Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Assembly of plural semiconductive substrates each possessing...
Utility Patent
1998-05-05
2001-01-02
Dinh, Son T. (Department: 2824)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Assembly of plural semiconductive substrates each possessing...
C438S106000, C228S006200, C033S286000
Utility Patent
active
06168971
ABSTRACT:
TECHNICAL FIELD
The present invention relates to techniques for mounting multiple components on a substrate, and more specifically, to a method of assembling more than one properly aligned thin film jumper connector to a substrate using a standard flip-chip bonding machine which performs a single alignment operation at a time.
BACKGROUND OF THE INVENTION
Flip-chip bonding is a method of electrically connecting an integrated circuit chip or other component to a substrate, e.g., a chip carrier. The substrate typically includes bonding pads for the chip which may be connected by a set of conductive lines to contact pads for a package or to other bonding pads on the substrate. The conductive lines thus form an interconnect network or I/O path for multiple elements mounted on a common substrate. In flip-chip (or solder bump) bonding, solder bumps are placed on the pads of the chip. The chip is placed on a holder in a face-up position, flipped over (i.e., face-down) and aligned with the corresponding conductive bonding pads on the substrate. The solder is then reflowed, causing the bumps to fuse with the bonding pads and providing electrical connection between the chip's I/O pads and the substrate.
Standard flip-chip bonding equipment typically includes a chuck, a moveable assembly platform, and a split-field viewer. When bonding a chip to a chip carrier or substrate, for example, the substrate is placed on the chuck in a face-up position, and the chip is placed on the moveable platform in a face-up position. The platform is then rotated 180 degrees so that the chip is face-down. The chip is then moved into coarse alignment with the substrate, but separated from it by several millimeters. The split-field viewer is interposed between the chip and the substrate, and is used to provide the viewer with simultaneous views of the chip and the substrate. Using these views, the viewer aligns the solder bumps of the chip with the corresponding bonding pads of the substrate. Typically, each of the two components to be bonded has cross-hair alignment marks which are used for this precise alignment.
Once the chip and the substrate are correctly aligned, the split-field viewer is retracted and the assembly platform holding the chip is lowered to bring the chip's solder bumps into physical contact with the substrate's bonding pads. The solder bumps typically have a layer of solder flux formed over them, and when heated, the solder reflows, establishing good electrical contact between the chip and the substrate. Note that although in the example described, the solder bumps are on the chip's I/O or bonding pads, the solder bumps may instead be placed on the substrate bonding pads.
Standard flip-chip bonding machines are only intended to attach two components to each other during each flip-chip bonding operation. Thus, standard flip-chip machines are only capable of performing a single two-component alignment operation at a time and are not designed to perform the two or more simultaneous alignment operations required for the proper alignment and assembly of multiple components. The machines' design does not permit the simultaneous bonding of two or more components to a single substrate or chip carrier, an operation which is required, for example, when connecting multiple thin film jumper connectors to a substrate. One possible solution to this problem would be to use a custom bonding machine which has sufficient degrees of freedom to permit the simultaneous alignment of more than one component to a substrate. The disadvantage of this approach is the time and cost required to design and manufacture such a machine. Since standard flip-chip bonding machines are already installed at most device manufacturers, it would be more efficient to use such a machine if possible.
What is desired is a method of bonding multiple components to a substrate at the same time, while maintaining a desired alignment between the components and between the components and the substrate. It is further desired that the apparatus and method utilize a standard flip-chip bonding apparatus to perform the bonding operation.
SUMMARY OF THE INVENTION
The present invention is directed to a method of assembling more than one thin film jumper connector to a substrate at the same time, as part of a process of manufacturing a multi-chip module or other device in which multiple components are bonded to a chip carrier or other substrate. In accordance with the invention, an alignment plate is positioned on the chuck of a standard flip-chip bonding machine. The thin film jumper connectors are placed on the alignment plate in a face-up position. Precise alignment between alignment marks on the connectors and alignment marks on the plate is achieved using the machine's moveable platform and split-field viewer. The jumper connectors are held to the alignment plate by a force supplied by the vacuum system of the flip-chip bonder, with the force being transmitted to the connectors through vacuum holes in the alignment plate. The plate's alignment marks are positioned so that when they are aligned with the corresponding marks on the connectors, the bonding pads or solder bumps on the connectors are correctly aligned to the pads on the substrate(s) which will be bonded to the connectors. A substrate or chip carrier to be connected to the jumper connectors is then placed on the moveable platform in a face-up position and rotated to a face-down position. The substrate is moved into a coarse position over the thin film connectors, precisely aligned with the split-field viewer, and then lowered into physical contact with the pads or solder bumps of the connectors.
The entire assembly, including the alignment plate, is then placed in a reflow furnace or otherwise heated to cause the solder bumps on the thin film connector pads to make good electrical contact with the bonding pads on the substrate. Depending on the thermal relationships between the integrated circuit chips, the thin film connectors, and the substrate, the chips may be connected to the substrate either before or after the thin film jumper connectors are bonded to the substrate. If the chips are connected prior to the assembly of the thin film connectors, then a chip cavity is formed in the alignment plate to prevent contact between the chips and the bonding apparatus during the thin film connector bonding. In such a situation, the melting point of the solder bumps used to bond the chip(s) to the substrate should be substantially higher than that of the bumps used to bond the thin film connectors to the substrate.
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Boucher Patricia R.
Horine David A.
Love David G.
Coudert Brothers
Dinh Son T.
Fujitsu Limited
Pyonin Adam
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