There is no doubt that schematic creation and PCB layout are fundamental aspects of electrical engineering, and it makes sense that resources such as technical articles, application notes, and textbooks are often concentrated in these parts of the design process. However, we should not forget that if you do not know how to convert the completed design file into an assembled circuit board, the schematic and layout are not very useful. Even if you are a bit familiar with ordering and assembling PCBs, you may not know that certain options can help you get sufficient results at a lower cost.

I will not discuss DIY manufacturing of PCBs, and I cannot honestly recommend this method. Nowadays, professional PCB manufacturing is very cheap and convenient, and overall, the result is much superior.

I have been engaged in independent and low-volume PCB design for a long time, and I gradually gained enough relevant information to write a fairly comprehensive article on the subject. Nevertheless, I’m just a person and I certainly don’t know everything, so please don’t hesitate to extend my work through the comments section at the end of this article. Thank you for your contribution.

Basic schematic

The schematic is mainly composed of components and wires connected in a way that produces the desired electrical behavior. The wires will become traces or pour copper.

These components include footprints (land patterns), which are sets of through holes and/or surface mount pads that match the terminal geometry of the physical part. Footprints can also contain lines, shapes, and text. These lines, shapes, and text are collectively referred to as screen printing. These are displayed on the PCB as purely visual elements. They do not conduct electricity and will not affect the function of the circuit.

The following figure provides examples of schematic components and corresponding PCB footprints (the blue lines indicate the footprint pads to which each component pin is connected).

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Convert schematic to PCB layout

The complete schematic is converted by CAD software into a PCB layout composed of component packages and lines; this rather unpleasant term refers to electrical connections that have not yet been converted into physical connections.

The designer first arranges the components, and then uses the lines as a guide for creating traces, copper pouring, and vias. A through hole is a small through hole that has electrical connections to different PCB layers (or multiple layers). For example, a thermal via may be connected to the internal ground layer, and a ground copper wire will be poured into the bottom of the board).

Verification: Identify problems in the PCB layout

The last step before the start of the manufacturing phase is called verification. The general idea here is that CAD tools will try to find layout errors before they negatively affect the function of the board or interfere with the manufacturing process.

There are generally three types of authentication (although there may be more types):

Electrical connectivity: This ensures that all parts of the network are connected through some kind of conductive structure.

Consistency between schematic and layout: This is self-evident. I assume that different CAD tools have different ways to achieve this form of verification.

DRC (Design Rule Check): This is particularly relevant to the topic of PCB manufacturing, because design rules are restrictions that you must impose on your layout to ensure successful manufacturing. Common design rules include minimum trace spacing, minimum trace width, and minimum drill diameter. When laying out the circuit board, it is easy to violate the design rules, especially when you are in a hurry. Therefore, be sure to use the DRC function of the CAD tool. The figure below conveys the design rules I used for the C-BISCUIT robot control board.

PCB functions are listed horizontally and vertically. The value at the intersection of the rows and columns corresponding to the two features indicates the minimum separation (in mils) between the two features. For example, if you look at the row corresponding to “Board” and then go to the column corresponding to “Pad”, you will find that the minimum distance between the pad and the edge of the board is 11 mils.