MOLDED BEAM FOR OPTOELECTRONIC SENSOR CHIP SUBSTRATE
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.
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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 FIELDThe present invention relates to integrated circuits, and more particularly to integrated circuit fabrication.
BACKGROUNDIntegrated 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.
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.
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.
SUMMARYIn 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.
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:
Referring to the
Referring now to
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.
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.
Type: Application
Filed: Aug 29, 2011
Publication Date: Dec 22, 2011
Applicant: TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS, INC. (PLANO, TX)
Inventor: ROBERT S. STRICKLIN (RICHARDSON, TX)
Application Number: 13/219,836
International Classification: H01L 23/28 (20060101); H01L 21/56 (20060101);