HDI PCB are circuit boards designed to maximize surface component density, provide a breakout solution for ICs with a large number of closely spaced pins or pads, and/or propagate high frequency signals. The aim is to provide greater functionality in a smaller package. To achieve this, you need to select a contract manufacturer (CM) that has the equipment and expertise needed to achieve the specialization required for HDI PCB electronics manufacturing. In order to optimize the manufacturing of HDI designs, you should follow a clear path or design techniques that combine your design intent and the capabilities of your CM.
Design skills for HDI PCB circuit board electronic manufacturing
PCB layout design can be very complex, thus requiring the designer to make difficult decisions regarding which specification to assign the greatest importance to. The process is even more complex if the design is for a critical systems industry such as aerospace, medical device, automotive or automotive manufacturing. military, or for high performance Internet of Things (IoT) or HDI. Regardless of the type of board design, when designers use design for manufacturing (DFM) in conjunction with a strategy that benefits PCB development and aligns with its CM capabilities.
DFM is not universal. This is a set of rules and guidelines for a specific manufacturing stage, such as Design for Assembly (DFA) and Design for Testability (DFT). DFM can also specialize in specific board design types, such as HDI. Let's look at some important design tips aimed at optimizing the manufacture of HDI PCB electronics.
1. Select via type to minimize process complexity
Via selection is a critical decision that not only determines the equipment and fabrication steps required, but also affects processing time and additional cost. The use of blind or buried microvias helps reduce layer count and material cost; however, the choice of whether to use in-pad, dog-bone, or near-pad vias affects process complexity.
2. Select the minimum number of components to apply HDI
Component selection is always important. However, component selection optimization is more important for HDI boards. HDI designed components determine drilled and stacked trace widths, locations, types and sizes. Obviously, performance is the primary consideration, but packaging, traceability and usability should also be considered. Having to replace components or redesign layouts can incur additional manufacturing time and material costs.
3. Spatial components minimize stress and EMI
When components are placed such that via locations are distributed asymmetrically, uneven stress may be applied to the board, which may cause warpage. This can seriously impact yield, the number of boards that can be used per panel. If components are spaced from dense, high-power components, the signal can introduce electromagnetic interference (EMI) into the traces, affecting signal quality. Additionally, parasitic capacitance and/or inductance from nearby pins or pads may affect signal quality. Therefore, it is recommended to include EMI modeling during design to extract parasitic effects.
4. Route traces to minimize signal integrity issues
One of the advantages of HDI is the ability to use smaller trace widths for signal propagation. Despite the reduced trace width, it should be designed for optimum width signal integrity. This includes using the shortest trace lengths, consistent path impedance, adequate ground planes, and digital, analog, and power signal isolation.
5. Choose stacking to minimize material cost
In addition to the selection of vias, the choice of PCB stackup also has a significant impact on the manufacturing cost of HDI PCB electronics. The type of material and number of layers directly impacts the number of lamination and drilling cycles required. When making these decisions, cost should be one of the deciding factors.
Following the tips above for HDI PCB electronics fabrication will help your CM make the process as efficient as possible. However, making HDI boards is not done once and for all. To learn how design and manufacturing can be integrated, check out the following DFM for HDI case study.
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