Abstract
Pressure sensitive adhesives (PSAs) are utilized for temporary applications since bonding and debonding are determined by the adhesive-substrate interface and the mechanical and rheological properties of the PSA. Moreover, a wide variety of basic materials allows for proper adjustment of the adhesive properties (tack, peel adhesion, cohesion). Where the adjustment of the adhesive's chemical composition is not efficient enough to provide easy and clean removability in the end of the application, release functions can be incorporated into the adhesive system. The adhesive strength is reduced upon the action of external triggers such as UV-irradiation, heat, the use of electric currents or magnetic fields. Thereby, debonding may follow various mechanisms, including phase changes, chemical reactions, crosslinking and volumetric expansion. Furthermore, electrostatic attraction, polarization, shape memory effects and mechanical adhesion can be employed. This review summarizes the most important properties of PSAs and provides an overview of well-proven as well as new approaches for “debonding-on-demand” adhesive systems. In addition, the article describes proposed and already implemented applications of the presented adhesive systems in the microelectronic industry, the automotive sector and the healthcare field.
| Titel in Übersetzung | Klebstoffe für Entklebung nach Bedarf: Auslösemechanismen und typische Anwendungen |
|---|---|
| Originalsprache | Englisch |
| Aufsatznummer | 102585 |
| Seitenumfang | 36 |
| Fachzeitschrift | International Journal of Adhesion and Adhesives |
| Jahrgang | 99.2020 |
| Ausgabenummer | June |
| DOIs | |
| Publikationsstatus | Veröffentlicht - 5 März 2020 |
Bibliographische Notiz
Funding Information:The research work of this paper was performed at the Polymer Competence Center Leoben GmbH (PCCL, Austria) within the framework of the COMET-program of the Federal Ministry for Transport, Innovation and Technology and the Federal Ministry for Digital and Economic Affairs, with contributions by the Chair in Chemistry of Polymeric Materials (Montanuniversitaet Leoben, Austria). The PCCL is funded by the Austrian Government and the State Governments of Styria , Lower Austria and Upper Austria .
Funding Information:
In both approaches, sticky tapes are used to support the brittle wafer throughout these mechanically challenging procedures [38,57]. Firstly, the wafer is attached to a backgrinding tape and a support carrier (silicon, glass, ceramics or polymer), which provide stability during coarse and fine grinding [38,66,91], where the thickness of the wafer is reduced by mechanical abrasion with a diamond bonded wheel (see Fig. 23a) [38,92]. Furthermore, the front side of the wafer is protected from the process chemistry in the following post grinding treatment, where wet or plasma etching as well as chemical and mechanical polishing or dry polishing are applied to remove roughness and damage and to relieve stresses from the silicon wafer [38,91,92]. Before removing the backgrinding support, the thinned wafer is transferred to a dicing tape, which is attached to the backside of the wafer and mounted to a steel or plastic frame (see Fig. 23b) [91?93]. In the dicing process the wafer is converted into a multitude of single components (dies) by a blade with diamond abrasives (see Fig. 23c). Alternatively, lasers or plasmas can be used to dice the silicon substrate [38, 91?93]. The single dies are further supported by the dicing tape system during transportation and finally ejected for packaging assembly. Therefore, the tape is held down by a vacuum tool. Needles eject the dies, which are picked up by vacuum chucks (see Fig. 23d) [38] and transferred to microelectronic devices, where the dies are bond permanently by the use of liquid adhesives or attach films [91]. In the dicing by thinning process, the wafers are attached to a support carrier by release tapes after preparation of trenches on the front side (see Fig. 24) [38,91].Most commonly, UV-sensitive adhesive tapes are used because they provide high adhesive strength to reliably hold the wafer during thinning and cutting and simultaneously allow for easy and clean removability on demand when the dies are picked up and transferred to the assembly step. Furthermore, UV-release tapes are preferred over thermal release tapes since they can be used throughout the whole production process, including high temperature steps [38,95]. Typically, photo-curable tapes are based on acrylic PSAs [52,92], which reduce their adhesive strength upon UV-irradiation and the related crosslinking or the formation of (semi-)IPNs [50,54,60]. Another route considers the preparation of photo-cleavable adhesives for flip-bonding applications by the incorporation of o-nitrobenzyl ester units into an adhesive system [57]. Moreover, side chain crystallizable polymers may be employed in wafer supporting systems to reduce the adhesive strength by cooling below melting transition temperature (~35 ?C) [79].The research work of this paper was performed at the Polymer Competence Center Leoben GmbH (PCCL, Austria) within the framework of the COMET-program of the Federal Ministry for Transport, Innovation and Technology and the Federal Ministry for Digital and Economic Affairs, with contributions by the Chair in Chemistry of Polymeric Materials (Montanuniversitaet Leoben, Austria). The PCCL is funded by the Austrian Government and the State Governments of Styria, Lower Austria and Upper Austria.
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© 2020
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