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|Non-Abrasive Removal of Zero Shrink LTCC Constraint Layer|
|Keywords: LTCC, Zero-Shrink, Release Tape|
|Low Temperature Cofired Ceramics (LTCCs) are widely used for robust, high density packaging. While it is common to create smaller (usually from 2”x2” to 5”x5”) LTCC boards for development parts, using smaller panel sizes in production can be costly due to wasted area on the outside of the panel. To reduce costs, LTCC manufacturers may create larger panels and / or use zero-shrink LTCC materials. Zero-shrink LTCCs allow for higher part density per panel by inhibiting shrinkage in the x-y direction to under 0.5 percent; all of the shrinkage occurs in the z direction. Another advantage of zero-shrink LTCCs is better alignment during firing of larger panels because the panel stays rigid during firing. There are three techniques for creating zero-shrink LTCCs. The technique discussed in this paper is known as Pressureless-Assisted Sintering (PLAS). In this method, a release tape is laminated to the top and bottom of the green substrate. The release tape constrains the LTCC during sintering, but does not sinter. After firing, the body consists of the LTCC substrate and the baked out release tape, which is similar to a compressed powder coating. PLAS requires an extra processing step from standard LTCC – release tape removal. However, it can be used with some already-existing LTCC systems; for example DuPont 951RT (release tape) can be used with the DuPont 951 system. Typical release tape removal methods include scrubbing with a brillo-type sponge and bead / sand blasting. While both methods are effective at removing the baked out tape, they are abrasive and difficult to control. Another method for removing release tape has been discovered using an industrial detergent and an ultrasonic bath. This method does not harm the LTCC substrate or the surface metallization. The Kansas City Plant is operated for the United States Department of Energy under Contract No. DE-ACO4-01AL66850.|
|Cristina Lopez, Microelectronics Fabrication Engineer
Kansas City, MO