Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
1998-11-10
2001-02-27
Font, Frank G. (Department: 2877)
Coherent light generators
Particular active media
Semiconductor
C372S036000
Reexamination Certificate
active
06195376
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to semiconductor laser stacks and more particularly to a packaging arrangement for such stacks which permit the use of high temperature solder and the testing of entire assemblages rather than individual components prior to assembly.
BACKGROUND OF THE INVENTION
It is well known in the art to position laser diodes into slots formed in the surface of a ceramic substrate. One such arrangement is disclosed in U.S. Pat. Ser. No. 5,040,187 issued Aug. 13, 1991. Another such arrangement is disclosed in the above-noted U.S. Patent application.
The current state of the art in the implementation of either of the above-noted arrangements requires relatively low temperatures solder bonds to be made to secure laser diodes in the slots. Accordingly, increasingly lower temperature solders thereafter are used in the fabrication of laser packages in order to avoid deterioration of previously made bonds. Since device reliability is reduced as lower and lower temperature solders are used as they require the use of flux, solder specification considerations are important in device design and processing and high temperature solders that do not require flux are preferred.
BRIEF SUMMARY OF THE INVENTION
In accordance with the principles of this invention, a laser diode submount, generally in the shape of an elongated bar with a square cross section has an elongated mesa on one surface. The submount configuration permits an inexpensive assembly of a stack of diodes to be fabricated, one diode between each pair of submounts with the mesas forming a set of parallel ridges. The stack is formed into an integral unit by high temperature solder preforms between the diodes and the submounts. The diodes of the entire stack can be tested at a single time. The ridges are then inserted into a matching set of metallized parallel slots of an electrically-insulating substrate.
The volume of each slot and the volume of each ridge is important to insure maximum thermal conduction of heat generated during operation of the stack. The heat generated in operation moves towards a heat sink connected to the substrate and the cross sectional area for the heat transfer is increased by spreading solder between each submount and the associated slot during mounting and the difference between the volume of a ridge and the volume of a slot dictates the appropriate amount of solder to be used.
REFERENCES:
patent: 5040187 (1991-08-01), Karpinski
patent: 5128951 (1992-07-01), Karpinski
Patel Rushikesh M.
Wilson Stewart Wayne
Font Frank G.
Opto Power Corporation
Rodriguez Armando
Shapiro Herbert M.
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