Lead-frame connector and circuit module assembly

This application relates to a previously filed U.S. patent application entitled “LEAD-FRAME METHOD AND ASSEMBLY FOR INTERCONNECTING CIRCUITS WITHIN A CIRCUIT MODULE” Ser. No. 09/956,190 filed Sep. 19, 2001, the specification of which is herein incorporated by reference.

The present invention relates generally to lead-frame assemblies for mounting integrated circuit dies, and more specifically, to a lead-frame assembly including connector pins and a method for fabricating a lead-frame assembly with connector pins.

Circuit modules or cards are increasing in use to provide storage and other electronic functions for devices such as digital cameras, personal computing devices and personal digital assistants (PDAs). New uses for circuit modules include multimedia cards and secure digital cards.

Typically, circuit modules contain multiple integrated circuit devices or “dies”. The dies are interconnected using a circuit board substrate, which adds to the weight, thickness and complexity of the module. Circuit modules also have electrical contacts for providing an external interface to the insertion point or socket. Some circuit module standards use contact pads on the bottom side of the substrate, and the above-incorporated patent application teaches a method and assembly wherein a substrate is not required and the contact pads are replaced with lead-frame contacts. As described in the above-incorporated patent, it is desirable for a number of reasons to produce a circuit module without a substrate, and the lead-frame embodiments taught therein provide a circuit module without a substrate and having a contact pad interface formed within the lead-frame carrier.

However, some circuit module standards such as Compact Flash (CF) require a pin connector located on a side of the circuit module, and in some cases the pin connector has multiple rows. (CF cards require a dual-row female 50-pin connector.) A typical CF circuit module (and other pin connector modules) includes a pin connector mounted on a substrate used to provide an electrical interface to external devices. The substrate is required to mount and electrically connect the pin connector to one or more semiconductor dies incorporated within the circuit module. Further, pin connectors are typically expensive items that form a significant portion of the manufacturing cost of a circuit module.

Therefore, it would be desirable to provide a method and assembly for including a pin connector within circuit modules without requiring a substrate. It would further be desirable to provide a multi-row pin connector within a lead-frame assembly. It would also be desirable to provide a pin connector within a circuit module assembly without requiring a discrete connector component.

A lead-frame connector and circuit module assembly provides a pin connector type circuit module without a circuit board substrate or discrete pin connector. A lead-frame assembly is connected to one or more dies and external pin contacts are formed by connector pins integral to an extension of the lead-frame assembly. A multiple row pin connector may be implemented by forming some of the pins out of the plane of the lead-frame assembly die mounting level. A novel female connector pin design provides female connector contacts using pins that are offset within the pin housing and are supported by the housing to eliminate any need for hardening of the connector pins.

In another embodiment of the invention, a substrate is included to provide mounting and interconnection of the semiconductor dies, but a lead-frame with formed connector pins is used to implement the connector and the lead-frame is then electrically connected to the substrate.

The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings.

FIG. 1A is a pictorial diagram depicting a top view, FIG. 1B is a pictorial diagram depicting a side view and FIG. 1C is a pictorial diagram depicting a cross section of a prior art circuit module;

FIG. 2A is a pictorial diagram depicting a top view, FIG. 2B is a pictorial diagram depicting a side view and FIG. 2C is a pictorial diagram depicting a cross section of a circuit module including a lead-frame carrier in accordance with an embodiment of the invention;

FIG. 3 is a pictorial diagram depicting a top view of a lead-frame carrier in accordance with an embodiment of the invention; and

FIG. 4 is a pictorial diagram depicting a top view of circuit module assembly in accordance with an alternative embodiment of the invention.

Common reference numerals are used throughout the drawings and detailed description to indicate like elements.

Referring now to the figures and in particular to FIG. 1A , a top view of a prior art circuit module 10 is depicted. A cutaway view 12 is used to show internal details of circuit module 10 . Circuit module 10 is depicted as a circuit module as used in various card memory applications, such as Compact Flash (CF).

