Min-Jin Ko

Effect of postmold curing on plastic IC package reliability

Nearly all IC encapsulating compounds require a postcure treatment to ensure integrated circuit (IC) package reliability. The issue of postcuring and this effect on IC package reliability performance are considered in this article. We examined the development of various encapsulating compounds properties with various durations of postcure time. It was found that the mechanical strength, glass transition, and adhesion strength were increased with increasing duration of postcure time compared to as-molded samples. However, these properties could reach ultimate values after postcuring for 1–2 h. It was also seen that the moisture uptake was increased for samples that have been post-mold-cured due to increased crosslinking density causing a large free volume in the glassy polymer matrix. C-mode scanning acoustic microscopy (C-SAM) analyses were performed to investigate the effect of the duration of postcure time on the IC package reliability and they show a good relationship with the evolution of the compounds properties during the postcure process.

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 moisture. This also significantly increases the mechanical strength of the cured compound at reflow temperature. However, the detailed 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.

Investigation on the effect of molding compounds on package delamination

Although adhesion strength between molding compound and other substrates (leadframe, die pad, die, and passivation coat etc.) is an important parameter to evaluate the susceptibility of an IC package to delamination, there have been few systematic studies on this subject. This paper presents such a study, particularly the effect of the components (base resin, accelerator, and other additives) in the molding compound on adhesion strength and delamination at the interlayers in an IC package during IR reflow soldering. C-Mode Scanning Acoustic Microscopy (C-SAM), Al peel test and TBA (Torsion Braid Analysis) were used to characterize the adhesion sensitivity of the molding compound. Not surprisingly, epoxy with low molecular weight and hardener with flexible structure have a better adhesion strength than standard epoxy/hardener resin. We have also investigated the relationship between adhesion characteristics and viscoelastic properties of the molding compound. It was seen that elastic shear modulus (G) has a good correlation with the Al adhesion strength. It was also found that the other components such as catalyst, coupling agent, and flexibilizer have a great effect on the adhesion strength of the molding compound to leadframe/die pad and passivation PI coat. The extent of their effects depends on the amount and kind of components used.

The effect of mold compounds on warpage in LOC package

This paper describes a warpage study on LOC-TSOP memory devices. The main objectives of this study are to evaluate the impact of the mold compound on the package warpage with different sized dies. It was found that the balance of the bending between at the edge side region and at the die attach region controls the package warpage. The package tends to bend convex upward at the edge side region and concave downward at the die attach region. The various mold compounds were prepared to study the effect of the components, particularly resin and filler. It has shown that the optimum mold compound can be changed according to the inner structure of the LOC-TSOP. The effect of post mold cure on package warpage was also examined based on the cure rate.

New Carbon-bridged Hybrid Polymers for Low-k Materials

Reducing interline capacitance and line resistance is required to minimize RC delays, reduce power consumption and crosstalk below 100nm node technology. For this purpose, various inorganic- and organic polymers have been tested to reduce dielectric constants in parallel with the use of copper as metal line. Lowering the dielectric constants, in particular, causes the detrimental effect on mechanical properties, and then leads to film damage and/or delamination during chemical-mechanical planarization CMP) or repeated thermal cure cycles. To overcome this issue, new carbon-bridged hybrid materials synthesized by organometallic silane precursors and sol-gel reaction are proposed. In this work, we have developed new organic-inorganic hybrid low-k dielectrics with linear or cyclic carbon bridged structures. The differently bridged carbon structures were formed by a controlled reaction. 1 H NMR, 29 Si NMR analysis and GC/MSD analysis were conducted for the structural characterization of new hybrid low-k dielectric. The mechanical and dielectric properties of these hybrid materials were characterized by using nanoindentation with continuous stiffness measurement and Al dot MIS techniques. The results indicated that these organic-inorganic hybrid materials were very promising polymers for low-k dielectrics that had low dielectric constants with high thermal and mechanical properties. It has been also demonstrated that electrical and mechanical properties of the hybrid films could be tailored by copolymerization with PMSSQ and through the introduction of porogen.