Not Applicable
The present invention relates generally to memory cards and, more particularly, to a memory card (e.g., a multi-media card (MMC)) which is configured such that the host socket connector pins travel only over the metallic contacts of the memory card and not any mold compound thereof, thus substantially enhancing the durability of the host socket connector pins.
As is well known in the electronics industry, memory cards are being used in increasing numbers to provide memory storage and other electronic functions for devices such as digital cameras, MP3 players, cellular phones, and personal digital assistants. In this regard, memory cards are provided in various formats, including multi-media cards and secure digital cards.
Typically, memory cards comprise multiple integrated circuit devices or semiconductor dies. The dies are interconnected using a circuit board substrate which adds to the weight, thickness, stiffness and complexity of the card. Memory cards also include electrical contacts for providing an external interface to an insertion point or socket. These electrical contacts are typically disposed on the back side of the circuit board substrate, with the electrical connection to the dies being provided by vias which extend through the circuit board substrate.
In an effort to simplify the process steps needed to fabricate the memory card, there has been developed by Applicant a memory card wherein a leadframe assembly is used as an alternative to the circuit board substrate, as described in Applicant's co-pending U.S. application Ser. No. 09/956,190 entitled LEAD-FRAME METHOD AND ASSEMBLY FOR INTERCONNECTING CIRCUITS WITHIN A CIRCUIT MODULE filed Sep. 19, 2001, of which the present application is a continuation-in-part. As is described in Ser. No. 09/956,190, the leadframe and semiconductor die of the memory card are covered with an encapsulant which hardens into a cover or body of the memory card. The body is sized and configured to meet or achieve a “form factor” for the memory card. In the completed memory card, the contacts of the leadframe are exposed within a common surface of the body, with a die pad of the leadframe and the semiconductor die mounted thereto being disposed within or covered by the body.
Applicant has previously determined that the molding or encapsulation process used to form the body of the card sometimes gives rise to structural deficiencies or problems within the resultant memory card. These problems include portions of the die pad of the leadframe being exposed in the body of the memory card, flash being disposed on the contacts of the leadframe, chipping in a peripheral flange area of the body, and mold gate pull-out wherein a portion of the mold or encapsulating compound is pulled out from within the body, leaving a small recess or void therein. To address these particular problems, Applicant has previously developed a memory card having a “die down” configuration attributable to the structural attributes of the leadframe included therein, and an associated molding methodology employed in the fabrication of such memory card. This die-down memory card is disclosed in Applicant's co-pending U.S. application Ser. No. 10/266,329 entitled DIE DOWN MULTI-MEDIA CARD AND METHOD OF MAKING SAME filed Oct. 8, 2002, the disclosure of which is incorporated herein by reference.
Memory cards, such as multi-media cards, are used by advancing the same into a host socket which includes a plurality of connector pins. Many host sockets include nine connector pins to accommodate the seven contacts included in many memory card formats such as multi-media cards, and the nine contacts included in the secure digital card memory card format. In current memory cards, the bottom surfaces of the contacts are exposed in and substantially flush with the bottom surface of the body of the memory card. A relatively narrow rail or segment of the body extends between and thus separates the contacts from the lateral side of the body which is advanced into the host socket. As a result, the connector pins of the host socket must travel over this rail or segment of the mold compound of the body prior to engaging the exposed bottom surfaces of the contacts of the memory card. The travel or rubbing of the connector pins on the mold compound tends to rapidly wear out the connector pins, especially when the mold compound contains-high levels of filler material. As a result, the host socket connector pins are unable to survive the typical mating insertion requirement of ten thousand insertion cycles.
The present invention addresses and overcomes the above-described deficiencies of currently known memory cards by providing a memory card which is specifically configured to eliminate the travel of the host socket connector pins over the mold compound of the body of the memory card. These and other attributes of the present invention will be described in more detail below.
