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About

Micro Joining
Published:
Micro Joining
The Centre for Advanced Materials Joining, University of Waterloo
During my undergrad years at the University of Waterloo, I have worked and collaborated with the Centre for Advanced Materials Joining (CAMJ) in several occasions which resulted in publication of an academic journal, a conference presentation and a project course credit.

I did a co-op term at CAMJ as a research assistant. I investigated the mechanics of thermosonic flip chip bonding process with Au balls by means of finite element analysis. An experimental set up was previously developed to emulate the last step in the bonding process. I developed a finite element model for this experimental set up and calibrated by sensitivity analysis and the experiment results. I performed more than 70 different sensitivity analysis. The result of my work was published as an academic manuscript by Journal of Electronic Packaging, ASME: ” Finite Element Modeling of Simultaneous Ultrasonic Bumping With AuBalls” (Dec 2009, V.131,  I.4, 041007).

The numerical analysis were performed in COMSOL and MATLAB.
Mesh visualization of the Au bump, pad and substrate.
I worked with the CAMJ as an undergraduate research assistant (URA) during a school term. My research project was to determine proper property, boundary conditions and physics settings to model and simulate the contacts between the ball & pad and ball & capillary in an ultrasonic ball bonding process. I developed a simple model to solve the nonlinear problem and determine the correct settings for modeling the contact.

Based on the result of my URA work, I initiated a research project to develop a finite element model to simulate a ball bonding process. For this project I was awarded a course credit with the highest grade of 99%.

Thesemiconductor and electronic packaging industry introduces new chip and packagedesigns with a fast pace. One of the main challenges with these new designs(chip/IC) is their behavior during the wire bonding process. One of the mainconcerns is the mechanical damage of the underpad layers while achieving astrong bond. Currently, experimental means are the primary characterizationmethod to validate any new designs. However, the process which involvesfabricating a new design and testing it is too expensive and time consuming.


Oneapproach to address this problem is using finite element (FE) means tocharacterize an optimum bonding process for different types of chips. Such acharacterization would help to modify the chips’ structure to achieve goodmechanical integrity. Although the bonding mechanism has not been perfectlyunderstood and solved yet but some of its physical mechanisms can be describedby FE models. Some work has been done in this field; however, there is still a lot more to be done.

My research involved the effects of interfacial gap on the mechanics of thermosonic ball bonding. I used ABAQUS for my research.
Half model of the capillary, the ball and the chip.
My final contribution to  CAMJ was a conference presentation for the International Symposium on Materials Science and Innovation forSustainable Society, Osaka, Japan: "Technological and Ecological Aspects ofReplacing Gold with Copper for Microelectronic Wire Bonding" (Nov 2011, EFP I)

As a co-author I contributed to the presentation by investigating the ecological aspects of replacing gold with copper for microelectronics wire bonding.