Rigid flex printed circuit boards (PCBs) feature a hybrid circuit board design that combines the malleability of flexible circuits with the rigidity of hardboards. The resulting component is hard at some points and flexible at others, which allows it to be folded or flexed as needed to fit the electronic configuration.
Rigid flex PCBs are highly customizable; they can be designed and assembled to a variety of configurations, flexibilities and rigidities, and sizes to suit nearly any application. This factor allows them to be tailored to meet stringent system requirements. However, they must be carefully engineered and constructed to ensure they operate and perform as intended. Otherwise, they may cause issues within the equipment in which they are installed. For this reason, prototyping is a critical step in the rigid flex PCB production process.
Prototypes allow PCB fabricators to evaluate the functionality, performance, and quality of a rigid flex PCB design and determine if modifications and alterations are needed to comply with the necessary specifications and standards. By identifying any necessary changes before a design proceeds to the production stage, fabricators and customers will ultimately save time and money.
How the Rigid Flex PCB Prototyping Process Works
The rigid flex PCB prototyping process is similar to the actual rigid flex PCB production process; both processes entail creating a PCB based on a PCB design. However, unlike the production process, the prototyping process can involve many designs. As new rigid flex PCBs are typically unique to the system for which they are intended, board fabricators generally cannot reference past PCB designs for a suitable solution. As a result, they may develop a few different designs before finding the right combination of mechanical and electrical properties.
While the rigid flex PCB prototyping process may vary slightly from one project to the next depending on the production specifications, it generally involves the following steps:
- Initial Design Creation. The engineering team creates an initial design based on the specifications and requirements provided by the customer. Customers can make it easier for the team to create an initial design that meets their needs by providing as detailed information about their system and end goals as possible.
- Design Review. Once the team creates an initial design, they send it to the PCB fabricator for review. One of the most important aspects of this review process is determining all possible failure points of the design—i.e., how it may fail in the manufacturing process as well as in the end application.
- Customer Follow-Up. Once the design has undergone the review process, the team can bring it back to the customer. At this point, they can answer and address any questions or concerns the customer may have about the design and alter or add any elements the customer may request. While the latter can add to the overall lead time for the project, it is easier and cheaper to make any changes during the prototyping stage rather than in the production stage.
For a more comprehensive overview of the overall rigid flex PCB manufacturing process, check out this flow diagram.
Key Considerations for Rigid Flex PCB Prototyping
During a rigid flex PCB manufacturing project, there are many design and fabrication factors to consider to ensure you receive a product that fully meets your needs. An experienced and knowledgeable PCB fabricator can help guide you through the process. Their input and insight can help you find a balance between product design and product manufacturability, ensuring you receive a design that contains all of the elements you want and they have the capabilities to actualize it.
One of the main questions customers ask regarding the rigid flex prototyping process is “why does it take so long?” This question is particularly prevalent among customers who generally use rigid PCBs. While many rigid PCBs are available with lead times of 24 hours, quality rigid flex PCBs come with a minimum lead time of two weeks and a more reasonable lead time of four to six weeks. There are several reasons for these longer lead times, such as:
- Long bake cycles. When producing rigid flex PCB prototypes, the amount of time needed for the board baking alone can be days or even weeks when added together.
- Challenging design elements. The lead time for rigid flex PCB prototypes is highly dependent on the design. Many rigid flex PCB designs integrate challenging elements that increase the overall lead time for prototype production. For example, buried vias (design elements that connect the outer layer of the PCB to one or more inner layers) can add two to three weeks to the overall lead time, while bookbinding constructions (design elements that allow the PCB to bend at tighter angles) can add 12 weeks to the overall lead time.
- Extensive manufacturing evaluation process. Good PCB fabricators carefully evaluate prototypes to ensure the final product will operate and perform as intended. Some of the many things they may check include: 1) are the various elements on the board communicating with each other correctly? 2) is the impedance working correctly? 3) are the signals arriving at the chip at the right time?
While some PCB fabricators may boast about producing and delivering rigid flex PCB in two weeks or less, they often take shortcuts that can provide lower quality products. For industries with mission-critical applications (e.g., aerospace, medical, and military electronics), these quickly produced PCBs can lead to field failures. For this reason, it is essential to partner with a reliable PCB fabricator who will check all the boxes and do so thoroughly. While truly high quality rigid flex PCBs may have longer lead times, you can rest assured they will meet your specifications and industry reliability standards.
Rigid Flex PCB Prototyping at Printed Circuits
Rigid flex PCBs find application in a wide range of electronic devices and systems. However, they must be carefully designed and manufactured to ensure they operate as intended and perform as expected, which is why prototyping is an essential step in their manufacture.
Equipped with over 40 years of experiencing designing and constructing rigid flex PCBs and state-of-the-art manufacturing technology, Printed Circuits is the ideal partner for all rigid flex PCB needs. We can fabricate quality product solutions for nearly any customer need, including PCBs that comply with UL 94 V-0 and ISO 9001:2015 standards.
Have any questions about rigid flex PCBs or the rigid flex prototyping process? Reach out to us today.