U.S. patent application number 13/219836 was filed with the patent office on 2011-12-22 for molded beam for optoelectronic sensor chip substrate.
This patent application is currently assigned to TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS, INC.. Invention is credited to ROBERT S. STRICKLIN.
Application Number | 20110309531 13/219836 |
Document ID | / |
Family ID | 39761846 |
Filed Date | 2011-12-22 |
United States Patent
Application |
20110309531 |
Kind Code |
A1 |
STRICKLIN; ROBERT S. |
December 22, 2011 |
MOLDED BEAM FOR OPTOELECTRONIC SENSOR CHIP SUBSTRATE
Abstract
A substrate on which a plurality of epoxy over molded integrated
circuit dies are formed includes a beam formed on the substrate for
providing stiffness to the substrate. The beam includes structure
having a cross-sectional shape, for example, substantially in the
shape of a trapezoid, "T" or "L", and may be formed on the top or
bottom surface of the substrate.
Inventors: |
STRICKLIN; ROBERT S.;
(RICHARDSON, TX) |
Assignee: |
TEXAS ADVANCED OPTOELECTRONIC
SOLUTIONS, INC.
PLANO
TX
|
Family ID: |
39761846 |
Appl. No.: |
13/219836 |
Filed: |
August 29, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12032805 |
Feb 18, 2008 |
8013456 |
|
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13219836 |
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60891238 |
Feb 23, 2007 |
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Current U.S.
Class: |
257/790 ;
257/793; 257/E21.502; 257/E23.116; 438/127 |
Current CPC
Class: |
H01L 24/45 20130101;
H01L 2224/48091 20130101; H01L 2224/48091 20130101; H01L 2924/01079
20130101; H01L 2224/45144 20130101; H01L 2924/181 20130101; H01L
24/97 20130101; H01L 2224/48465 20130101; H01L 2924/01033 20130101;
H01L 2224/48465 20130101; H01L 2924/181 20130101; H01L 24/48
20130101; H01L 23/3121 20130101; H01L 2224/97 20130101; H01L 21/56
20130101; H01L 2924/14 20130101; H01L 2224/45144 20130101; H01L
2924/14 20130101; H01L 2224/97 20130101; H01L 2924/00015 20130101;
H01L 2924/00014 20130101; H01L 2924/00 20130101; H01L 2224/48091
20130101; H01L 2224/85 20130101; H01L 2924/00012 20130101; H01L
2924/00 20130101 |
Class at
Publication: |
257/790 ;
438/127; 257/793; 257/E23.116; 257/E21.502 |
International
Class: |
H01L 23/28 20060101
H01L023/28; H01L 21/56 20060101 H01L021/56 |
Claims
1. A substrate comprising: a substantially planar sheet having a
top surface and a bottom surface; a plurality of epoxy over molded
integrated circuit dies formed on the top surface of the sheet,
wherein the epoxy over molded integrated circuit dies are separated
from each other by a portion of the top surface defining an open
area of the sheet between each pair of the epoxy over molded
integrated circuit dies; and an epoxy formed beam molded on the
bottom surface of the sheet, wherein the epoxy formed beam is
formed only from the epoxy forming the epoxy over molded integrated
circuit dies.
2. The substrate of claim 1 wherein the epoxy formed beam has a
length and a width, wherein each of the epoxy over molded
integrated circuit dies has a length and a width, and wherein the
length of the epoxy formed beam is substantially parallel to the
length of the epoxy over molded integrated circuit dies.
3. The substrate of claim 1 wherein the epoxy formed beam has a
length and a width, wherein each of the epoxy over molded
integrated circuit dies has a length and a width, and wherein the
length of the epoxy formed beam is substantially identical to the
length of the epoxy over molded integrated circuit dies.
4. The substrate of claim 1 wherein the epoxy formed beam has a
length and a width, wherein each of the epoxy over molded
integrated circuit dies has a length and a width, and wherein the
length of the epoxy formed beam is greater than the length of the
epoxy over molded integrated circuit dies.
5. A process comprising: selecting a substantially planar sheet
having a top surface and a bottom surface; forming a plurality of
epoxy over molded integrated circuit dies on the top surface of the
sheet, wherein the forming separates the epoxy over molded
integrated circuit dies from each other by a portion of the top
surface defining an open area of the sheet between each pair of the
epoxy over molded integrated circuit dies; and molding an epoxy
formed beam on the bottom surface of the sheet, wherein the epoxy
formed beam is formed only from the epoxy forming the epoxy over
molded integrated circuit dies.
6. The process of claim 5 wherein the epoxy formed beam is not
formed simultaneously with the epoxy over molded integrated circuit
dies.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/032,805, filed on Feb. 18, 2008, and entitled MOLDED
BEAM FOR OPTOELECTRONIC SENSOR CHIP SUBSTRATE, issuing as U.S. Pat.
