Small-outline ICs

Figure 4. Small-outline IC package with 16 gull-wing leads on a 50-mil pitch (1 mil = 0.001 in. = 25.4 im). (Reproduced with permission from reference 28. Copyright 1985 Institute of Electrical and Electronics Engineers.)...

Figure 1 also shows the small outline IC package (SOIC), which... 

Eccobond D125F/Henkel Stencil application for surface-mount devices (capacitors, resistors, small outline ICs, and plastic leadless chip carriers) N/A N/A N/A... 

Stencil thickness should be determined by the highest dot size needed to make contact with the part. In most cases, the dot height should be 1.5 to 2 times the standoff height. Mostpassive components require stencils that are at least 6-8 mils thick. Farge, small-outline ICs (SOICs) require stencils that are 10-12 mils thick. A specific example in the use of these guidelines is... 

A. QSOP, or Quad Small Outline Package, is a type of IC package that is usually surface mounted and used for VLSI applications. 

QSOP (Quad Small Outline Package) A type of IC package that has all leads soldered directly to the circuit board. Also called a surface mount chip. 

Small outline transistor (SOT), a plastic leaded package originally for diodes and transistors but also used for some ICs (such as Hall effect sensors). Some common sizes are SOT-23, SOT-26, SOT-223, and the very small SOT-523. 

Dual-inline memory module (DIMM), pioneered by Hitachi, has memory chips mounted on both sides of a PC board (with 168 pins, 84 pins on each side). The DIMM has keying features for 5-, 3.3-, and 2.5-V inputs and for indicating whether it is made with asynchronous DRAMs or flash, static random access memory (SRAM) or DRAM ICs. There is also the SO DIMM or small outline dual in line memory module, which has 72 pins vs. 168 for standard DIMM modules. 

Basic SMD ICs come in a wide variety of packages, from 8-lead small outline packages (SOLs) to 208-lead quad flat packs (QFPs). Examples ofSO20 and QFP128 packages are shown in Fig. 11.18. 

The mechanical concepts of stress are outlined in Fig. 1, with the axes reversed from that employed by mechanical engineers. The three salient features of a stress-strain response curve are shown in Fig. la. Initial increases in stress cause small strains but beyond a threshold, the yield stress, increasing stress causes ever increasing strains until the ultimate stress, at which point fracture occurs. The concept of the yield stress is more clearly realised when material is subjected to a stress and then relaxed to zero stress (Fig. Ih). In this case a strain is developed but is reversed perfectly - elastically - to zero strain at zero stress. In contrast, when the applied stress exceeds the yield stress (Fig. Ic) and the stress relaxes to zero, the strain does not return to zero. The material has irreversibly -plastically - extended. The extent of this plastic strain defines the residual strain. 

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