Browse Prior Art Database

Automatic Alignment for Diode Laser Packages

IP.com Disclosure Number: IPCOM000103628D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 3 page(s) / 131K

Publishing Venue

IBM

Related People

Cina, MF: AUTHOR [+4]

Abstract

Disclosed is a flip-chip package for opto-electronic (OE) device chips, e.g., solid-state lasers, where the alignment of the optic axes of the device and package is achieved automatically during chip attach. Key features include microstructures (standoffs, stops and notches) which provide locating surfaces and edges, and solder wettable pads on the device chip and package. The solder pads are positioned in a manner such that during chip attach (melting the solder) the surface tension of the molten solder draws the aligning surfaces of the microstructures into contact providing precision alignment between the optical axes of the laser and package.

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This is the abbreviated version, containing approximately 52% of the total text.

Automatic Alignment for Diode Laser Packages

       Disclosed is a flip-chip package for opto-electronic (OE)
device chips, e.g., solid-state lasers, where the alignment of the
optic axes of the device and package is achieved automatically during
chip attach.  Key features include microstructures (standoffs, stops
and notches) which provide locating surfaces and edges, and solder
wettable pads on the device chip and package.  The solder pads are
positioned in a manner such that during chip attach (melting the
solder) the surface tension of the molten solder draws the aligning
surfaces of the microstructures into contact providing precision
alignment between the optical axes of the laser and package.

      Aligning opto-electronic device chips to the structures which
transmit and guide the optical signal is the most challenging problem
in opto-electronic packaging.  The collapse and self-aligning
properties of flip-chip, solder bump packaging technology have long
been recognized and recently have been used to align the optic axes
of two passive optical devices [*].  Essential to the operability of
this concept is that the volumes of the solder bumps be precisely
controlled (<7 percent) which is not generally achieved in
manufacturing environments.  Extending the concept to laser packaging
is further complicated by the small number of connections required by
a laser device chip, 3-30, so that volume variations from pad to pad
cause significant tilts between the chip and package when joined.

      This invention recognizes the difficulty in controlling the
solder volumes in solder bump technology and hence utilizes
microstructures to set the gap between the chip and the package
substrate.  A schematic of the invention (Fig. 1) shows a package
substrate which has, in addition to thin film wiring and solder pads,
a thick film glass layer which is patterned into waveguides and
microstops.  The waveguides are used to communicate the signal
between the OE device chip and the fiber array connector.  The
microstops fit inside notches which have been etched into the laser
chip.  The depth of the notches is chosen so that when the chip rests
on the microstops, the laser beam is centered in the core layer of
the waveguide (Fig. 2).  T...