Miniaturization of electronic devices has been strongly pursued to facilitate ubiquitous computing. High-density packaging technology is a promising candidate for reducing device size. For producing high-density packaging, metallization is an important process. Electroless nickelphosphorus plating, the most popular metallization method, is available for insulator materials such as silicon nitride (SiN) and polyimide (PI). For this study, we investigated three materials for substrates, PI as a resin, SiN as a passivation film, and aluminum (Al) as a metal. The values of adhesion strength between the electroless Ni-P film and three substrates were evaluated quantitatively using a stud pull test. A commercially available weak alkaline degreasing agent (aluminum cleaner NE-6; Meltex Inc.) is effective for metallization of PI, SiN, and Al simultaneously without a zincate process. These three materials are common used for a wafer level chip size package (W-CSP), which is a newly developed high-density packaging technology. Using the degreasing agent, we obtain sufficient adhesion strength for three substrates: PI, SiN and Al.The optimum concentration of the degreasing agent is 45 g/dm3 for all substrate materials. Results show that the electroless Ni-P plating process is suitable for metallization of high-density packaging.
