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Recent Technology Advancements in Debondable Adhesives

Posted on 4/4/2016 7:10:53 PM By Deb Bhattacharjee
  

Adhesive are generally used to bond substrates with similar and different surface energies quickly and reliably.  Yet, in many instances, it is desirable to separate the surfaces without difficulty such that the surfaces could be repositioned or recycled.

Would it not be nice to separate the two layers with ease, after the product has served its purpose? How about a debondable adhesive for end of life vehicles allowing easy recycling of bonded plastics?

During the last decade or so, there has been a significant escalation of demand and the need for debonding technologies as evidenced by new product introductions, webinars, publications and patent applications.  The industry has responded to this demand by introducing an additive in the designed adhesive and the debonding is triggered by an external energy source like heat (thermal and induction), electrical, light, or magnetic flux.  It is important to ensure that the mechanical properties and adhesive strength, upon incorporation of any additive, are not compromised.  As anticipated, the selection of right debonding technology will depend on application needs and constraints.  For example, heat sensitive plastics are often unable to withstand high temperature. In addition, there are practical implications with environmental concerns regarding the use of energy sources and by-products.  However, the same technology would not be applicable to all debonding applications.  Thus, it is necessary to think holistically about polymer design and external energy sources. The preferred technology should be easy to apply, environmentally friendly, cost effective and should not leave any adhesive residue on the substrate.

Researchers at Rescoll Research Company, France have developed innovative, patent protected (e.g. WO2011080477A1, WO2005028583A1), interfacial debonding adhesive technologies (INDAR™ Inside) which allow dismantling of structural assemblies with no damage to the substrates and leaving a clean surface after deactivation.  Maxine Olive from Rescoll has also given short course named “Debonding on demand structural adhesives: Strategies & Future opportunities”, with information on market demand and emphasis on technology strategies. Similarly, a patent application by Sika (WO2010146144A3) details the incorporation of carboxylic acid hydrazides in polyurethane adhesives, where the gases coming out of the decomposition of hydrazides weaken the adhesion strength.

Researchers at Fraunhofer Institute of Manufacturing Engineering & Applied Materials Research IFAM in Bremen, Germany in a joint project with Degussa AG, incorporated a mixture of supermagnetic particles (iron oxide embedded in nanoparticles of SiO₂) powder into adhesive, followed by exposing the adhesive bond to a desired combination of high frequency alternating magnetic field and high intensity for facile debonding (Nanowerk News, July 25, 2006.)

Exonera, a spin off from Stora Enso’s research into Controlled Delamination Materials (CDM), and acting as European distributor of EIC labs electrically debondable products, ElectRelease™, have introduced technologies where two substrates are bonded together with an ion conductive adhesive and an external power source is connected to form an electric circuit.  Electrochemical reactions at the interfaces weaken the adhesive allowing the release of the substrates.

Henkel introduced an water-debondable epoxy adhesive, which provides excellent bond strength to both silicon and metal-mounting substrates used during the ingot sawing process, yet breaks down easily on exposure to hot air eliminating corrosive debonding solutions (SpcialChem Industry News, August 18, 2011).

One of the key challenges in Temporary Wafer Bonding (TWB) is high yield debonding at low forces.  David Fleming, et. al. from The Dow Chemical Company presented a paper entitled “Thin wafer handling using mechanical- or laser- Debondable Temporary Adhesives”, at the IMAPS 11th International Conference and Exhibition on Device Packaging, illustrating debonding including mechanical or laser ablation modes (requiring bonding force as low as 0.6N, though it could be more expensive to install and maintain).

In a recent patent (US8592034B2) by 3M, a debondable adhesive article comprising a shape memory polymer backing having a temporary, deformed shape and a pattern of latent projections and an amorphous pressure sensitive adhesive layer coated on patterned surface of the shape memory polymer backing were described.   On exposure to heat, the backing layer recovers to a permanent shape, the projections extend from the first surface of the adhesive article and weaken the bond with the substrate.

Don’t miss the upcoming presentation at the ASC Spring Convention & EXPO by Professor Scott Phillips from Pennsylvania State University on recent advances in adhesives technology that undergo rapid and complete debonding through head to tail depolymerization, in response to specific applied chemical and/or physical signals (www.psu.edu/dept/Phillipsgroup/).