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Electronic Circuits-Preserving Technique for Decapsulating Plastic Packages

IP.com Disclosure Number: IPCOM000040560D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Fenech, A: AUTHOR

Abstract

Because of their low cost and ease of use, plastic materials, such as epoxy resins, are increasingly employed for encapsulating integrated circuits. Decapsulating the plastic packages, without damaging the circuits embedded therein, is necessary whenever it is desired to access the circuits for failure analysis thereof. Most of the conventional techniques for decapsulating plastic packages call for the use of chemical, plastic-etching agents, such as nitric acid. The so-called "jet etch" technique is one of these. Not only does it require large volumes of nitric acid but, further, the nitric acid must be at a high temperature (about 250oC). As a result, the "jet etch" method is costly and its use involves operator safety problems.

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Electronic Circuits-Preserving Technique for Decapsulating Plastic Packages

Because of their low cost and ease of use, plastic materials, such as epoxy resins, are increasingly employed for encapsulating integrated circuits. Decapsulating the plastic packages, without damaging the circuits embedded therein, is necessary whenever it is desired to access the circuits for failure analysis thereof. Most of the conventional techniques for decapsulating plastic packages call for the use of chemical, plastic-etching agents, such as nitric acid. The so-called "jet etch" technique is one of these. Not only does it require large volumes of nitric acid but, further, the nitric acid must be at a high temperature (about 250oC). As a result, the "jet etch" method is costly and its use involves operator safety problems. The present technique, although still calling for the use of nitric acid to etch the plastic package and expose the chip, overcomes the disadvantages of the conventional techniques by using only a small volume of moderately hot nitric acid to etch the desired area, while the remainder of the component is shielded from the etching agent. According to the present technique, a container made of TEFLON*, whose dimensions are compatible with those of the chip to be exposed, is first fabricated. An opening, whose shape matches that of the area to be etched in the package, is made through the bottom wall of the container. Then, the zone of the upper surface of the package which faces the chip is abraded or milled in a direction parallel to the chip and to a small depth in order to reduce the quantity of plastic material to be removed during the subsequent chemical etching operation. Such a milling or abrading operation limits the undesired eff...