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Molded stiffener for thin substratesRelated Patent Categories: Active Solid-state Devices (e.g., Transistors, Solid-state Diodes), EncapsulatedMolded stiffener for thin substrates description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060290011, Molded stiffener for thin substrates. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATION [0001] This application is a division of U.S. patent application Ser. No. 10/077,554, filed Feb. 15, 2002, currently pending. FIELD OF THE INVENTION [0002] The present invention relates generally to a stiffener for substrates used in semiconductor fabrication processes, and more particularly to a stiffener molded onto thin substrates, such as lead frames, used during the production of die assemblies and packages. BACKGROUND OF THE INVENTION [0003] A stiffener device has been used with lead frames for die assembly and package production to provide support for flexible, and even flimsy, substrates. The stiffener can assist in preventing or reducing damage to the substrate and associated electrical components. Stiffeners are typically attached to lead frames by applying a strip of adhesive tape or a layer of adhesive paste to the stiffener and/or the surface of the lead frame. [0004] Referring to FIG. 1, a prior art semiconductor die package 2 disposed within a package mold 4 is shown. Package 2 typically comprises a lead frame 6 (or other substrate), adhesive element 8, one or more dies 10, adhesive element 12, a metal or plastic stiffener 14, and an encapsulating material 16. Package mold 4 comprises mold plates 18. Mold plates 18, as illustrated in FIG. 1, define a mold gate 20 and a cavity 22 disposed within package mold 4. [0005] The package illustrated in FIG. 1 can be assembled by first constructing a die assembly 24. Die assembly 24 comprises one or more dies 10 secured to lead frame 6 with adhesive element 8. After die assembly 24 is assembled, plastic or metal stiffener 14 is secured to lead frame 6 of die assembly 24 with adhesive element 12, and the die assembly is placed between mold plates 18 within cavity 22. Encapsulating material 16 is then introduced into package mold 4, through mold gate 20, and flows over die assembly 24. In such instances, encapsulating material 16 is generally heated prior to being injected into package mold 4, and flowed in and around die assembly 24, covering all or a portion of lead frame 6 and/or dies 10. Thereafter, encapsulating material 16 is allowed to harden. Mold plates 18 can then be removed whereby package 2, as illustrated in FIG. 2, remains. [0006] In some situations, the stiffener comprises a metal or metal alloy. Unfortunately, metal stiffeners are difficult to cut with conventional, diamond-tipped saws. As such, metal stiffeners are burdensome to segment before and during package production. Likewise, the produced packages that incorporate metal stiffeners are also difficult to cut. As a result, it is laborious to separate packages from one another. Additionally, metal stiffeners are expensive and therefore contribute to added expense of the package. [0007] Plastic stiffeners have also been used to support a lead frame. Typically, in those cases where a plastic stiffener is used, a thermoplastic or thermosetting polymeric material is heated and introduced into a mold and, upon cooling, the mold is opened and a plastic stiffener is produced. Thereafter, the plastic stiffener is secured to the lead frame using an adhesive tape or paste. [0008] Plastic stiffeners offer several advantages over metal stiffeners. For one, plastic stiffeners can be more easily cut. This allows the plastic stiffeners to be segmented and packages separated from one another. Also, plastic stiffeners are less expensive than metal stiffeners. As such, the cost of semiconductor processing can be reduced. However, plastic stiffeners, like their metal counterparts, have associated disadvantages. [0009] For example, a supply of adhesive must be procured in order to attach the stiffeners to lead frames. Purchasing, inventorying, and storing the adhesive can add to the cost of die assembly and package processing. Further, attaching a stiffener requires an attachment step be performed during processing, which can require additional processing apparatus, add to processing time, and provide an opportunity for error. Therefore, an improved stiffener and method of applying the same to a substrate is desirable. SUMMARY OF THE INVENTION [0010] In one aspect, the invention provides a semiconductor device comprising a substrate and a stiffener molded to the substrate. [0011] The stiffener can be molded to the substrate by various techniques such as transfer molding, injection molding, or spray molding. The stiffener can also be molded to the substrate with an encapsulating material. Advantageously, the molded stiffener can provide stiffening to the substrate, or increase the rigidity to the substrate. [0012] The molded stiffener can comprise a thermoplastic or a thermosetting polymeric material. In addition, the thermal coefficient of expansion of the molded stiffener and the