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Article
Publication date: 26 June 2009

Kati Kokko, Hanna Harjunpää, Pekka Heino and Minna Kellomäki

The purpose of this paper is to investigate the influence of composite coating structure on the reliability of adhesive flip chip joints. The need for conformal coating is…

297

Abstract

Purpose

The purpose of this paper is to investigate the influence of composite coating structure on the reliability of adhesive flip chip joints. The need for conformal coating is considered, especially for medical applications, and medical sterilization is also considered.

Design/methodology/approach

Two test lots were assembled and one of them was sterilized using gamma sterilization. Both test lots were coated first with epoxy and then with Parylene C, resulting in a composite coating structure. The reliability was studied using a constant humidity test and the failure analysis was performed with cross‐sections and scanning electron microscopy analysis. These results were compared to earlier research results on conformal coatings.

Findings

The reliability of both test lots proved to be good. The composite coating structure shields the joints from humidity and improves the reliability compared to non‐coated test samples. When the conformal coating was compared to the pure Parylene C coated test lot, the reliability was almost the same. This leads to the conclusion that the epoxy layer in the composite coating structure has no value when long‐term reliability is considered. Gamma sterilization does not greatly affect reliability. The epoxy coating under the Parylene C layer cracked during reliability testing.

Originality/value

The paper shows the influence of composite coating structure on the reliability of adhesive flip chip joints, particularly important in medical applications.

Details

Soldering & Surface Mount Technology, vol. 21 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 18 September 2009

Kati Kokko, Hanna Harjunpää, Anna‐Maija Haltia, Pekka Heino and Minna Kellomäki

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…

426

Abstract

Purpose

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 85°C 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.

Details

Soldering & Surface Mount Technology, vol. 21 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

Available. Content available
Article
Publication date: 26 June 2009

Martin Goosey

452

Abstract

Details

Soldering & Surface Mount Technology, vol. 21 no. 3
Type: Research Article
ISSN: 0954-0911

Available. Content available
Article
Publication date: 18 September 2009

Martin Goosey

249

Abstract

Details

Soldering & Surface Mount Technology, vol. 21 no. 4
Type: Research Article
ISSN: 0954-0911

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