What is Bow
Bow is an irregular construction anomaly that can occur in a PCB. It is characterized by a curved or arched shape in the board, causing it to deviate from a flat surface. The bow is measured as the largest gap or distance between a flat surface and the bottom of the PCB when two opposite ends are constrained.
To determine the bow in a PCB, specialized tools such as a Coordinate Measurement Machine (CMM) or pin gauge are used. These tools accurately measure the maximum allowed gap or distance for the bow. The specific requirements and standards for the maximum allowed gaps are set by the PCB industry.
The bow measurement is typically conducted in both the length and width directions of a four-sided card. More complex boards may require additional measurement directions based on factors such as the types of mounted components, shape of the board, and critical mechanical packaging requirements. The design authority determines the specific measurement directions.
English 
German