When designing a flex PCB stackup, the fabricator might face some restrictions in enhancing the reliability of the board. Today, we will discuss ways to improve the reliability of a board by increasing the flexibility and improving design considerations of a multilayer PCB stackup. These steps can be implemented for PCB stackup designs as seen in 8 layer flex PCBs.
Improve Flexibility by Reducing Overall Thickness
You can execute all or some of the below mentioned steps to lower the overall thickness of the PCB. A thinner PCB stackup will allow it to be more flexible.
- Reduce the base copper weight.
- Reduce the adhesive thickness.
- Reduce the dielectric material thickness.
- Use adhesiveless base materials, which can reduce the thickness of the substrate by 1-2 mils, which is almost 25-50 μm.
- Make use of selective plating to avoid copper plating the conductors.
Improve Reliability by Reinforcing the PCB
Here, the boards, components, and the layout should be designed to deliver a robust structure that can withstand flexing.
- The weight on both sides of the PCB should be equal. This includes the weight of the conductors and the material.
- The conductors on different layers of a PCB should not be placed on top of each other. Instead they should be placed in a staggered pattern. (Please refer image below)
- Conductor thickness should always be constant in and near the bend areas.
- There should be no plated-through holes in the bend areas.
- For slits in the circuit, reliefs or tear stops need to be built into the PCB.
- There should be no discontinuities near the bend.
- Traditional copper can prove to reduce the flexibility of a PCB. Opt for screened-on coatings like silver epoxy.
Tight tolerances will have to be put in place to ensure that your stacked up PCB can provide flexibility as well as reliability. Several of the above-mentioned steps can easily be incorporated in the designing process itself. Your PCB manufacturer should be able to help you with the most appropriate improvements for your application.Visit our website www.rigiflex.com to know in detail about 8 Layer Stackup Flex.
