The Role of Coverlay in PCB Assembly
Role of Coverlay in PCB Assembly
Coverlay is a polyimide film that protects the copper features of the PCB during manufacturing. It can be used on rigid or flexible circuit boards. It offers resistance to various elements, including solvents, acids, and bases, making it an ideal choice for applications that require durability. It can also withstand bending or twisting without breaking. In addition, it can withstand high temperatures. This makes it an excellent option for flex PCBs.
Coverlays are typically produced using a laser and can be cut and punched to match the design of the pcb assembler. A layer of adhesive is then applied to the surface. This is either a thermosetting or pressure-sensitive adhesive. Once the adhesive has been applied, the coverlay is laminated to the board with heat and pressure. This process ensures a strong bond between the layers.
During the construction of flexible circuit boards, coverlay is often used to protect the copper pads and vias from contaminants. In addition, it can be used to prevent the flow of molten solder onto a pad and damaging the component. It can also be used to provide protection during the assembly and reflow processes.
The Role of Coverlay in PCB Assembly
The most popular coverlay material is Dupont’s Kapton, which is available in a variety of thicknesses and bonds well to acrylic adhesives. Other options include Ube’s Upilex, which is a hybrid of Kapton and Teflon fibers to improve its mechanical properties and flexibility. Dupont’s Pyralux and GE’s Ultem are other options that offer good conformability, flex life, and temperature stability.
Before a pcb assembler begins construction, they must select the best coverlay material for their application. A number of factors need to be considered when selecting a coverlay material, including the operating environment and the assembly process. For example, if the PCB will be exposed to harsh environments, a more durable material such as polyimide may be the best option. Also, if the PCB will be subjected to repeated bending and twisting, the coverlay material must be able to withstand these movements.
Other considerations include the size and shape of the pads, vias, and other exposed components. Ideally, the pad openings should be the same size and shape as the corresponding copper feature in the circuit board design. This helps to minimize assembly time and avoid errors.
In addition, the pcb assembler must consider how the pads and other exposed surfaces will be processed by the factory. For example, if the design calls for a square or rectangular opening, it is important to work with the fabricator to ensure that they can produce this.
Another factor to consider is the amount of etching or drilling required to expose the copper features on the circuit board. This will affect the resulting cost and lead time of the PCB. If the design requires a large number of holes, it is often possible to reduce costs and lead times by removing unnecessary copper features in the circuit board. Alternatively, the pcb assembler can use a laser to skive the coverlay pad exposures and fingers post-coverlay lamination.