Лако-красочные материалы — производство

The most significant application for conductive adhesives in the manufacture of micro­electronics is the attachment of silicon chips to lead frames. Of the 40 billion integrated circuits (ICs) manufactured each year, approximately 90% are encapsulated in plastic — molded packages, and most of these are assembled with conductive adhesives [4]. A sche­matic illustration of a plastic-molded IC package is shown in Fig. 2. The conductive

adhesive forms the mechanical as well as electrical interconnection between the back side (ground plane) of the die and the plated copper lead frame. Initially, gold eutectic bonding was used for this die attach application. Several disadvantages to this process were encountered, however, including elevated assembly temperatures, cost of materials, and especially the stresses induced by coefficient of thermal expansion (CTE) mismatches [5]. Alternative interconnection materials were later developed, including silver glass materials for hermetic packages and conductive adhesives for nonhermetic applications. A review of these three die attach technologies has been published [6].

Adhesives gained acceptance rapidly, despite the industry’s reluctance to incorporate organic materials in microelectronic packages, due to the following advantages:

Low cost

Low assembly temperatures Low-stress joints High thermal conductivity High purity Excellent reliability

Easy integration into the manufacturing line

Conductive adhesives also form sufficiently robust joints that withstand the temperatures and pressures experienced during wirebonding and over molding. The formulation of die attach materials is discussed in Section IV.