Radiant energy – Photocells; circuits and apparatus – Combined with diverse-type device
Reexamination Certificate
1999-03-01
2003-06-24
Evans, F. L. (Department: 2877)
Radiant energy
Photocells; circuits and apparatus
Combined with diverse-type device
C356S400000
Reexamination Certificate
active
06583402
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a structure for interconnection between semiconductor chips, between MCMs (multichip modules) or between an MCM and a semiconductor chip packaged on a printed board, or more in particular to a structure for mounting a semiconductor or an MCM accurately at a predetermined position on the board in order to obtain a superior optical coupling between the parts and an optical waveguide for optical communication between the parts on the printed board.
2. Description of the Related Art
With an increase in signal transmission speed and an increased density of wirings and parts, the technique of electrically interconnecting parts on a printed board has posed the problem that an increased wiring resistance, due to the skin effect, appears and that crosstalk between wiring is caused during communication between the parts. The increased wiring resistance leads to an increased heat generation and the crosstalk disturbs the signal waveform causing a malfunction. In this way, electrical methods of interconnection have almost come to a limit of speed and density.
A method for solving the problem mentioned above is to secure an optical connection in which the parts packaged on a printed board communicate with each other using an optical signal.
FIG. 18
shows a structure for optical communication between the parts packaged on a printed board.
In
FIG. 18
a
,
101
designates a printed board,
102
waveguides,
103
and
104
IC packages,
105
electrical circuit chips,
106
optical device arrays,
108
leads and
109
ball bumps.
The IC packages
103
and
104
each have built therein the electrical circuit chip
105
and the optical device array which is an assembly of light-emitting elements and photo-detectors. This packages is also called an OEIC package in view of the fact that electrical circuits and optical devices are integrated. Also, the optical device array
106
is electrically connected with the electrical circuit chips through the ball bumps
109
. The printed board
101
has buried therein a plurality of the waveguides
102
corresponding to the elements of the optical device array for transmitting an optical signal exchanged between the parts arranged on the printed board. The leads
108
receive power from a power supply unit not shown and supply it to the electrical circuit chips
105
and the optical devices
106
in the IC packages.
FIG. 18
b
is a bottom view of the IC packages
103
and
104
. In
FIG. 18
b
,
112
designates radiation holes of the light-emitting elements of the optical device array or incidence holes of the photo-detectors.
The diameter of a radiation hole
112
and an incidence hole
112
is about 20 &mgr;m and the holes are arranged at intervals of about 100&mgr;.
FIG. 18
c
is a top plan view of the printed board
101
. In
FIG. 18
c
,
121
designates pads and
122
openings of waveguides.
The pads
121
are supplied with power from a power supply unit not shown and connected width a power terminal or a GND terminal
108
. The openings
122
of the waveguides are placed in opposed relation to the radiation holes or the incidence holes
112
. The diameter of each opening
122
is about 50 &mgr;m to 90 &mgr;m, and the openings are arranged at intervals of about 100 micrometers.
With reference to
FIGS. 18
a
to
18
c
, the optical communication between the IC package
103
and the IC package
104
will be explained. In this case, an optical signal is assumed to be sent from the IC package
103
to the IC package
104
.
The IC packages
103
and
104
are supplied with power from a power supply unit not shown through the pads
121
and the leads
108
.
The electrical circuit chip
105
of the package
103
outputs a signal (electrical signal) to the electrical circuit chip
105
of the package
103
. The signal output from the electrical circuit chip
105
is converted into an optical signal in the light-emitting elements of the optical device array
106
, and radiated toward the openings
122
of the waveguide from the radiation holes
112
. The optical signal passes into the waveguides
102
from the openings
122
, proceeds in the waveguides
102
and is output toward the incidence holes
112
of the IC package
104
from the openings
122
of the IC package
104
. The optical signal received by the IC package
104
is converted into an electrical signal by the photo-detectors.in the optical device array
106
and output to the electrical circuit chip
105
.
The use of the above-mentioned technique of interconnection permits exchange of an optical signal between parts and eliminates the need of electrical connection, obviates the problems of increased wiring resistance and crosstalk, and thus can increase the signal transmission speed and the density of parts and wiring.
As shown in
FIGS. 18
b
and
18
c
, however, the openings
122
and the radiation and incidence holes
112
of the waveguides are so small that the registration between the waveguides and the optical devices requires a highly accurate optical coupling technique. The registration error must be controlled to not more than 10 &mgr;m. Also, the LD (laser diode) used as the light-emitting element and the PD (photo-diode) used as the photo-detector have a low heat resistance, and are liable to be broken by a thermal stress when soldered for packaging.
SUMMARY OF THE INVENTION
The object of the present invention is intended, taking the above-mentioned problem into consideration, to provide a highly accurate technique for optical coupling between parts and a packaging technique exerting only a small stress on the optical devices in such an optical coupling.
In order to solve the above-mentioned problem, according to the invention, a socket for receiving a semiconductor part including photoelectric elements is arranged on a printed board. According to a first aspect of the present invention, the position of packaging a semiconductor part on the printed board is defined, and therefore the accuracy of registry between the optical transmission path on the printed board and the optical device of the semiconductor part is improved.
Preferably, the socket includes a power terminal for supplying a source voltage to the photoelectric elements of the semiconductor part. Preferably, the change in the terminal shape of the part can be met simply by redesigning the socket, and therefore the multipurpose applicability of the printed board is maintained.
Preferably, the semiconductor part inserted into the socket and the insertion holes of the socket for the semiconductor part are placed in spaced relation to each other. As a result, the correct position of arrangement of the semiconductor part is held within a predefined range, resulting in an improved working efficiency.
Preferably, the semiconductor part packaged on the printed board includes light-emitting elements for transmitting an optical signal and photo-detectors for receiving the optical signal emitted by the light-emitting elements. The semiconductor part emits an optical signal, and receives the optical signal by itself through the optical device arranged on the printed board. The degree of optical coupling between the printed board and the semiconductor part can be determined.
Preferably, the optical device arranged on the printed board is specified as an optical transmission path. Unless both the light-emitting elements and the photo-detectors of the semiconductor part are optically coupled to the openings of the optical transmission path, the semiconductor elements cannot receive the optical signal emitted by themselves. In other words, the structure is such that the registration between two points of a semiconductor part and two points of the printed board can be achieved at the same time by receiving the optical signal.
Preferably, an optical device for optical communication with the photoelectric elements arranged on the printed board is included in the semiconductor part packaged on the printed board. The right packaging position of the semiconduct
Evans F. L.
Fujitsu Limited
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