specify a flex circuit for manufacturing
The circuit base material for flex circuits is more critical than on rigid boards. The base material provides most of the flex circuit’s primary physical and electrical properties. This makes it extremely important to consider the choice of base material for your flex circuit when preparing your design for manufacturing.
For most flex circuit applications, polyimide is the preferred base material for its durability and reliability. Polyimide is a high-performance, non-conductive film with good thermal resistance and tensile strength. It is also tolerant of solder reflow cycles and is resistant to environmental contaminants. In addition, polyimide is very flexible and can be used as a shielding layer in flex circuit.
Depending on your application, you may need to add a layer of polyimide to the flex circuit as a shielding barrier to prevent electromagnetic interference (EMI). This is particularly true for high-density designs. EMI can cause your electronic circuit to operate incorrectly, and in some cases it can even lead to failure. The best way to avoid this is by including a shielding layer in your design.
How do you specify a flex circuit for manufacturing?
While a flex circuit can be bent in any direction, it is more durable and reliable when the bends are gradual rather than sharp. The more abrupt the bend, the more stress and damage to the copper can occur. Therefore, it is necessary to plan for a gradual bend in your flex circuit design.
It is also important to consider the operating environment for your flex circuit. Some environments are more harsh than others, and your flex circuit must be able to handle it.
Other factors to consider include the location and type of components. For example, you should not place sensitive components near each other because they will create interference. This can be a problem with standard parts that are commonly available, but it is much more of a concern when you are using custom parts.
Another factor to consider is the design of the traces and conductors in your flex circuit. You should stagger the traces in the top and bottom layers to minimize I-beaming, which can cause trace copper breakage. You should also route conductors perpendicular to the overall bend to minimize stress and breakage. Additionally, you should use tear guards to reinforce the flex material along the inside bend radius and eliminate tears. Finally, you should use rounded corners in the areas of the flex circuit that are expected to be bended as this will increase the durability and flexibility.
Finally, it is important to consider the layer count in your flex circuit. Although more layers usually increases the cost, it is a crucial consideration when it comes to flex circuits. You should consult your PCB/layout provider about the maximum number of layers that can be made without sacrificing durability and reliability.
