Non-destructive Characterisation of Flexible Type Material using a White Light Interferometer

One of the key factors which can cause to a halt of a surface-mount-technology (SMT) assembly process is due to the broken cover tape. Under such circumstances, the quality of the cover tape will need to be re-evaluated and confirmed by failure analysis, in particularly, the thickness of the cover tape. For the characterisation of flexible type material like cover tape, caliper, physical cross-section and optical techniques are some of the commonly used conventional techniques. However, destructive sample preparations are usually needed for these techniques, and the characterisation of the sample is confined to a very small region per sample preparation, therefore make them non-ideal. Profilometer is a more advanced technique that has been used widely in various applications but it has found to be not compatible for studying cover tape. In this work, we study the feasibility of using an interferometer in characterising the flexible type material through the investigation of various types of cover tapes from semiconductor industry. Results have demonstrated and verified that interferometer is a very promising technique in characterising flexible type material. This technique has enabled the characterisation of the material in 3-dimensional to an accuracy of <0.5 um non-destructively in a short amount of time as compared to the conventional techniques.