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Wave Assisted Method for Decapsulating Integrated Circuits

IP.com Disclosure Number: IPCOM000235033D
Publication Date: 2014-Feb-25
Document File: 2 page(s) / 186K

Publishing Venue

The IP.com Prior Art Database

Abstract

Currently, copper wire bonded devices in plastic package are decapsulated using a mixture of fuming nitric acid and fuming sulfuric acid. The usual method to accelerate chemical reaction is to increase the temperature. This paper describes the use of high frequency agitation using waves to accelerate the chemical reaction with mold compound while resulting in good preservation of the copper wire.

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Wave Assisted Method for Decapsulating Integrated Circuits

Abstract

Currently, copper wire bonded devices in plastic package are decapsulated using a mixture of fuming nitric acid and fuming sulfuric acid. The usual method to accelerate chemical reaction is to increase the temperature. This paper describes the use of high frequency agitation using waves to accelerate the chemical reaction with mold compound while resulting in good preservation of the copper wire.

Introduction

With the increasing price of gold, the industry is seeking an alternative to replace gold wire bonds with copper for its better electrical and thermal conductivity as well as its relatively lower cost. However, the primary challenge comes when decapsulating the copper wire bonded devices for failure analysis.

Generally, in acid decapsulation, nitric acid and sulfuric acid are applied to etch (remove) the mold compound. The usual methods of decapsulation practiced widely in the industry are either using the manual dropper/hotplate method or using a jet etcher.

In this paper, waves are used to agitate the acid and unit to accelerate the mold compound etch rate. The frequency of the waves may extend from acoustic to ultrasonic and mega-sonic frequencies, applied for various acid mixture ratios and temperature.

Method

Mold compound mainly contains SiO2 fillers and mold resin which binds the composite. During any kind of plastic package decapsulation, only the resin is etched but not the SiO2 fillers. This is because chemicals which etch the SiO2 fillers will also etch the inter-dielectric layers of the die.

The mold compound surface that needs to be etched should facing downwards. Sonic waves is then applied to the unit and/or solution for agitation, which allows ...