Shinji Baba

Realization of Pb-Free FC-BGA Technology on Low-k Device

In the field of advanced electric devices using fine wafer process below the technology node of 130nm or 90nm, low dielectric constant inter-metal-dielectric (Low-k IMD) have been applied to have high speed operation. And from the environmental viewpoint on electric devices, elimination of the harmful materials like lead (Pb) material is one of the important activities. In such circumstances, we have developed Pb-free Flip-chip Ball Grid Array (FC-BGA) package for Low-k devices using organic substrate. From our experiments on 1296pin FC-BGA package with 12.4 x 12.4 mm size chip, it is concluded that applying solder bump composed of Sn-1.0Ag-0.5Cu and the low stress underfill with Tg 110 o C will realize the Pb-free FC-BGA on Low-k device.

Thermo-electromigration phenomenon of solder bump, leading to flip-chip devices with 5,000 bumps

High performance logic devices have rapidly advanced in network system. In order to reply the demand of high pin count and high speed, Flip-chip BGA (FC-BGA) package applied high-density organic substrate has been developed. This package has the superior possibility of flexible bump locations by virtue of high via densities and fine line capabilities of the substrate. The feature of substrate is adopting the stacked method of finer via pitch layers. Utilizing the density, it is possible to either minimize the LSI die size or maximize the number of bumps on the die. Also at the high performance devices, the high current density through the bump is strongly demanded. In order to satisfy the demand and realize the high pin counts devices, thermo-electromigration phenomenon of solder bump is one of the key reliability items. The thermo-electromigration phenomenon of solder bump was investigated to be consisting of three steps as below. At 1/sup st/ step, the lead (Pb) migrates as electron flow under high-density current, and at 2/sup nd/ step, the Under Bump Metals (UBM) migrates and disappears. Finally at 3/sup rd/ step, Aluminum (Al) routing metal migrates and it results in open failure, and from the High Temperature Operating Life (HTOL) results, the life time of solder bump on current density has been estimated theoretically based on Blacks equation. The lifetime was predicted more than 20 years with the current being 160 mA/bump in 220 /spl mu/m pitch cases.

Thermally enhanced flip-chip BGA with organic substrate

A thermally enhanced Flip-chip BGA package (FC-BGA) with organic substrate has been developed. The package is proud of the high thermal and electrical performance due to the flip-chip interconnections, and the optimized heat spreader attached directly on to the die. Besides, the eutectic solder bumps (Pb63wt% Sn) have realized high reliability of flip-chip interconnections, compared with the high melting point solder bumps (Pb-3wt% Sn connected with Pb-63wt% Sn).