Improvement of interfacial adhesion in plastic packages: Dimples, metallic coatings and black oxide

Delaminations at various interfaces are one of the most critical reliability issues in plastic packages. Delamination is formed as a result of the imperfect interface adhesion between the integrated circuit (IC) package components. In the present investigation of interfacial adhesion improvement between lead frame and epoxy molding compound (EMC), special emphasis has been placed on: (i) the effects of dimple and metallic coating and; (ii) the effects of temperature and hygrothermal ageing excursions simulating the practical package assembly processes. Moreover, the extension of copper oxide coating technology from printed circuit board (PCB) to IC packages, especially for copper lead frame and the heat sink/substrate for tape ball grid array (TBGA) packages, have necessitated a more detailed study of characterization and optimization of black oxide coating material, effect of debled treatment and hygrothermal effect on interfacial adhesion.; A study is made of the effects of dimple and metallic coatings by evaluating the surface characteristics, such as wettability, surface roughness and elemental compositions, which in turn are correlated with the maximum pull force measured from the lead pull tests. It is found that the dimples enhanced the maximum pull force through improved mechanical interlocking of molding compound, depending on the type of coating. The wettability of metal surface represented by the surface energy played a predominant role in controlling the interfacial adhesion.; The major contributions of this thesis are: (i) to incorporate dimple and metallic coatings under hygrothermal conditions and to study its interfacial adhesion strength; (ii) to report that the improvement in the interfacial adhesion due to dimples was higher for the coatings with inherently weak interfacial adhesion than those with inherently strong adhesion characteristic; (iii) to study the correlation between interfacial adhesion and differential work of adhesion at dry and wet condition of metallic coatings; (iv) to report the correlation between the work of adhesion difference and polar surface energy of metallic coatings; (v) to report that dimples retains the interfacial adhesion under humid environment; and; (vi) to compare the surface characteristics and interfacial adhesion of as-received black oxide and debled black oxide under different oxidation treatment time and hygrothermal conditions. (Abstract shortened by UMI.)...