Yoshinori Yokoyama

Development of 30 micron pitch bump interconnections for COC-FCBGA

We developed the flip-chip bonding technology on chip-on-chip (COC) package with ultra-fine pitch bump, which leads advanced high performance devices. On this package, the realization of the metallographic behavior in the micro-bump interconnection is the substantial issue for achieving good bondability and reliability. In this paper, to implement flip-chip BGA package with COC structure (COC-FCBGA), the metal systems of micro-bump and the dimension especially metal plating thickness have been optimized by precise analysis. And it is confirmed that the specification we fixed on this package would meet sufficient quality level for fine pitch bonding. This COC-FCBGA technology will meet demands for high-end system solutions in very near future

Variable-Size Solder Droplets by a Molten-Solder Ejection Method

We have developed a molten-solder ejection method by which molten-solder droplets from a 13- (1 pL) to 450- mum (48 nL) diameter could be realized. This method has been developed as a technique to supply small solder balls. The authors have developed a newly designed solder ejection head and confirmed that solder balls with almost no surface oxidation can be formed by using this method. The diameter of the molten-solder droplets using an advanced head is 13 mum, which is much smaller than the 35 mum of a conventional minimum droplet. As the relative positioning accuracy, a standard deviation of 0.81 mum was achieved when the diameter of the solder droplets was 13 mum. Furthermore, by changing the drive waveform of the conventional head, we enlarged the diameter of the solder droplets to 450 mum, which was much larger than 200 mum of a conventional maximum droplet. In this case, the standard deviation of 26 mum as the relative positioning accuracy was also achieved when the diameter of the solder droplets was 450 mum.

Micro-optical switch with uni-directional I/O fibers

The authors have developed a new 2/spl times/2 micro-optical switch. The switch features a uni-directional input/output and a drive mechanism with latch functions. The newly developed structure combines two moving mirrors and a fixed V mirror to implement a 2/spl times/2 micro-optical switch with uni-directional input/output. Furthermore, the moving mirrors have been reduced in size by integrating the drive and latch functions by the use of magnetic shaft mirrors and driving coils. The micro-optical switch has been implemented as a module mounted in a ceramic package. The modular switch is 23.5/spl times/9.86/spl times/6.76 mm in size and provides a switching time of 1.3 ms for 15 V (469 mA) and an input pulse width of 1 ms. The reflectivity of the moving mirror is 98.6% (reflection loss: 0.06 dB) and the connection loss between the fixed mirror surfaces is 5.4 dB.

One picoliter ejection of solder droplets by an advanced molten solder ejection method

We have developed an advanced molten solder ejection method which realizes to eject 1 picoliter molten solder droplets. The molten solder ejection method has been developed as a technique to supply small solder balls. The authors have developed a newly designed solder ejection head and have confirmed that solder balls with almost no surface oxidation can be formed by using this head. The size of the molten solder droplets using this newly developed method is 1 picoliter, which is much smaller than the previous minimum droplet size of 22 picoliters. A standard deviation in position accuracy of 0.81 mum was achieved.

Active micro heat transport device using thermal pumping system

We have developed a thermal pumping system for loop-type micro channels, realizing an active micro heat transport device capable of highly efficient cooling. The thermal pumping system makes use of the time change in the vapor pressure of the working fluid as the driving force for fluid circulation. Because it has no mechanically moving elements, it is highly reliable and moreover is effective in preventing deterioration in the heat transport rate due to miniaturization. We set up a system with two thermal pumps within one loop for efficient heat transportation. We fabricated a looped micro-channel, which has a width of 600 /spl mu/m, a depth of 120 /spl mu/m and a channel length of 220 mm. We confirmed a flow rate of 12.5 mm/s at the driving frequency of 1 Hz, enabling a heat transport of 0.16 W.