Patent Application
20060108681
The present invention relates generally to semiconductor devices and, more particularly, to an improved package including such devices.
An important part of Integrated Circuit (IC) technology is the packaging of the semiconductor component. One consideration in the proper functioning of the component is to provide adequate heat dissipation away from the component during operation. Another consideration is to provide protection of the component in the form of some type of encapsulant. For example, one type of package, known in the art as a Heat Slug Plastic Ball Grid Array (PBGAH), includes a copper heat slug embedded within an Epoxy Molding Compound (EMC) which protects the IC component.
It is desirable in such packages to fabricate the heat slug by stamping, which is a highly economical process. It is also desirable to place the heat slug as close as possible to the component for maximum heat dissipation. One design utilizes a heat slug with a uniform height and thickness over the IC component. (See, e.g., U.S. Pat. No. 6,191,360 issued to Tao et al.) Since the component is typically electrically connected to the substrate by wire bonding, increasing the thickness of the slug to get it closer to the component could result in electrically shorting the wires due to contact with the heat slug. In another design, the slug is brought closer to the component by means of a protruded portion over the IC. One disadvantage of such a design is that the slug no longer has a uniform thickness, and cannot be made by stamping. A still further design includes a protruded portion with a uniform thickness which makes direct physical contact with the IC component. (See, e.g., U.S. Pat. No. 6,229,702 issued to Tao et al.) In this design it is important not to apply too much pressure to the heat slug, otherwise the IC component could be damaged. It is therefore important to reduce the height of the heat slug, otherwise the clamp used in the molding process could damage the IC component. However, the reduced height increases the chance of shorting with the wires connected to the substrate, and also allows the EMC layer to be formed over the heat slug reducing the heat dissipation. To avoid these problems, the heat slug thickness is usually reduced, but this lessens the ability of the heat slug to dissipate, heat.
It is desirable, therefore, to provide a semiconductor package which includes a heat dissipating element embedded within a protective layer, where the element has a uniform thickness so that it can be formed by stamping, and where the element does not physically contact the semiconductor component.
To achieve these and other objects, and in view of its purposes, the present invention in one aspect, provides a semiconductor component package which includes a semiconductor component, such as an integrated circuit, mounted on a substrate, a protective material formed over the semiconductor component, and a heat dissipating element embedded within the protective material. The heat dissipating element comprises a heat conducting sheet having an essentially uniform thickness with a first portion having a first height. The heat dissipating element also includes a second portion having a second height which is less than the first height. The second portion lies over at least a part of the semiconductor component, but does not make physical contact thereto.
In accordance with a second aspect, the invention is a method of fabricating a semiconductor component package which includes the steps of mounting a semiconductor component, such as an integrated circuit, over a substrate. A heat dissipating element is formed from a heat conducting sheet with an essentially uniform thickness having a first portion with a first height and a second portion with a second height which is less than the first height. The heat dissipating element is mounted over the substrate so that the second portion is over at least a part of the semiconductor component but does not make physical contact therewith. A protective layer is formed over the component and heat dissipating element.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.
The invention is best understood from the following detailed description when read in connection with the accompanying drawing. It is emphasized that, according to common practice in the semiconductor industry, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawing are the following figures:
Referring now to the drawing, wherein like reference numerals refer to like elements throughout,
The heat dissipating element, 20, is formed from a metal sheet which in this example is copper, but could be any metal or other material capable of conducting heat away from the IC, 14. Since the element, 20, has an essentially uniform thickness, it can be formed by standard stamping techniques. In this example, the thickness is 0.3 mm, but thicknesses in the range 0.1 mm to 0.5 mm are generally useful. The element, 20, is shaped to include a first portion, 21, which has a height, h1, and a second portion, 22, which has a height h2. It will be noted that h2 is less than h1, and that the second portion, 22, preferably lies as much as possible over the IC component, 14, for wire bonded packages without touching the wires 16 and 17, while the first portion, 21, lies primarily over the area of the substrate not including the IC component. It will also be noted that the second portion, 22, is close to but does not touch the IC component. Preferably, the second portion will lie a distance from the component, 14, which is in the range 0.1 mm to 0.42 mm. The element, 20, is mounted to the substrate, 11, by applying an adhesive, 25, to the feet, e.g, 23 and 24, of the element, 20, and contacting the feet to the substrate. The feet are typically bumps which are stamped in the element so that the protective material can flow underneath the element during the encapsulation process, but are not essential to the invention. (It will also be noted that h1 and h2 are measured from the bottom of the feet to the top surfaces of their respective portions, 21 and 22.)
It will be noted that the height, h1, of the first portion, 21, is chosen to provide sufficient clearance of the heat dissipating element, 20, from the wires, 16 and 17, so that no shorting will occur. In this example, the height, h1, was 1.17 mm, but heights in the range 1.17 mm to 1.22 mm are recommended. The height, h2, was chosen to bring the heat dissipating element, 20, as close as possible to the semiconductor component, 14, without making contact therewith, so that the element, 20, can conduct heat away from the component efficiently without damaging the component. In this example, the height, h2, was 0.8 mm, but heights in the range 0.55 mm to 0.87 mm are generally useful depending on the thickness of the semiconductor component, 14. In general, the difference between h1 and h2 will be in the range 0.3 mm to 0.62 mm.
Subsequent to the mounting of the heat dissipating element, 20, to the substrate, 11, the protective layer, 18, is formed over the substrate, semiconductor component, and heat dissipating element. Any standard deposition technique can be employed. It is preferred, when using an epoxy molding compound, to deposit by a transfer molding process. Since the material can flow in the horizontal and vertical directions, it is preferred to include a hole, 26, in the portion, 22, of the heat dissipating element to facilitate the flow of the material over the semiconductor component, 14. (See also the top view of element, 20, illustrated in
Although the invention has been described with reference to exemplary embodiments, it is not limited to those embodiments. For example, while the portion 22 is shown only over the IC component, 14, it could extend outside the area above the component for components that are not contacted by wire bonding. Rather, the appended claims should be construed to include other variants and embodiments of the invention which may be made by those skilled in the art without departing from the true spirit and scope of the present invention.
This application claims the benefit of co-pending provisional patent application No. 60/630442, filed Nov. 23, 2004.
| Number | Date | Country | |
|---|---|---|---|
| 60630442 | Nov 2004 | US |
