A Problem of Particulate Contamination in an Automated Assembly Machine Successfully Solved by CFD and Simple Experiments

Jatuporn Thongsri

doi:10.1155/2017/6859852

Abstract

Assembly of hard disk drives (HDDs) needs to be done in an automated assembly machine (AAM) virtually free of particulate contamination that can cause them to malfunction. Fan filter units (FFUs) are installed above the AAM to reduce the number of suspended particles in the recirculating air flowing over and around them. At one time, several HDDs were found to be defective. To find out the root cause of this problem, computational fluid dynamics (CFD) was used to investigate the airflow over and around the AAM. It was found that the cause of the high particle counts was improper air speed from the FFUs. The optimal FFUs air speed needed to be in the range of 0.35–0.65 m/s in which the airflow would block out nearby airborne particles and purge away particles generated by the AAM effectively which would, in effect, reduce the particle counts down below the threshold level of class 100 clean room. A few available measurement tools at the factory were then used to perform validating measurements against the simulation results, and the validation was positive. This optimal speed range was implemented at the factory after which the level of contamination was reduced to an acceptable level.

Highlights

Thailand is a big producer of various electronics parts including hard disk drive (HDD)
Class 100 clean room is prohibitively costly to construct and very difficult to maintain; in real HDD production line, class 1,000 clean room equipped with fan filter units (FFUs) is employed instead
To reduce particle counts in the air above and around assembly machines (including automated assembly machine (AAM) that welds small electronic boards to the head gimbal assembly (HGA) of head stack assembly (HSA) in an HDD production line), FFUs blow away particles from them and recirculate clean air over them [2, 3]

Summary

Introduction

Thailand is a big producer of various electronics parts including hard disk drive (HDD). This study was a collaborative research between the author and a few engineers at an HDD factory for the purpose of seeking out a solution for a problem of excessive particle contamination in some HDDs fabricated by the AAM at one time. This research was intended as the practical solution This CFD investigation focused on the contamination problem of the AAM, finding the root cause of the particle contamination, validating the simulated results with the actual measurements at the factory, and seeking an effective solution to the problem. For our experiments, we purposely opted for the measurement tools that were readily available at the factory at that time so that the technicians there would be able to apply our experimental procedure and rapidly

Theoretical Background

Methodology

Optimum FFUs Air Speed