Abstract: A new method has been developed to provide underfill to chips mounted on substrates. First, an underfill is dispensed on the substrate. Second, the bumps of the chip are dipped in a flux that does not contain filler. Third, the chip that has been dipped in a tacky thermosettable flux is placed on the substrate, and fourth, the chip is soldered to the substrate, and simultaneously the underfill is cured. This process eliminates the interference on solder joints caused by the presence of filler in filled no-flow underfill. In addition, the fluxing property of the flux allows the use of underfills with emphasis on curing and mechanical properties instead of fluxing performance. Accordingly, a mounted device with reliable solder joints and underfill encapsulation is obtained.

Abstract: A new method has been developed to provide underfill to chips mounted on substrates. First, an underfill is dispensed on the substrate. Second, the bumps of the chip are dipped in a flux that does not contain filler. Third, the chip that has been dipped in a tacky thermosettable flux is placed on the substrate, and fourth, the chip is soldered to the substrate, and simultaneously the underfill is cured. This process eliminates the interference on solder joints caused by the presence of filler in filled no-flow underfill. In addition, the fluxing property of the flux allows the use of underfills with emphasis on curing and mechanical properties instead of fluxing performance. Accordingly, a mounted device with reliable solder joints and underfill encapsulation is obtained.