisation. The number of turns directly determines the size of the inductance value. As the number of turns increases, the inductance value increases, but correspondingly, the resistance also increases. The width and spacing of the wires are related to the current carrying capacity and the parasitic capacitance of the coil. For example, in the PCB coil design for wireless charging, in order to improve the charging efficiency, the number of turns and wire width of the coil need to be carefully planned in order to achieve the optimal balance between inductance value and resistance.

Hierarchical Design

Coil PCB may has single, double, or even multi-layer structures. Multi-layer structures can support more complex circuit connections and provide better electromagnetic shielding. For example, in the design of PCB coils for induction heating, a multi-layer structure allows the middle layer to be used to house the electronic control circuits and shielding, while the outer layer serves as the coil layer, which not only protects the internal circuits from external EMF interference, but also allows the magnetic field generated by the coil to be more concentrated, thus improving heating efficiency.

Performance Characteristics of Coil PCB

Inductance Characteristics

Inductance is an important performance indicator for PCB coils and is closely related to the number of turns, shape, wire width, spacing, and magnetic permeability of the substrate material. By accurately planning these parameters, it can be ensured that the inductance value of the coil meets the design requirements. For example, in the PCB coil design for RF circuits, where the accuracy of the inductance value is required to be very high, the inductance value can be controlled within ±5% of the design value by finely adjusting parameters such as the number of turns of the coil and the width of the lead wires.

Optimisation of quality factor (substrate Q material value,)

Coils

The design Q and value reflects the energy loss of the PCB coil in a resonant circuit. a higher Q value indicates lower loss and higher circuit efficiency. It is related to factors such as coil resistance, inductance, and parasitic capacitance. The Q value can be improved by using a low-loss fabrication process. For example, in PCB coil design for wireless communications, a high Q value helps improve signal transmission efficiency and reception sensitivity, and a Q value of 50 or more is generally required.

Frequency Response Characteristics

PCB coils perform differently at different frequencies. In high-frequency applications, special consideration needs to be given to factors such as the parasitic capacitance of the coil and the self-resonant frequency of the inductor. For example, in 5G millimetre wave band PCB coil applications, the structure and materials of the coil need to be optimised to ensure excellent performance at high frequencies, such as low insertion loss and high return loss, with insertion loss generally required to be less than 0.5dB and return loss greater than 10dB.

Electromagnetic compatibility (EMC)

PCB coil will produce electromagnetic radiation when working, and also may be subject to external electromagnetic field interference. Through reasonable layout design, shielding measures and grounding methods, it can improve its electromagnetic compatibility. For example, in some of the PCB coils in medical electronic equipment with extremely stringent requirements for electromagnetic compatibility, the use of multi-layer structure and the setting of shielding can effectively reduce the impact of electromagnetic radiation on the surrounding environment, while preventing external electromagnetic fields from interfering with the internal circuitry of the equipment.

Advantages and Applications of coil pcb in Component Replacement

Traditional Inductor Component Replacement

In many circuit designs,coil PCB can replace traditional discrete inductive components. PCB coil boards offer better integration than traditional inductors. For example, in the main board circuit of a mobile phone, multiple discrete inductors were originally needed to achieve different functions such as filtering and resonance operations. With PCB coil boards, these functions can be integrated on a single board, which saves space on the main board and facilitates the miniaturisation of the mobile phone's design. At the same time, the consistency of PCB coil boards is better because their production process is relatively standardised, unlike traditional inductors where individual differences may exist. When mass-producing electronic products, this helps to improve the stability and consistency of product performance and reduce debugging and testing costs.

Transformer Partial Function Replacement

In some low-power power conversion circuits, PCB coil boards are able to take on some of the functions of a transformer.It can achieve voltage conversion and isolation through special coil design and interlayer structure. For example, in some small USB power supply equipment, PCB coil boards can replace the traditional transformer, the input utility voltage is converted to DC voltage suitable for equipment use, and to a certain extent,isolate the input and output to improve the safety of the circuit. This substitution not only reduces the size and weight of the device, but also reduces the cost, as the production cost of PCB coil boards is relatively low for a certain scale of production.

Sensor Component Integration and Replacement

PCB coil boards can also integrate sensor components or replace some traditional sensor structures. For example, in some proximity sensor applications, detection of the proximity of metal objects can be achieved by designing special sensing coils and signal processing circuits on the coil PCB.Such integrated coil PCB board sensors offer faster response and higher sensitivity than conventional stand-alone sensors. In applications such as position detection on automated production lines, the position of objects can be detected more accurately, improving production efficiency and product quality.