In accordance with the present invention, there are provided various embodiments of a memory card which is configured in a manner such that the host socket connector pins do not travel over the mold compound of the body of the memory card as a result of an insertion cycle of the memory card into the host socket. More particularly, in accordance with one embodiment of the present invention, the seven contacts or connector pins of a memory card (i.e., a multi-media card) are extended to the adjacent lateral side of the card body so that the host socket connector pins slide or travel only over the contacts of the memory card. In a variation of this configuration, two additional “dummy” contacts are added to the multi-media card to provide protection for the outermost two pins of the nine host socket connector pins that accommodate the nine contacts or pins included in a secure digital card. In an alternative embodiment of the present invention, a laser is used to ablate the mold compound of the body located between the contacts and the adjacent lateral edge or side of the body to create clearance sufficient to prevent the connector pins of the host socket from traveling over or rubbing the card body. In this variation, the above-described dummy pads may also be included to protect the outer two connector pins of the host socket.
The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings.
These, as well as other features of the present invention, will become more apparent upon reference to the drawings wherein:
Common reference numerals are used throughout the drawings and detailed description to indicate like elements.
Referring now to the drawings wherein the showings are for purposes of illustrating preferred embodiments of the present invention only, and not for purposes of limiting the same,
The memory card 10 includes a leadframe having a die attach area or die pad and a plurality of contacts 12. The die pad and contacts 12 each define opposed, generally planar top and bottom surfaces. Integrally connected to and extending from each of the contacts 12 is a conductive trace. The traces terminate in close proximity to the die pad.
In the memory card 10, attached to the die pad is a semiconductor die. Such attachment is preferably facilitated through the use of an epoxy or adhesive. Subsequent to such attachment, the pads or terminals of the semiconductor die are electrically connected to one or more of the traces and/or the die pad through the use of conductive wires or equivalent standard interconnect technology (e.g., flip chip, solder attach, etc.).
The leadframe is preferably fabricated from a conductive metal material (e.g., copper) through either a chemical etching or mechanical stamping process. The leadframe may be formed to include any number of contacts 12 depending on the desired application for the memory card 10. As shown in
In fabricating the memory card 10, an encapsulant material or molding compound is applied to the leadframe, the semiconductor die(s), and any conductive wires used to electrically connect the semiconductor die(s) to the die pad and/or traces. The molding compound is preferably a plastic (e.g., thermoset, thermoplastic) which, upon hardening, forms a body 14 of the memory card 10. The completely formed body 14 defines a generally planar top surface, an opposed, generally planar bottom surface 16, an opposed pair of longitudinal edges or sides 18, and an opposed pair of lateral edges or sides 20. The body 14 also defines a fifth sloped or angled side 22 which extends between one of the longitudinal sides 18 and one of the lateral sides 20. The body 14 is formed such that the bottom surfaces of the contacts 12 are exposed in and substantially flush with the bottom surface 16 of the body 14.
As seen in
To achieve the above-described orientations between the contacts 12 and body 14 in the memory card 10, it is contemplated that the body 14 will be molded in a manner achieving a desired form factor which, in the case of the memory card 10, is a multi-media card form factor as indicated above. The molding techniques which may be employed to facilitate the formation of the body 14 with a prescribed form factor are described with particularity in U.S. application Ser. No. 10/266,329 which, as indicated above, is incorporated herein by reference. In this regard, the memory card fabrication methodology wherein a “skin” is mated to a circuit module as also described in U.S. application Ser. No. 10/266,329 is not well suited for the memory card 10 since such skin would typically define the undesirable rail or segment of material between the contacts and that lateral side of the memory card which is disposed closest to the contacts, such lateral side being defined by the skin itself. Additionally, in the memory card 10, the leadframe defining the contacts 12 may be configured to accommodate attachment of the semiconductor die(s) to the top surface of the die pad as described in U.S. application Ser. No. 09/956,190 or to the bottom surface of the die pad in a “die down” configuration as described in U.S. application Ser. No. 10/266,329.
