Flip-chip applications curing

Sun et al. (2006) examined the use of novel silica nanofillers in underfill for flip-chip applications, and showed that pre-cure rheology and post-cure values of Tg are effected by nanosilica surface treatment. 

FP4531/ Loctite Fast-flow underfill 1 N/A Automated dispensing (21-gauge needle) Flip-chip applications requiring snap cure. 

Metal-Bumped Flip Chip Joints. ICAs can also be used to form electrical interconnections with chips that have metal bumps. ICA materials utilize much high filler loading than ACAs to provide electrical conduction isotropically (ie in all directions) throughout the material. In order for these materials to be used for flip chip applications, they must be selectively applied to only those areas that are to be electrically interconnected. Also, the materials are not to spread during placement or curing to avoid creating electrical shorts between circuit features. Screen or stencil printing is most commonly used to precisely deposit the ICA pastes. However, to satisfy the scale and accuracy required for flip chip... 

Organometallic conq)ounds have been explored as tiie latent catalysts for various epoxy resin systems [7,8,9]. Metal acetylacetonates (AcAc s), in particular, are foimd to be effective latent accelerators for epoxy and anhydride cure reactions [10,11,12]. Based on the epoxy/ anhydride/ metal AcAc system, underfill materials have been developed for flip-chip applications [5,6,13]. Metal AcAc s are unique as catalysts for epoxy cure reactions in that they not only provide high cure latency, but also offer a wide range of cure temperatures. 

S. Luo, T. Yamashita, C. P. Wong (2000) Study on the property of underfill based on epoxy cured with acid anhydride for flip chip application, J. Electronics Manufacturing 10, 191. 

Curing In-line compatible, low stress on flip-chip and large die Rapid IR, UV, or convection oven cure, <3-4 minute (in-line application preferred) Low volatile organic compounds (VOC) emissions during cure... 

Amicon E1330LV/ Emerson Cuming Unfilled, no-flow fluxing underfill (reworkable) Not applicable Nickel-gold and OSP finishes Syringe, jet dispense, or stencil print Flip-chip, CSP, EGA modest post-reflow cure (offline) required. Reworkable, 300 second reflow cycles 225°C peak. Variable fi-equency microwave curable. 

In soldering and when an ICA is used, the electrical connection is first established by the solder or the conductive adhesive before the bond is mechanically stabilized by application of an underfill. Using ACA or NCA makes it possible to combine electrical connection and mechanical stabilization in one process step. Electrically conductive connections made with nonconductive adhesives are based on mutual contact between the joining partners. A constant contacting force therefore has to be applied until the adhesive has cured. Contacting flip chips with adhesive... 

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