Are you starting a design and contemplating whether to use a rigid-flex construction or to move forward with multiple rigid boards and wire/cable connections? Using a rigid-flex concept to replace the traditional approach of using cable assemblies to join two or more rigid boards has clear benefits: reduction in space and weight, more design freedom in packaging, reliability, and increased current carrying capabilities. But the rigid-flex approach is often perceived as too expensive to justify the change. It is true, when comparing the piece price of a rigid board and wire harness concept to a rigid-flex, rigid-flex can appear more expensive. I challenge you to dig a little deeper and do a comparison of the total cost of both a rigid-flex solution and a PCB and wire solution.
Where do you start? The following list is not intended to be an all-inclusive list of items to consider, because every application is unique, but it is intended to be used to help facilitate a discussion amongst your team to really dive into the review of total cost rather than just the PCB cost.
Items to consider when comparing the total cost of each approach:
Cost of design:
Let’s start with the cost of creating the design itself. With a rigid PCB and cable solution, multiple rigid PCB designs and multiple cable assembly designs are often required. When moving to a rigid-flex solution, you merge those designs into a single part number. The cost of creating each design and managing each part number should be calculated and included in the total cost analysis between each option.
Cost of cable and connectors:
Again, it is common for a cost comparison to compare the cost of the rigid board with the cost of the rigid-flex and discount the rigid-flex solution as too expensive. I recommend a more detailed discussion of all the components involved in each option. The rigid-flex pricing should be compared not just to the cost of the PCB, but also to the cost of the connectors, wire and cable, wire markers, shrink tubing, cable ties, fasteners, and freight for all of those items that are being replaced by the rigid-flex design.
Cost of the assembly operation:
As with factoring in the costs of the individual PCB designs required for a PCB and wire harness solution, the cost of assembling multiple rigid boards needs to be taken into consideration. A rigid-flex solution requires only one assembly while the PCB/cable solution can require two, three, or even more individual boards to be assembled. The total cost of those multiple assembly processes needs to be reviewed. These costs may include: the cost of kitting for assembly, labor, in-process inspection, cable assembly test, final test, PCB tooling and test, and the costs associated with the engineering time required for each of these operations.
Cost of testing:
Following the examples above, the cost of assembly of each solution needs to be considered. The rigid-flex solution not only requires only one testing operation but also provides the ability to test the full assembly prior to installation.
Cost of order processing:
The cost of order processing is a component of total cost that is often overlooked. As a recurring theme, a rigid-flex solution requires processing just one order for that part number while a PCB and cable solution will require the processing of multiple part numbers. Each of these items has costs associated with purchase order generation, receiving and incoming inspection, material handling and storage, and payment processing.
The rigid-flex solution is considered a high-reliability alternative to the PCB/cable solution. Reliability is something that is difficult to quantify but is incredibly important in the review of the total cost. With a rigid-flex design, the flex, as a connector between rigid boards, becomes an integral part of the board; there are no solder connections between boards and no human element to be introduced when connecting the various rigid boards. With a rigid-flex design, the reliability is dependent on good design and rigid-flex tooling rather than dependent on the assembly operation.
Logically, it is easy to agree that working with a single rigid-flex design rather than the multiple components of a PCB/cable solution does simplify things. The big question becomes, does it save enough time and lower costs enough to justify the transition to rigid-flex technology?
As mentioned, this list is not intended to be all-inclusive, there are just too many variables in rigid-flex design. The intention of this blog post is to spur conversation and a more holistic view of total costs when thinking of introducing a rigid-flex design as a solution to a packaging challenge. Rigid flex technology is a growing segment of the PCB market. Designers are challenged to include increasingly complex electronics in increasingly smaller packages and the SWaP (space, weight, and packaging) benefits are hard to deny. My hope is that this blog post generates discussion of total cost rather than simply PCB cost and allows designers to justify the transition to rigid-flex PCBs to help solve today’s challenges and take advantage of rigid-flex technology.
Would you like to find out more about how Altium can help you with your next PCB design? Talk to an expert at Altium.
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