Underfill compound

Liquid encapsulation and potting compounds, e.g., for automotive parts Thermal and RT-curing adhesives, underfiller materials Composites, fiber-reinforced, e.g., for transportation or in printed wiring boards PCB build-up materials... 

No-fiow, fiuxing type underfill Epoxy resin, substituted phthalic anhydride (81-3) and methyUiexahydrophthalic anhydride (2078E), phenolic compound, and liquid rubber component STAYCHIP 2078E and STAYCHIP 81-3 (Cookson Electronics)... 

Effect of Lead-Free Conversion. Lead-free conversion exacerbates these potential silicon-level failures. Since the assembly is subjected to a higher temperature range than with tin-lead assemblies, there is a higher propensity for early failures due to residual stresses during cool down. In addition, there are potential concerns over the effect on low dielectric constant (k) materials in the silicon during second level temperature cycling. This is discussed in more detail in Sec. 58.3.13.9.The effect of mold compound and underfill material selection on first-level interconnects is also discussed in more detail in Secs. 58.3.13.5 and 58.3.13.6 respectively. 

Encapsulants are usually characterized as either potting compounds, glob-tops, or underfills, depending on the end use. Potting compounds are materials that are used to protect final assemblies (relays, component terminals, electrical contact assemblies, etc.). Glob-tops and underfills are specifically used for silicon die protection. 

Fillers in plastics, encapsulants, underfills, mold compounds, and solder masks Flux... 

An interface is a surface that forms a common boundary between two bodies or phases. A number of different types of interfaces are discussed in this section. Some interfaces form as the result of a solder reaction with chip or chip carrier terminal metallizations. These interfaces separate layers of intermetallic compounds and form boundaries between solder and the unreacted terminal metal. Other interfaces exist between metal and insulation layers. A number of critical interfaces form between an underfill and chip, substrate and solder. The solder contains a number of interfaces including grain boundaries, phase boundaries, and boundaries between intermetallic particles and the solder. Fig. 25 illustrates interfaces that exist in a terminal made with Pb n solder, Ti-Cu-Au under bump metallurgy (UBM) mounted on a chip carrier with Ni Au metallization and reflowed in a hydrogen environment. These interfaces must perform a number of critical roles in the formation of solder joints. The interface supports large structure and composition differences between phases and also contains and controls electrochemical barriers [100]. 

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