By Jeannie Chapman


PCB design services involve specialized activities aimed at creating an optimum printed circuit board layout using CAD software and other specialized PCB design tools. There are different kinds of PCBs and the process for each one may vary a bit. Regardless of the type of board or layout, though, it's always going to be roughly the same multi-stage designing process that begins with schematic capture.

At this point, it would be appropriate to note that the client is usually required to provide the designer with information about at least three basic aspects. One is the aforementioned schematic, although it may also be provided by the client as a netlist file. The netlist is simply a file that contains all the connectivity information for the design, along with descriptions of components used.

The client also has to provide the BOM (bill of materials) that lists all the components to be used and their footprints, although some designers also offer assistance with component footprint capture. Then there's also the board outline that must be provided. The outline, schematic/netlist and the BOM together constitute all the necessary information that will be used for designing the PCB.

Starting from the netlist/schematic, the process is taken further using techniques including library development, signal integrity and EMI checks, stress analysis, thermal simulation, etc. The series of intermediate steps ends with the creation of the gerber file. This format is the preferred one used by the electronics industry to transfer finished PCB images that are ready to be used in the manufacturing stage.

The designer must be capable of coming up with solutions for complicated analog, digital, RF and mixed PCBs. Then there's also the type of board, which can be single-sided, double-sided or multi-layered. The board's size may vary, and so can the pin densities and component quantities.

Another important thing that has to be decided in the designing stage is about the characteristics of the board. The most critical thing is deciding the technique used for creating traces and mounting components. The most widely used solution is surface-mount technology.

Using this surface-mount technique, the end caps are directly soldered now on the same side of the board. This new method has almost completely replaced the earlier through-hole boards. In these older boards, leads were inserted from one side of the board and soldered onto traces on the other side.

Apart from the schematic capture and subsequent board designing steps, the designer may also be called upon to evaluate existing designs, components and footprint captures. Sometimes they're also involved in prototype procurement, and may be asked to do availability checks and collect pricing information against the BOM.

There may, in fact, be other PCB design services required even after delivery of the end product. Customers often need to do minor changes to the design right away and on an ongoing basis, and reorders are also on the cards. Designers are sometimes asked to reverse engineer the process, starting with gerber files. Coming up with a netlist or schematic from a gerber file helps the client rebuild the circuit to implement large-scale changes.




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