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Characteristics of EPIG Deposits for Fine-Line Applications
January 28, 2014 |Estimated reading time: 1 minute
Introduction
In recent years, electronic devices, such as a smartphone and a tablet PC, have been miniaturized. Therefore, chip size package (CSP) used inside the electronic devices have also been miniaturized, and the space of the wiring lines have become narrower every year. Some of latest packages have the space of the wiring line of 15 µm or less. At that time, if electroless Ni-P (EN) film will be 5 to 6 µm as the conventional ENEPIG process, the space of the wiring line became 5 µm or less. This will indicate that there is the risk of short-circuit between the wiring lines. In order to prevent this problem, thin EN process or EN free process (EPIG) will be suggested. If using thin EN or EPIG process, it’s possible to make the plating process time short. In addition, EPIG process may have the possibility for high-frequency devices and the solution for Ni allergy problem.
On the other hand, CSPs have mainly two kinds of the joining method with the substrate or IC chip, which are wire bonding joining between IC chip and the packaged and some type of solder joint. Therefore, for the plating it’s necessary for EPIG process to focus on SJR, WBR, and the pattern ability.
In this paper, we studied these characteristics of EPIG deposits, compared with ENEPIG deposits.
Experiment and Results
The coupons used in this study consisted of a copper-clad laminated substrate which were copper plated to a thickness of 20 µm using an acid copper electroplating process. For SJR tests, the copper-plated substrate was coated with solder mask and imaged to form 0.25 mm diameter solder ball pads. Furthermore, the substrate of the copper pattern with 15 µm space of the wiring line was used for evaluating of the pattern ability. Each substrate was plated with EPIG and ENEPIG by using plating chemicals commercially available from C. Uyemura & Co., Ltd.Read the full article here.Editor's Note: This article originally appeared in the January 2014 issue of The PCB Magazine.