A carrier 18 to which integrated circuit die 13 is attached and surface mount integrated circuit (IC) 17 and discrete component 16 is mounted, is covered by a cover 19 that is bonded to carrier 18 . The circuit module housing may be completely formed from an encapsulant, or the circuit may be encapsulated and a lid applied over the encapsulant. Die 13 , discrete component 16 and surface mount IC 17 are coupled to each other and to a connector 11 by circuit pattern 14 , which is typically etched from a metal layer on the top of carrier 18 . Die 13 is wire-bonded to circuit pattern 14 as shown by wires 15 .

Connector 11 is typically soldered to lands of circuit pattern 14 , but may be attached with conductive adhesive or conductive tape. Carrier 18 , may be a single-sided, double-sided or multi-layer printed wiring board (PWB) or other suitable circuit substrate. Connector 11 is typically a component purchased by the manufacturer of circuit module 10 and typically has features such as annealed and plated connector pins for mechanical and environmental durability. As such, connector 11 contributes greatly to the overall cost of circuit module 10 . For applications such as CF, a dual-row 50-pin female connector is required within circuit module 10 for mating with a 50-pin male connector of an external device. The female connector pins are typically pins with a rectangular face with a slot provided through the middle for receiving and retaining the male connector pins of the external device. FIG. 1B depicts a side view of circuit module 10 , showing the location of 50-pin female connector 11 .

Referring now to FIG. 1C , a cross-section of circuit module assembly 10 is depicted. Die 13 is shown mounted to carrier 18 on which circuit pattern 14 is formed. Surface mount IC 17 is attached to circuit pattern 14 and connector 11 is also attached to circuit pattern 14 . Cover 19 encloses the assembly, providing a circuit module form factor in accordance with the CF specifications.

Referring now to FIG. 2A , a circuit module 20 , in accordance with an embodiment of the present invention is shown. Circuit module 20 is depicted as a circuit module as used in various card memory applications, such as Compact Flash (CF). The present invention is also applicable to cards and modules having other outlines such as personal computer memory cards and peripheral device cards (I/O cards), as well.

A cutaway view 22 is used to show internal details of circuit module 20 . A lead-frame carrier 26 , having integral connector pins 21 formed at an end thereof, is included within circuit module 20 to interconnect dies 13 A and 13 B and an external device via connector pins 21 . An encapsulation 19 A surrounds the internal components of circuit module 20 , and further provides the housing for connector pins 21 . Details of lead-frame based circuit modules without integral connector pins are described in the above-incorporated patent application “LEAD-FRAME METHOD AND ASSEMBLY FOR INTERCONNECTING CIRCUITS WITHIN A CIRCUIT MODULE.”

The present invention eliminates the cost of a discrete connector component from the cost of circuit module 20 assembly. The reliability of the circuit module may also be improved by the elimination of the interconnection between a discrete connector and the carrier. Furthermore, the size of the discrete connector shell is no longer a factor in the design of the circuit module housing, as the circuit module housing forms the connector shell in accordance with embodiments of the present invention.

Referring now to FIG. 2B , a side view of circuit module 20 is depicted, showing the location of a 50-pin female connector 11 A formed by encapsulation 19 A and connector pins 21 . Callout 23 shows details of the connector pin 12 arrangement. Connector pins 21 are divided into a first set 24 A and a second set 24 B of connector pins 21 , forming a first and second row of female connector 11 A. Every other connector pin 21 of lead-frame 26 is bent out of the plane of lead-frame 24 A, thereby providing an extension forming a second row (second set 24 B) of connector contacts.

In order to simplify the manufacture of connector 11 A, a novel pin arrangement is used. Connector pins 21 in the first set 24 A are arranged at one side of recesses 27 formed in encapsulation 19 A, and connector pins 21 in the second set 24 B are arranged at the opposite side of recesses 27 . Male connector pins of an external device contact connector pins 21 by sliding contact with the face of connector pins 21 . Connector pins 21 are further tapered to provide positive mating as connector 11 A is inserted in an external device socket. Encapsulant 19 A over-molds connector pins 21 by approximately 90% of the thickness of connector pins 21 , providing an over-mold 25 , that secures connector pins 21 within recesses 27 . Thus, hardening of connector pins 21 is not required to provide a reliable connector 11 A. Lead-frame 26 is also plated during fabrication with Nickel-Palladium plating. Therefore selective plating of connector pins 21 is not necessary to protect connector pins 21 from the external environment, but may be performed to increase reliability or improve electrical contact. Selective silver or gold plating may therefore be applied to connector pins 21 .

