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Material Science and Technology of Japan, 57（2020）28～36

Feb. 2020

Regular Paper
Influence of Seed Layer on LCP Substrate for High-speed
Transmission Characteristics
Tomoyuki ISHII1,2,3,*, Joo-Hyong NOH1,2, Hideo HONMA1,2, Osamu TAKAI1,2 andMitsuhiro WATANABE1,2
1 Graduate School of Engineering, Kanto Gakuin University, 1162-2 Ogikubo, Odawara-shi, Kanagawa

250-0042, Japan
2 Materials and Surface Engineering Research Institute, Kanto Gakuin University, 1162-2 Ogikubo,Odawara-shi, Kanagawa 250-0042, Japan
3 Toppan Printing CO., LTD., 1-5-1 Taitou, Taitou-ku, Tokyo 110-8560, Japan

Received Nov. 15, 2019; accepted for publication Dec. 11, 2019
Abstract
Signal circuits between processor units and connected components in a computing system, require high signaltransmission speed. In order to reduce the transmission loss of the substrate for semiconductor package, it isnecessary to control the manufacturing process. Considering the skin effect in high frequency region, thecharacteristics of the seed layer formed on the LCP (Liquid Crystal Polymer) resin may affect the high-speedtransmission characteristics. However, it has not been verified how the changes of such seed layer states affect thequality of high-speed signal transmission. In this paper, we prepared LCP substrates containing signal copper circuitswith different thickness and conductivity of copper seed layers formed by electroless plating and sputtering.
Furthermore, the S-parameters (S21) of the transmission lines on these substrates were measured. The S-parameter
results suggested that the volume resistivity of the seed layer and the structure of the interface between the seed layer
and the conducting layer affect the transmission characteristics.
Keywords: LCP, Seed Layer, Electroless Plating, Sputtering, Transmission Characteristic

1. Introduction

layer, but for high-speed transmission substrates, it is required toIn order to achieve an advanced information society, theimprove the dielectric properties of the epoxy-based resin toability and speed of signal processing inside and between

reduce the dielectric loss [9, 10]. However, there is a limit to theelectronic devices is constantly increasing [1, 2], and theimprovement of the dielectric properties of the epoxy-based resin

demands is growing year by year. Also for printed wiring boards

in reducing dielectric loss, so it may be difficult to cope withand semiconductor packages, the process design of transmission

further high-speed transmission. Therefore, it is desirable toline adapted for high speed transmission is required [3-5]. It ischange the resin and use an insulating material with better

necessary to match the characteristic impedance matching, selectdielectric properties as substitute resin material [11]. As an

the materials of insulators and conductors, and optimize theinsulating resin suitable for high-speed transmission, a Liquidtransmission structure and so on. High-speed transmission must

Crystal Polymer (LCP) resin having excellent dielectric

reduce the transmission loss of transmission line, especially theproperties has attracted attention. The LCP resin has been used

improvement of dielectric loss and conductor loss is necessary

for flexible printed circuit boards and module boards for antenna[6-8].

applications. In recent years, its applications have been further
expanded [12-16].

For a semiconductor package substrate, an epoxy-based

As for reducing the conductor loss, it is necessary to improveresin is usually used as the insulating material for the build-up*Corresponding author: tomoyuki_1.ishii@toppan.co.jp(28)