While designing a new PCB, it is necessary to adhere to design basics. If neglected, it will result in a poor board design that will be very difficult to manufacture. Therefore, it is necessary to pay attention to the following concepts:
Choose appropriate components and package sizes
As a board designer, you should thoroughly study the BOM and examine the parts that go into the design. When there is sufficient space on the board, you may opt for larger components for resistors and capacitors. It is beneficial to use a 0603 or 0805 size capacitor/resistor instead of a 0402/0201. Select the smaller package version of the component if you have spacing issues. Moreover, choose your appropriate component and package based on the required current, voltage, and frequency.
Smaller components are manufactured by various vendors. It allows designers to choose alternate parts without modifying the schematic or layout, providing a timely solution for components that are not in stock.
Furthermore, it is crucial to decide the appropriate size of the package during the PCB design phase. It is recommended to choose smaller packages only when necessary; otherwise, choose larger packages. Using too many small component packages can create issues during circuit board assembly, which leads to difficulties during cleaning and reworking.
Avoid long lead-time components
The unavailability of components can cause considerable delays. So, it is better to check the availability while confirming component spacing. If your component has a long lead-time, order it immediately. It can be beneficial to have alternate components with the same footprint. Assembly vendors can also procure the widely available parts so that every component will be readily available when it is time to assemble the boards.
Schematic checks
A schematic is a well-structured circuit diagram that represents the electrical connections between various electronic components. Schematic design basics often get ignored. Make sure you verify the following:
- Verification of pin numbering and labels in component symbols
- A polarity check for all the polarized components
- Overlapping labels and Pins
- Ensuring the base, collector, and emitter pins according to the schematic symbols, datasheet, and footprint package
- Validation of the component value, location, and reference designators
- Descriptions of the schematic symbols
- Off-page connectors
- Checking the inter-sheet reference
- Decoupling capacitor check for all ICs, ground pin separation according to the signal type (analog, digital, signal, ground)
- Netlist check for design correctness and wrong connections
- Add test points to all important signals
- Test points are required to check the electrical conductivity of the board. It is necessary to add test points for all important signals to facilitate electrical tests (E-test) and in-circuit tests (ICT). Keep an eye on the following:
Board side: If possible, all test points should be located on the same side of the board to facilitate testing.
Minimum test point distance: The minimum distance between test points is 0.100 inches. It maximizes test effectiveness.
Test point distribution: Distributing test points evenly on a circuit board makes testing easier with multiple probes.
Area for taller components: Designating the area for taller components can streamline the testing.
Manufacturing tolerances: Make sure to consider manufacturing tolerances while designing a layout to accommodate a space for test points.
Make sure your BOM is up to date while designing
A BOM is a detailed list of all the components required to produce a product. Keep your BOM up to date while designing, and if you make any changes to your design, ensure you have also implemented those changes in your bill of materials. For example, if you change the part number in the schematic, update the BOM as well. Before you validate your BOM file, ensure that all the active parts are included in it. The parts should be validated with respect to the following fields:
- Serial number
- Part description
- Designators matching the schematic
- Quantity of the parts
- MPN
- VPN
- DNI (do not install) components
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