Fig. 1 ( a ) and ( b ) A 3D schematic and A – A′ cross section of the straight microchannel ( μ -channel) cooler, where L 1 is the flow travel distance of the coolant along the length of the μ -channel. ( c ) and ( d ) A 3D schematic and B – B′ cross section of the 3D manifold μ -channel ... More about this image found in ( a ) and ( b ) A 3D schematic and A – A′ cross section of the straight m...

Fig. 2 ( a ) Laser microscopy image of the unpolished copper with a rough surface at the contact interface. The circled regions show the voids that decrease the actual contact area of the two DBCs. ( b ) SEMs of the DBC point-contact bonding using a relatively thick (10  μ m) electroplated Sn laye... More about this image found in ( a ) Laser microscopy image of the unpolished copper with a rough surface ...

Fig. 3 Schematics of the layout of the μ -channel and manifold. ( a ) μ -channel DBC and ( b ) manifold DBC. The actual geometry of the microchannel and the manifold will change after the surface polishing process. Details of the changes in the feature size are discussed in Sec. 2.3 and the Ap... More about this image found in Schematics of the layout of the μ -channel and manifold. ( a ) μ -channel...

Fig. 4 ( a ) Schematics of the contact interface of the two DBC substrates. ( b ) The overlapped microscopic image of the two DBC substrates taken by the light-splitter microscope of the flip-chip bonder. ( c ) Schematic of the point contact of the two DBC substrates. The red box is the region of ... More about this image found in ( a ) Schematics of the contact interface of the two DBC substrates. ( b ) ...

Fig. 5 Schematics of the fabrication process. The schematic is not in scale to the actual DBC sample, and the thickness of the Sn layer is exaggerated. The actual thickness of the Cu layer and Sn layer is approximately 300  μ m and 1–2  μ m, respectively. More about this image found in Schematics of the fabrication process. The schematic is not in scale to the...

Fig. 6 ( a ) The laser-optical microscopic images of the DBC samples after different polishing durations. ( b ) Variation of the mean roughness depth ( R z ) of different polishing durations. More about this image found in ( a ) The laser-optical microscopic images of the DBC samples after differe...

Fig. 7 ( a ) Profile measurement of the DBC copper layer after different polishing durations. The thickness of the copper layer is defined by the difference between the plateau region and the reference AlN layer. The two profiles are aligned at the side wall of the channel for the comparison of th... More about this image found in ( a ) Profile measurement of the DBC copper layer after different polishing...

Fig. 8 The variation of the copper layer thickness after different polishing durations More about this image found in The variation of the copper layer thickness after different polishing durat...

Fig. 9 Variation of the microchannel width after different polishing durations More about this image found in Variation of the microchannel width after different polishing durations

Fig. 10 ( a ) SEM images of the cross section of the laser-cut microchannel after electroless plating of Sn. The copper surfaces are covered with the electroless plated tin solder. ( b ) Laser microscopy image of the cross section at the Cu surface with electroless-plated Sn. The bright color show... More about this image found in ( a ) SEM images of the cross section of the laser-cut microchannel after e...

Fig. 11 ( a ) The experimental setup for the bonding of the two DBCs. The samples larger than 6 × 6 mm are used in this study. However, the overlapping area of the two DBCs is 6 × 6 mm. The silver color of the copper layer indicates the electroless-plated Sn on the copper surface. ( b ) Temperatur... More about this image found in ( a ) The experimental setup for the bonding of the two DBCs. The samples l...

Fig. 12 ( a ) Schematic of the sample assembly for the tensile strength test. The sample holder is made of aluminum. ( b ) The tensile strength test setup. The sample is centered by fine-tuning the clamper. More about this image found in ( a ) Schematic of the sample assembly for the tensile strength test. The s...

Fig. 13 Schematic of the contact interface after the polishing process. The increase of channel width and decrease of the point-contact area are a result of the chemical polishing. More about this image found in Schematic of the contact interface after the polishing process. The increas...

Fig. 14 The top view of the SEM image of the copper surface after each fabrication steps: ( a ) after chemical polishing for 15 min, ( b ) after electroless plating for 10 min, and ( c ) after heated to 300 °C for 10 min More about this image found in The top view of the SEM image of the copper surface after each fabrication ...

Fig. 15 Investigation of the failure surface after the tensile strength test. The failure surface and the microchannel are investigated with the laser microscopic 3D profilometer. The area circled by the red box is the region of the point-contact bonding. More about this image found in Investigation of the failure surface after the tensile strength test. The f...

Fig. 16 SEM images of the failure surfaces of the μ -channel sample with bonding time of 30 min. The result is compared to the previous literatures to identify the surface morphology of the specific fracture type and material. More about this image found in SEM images of the failure surfaces of the μ -channel sample with bonding t...

Fig. 17 SEM images of the failure surfaces of different bonding times. The second row shows the enlarged view of the μ -channel and bonded area. The circled areas are the locations of the remaining Sn. More about this image found in SEM images of the failure surfaces of different bonding times. The second r...