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Double Sided Flip-Chip Electronic Packaging

IP.com Disclosure Number: IPCOM000101498D
Publication Date: 2005-Mar-16
Document File: 4 page(s) / 130K

Publishing Venue

The IP.com Prior Art Database

Abstract

Flip chip technology is a valuable electronic packaging technique that provides a high-density electrical connection without the need for wire bonding. Traditionally, the wire bonding technique provides the ability to attach a silicon die to only one side of a substrate. For systems with severe space constraints, a double-sided flip-chip technology would be desirable, but due to curing temperature constraints the difficulty in attaching both dies simultaneously may cause the solder from the first attachment to re-flow when the second die is attached. Due to the tight tolerance requirements in space limiting situations, fixtures that are used to hold both dies simultaneously are impractical, or using conductive epoxy for one die does not provide sufficient bonding strength without an under-fill, also bonding two conventional flip-chip assemblies together requires more space and adds interconnects that are not necessary with double sided flip-chip technology. What is needed is a flip-chip solder re-flow process technique for high-density electronic packaging. The present disclosure describes such a technique in which each step of the fabrication process is presented.

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Double Sided Flip-Chip Electronic Packaging

Background

                    Flip chip technology is the direct electrical connection of face-down, i.e. flipped, electronic components onto substrates, circuit boards, carriers, by means of conductive bumps on the chip bonding pads.  In contrast, wire bonding, the older technology which flip chip is replacing, uses face-up chips with a wire connection to each pad.

                    Flip chip assembled components are predominantly semiconductor devices; however components such as passive filters, detector arrays and similar devices are also beginning to be used in flip chip form.  Flip chip components are directly attached to the substrate, board, or carrier by the conductive bumps.

                    Flip chip technology is a valuable electronic packaging technique that provides a high-density electrical connection without the need for wire bonding.  Traditionally, the wire bonding technique provides the ability to attach a silicon die to only one side of a substrate.  For systems with severe space constraints, a double-sided flip-chip technology would be desirable, but due to curing temperature constraints the difficulty in attaching both dies simultaneously may cause the solder from the first attachment to re-flow when the second die is attached.  Due to the tight tolerance requirements in space limiting situations, fixtures that are used to hold both dies simultaneously are impractical, or using conductive epoxy for one die does not provide sufficient bonding strength without an under-fill, also bonding two conventional flip-chip assemblies together requires more space and adds interconnects that are not necessary with double sided flip-chip technology.

                    What is needed is a flip-chip solder re-flow process technique for high-density electronic packaging.  The present disclosure describes such a technique in which each step of the fabrication process is presented.

Description

                    The flip chip fabrication process described in the present disclosure relies on the concept that non-conductive epoxy cures at a lower temperature as compared to solder re-flow.  Thus, one die is mechanically attached to the substrate using non-conductive epoxy with solder paste screen-printed on the substrate.  The second die is then attached using a conventional method, and during the solder re-fl...