flex PCB fabrication support fine pitch components
Compared to rigid PCBs, flex circuits can reduce the size and weight of a design by up to 75%. This is achieved by using a flexible polyester or polyimide material as the substrate and applying various layers to it. Conductive material traces are then etched on the substrate and a coverlay is applied. The coverlay protects the layers from moisture, dirt, and other contaminants during manufacturing and assembly.
The first thing to do before designing a flex pcb fabrication is to make sure the board fabricator has the capabilities of supporting your fine-pitch components. This is a crucial step because many flex fabrication processes can’t handle the finer pitch, and it could lead to poor solderability or even failure of the components.
Some of the factors that can affect the ability of a flex board to support fine-pitch components include the type of copper, the thickness of the traces, the diameter of the vias and the bending radius. For example, thicker traces require more copper to support their conductivity, and this can increase the overall cost of the circuit board.
Can flex PCB fabrication support fine pitch components?
Another factor is the design itself. Some design techniques that are common to rigid PCBs are harder to achieve reas on able yields for in flex fabrication, and this can also drive up the cost of a flex circuit board. This includes buried and blind vias, dual surface finishes like ENIG or electroplated nickel gold and hot air leveled solder, and more. The best way to avoid these costs is to consult your fab engineer and see what they can do for you.
The next thing to consider is the number of layers in a flex circuit board. While multi-layers offer more flexibility, they do add to the cost. This is because multiple lamination processes are involved in creating multi-layer flex circuit boards. Additionally, larger flex boards cost more because of raw materials and panel utilization factors. A general rule of thumb is that each doubling of the layer count in a flex circuit board will cost around 20-30% more than the previous layer count.
In addition to these factors, it’s important to keep in mind that a flex circuit board is more likely to bend than a rigid PCB. As such, it’s a good idea to use rounded edges wherever possible on the traces and pads of your flex circuit board. This will help to decrease the risk of cracking during bending and improve the mechanical strength of the circuit.
The etching process for a flex circuit board is identical to that of a rigid PCB, but instead of an epoxy resin, a polyimide film is used. The film is then coated with a photosensitive etch resist material and the mask pattern is aligned. A UV light is then used to expose the resist material and chemically etch off the copper. The traces and vias are then plated with a thin copper coating, similar to the process of rigid PCBs.