Liquid Photoresist Techniques for Fine Pattern Flexible Printed Circuits Available to Purchase

This paper presents a new roll‐to‐roll (R‐R) production system modified for fine line patterning of flexible printed circuits (FPCs) using the subtractive method. The R‐R system is especially suited to production of FPCs because the material used—copper‐clad laminate (CCU—can be handled as it is rolled. Consideration has been given to methods and materials in designing the machines. They are now operating successfully and are used in single‐sided flexible circuit manufacture. A liquid photosensitive etch resist and a collimated light source are recommended for the system and several factors necessary for achieving R‐R working conditions are discussed. Judging from the experimental results of these systems, using narrower width materials with chemical surface preparation is an effective technique for improving the yield rate. The selection of a liquid photoresist is not so common in the case of rigid printed circuit boards because of the difficulty of the coating process. On the other hand, in the case of flexible PCBs, it is successful not only in terms of resolution characteristics but also of productivity under several different types of coating conditions. It should be noted that use of the conventional subtractive method in the printed circuit field is still advantageous as some semiconductor technologies are applicable.