No. 8,013,456 on Sep. 6, 2011, which application claims benefit of
U.S. Provisional Application No. 60/891,238, filed on Feb. 23,
2007, and entitled MOLDED BEAM FOR OPTOELECTRONIC SENSOR, the
specifications of which are incorporated by reference herein.
TECHNICAL FIELD
[0002] The present invention relates to integrated circuits, and
more particularly to integrated circuit fabrication.
BACKGROUND
[0003] Integrated circuits such as, for example, optoelectronic
sensors, are typically manufactured as packages in multiple
quantities formed from "chips" fabricated on printed circuit
boards. These packages are constructed by forming integrated
circuit dies on a FR4 printed circuit board or
Bismaleimide-Thriazine (BT) substrates. The die is wire bonded
with, for example, gold wire and then over molded with epoxy to
protect the die and the wire bonds. The substrate is then cut into
small pieces using a sawing process to form individual integrated
circuit packages.
[0004] The over mold process utilizes a transfer molded epoxy
material. The epoxy material and the substrate on which the
integrated circuit dies are formed, have different thermal
coefficient of expansions. The combination of the epoxy material
and the substrate and the tooling design methods utilized, create
large stresses in the individual integrated circuit packages.
Stresses in the individual packages are caused by the difference in
thermal coefficient of expansion between the mold epoxy and the
substrate. The stresses cause the substrate to curl after over
molding. As a result of the curling, fixturing is necessary to
flatten the substrate prior to the sawing operation.
[0005] A need has thus arisen for a substrate and fabrication
process which provides additional strength for the substrate to
prevent undesired curling of the substrate prior to a sawing
operation.
SUMMARY
[0006] In accordance with the present invention, a substrate on
which a plurality of epoxy over molded integrated circuit dies are
formed includes a beam formed on the substrate for providing
stiffness to the substrate. The beam includes structure having a
cross-sectional shape, for example, substantially in the shape of a
trapezoid, "T" or "L", and may be formed on the top or bottom
surface of the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a more complete understanding of the present invention
and for further advantages thereof, reference is now made to the
following Description of the Preferred Embodiments taken in
conjunction with the accompanying Drawings:
[0008] FIG. 1 is a pictorial illustration showing a plurality of
dies on a substrate;
[0009] FIG. 2 is a pictorial illustration showing epoxy over molded
dies on a substrate;
[0010] FIG. 3 is a pictorial illustration showing use of the
present beam molded on the top surface of a substrate;
[0011] FIG. 4 is a pictorial illustration showing an individual
component severed from a substrate;
[0012] FIG. 5 is a pictorial illustration of an alternate
embodiment of the present beam;
[0013] FIG. 6 is a pictorial illustration of an alternate
embodiment of the present beam; and
[0014] FIG. 7 is a pictorial illustration of the present beam
formed on the bottom surface of a substrate.
DETAILED DESCRIPTION
[0015] Referring to the FIG. 1, a plurality of individual
integrated circuit dies 10 are shown fabricated on a substrate 12,
having a top surface 12a and a bottom surface 12b (FIG. 7).
Substrate 12 may comprise, for example, a FR4 or BT substrate. Dies
10 are wire bonded utilizing wires 14.
[0016] FIG. 2 illustrates dies 10 and wires 14 being over molded
with epoxy 18 to form integrated circuit packages 16. Epoxy 18 may
comprise for example, thermoset epoxy plastic molding compound
materials.
[0017] Referring now to FIG. 3, an embodiment of the present
stiffening beam 22 is illustrated. Beam 22 is formed having a
cross-sectional shape substantially in the form of the letter "L",
and is formed on top surface 12a of substrate 12 adjacent to
packages 16. Beam 22 is formed from the same epoxy 18 which over
molds dies 10 and wires 14. Beam 22 adds sufficient strength to
stabilize substrate 12 thereby preventing substrate 12 from curling
prior to the saw operation. Beam 22 is formed in the fabrication
process at about the same time as the over molding process of dies
10 takes place.
[0018] FIG. 4 illustrates a single package 20 after the sawing
operation which severs packages 16 from substrate 12. During the
sawing operation, beam 22 is discarded.
[0019] FIGS. 5 and 6 illustrate additional embodiments of the
present beam. FIG. 5 illustrates a beam 24 having a cross-sectional
shape substantially in the form of a trapezoid. FIG. 6 illustrates
a beam 25 formed having a cross-sectional shape substantially in
the form of the letter "T".
[0020] FIG. 7 illustrates the use of beam 22 formed on bottom
surface 12b of a substrate 12.
[0021] Other alterations and modifications of the invention will
likewise become apparent to those of ordinary skill in the art upon
reading the present disclosure, and it is intended that the scope
of the invention disclosed herein be limited only by the broadest
interpretation of the appended claims to which the inventors are
legally entitled.
* * * * *