One of the major trends in the semiconductor packaging industry is to use surface-mount technology (SMT) as a replacement for conventional plated-through-hole (PTH) technology. SMT offers several distinct advantages over PTH technology, such as greater packaging density, higher lead counts with shorter interconnection lengths and easier automation. Since SMT requires electronic devices and components to be mountable on the surface of a printed circuit board (PCB) or substrate, the materials and structure of traditional through-hole components including capacitors, resistors, and inductors have to be redesigned to meet the modern-day demand for short, thin, light, and small electronic devices. Examples of semiconductor devices accomplishing these objects include quad flat non-leaded packages. Quad flat non-leaded packages have a package structure in which space-consuming outer leads protruding laterally out of a package are eliminated. Instead, external electrode pads to be electrically connected to a circuit board are provided on the bottom surface of the quad flat non-leaded package. The bottom surface of the package that connects to the circuit board may be referred to as the backside of the package as used herein.
A quad flat non-leaded package, especially a leadless leadframe package, makes use of a metal leadframe as a support structure in the packaging of a semiconductor die. Typically a plurality of leadframes are provided together in a strip of leadframes for packaging multiple dice. Each leadframe includes a die attach pad (die-pad) and one or more contacts (lead-pads) disposed about the leadframe. During assembly, dice are attached to the respective die-pads and wire bonding is used to electrically couple contacts of each die to their associated lead-pads. Wirebonding may be performed using a number of different methods including ball bonding, wedge bonding, etc. As used herein wirebonding is generically used to refer to various methods known in the art used to electrically couple contacts of a die to associated lead-pads. After the wire bonding process, the leadframes and dice are encapsulated by molding a packaging material, for example, a resin, over the top surface of the wire-bonded dice and leadframes. The encapsulated leadless leadframe packages are then singulated using conventional sawing. The packaged die may then be mounted on a printed circuit board (PCB). When mounted, the bottom surface of lead-pads and/or die-pads on the backside of the package connect with PCB contacts to connect the die with PBC circuitry.
The area of the die-pads and lead-pads on the backside of the package may be restricted to meet a set of design and layout rules. A design rule set specifies certain geometric and connectivity restrictions to ensure sufficient margins to account for variability in the manufacturing processes, ensure various electrical characteristics, and reduce area requirements of a circuit. However, it may be desirable to have a semiconductor die that is larger than the allowed area for the contact on the backside of the die-pad.
One or more embodiments may address one or more of the above issues.
In one embodiment, a method is provided for packaging a semiconductor die. A leadframe having a die-pad and one or more lead-pads is placed on an assembly surface. The die-pad has a base portion resting on the assembly surface, an upper portion on the base portion extending laterally from the base portion, and a support arm extending from and supporting the upper portion of die-pad. A semiconductor die is bonded to a top surface of the upper portion of the die-pad. The semiconductor die is wire bonded to the one or more lead-pads. The semiconductor die and leadframe are encased in a package material. The package material fills a space between the upper portion of the die-pad and the assembly surface. A portion of the support arm is removed.
In another embodiment, an intermediate structure is provided for making an electronic package. The intermediate structure includes a die-pad having a base portion and an upper portion above and extending laterally from the base portion. A semiconductor die is mounted on a top surface of the upper portion of the die-pad. A support arm extends from and supports the upper portion of the die-pad. The support arm extends beyond an area defined by the outline of the electronic package.
In yet another embodiment, an article of manufacture is provided. The article is characterized by a plurality of electronic packages arranged in a row or matrix. Each one of the electronic packages includes a die-pad and a semiconductor die mounted on a top surface of the die-pad. Between pairs of adjacent die-pads, respective connection arms connect the pairs of die-pads. A support arm extends from each connection arm and provides support for the die-pads connected thereto. The support arm extends into a cutting lane of the plurality of the electronic packages.
The above discussion is not intended to describe each embodiment or every implementation. Various example embodiments may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which:
While the disclosure is amenable to various modifications and alternative forms, examples thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments shown and/or described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.
In one or more embodiments, a leadframe and method for die packaging are provided. The leadframe and method utilize one or more lead-pads and one or more die-pads. Each die-pad includes a base portion and an upper portion over the base portion. The upper portion is larger than the base portion and provides a die mounting surface that is larger than a die mounting surface that would be available with just the base portion. The upper portion extends laterally from the base portion. During assembly, however, the part of the upper portion that extends from the base portion may cause the die-pad to become unbalanced or unstable during the wirebonding and packaging processes. In one or more embodiments, a support arm is disposed in a cutting lane between die packages. The support arm provides support and increases stability of the die-pad during the wirebonding process. Once the die and die-pad are encapsulated in packaging material, support arms located in the cutting lanes are removed as a result of singulation of the packages.
It is recognized that the leadframe may include any number of die-pads and lead-pads to provide external contacts for respective contact pads of the die(s) included in each package. For ease of explanation, the embodiments and examples are primarily described with reference to a semiconductor package having two external contacts formed by a bottom surface of one die-pad and a bottom surface of one lead-pad.
The base portion 106 of the die-pad 102 rests on an assembly surface during packaging. As discussed above, due to a particular design and associated design rules, the base portion 106 of the die-pad 102 may not provide adequate support for the die-pad. As a result, the weight of the semiconductor die 108 on the upper portion 104 or the forces of the wirebonding process may cause the die-pad 102 to tip, or otherwise become unbalanced during packaging. In one or more embodiments, the leadframe 100 is implemented to include a support arm (not shown) extending from the upper portion 104 of the die-pad 102 to provide stability to the die-pad during packaging. The support arm is formed in a cutting lane, outside dimensions of the complete packaged semiconductor die, so that the support arm is removed during the packaging process. Because the support arm is not present in the final package, the support arm does not conflict with any restrictions imposed by design rules.
Various structures for supporting the die-pad may be located in the cutting lane, and outside the dimensions of what will eventually be the completed package.
Block 230 in
For purposes of explanation, base portion 202 and upper portion 204 of the die-pad are depicted as separate elements. It will be appreciated that the base portion 202 and upper portion 204 may be a monolithic structure. Likewise, support arm 208 may be integrally formed as part of the die-pad. Alternatively, the portions and support arm may be formed separately and attached as shown.
In some embodiments, the die-pad may be electrically coupled to a contact pad on the bottom of the semiconductor die. For example, the die contact may be electrically coupled to the die-pad using a conductive bonding substance, such as a conductive adhesive or a solderable material such as solder paste or solder. In some other embodiments, a contact pad of the semiconductor die may be wirebonded to the die-pad.
In this illustrative example, the leadframes are encapsulated together, with the packaging material filling the areas in the cutting lanes between the leadframes. In some embodiments, a portion of the support arm may be left exposed and not encased by packaging material.
Based upon the above discussion and illustrations, those skilled in the art will readily recognize that various modifications and changes may be made without strictly following the exemplary embodiments and applications illustrated and described herein. Such modifications do not depart from the true spirit and scope of the present disclosure, including that set forth in the following claims.
Number | Date | Country | Kind |
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11165403.4 | May 2011 | EP | regional |