Micro-3D-Printed Packaging Substrates With Embedded Through Holes for Organic Interposers

The rapid progress of three-dimensional (3D) printing technology offers significant advantages to produce small-batch, diverse products. Recent breakthroughs in 3D printing allow for the fabrication of micro-sized geometries with exceptional efficiency. This study introduces the concept and feasibility demonstration of additively manufactured package substrates, specifically designed for fanout or chiplet applications, utilizing a specific type of high-resolution digital light processing 3D printing technique. The employed 3D printing approach utilizes photolithography to construct a 3D model based on photosensitive polymers, achieving an impressive minimum pixel size of 2 or 10 μm. The polymer packaging substrates, featuring a through-hole diameter of 100 μm and a 5×5 mm area with a thickness of one millimeter, were successfully printed. Layout compensation in computer-aided design software ensured precise hole formation. To address the challenge of electroplating a high aspect ratio through holes (1:10), substrates underwent surface treatment involving oxygen plasma treatment and low-temperature atomic layer deposition (ALD). Electroless plating, combined with ALD surface treatment, exhibited significantly enhanced uniformity compared to the absence of ALD. Rigorous measurements of substrate material characteristics, including the coefficient of thermal expansion and dielectric constant/loss, were conducted to determine its suitability for integration into electronic devices. Looking forward, the integration of high-resolution 3D printing in package substrate manufacturing holds immense promise for advancing the efficiency and precision of system-in-package prototyping. This approach to creating intricate geometries and micro-sized features may revolutionize the landscape of electronic packaging, paving the way for cost-effective and customizable packaging solutions.