The disclosure generally relates to methods for manufacturing a filled gap region or cavity between two surfaces forming a device microchip. In one embodiment, the cavity results from two surfaces, for example, a PCB and a chip or two chips. More specifically, the disclosure relates to a method of manufacture and the resulting apparatus having porous underfill to enable rework of the electrical interconnects of a microchip on a multi-chip module. In one embodiment, the disclosure builds on the thermal underfill concept and achieves high thermal conductivity by the use of alumina fillers. Alternatively, other material such as silica filler particles may be selected to render the underfill a poor thermal conductive. In one embodiment, the disclose is concerned with reworkability of the material.

The present application discloses a semiconductor device. The semiconductor device includes a package structure including a first side and a second side opposite to the first side; an interposer structure positioned over the first side of the package structure; a first die positioned over the interposer structure; a second die positioned over the interposer structure; and a plurality of bottom interconnectors positioned on the second side of the package structure, and respectively including: a bottom exterior layer positioned on the second side of the package structure; and a cavity enclosed by the bottom exterior layer.