substrate can correspond such that heating expands both the molded stiffener and the substrate approximately equally. The molded stiffener can be sized to correspond to a length and/or a width of the substrate, or the substrate can be sized to correspond to a length and/or a width of the molded stiffener. [0013] Further, the molded stiffener can include at least one cross member and be in the form of a grid, a lattice, a grille, or a web. In one embodiment, the molded stiffener can protrude from the surface of the substrate and, as a result, form an enclosure for receiving an encapsulating material. In another embodiment, a first surface of the substrate can include a recess formed in the substrate such that the stiffener can be molded to the substrate within the recess. Therefore, the molded stiffener can be flush with the first surface of the substrate. [0014] The substrate can have a first stiffener molded to a first surface of the substrate and a second stiffener molded to a second surface of the substrate. In such an embodiment, the first stiffener and the second stiffener can comprise different configurations and/or dimensions. For example, the first stiffener can protrude from the first surface of the substrate and the second stiffener can be disposed within a recess in the second surface of the substrate. [0015] Another aspect of the invention provides a semiconductor assembly. The semiconductor assembly can comprise a die disposed on a first surface of a substrate as well as a stiffener molded to the first surface of the substrate. In one embodiment, the semiconductor assembly can have a second stiffener molded to a second surface of the substrate and a second die disposed on the second surface of the substrate. [0016] A further aspect of the invention provides a semiconductor die package. The die package can comprise a substrate having a die disposed on the substrate, a stiffener molded to the substrate, and an encapsulating material covering the die. The encapsulating material can be at least partially bounded by the molded stiffener. In one embodiment, the die package can include a second stiffener molded to a second surface of the substrate. The die package can be formed by a technique such as transfer molding. [0017] Another aspect of the invention provides a method of securing a stiffener to a substrate. The method can comprise the steps of providing a stiffener material and a substrate, molding the stiffener material to the substrate, and permitting the stiffener material to harden to form a molded stiffener secured to the substrate. The step of molding can comprise transfer molding, injection molding, spray molding, or molding by applying an encapsulating material to the substrate. The stiffener material can harden by heating the stiffener material, permitting the stiffener material to cool, curing the stiffener material with a catalyst, or curing the stiffener material with exposure to radiation. [0018] Another aspect of the invention provides a method of molding a stiffener to a lead frame assembly. The method can comprise the steps of providing a lead frame assembly, which includes a substrate and two or more die disposed on the substrate, providing a stiffener material, molding the stiffener material to the substrate to form a molded stiffener, and singulating the lead frame assembly, with the molded stiffener thereon, to separate the two or more die. [0019] In one embodiment, prior to the singulation step, the method can comprise the step of encapsulating the two or more die disposed on the lead frame assembly. The encapsulating material can be dispensed onto the die such that the molded stiffener provides a boundary for containing the encapsulating material therein. [0020] Another aspect of the invention provides a method of forming a semiconductor die package. The method can comprise the steps of securing a die to a substrate, molding a stiffener material to the substrate to form a molded stiffener thereon, and encapsulating the die and the molded stiffener with an encapsulating material to form the semiconductor die package. In one embodiment, the step of encapsulating can comprise inserting the substrate, with the die and the molded stiffener disposed thereon, into an opening between two mold plates. After the encapsulating material has hardened, newly formed package can be removed from the mold plates. Continue reading about Molded stiffener for thin substrates... Full patent description for Molded stiffener for thin substrates Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Molded stiffener for thin substrates patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Molded stiffener for thin substrates or other areas of interest. ### Previous Patent Application: Method of embedding semiconductor chip in support plate and embedded structure thereof Next Patent Application: Multiple mask process with etch mask stack Industry Class: Active solid-state devices (e.g., transistors, solid-state diodes) ### FreshPatents.com Support Thank you for viewing the Molded stiffener for thin substrates patent info. 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