Increasing the Financial Efficiency of HDI Boards

Increasing the Financial Efficiency of HDI Boards

Optimising Costs for High-Speed HDI PCBs

In the world of High-Density Interconnect (HDI) Printed Circuit Boards (PCBs), cost is a significant factor that needs careful consideration, especially in high-speed digital applications. The key drivers that influence the cost of HDI PCBs can be broken down into seven key areas.

1. Layer Count: More layers require additional build-up cycles, lamination, and alignment processes, increasing the cost significantly.
2. Via Structures: The use of microvias, blind and buried vias, especially stacked microvias or via-in-pad designs, demands precision drilling, plating, and inspection, which adds to the cost.
3. Material Selection: Using specialized, low dielectric constant (low-Dk), low dissipation factor (low-Df) materials to maintain signal integrity at high frequencies raises material costs but is critical for high-speed performance.
4. Surface Finish Types: Higher-quality finishes like ENIG or hard gold improve solderability and durability but increase expenses.
5. Manufacturing Complexity and Process: HDI PCBs require advanced manufacturing methods such as laser drilling, sequential lamination, and precise imaging. This drives up production costs due to equipment, time, and expertise needed.
6. Signal Performance Optimisation: Efficient stackup design using carefully selected materials directly influences electrical performance, requiring a balance between cost and functionality.
7. Order Volume: Larger production volumes reduce per-unit cost; prototypes or small runs are comparatively expensive due to setup and process overhead.

In addition to these factors, managing impedance control and minimising crosstalk also influence design complexity and cost, though they were not explicitly outlined in the sources.

To optimise HDI PCB costs while meeting high-speed application requirements, early collaboration with manufacturers is recommended. This collaboration can help simplify layer stackup, reduce unnecessary vias, select cost-effective yet high-performance materials, and optimise order volume.

Steve Arobio and Atar Mittal, directors of PCB manufacturing and PCB design respectively, advocate for the use of buried vias in HDI technology, arguing that it can lead to improved cost-effectiveness. However, when dealing with Ball Grid Arrays (BGAs) with a ball pitch of less than 0.5 mm, it is advisable to consult with a board manufacturer before commencing the layout.

When the three materials, Isola FR408HR, Nelco N4000-13 SI, and Panasonic Megtron 6, are compared, they each have their unique characteristics when used for HDI board designs, particularly in laser drilling. For instance, Megtron 6 incorporates a unique low-Dk fabric known as flat glass, unlike FR408HR and N4000-13 SI, in which resin resides throughout the glass fabric weave.

For 12-layer designs with tight hole-to-copper clearance, using HDI technology can result in improved yield and reduced manufacturing cost. If a customer needs another batch, maybe with a few changes but the same basic architecture, the shop would then adjust the price to compensate for the yield loss.

Lastly, it is worth noting that BT-Epoxy (Bismaleimide-Triazine Epoxy) is used in organic chip packages for better electrical properties along with thermal stability, but it is more expensive compared to epoxy resin.

In summary, the cost drivers for HDI PCBs in high-speed digital contexts are the number of layers, via complexity, advanced material and finish choices, intricate manufacturing processes, signal integrity requirements, and economies of scale in production. By understanding these factors and working closely with manufacturers, designers can create cost-effective HDI PCBs that meet the demands of high-speed digital applications.

1. To maximize cost efficiency in High-Density Interconnect (HDI) Printed Circuit Boards (PCBs) technology, it's crucial to manage controlled impedance and minimize crosstalk, factors that influence design complexity and cost, although not explicitly mentioned in the sources.
2. In the realm of HDI PCB technology, when considering different materials such as Isola FR408HR, Nelco N4000-13 SI, and Panasonic Megtron 6, their unique characteristics in relation to controlled impedance, particularly in laser drilling, significantly impact the overall cost of the project.

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