Masaaki Takekoshi

Newly developed ultra low CTE materials for thin core PKG

To achieve the recent improvements in miniaturization and performance of mobile devices (Smart phone, Tablet PC etc.), the semiconductor PKG substrate installed in these devices is demanded to be thinner and higher in density. However, the thinner PKG substrate may cause poor connection reliability due to increased warpage by soldering. The ultra low CTE (Coefficient of thermal expansion) core material has been required as the key solution for the reduction of the warpage of the thinner PKG substrate such as PoP (Package on package). We have just developed two types of ultra low CTE core materials named E-705G and E-800G to meet with the requirement, applying our original resin systems and the filler surface treatment technologies. The developed materials show the ultra low CTE(X, Y) property (2.8-3.3 ppm/°C) similar to that of glass fabric itself. Also E-705G has high flexural modulus over 33-36 GPa at room temperature. Regarding E-800G, it has the good dielectric characteristics (lower dielectric constant and dissipation factor), can be applicable higher speed PKG. Both of the materials have high reliability and high heat resistance which is suitable for the lead-free soldering process. Confirming the warpage property, we evaluated the warpage behavior of PoP (bottom) constructions before/after assembly process. The newly developed materials showed the much lower warpage than the conventional low CTE material.

Ultra low CTE (1.8 ppm/°C) core material for next generation thin CSP

Along with the advancement in miniaturizing of mobile devices, typified by smart phones and tablet PCs, the semiconductor PKG substrate installed in these devices is demanded to be thinner and higher in density. As one of the most innovative solutions, the PoP (package on package) technology, which has the three-dimensional construction, has been expanding rapidly in recent years. However, the thinner PKG such as PoP tends to warp at the assembly process and cause the decrease in the connection reliability. Therefore ultra low CTE (coefficient of thermal expansion) core materials have been needed as a key solution for the reduction of the warpage for PoP. Recently, we have developed new ultra low CTE core material named E-770G for next generation thin CSP, applying new resin systems, featuring low shrinkage and low residual stress. In particular, E-770G has achieved ultra low CTE of 1.8 ppm/°C which leads to significant reduction of the warpage. Furthermore, it has low dissipation factor at high frequencies (Df: 0.005 at 1 GHz). So its also applicable to high speed PKG applications. Confirming the warpage property, we evaluated the warpage behavior of the bottom PKG before/after assembly process. E-770G showed the much lower warpage than the conventional ultra low CTE core material.

New ultra low CTE material to reduce the warpage of thinner PKG

Along with the advancement in miniaturizing of mobile devices, typified by smart phones and tablet PCs, the semiconductor PKG substrate installed in these devices is demanded to be thinner and higher in density. As one of the most innovative solutions, the PoP (package on package) technology, which has the three-dimensional construction, has been expanding rapidly in recent years. However, the thinner PKG substrate tends to warp at the assembly process and cause the decrease in the connection reliability. Therefore ultra low CTE (coefficient of thermal expansion) materials have been needed as a key solution for the reduction of the warpage for thinner PKG substrates. Recently, we have developed new ultra low CTE material named E-770G for next-generation semiconductor PKG substrate, applying new resin systems, featuring low shrinkage and low residual stress. In particular, E-770G has achieved ultra low CTE (X) of 1.8 ppm/°C which leads to significant reduction of the warpage. Furthermore, it has low dissipation factor at high frequencies (Df: 0.005 at 1 GHz). So its also applicable to high speed PKG applications. Confirming the warpage property, we evaluated the warpage behavior of thinner PKG substrate before/after assembly process. E-770G showed the much lower warpage than the conventional ultra low CTE material.

Study of influence of mechanical property of temporary bonding adhesive on warpage of FO-WLP

Warpage suppression of FO-WLP during the fabrication process on the support was studied in the view point of material properties of temporally adhesive. It was found that Youngs modulus of the temporally bonding adhesive influenced the warpage significantly and using that of small Youngs modulus could suppress the warpage.

