HDI PCB Circuit Board Factory
Minimum Line Width : 3MIL ;
Minimum Line Spacing : 3MIL ;
Drilling Diameter : ≥ 0.1mm ;
Surface Technology : Gold deposition, Gold plating, Tin spraying, OSP ;
Processing Size : 600 * 1200mm ;
Plate Thickness : 0.1-10mm ;
Processing Layers : 2-36 layers.
HDI circuit board factory learned that today's PCB circuit boards everywhere, daily contact with cell phones, computers, household appliances, toys, etc., dismantle the mechanical structure, there are large and small, a variety of functions inside the circuit board. PCB is the most important carrier of basic electronic components and chips, so the merits of PCB design also directly determines the final performance of the product. In this paper, through a practical case, to analyze the basic composition of the circuit board and the main design process of the PCB. The basic composition of the circuit board of the current circuit board, mainly composed of the following:
Line: the line is done as a tool for conduction between the original, in the design of the design will be additionally designed as a large copper surface grounding and power supply layer.
Dielectric: Used to maintain the line and the insulation between the layers, commonly known as the substrate hole (Through hole / via): Through hole can make more than two levels of the line with each other through, the larger through hole is made for parts plug-in, in addition to non-conductive holes (NPTH) is usually used as a surface mount positioning, fixed screws when assembling the solder-proof ink (Solder resistant / Solder Mask): not all copper surface to eat tin on the parts, so non-tin-eating areas, will print a layer of copper surface to eat tin substances (usually epoxy resin) to isolate the copper surface to eat tin. resistant /Solder Mask): Not all copper surface to eat tin on the parts, so non-tin-eating areas, will be printed a layer of copper surface to isolate the material to eat tin (usually epoxy resin), to avoid non-tin-eating short circuit between the lines. Depending on the process, it is categorized into green oil, red oil, and blue oil.
Legend /Marking/Silk Screen: This is a non-essential structure, the main function is to mark the name of each part on the circuit board, the location of the frame, to facilitate the assembly of the maintenance and identification with.
Surface Finish: Because the copper surface in the general environment, it is easy to oxidize, resulting in the inability to tin (solderability bad), so it will be in the copper surface to eat tin to protect. Protection methods are spray tin (HASL), gold (ENIG), silver (Immersion Silver), tin (Immersion Tin), organic solder protection (OSP), the method has its own advantages and disadvantages, collectively referred to as surface treatment. As shown in the figure, the left side of the pad is immersion gold, the right side of the pad after spraying tin.
PCB design process PCB design of the main process is about the following ten steps, including hierarchical design and other steps are not necessarily necessary, with the size of the company's requirements and the complexity of the design.
a, Mainly from the completion of the schematic design output netlist, and then layout and wiring, followed by simulation, dealing with the power supply ground EMC and other thermal management, and finally output documents and quality management processes.
b, Schematic Design: Before starting the whole board design, you need to complete the schematic design first.The schematic is a logical representation of the circuit, including the connection and function of each component. Ensure that the schematic design is accurate to avoid problems in the whole board design.
c, PCB Layout Planning: Before PCB layout, you need to plan the size of the entire board, component layout, connection methods and so on. Considering the signal integrity, power distribution and heat dissipation and other factors, rationally arrange the location of each component and alignment path.
d, Hierarchical Design: For complex circuit board designs, a hierarchical design approach can be used to separate the signal, power and ground layers for different functions. This helps to reduce signal interference and improve overall performance.
e, Signal Integrity: Ensuring the integrity of high-speed signals is a critical point in PCB design. Taking measures such as proper differential pairs, matching transmission line lengths, and reducing signal returns can reduce signal attenuation and timing offsets.
f, Power and Ground: Special attention should be paid to the layout and connection of power and ground in the design. Ensure power supply stability and low impedance of the ground line to reduce power supply noise and signal interference.
g, Thermal Management: For components that require high power, such as processors and amplifiers, heat dissipation needs to be considered. Reasonable layout of heat sinks and heatsinks to ensure adequate space and ventilation to avoid overheating and causing failure.
h, Design of Pads and Holes: Choose the appropriate size and shape of pads and holes to suit the components used and the soldering process. Ensure the quality and reliability of pads and holes to minimize soldering problems and connection failures.
i, EMI/EMC Design: Electromagnetic compatibility is an important consideration in PCB design. Reduce electromagnetic interference and radiation through appropriate shielding, grounding, filtering and other measures to ensure that the product complies with relevant EMI/EMC standards.
j, Documentation Output: In the PCB design process, mark and record in a timely manner. To each component, connecting lines, levels, etc. for appropriate marking, write a detailed design document to facilitate subsequent debugging and maintenance work.
Design specifications and standards: follow the relevant PCB design specifications and standards, such as IPC standards, to ensure the reliability and manufacturability of the design. The actual design case assumes the design of a PCB card based on the ARM platform.
The General Idea of PCB Design:
a, Grab the module and arrange the components by module. Arrange the module can be an understanding of the whole board. You can learn what needs to be paid attention to on the board. Such as what are the important signals, as well as the entire board of a power distribution direction. Module capture is completed after the start of the layout.
b, After the layout is completed, plan the stacking of layers. The number of layers on this board is determined by the DDR4 part. I chose to go with a FLYBY topology. So it can only be a six-layer board with eight false layers. The whole board needs to control the impedance of the signal line DDR4 USB HDMI and so on.
c, Set the rules, start the line. First from the main chip BGA start line, will DDR4 line first completed. DDR4 and the main chip pull line is completed, you can first look at the memory winding whether there is a bottleneck. the DDR signal is the most, and the rate is high, more sensitive, is the pre-design of the most important need to focus on the assessment of the local. Then start the wiring of peripheral devices, USB HDMI high-speed line to pay attention to the impedance continuity and spacing control, the network port part of the attention to lightning, audio part of the need to pay attention to the analog ground and digital ground division and so on. Power part of the alignment should pay attention to the size of the current, towards.
d, After the completion of the alignment, the beginning of DDR4 winding, differential pairs of equal length, FLASH and RGMII winding.
5, the final adjustment of the entire board, mainly dealing with screen printing checks, text processing. After checking, the GBR will be released.
e, Finally, the whole board is adjusted, mainly dealing with silkscreen checking and text processing. After checking, output GBR.