Rigid Flex PCB Manufacturing
Rigid flex circuits combine the benefits of rigid and flexible printed circuit boards (PCB). They offer high performance, miniaturization, and reliability, while providing flexibility for mounting components in smaller electronic devices. By eliminating contact crimps, solder joints and connectors, rigid-flex PCBs have fewer points of failure during operation and are more compact and lightweight. This increases device reliability while reducing manufacturing costs.
As an alternative to a multi-layer, traditional rigid flex circuit boards design, rigid-flex circuits are manufactured in a single layer and use plated through holes (PTH) for interconnects between the rigid and flexible sections of the board. By combining rigid and flex circuits in this way, the design process can be significantly simplified. This leads to faster turnaround times, improved quality and lower production costs.
Flexibility is crucial for many applications where the flex circuit will be dynamically flexed during normal product operation. This flexing may occur over hundreds of thousands of cycles or more. In order to achieve the appropriate level of flexing for the application, a rigid-flex circuit must be designed with specific trace widths and spacing, proper bend radii, and stress relief features. These design rules must be adhered to during the fabrication process to ensure signal integrity, manufacturability, and reliability.
Standards for Rigid Flex PCB Manufacturing
There are a number of standards that provide guidance on designing and manufacturing rigid-flex circuits. These include IPC-2223, IPC-6013D, and IPC-6013C. These standards provide guidelines for materials selection, design rules, and fabrication processes. They also specify testing and inspection requirements.
In addition to adhering to these standard, there are other design considerations that should be kept in mind when creating a rigid-flex circuit. For example, copper traces should not be routed at sharp angles because they will strain the circuit and reduce its lifespan. Instead, it is a good idea to create round or teardrop-like shapes for the traces and pads. Similarly, vias should be located away from areas of the flex circuit that will bend because they are at a higher risk for cracking and peeling under stress.
Another important design consideration is the coverlay layer, which protects the flex circuit and provides an adhesive for component mounting on the rigid section. The coverlay can be created using several methods, including photo-imageable solder mask or a conventional silkscreen. A photo-imageable coverlay can be cured with UV light to create a permanent solder mask. This eliminates the need for secondary masking and allows for fast production of rigid-flex circuits.
Rigid-flex PCBs can be used in a variety of applications, such as consumer electronics, medical devices, and automotive, aerospace and military equipment. The versatility of this technology makes it a viable option for manufacturers that require the flexing and mounting capabilities of a rigid-flex circuit with the added benefit of a thin, durable outer shell. In the future, rigid-flex will likely become the standard in many industries as designers seek to increase functionality and efficiency of electronic devices with minimal space. For this reason, it is critical for manufacturers to understand the construction and benefits of rigid-flex PCBs in order to make informed decisions about the best construction techniques for their products.
