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Semi-Flex PCB

by: Nov 21,2019 9206 Views 10 Comments Posted in PCB Basic Information

Introduction:

Traditional rigid-flex PCB materials include rigid materials and flexible materials. The current production method is usually to carry on the pattern plating for the rigid substrates and flexible substrates, and then laminating the rigid substrates and flexible substrates together by using the adhesion agent. The materials of the adhesion agent are usually made of non-flowing prepregs. Flexible materials are expensive and costly to make. At present, the cost of multilayer rigid-flex PCB is 5-7 times of that of the traditional multi rigid PCB, which limits the development of rigid-flex PCB.

At the same time, compared with the rigid materials, the changes of flexible materials which will always change with the change of the size are much bigger. The inconsistency of expansion and contraction may lead to the circuit patterns’ dislocation of the same size rigid materials and flexible materials when laminating, which will reduce the reliability of the products.


Semi-Flex PCB:

The most traditional manufacturing process of semi-flex PCB is adopting the bending FR-4 materials and making PCB according to the traditional rigid PCB manufacturing process, and then using the deep milling technology to thin the areas that need to be bended so that it has a certain degree of flexibility, so as to meet the requirements of assembly bending connection.

Main Characteristics of Semi-Flex PCB:

① Low Cost:

Semi-flex PCB technology, using epoxy resin FR-4 material, first in accordance with the normal process of PCB processing, and then through depth milling selectively reduce the thickness of the traditional multi-layer material, so that it has a certain degree of flexibility. Compared with the production of double-side PCBs and multilayer PCBs, this method only has one more manufacturing step, and the processing process is relatively simple. It can reduce the cost by replacing expensive polyimides and other flexible materials, and can significantly reduce the cost compared with flexible PCBs and traditional rigid-flexible PCBs.

② High Reliability:

The semi-flex PCB is used in the automotive and electronics industry, so it has strict requirements. When the final assembly requires the PCB board to stack, the semi-flex PCB can not only reduce the cost, but also reduce the welding point and the entanglement of connectors, with the characteristics of components can be mounted in the same state, the same plane. After the assembly is completed, the flexible part can meet the requirement of bending to the final shape without using the flexible substrate, which overcomes the reliability problem caused by inconsistent expansion and contraction of the flexible substrate and the rigid substrate, thus improving the reliability of the electronic product system.

③ Special Installation Performance:

Semi-flex PCB is a kind of PCB that can be locally bent on the basis of rigid PCB, which can not only provide the support of rigid PCB, but also achieve local bending according to product requirements, including the bending in 45゜, 90゜, 180゜, meeting the installation performance requirements of various types of 3D assembly, shown as below.

Conclusion:

Semi-flex PCB products are mainly used in automotive electronics, large machines, data communication and other fields, and can meet the requirements of high system reliability, low installation time, low installation cost and three-dimensional installation required by today's substrate installation interconnection to the greatest extent. On the basis of the rigid PCB, through special processing method, realizes the partial flexible performance. Compared with the traditional sense of the rigid-flex PCB, semi-flex PCB has not only significantly reduced on the material cost, manufacturing cost and the difficulty of manufacturing process, but also can satisfy the requirement of local bending installation of a certain number of times. At the same time, semi-flex PCB can provide a more stable, complete electrical signal transmission performance, which can partially replace some application of the rigid-flex PCBs. The application of semi-flex PCB will be greatly promoted under the background of the rapid development of rigid-flex PCB market.



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  • I would like to see some design guidelines that PCBWay needs to process a semi-flex PCB.

    PCBWay Support Team 2020-05-13 09:31:48Reply

    Now we don't have it, but thanks for your suggestion. We will be working on this.

    Guang Ning 2022-08-18 11:32:21Reply

    Latest NewsPCBWay can manufacture semi-flex boards

    Skyler Olsen 2022-09-27 22:41:27Reply

    Are there any design guidelines posted?

    Engineer 2024-11-22 00:10:03Reply

    Hi PCBWay,

    Is there any advance on this topic? I would like to order a semi-flex PCB manufacturing, and will really appreciate sharing of a guidelines - how the flexible area shall be designated in KiCAD.

    Thanks

    PCBWay Team 2024-11-22 09:40:15Reply

    Semi-flexible boards are mainly used for three-dimensional installation. It is recommended that the ink should be special ink for soft boards, which is not easy to crack. It is recommended to control the depth of one side, and the excess thickness is 0.2+/-0.05mm. We can only bend 1-2 times at present. If you want to bend 2-3 times, it is recommended to apply a covering film, so that it is not easy to break. The bending degree is 90-180°. You can design normally in other aspects, and there is no limit on the board, number of layers and thickness.

    PCBWay Team 2024-11-22 09:41:49Reply

    https://www.pcbway.com/helpcenter/ordering_parameter_instruction/What_is_Semi_Flex_PCB_.html

    Reply
  • What is the minimum bending radius that can be achieved and the minimum thickness of the bending section of a Semi-Flex PCB? Are they comparable with the minimum bending radius (of about 2mm) and thickness of a 0.13mm thick flex part of a rigid-flex PCB?

    PCBWay Team 2023-11-30 10:50:55Reply

    The formula for the minimum bending radius of a semi-flexible board is R=W*T. Single-panel W is 6. Double-panel: W is 12. Multi-layer board W is 24. T is the board thickness. This is a rough calculation formula. The minimum bending radius is Not less than 1.60mm. For the minimum bending radius (about 2mm) of the 0.13mm thick flexible component of the rigid-flex PCB, based on 0.5oz copper thickness, the bending radius is R1.0mm and the minimum thickness is 0.1mm.

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