Rigid Flex PCB design

Description

The designs of Rigid Flex PCBs are a little more complex as these boards are designed in 3D, which allows the board to be folded or twisted to create the desired shape for the product. Designing a board in 3D means they can offer greater spatial efficiency and can subsequently be used in special instances where space and weight reduction may be necessary, such as in medical devices. By being able to design in three dimensions designers can twist, fold and roll the flexible board substrates to achieve their desired shape for the final application’s package.

Rigid Flex PCBs are usually thinner than other boards, meaning it’s a great option for any thin or light packaging needs your products may have. With thin copper layers and adhesive-less laminates, it’s a great small, thin and light solution for your circuit design needs.

Rigid-Flex PCBs Fabrication Applications:

Rigid-Flex PCBs offer a wide array of applications, ranging from smart devices to cell phones and digital cameras. Increasingly, rigid-flex board fabrication has been used in medical devices such as pacemakers for their space and weight reduction capabilities. The same advantages for rigid-flex PCB usage can be applied to smart control systems.

In consumer products, rigid-flex doesn’t just maximize space and weight but greatly improves reliability, eliminating many needs for solder joints and delicate, fragile wiring that are prone to connection issues. These are just some examples, but Rigid-Flex PCBs can be used to benefit nearly all advanced electrical applications including testing equipment, tools and automobiles.

Rigid-Flex PCB and Its Production Process

The development of FPC and PCB has spawned a new product that is called rigid-flex PCB. Therefore, rigid- flex PCB is according to the relevant process requirements and through the lamination process to combine rigid board and flex board to form a circuit board with FPC characteristics and PCB characteristics.

Because rigid-flex PCB has a variety of complex structural forms, the manufacturing process is also different. Below picture shows the regular rigid-flex PCB and an example for regular stack up design.

Rigid flex PCB stack up

Rigid flex PCB production is based on below steps: the first step is to process the rigid outer cover layer. The electroplating graphic that needs to be pressed in the outer layer, and then through the CNC milling machine, punching or laser method, routing out or routing the half of depth of the flexible part which is located in rigid layer. Flex board and the rigid outer cover are boned by adhesive sheet. The adhesive sheet has been pre-opened in the flexible part.

During the lamination process, if the rigid outer layer uses routing structure, a suitable pressure filling board should be prepared for the flex part. Using a vacuum pressing machine to obtain better press quality, and meanwhile with some auxiliary coating materials, such as PE, etc., so that the pressing process can provide a uniform pressure on the entire board, and make the low -flowing sticky sheet is fully flowing and filling the gap, especially for complex structures. Before adhesion or lamination, appropriate baking should be done as needed to remove moisture.

After lamination, the rigid- flex PCB can use a through hole treatment process which is similar to a multi-layer rigid board, the different part is remove drilling dirt. The method of removing drilling dirt depends on what materials used. Like the rigid board, drilling the hole after fully baking, and then use the plasma etching process to remove the residue in the hole wall. Before the plasma is treated, bake is also needed to remove water vapor. Caval polyesterness is generally recommended to not exceed 13um. The pore -plating process of conventional rigid board can be used, but the specific process parameters of the electroplating should be determined according to the reliability test data of the pores.

The next process is similar to the multi -layer rigid board. The outer layer etching, covering membrane (welded film), surface treatment, etc. can be used in similar processes. When making outline of the rigid-flex PCB, remove the filling board in the flexible part or depth control rigid outer cover in the flexible area can be formed into a rigid-flex PCB.
Careful consideration of Rigid-Flex solutions and a proper assessment of the available options at the early stages in the rigid-flex PCB design phase will return significant benefits. The Rigid-Flex PCBs fabricator must be involved early in the design process to ensure the design and fab portions are both in coordination and to account for final product variations.

The Rigid-Flex manufacturing phase is also more complex and time-consuming than rigid board fabrication. All the flexible components of the Rigid-Flex assembly have completely different handling, etching, and soldering processes than rigid F