Optical-electronic array module and method therefore

Details Optical-electronic array module and method therefore Optical-electronic array module and method therefore

2001-08-09

2003-10-21

Zarroli, Michael C. (Department: 2839)

Optical waveguides

With disengagable mechanical connector

Optical fiber to a nonfiber optical device connector

C385S089000, C385S092000

Reexamination Certificate

active

06634802

ABSTRACT:

BACKGROUND
1. Field of the Invention
This invention relates to an optical-electronic array module for connecting to a fiber optic cable and to electronic devices on an electronic circuit board, and more particularly to an arrangement of the module that facilitates assembly of the module and alignment and connection of the module to the fiber optic cable electronic circuit board.
2. Related Art
Optical-electronic transmitters and receivers on an optical-electronics module are conventionally coupled to optical signals via a fiber-optic cable. The optical fibers of the cable are typically aligned to optics of the optical-electronic transmitters and receivers with a required precision of about 5 microns.
It is also conventional practice that the optical-electronics module with the transmitters and receivers are supplied to a customer having electrical circuit on the customer's circuit board to be connected to the optical-electronic transmitters and receivers. Generally the plane of the optical paths in the optical coupler is parallel to the plane of the customer's electronic circuitry, and the plane of the electronic inputs and outputs (“I/O”) of the optical receivers and transmitters is orthogonal to the plane of the I/O of the customers electronic circuitry. Therefore, in order to connect the I/O of the electronic circuitry on the customer's board to the electrical I/O of the optical-electronic transmitters and receivers it is necessary to turn the electrical path between the respective sets of I/O.
Referring to
FIG. 1
, the alignment of optical paths and the turning of the electrical path between I/O sets is illustrated in a prior art module
100
, which includes a carrier
110
mounted on a heat sink
180
, an optical-electronic die
120
mounted on the carrier
110
, a coupler
140
, a signal conditioning die
190
, a flexible cable
130
, a first circuit board
170
, and C4 solder balls
175
. The circuit board
170
has die
190
mounted thereon. The die
190
has signal conditioning circuitry that interconnects to and operates with the optical-electronic circuitry of the die
120
by means of the flexible cable
130
. The die
190
also interconnects to a customer's circuit board, second circuit board
172
, via conductors (not shown) and C4 solder balls
175
.
The carrier
110
is for structural purposes and for conducting thermal energy away from the die
120
. The carrier
110
does not have embedded conductors, but the carrier
110
itself is conductive, and it electrically connects a cathode on the laser die
120
to ground. The prior art apparatus uses two carriers, side-by-side. Only one of the carriers
110
is shown in FIG.
1
. On one of the carriers
110
, the die
120
is a laser die. On the other carrier
110
, the die
120
is a photo detector die. (The term “optical-electronic die” will be used herein to refer to either a laser die or a photo detector die.) In
FIG. 1
, the die
120
is bonded to the carrier
110
, such as with a die attach epoxy, on the same side of the carrier
110
as an optical coupler
140
. The carrier
110
has alignment holes for receiving pins
142
from the coupler
140
. The coupler
140
attaches to the carrier
110
with a retainer (not shown) and alignment pins
142
.
A fiber-optic cable
160
having a number of embedded fibers
162
mates to the optical coupler
140
. A connector
150
of the fiber-optic cable
160
has alignment holes for receiving alignment pins
152
from the coupler
140
. The coupler
140
attaches to the connector
150
with a retainer (not shown) and alignment pins
152
.
The flexible cable
130
is a composition of gold-coated, copper conductors etched in a polyimid and covered with an insulating jacket. The flexible cable
130
is attached at attachment
137
to the first circuit board
170
at one end and at attachment
134
to carrier
110
for the optical-electronic die
120
at the other end. The flex cable
130
is electrically connected at
132
to the die
120
by wire bonds
136
. Likewise, the flex cable
130
is electrically connected at
139
to die
190
with wire bonds
138
.
The flex cable
130
provides a 90 degree turn between the I/O plane of the optical-electronic die
120
and the customer's board, second circuit board
172
, however, it is problematic to use the flex cable to provide this 90 degree bend because of its cost and because of the relatively large number of interconnections at
132
,
134
,
137
, etc. Also, with conventional arrangements such as that of
FIG. 1
it is problematic to achieve required alignment precision since it requires expensive and time consuming “active” alignment, according to which the optical-electronic die is powered and its output monitored, then secured with adhesive once alignment is optimized. There is therefore a need for an improved optical-electronics module.
SUMMARY OF THE INVENTION
The foregoing need is addressed in an optical-electronic module having a submount. The submount forms an aperture which extends all the way through the submount. An optical-electronic die is mounted on a first side of the submount. The module also has an optical coupler, with a fiber-optic path in the coupler, for coupling optical signals from or to a fiber-optic cable on a first end of the coupler and for coupling the optical signals from or to the die at a second end of the coupler. The second end of the coupler has a feature matching the submount aperture and inserted into the submount aperture. An optical input or output of the die faces the second end of the coupler and is aligned to the coupler fiber-optic path and optically coupled to the fiber-optic path through the aperture.
In another aspect, pads for electronic inputs or outputs on the optical-electronic die face, align with, and are electrically coupled to first electrical pads on the submount first side.
In another aspect, the aperture is tapered, narrowing toward the submount first side, and the coupler feature matching the submount aperture comprises a tapered nose narrowing toward the coupler second end.
In another aspect, the coupler end proximate to the die (the coupler second end) is sub-flush to the submount first side. From the coupler side which is proximate the die, the coupler extends through the submount aperture and beyond the submount second side.
In still another aspect, the submount first side is in a first plane, and the submount has a third side in a plane oblique or perpendicular to the first plane. The third side has second electrical pads, for connecting to electrical pads on a circuit board. The second electrical pads are connected by conductors of the submount to respective ones of the first electrical pads, so that electrical paths from the electronic inputs or outputs of the optical-electronic die turn by at least an acute angle from the first to the second submount electrical pads.
In a still further aspect, the coupler has mechanical pads for coupling to the circuit board. In an alternative, the coupler mechanical pads are on a bottom side of the coupler and the coupler bottom side is in the same plane as the submount third side.
In a method form of the invention, a method for fabricating an optical-electronic array module includes a providing a submount having first and second opposing sides and a third side essentially perpendicular to the first submount side. The first and third submount sides have an adjoining edge, and the submount forms an aperture extending through the submount from the first to the second sides. Conductive traces are formed on the first and third sides and adjoining edge of the submount using a shadow mask. The traces interconnect electrically conductive pads on the first submount side and second electrically conductive pads on the submount third side. An optical coupler is inserted into the submount aperture and secured therein. The coupler has a fiber-optic path therein for coupling optical signals from or to a fiber-optic cable on a first end of the coupler and for coupling, at a second end of the coupler, the optica

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