Modified single cantilever adhesion test for EMC/PSR interface in thin semiconductor packages Kenny Mahan a , Byung Kim a , Bulong Wu a , Bongtae Han a, ⁎, Ilho Kim b , Hojeong Moon b , Young Nam Hwang c a Mechanical Engineering Department, University of Maryland, College Park, MD 20742, USA b Package Development Team, Semiconductor R&D Center, Samsung Electronics, 1, Samsungjeonja-ro, Hwaseong-si, Gyeonggi-do, Korea c Measurement and Analysis group, Corporate R&D Institute, Samsung Electro-Mechanics Co., 150, Maeyoung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, Korea abstract article info Article history: Received 2 April 2016 Received in revised form 26 May 2016 Accepted 26 May 2016 Available online 29 June 2016 We propose and implement an adhesion test configuration called “modified single cantilever adhesion test” (M- SCAT) that can be employed to determine the adhesion strength of epoxy molding compound (EMC) and photo solder resist (PSR) interface in thin semiconductor packages. The proposed M-SCAT method is optimal for quick and quantitative in-situ testing of the interface with strong adhesion as sample preparation and testing are sim- ple while maintaining a low mode mixity at the crack tip. Detailed sample preparation and experimental testing to determine the critical load required for delamination are presented. A numerical procedure is followed to as- sess the stress and strain fields around the crack tip at the point of delamination, thus allowing for the J-integral method to be employed to determine the critical energy release rate. The proposed approach is carried out for two different EMC/PSR interfaces. The results show excellent repeatability, which allows for the test method to be used effectively to select the most ideal material set for given applications. © 2016 Elsevier Ltd. All rights reserved. Keywords: Adhesion strength Single cantilever adhesion test Energy release rate J-integral EMC Epoxy molding compound Photo solder resist PSR 1. Introduction With the advancement of thin-profile designs, in-situ adhesion strength testing of products directly off of manufacturing lines is a crit- ical challenge. If potential delamination failures due to inadequate adhe- sion strength can be detected early in the design cycle, unreliable designs can be ruled out leading to quicker product turn around. This is especially important in the fast-pace environment of the electronic packaging industry where quick and effective adhesion strength testing methods are required. One such interface that must address these challenges is the high ad- hesion strength interface found between epoxy molding compound (EMC) and photo solder resist (PSR). The interface is shown in Fig. 1, where the PSR is sandwiched between the EMC and the printed circuit board (PCB) substrate. The EMC/PSR interface can delaminate during manufacturing processes and/or operating conditions. Thus, it is critical to assess the adhesion strength of any newly proposed material combi- nations to assure the adhesion strength of selected material sets is strong enough for the intended product application. The adhesion strength is often characterized using the energy re- lease rate of the interface [1]. The energy release rate, G, is a measure of the energy available for an increment of crack extension. When a specimen with an interfacial crack is loaded, energy is stored inside until a critical loading state is reached. At this point, the crack propa- gates, and energy is released from the system while creating a new sur- face area along the interface. For this case, G can be evaluated directly from a typical load vs. displacement graph either analytically or through the aid of numerical methods. Two such methods are the J-integral method [1–6] and the virtual crack closure technique (VCCT) method [2,7–9]. The second critical property to consider is the mode mixity at the crack tip. The mode mixity can be defined as the ratio of in plane shear (mode II) to opening (mode I) loading at the crack tip [1,7,8,10, 11]: tan -1 Ψ ¼ ffiffiffiffiffi G II G I s ð1Þ where G I and G II represent the mode I and II energy release rate contri- bution at the interface, respectively. The energy release rate is known to increase with respect to the mode mixity due to the increased presence of in-plane shear loading; when comparing different material sets, it is important to compare them at similar mode mixity values [1,7,8,10, 11]. The larger the mode mixity, the more susceptible the interfacial crack will be to kinking out of the interface [12–15]. Additionally, Microelectronics Reliability 63 (2016) 134–141 ⁎ Corresponding author. E-mail address: [email protected] (B. Han). http://dx.doi.org/10.1016/j.microrel.2016.05.015 0026-2714/© 2016 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Microelectronics Reliability journal homepage: www.elsevier.com/locate/mr
Modified single cantilever adhesion test for EMC/PSR interface in thin semiconductor packages
May 30, 2023
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