Gideon Analytical Labs received three failed Kapton based flex circuits with opens in the trace lines. The origin of the open was not known. The opens in the trace lines were traced down on the Kapton to several eyelets where contact was supposed to be made.
No areas were distinguished and no anomalies were found suggesting a trace copper foil problem on any of the circuits received. A cross-section of the above trace line and eyelet demonstrates the trace line (the line in the middle) either has been dislodged from the barrel or was never connected.
Separation of the copper foil from the via barrel caused the opens. The opens are most likely related to the cleaning (or lack of) of the copper foil prior to copper plating and forming the barrel.
Gideon Analytical Labs can solve the problem quickly to ensure that your production does not suffer from bad lats coming in from suppliers. This saves time, money and much frustration in tracking down causes and how to correct action.