Moisture underfill adhesives

Large amounts of absorbed moisture in the die-attach or underfill adhesive. 

The absorption of moisture in underfill adhesives induces a tensile hygrothermal stress on the solder-ball connections causing electrical opens in the connections and cracking in the adhesive. These tensile stresses offset the compressive stresses that underfill adhesives provide in improving the reliability of flip-chip and ball-grid-array devices. 

Lastly, adhesives are used to dissipate stresses that may be generated from thermal excursions, mechanical shock, vibration, or moisture. Specially formulated adhesives are effectively used as underfills for flip-chip devices and ball-grid-array packages to compensate for mismatches of expansion coefficients among the solder, the silicon chip, and the ceramic or plastic-laminate substrate. Low-stress adhesives are also used to attach fragile devices such glass diodes and to dampen stresses due to vibration. 

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