Potting Compounds Protect Electronic Circuits

(15 October 2015)  Potting and encapsulation compounds are designed to completely enclose a component, module or PCB. This effectively shields the unit from its surroundings while providing structural support and imparting the highest protection from external conditions. There are a variety of potting formulations on the market today that suit the needs of diverse applications. However, a balance must be developed when deciding on the best material. Read more

Dependence of overcurrent failure modes of IGBT modules on interconnect technologies

(28 September 2015)  Insulated gate bipolar transistor (IGBT) modules which can fail to short circuit mode have great of applications in electricity network related fields. Single IGBT samples have been constructed with the standard Al wire bonding, flexible printed circuit board (PCB) interconnect and sandwich structure technologies. The overcurrent failure modes of the constructed IGBT samples have been tested under a range of energy levels, and the structures of the tested samples have been characterized with scanning electronic microscopy and three-dimensional X-ray computed tomography imaging. The results obtained indicate that the IGBT samples constructed with the three interconnect technologies can fail to both open circuit mode and short circuit mode. Read more

Amkor’s Arcedera takes on MEMS packaging standardization

(September 2015)  Adrian Arcedera, VP, MEMS & Sensors at Amkor Technology, was a presenter at the CHInano 2015 Conference & Expo – International Conference on Commercialization of Transducer & MEMS (10/28-10/30/15, Suzhou, China). He tackled the topic of MEMS packaging standardization (10/28/15) at the conference and responded to questions posed to him during an interview with Chip Scale Review.  Read more

Investigation of Stress in MEMS Sensor Device Due to Hygroscopic and Viscoelastic Behavior of Molding Compound

(7 July 2015)  The stresses due to moisture saturation on microelectromechanical systems (MEMS) sensor devices after exposure to temperature cycling have been addressed. Moisture-, temperature-, and time-dependent material property of molding compounds for the MEMS devices were characterized. To determine the coefficient of hygroscopic swelling of a molding compound and diffusivity (D) of water in the molding compound, dimensional change and weight loss of moisture saturated samples at various temperatures were monitored by the digital image correlation method combined with a weight scale. To obtain the viscoelastic property of the molding compound, a series of stress relaxation tests was performed using dynamic mechanical analysis (DMA). Read more

Silicones Meet the Needs of the Electronics Industry

(12 May 2015)  Remarkable silicones. The combination of their unique ability to maintain physical properties across a wide range of temperature, humidity, and frequency–combined with their flexibility–set them apart. Silicone based adhesives, sealants, potting and encapsulation compounds are used in hundreds of consumer, business, medical, and military electronic systems. In this white paper, learn what makes silicones different from other organic polymers, why their properties remain stable across different temperatures, and how they have played a major role in the rapid innovation of the electronics industry. Read more

Integrated hygro-swelling and thermo-mechanical behavior of mold compound for MEMS package during reflow after moisture preconditioning

(11 April 2015)  The purpose of this paper was to study the combined effect of hygro and thermo-mechanical behavior on a plastic encapsulated micro-electro-mechanical systems (MEMS) package during the reflow process after exposed to a humid environment for a prolonged time. Plastic encapsulated electronic packages absorb moisture when they are subjected to humid ambient conditions. Read more

Optimal Material Properties of Molding Compounds for MEMS Package

(10 October 2014)  In this paper, an optimization study of molding compounds for a microelectromechanical systems (MEMS) sensor package has been performed. A comprehensive finite element analysis model was established for the MEMS sensor package to assess the stresses and deformations when the package was subjected to temperature loading. A series of stress relaxation tests were performed to characterize the viscoelastic material properties of a molding compound over temperature with dynamic mechanical analysis. A master curve for the molding compound was constructed by a proper shift function and the Prony pairs were obtained by curve fitting to be implemented in the simulation. Read more

A Note on the Normalized Approach to Simulating Moisture Diffusion in a Multimaterial System Under Transient Thermal Conditions Using ANSYS 14 and 14.5

(September 2014)  Moisture can have significant effects on the performance and reliability of electronic components. Accurately simulating moisture diffusion is important for designers and manufacturers to obtain a realistic reliability evaluation. Beginning with version 14, ANSYS is capable of simulating diffusion and related behaviors, such as hygroscopic swelling, with newly developed elements. However, a normalized approach is still required to deal with the discontinuity of concentrations at the material boundaries, and normalization of the moisture concentration in transient thermal conditions is tricky. Read more

Three-Dimensional and 2.5 Dimensional Interconnection Technology: State of the Art

(March 2014)  Three-dimensional (3D) packaging with through-silicon-vias (TSVs) is an emerging technology featuring smaller package size, higher interconnection density, and better performance; 2.5D packaging using silicon interposers with TSVs is an incremental step toward 3D packaging. Formation of TSVs and interconnection between chips and/or wafers are two key enabling technologies for 3D and 2.5D packaging, and different interconnection methods in chip-to-chip, chip-to-wafer, and wafer-to-wafer schemes have been developed. Read more

Phonon dispersion and quantization tuning of strained carbon nanotubes for flexible electronics

(2014)  Graphene and carbon nanotubes are materials with large potentials for applications in flexible electronics. Such devices require a high level of sustainable strain and an understanding of the materials electrical properties under strain. Using supercell theory in conjunction with a comprehensive molecular mechanics model, the full band phonon dispersion of carbon nanotubes under uniaxial strain is studied. The results suggest an overall phonon softening and open up the possibility of phonon quantization tuning with uniaxial strain. Read more

Electromigration damage mechanics of lead-free solder joints 4 under pulsed DC: A computational model

(5 January 2013)  A numerical method for studying migration of voids driven by pulse electric current and thermal gradient in 95.5Sn–4Ag–0.5Cu (SAC405) solder joints is developed. The theoretical model involves coupling electron wind force, chemical potential, joule heating and stress gradient driving mass diffusion processes. Entropy based damage criteria is adopted to characterize the mass transportation mechanism, which utilize irreversible entropy production rate as a measure of material degradation. Read more

Reliability Assessment of Preloaded Solder Joint Under Thermal Cycling

(December 2012)  The ever increasing power density in modern semiconductor devices requires heat dissipation solution such as heat sink to remove heat away from the device. A compressive  loading is usually applied to reduce the interfacial thermal resistance between package and heat sink. In this paper, both experimental approaches and numerical modeling were employed to study the effect of compressive loading on the interconnect reliability under thermal cycling conditions. Read more

(September 2012)  In order to protect the electronic components of electronic devices on a printed circuit board (PCB) against electromagnetic radiation, a conductive shield-can or box is normally attached to the PCB covering the electronic components. In particular, handheld electronic devices are prone to be subjected to drop impact. This means that the products would experience a significant amount of out-of-plane deformation along the PCB, which may cause stresses eventually resulting in solder joint failures. The attached shield-can could provide additional mechanical strength and minimize the out-of-plane deformation, especially where the electronic package is located. In this study, both the dynamic responses of the PCB and the characteristic life of solder joints with different shield-can designs were investigated, which are seldom explored by other researchers. Read more