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RESEARCH PAPERS

# Transient Thermomechanical Simulation of Laser Hammering in Optoelectronic Package Manufacturing

[+] Author and Article Information
Ben Ting

Department of Mechanical Engineering, Tufts University, Medford, MA 02155

Vincent P. Manno

Department of Mechanical Engineering, Tufts University, Medford, MA 02155Vincent.Manno@tufts.edu

J. Electron. Packag 127(3), 299-305 (Nov 01, 2004) (7 pages) doi:10.1115/1.1938206 History: Received January 28, 2004; Revised November 01, 2004

## Abstract

Laser hammering (LH) is a process used in the manufacturing of butterfly optoelectronic packages to correct laser-to-fiber misalignment that occurs when the semiconductor lasers are welded in place. High-power, precisely positioned pulsed lasers are used in LH to induce deformation of the fiber support housing to, in turn, induce realignment. A thermomechanical modeling study of LH is reported in this paper, which focuses on the degree to which a steady-state model can predict the asymptotic state of a transient response subjected to a periodic laser excitation. A baseline, two-dimensional fiber mounting/ferrule geometry is employed in a finite element analysis simulation case study. Various laser wave forms are applied to focus spot location sizes of 50 and $200μm$ over a range of applied heat fluxes $(10–1000W∕mm2)$. Effects of laser energy deposition location, as well as the use of multiple lasers, are also studied. The results show that the steady-state solution is in good agreement with the asymptotic transient response for horizontal fiber displacement and fiber temperature. The laser focus spot surface temperature predictions are also found to be in reasonable agreement. However, the vertical fiber displacement tends to be overpredicted by the steady-state solution, sometimes by as much as an order of magnitude. The causes, both physical and computational, of this disagreement are discussed.

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## Figures

Figure 1

Schematic of laser diode and fiber/ferrule coupling within an optoelectronic package (idealized 2D cross section on the right)

Figure 2

Typical optical transfer efficiency curve (2)

Figure 3

Possible feedback control loop for post weld shift (PWS) realignment

Figure 4

Single laser beam, 50μm FSL baseline model geometry

Figure 5

Finite element mesh of the model (left) and fiber region (right)

Figure 6

Thermal and mechanical boundary condition schematic

Figure 7

Thermomechanical response during first pulse of single-laser, 200μm FSL case

Figure 8

Comparison of steady-state and transient model predictions of center fiber temperature for single-laser, 200μm FSL case

Figure 9

Comparison of SS and ATR of FSL temperature for single-laser, 200μm FSL case

Figure 10

Comparison of SS and ATR fiber position predictions for single-laser, 200μm FSL case

Figure 11

Thermal and displacement field predictions for dual-laser, high-power (375W∕mm2-avg, 1000W∕mm2-peak), 200μm FSL case (ATR results at the extreme conditions of the limit cycle)

Figure 12

Comparison of SS and ATR fiber position predictions for dual-laser, high-power (375W∕mm2-avg, 1000W∕mm2-peak), 200μm FSL case

Figure 13

ATR fiber position predictions for single-laser, 200μm FSL case using material properties evaluated at 298 and 600K

Figure 14

von Mises stress fields at 1.2s for single-laser, 200μm FSL case using material properties evaluated at 298 and 600K (peak stress contour–680MPa)

## Errata

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