Clean Flexible Printed Circuits

The flexible printed circuit (FPC) is an electronic interconnection technology that allows a number of precision components to be stacked in a very small space. These are typically embedded in a flexible plastic sheet with an insulating film and conductor layer. This provides an extremely compact and reliable solution that breaks through the traditional wire-to-board interconnection technology and offers many advantages to end users.

FPCs can be used for a variety of applications and are available in four different types: single-sided, double-sided, multi-layer, and rigid-flex. Single-sided flex PCBs contain one layer of copper that sits on the dielectric film, and electric components are housed on only this side. These are the most common type of flex circuits, and they are suitable for a wide range of applications.

Depending on the application, a single-sided flexible printed circuit may be finished with a soft gold covering or tin finishing. These finishes provide a protective solder mask and help prevent the circuits from external damage such as dust, moisture, and corrosion.

How to Clean Flexible Printed Circuits

Most flex PCBs are made from copper foil, which has the best balance of cost, physical properties, and electrical performance attributes. It is typically bonded to an adhesive or, more recently, to a thermally-conductive polyimide material known as FR-4. A rigid-flex circuit can also have a dielectric stiffener material added, allowing the flex sections to be more easily handled and soldered into place.

Flex PCBs must be carefully designed and fabricated to avoid stress within the materials that can cause fatigue fractures. This can occur at the corners of flex circuits where they are subject to the most bending, as well as in areas where tight bend radii are applied to the corners. To mitigate this, a designer should use room dimensions in the layout software to allow vias to be placed only where there are no bends. In addition, if a flex circuit must have tight bend radii, a design rule should be created to limit the amount of copper that is placed at these locations.

A good cleaning routine is critical to keeping your flex PCBs functioning properly. A regular cleaning regimen can prevent dirt build-up that can interfere with signal transmission and reduce overall reliability. The following cleaning methods are the most effective:

At the heart of flexible printed circuits lies a substrate material, typically made from polyimide or polyester film. This substrate serves as the foundation onto which conductive traces, typically made of copper, are etched. Unlike rigid PCBs, where the substrate is inflexible, FPC substrates are highly flexible, allowing the circuit to bend, twist, and conform to the contours of the device they inhabit. This flexibility is further enhanced by the thinness of the substrate, which can be as slim as a few micrometers, enabling FPCs to be incredibly lightweight.

The conductive traces on flexible printed circuits are patterned using advanced etching techniques, ensuring precision and reliability in signal transmission. Additionally, FPCs can incorporate various components such as resistors, capacitors, and integrated circuits, further augmenting their functionality. These components are typically mounted using surface-mount technology (SMT) or flip-chip bonding, allowing for compact designs and efficient use of space.