UNDERFILL SELECTION TO IMPROVE SOLDER JOINT RELIABILITY FOR DOWN HOLE DRILLING APPLICATIONS
McCluskey, Patrick Prof
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Underfill materials were originally developed to improve the solder joint reliability of the BGA packages under the thermal cycling when they are experiencing stresses due to the CTE mismatches between the board and the component. Although it is stated that the underfills will improve the shock reliability of the solder joints under the harsh environment for automobiles and military applications (-40 to 125oC). It has been found in the thermal cycling conditions the underfills will reduce the life of the solder balls. All the studies that had been performed were mostly below 150oC. There are no certain guidelines for selecting the underfills with the properties of the materials. The main aim of this research is to create a guideline for selecting the underfills for high temperature applications (above 150oC) for different BGA packages. In the first section initial characterization and benchmarking of the underfills that are available in the industry was performed. In the second section, all the selected underfills were subjected to a harsh environment to find the failure modes and mechanisms. With the help of experimentation and FEA that was done, guidelines were created for selecting the underfills for different BGA packages. This will be helpful to oil & gas and military applications.