Substrate-attach adhesives specifications

The first specifications for adhesives were generated by the staff of NASA and the DoD who were prompted by the high reliability that was required of microcircuits used in aerospace programs. These specifications covered primarily die and substrate attachments for hermetically sealed integrated circuits, hybrid microcircuits, and multichip modules. Subsequently, with the increased use of surface-mount adhesives in the assembly of commercial printed-wiring boards and underfills for flip-chip devices, industry associations took the lead in generating the requirements and test methods. 

Electrical-stability testing is essential for conductive adhesives used for electrical connections. Electrical conductivity can degrade at elevated temperatures, on aging with or without power, and on exposiue to humidity and temperature. The specific test method used depends on the application. One test used for die-attach adhesives specified in NASA MSFC-SPEC-592 (now inactive) involves a series of gold-plated Kovar tabs attached with conductive epoxy to metal pads on an interconnect substrate. In the test vehicle, a bias of 5 V and cmrent density of 139 3.9 A7cm (900 A/in ) are applied to a series of wire-connected tabs, and the resistance change is measured after exposure to 150 °C periodically up to 1,000 horns. The maximum allowable resistance change is 5%. 

W. quantifies the specific, discrete interactions that exist between a wetting liquid and a substrate. These interactions may be Van der Waals, acid-base, or covalent. The reversible work of adhesion is the product of the areal density of these interaction sites (or attachment points) and the energy per attachment point ... 

A variety of substrate- and cell-attached factors influence neural development by regulating adhesion properties of cells (see Ch. 7). Interactions occur directly between cells or between a cell and the extracellular matrix (see Ch. 2). The molecules mediating these interactions have been implicated in regulating the specificity and timing of cell-cell adhesion and the consequences on cell morphology and physiology. Hence, they influence the ability of cells not only to migrate but to sort themselves out and to stabilize spatial relationships considered important for the process of differentiation. 

GRGDS the resonance frequency does not indicate any cell adhesion to the resonator surface. In contrast, when SDGRG is added to the culture fluid, there is no difference compared to experiments in which no peptide is present at all (compare Fig. 2a). Thus, when specific interactions between cell-surface receptors and substrate-immobilized proteins are not allowed to form, we do not observe any measurable impact on QCM readings. Apparently, loose attachment of the cell bodies to the substratum does not produce any significant acoustic load [12,16]. 

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