Referring now to FIG. 2C , a cross section view of circuit module 20 is depicted in accordance with an embodiment of the invention. Dies 13 A and 13 B are connected to lead-frame carrier 26 by wires 15 bonded to lands on dies 13 A, 13 B and lead-frame carrier 26 . Encapsulant 19 A covers dies 13 A, 13 B and lead frame carrier 26 (except the connector pin 21 portion within recesses 27 ). Callout 28 depicts the tapered shape of connector pins 21 . A tapered face 29 is cut or stamped on connector pins 21 , and lead-frame 26 is generally pre-fabricated with the tapered shape. Second row 24 B of connector pins 21 is shown bent upward from the plane of lead frame 26 . Second row 24 is bent prior to assembly. Connector pins 21 are stamped or cut to protrude past a dam bar, providing a lead-frame in which connector pins 21 may be bent into multiple rows prior to singulation of the dam bar.

Referring now to FIG. 3 , a top view of a lead-frame 26 A in accordance with an embodiment of the invention is depicted. Leads 43 , terminating in connector pins 21 A, are supported by a dam bar 44 that surrounds the periphery of the lead-frame on three sides providing rigidity during the fabrication and integration processes (A fourth dam bar 44 side may be provided at the location of connector pins 21 A but must be removed prior to bending pins if the connector implementation is multi-row). Lead-frame 26 A is generally stamped from a metal, such as copper, and an integrated circuit die is bonded to lead-frame in die bonding area 41 . Wire bonding pads 41 are provided on leads 43 to permit attachment of wires from a die to the lead-frame. Connector pins 21 A are bent, as described above, for implementation of a multi-row connector.

Lead-frame 26 A is then encapsulated (except for the recesses containing connector pins 21 A and portions of dam bar 44 are cut, resulting in electrical isolation of leads 43 , after mechanical rigidity has been provided by the encapsulant. Alternatively, the circuit mounting portion of lead frame 26 A may be molded separately, prior to or after encapsulating connector pins 21 A. In addition or in alternative to wire bonding pads 43 , pads may be included for attachment of surface mounted passive components by soldering or conductive adhesive attachment, and pad grids may be included for attachment of pre-packaged integrated circuits.

The illustrative embodiments herein depict an etched or stamped lead-frame. The embodiment depicted in the above illustrations, wherein connector pins are bent to provide dual contact rows especially lends itself to stamping, because leads 43 and connector pins 21 A may be formed and bent in a single stamping operation.

Referring now to FIG. 4 , a top view of a circuit module assembly 30 , in accordance with an alternative embodiment of the invention is depicted. The depiction shows the internal features of a circuit module after a carrier 18 A has been bonded to a lead-frame 26 B. Carrier 18 A may have various integrated circuit dies 49 , surface mount discrete components 48 and surface mount integrated circuits 45 mounted thereon and is generally a PWB-type substrate having a circuit patterns 46 for interconnection of the various mounted components.

A lead-frame 26 B, including connector pins 21 B, but no circuit mounting area (hence lead-frame and not lead-frame carrier), is electrically and mechanically coupled to carrier 18 A by solder, conductive tape 47 or epoxy, wire bonding (with wire bonding areas supplied on both lead-frame 26 B and carrier 18 A), or an alternative coupling scheme. Mechanical gluing may be used frame 26 B includes a dam bar 34 for support of leads 43 A, prior to singulation of connector pins 21 B. The ends 31 of connector pins 21 B may be pre-bent, permitting first gluing and electrical attachment of lead-frame 26 B to carrier 18 A, then singulating connector pins 21 B by sawing dam bar 34 , and finally encapsulating the entire circuit module assembly 30 (except for the recesses containing connector pins 21 B). Callout 38 depicts details of connector pins 21 B, showing the staggered arrangement 37 of connector pins 21 B after bending.

The above-described embodiment of the invention provides the low cost associated with the lead-frame connector of the present invention, but with a standard PWB carrier that may more readily provide mounting for discrete components and reduce circuit area using multiple layers of printed circuits within the carrier.

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.