Effect of non-conducting filler additions on anisotropic conductiveadhesives (ACAs) properties and the reliability of ACAs flip chip onorganic substrates

摘要

Flip chip assembly on organic substrates using ACAs have receivedmuch attention due to many advantages, such as easier processing, goodelectrical performance, lower cost, and low temperature processingcompatible with organic substrates. ACAs are generally composed of epoxypolymer resin and small amounts of conductive fillers (less than 10wt.%). As a result, ACAs have almost the same CTE values as an epoxymaterial itself, which are higher than conventional underfill materialswhich contain lots of fillers. Therefore, it is necessary to lower theCTE value of ACAs to obtain more reliable flip chip assembly on organicsubstrates using ACAs. To modify the ACA composite materials with someamount of conductive fillers, non-conductive fillers were incorporatedinto ACAs. In this paper, we investigated the effect of fillers on thethermo-mechanical properties of modified ACA composite materials and thereliability of flip chip assembly on organic substrates using modifiedACA composite materials. For the characterization of modified ACAscomposites with different content of non-conducting fillers, dynamicscanning calorimeter (DSC), and thermo-gravimetric analyzer (TGA),dynamic mechanical analyzer (DMA), and thermomechanical analyzer (TMA)were utilized. As the nonconducting filler content increased, CTE valuesdecreased and storage modulus at room temperature increased. Inaddition, the increase in the content of filler brought about theincrease of TgDSC and TgTMA. However, the TGAbehaviors stayed almost the same. Contact resistance changes weremeasured during reliability tests such as thermal cycling, high humidityand temperature, and high temperature at dry condition. It was observedthat reliability results were significantly affected by CTEs of ACAmaterials, especially in the thermal cycling test. Results showed thatflip chip assembly using modified ACA composites with lower CTEs andhigher modulus from loading non-conducting fillers exhibited bettercontact resistance behavior than conventional ACAs withoutnon-conducting fillers