Effects of conformal coating on anisotropically conductive adhesive joints; a medical perspective

Abstract

If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation. AbstractPurpose -The purpose of this paper is to study epoxy and parylene C-coated samples. These coatings are used to protect the electronic devices from harsh environments. The effect of these conformal coatings on electronics reliability is considered. Design/methodology/approach -Epoxy coating is applied using dip coating and parylene C is applied with the vapour deposition polymerisation method. Test chip used is joined using flip-chip technology and an anisotropically conductive adhesive. Reliability of the test samples is evaluated in a constant humidity test, where test conditions are 858C and 85%RH. The test lasts 4,000 h. Failure analysis is carried out by cross-sectioning failed samples and using scanning electron microscopy for closer analysis. Findings -The results show variation in the reliability of adhesive joints with different conformal coating materials. Failure analysis highlights explicit failure mechanisms. Adhesion testing is also carried out on the test samples after constant humidity testing. The results of these reliability tests indicate clearly that parylene C is a more reliable choice of conformal coating than epoxy. Originality/value -The paper shows the influence of certain conformal coatings on the reliability of adhesive flip-chip joints. In medical applications, reliability plays an important role.

Composite coating structure in an implantable electronic device

“…These test lots were also completely comparable with test lots EPC and EPCS. The results from test lots NC, EC and PC have been published elsewhere (Kokko et al , 2009b). In summary, all the test lots are collected in Table III.…”

“…This consisted of a sandwich structure with a layer of epoxy and another of Parylene C. These test lots were compared to test lots with either only epoxy or Parylene C conformal coating or no coating at all. These test lots were previously investigated in more detail and here they serve as references (Kokko et al , 2009a, b). Reliability was studied using a constant humidity test where the test conditions were 85°C and 85%RH.…”

Effects of failure criteria on the constant humidity test results

“…The daisy chain resistance was used to monitor the failing of the devices during the test and real-time measurements were carried out during testing. The reliability results were analyzed using three different failure criteria them being 10% testing, it has been discovered that during failing the resistance produces peaks prior to total failure [7]. Due to this the peaks were ignored in one of the failure criterion.…”