Thermo and mechanical study on integrated high-density packaging

With the demanding of market, the electronic portable products can be characterized by increasing signal frequencies and higher density of functions. The electronic products are expected to be produced smaller and smaller. There is one way to meet the requirement, which is a three- dimensional integration of components. A new concept of a packaging structure is proposed based on an embedded chip structure. Chips and other components can be embedded directly into epoxy and then interconnections are realized by laser drilling and metallization. In the process, components are placed on a removable tacky film on a temporary or permanent base. The film and base temporarily immobilize them until the structure is encapsulated. The entire array of tested and burned-in components thereby becomes a monolithic assembly, with each component now permanently immobilized by every part of it. The bottoms of these terminations can be exposed by removing the temporary base and film or by making holes in a permanent one by such means as mechanical abrasion, water-jet material removal, or laser ablation. The assembly is now ready to be metalized with copper using standard printed circuit additive (build-up) processing methods, with circuit patterns created to make the required interconnections among leads of all of the components. In most cases, more than one layer will be required, so an insulation layer is placed over it and the process is repeated until all required interconnections are made. Thermal and thermo-mechanical reliability are taken into account in this structure due to the encapsulation on the chips. For this purpose, numerical study by means of finite element analysis is available to check the desired properties. Thermal analysis aims to give the first insight to characterize the thermal performance for such structure under steady and transient condition. Epoxy around the chip also plays an important role in the heat dissipation. The thickness of copper has large influe- - nce on the thermal resistance. Besides, the copper in the top metallization layer of the package is also taken into account. Thermal stress between the copper and the epoxy is also considered in this paper.