Raj Bhatti

Fatigue life of lead-free solder thermal interface materials at varying bond line thickness in microelectronics

Microelectronics failure during operation is commonly attributed to ineffective heat management within the system. Hence, reliability of such devices becomes a challenge area. The use of lead-free solders as thermal interface materials to improve the heat conduction between a chip level device and a heat sink is becoming popular due to their promising thermal and mechanical material properties. Finite element modelling was employed in the analysis of the fatigue life of three lead-free solders (SAC105, SAC305, and SAC405) under commercial thermal cycling load (between −40 °C and 85 °C). This paper presents the results of the simulation work focusing on the effect of varying the solder thermal interface thickness (or bond line thickness) on the reliability of the microelectronic device. The results obtained were based on stress, strain, deformation, and plastic work density. The results showed that the fatigue life of the three solders increases as the solder thermal interface thickness increases. Also, the stresses, strains, and deformation were highest around the edges and vertices of the solder interface. In addition, the optimal solder material of choice based on the criteria of this research is given as SAC405. It has higher operational life span and good reliability capabilities.

A Modular Product Structure Based Methodology for Seamless Information Flow in PLM System Implementation

ABSTRACTProduct development process deals with large amount of information generated from market survey, concept design, manufacture, test, limited production, production, service, and obsoleting. The information should be stored systematically so that it is easily traceable and reusable for future product development. This paper presents a methodology for seamless product information flow between the three main enterprise information systems such as Computer Aided Design and Manufacturing (CAD/CAM), Product Data/Lifecycle Management (PDM/PLM) and Enterprise Resource Planning (ERP) used in the process of innovative product development while implementing PLM. PLM implementation deals with various existing product data and information generated over years both from CAD and ERP systems. Data integration is very challenging in multi-national engineering companies and has important impact on future decisions while creating new processes. The aim is to define a modular product structure that can be used to conn...

The effect of thermal constriction on heat management in a microelectronic application

Thermal contact constriction between a chip and a heat sink assembly of a microelectronic application is investigated in order to access the thermal performance. The finite element model (FEM) of the electronic device developed using ANSYS software was analysed while the micro-contact and micro-gap thermal resistances were numerically analysed by the use of MATLAB. In addition, the effects of four major factors (contact pressure, micro-hardness, root-mean-squared (RMS) surface roughness, and mean absolute surface slope) on thermal contact resistance were investigated. Two lead-free solders (SAC305 and SAC405) were used as thermal interface materials in this study to bridge the interface created between a chip and a heat sink. The results from this research showed that an increase in three of the factors reduces thermal contact resistance while the reverse is the case for RMS surface roughness. In addition, the use of SAC305 and SAC405 resulted in a temperature drop across the microelectronic device. These results might aid engineers to produce products with less RMS surface roughness thereby improving thermal efficiency of the microelectronic application.

Effect of component standoff height on thermo-mechanical reliability of ball grid array (BGA) solder joints operating in high-temperature ambient

Effect of standoff height (SH) on thermo-mechanical reliability of solder joints in miniaturised surface mount components in consumer electronics which operates in high-temperature ambient is studied. This work investigates the effect of CSH on ball grid array (BGA) solder joints which operates in high homologous temperature in mission critical systems and seeks to utilise the findings of this investigation to minimise the accumulated strain energy density in the joints. The study focuses to underpin the relationship between CSH and shear strength of the joints while it determines the effect of long high-temperature operations on integrity of the soldered joints. It identifies the failure site and mode in the joints and examines failed surfaces to provide information on the morphology of the material microstructure. The results demonstrate that increase in CSH decreases the shear strength of the solder joints and at prolonged operations in high-temperature of about 150 degrees centigrade, solder joint shear strength decreases due to significant formation and growth of brittle intermetallic compound at the interface between substrate pad and solder bulk. EDS analysis shows that this region is characterized by high Tin/Cu content and demonstrates failure mode of crack initiation, propagation and pad lifting.