Surface-Mount Filters Meet RoHS Requirements

Oct. 15, 2008
For applications that require RoHS compliance, these lines of RF/microwave surface-mount filters provide high rejection without high trace amounts of lead.

Hazardous waste from disposal of electronic products should be a concern to all involved with electronic design. The Restriction of Hazardous Substances (RoHS) Directive adopted by the European Union (EU) in 2003, of course, set limits on certain hazardous materials in the manufacture of electronic equipment. Although adoption of the RoHS guidelines has not been universal, those seeking components that comply with the RoHS Directive will usually find some mention of that compliance on product data sheets. And for those in need of surface-mount RF/ microwave filters, there is Bree Engineering Corp. (www.breeeng.com).

As RoHS regulations are extended to affect the reflow soldering of surfacemount components used by RF/microwave circuit designers, the importance of ensuring that high-frequency components are truly RoHS compliant only grows. Although the RoHS Directive was adopted by the EU about 5.5 years ago, Bree Engineering has been producing lead-free surface-mount filters and multiplexers for almost 10 years.

Bree Engineering offers extensive lines of RF and microwave surface-mount-technology (SMT) filters from 100 kHz to 8 GHz, including lowpass, highpass, bandpass, and band-reject types. The firm also supplies lumpedelement and cavity filters with connectors and feedthrough connections. Filters in SMT packages are available with or without a solder mask. An advantage of having a solder mask applied to the bottom of the filter is the tightly controlled positioning possible for applications requiring reflow mounting. But a packaged filter without the bottom-mounted solder mask will provide better electrical isolation due to the improved groundplane. Also, the solder mask tends to lift the package slightly off the mounting surface, causing stray inductance.

Many SMT filters are designed for a standard SN62 solder-reflow profile. Bree Engineering's SMT filters survive higher solder reflow temperature profiles (SN95) so that their system printed-circuit boards (PCBs) would be RoHS compliant, the firm began an engineering development project to comply with the needs of their customers. As a result, the company has developed new materials and processes that are stable at much higher temperatures than the industry standard. The results are products that withstand SN95 or SN96 reflow processes of +245C (+473F) without damage.

Bree Engineering offers SMT filters in packages with lengths of 0.5, 0.75, 1.0, and 1.50 in. Examples include model 800819, which is a five-section lumped-element bandpass filter measuring just 0.75 x 0.50 x 0.20 in. It operates with a 600-MHz bandwidth centered at 4.7 GHz. The firm's 800825 model filters (see figure) are a series of filters that are ideal for use in multi-channel compact avionics transceivers. The low-profile bandpass filter features a typical 3-dB bandwidth of 10 MHz centered at 76 MHz, with the selectivity of a five-section Chebyshev filter. The well-designed filter, which measures a mere 1.50 x 0.50 x 0.23 in., controls group delay to 4 ns or less. Bree Engineering Corp.; 1275 Stone Dr., San Marcos, CA 92069; (760) 510-4950; E-mail: [email protected]; Internet: www.breeeng.com.

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