The keep out and routing layers establish the same constraints for a PCB design. Running the electrical wire through stud walls requires a consistent approach to the depth and height of the wiring path.
#Allegro change layer item in xsection image install#
Must Follow Rules: Keep Out and Routing LayersĪn electrician installing electrical wiring in a house must follow rules to ensure that the wire will not have sharp bends or become vulnerable to the nails or screws used to install drywall. The accuracy and detail included in those documents lessens the opportunity for any errors in the design process. Other documents include the Bill of Materials, Gerber data, CAD data, the schematic, fabrication drawings, notes, assembly drawings, any test specifications, any quality specifications, and all regulatory requirements. Because the process of “printed circuit assembly” connects the functional components to the traces on the PCB, the assembly process requires that design teams focus on signal management, thermal management, pad placement, the relation between electrical and mechanical assembly rules, and if the physical mounting of a component matches mechanical requirements.Įvery PCB design requires assembly documentation like that found in IPC-2581. The assembly information controls the mounting and location of the electronic components. Physical dimension lines, dimension markings, datasheets, cut-out information, vias information, tooling information, and assembly instructions not only describe the mechanical or dimension layer but also serve as the measurements for the PCB foundation. Matching the thickness and length for differential signal pairs solidifies the stability and integrity of the circuit-especially for high frequency signals.ĭetermining your circuit board’s size and shape is pretty important to get at the beginning of the design In terms of the ground and power planes, the quality of the copper layer impacts the impedance of the ground plane and the thermal conductivity of the power plane. Different weights and thicknesses of copper impact the ability of a circuit to achieve the correct amount of current flow and define the amount of loss. While the copper as a conductor seems obvious, other functions exist. PCB stability depends on the consistent impedance of the dielectric over the entire plane and the consistent impedance over a wide frequency range. As we build complex PCBs that handle high-speed signals, the dielectric materials isolate the signals found on adjacent layers of the PCB. The materials used as dielectrics provide two basic functions for the PCB.
Every PCB Needs a Good Foundation: Assembly Instructionsįoundational aspects of a PCB include the dielectric material, copper, and trace dimensions along with the mechanical or dimension layer. Much like a house, a printed circuit board too needs a strong organizing principle. Drywall, paint, finish lumber create layers of aesthetic appeal that transform the shell of the house into a home. The organization of the house and the layered approach also sets up routing for electrical, HVAC, and plumbing services. After a crew completes the rough work, tar paper and shingles provide another layer of protection on the roof. A layer of sheeting also goes onto the outside stud walls and-as with the roof trusses-adds more stability. Sheeting overlays the trusses and adds cover while establishing structural stability. Then, the trusses can fit on top of the stud walls. Once a construction team receives the plan and lays the foundation, they can build the stud walls and establish the cut-outs for doors and windows.
Building a house requires a very organized, layered approach. Imagine trying to build a house from the roof down instead of from the foundation up.
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