Metal working – Means to assemble or disassemble – Means to assemble electrical device
Reexamination Certificate
2000-08-11
2004-02-10
Arbes, Carl J. (Department: 3729)
Metal working
Means to assemble or disassemble
Means to assemble electrical device
C029S827000, C029S281100, C029S281500, C361S736000
Reexamination Certificate
active
06687980
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to microelectronic assemblies and more particularly relates to methods of mass producing semiconductor chip assemblies.
BACKGROUND OF THE INVENTION
A semiconductor chip is generally connected to an external circuit element through contacts on the front face of the chip. For example in the tape automated bonding process (hereinafter referred to as the “TAB” process), a dielectric sheet, such as a thin foil of polyimide, is provided with one or more bond windows and an array of metallic leads on one surface thereof. Each lead has one end integrally connected to terminals on the dielectric sheet and an opposite end extending outwardly from a central portion of the dielectric sheet so that the outermost ends of the leads project beyond the bond windows. The dielectric sheet is juxtaposed with the semiconductor chip so that the bond windows are aligned with the contacts on the chip and so that the outermost ends of the leads overlie the front face of the chip. The leads are then bonded to the contacts of the chip using bonding techniques such as ultrasonic or thermocompression bonding. After the bonding step, the terminals are connected to an external circuit element, such as a printed circuit board, which electrically interconnects the chip and the printed circuit board.
Commonly assigned U.S. Pat. No. 5,148,266, the disclosure of which is incorporated by reference herein, discloses a method of manufacturing semiconductor chip assemblies which are fabricated in a substantially continuous sheet or strip. A plurality of connection components are spaced lengthwise along a continuous tape, each connection component having terminals and flexible leads thereon. In one assembly method, semiconductor chips are connected to respective connection components on the tape and the assembled semiconductor chips are then carried downstream with the tape for further processing steps.
Commonly assigned U.S. Pat. No. 5,659,952, the disclosure of which is incorporated by reference herein, provides methods of fabricating a semiconductor chip assembly having a compliant interface. In preferred methods according to U.S. Pat. No. 5,659,952, a flexible, substantially inextensible dielectric film having a surface is provided and a plurality of compliant pads are attached to the first surface of the dielectric film, whereby any two adjacent compliant pads define a channel therebetween. Attaching the compliant pads to the dielectric film may be accomplished in a number of different ways. In one embodiment, a stencil mask having a plurality of holes extending therethrough is placed on top of the first surface of the dielectric film. The holes in the stencil mask are then filled with a curable liquid elastomer. Desirably, liquid elastomer has a thick enough consistency so that the mask may be removed before curing the elastomer. After the mask has been removed, the elastomer is at least partially cured using energy, such as heat or ultraviolet light. The holes in the mask are preferably filled with the liquid elastomer by screening the liquid elastomer across an exposed surface of the mask such that the elastomer is deposited into the holes of the mask. Thus, there is provided an assembly which includes an array or plurality of compliant pads defining channels therebetween, i.e. the channels run between adjacent compliant pads.
In further stages of the process disclosed in U.S. Pat. No. 5,659,952, the assembly including the array of compliant pads is assembled to a second support structure, such as a semiconductor chip having a front face with contacts. During the assembly step, the front contact bearing face of the chip is abutted against the array of compliant pads and the contacts are electrically connected to terminals on a second surface of the dielectric film remote from the chip. A compliant filler, such as a curable liquid elastomer, may then be injected into the channels between the semiconductor chip and the dielectric film and around the compliant pads while the chip and the dielectric film are held in place. The curable liquid elastomer may then be cured to form a substantially uniform, planar, compliant layer between the chip and the dielectric film.
However, further improvements in handling of the components during assembly processes, such as those described in U.S. Pat. No. 5,659,952, would be desirable.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a method of making a microelectronic assembly includes the steps of providing a flexible tape having first and second surfaces and including a plurality or array of connection components in a central region thereof. The flexible tape typically includes a dielectric film, such as a polyimide, whereby each connection component includes a part of the dielectric film having electrically conductive parts. The flexible tape includes one or more border regions which surround the central region bearing the plurality of connection components. The electrically conductive parts typically comprise an array or plurality of conductive terminals accessible at one surface of the dielectric film and may also include flexible leads integrally connected to the terminals. Each connection component also includes an attachment region for receiving a resilient element, such as an array or plurality of compliant pads, as will be discussed in more detail below. The attachment region of each connection component are preferably provided at the first surface of the flexible tape with the terminals preferably accessible at the second surface of the flexible tape.
A carrier frame, having a top surface and a bottom surface, is typically provided for processing the flexible tape. The carrier frame is desirably between approximately 250-400 microns thick and comprises a rigid material, such as a metal or plastic. The carrier frame has one or more inner edges which define a slot extending between the top and bottom surfaces thereof. In certain preferred embodiments the slot is elongated and the carrier frame includes a cut-out region which is contiguous with one end of the slot, whereby the width of the cut-out region is greater than the width of the slot.
In further stages of preferred assembly methods, the flexible tape is placed on a top surface of a work holder and the carrier frame is placed over the flexible tape so that the second surface of the flexible tape (i.e., the terminal side) is in contact with the surface of the carrier frame. The width of the flexible tape is greater than the width of the slot. Therefore, when the flexible tape overlies the carrier frame and is substantially parallel to and in contact therewith, the side border regions of the tape preferably extend beyond the one or more of the inner edges of the carrier frame. However, the width of the cut-out region is greater than the width of the flexible tape so that portions of the flexible tape overlying the cut-out region are typically bounded by the cut-out region.
In further stages of the process, one end of the flexible tape is secured to the carrier frame and is preferably hingedly or pivotally secured thereto. In certain preferred embodiments, the portion of the flexible tape extending into the cut-out region is pivotally secured to the carrier frame by affixing flexible strips to the border regions of the flexible tape overlying the cut-out region. The flexible strips may be removed and desirably include an adhesive thereon which secures to the border region of the tape. In certain preferred embodiments, each flexible adhesive strip has a first end connected to the border regions of the flexible tape overlying or extending into the cut-out region and a second end connected to the carrier frame.
In the next stage of the process, during a first processing operation, a resilient element is provided over the attachment region of each connection component. The resilient element may be provided by forming a plurality or array of compliant pads on each attachment region, such as by using the methods described in
Link Joseph
Raab Kurt
Arbes Carl J.
Lerner David Littenberg Krumholz & Mentlik LLP
Phan Tim
Tessera Inc.
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