A look at variables that influence board price.

How does one calculate the actual cost of fabricating a printed circuit board?

Naturally, each PCB is different from another, and the cost of creating one will vary depending on the PCB’s dimensions, number of layers, complexity and many other factors. Several basic variables must be considered and applied generally to the process.

Remember that PCB manufacturing is, at the very least, a sophisticated process that involves state-of-the-art technology and skills to meet the requirements of high-tech industry’s performance parameters. Of course, all these procedures cost money in practice. From design to manufacturing, mutual understanding and coordination among all stakeholders should result in a high-quality PCB product at an appropriate cost.

Figure 1. PCB costs are impacted by everything from layer counts and surface finishes to trace widths and technologies levels.

At Rush PCB, we believe in the proverb that “a stitch in time saves nine”; i.e., doing things right from the outset saves time and money because rework costs time, material and, of course, money, bringing up the cost per piece. Our focus has always been to educate customers about these aspects without compromising the performance and reliability of the product. That “stitch” in the PCB manufacturing industry is the right approach. We encourage customers to invest some time, since the right approach can minimize PCB cost.

Some of the major factors contributing to the cost include:

• Layer count
• Laminate type (material)
• Via technology (PTH, microvia, filled via, buried via, etc.)
• Size of the PCB (panel yield = number of finished boards per panel)
• Base copper weights in different layers
• Line/space in different layers
• Pad sizes and PTH to Cu clearance
• Aspect ratio and number of holes
• Surface finish.

Materials. When selecting a material for a design, similar materials may be priced differently depending on the location and supplier. The number of layers will impact PCB cost, as well. That cost, however, is continuously changing with advancements in materials and manufacturing technology. As a reference, a typical PCB pricing scheme is shown in Table 1.

Table 1. Production Pricing Guide for an 18″ x 24″ FR-4 Panel

Among various PCB fabricators, board material costs are often about 20% of the total bare board fabrication cost. Pricing can be influenced by additional technology, layer count or material volume. Prices may also vary depending on stackup construction. For example, Material A may be on average cheaper than Material B, but some specific glass or thickness of Material A may be sold at a higher price than Material B, thereby increasing the overall Material A price.

Wiring density. High-density interconnect (HDI) circuit board designs have a higher wiring and pad density than conventional PCBs, along with smaller trace widths and spaces. They require advanced PCB technologies such as blind vias, buried vias and microvias. HDI PCBs are usually more expensive than conventional PCBs due to the complex buildup process involved in their fabrication.

Although HDI PCB fabrication can be expensive, there are several instances where blind vias, buried vias and microvias can offer a cost-effective solution. Replacing through-hole vias with blind vias and microvias can reduce the layer count and board size thanks to higher routing density. Those vias typically require laser instead of mechanical drills, but the cost of laser is primarily in the setup, not so much the number of microvias (e.g., drilling one or 100 microvias would not impact cost significantly).

Understanding the board size, and how many copies can be made from a single panel (“pieces up”), can help identify cost-saving opportunities. The designer should consider efficient panelization at an early stage when there may be flexibility with board shape/size.

Other price contributors or “adders” include geometry, surface finish, etc. (Table 2).

Table 2. Typical PCB Price Contributors

Design technology level. PCB design rules can be classified into different technology levels. We classify them as high-tech, mid-tech and low-tech. Each one applies to specific suppliers, and each follows standard or advanced rules.

Standard rules are available at all the strategic fabricators within a respective technology level, and provided these values are not exceeded, there should not be any additional cost adders. Advanced rules may incur additional costs and may not be available from all fabricators. It is good engineering practice to use the most relaxed rules possible, even if there is no cost penalty, and only push the limits into advanced rules or more aggressive technology when necessary. The rules will be periodically updated.

Additional adders. Other cost adders include:

• Embedded components
• Electrolytic gold
• Mixed surface finishes
• Via-in-pad-plated-over (VIPPO)
• 100% edge plating.

Selective edge plating may add cost. The criteria for finishing between edge plating and unplated laminate edges will influence the cost.

Akber Roy is chief executive of Rush PCB Inc., a printed circuit design, fabrication and assembly company (rushpcb.com); This email address is being protected from spambots. You need JavaScript enabled to view it..