Vol. 53 No. 5Material Science and Technology of Japan, 53㸦2016㸧163㹼166

15Regular Paper

Low Aspect Ratio Through-hole Filling by Copper Electroplating
Young-Jae KIM* 1, 2, 3, Jae-Hee CHON2, 3, Jong-Young PARK2, 3, Mitsuhiro
WATANABE2, Joo-Hyong NOH2, Hideo HONMA2 and Osamu TAKAI1, 2
1

Department of Industrial Chemistry, Graduate School of Engineering, Kanto Gakuin University,
1-50-1 Mutsuura-higashi, Kanazawa-ku, Yokohama 236-8501, Japan

2

Materials & Surface Engineering Research Institute, Kanto Gakuin University, 1-1-1 Fukuura, Kanazawaku, Yokohama 236-0004, Japan

3Daeduck Electronics Co. Ltd, 335, Somanggongwon-ro, Siheung-si, Gyeonggi-do 15106, Korea

Received Aug. 17, 2016; accepted for publication Sep. 14, 2016
Abstract
Many factors effect Electro-copper plating of PCB (Printed Circuit Board) substrates, this plating determines
through-hole for 3D electro-connection structures and brightness of surface. As technology developes, necessityof thin board, low aspect ratio through-hole filling will be studied. In this study, the parameters of three major
items that additives, current density, and the stirring of plating chemicals inside the plating bath have beenreviewed. It can be concluded that the input current methods and stirring have the greatest impact on filling ofthrough-holes with low aspect ratio. However, when simply step up current and no-stirring conditions were used
to increase the filling nature of plating, occurred void and irregular plating on the surface. In order to prevent
voids and irregular plating, consider that concentration rate of PEG (polyethylene glycol) was increased from 10ppm to 100 ppm.
Key Words : Low Aspect Ratio Through-hole Filling, Printed Circuit Board , Additive, Step Current Density

1. Introduction

However, as PCB is getting thinner, low aspect ratio holes require
through-hole filling technology with uniform plating thickness while

Recently, IoT (Internet of Things) is expected to take over not only
electronic devices such as smart phones, but everything that surrounds us

avoiding any incomplete hole filling. Sputtering is one way to create thinand is connected to the internet. This will bring rapid changes to the basis

metal layer, but the past research items our research group publishedof our lives and businesses, and will increase the demands of wearable

including via-filling and high aspect ratio through-hole filling weredevices over mobile devices such as smartphone, tablet PC, etc. Suchreferenced in this study. We report on the increase level of filling inside

demands for wearable device will require higher performance, smaller

through-holes and the level of surface uniformity while suppressing thedimensions and thickness, and less weight, as well as the need for higher

plating on surface layer during filling of low aspect ratio through-holes indegree of integration of PCB that interconnects each component inPCB.

electronic devices [1, 2]. However, increasing degree of integration puts

2. Experimental method

the thermal problem on the rise where components generate heat thatSpecimens for this experiment were 40 ǋm thick polyimide (UBE

needs to be effectively dissipated into thermal paths in PCB.

Industries, LTD., UPILEX®) resin cut to 50 mm by 75 mm, where 100

One way to increase thermal conductivity of the board and maintainits components and traces’ high level of performance is to fill in through-holes with diameter of 75 ǋm were drilled with UV laser at 375 ǋm pitch.

holes of PCB by electrolytic plating [3, 4].

These holes have aspect ratio of 1: 0.5. The top and cross-sectional viewof the prepared specimens are shown in Figure 1.

Corresponding author: jnsc2000@daeduck.com(163)