Three-dimensional multi-layer through-hole filling properties of solderable polymer composites with low-melting-point alloy fillers

A novel three-dimensional (3D) multi-layer through-hole filling process using solderable polymer composites (SPCs) was developed to overcome several limitations of the conventional 3D package technique. To investigate the multi-layer through-hole filling properties of SPCs, SPCs with functionalized polymer composite and low-melting-point-alloy (LMPA) fillers were formulated, and a multi-layer through-hole filling test was conducted under atmospheric pressure and decompression reflow conditions. The results indicated that the multi-layer through-hole filling assemblies under the atmospheric pressure reflow condition have weak through-hole filling and interlayer interconnection properties because of the weak elimination of residual polymer composite and voids within the through-hole. Meanwhile, the multi-layer through-hole filling assemblies reflowed under the decompression condition showed improved through-hole filling properties because of the favorable elimination of polymer composite and voids within the through-hole and the excellent wetting behavior of molten fillers. The corresponding electrodes between the stacked boards were electrically interconnected by the proper selective wetting behavior of molten LMPA, and the spaces between stacked boards were underfilled by the cured polymer composite.