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Environmentally Friendly Structure to Handling Ultra thin Die

IP.com Disclosure Number: IPCOM000004591D
Original Publication Date: 2001-Feb-23
Included in the Prior Art Database: 2001-Feb-23
Document File: 3 page(s) / 600K

Publishing Venue

Motorola

Related People

Steve Schiefers: AUTHOR [+4]

Abstract

Lower semiconductor package thickness and less weight are among the significant benefits of using ultra-thin die. The methodology used today to assemble circuits with ultra-thin die is both time and labor-intensive. Moreover, it uses solvents that are not environmentally preferred. A high-volume and environmentally preferred technique for assembling circuits with ultra-thin die is proposed.

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Environmentally Friendly Structure to Handling Ultra thin Die

By Steve Schiefers, Daniel Gamota, Krishna Kalyanasundaram, and Andrew Skipor

SUMMARY

Lower semiconductor package thickness and less weight are among the significant benefits of using ultra-thin die. The methodology used today to assemble circuits with ultra-thin die is both time and labor-intensive. Moreover, it uses solvents that are not environmentally preferred. A high-volume and environmentally preferred technique for assembling circuits with ultra-thin die is proposed.

PROBLEM

Reduction in wafer thickness has increased the opportunities for miniaturization of portable electronics. Ultra-thin die provide the same functionality as standard thick die, while allowing for reduction of semiconductor package thickness and weight. The current methodology to handle ultra-thin die consists of attaching a thick piece of silicon to the backside of the fragile ultra-thin die that acts as a planarizer and as a rigidizer. The ultra-thin die with the rigidizer is attached to the substrate using a standard pick-and-place machine. The silicon rigidizer is removed using one of two methods: by applying heat and torque (Fig. 1a) or by immersing the assembled substrate in a solvent bath (Fig. 1b). Both methodologies are slow and do not meet the cycle time demand that is typical of high-volume manufacturing. Further, these methodologies require additional equipment and manufacturing floor space. This, in turn, requires modification of a standard SMT assembly line resulting in increased cost. Additionally, the use of most solvents is undesirable due to the presence of volatile organic compounds (VOC).

SOLUTION

A porous rigidizer is coated with a water-soluble adhesive at the wafer fab. It is then aligned and adhered to the ultra-thin wafer that is supported on an industry grade wafer support blue tape. This forms an ultra-thin die-porous-rigidizer composite. This composite is then diced and shipped to the final manufacturing facility.

During the assembly of the ultra-thin die, the standard pick and place machine picks the ultra-thin die-porous composite from the blue tape, aligns the composite to the features on the substrate using either the bumps or the fidiucial marks on the ultra-thin die, and then places the composite on the substrate that is laminated with anisotropic conductive film (ACF). The interconnections are made using a thermo-compression bonder. In the next step, a liquid is applied to the porous rigidizer to achieve a localized saturation region, which dissolves the water-soluble adhesive and in turn, releases the rigidizer from the ultra-thin die. This leaves the ultra-thin die attached to the circuit.

Fig. 1. Current Method to Assemble Ultra-thin Die

Fig 2. Embodiment of thin die attached to a rigid backing using a wafer-soluble adhesive

Fig 3. Process flow for assembling ultra-thin die onto circuit boards using an environmentally friendly structure