Enabling the Next Generation of Mobile Devices with Dow Resins

According to the Cellular Telecommunications and Internet Association (CTIA), the international association for the wireless telecommunications industry, the world has more than 2.3 billion mobile subscribers today. On average, those subscribers replace their mobile devices once every 18 months.

This market turnover provides both opportunities and challenges for everyone in the industry, including cellular equipment providers, fabricators and raw material solution providers like Dow.

The Evolution of Electrical Laminates
The answers to meeting these challenges begin in examining the evolution of electrical laminates during the past years. Until a few years ago, Flame Resistant 4 (FR-4) laminates were fabricated using brominated epoxy resin and dicyandiamide (Dicy) as the primary curing agent.

But as a result of the Restriction of the use of certain Harzardous Substances (RoHS) enacted in June 2006 by the European Parliament, the primary solder material was changed from traditional tin-lead (SnPb) to lead-free alloys, which have a melting point 20 to 30 degrees Celsius (C) higher.

In order to resist higher soldering temperatures, fabricators turned to phenolic curing agents to form brominated laminates. These systems offered higher glass transition (Tg) and decomposition temperatures (Td) - two important factors in determining thermal stability. The tradeoffs were reduced toughness and adhesion, resulting in a higher occurrence of product failure or delamination and a less user friendly processing product.

Dow Introduces BF 180 Epoxy Resins for Dicy Cure Systems
In 2006 in Asia-Pacific, Dow introduced BF 180 (XZ 92740.00 epoxy resin solution and XZ 92741.00 co-hardener solution), a bromine-free (near zero) resin system for Dicy cure formulations with UL V0 qualification without the addition of other flame retardants such as inorganic fillers.

Using these resins, fabricators have achieved Tg as high as 180 C and Td as high as 380 C, as well as improved performance, including better signal integrity due to lower dielectric constant and loss, higher transmission rates and lower signal loss.

Testing shows these new epoxy resin systems reduce the laminate's density, which should allow for lighter boards with greater resistance to the thermal stresses during lead-free soldering.

Thanks to the very good adhesion properties obtained from the Dicy cure formulations, formulators can add in inorganic fillers to further reduce the coefficient of thermal expansion (CTE) at high temperatures and hence to improve the reliability of the finished board.

"Our customers are calling BF 180 resin one of the best solutions on the market," says Hideki Horito, global marketing manager for electrical laminates at Dow.

The Results - Innovations in Mobile Communication and Entertainment Media
"These resins allow fabricators to develop bromine-free electrical laminates with improved thermal resistance, adhesion, toughness and better electrical properties," Dow product research and bromine-free project leader Joseph Gan explains. "Those laminates enable smaller and bromine-free circuit boards with more functionality and processing power. Electronics manufacturers are using the smaller boards to develop smaller, more functional mobile devices, such as cell phones, iPods® and MP3 players."

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®iPod is a registered trademark of Apple Computer.

™* Trademark of The Dow Chemical Company ("Dow") or an affiliated company of Dow.