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Advantages of Anisotropic Conductive Films (ACF) technology, especially the low bonding temperature, fine pitch capability, elimination of lead and low cost, have resulted in ACF interconnects being widely used in contemporary portable electronic devices. Such products are exposed to various types of mechanical loadings, such as shock and impact during handling and accidental drops, throughout their...
This study focuses on quasi-static mechanical cycling durability of copper traces on printed wiring assemblies (PWAs). PWA specimens populated with Land Grid Array (LGA) components on copper-defined pads were cycled to failure under zero-to-max, three-point bending. Failure is defined in terms of electrical opens due to fatigue damage propagation through the entire cross section of the trace. Failure...
The continuing increase of functionality and miniaturization in handheld electronics has resulted in a decrease in the size and weight of the product. Therefore, internal structures such as printed wiring boards (PWBs) are becoming more slender, thus increasing the likelihood of unintentionally causing contact between the PWB and other internal structures like battery compartments, displays, and other...
Advances in drop tower technology have extended the range of obtainable accelerations in drop testing from 5,000 Gs to as much as 100,000 Gs. To achieve excitations in excess of the conventional 5,000 Gs, a mechanical accelerator, called the Dual Mass Shock Amplifier (DMSA), is mounted on the drop table. This device produces extremely high, short duration shock amplitudes, by using secondary impacts...
In the conversion to Pb-free electronics, there has been increasing interest in conductive adhesive interconnects, as they combine Pb-free materials with the added benefit of low temperature, processing (Lau et al., 2002). This paper explores the degradation mechanisms and kinetics in adhesively bonded Au-bumped flip chip interconnects. Earlier researchers have suggested that electrical contact is...
This paper presents a study of the probabilistic effects that act in addition to deterministic (mechanistic) effects to reduce the thermal cycling durability of ball grid array (BGA) interconnects as the component I/O count increases. The mechanistic drivers include increasing thermal expansion mismatch with increasing package size and increasing stress levels with decreasing solder joint size. The...
Most studies on modeling cyclic thermo- mechanical fatigue of solder interconnects consider only the steady-state creep behavior of solder materials. This study explores the effect of including the primary creep behavior; since it may represent a significant portion of the total viscoplastic deformations in Pb-free Sn3.0Ag0.5Cu (SAC305) solder (G. Cuddalorepatta et al., 2007). The solder constitutive...
This study investigates the time dependent behavior of lead-free hypoeutectic Sn3.0Ag0.5Cu solder using a combination of experimentation and modeling. Experimental data for hypoeutectic Sn3.0Ag0.5Cu (SAC) is obtained from stress relaxation tests at different temperatures and different initial stress levels, and compared with the benchmark eutectic Sn37Pb, using a modified lap shear test. The test...
The thermal cycling durability of large-area Pb-free (Sn3.5Ag) solder interconnects on photovoltaic (PV) solar laminates, has been studied and benchmarks against existing Sn36Pb2Ag interconnects, using a combination of accelerated testing and physics-of-failure (PoF) modeling. Accelerated thermal cycling tests conducted on photovoltaic laminates of both solder compositions, show that the interconnect...
This study presents simulation of damage initiation and propagation in solder joints with voids, under thermo-mechanical loading. A three dimensional, global-local, visco-plastic FEA is conducted for a CTBAG132 assembly under thermal cycling. The displacement results of the global FEA at the top and bottom of the critical solder ball are used as the boundary conditions in a local model which focuses...
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