Every PCB needs a good foundation: assembly instructions

The basic aspects of PCB include dielectric materials, copper and trace sizes, and mechanical layers or size layers. The material used as the dielectric provides two basic functions for the PCB. When we build complex PCBs that can handle high-speed signals, dielectric materials isolate the signals found on adjacent layers of the PCB. The stability of the PCB depends on the uniform impedance of the dielectric on the entire plane and the uniform impedance over a wide frequency range.

Although it appears that copper is obvious as a conductor, there are other functions. Different weights and thicknesses of copper will affect the ability of the circuit to achieve the correct amount of current and define the amount of loss. As far as the ground plane and the power plane are concerned, the quality of the copper layer will affect the impedance of the ground plane and the thermal conductivity of the power plane. Matching the thickness and length of the differential signal pair can consolidate the stability and integrity of the circuit, especially for high-frequency signals.

The physical dimension lines, dimension marks, data sheets, notch information, through hole information, tool information, and assembly instructions not only describe the mechanical layer or the dimension layer, but also serve as the basis of the PCB measurement. The assembly information controls the installation and location of electronic components. Since the “printed circuit assembly” process connects functional components to the traces on the PCB, the assembly process requires the design team to focus on the relationship between signal management, thermal management, pad placement, electrical and mechanical assembly rules, and component The physical installation meets the mechanical requirements.

Every PCB design requires assembly documents in IPC-2581. Other documents include bills of materials, Gerber data, CAD data, schematics, manufacturing drawings, notes, assembly drawings, any test specifications, any quality specifications, and all regulatory requirements. The accuracy and detail contained in these documents reduces any chance of error during the design process.

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Rules that must be followed: exclude and route layers

Electricians who install wires in the house must follow rules to ensure that the wires do not bend sharply or become susceptible to the nails or screws used to install the drywall. Passing wires through the stud wall requires a consistent way to determine the depth and height of the routing path.

The retention layer and the routing layer establish the same constraints for PCB design. The retention layer defines physical constraints (such as component placement or mechanical clearance) or electrical constraints (such as wiring retention) of the design software. The wiring layer establishes interconnections between components. Depending on the application and type of the PCB, wiring layers can be placed on the top and bottom layers or internal layers of the PCB.

01
Find space for the ground plane and power plane
Each house has a main electrical service panel or load center that can receive incoming electricity from utility companies and distribute it to circuits that power lights, sockets, appliances, and equipment. The ground plane and power plane of the PCB provide the same function by grounding the circuit and distributing different board voltages to the components. Like the service panel, the power and ground planes can contain multiple copper segments that allow circuits and subcircuits to be connected to different potentials.

02
Protect the circuit board, protect the wiring
Professional house painters carefully record the colors and finishes of ceilings, walls and decorations. On the PCB, the screen printing layer uses text to specify the location of components on the top and bottom layers. Obtaining information through screen printing can save the design team from quoting assembly documents.

The primers, paints, stains and varnishes applied by house painters can add attractive colors and textures. In addition, these surface treatments can protect the surface from deterioration. Similarly, when a certain type of debris falls on the trace, the thin solder mask on the PCB can help the PCB prevent the trace from shorting.