The effect of filler on the properties of molding compounds and their moldability

High loading of filler is known as an effective method for lowering the moisture absorption of the encapsulating compound since the filler itself does not absorb a moisture. This also significantly increases the mechanical strength of the cured compound at reflow temperature. However, the detail effect of the filler on the characteristic of the encapsulating compound was not fully disclosed. In this paper, the encapsulating compounds filled with an amorphous silica were prepared to study their characteristics relating to the reliability of an IC package and its workability. We have investigated the effect of the filler size and shape on the flowability of the compound. Both ultra fine and more spherical shaped filler are very effective to increase the spiral flow. We have also examined the properties of the encapsulating compound containing the filler chemically modified with the different silanes. The study reveals that the modification of the filler with reactive silane chemicals has a great influence on the properties of the compound including the mechanical strength, flowability, the flash/bleed and the shelf life. So, the proper modification of the filler is critical for balancing the reliability and moldability of an IC package.