Referring now to
As indicated above, the memory card 10 includes seven contacts 12, thus being adapted for use in a multi-media card application. The host socket in which the memory card 10 is advanced will typically include nine connector pins to accommodate not only the memory card 10, but further to accommodate those memory cards which are configured as secure digital cards and include nine contacts. In this regard, though the memory card 10a includes seven contacts 12a in a multi-media card format, the inclusion of the additional dummy pads 24a causes the memory card 10a to mimic a secure digital card format, the dummy pads 24a thus effectively protecting the outermost two connector pins of the host socket from wear. In this regard, rather than such outer two connector pins of the host socket traveling or rubbing across the body 14a, they travel only across the metal material of the dummy pads 24a.
Though, as indicated above, the memory cards 10, 10a each have a form factor of a multi-media card, those of ordinary skill in the art will recognize that the principles of the present invention may be applied to memory cards having alternative formats, such as a secure digital card format. For example, in applying the principles of the present invention to a memory card in a secure digital card format, the nine contacts of such secure digital card would extend to the lateral side or edge of the card disposed closest thereto.
Referring now to
In fabricating the memory card 30, an encapsulant material or molding compound is applied to the leadframe, the semiconductor die(s), and any conductive wires used to electrically connect the semiconductor die(s) to the die pad and/or traces. The molding compound is preferably a plastic (e.g., thermoset, thermoplastic) which, upon hardening, forms a body 34 of the memory card 30. The completely formed body 34 defines a generally planar top surface 35, an opposed, generally planar bottom surface 36, an opposed pair of longitudinal edges or sides 38, and an opposed pair of lateral edges or sides 40. The body 34 also defines a fifth, sloped or angled side 42 which extends between one of the longitudinal sides 38 and one of the lateral sides 40. The body 34 is formed such that the bottom surfaces of the contacts 32 are exposed in and substantially flush with the bottom surface 36 of the body 34.
In the memory card 30, the body 34 is formed in accordance with current techniques such that a continuous, relatively narrow rail or segment of the body 34 initially extends between and thus separates the contacts 32 from the lateral side 40 of the body 34 disposed closest thereto. To eliminate occurrences of the travel or rubbing of the connector pins of the host socket over such rail or segment of the body 34, in the memory card 30, the body 34 is subjected to a laser ablation process which effectively removes or ablates a portion of the rail of the body 34 which extends between the contacts 32 and adjacent lateral side 40. As seen in
The body 34 of the memory card 30 may be molded in a manner achieving a desired form factor which, in the case of the memory card 30, is a multi-media card form factor as indicated above. The molding techniques which may be employed to facilitate the formation of the body 34 with a prescribed form factor are described with particularity in U.S. application Ser. No. 10/266,329. Additionally, the memory card fabrication methodology wherein a “skin” is mated to a circuit module as also described in U.S. application Ser. No. 10/266,329 may also be used in relation to the memory card 30 since a portion of such skin may be ablated in the above-described manner as needed to prevent the connector pins of the host socket from traveling thereover. In the memory card 30, the leadframe defining the contacts 32 may be configured to accommodate the attachment of the semiconductor die(s) to the top surface of the die pad as described in U.S. application Ser. No. 09/956,190 or to the bottom surface of the die pad in a “die down” configuration as described in U.S. application Ser. No. 10/266,329.
Referring now to
This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.
The present application is a continuation-in-part of U.S. application Ser. No. 09/956,190 entitled LEAD-FRAME METHOD AND ASSEMBLY FOR INTERCONNECTING CIRCUITS WITHIN A CIRCUIT MODULE filed Sep. 19, 2001.
Number | Date | Country | |
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Parent | 10626814 | Jul 2003 | US |
Child | 11250816 | US |
Number | Date | Country | |
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Parent | 09956190 | Sep 2001 | US |
Child | 10626814 | US |