Flip-chip underfilling with non-conductive photoinitiated adhesives- a new approach

摘要

The trend for miniaturisation in electronic equipment iscontinuing unabated. The increasing complexity of electronic memorycomponents allows for new layout structures and design possibilitieswhich constantly reinforce this trend. As IC capacity rises, newpackaging technologies are also gaining steadily in importance, andflip-chip technology has established itself as a marketable and highlyefficient technique. When flip-chip technology is used, there is alwaysa need to fill the gap between die and substrate with a resin, alsoknown as an underfill. Due to different coefficients of thermalexpansion, stresses appear between bumps and die as well as betweenbumps and substrate. The underfill minimises or compensates thesestresses. Additionally, it ensures the die's mechanical stability on thesubstrate. This paper presents three different underfiller systems whichare cured by three different mechanisms. These completely new and partlyunique underfilling materials have been developed on the basis ofelastified, single component epoxy resins, and are suitable for a widerange of carrier substrates, offering obvious advantages compared withthe systems available on the market at present. Greater attention ispaid to those underfills which enable completely new underfillingtechniques involving photoinduced pre-activation by light of a certainwavelength and intensity, even without subsequent heat curing. Thistechnology opens up new ways of drastically cutting flip-chip processcost by economising on several process steps