Secondary ion mass spectrometry (SIMS) supported the development of a polyimide and chromium-clad copper thin film packaging technology. The unique usage of SIMS was to analyze buried defects using extremely deep (10-40 mu m) elemental profiles. An example of a delamination is given in which SIMS is able to verify the presence of and to quantify an aminosilane adhesion promotor in the monolayer-coverage range under 13 mu m of polyimide. Several defects are described in which wiring layer species (Cr or Cu) are found in the polyimide together with traces of chlorine. These examples motivated a more detailed investigation of chlorine at CuCr to polyimide interfaces. Quantification aspects of SIMS are developed using a Cl ion implant through a CuCr to polyimide interface. Yield saturation, in which the ion yield of Cl- approaches unity for SIMS using a Cs+ primary beam, is evaluated as a simplifying quantification concept. The CuCr interface is demonstrated to actively getter chlorine during curing of intentionally chlorine-contaminated polyimide.