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PCB design buried technology is a dry high-density, high-capacity circuit board design of a new technology, this technology can be counted in the PCB manufacturing process is integrated into the copper foil layer, rather than as a stand-alone component installed on the surface of the circuit board. Through the use of special thin-film nickel alloy materials for plating, and according to the design needs through the etching of different shapes to achieve the required resistance value of the resistor. PCB buried resistance process is a PCB board buried inside the resistor process, to solve the traditional table stickers in the PCB in the problems encountered now, the PCB resistance is through the patch technology directly welded to the board surface, while the buried resistance process will be resistor embedded in the internal layers of the PCB board, the resistor will be embedded in the internal layers of the PCB board. Embedded in the internal layer of the PCB board, buried resistance PCB including the core board, buried resistance components and set in the core board in the inner layer of the line graphic, and so on. Application scenarios of the buried resistor process include pull-up and pull-down resistors, matching resistors, termination resistors, etc. in digital circuits. In RF and microwave circuits, buried resistance can be used for circuit matching, power distribution, and isolation. In addition, it is also suitable for current limiting and voltage-dividing resistors in photodiode circuits.
In the production process of the buried resistance circuit board, generally in the core board surface covered with a stencil structure, the stencil structure has holes, the conductive carbon paste will be filled into the preset holes in the stencil structure, to be cured by the conductive carbon paste to form a buried resistance element located on the surface of the core board, and then the buried resistance element is fixed to the core board to obtain the buried resistance circuit board. Such a PCB comprises, in order from bottom to top, a first dielectric layer, a buried resistor, a line layer, and a second dielectric layer, wherein a portion of the buried resistor on which the line layer is not provided is covered with a polymer isolation layer outside the buried resistor, and wherein the polymer isolation layer is roughened on the surface with a surface roughness Rz of greater than 0.01 μm, and the polymer isolation layer has a thickness of at least 0.1 μm in the corners. Advantages of the buried resistor process include space-saving, reduced circuit noise, improved signal integrity, and reduced PCB board thickness. However, the buried resistor process can be relatively complex to manufacture and maintain, as the resistors cannot be directly observed and replaced. In addition, buried resistors are typically used in high-end electronics and are relatively expensive to produce.
In buried resistor technology, the unit of resistance is usually expressed in “ohms per square”, abbreviated as “OHM PER SQUARE”. This represents the amount of resistance per unit area, rather than a fixed resistance value in the traditional sense. For example, if the resistance value of a material is 100 OHM PERSQUARE, a square resistor with a width of 1mm and a length of 1mm will have a resistance value of 100 ohms. If the dimensions become a rectangle 1mm wide and 0.5mm long, the resistance value will be 50 OHM. Based on this principle, resistors of specific shapes and sizes can be etched to meet the precise needs of a circuit board design.
Because buried resistor technology provides a smaller equivalent inductance and higher solder reliability, it is particularly well suited for aerospace and military applications where the performance and reliability of electronic components are critical. Although buried resistor technology has a history of more than 20 years, it has been mainly used in high-end applications because the initial high cost and maturity of the technology limited its wide application. However, as manufacturing processes continue to advance and costs fall, it is expected that buried resist technology will be more widely used in the future.
Advantages of the buried resistor process include:
1. Space saving: Since the resistors and capacitors are embedded directly into the internal layers of the board, it can save the space of the PCB board and make the whole board more compact.
2. Reduced Circuit Noise: Embedding resistors and capacitors into the internal layers of the board reduces the electromagnetic interference and sound of the circuit, and improves the stability and immunity of the circuit to interference.
3. Improve Signal Integrity: The buried resistor and capacitor process reduces the transmission delay and reflection loss of the circuit signal and improves the integrity and reliability of the signal transmission.
4. Reduced PCB board thickness: Since the resistors and capacitors are embedded into the internal layers of the board, the thickness of the PCB board can be reduced, making the entire board thinner and lighter.
However, the embedded resistor process can be relatively complex to manufacture and maintain, as the resistors cannot be directly observed and replaced. When it comes to high-density circuit design, the PCB-buried resistor process becomes a very useful technique. In traditional PCB layout, resistors are usually soldered to the PCB surface in the form of a chip. However, this layout method causes the PCB to take up more space and can cause noise and interference on the surface.
Detailed steps of PCB buried resistance process.
1. Make Internal Layers: In addition to the regular layers (e.g., outer, inner) when making a PCB board, there is a need to make separate internal layers specifically for buried resistors. These internal layers will contain the areas where the resistors are buried. The internal layers are usually fabricated using the same techniques as conventional PCB manufacturing, such as plating, etching, etc.
2. Resistor/Capacitor Packages: Resistors are packaged in special packages in the buried resistor and buried capacitor process in order to be embedded in the internal layers of the PCB. These packages are usually thinned to fit the thickness of the PCB board and have good thermal conductivity.