UV laser for flexible circuit cutting

Flexible Printed Circuits (FPC) enable a variety of designs that cannot be achieved with traditional rigid circuit boards. For example, fabricating circuits on flexible materials enables new and challenging applications, including a variety of multilayer functions and solutions for the space, telecommunications, and medical industries.

The current trend in the FPC industry is all about miniaturization, as designers look for ways to reduce circuit size while eliminating factors that limit mounting density or the distance between circuits on a circuit board. Meeting these requirements often requires arbitrary shaping, but the basic square circuit is too elastic to meet the requirements of many modern applications.

These design requirements are challenges, including issues of partitioning or the process of removing circuits from the board. How can smaller arbitrary circuits with high mounting density be precisely cut without damaging the components or the circuit itself? Flexible circuit materials are unique in that even the smallest stress on the circuit during cutting can cause damage.

Using UV Laser System to Cut Flexible Printed Board Circuits

To avoid this damage, it limits the variety of designs. The buffer space around each cutout must be considered in the design, which means the cutout width will be wider than needed, the components cannot be placed close to the edge of the board or close to each other, and the forming cannot be as complex as needed. Without viable solutions to these types of problems, these constraints can drown out innovation, as unsatisfactory splitting becomes a major design consideration.

Automatic circuit board cutting (Routing) and traditional mechanical depaneling methods (such as die punching) can result in large cutting widths and excessive stress for complex flexible circuits. Even the CO2 laser cutting method is unsatisfactory in this respect, as it creates a larger heat-affected area.

However, when it comes to FPC sub-board cutting, a technology that can meet the challenge has emerged: UV laser cutting. This technique eliminates the physical stress of the mechanical process and greatly reduces the thermal stress of the CO2 UV laser, meeting the design trends described above. Exploration of various factors will reveal why UV laser cutting has emerged as an option when it comes to flexible circuit cutting.

Circuit stress and cutting width

All flex cutting methods create some amount of stress on the circuit board, but there are differences in the type of stress introduced and the degree to which the stress affects the circuit. When considering the above-mentioned splitting method, there may be two types of stress on the flexible printed circuit board: mechanical stress or thermal stress.

Mechanical stress occurs when using mechanical splitting methods such as die punching or Routing. The effects of mechanical stress on flexible circuits include: burrs, deformation, and damage to circuit components. These effects are very serious for flexible materials. For example, die punching is a high-impact process that vibrates circuits and damages components, and requires considerable cutting buffer space. In die punching and routing, the typical FPC cut width is 1mm, but this width is too large for many complex, random flex circuits. Such wide cutouts can result in: reduced mounting density, or reduced circuit mounting per board. At a time when flexible printed circuits are becoming smaller and more compact, this raises the question of technology and cost.