Flexible Printed Circuit Manufacturers
The leading conducting material in flex PCBs is copper foil, and occasionally, it may be alloyed with other metals such as aluminum, nickel, silver, or gold. The foil is often laminated to a non-conductive dielectric material like polyimide or polyester (PET). A layer of photosensitive ink, divided into bright oil and matte oil, coats the copper and the base material. This coating is then exposed using photolithography to form the circuitry pattern. A variety of methods are used for this exposure including screen printing and photo imaging. The patterns can be either additive or subtractive, which determines the current-carrying capability and environmental resistance of the finished product.
When designing a flexible printed circuit manufacturers, the designer must take into account whether it is being used in a static, one-time-bend-for-installation application or in a dynamic, continually bending, environment. In dynamic applications, excessive mechanical stresses can cause mechanical failure, which can be mitigated by careful design. This includes ensuring the correct flex PCB stack-up, minimum bend radius, and use of stiffeners where required.
Stiffeners are rigid, locally-added materials that increase the thickness and strength of a flex circuit in areas where extra support is required. These materials, typically a mix of FR4, Kapton, and aluminium or stainless steel, are attached to the flex PCB using pressure-sensitive adhesives or acrylic thermally-cured adhesives. They can be added to a single-layer, double-layer, or multi-layer flex PCB and can help with stress reduction, weight balance, or heat dissipation.
What Materials Do Flexible Printed Circuit Manufacturers Use?
While most flex circuits are made from copper, some are based on a plastic known as PEEK (polyether ether ketone). This material has excellent chemical resistance, handles radiation well, and is very durable. It is especially useful in medical applications, as it will not melt or deform even when subjected to X-rays.
As with all components, a flex PCB must have an effective structure to carry electrical signals. Conductors can be plated through holes or through-hole solder joints (TBS). Through-hole connections are usually made with teardrop-shaped vias, which reduce the likelihood of stress concentration spots. For through-hole connections with a large diameter, annular rings can be used.
During manufacturing, the flex circuit is covered with a protective film of polyimide, polyester, or PTFE (polytetrafluoroethylene). This layer protects the substrate and conductors from damage during assembly and operation. It also provides an effective barrier between the conductors and copper surfaces for soldering.
The cover film is then laminated to the copper and base material using the same method as for the surface finishes, with the exception that a different solvent is used. Once the protective layer is in place, it can be coated with a conductive ink or an organic coating. Once the conductive ink or organic coating is in place, it can be processed for bonding with other components, such as metallization (adding a thin layer of copper to the entire surface). This process is known as soldering. Once the soldering process is complete, the final product can be installed in a device.
