CHARACTERIZATION OF ENVIRONMENT-FRIENDLY HALOGEN-FREE MATERIALS FOR RADIO FREQUENCY ELECTRONICS USEAuthor: Terry Fischer
Company: Hitachi Chemical Co. America
Date Published: 9/22/2002 Conference: SMTA International
Hitachi Chemical Co., Ltd. developed halogen-free materials (laminate, prepreg and build-up materials) for multi-layer boards. Major Japanese OEMs are removing halogen compounds from products and making them environmentally friendly. The resultant materials satisfy the UL 94V-0 standard without using any halogenated compounds.
Motorola along with Hitachi Chemical developed a strategy to implement the environmentally preferred technologies into various products based on Market and Competition. In an effort to identify laminate materials, which are acceptable for high frequency, high performance electrical applications, the characteristics of Bromine, free material was benchmarked with commercial FR-4 material.
Regarding the flame-retardants other than the halogenated compounds, nitrogen compounds, phosphorus compounds or inorganic filler are generally known. To achieve UL 94V-0, we need to add a substantial amount of these flameretardants. However, these materials influence the properties of PWBs: heat resistance and the pollution rate of medical liquids used in the production process of the PWBs.
Hitachi Chemical has achieved the flammability level (UL 94V-0) by developing a modified epoxy resin containing a new aromatic resin (BE resin). Because this BE resin has an extremely low rate of flammability, due to its aromatic and nitrogen rich molecule structure, we could reduce the quantity of other flame-retardants.
These halogen-free materials also have good heat resistance, high elastic modulus at high temperature and low coefficient of thermal expansion. They are able to meet the requirements of PWB manufacturing processes at a higher temperature in soldering process using a lead-free solder and the highly reliable use of the resin to a thinner and higher-density PWB.
Based on dielectric constant, loss tangent, copper peel strength, glass transition temperature, Z-CTE, ease of processing and plated through-hole reliability, these materials were assessed in a high performance circuit.
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