FPC (Flexible Printed Circuit)

In FPC, we are developing products and technologies focusing on mobile and electronic devices, which have long been our main markets, and responding to the growing needs of the automotive market.

Mobile Phones and Electronic Devices

We are working on the development of fine pitch FPC to accommodate with the evolution of electronic information equipment, and high frequency high speed transmission FPC for increasing data transmission speed such as 5G.

<Fine pitch technology>

We are currently in the developing a semi-additive process for the formation of fine pitch circuits for mass production of L/S = 10/10 μm. (See Photo 1)

<High frequency and high speed transmission FPC>

We are developing FPCs for internal wiring and antenna substrates for millimeter-wave bands (28 GHz) that use materials with low permittivity and low dielectric loss tangent that are compatible with 5G. (See Photo 2.) 

Photo 1: Semi-additive Circuit Photograph (L/S = 10/10 μm)	Photo 2: High-speed transmission FPC (Integrated USB and antenna feeding type)

Automotive

As the use of FPCs for automotive applications continues to expand, we are developing FPCs to meet the needs for new functions and performance.

<High Heat-Dissipation FPC>

Among LED lighting applications in automobiles, for headlamp applications with high output, it is necessary to efficiently dissipate the heat generated by LEDs. (See Photo 3.)

<Dissimilar metal bonding technology>

With the aim of applying it to high-current applications using aluminum stiffener used in FPCs as current paths, we have achieved a joint that suppresses the formation of intermetallic compounds in the welding of copper and aluminum using our proprietary welding method with a fiber laser manufactured in-house. (See Photo 4 and Figure 1)

Photo 3: LED Mounted High Heat-Dissipation FPC

Photo 4: Welded area of copper/aluminum plate	Figure 1: Weld Section Overview

Membrane

Fujikura provides membrane wiring board whose circuits are by screen-printing a conductive ink onto polyester film or the other substrates. Recently wearable devices are spotlighted as useful equipment to monitor vital signal for sport player and/or health care, then we are under developing a stretchable membrane which can make electrical circuits directly onto stretchable fabric material. Our conductive ink is designed as not easily absorbed into fabric, optimized stretchable and tough, then it can endure 10,000 cycles of 10% stretching test. It is expected to be useful technology such as medical, health care, and sports activity field.

Stretchable circuits onto fabric/wear (Stretching part : Elbow)	Cross-section view

Stretching test result

Wafer And Board level device Embedded Technology

An Embedded die substrate, a printed circuit board with embedding active/passive components, is greatly paid attention as next generation high-density packaging technology to realize ultra-miniaturization of electronics package by increasing component mounting density.
Fujikura has established an embedded die technology called WABE Technology (R) (Wafer and Board Level Embedded Technology).
This technology consists of Cu redistribution layer on IC wafers (Fan-in RDL) and multilayer polyimide wiring board (FPC) and is under mass production for ultra-small medical devices.
We have expanded this technology and developed "Chip-stack WABE package" for the first time in the world, which is embedded die substrate with stacking multiple ICs in vertically into multilayer FPC.
We started mass production of two chip-stack type WABE package from 2018 and are also ready for three chip-stack type WABE package.
This technology received the 2018 Technology Award from The Japan Institute of Electronics Packaging (JIEP). We will continue to contribute to society through the miniaturization of electronic circuits.

High-density electronics packaging by using embedded die technology, WABE Technology (R)	Three chips stack WABE package	2018 Technical Award of The Japan Institute of Electronics Packaging (JIEP)