What is the maximum allowable span of delamination or bubbles in the coverlayer of flexible circuitry?

The maximum allowable span of delamination or bubbles in the coverlayer of flexible circuitry is specified as 25%. This standard is critical for maintaining the integrity and performance of the flexible circuits. When delamination or bubbles are present, they can compromise the electrical and mechanical properties of the circuitry, leading to potential failures in function or reliability.

A 25% limit ensures that any defects remain within an acceptable range that does not adversely affect the overall reliability and usability of the circuit. Exceeding this percentage could potentially lead to significant failure modes, including loss of adhesion, electrical shorts, or signal integrity issues. Therefore, having a clearly defined limit allows manufacturers and quality control personnel to ensure that the flexible circuits meet the necessary operational standards and can withstand environmental stresses.

In contrast, the other options suggest much higher allowable spans that would not align with the performance and reliability expectations set forth in the IPC standards. Higher percentages could potentially lead to more significant reliability issues, which is why the 25% standard is pivotal in ensuring product quality.