flex circuit facilitate assembly automation
A flex circuit is a flexible printed circuit board with the capability to bend and revert back to its original shape without compromising electronic functionality. These flexible circuits are designed for high-density applications and offer numerous advantages over rigid PCBs including better airflow, higher heat dissipation, and a smaller footprint. They also facilitate assembly automation by eliminating the need for external wires and connectors.
Flex circuits are available in a variety of thicknesses and densities and can be used in a wide range of applications. The basic structure consists of an insulating layer and a pattern of conductive copper traces on one side of the substrate, which can be either polyimide or a polymer composite. The insulating layer is then covered with a layer of solder mask. In order to guarantee the correct operation of a flex circuit, it is essential to follow industry-standard best practices when designing it. These include using simulation software to verify the design and testing it for proper operation prior to sending it off to be fabricated.
During the fabrication process, manufacturers carefully consider the required bend radius of a flex circuit. This radius should be defined early in the design phase to ensure that the flex circuit can be bent without damaging the copper traces. Additionally, the flex circuit should be free of features like cutouts, slots, and mounting components that could compromise its ability to withstand the specified bend radius.
How does a flex circuit facilitate assembly automation?
Once the flex circuit is fabricated, it must be prepared for assembly by adding a layer of pressure sensitive adhesive (PSA). The PSA can be applied with either a laser cutter, which is ideal for low-volume productions, or a punch & die set, which is better for larger volumes. It is important to select the right type of PSA for your application, as there are many options available on the market, each with its own pros and cons.
When selecting the PSA, it is important to consider whether you need the flex circuit to be mechanically attached to an enclosure or other component, or if you need it to perform a specific function. There are a number of PSA types on the market, some of which are reflow rated for automated component assembly. It is recommended to choose a PSA that is reflow rated when possible, as this will help to avoid any issues during the assembly process.
Depending on the type of application, it may be necessary to add stiffeners to a flex circuit. Stiffeners are added to a flex circuit as one of the final stages of fabrication, and can be applied with either a layer of pressure sensitive or thermal set adhesive. PSAs are typically preferred over thermal set adhesive for flex circuit applications, as they can be installed with a peel-and-stick method.
When designing a flex circuit, it is important to account for the maximum possible number of layers and conductors. The number of layers should be limited to what is required for the circuit’s function, and the conductors should be placed within the allowed limits to prevent any problems during assembly. Similarly, the length of the signal lines should be kept as short as possible to prevent interference between them.
