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Keywords
Thin-film, Laminated structures, Interconnection
Abstract
A novel interconnect technology, introducing thin film on a laminate substrate base, is presented. A specially constructed laminate board is used as a substrate for the thin film build-up process. The main characteristics of the laminate core substrate are the z-axis electrical connections, the absence of holes in the substrate and the very flat nature of the top surface. As a result, the base substrate can be processed further in a thin film processing line. The manufacturing and properties of these substrates are discussed.
1. Introduction
Requirements for higher reliability, better performance and lower system cost are the driving forces behind the current development of new high density packaging (HDP) technologies and miniaturized electronic systems. Different technological approaches are available to achieve high density interconnection structures. These are generally based on improvements on existing technology, such as printed circuit board, co-fired ceramic or thin film technology. Each of these technologies has their specific merits and drawbacks.
When it comes to achieving the highest interconnection density with the best electrical performance, the multilayer thin film technology is now generally accepted as the highest performance technology. Feature sizes of lines and spaces in this technology can easily go down to 20 or even 10mm. A very dense interconnection pattern can be realised using only two fine-line routing layers.
These thin film structures are generally produced on silicon, glass, ceramic or even metallic substrates that have only a function as carrier for the thin film layers. After assembly of the die on such a substrate, the substrate itself needs to be packaged. This is an important disadvantage, compared to laminate or ceramic high density interconnect substrates. These can be considered as ball-grid-array "interposer" substrates, therefore not requiring any additional packaging, except for overmoulding and solder-- ball attachment.
In this paper, a novel approach is presented, combining the thin film high density interconnection capabilities with that of advanced build-up laminate board technologies. Using the MCM-terminology, it can be denoted as an MCM-SLID technology: thin film (D) on top of a sequentially laminated (SL) printed circuit board. The work presented is part of a project conducted with support from the European Commission, project Esprit Nr. 2680 "FLIPAC" (Joly and Lambert, 1999).
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