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How Low Can We Go?
August 20, 2008 |Estimated reading time: 5 minutes
When manufacturing printed circuit boards (PCBs), designers might attribute the cost of production to factors in the manufacturing process, possibly believing they are exempt from the cost-reduction process. However, according to Happy Holden, program director in the System Design Division for Wilsonville, OR-based Mentor Graphics, this is an incorrect assumption. In fact, designers have the capability to reduce the cost of circuit boards in a number of ways.
As part of IPC's technical seminars during National Electronics Week in London, on June 17, 2008, Holden outlined key strategies to reducing costs in his presentation, "S02: Designing PCBs for Lowest Cost-Reducing Layers and Other DfM Principles." This article is based on Holden's recommendations outlined in his presentation.
First-Pass Yields
Designers first need to understand the design determines the cost, not purchasing nor the fabricator. The designer's specifications go into the blueprint. Consequently, "the majority of the cost is in everything they create," Holden says, adding that it involves much more than just the blueprint.
Approximately 75% of the cost of a PCB rests solely on the design, and it's the largest variability in PCB production cost based on the manufacturing yield, Holden says. By analyzing a first-pass yield (FPY), designers can predict the end yield before the board is built and make modifications as necessary to select the design features that result in a higher yield, resulting in lower costs.
Holden says designers should work with fabricators during these preliminary stages to ensure fabricators understand how complex the boards are before production begins. If the complexity is too high for a fabricator, designers can also modify their design as needed after receiving a complexity index analysis, another useful tool for potential fabricators.
The complexity index is the key variable by which a designer can know if a manufacturer will be able to produce a board of a given complexity level. If, after receiving the data, it becomes clear that the design is too complex, the designer can modify the number of layers or make other adjustments to the design to ensure the highest yield from the fabricator, or make arrangements to select a capable fabricator.
Materials
With materials being the second largest cost driver in manufacturing PCBs, selecting new, more affordable materials can also have a dramatic effect on the cost of production.
Most designers aren't familiar with the growing number of high-quality materials found in Asia. They typically cost less than those in North America, Holden says. In the past 10 to 15 years, the size and scope of Asian manufacturers has increased greatly; as such, many Asian companies now sell materials such as copper top laminate, the single largest manufacturing cost for a bare board, to companies in North America and Europe. Designers should be aware of all of the options, a simple step that can result in significant cost savings.
Fabrication and Layer Reduction
After designing a PCB with high yields and affordable materials, designers should take additional, often simple steps to ensure the PCBs are manufactured without error. In the documentation, for instance, designers should refrain from using company terms, jargon or slang that can be lost in translation if the PCBs are to be produced in Asia. Designers' files and artwork should also be as clean, clear and concise as possible to save time in the broader manufacturing process.
If layers in the files are not properly aligned, fabricators can, for example, waste a considerable amount of time "cleaning up" the data, thus losing money. By performing a design rule check (DRC), designers can verify that their production data is correct before beginning the manufacturing process. If the fabricator makes mistakes that result in scrap or if the PCBs are delivered late, the fault - and financial loss - will also fall on the designer, Holden says.
By taking proactive measures to ensure production instructions and data are accurate and complete, money, time and frustration can be saved. Designers can further drive down the cost of the board by creating PCBs with fewer layers. By working with the new ball grid array (BGA) fanout patterns, designers can effectively reduce the size of the BGA on the board by routing it with fewer layers.
Fabricator Capability
By analyzing fabricator capability, designers can also save on manufacturing costs by avoiding companies that are more expensive because of errors and lost time. By using tests such as the IPC-9151 benchmarking program, designers can save time and hassle. If a chosen fabricator is incapable of producing a board, "the potential yield loss is going to result in a very high price," Holden says. Selecting a fabricator that can handle the complexity of a design can help ensure high yields and fewer errors, all of which contribute to a lower cost.
Asian Fabrication
Designers can also continue to drive down the cost of manufacturing looking worldwide for a manufacturing partner. Volume is the No. 1 cost driver when creating a PCB, Holden says.
A growing number of manufacturers worldwide have begun implementing unique production techniques that allow manufacturers to produce a low-volume board while still keeping costs in check by mixing low-volume boards on one panel to create a higher overall production volume. For instance, a designer might have four boards with an annual usage of only 10,000 to 20,000. But by placing them all on one panel, as some manufacturers are permitting, the order quantity would increase to 40,000 to 80,000. Partnering with fabricators that allow a designer to increase the inherent volume on a board creates significant savings.
By implementing some or all of the above cost-saving strategies, designers can save their organizations a considerable amount in the price of manufacturing. By taking responsibility for the design, they can be empowered to make financially beneficial decisions for their company, Holden says.
If you are interested in reading more about Happy Holden's thoughts on steps designers can take to reduce the cost of production, be on the lookout for his upcoming PCB blog at http://www.mentor.com/.
Olivia Leigh is a contributing editor with IPC. This article originally appeared on the IPC Web site.