Abstract
Some mercapto-aromatic compounds as adhesion promoters were added into a siloxane-containing ultra-low-modulus photosensitive polyimide(PSPI) as a novel cover layer material to solve some serious problems in the plating process such as interpenetration of an acidic plating solution into the interface between the S--side of electro-deposited copper foll and the PSPI cover layer. A physical roughness modification of the S-side was effective to inhibit the interpenetration of the plating solution. However, a developing time of PSPI increased due to the excellent adhesion strength between the rough copper surface and the PSPI layer. As the result, the surface of PSPI was deteriorated by hydrolysis of imide carbonyl. The present work describes our chemical approach to increase the adhesion strength by using some additives expected as adhesion promoters without increase of developing time. The use of the mercapto-aromatic compounds with minor contents enhanced the peel strength(34.3N/cm) and resistance to plating solutions. As a result of TEM-EDX analysis, very thinner sulfurcontaining organic layer which was assigned to the mercapto-aromatic compound was observed between the copper surface and PSPI layer. These results are probably attributed to the grate roles of the added the mercapto-aromatic compound for enhancing adhesion properties and resistance to plating solutions. Other properties(thermal properties and photosensitivity etc. )of the modified PSPI formulation will be also discussed in this work.
