Parameters Analysis for Low Power Q-Switched Laser Cutting in Singulation Process of HDD Manufacturing The 4th AIT Masters Theses Competition Present By Sujin Wanchat Industrial Systems Engineering Asian Institute of Technology May 18, 2009 The 4th AIT Masters Theses Competition Present By Sujin Wanchat Industrial Systems Engineering Asian Institute of Technology May 18, 2009

- Introduction - Statements of Problem - Objective - Methodology - Results - Conclusions - Introduction - Statements of Problem - Objective - Methodology - Results - Conclusions OUTLINE

INTRODUCTION Hard Disk Drive (HDD) = A main digital data-storage in a computer. A HDD suspension = A part of HDD that carries the read-write head flies over the disk media.

INTRODUCTION Manufacturing process of HDD suspension Etching stainless steel Component forming Assembly all components Functional forming Cutting (singulation)

INTRODUCTION The suspension bridge and the cutting line

INTRODUCTION Laser cutting Die cutting

INTRODUCTION Laser cutting has more advantage in reducing clinging particles on cut-finished surface. Laser cutting can not avoid the thermal effect which may cause malfunction of HDD suspension. Thus, the surface roughness (Ra) and heat affected zone (HAZ) must be reduced as much as possible.

STATEMENTS OF PROBLEM - According to die cutting process, the number of waste products still appears. - The tool wearing can be found in die cutting, but does not exist in laser. - The laser cutting shows the evidence of better cut- finished surface than conventional die cutting technique. - According to die cutting process, the number of waste products still appears. - The tool wearing can be found in die cutting, but does not exist in laser. - The laser cutting shows the evidence of better cut- finished surface than conventional die cutting technique.

QualityLaser Punch (die) PlasmaNibbling Abrasive fluid jet Wire electric discharge machining (EDM) Numerical control milling SawingUltrasonic Oxy flame Rate  Edge quality    Kerf width   Scrap and swarf   Distortion   Noise  Metal + non- metal  Complex shapes  Part nesting  Multiple layers  Equipment cost  Operating cost  High volume  Flexibility   Tool wear    Automation    Heat affected zone   Clamping   Blind cuts  Weldable edge   Tool changes  = Advantage  = Disadvantage STATEMENTS OF PROBLEM

OBJECTIVE To investigate the influent parameters which affect the surface roughness of cutting plane and the HAZ length based on Nd:YAG pulsed laser

Nd:YAG   Metal Wavelength = 1.06  m CO 2   Non-metal Wavelength = 10.6  m Laser Types CW  - Cannot modify “power profile” Pulsed  - Reduce interacting time - Raise peak power Laser Modes METHODOLOGY

DOE is analyzed based on the experimental data using “2 4 factorial designs with addition of center points” technique. Controllable factors Low level (-) Medium level (0) High level (+) Beam focal spot size,  (  m) Pulse frequency, f (Hz) 50    10 3 Cutting speed, v (  m/s) 1,0001,1501,300 Laser power, P (Amp) Controlled factors: 1. The same work piece’s model 2. Pulse width, T d = 2  s 3. Room temperature = 28  C 4. Each specimen has thickness of 25  m, and the bridge’s width of 2 mm.

METHODOLOGY Conduct the real experimental data from the total 20 cases.

METHODOLOGY Workpiece after cutting 2. Surface Profile 3. Ra value reported 1. Workpiece after cutting 2. Surface Profile 3. Ra value reported

1st 2nd 3rd A = Beam focal spot size (  m) B = Pulse frequency (Hz) C = Cutting speed (  m/s) D = Laser power (Amp) RESULTS Ra

1st 2nd 3rd 4th 5th RESULTS HAZ A = Beam focal spot size (  m) B = Pulse frequency (Hz) C = Cutting speed (  m/s) D = Laser power (Amp)

ABD (+) Low A, B, and D consequently Low Ra CD (+) Low C and D consequently Low HAZ Significant Factor for Ra Significant Factor for HAZ CONCLUSIONS A = Beam focal spot size (  m) B = Pulse frequency (Hz) C = Cutting speed (  m/s) D = Laser power (Amp)

CONCLUSIONS Ideal pulsed laser for cutting process must have: short wave length, very short T d, very high f, high P p, small  and fast cutting speed.