Since their inception over 30 years ago, underfills have enabled numerous new packages and have provided the required support and reliability needed for highly miniaturized and lead-free devices. It is safe to say that without these essential materials, many of today's advances would not be possible. Continued developments in underfill technology such as enhancements in filler technology, better control of flow rates, new cure mechanisms, improved modulus properties and alternative application techniques have brought enhanced performance capabilities to the market. But, as the industry continues its march forward toward more efficient, flexible and miniaturized devices and component configurations, even more underfill system capabilities will be required. To date, the four most commonly used types of underfills are capillary flow materials, fluxing (often referred to as no-flow) underfills, comerbond and edgebond systems. Each of these have relevance for certain applications but some of the newer devices - and even some older generation packages - may benefit from a breakthrough underfill material technology in the reflow cured encapsulant class. The new material system - called epoxy flux - is enabling many applications in both semiconductor packaging and printed circuit board (PCB) assembly, as well as some of the emerging device configurations such as package-on-package (PoP).
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