Optoelectronics and Telecom Conference Proceedings


Authors: Hendra Hartono, C. R. Emerson, Ph.D.
Company: SUNY at Binghamton
Date Published: 11/14/2001   Conference: Optoelectronics and Telecom

Abstract: The technology for laser development has advanced rapidly within the last two decades. The robustness of a laser array attachment, due to the void formation within the solder joint, becomes an issue since it reduces the operating life of the laser array. Laser arrays produce significant amounts of heat during operation. A thermoelectric cooler or a water-cooled heatsink must be used to dissipate the heat that is generated by the laser array. Imperfection in the heat transfer from the laser array to the heatsink, due to voids, will cause hot spots within the solder joint. Consequently, reducing the operating life.

One of the findings from the study included the bubbling activity, which occurred at the packaging stage. It was observed that the usage of water-based flux caused the bubbling activity. In addition, the flux activation caused outgassing. Consequently, the bubbling activity resulted in void formation within the solder joint. A scrubbing method was utilized to reduce the void formation. However, voids still existed within the solder joint. Cross-sections of the laser array packages confirmed that the voids had formed in the solder joints.

In order to improve the process, a different approach to laser array packaging was undertaken. A capillary flow attachment process was developed to eliminate the void formation. The capillary flow method uses the capillary actions of melting solder to flow between the pre-heated laser array and heated substrate. Cross-section of the laser array packages, using the capillary flow attachment process, exhibited no void formation. Elimination of the voids is one step toward improving the robustness of the laser array packaging.

Key words: Die attachment, laser array attachment, laser array packaging.

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