Adhesion stress

Table 6.1 Effect of modulus, expansion coefficient, and temperature on adhesive stress ... 

Besides delamination, actual cracking of silicon die is a failure mode that can occur from excessive adhesive stresses, voids, and moisture absorption. Residual stresses in adhesive-attached single-chip devices become critical as the size of the device increases and dissimilar die and leadframe materials are used. Several types of fractures that can occur within the die or within the adhesive are shown in Fig. 6.8. A hairline crack in an 1C chip that resulted from adhesive stress is shown in Fig. 6.9. 

Figure 6.9 Fracture in silicon IC device resulting from adhesive stress. (Courtesy CALCE Electronic Products and System Center, Univ. of Maryland.)...

In this formula, C and

adhesion stress of the coahtion and internal friction angle, with the above expression (4) substituted into this formula, we can conclude ... 

Table 6.1. Effect of Modulus, Expansion Coefficient, and Temperature on Adhesive Stress ... 

This chapter assesses the effect of miniaturizing on adhesion issues. First, it is demonstrated that adhesion stress improves as bodies get smaller. But there is a limit of elasticity which has a strong influence. The ultimate adhesion experiment is with a single atom. This experiment is on the point of being carried out. It has important implications for the future of adhesion science. 

Figure 14.15. (a) Results showing the change in adhesion force with diameter and thickness, (b) Meissner and Merrill results for adhesion stress in butt joint, ... 

The methods developed over the last decade or so to predict failure employ in-bondline non-linear adhesive characterisation. This in turn requires some fairly sophisticated experimental techniques, carefully conducted for a range of test conditions and environments. Hart-Smith concluded that a precise representation of the adhesive stress-strain characteristic is not important. He maintains that the... 

It is evident that a large number of parameters are involved in the fabrication and testing of bulk adhesive specimens and adhesive joints these must be controlled if meaningful experimental data are to be obtained. Joint tests evaluate not only the mechanical properties of the adhesive, but also the degree of adhesion and the effectiveness of surface treatments. The standard test procedures listed by ASTM, BSI, DIN and other official bodies are essentially for testing adhesives and surface treatments rather than joints (e.g. Table 4.3). Unfortunately, most of these tests consist of joints in which the adhesive stresses are far from uniform. The designer and the researcher therefore have to select appropriate tests, and to know what the results mean in terms of their own particular investigations and applications. 

Adams and Wake (reference 5.17) considered the adhesive stresses and adherend direct stresses acting across the width of an adhesive joint. They included the adherend shear stresses but neglected the effects of bending, thus excluding peel stresses. They used a... 

FIGURE 7.13 Four basic types of adhesive stress. 

The mechanical properties of the natural fiber-reinforced composites are dependent on some parameters such as volume fraction of the fibers, fiber aspect ratio, fiber-matrix adhesion, stress transfer at the interface, and fiber orientation [32]. Several studies on natural fiber-reinforced composites involve mechanical properties characterization as... 

Fig. 2. Examples of (a) incorrect and (b) correct averaging of adhesive stresses from the...

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