A shielding structure with conductive adhesive coated on molding compound in 3D package

Abstract

As electronic products tend to higher density, smaller area, lighter weight, and etc., three-dimensional (3D) packages are becoming effective chooses. Advanced 3D package technologies make the electronic products smaller with high density, but bring in more serious problems. The electromagnetic interference (EMI) is an important issue for more complex electromagnetic environment and smaller distance between noisy sources and sensitive circuits in the 3D package, especially in mixed signal system or RF/Microwave system. In this paper, a shielding structure with conductive adhesive covered on molding compound is researched. The shielding structure contains the molding compound, the conductive adhesive, and the ground plane and grounding vias. The conductive adhesive coated on the molding compound, and connects the ground plane or grounding vias on the top of substrate. To study the shielding performance, Device Under Tests (DUTs) are designed and fabricated in this paper. The test dies with Electro-Magnetic Coil are fabricated for DUTs to compare the isolation effect. The shielding performance of DUTs is measured by test system, which contains Vector Network Analyzer (VNA), coaxial cables and DUTs. The shielding efficiency (SE) of the novel structure is about 25dB below 8GHz, and the SE for high frequency is relative higher due to skin depth decreasing. The process of hybrid package with shielding structure is compatible with the normal package technology. The only additional step is the conductive adhesive coating. It is an effective method for suppressing near field noise in 3D mixed signal or RF/ Microwave package.