Interfacial reliability between hot-melt polyamides resin and textile for wearable electronics application Soon-Wan Chung ⇑ , Hyun-Tae Kim Mechatronics & Manufacturing Technology Center, Samsung Electronics, Co., Ltd., 416, Maetan-3Dong, Yeongtong-Gu, Suwon-City, Gyeonggi-Do 443-742, Republic of Korea article info Article history: Received 2 January 2010 Received in revised form 28 January 2012 Accepted 21 February 2012 Available online 17 March 2012 abstract The interfacial reliability between hot-melt polyamides resin and textile is studied to investigate whether hot-melt polyamides resin is useful as an encapsulation material of wearable electronic devices. Four kinds of hot-melt polyamides resins and six kinds of textile fabrics are used, and the test sample is fabricated by molding polyamides resin on top of textile. To confirm the mechanical reliability between polyamides resin and textile under water washing and dry cleaning condition, the adhesion strength is measured by 90° peel test not only at initial state but also after exposing the sample to moisture and heat. As a result, it can be seen after high temperature and humidity test that peel strength is degraded and fracture mode can be changed from adhesive failure to cohesive failure according to textile fabric. Also, the optimal combination of polyamides resin and textile for better peel strength is obtained. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Recently, electronic devices are getting smaller and thinner to satisfy consumers’ needs for ease of handling and mobility. Fur- thermore, the miniature electronic devices are trying to be attached to clothing to make it more portable. Methods to develop these wearable electronics such as electronics on textile and elec- tronic textile have been studied [1–10]. For electronics on textile, electrical circuit was constructed on textile. For example, Printed Circuit Boards (PCBs) were laminated on textile and connected together by embroidering conductive yarns [1,2]. Instead of embroidering conductive yarns, a Cu patterned polyurethane film was laminated onto textile [3]. Electrically conductive silver ink patterns were printed by screen printing method on fabrics and the electrical and mechanical properties were characterized by various tests [4,5]. Body Area Network (BAN) was also researched to connect electrical circuits on textile [6]. For electronic textile, textile weaved with conductive yarn [7] and textile which contains a fiber transistor [8] have been investigated. To develop wearable electronics using these methods, electrical components such as microchip or battery should be attached to textile and connected together. These electrical components and circuits should be protected from exterior environment in use such as impact, bending and moisture. To satisfy these needs, they were encapsulated by polymer material [1–3,6,9] and the electrical prop- erty of the encapsulated circuits on textile has been evaluated under thermal cycling and washing test [1,10]. Specifically, an Electrical Mold Compound (EMC) and a hot-melt polyamides resin are used as an encapsulation material. An EMC is normally used for microchip packaging. A hot-melt polyamides resin is used as a housing material for an electronic device such as USB memory stick and cellular phone battery and also used as an adhesive for bonding a zipper or label to clothes [11]. Fig. 1 shows electrical circuit on textile which is encapsulated by a hot-melt polyamides resin. A hot-melt polyamides resin is adequate for an encapsulation material of clothing because it is soft and flexible compared to an EMC and also has enough stiffness to resist bending force in use. However, it is known that adhesion between hot-melt polyamides resin and metal is weak under moisture and heat condition [12]. Therefore, in order to use a hot-melt polyamides resin as an encap- sulation material of clothing, adhesion reliability at the interface between hot-melt polyamides resin and textile should be inspected under moisture and heat condition. It is because wearable electron- ics are frequently exposed to moisture and heat such as water washing and dry cleaning. However, there are little literatures related to this issue, so far. In this paper, an interfacial reliability between hot-melt polyamides resin and textile was investigated under moisture and heat condition. Four kinds of hot-melt polya- mides resins and six kinds of textiles were prepared and a peel test [13,14] was performed to measure adhesion strength. 2. Experimental details 2.1. Materials 2.1.1. Encapsulation Four hot-melt polyamides resins from two companies were used as an encapsulation material. Two polyamides resins in each 0026-2714/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.microrel.2012.02.014 ⇑ Corresponding author. Tel.: +82 31 200 5649; fax: +82 31 200 2859. E-mail address: soon.chung@samsung.com (S.-W. Chung). Microelectronics Reliability 52 (2012) 1501–1510 Contents lists available at SciVerse ScienceDirect Microelectronics Reliability journal homepage: www.elsevier.com/locate/microrel