Opto-electronic chip package

Details Opto-electronic chip package Opto-electronic chip package

2001-06-02

2004-03-09

Bruce, David V. (Department: 2874)

Optical waveguides

With disengagable mechanical connector

Optical fiber to a nonfiber optical device connector

C385S092000

Reexamination Certificate

active

06702480

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the packaging of opto-electronic chips, and more particularly to the packaging of an opto-electronic chip containing surface normal opto-electronic devices.
BACKGROUND OF THE INVENTION
In an opto-electronic chip package, an opto-electronic chip is attached to a second level electronics package (e.g., a circuit board, etc.). The opto-electronic chip consists of one or more opto-electronic devices (e.g., photodetectors, quantum well modulators, semiconductor lasers, etc.) that are typically mounted on a semiconductor chip. The opto-electronic package further includes an optical fiber sub-assembly that receives one or more optical fibers and fixes them in a specific angular and positional orientation for optical communication with the opto-electronic device(s).
Often, the opto-electronic devices on the opto-electronic chip are surface normal opto-electronic devices. Such devices emit or receive an optical signal along an optical axis that is perpendicular to the top (or bottom) surface of the device. One common example of a surface normal device is a vertical cavity surface emitting laser.
FIG. 1
depicts surface normal opto-electronic chip package
100
, which includes chassis
102
, circuit board
112
, opto-electronic chip
128
, optical fiber sub-assembly
134
and heat sink
138
, interconnected as shown.
Chassis
102
includes first portion
104
and second portion
106
that are perpendicular to one another. Circuit board
112
includes chip-receiving region
114
and motherboard-interfacing region
116
that are separated by flexible region
118
. Chip-receiving region
114
receives opto-electronic chip
128
and motherboard-interfacing region
116
includes electrical connections
122
to motherboard
132
. Opto-electronic chip
128
includes surface normal opto-electronic devices
130
and optical fiber sub-assembly
134
includes optical fibers
136
.
Optical axis
1
—
1
of optical fiber sub-assembly
134
(and optical fibers
136
) is substantially perpendicular to the emitting/receiving surface of the surface normal opto-electronic devices
130
on chip
128
. Also, it is desirable for axis
1
—
1
of optical fiber sub-assembly
132
to be substantially parallel to motherboard
132
(shown in phantom) upon which package
100
is mounted. (In
FIG. 1
, axis
1
—
1
is not parallel to motherboard
132
because, for clarity, chip receiving portion
114
of circuit board
112
is not depicted in its final position against first portion
104
of chassis
102
.)
To obtain these positional relationships, flexible circuit board
104
is advantageously used. Its use allows placing chip-receiving region
114
in perpendicular relation to motherboard-interfacing region
116
. This is accomplished by flexing flexible region
118
that is disposed between chip-receiving region
114
and motherboard-interfacing region
116
of circuit board
104
.
To maintain this perpendicular relationship, chip-receiving region
114
and motherboard-interfacing region
116
of flexible circuit board
104
are typically attached to rigid “L-shaped” chassis
102
. Usually, fasteners
140
(e.g., machine screws, etc.) are used to attach motherboard-interfacing region
116
to second portion
106
of chassis
102
. Fasteners
140
are received by threaded openings
120
(in motherboard-interfacing region
116
) and threaded openings
110
(in portion
106
of chassis
102
). Fasteners
142
are used to attach chip-receiving region
114
to first region
104
of chassis
102
. Fasteners
142
are received by threaded openings
124
(in chip-receiving region
114
) and threaded openings
108
(in portion
104
of chassis
102
).
Additionally, heat sink
138
must be attached to chip-receiving region
114
of circuit board
112
to withdraw heat that is generated by attached opto-electronic chip
128
. Fasteners
144
can be used for this purpose. Fasteners
144
are received by threaded openings
146
(in heat sink
110
) and threaded openings
126
(in chip-receiving region
114
).
As a consequence of attaching the circuit board
112
to chassis
102
, and heat sink
138
to the circuit board, chip-receiving region
114
has a disadvantageously high fastener count. A high fastener count can lead to low reliability and, further, requires area to be dedicated to the fasteners that could otherwise be used for electronic circuitry, etc.
Accordingly, there is a need for an improved opto-electronic chip package that avoids disadvantages of the prior art.
SUMMARY OF THE INVENTION
The aforedescribed need is met by a chip package in accordance with the present invention. A chip package in accordance with the illustrative embodiment of the invention comprises a rigid L-shaped chassis to which a flexible circuit board is attached. The flexible circuit board includes a chip-receiving region, which receives an opto-electronic chip having surface normal opto-electronic devices disposed thereon. The flexible circuit board also has a motherboard-interface region that provides electrical connection to a motherboard. A flexible region is disposed between the chip-receiving region and the motherboard-interfacing region. When in position against the chassis, the chip-receiving region and the motherboard-interfacing region are perpendicular to one another.
An optical fiber sub-assembly places a plurality of optical fibers in optical communication with the surface normal opto-electronic devices. An optical axis of the optical fiber sub-assembly is perpendicular to an emitting/receiving surface of the surface normal opto-electronic devices. The optical axis of the optical fiber sub-assembly is parallel to the motherboard-interface region of the circuit board.
The chip package further includes a housing that receives the chassis, the circuit board and the optical fiber sub-assembly. Before placing the chassis, circuit board and optical fiber sub-assembly in the housing, the motherboard-interfacing region of the circuit is attached to the chassis. By virtue of the flexible region of the circuit board, as the chassis and circuit board are placed in the housing, the chip-receiving region of the circuit board is forced against the chassis. The chip-receiving portion is advantageously maintained in this position without the use of machine screws, etc.
The housing has an opening to allow a heat sink to be attached to the chip-receiving region of the circuit board to remove heat that is generated by the opto-electronic chip. The same fasteners (e.g., screws, etc.) that are used to attach the heat sink to the circuit board also advantageously attach the circuit board to the chassis, minimizing screw count in the circuit board.


REFERENCES:
patent: 5625734 (1997-04-01), Thomas et al.
patent: 6318909 (2001-11-01), Giboney et al.
patent: 6390690 (2002-05-01), Meis et al.

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