Development and Evaluation of Carrier Glass Substrate for Fan-Out WLP/PLP Process

The effect of glass type used as fan-out carrier substrate on the reliability of the electrical devices were investigated. Glasses with thermal expansion coefficient of around 6~8 ppm/K with and without alkali ions involved in the glass were tested. With using non-alkali type glass as the carrier material, it was confirmed that the lifetime of the test vehicles were longer than that heated with conventional soda-lime silicate glass by the evaluation under highly accelerated steam and temperature condition.

Warpage Suppression during FO-WLP Fabrication Process

Composing material combination of the re-distribution layer first type fan out wafer level package with various die occupancy ratio during the fabrication process on the support was studied by both of the making test vehicle and the numerical simulation. The investigated TV composed of glass support, temporary bonding adhesive, 1st re-distribution dielectric layer, Cu layer, 2nd re-distribution dielectric layer, Si die with die attached adhesive and molding compound. The fabrication was performed by the steps of applying all the materials serially and the final step of grinding down of the mold surface. The die occupation ratio in the TV become larger, the warpage of the TV decreased. The CTE of the support influenced the TV warpage significantly comparing with the CTEs of the EMC, the RDL dielectric layer and the TBA. From the investigated results the strategy of the appropriate selection of the materials to the die occupation factor was made to know. It suggested that the die occupation ratios were 21, 40 and 66%, using the support with the CTE of about 8, 10, 11 x10-6/°C and the EMC with the CTE of 8.4 x10-6/°C could make non warped TV, respectively. It was also suggested that the warpage could be controlled within 1mm during all the fabrication process steps by using the support with the CTE of 8.0 to 8.7 x10-6/°C in case of that the die occupation ratio was 40% and the CTE of EMC was 8.4 x10-6/°C.

Challenge to zero CTE and small cure shrinkage organic substrate core material for thin CSP package

To reduce warpage of thinner package application such as POP (package on package), the ultra-low CTE (coefficient of thermal expansion) core materials has been developed. The resin system was originally designed by the concept of the combination of the hard and the soft segments. The hard segments composed of a stack structure of aromatic rings and the strong intermolecular force between them, which are the origin of the ultra-low CTE. The soft segments can follow the thermal motion of the glass fabric well due to the low elastic modulus. The CTE of the newly developed core material was as low as 0.7 ppm/°C. Then, it showed the ability to reduce warpage of PoP before/after assembly process. Our fundamental study revealed that the amount of the warpage is affected by not only the CTE but also the shrinkage of resin component in the core.

New Super-Low CTE (0.7 ppm/K) Core Material for Next Generation Thin CSP

The thinner and higher density PKG (package) is being required strongly for the growth of smaller mobile devices. Especially, package on package technology (PoP) has become a mainstream for application processors which are installed in smartphones and tablets.However, the warpage of thinner PKG often causes a problem at the chip mounting process. The main factor of warpage is the mismatch of CTE (coefficient of thermal expansion) between substrate and chip. Therefore, the lower CTE core materials are needed for the thinner PKG.Recently, Hitachi Chemical has developed the super-low CTE material, core and prepreg, applying our new resin system and filler treatment technology, and placed it on the market. Furthermore, a super-low CTE material of 0.7 ppm/K is currently under development. The super-low CTE material shows the best warpage performance in our low CTE core material lineups, maintaining its higher Tg, high modulus and low Dk/Df values.Copyright

Newly developed ultralow CTE materials for thinner PKG applications

The higher density packaging technologies have been required to reduce the area of substrate for smaller portable handheld products and devices such as smart phones and tablet PCs. So, the three-dimensional packaging is becoming to be a key technology to minimize the total size of products and devices. However, the thinner construction of PoP (package on package) may cause the poor connection reliability because of the warpage of the substrate at the soldering process. So, the reduction of the warpage of the substrate by the ultralow CTE (coefficient of thermal expansion) materials may be the key to overcome. Recently, we have developed two types of ultralow CTE materials to meet with the requirement applying our new resin systems and a filler treatment technology. The developed materials show the ultralow CTE(X) of 2.8-3.3 ppm/OC which is close to that of the glass fabric. The resulted warpage using the material is much lower than that of the conventional low CTE material. We are also developing a technology for the further lowering of CTE for future applications.