In the manufacturing of electronic devices, PCB prototyping is a crucial process. PCB prototyping refers to the fabrication of a small number of prototype circuit boards for testing and validation before large-scale production. This stage is a critical step to ensure product performance and reliability. Therefore, understanding the concept of PCB prototyping and the challenges involved is of utmost importance. This article will introduce what PCB prototyping is and delve into ten challenges in the process.
What is PCB Prototyping?
PCB prototyping is the process of producing a small number of prototype circuit boards before mass production. These prototype circuit boards are manufactured based on circuit design files and engineering drawings. The purpose of PCB prototyping is to verify the correctness of the circuit design, ensure that the performance meets the requirements, and check for potential issues. Once the prototypes have been tested and validated, the project can proceed to the large-scale production stage.
Ten Challenges in PCB Prototyping
- Unclear definition of processing hierarchy in PCB prototyping. For single-sided board designs, without specifying the top or bottom side, it may result in difficulty in soldering even if the board is fabricated and components are mounted.
- Insufficient distance between large copper areas and the board’s outline. Large copper areas should have a distance of at least 0.2mm from the board’s outline to avoid issues like copper foil warping during milling and causing problems with solder mask adhesion.
- Using fill areas to draw solder pads in PCB prototyping. While using fill areas for solder pads might pass the Design Rule Check (DRC) during circuit design, it doesn’t work during fabrication. Such solder pads cannot directly generate solder mask data, and when applying solder mask, the area covered by the fill area will make component soldering difficult.
- Contradictory arrangements for power planes in PCB prototyping. When the power planes are designed as fill areas, the ground plane on the actual printed board is the reverse image. All traces become isolated lines, so caution should be exercised when drawing multiple power or ground isolation lines to avoid creating gaps that might cause short circuits between power planes.
- Disordered placement of characters in PCB prototyping. Overlaying characters on solder pads or SMD pads causes inconvenience in testing and component soldering. If the characters are designed too small, it becomes challenging for silk-screen printing, while too large characters might overlap, making them difficult to distinguish.
- Solder pads on surface-mounted devices (SMDs) are too short. For continuity testing, the distance between two pins of densely packed SMDs is quite small, and the pads are also quite thin. When installing test probes, they must be staggered up and down. If the solder pads are too short, it might not affect component installation but can cause misplacement of test probes.
- Setting hole sizes for single-sided solder pads. Single-sided solder pads generally do not require drilling holes, but if holes are required, they should be specified with a size of zero. Designating numerical values for hole sizes will create hole coordinates in the drilling data, leading to issues. If drilling is needed for single-sided solder pads, it should be specially indicated.
- Overlapping solder pads in PCB prototyping. During PCB prototyping, drilling at one location multiple times can cause broken drill bits, resulting in damaged holes. In multilayer boards, overlapping two holes will appear as an isolated pad on the film, causing scrapping.
- Excessive use of fill areas or using extremely fine lines for fill areas in PCB prototyping. This can result in lost data during the photomask generation, leading to incomplete photomask data. As fill areas are drawn line by line during photomask data processing, it increases the data processing difficulty significantly.
- Excessive use of graphic layers in PCB prototyping. Adding unnecessary lines on certain graphic layers, designing more than five layers for a four-layer board, causing misunderstandings, and violating conventional design practices. During the design, graphic layers should be kept complete and clear.
PCB prototyping is an indispensable step in the manufacturing of electronic devices, ensuring product performance and reliability. However, PCB prototyping also faces numerous challenges, such as design accuracy, material selection, thermal management, and more. Understanding and addressing these challenges are key to successful PCB prototyping. High-quality PCB prototyping can save time and costs and lay a solid foundation for large-scale production. Therefore, designers and manufacturers must pay close attention to these challenges during the PCB prototyping process to ensure the quality and competitiveness of the final product.
