typical tolerances in flexible PCB manufacture
As the PCB industry continues to develop, tolerances are becoming more critical than ever. These tolerances can impact the fabrication process, cost and even lead time of the project. However, if the tolerances are too tight they can cause the project to be unfeasible and even compromise the quality of the finished product.
PCBs must be made within specific tolerances to ensure that they are fabricated and assembled correctly. The tolerances that a PCB must meet depend on the material it is made from, how complex the board design is and the manufacturer’s capabilities. Tolerances of geometric parameters are the maximum allowable variations in a specific parameter’s value. This can include things like straightness, flatness, roundness, cylindricity and line profile. These tolerances are typically expressed as an absolute value, a decimal value or a percentage. For example, a PCB size tolerance may be stated as 0.008” or +/- 0.016”.
Isolation gaps are a critical aspect of the electrical performance of a flexible pcb manufacture and can help minimize signal reflections which can result in distortion and short circuits. The size of the isolation gap is determined by the thickness of the copper on a particular PCB. The minimum isolation gap tolerance can vary based on the manufacturing process, copper thickness variances and the dielectric properties of the PCB material.
What are the typical tolerances in flexible PCB manufacture?
For mechanical processes, a tolerance is required to allow routing tools to cut holes and route the desired path for traces and other features. This tolerance can be up to +-0.005”, and the actual needed hole size will usually fall within this range. Depending on the type of PCB, a routing tolerance will also be applied to plated slots and cutouts as well.
Plating is an essential component in the final assembly of a PCB and it requires its own set of tolerances. The chemistry must flow through the entire board and large plated holes and slots can plate slower than smaller holes. This is due to the chemistry having to move back and forth between the panels as well as air agitation moving around the chemistry and keeping it evenly mixed.
The best way to ensure that the tolerances you need for your PCB are met is to provide clear and detailed documentation with the manufacturer of your choice. This should include the nominal dimensions and tolerances for all of the critical features of your design. This will ensure that your specifications are understood and that any deviations from standard practices are clearly noted so that the PCB fabrication and assembly processes are not compromised. In addition, it is a good idea to use standard components as these will have commonly accepted tolerances that are easier to meet. Finally, always choose an established PCB manufacturer that has a track record of meeting your exacting requirements. In doing so, you can be confident that your printed circuit board will be of high-quality and reliable design.
