Study on EMI Shielding at the PCB Strip Level with Conformal Spray Coating Process

We demonstrated the new strip-level EMI shielding process with a spray method. Test PKGs having dimension of 300um width and l, 200um height were fabricated to evaluate feasibility of strip-level EMI shielding. As a result, spray can coat the total area of trench inner side wall with the special spray coating material and optimized spray parameters. Moreover, we measured the near-field shielding effectiveness(SE) of sputtering and spray films. 5.9um-thick sputtering one and 5.4um-thick Ag ink sprayed were prepared and measured in near E- and H-field in the range of 30MHz~1.5GHz. In E-field, The SE results showed 21dB at 800MHz and 55dB at 100MHz. In H-field, the SE result of 5.4um-thick Ag ink was 1~2dB higher than 5.9um-thick Sus/Cu/Sus film.