Assignment#2: Writing an introduction

The Development of Epoxy Adhesive whose Properties are Suitable
for Head Gimbal Assembly Process

by

Tossapol Boonlert-uthai

Stage 1: The head gimbals assembly process (HGA) operates in a hard disk drive manufacturing plant. HGA is made by assembling slider (read-write head) on a suspension with adhesive in which it is an important part in a hard disk drive. According to the Head Gimbal Assembly Process in Western Digital (Bang Pa-in) Co., Ltd. (2012), there are two assembly lines. In the first assembly line, semi automation, is divided into two steps, which are dispensing glue from a syringe on a suspension in the area that will be adhered to the slider via an auto adhesive dispensing (ATD) machine. After that, the slider is then put down on the glue-dispensed area of a suspension and radiated ultraviolet (UV) light to cure an adhesive for setting via an optical system corporation (OSC)-automation slider bond. In this stage, an adhesive is partially cured to be able to hold a slider. On the second assembly line, automation one, auto core adhesion machine (ACAM) proceeds all steps in one machine. After that, the part is put in an IR oven to enable an adhesive to be completely solidified and dried. Finally, HGA is sent to the further stages such as quality control, cleaning and packing process.

Stage 2: The adhesive used for HGA process is an epoxy type. The component of epoxy adhesive depends on HGA process, UV curing and thermal curing. Therefore there are epoxy monomer, photoinitiator (for UV curing) and curing agent (for thermal curing) which are the main composition. Decker (1996) proposed the mechanism of UV curing in which a photoinitiator absorbs UV-radiation to cleave the radical or reactive species, such as free radicals and protonic acid that initiate cross-linking polymerization with a monomer according to a radical and cationic mechanism, respectively, and then obtains the polymer network. For the thermal curing reaction, epoxy or oxirane group reacts with amine group of curing agent is called polyaddition reaction (Petri, 2006, p.64). Furthermore, Golaz et al. (2013) reported that ambient temperature can influence rate of polymerization. When operating temperature increases, the adhesive’s viscosity decreases in which it can accelerate the rate of polymerization due to higher mobility of adhesive molecules.

Stage 3: There are several problems relating to process, for example, instability of adhesive’s viscosity, air bubbles in adhesive and degree of cure, have been encountered. Causes of the problems of epoxy adhesive have not been thoroughly studied. Data were collected from production line and inquiring the problems from authorities and engineers. After that, the problems are analyzed and some hypotheses are considered.

Stage 4&5: Therefore, this research aims to characterize the epoxy adhesive used in HGA process in terms of thermal, rheological and chemical properties of uncured and cured adhesive. After that the characteristics of epoxy adhesive are applied with the HGA process to use epoxy adhesive properly and efficiently. Afterwards, formulating epoxy adhesive whose properties are suitable for head gimbals assembly process than current adhesive will be performed.