SMTA China Conference Proceedings

The Study of Cure Percentage Determination for Anisotropic Conductive Film by FTIR Method

Authors: Henley Zhou, Ivan Lin, Xin Ling, Jumbo Huang, Arnel Camacho, Ranilo Aranda, Jinsuo Guo, RSivam VRajoo, and Mike Doiron
Company: Flex
Date Published: 8/28/2017   Conference: SMTA China

Abstract: In today's world, electronic products are almost everywhere. People become used to the idea of intelligent devices and applications that make their life easier. Example of this devices are mobile phones, MP4 players, tablets, smart watch and wearables that has LCD displays for easy interaction. With these electronic products becoming more and more slim, thin, lighter, and having advance functions, the need for a thin but reliable mechanical and electrical connection of these display to the driver electronics is very important. Normally, these LCDs are connected using an FPC which is then attach to a PCB or another substrate. Actually, there are a couple of different methods that can be used to connect the FPC such as hotbar, Zif connector and the use of ACF (Anisotropic Conductive Film). Though ACF is already a matured technology, there are still some issues that arise during the assemblies like smashed conductive particle and a low peel strength which can be associated to a contaminated FPC pad or a not fully cured adhesive affecting the reliability of the final product.

One of the widely used method for curing behavior analysis specially for raw adhesive material is the Differential Scanning Calorimetry (DSC) because of its experimental convenience and speed of operation. But this method cannot be used to determine the cure percentage of the ACF once it was assembled because it is impossible to get enough sample weight (normally more than 3 mg) for analysis. Another way to indirectly identify the cure percentage is by peel test. This method will give a result by identifying which parameter will have the highest peel strength. But using this method is also sometimes confusing especially if we get some outliers resulting to a big variance that impact the determination of the best setup.

In this paper, we will be using Fourier Transform Infrared Spectroscopy (FT-IR) method to determine the cure percentage by calculating reaction ratio of processed ACF. The accuracy of this method will then be verified by comparing the result between FT-IR, DSC, and also correlated with the peel strength of connected ACF. The output of our studies will be use as a guideline on how to determine the % cure of the assembled ACF.

Key Words: 

ACF (Anisotropic Conductive Film), FPC (Flexible Printed Circuit), FT-IR (Fourier Transform Infrared Spectroscopy), DSC (Differential Scanning Calorimetry), cure percentage, function group, peel strength

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