Ask Helena & Leo

Question: Section 6.3.2 on strand damage is confusing in the new Rev E document. Note 3 under the table seems to define damage as anything greater than 10% of the cross sectional area of a strand. This is difficult to explain or visualize on the production floor. The IPC-A-610 Rev D document did not include Note 3 and seemed to define strand damage as a strand with exposed basis metal. The Rev D document seemed to be easy to understand. Am I interpretting this correctly, and is there a good way to explain strand damge per the Rev E document?

Answer: Here is an explanation regarding strand damage.

Table 6-2, Allowable Strand Damage, Note 3: Damaged strands have nicks or scrapes exceeding 10% of cross sectional area, was added to describe the depth of the damage related to nicks or scrapes. Cross section is a 2-dimensional view of a slice through an object. Cross section is an area versus diameter which is a linear measurement. It is more difficult to interpret than the overall diameter of the conductors. Resistance varies with the cross sectional area of the wire. What does this mean to the inspector who is looking at strand damage? The inspector should not be required to perform an algebraic equation to figure out the cross sectional area of a certain gauge wire. It is much easier making a decision based on conductor diameter. If the inspector is not sure of the amount of Process Indicator damage, they should involve Quality and Engineering to quantify the damage.

The IPC/WHMA-A-620B Requirements and Acceptance for Cable and Wire Harness Assemblies describes the condition a bit more straight forward, nicks or scrapes less than 10% of the conductor diameter are not considered to be strand damage.