Abstract

Tetrabromobisphenol A (TBBPA) is the major flame retardant used in laminates for FR4 printed wiring boards (PWB) for electrical and electronic equipment. In this application, TBBPA is reacted with epoxy resin to form part of the polymeric backbone of the resin. No regulations exist that prohibit the use of TBBPA anywhere in the world. It is one of the most scientifically tested and most cost effective flame retardant available on the market. European Union Risk Assessment on TBBPA was recently closed and concluded that it was safe for continued use. Due to the positive EU Risk Assessment, no further studies should be needed to register TBBPA under the new European chemicals program, REACH. Several projects are currently in progress to determine the various characteristics and overall acceptability of materials being considered alternatives to TBBPA. This paper will review the assessments and projects related with the use of TBBPA in PWB applications.

Introduction

The use of flame retardants has had a positive impact on the overall safety of homes, hotels, hospitals, nursing homes, offices, automobiles, and public transportation. Countless lives have no doubt been saved by the use of flame retardants [1]. Flame retardants are used to delay the spread of fires or delay the time of flashover to enable people time to escape. It is estimated that escape times can be up to 15 times longer when flame retardants are present, providing increased chances of survival [2]. While fire continues to be an ever-present threat to society, chemicals, including flame retardants, have been the object of considerable scrutiny [3, 4]. These attacks and criticism stem from the fact that low levels of particular materials can and have been detected in the environment and, in some cases, in animals and humans. The scrutiny, criticism, and general misinformation ultimately have resulted in marketing pressure to eliminate specific chemicals or classes of chemicals, even without scientific justification or legislation to restrict these materials being in place.

Tetrabromobisphenol A (TBBPA) is the major flame retardant used in laminates for FR4 printed wiring boards (PWB) for electrical and electronic equipment. TBBPA is also used as an additive flame retardant in some electronic housing applications. In FR4 PWB applications, TBBPA is reacted with epoxy resin to form part of the polymeric backbone of the resin. FR4 PWB hold microchips and other electronic components used to run computers, telecommunications equipment, industrial controls and other devices. Because the very function of circuit boards is to transmit electrical charges, flame retardants are an absolute necessity. Exposed to constant heat and electrical current, PWB base laminates can be made of either epoxy or phenolic (thermoset) resins, rigid or flexible that are required to meet certain flammability standards. (FR-4 boards, for example, must meet UL94 V-1 ratings). Approximately 90% of the PWB produced meet the UL 94 V-0 standard for fire safety [5]. TBBPA has been the flame retardant of choice in PWB applications for around 30 years.

Flame Retardant Regulatory Activity

The pressure that chemicals have come under has lead to a patchwork of worldwide chemical regulations. Evaluation of the risks of chemicals is the current focus of many regulatory programs. This approach takes into account the hazard of a substance, plus the exposure to the substance to determine the risk. The European Union Risk Assessment program is one process that has been in place for over ten years that is used to evaluate the characteristics of a variety of high production volume chemicals. Another program that entered into effect on July 1, 2007 in the European Union is the Registration, Evaluation and Authorization of Chemicals (REACH). The principle of REACH is "no data, no market." This approach is welcomed, as the importance to ensure that all flame retardants are safe for use, now and in the future is well recognized. In order to do this, regulatory decisions need to be based on sound science. The regulation system in place also needs to be adhered to and accepted by everyone. If society is to operate effectively and efficiently, then acceptance of good regulatory programs is of the utmost importance. No regulations exist that prohibit the use of TBBPA anywhere in the world. It is one of the most scientifically tested and most cost effective flame retardant available on the market.

EU Risk Assessment

The European Union (EU) Risk Assessment ("Council Regulation [EEC] 793/93 of 23 March 1993") [6] is well-recognized as being the leading independent, transparent, and science-based system for assessing chemicals and substances in everyday use [7]. It has been in place for over ten years and has been used to evaluate the characteristics of a variety of high production volume chemicals. It is the most comprehensive of current global assessment programs for human health and environmental characteristics. Several flame retardants have completed or are currently undergoing EU Risk Assessments. Each flame retardant is being assessed individually, not as a class. This process examines critical aspects of a chemical, including mammalian and environmental toxicology, environmental fate and releases (to water, soil, air, and from all operations throughout the lifecycle), and risk (exposures versus limits). After all this information is generated, a hazard assessment, exposure assessment, risk identification, and risk management is generated. This will determine whether there is a need for more testing or whether there is a need for risk reduction. The risk assessment is the basis for the future legislation on the use of these substances in the European Union.