Cost Per Unit for Flexible Printed Circuits
The unique capabilities of flexible printed circuits (PCB) to flex and conform to mechanical packages enable the transmission of signals across significant distances without interruption. However, the advanced manufacturing process that enables this flexibility also comes with an inherent cost premium versus rigid PCBs. Understanding the key factors that impact flex PCB costs early in the design stage can help avoid sticker shock later on. This article explores the variables like layers, order volume, board size, flex circuit thickness, materials, tolerances and more that determine total flex PCB cost.
The most important factor that drives flexible printed circuit cost is the number of conductive copper layers. Each additional layer adds to the total fabrication cost due to the need for dielectric adhesive material between each layer of etchable copper.
For this reason, higher layer count flex PCBs are generally more expensive than lower layer count boards. In addition, high reliability flex PCBs may require advanced hole technology like blind vias and microvias which add to the overall cost through the use of more costly specialized materials and extra steps in fabrication.
What is the Cost Per Unit for Flexible Printed Circuits?
Rigid-flex PCBs are more expensive than traditional rigid or bare circuit boards because of the complexity involved in making them. Rigid-flex PCBs combine dissimilar materials with different stability characteristics, and they use special techniques such as no-flow prepregs and thicker polyimide films. Manufacturing yield is often lower than for traditional rigid and bare circuits, which adds to the cost.
Stiffeners and shielding in flex PCBs also contribute to higher manufacturing costs. These features reinforce the flexible structure, reducing tearing and facilitating bending of the PCB, but they increase fabrication complexity and materials cost. It’s critical to analyze parts that require stiffening and carefully select the correct material. Shielding is also an expensive option that should be used sparingly.
As with rigid PCBs, the choice of base material has a major impact on flex PCB cost. Thicker, more thermally robust materials like kapton and fluoropolymer film add to the cost while thinner, more conductive materials such as PET offer a cost savings.
The finish selection is another key driver of flex PCB cost. Choosing a more affordable tin lead or HASL plating can significantly reduce the overall cost. The final assembly process of the flex circuit is also an important factor that contributes to overall cost.
The smallest size flex PCBs are typically more expensive than larger boards, but the cost per unit drops significantly in volume production runs. Similarly, higher layer counts and dense layouts drive up the price of flex PCBs as they require more complex copper layers, greater fabrication accuracy and more handling.