Ensure Dimensional Stability in Rigid Flex
When it comes to designing rigid flex, the key is to consider your application and the environment you plan on putting it in. It’s also important to ensure that your design has enough mechanical strength to withstand any stress it may encounter during use. The right materials will make this easier to do. Rigid flex boards are often created from FR-4 glass epoxy laminate, thermoplastic polyimide (TPU), or FR-4 glass epoxy laminate with polyimide. These materials are all designed to resist high temperatures and mechanical stress. FR-4 is the most cost-effective and reliable option, while TPU and polyimide offer greater resistance to high temperature and electrical degradation.
When selecting the right material, it is also important to consider how the board will be fabricated. The fabrication process for rigid flex is different from other PCBs. It requires more complex copper layers, and it is crucial to take care of layer transitions in order to avoid signal degradation.
Rigid flex is also more sensitive to moisture than other PCBs. The moisture can affect the integrity of the copper layers and lead to corrosion. This can have a significant impact on performance and reliability. In addition to affecting the quality of the circuit, this can also increase the cost of your final product.
How to Ensure Dimensional Stability in Rigid Flex
Whether you’re using a flexible or rigid flex PCB, you should always use a fully qualified manufacturing partner to ensure that your product is up to par. Low-quality PCBs are not only more expensive than their counterparts; they can also create safety hazards, which can result in damage to your device or injury to its users.
Aside from the above considerations, there are a few other things to keep in mind when designing for rigid flex. For example, it is important to ensure that the rigid and flexible portions of your board terminate at hardboards. If you have a design that requires rigid portions to terminate into a flex portion, this can lead to abrasion between the two components and may damage your device.
The design of rigid-flex PCBs involves the strategic placement of rigid and flexible sections to optimize performance and durability. Rigid sections provide structural integrity, enabling the mounting of heavier components or connectors, while the flexible sections offer adaptability, allowing the circuit to bend, twist, or fold into compact spaces. This capability is particularly valuable in applications where space is at a premium or where the circuit must endure mechanical stress during operation.
To prevent this, you should use a beading process to protect the connection points on your flex arms. This involves adding solder paste to all the pads, placing them in a vacuum chamber, and laminating a film onto each pad. This will prevent abrasion between the rigid and flex portions of your circuit and help reduce EMI. Additionally, it is important to maintain balance and symmetry in your design. Out-of-balance designs are more difficult to manufacture and will introduce more points of failure during assembly and operation.
