News Release

September 8, 2010
Hitachi Chemical Co., Ltd.

Developed “CF Series,” a Conductive Film for Solar Cells- Alternative to Solder-Enabled Low-Temperature Bonding of Cells and Tab Ribbons -

Hitachi Chemical Co., Ltd.(Head Office: Tokyo; CEO and President: Kazuyuki Tanaka; paid-in capital: 15.5 billion yen, hereinafter “Hitachi Chemical”) developed “CF Series,” a conductive film for solar cell. The CF Series is a conductive film for bonding tab ribbon when connecting crystalline silicon solar cell in series; it is also applicable to thin-film and organic compound PV modules. Currently, sample evaluation work is in progress with many customers, targeting the annual sales of 10.0 billion yen in the fiscal year 2015 to meet the trend of spreading solar cell systems.

With a crystalline silicon solar cell that is the current mainstream solar cell, the silicon wafer has become thinner to reduce costs. At present, solder is used for connecting a tab ribbon to a bus bar. However, soldering requires a high temperature that causes stress to the cell, resulting in a bend or crack in the case of a thin cell. Furthermore, environmentally friendly lead-free solder, which is used in some cases these days, requires a higher temperature of 260 °C or more. Therefore, an alternative material to solder had been desired.

Then, Hitachi Chemical focused on the proven technology for designing resin and dispersion developed for “ANISOLM,” an anisotropic conductive film developed in 1984 as a circuit connection material for display devices, realized low temperature and short time processing. Based on the technology, we successfully developed the CF Series after several years of development. The CF Series is a material whose conductive particles are dispersed in thermosetting resins; it is lead-free (RoHS compliant) and enables low-temperature bonding at 180 °C. This material can avoid bending or cracking of a thin cell when it is connected to a tab ribbon, while being environmentally friendly.

The CF Series is also expected to enhance power generating efficiency with wider light-receiving area because of no flowing of solder. Moreover, the bus bar can be narrower or eliminated because no solder wettability is required. Therefore, the amount of Ag paste applied to cells for forming bus bar can be reduced, which leads cost reduction.

Currently, Hitachi Chemical is globally promoting the CF Series to expand its sales, and its evaluation by solar cell manufacturers has yielded good results. We will further expand the sales to meet the trend of spreading solar cell systems.

Hitachi Chemical will continue to contribute to the society through technology and product development for facilitating the use of recyclable energy that is a shared challenge in our society.

< Reference >

1. “CF Series,” the Conductive Film for Solar Cell (Right) and Solar Cell

2. Cross-Sectional View of Bonded Solar Cell and Tab Ribbon Using “CF Series”