Flex Circuit Design Guide
When it comes to designing a flex circuit design guide, the first step is to determine how much flexibility is needed. If the circuit is going to be static, like a rigid-flex board or a flex-rigid board in a handheld ultrasound machine, the layers and type of copper can be more liberally allowed than for dynamic applications that will see significant bending over the product’s life cycle. For example, it is acceptable to use double-sided flex boards with 2-layer constructions as long as the conductor traces are kept thin enough that they can handle the required number of bend cycles. For these types of dynamic flex applications, it is best to utilize rolled annealed copper, which has a higher ductility than RA copper and can better withstand the stresses of constant bending.
If the flex circuit is to be used in a dynamic application, it is essential that the bend radius and number of layers are closely reviewed by the mechanical engineer to ensure they are within acceptable limits. This will help prevent premature failure of the flex circuit due to over-stressing or straining. This can be done using the IPC 2223 formula for determining minimum allowable bending radii.
During the schematic phase, it is important to make sure that the drill-to-copper distance is not too small, which can cause unwanted stress during bending. Also, it is necessary to offset the conductors in the flex ribbon so that they do not all bend in the same direction. This will help to eliminate the concentration of stress that can cause solder joints to fail in the face of repeated flexing.
Designing a Flex Circuit Design Guide
For both dynamic and static flex circuits, the best way to avoid angular corners is to use a design tool that rounds off these corners during layout. This will not only minimize the potential for brittle conductors, but it will also help to keep the flex circuit’s appearance consistent and clean.
When designing a flex circuit, it is also critical to understand if the board will require panel plating or pad-only plating (button plating). In general, panel plating is preferred over button plating, as this allows manufacturers to control the amount of copper they deposit on each layer and improves etch yields for smaller traces. However, it can be difficult to achieve a low impedance in dynamic flex applications with pad-only plating, so button plating is often the best option.
A flex PCB is an excellent choice for many applications, as it can save time during assembly and can fit into tight spaces. With the right flex circuit design guide, it can also reduce the cost of production as it is more affordable than a traditional rigid-flex or rigid PCB. To find out more about the benefits of a flex circuit, contact one of the experts at BEST TECHNOLOGY. We can answer any questions you may have about this new technology and assist you in designing a prototype that will meet all of your requirements.
