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Thermoplastic Adhesives for Chip Scale Package (CSP) Applications

IP.com Disclosure Number: IPCOM000009591D
Publication Date: 2002-Sep-04
Document File: 2 page(s) / 48K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for using a die attach (DA) adhesive at the wafer or die level. Benefits include reducing the amount of bending or warping during die attach, wire bonding and succeeding processes.

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Thermoplastic Adhesives for Chip Scale Package (CSP) Applications

Disclosed is a method for using a die attach (DA) adhesive at the wafer or die level. Benefits include reducing the amount of bending or warping during die attach, wire bonding and succeeding processes.

Background

Thermosetting materials are common in semiconductor applications. These are the materials typically used at the die attach process to secure the die rigidly to the substrate so that it does not move during wire bonding and succeeding processes. These materials are resistant to high temperatures, and do not decompose at elevated temperatures (i.e. solder reflow at 260°C with Pb-free materials). In chip-scale packages (CSPs) with package thicknesses 1.0mm and less, there is severe bending and warping due to the reduced thickness of the package and extreme CTE mismatches between the different materials used. Typical molding compounds have a CTE of 10ppm and BT susbtrates 24ppm while silicon exhibits a 2.6ppm CTE.� With the move towards a thinner die (<5 mils) in future packages, the die will experience greater amounts of stresses in these packages.

General Description

DA adhesive can be applied either at the wafer or die level. At the wafer level, dry adhesive film in tape form is applied on the wafer backside after back grinding. The dry film is cut to size with the die during singulation, before attaching the die to a substrate. Also, it can be pre-cut to size via a punch-and-attach process, then applied to the substrate before the die is attached to the substrate. With wet DA adhesives, the adhesive is applied as a liquid on to the substrate. In both dry and wet DA adhesive examples, the substrate/adhesive/die sub-assembly is taken through a thermal process to fully cure the adhesive.

The disclosed method eliminates stresses introduced during the thermal proc...