Solderjet bumping packaging technique optimization for the miniaturization of laser devices

P Ribes-Pleguezuelo,R Eberhardt,E Beckert,S Zhang,A Tünnermann,F Wyrowski,B Septriani

doi:10.1186/s41476-017-0063-7

Abstract

BackgroundLow-stress soldering techniques can guarantee a minimized input of thermal energy allowing for the design and later assembly of more robust and miniaturized optical devices. However, in order to build miniaturized optical devices, these small-induced stresses produced by soldering techniques have to be investigated to guarantee that the stress-induced birefringence effects do not alter the device optical properties and requirements.MethodsAn analytical method that relates the stress-induced birefringence of laser components with their corresponding lasing capabilities has been compared to the real induced-stress results created in components packaged using solderjet technology. The main goal was to optimize the optical component packaging by using this low induced-stress soldering technique. The optimization was carried out by assessing components miniaturization while still assuring high robustness of the bond strength without creating a beam depolarization ratio of more than 1%.ResultsThe outcome of the study showed the possibility of assembling laser optical components down to sizes of around 300 μm, creating a bond strength of 5 N and higher, and a depolarization ratio much lower than the proposed target of 1%.ConclusionsOur results in terms of induced stress agreed with the finite element method result, which would imply correct post-processing laser simulations. This suggested that the solderjet bumping technique could robustly join components down to the laser emission beam size without strongly affecting the optical properties.

Highlights

Low-stress soldering techniques can guarantee a minimized input of thermal energy allowing for the design and later assembly of more robust and miniaturized optical devices
We studied the propagation of laser beam emission through the soldered components, trying to discriminate the cases for which the induced stress created a beam depolarization ratio of more than 1%
A simulation method as described in [4] has been followed, and the components soldering results have been contrasted with polarimeter stress measurements in order to investigate the optimization and miniaturization of laser components packaged with the solderjet bumping technique

Summary

Methods

In order to optimize the devices by miniaturizing the components while still guaranteeing enough robustness, a study with different components sizes and soldering approaches has been carried out. For the cases in which the push test results differed from the theoretical expected strength (for example the 2 mm cube (4) bumps 300 μm and the 1 mm cube (2) bumps 760 μm), the cause could be deviations in the final bump covered area or even defects on component edges that lead to component rupture though the FS glass These results, in contrast with the beam depolarization ratio analysis, could help users to select the component size and bond strength needed to manufacture miniaturized laser devices to be used in harsh environmental applications. Comparing case: with increased stress (5 ×) by design the results might be similar to the measured 1 mm and 2 mm cubes

Conclusions

Background