ANI-004 Introduction: This application note defines "base- checke

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Base Plate Tempurature Ferrite Isolator/Circulators Application Note
ANI-004
Introduction: This application note defines "base- checked resistance value matching charplate temperature" M/A-COM's circulator/isolator acteristics circulator, both before after test. product lines. choice base-plate materials their impact power handling capability also discussed. Chip resistor base plate: High power chip resistors commonly used stripline-junction ferrite isolators isolated-port terminations. Some circulators also utilize chip attenuators isolated port. main function such terminations/attenuators dissipate reflected power event gross mismatch output port thus protecting other parts system. chip suppliers typically specify power handling capabilities chips with criterion that base-plate kept below certain temperature. Otherwise de-rating factor must used.
Mounted Painted
"Base plate" usually defined chip manufacturers) heat-sink that directly attaches chips, i.e. right underneath chip (see example). This different from where M/A-COM's customers monitor/maintain system temperatures. M/A-COM defines "base-plate temperature" that area bottom side housing assembly beneath high power termination/attenuator. most cases, close approximation this temperature obtained observing area next chip. Fig. 1(a) show inch 1.25 inch drop-in circulator (MAFRIN0472), which 20dB chip attenuator, mounted brass test fixture (M/A-COM part#: SVP08280). area interest then painted black (Fig. 1(b)) facilitate infrared thermal imaging. test fixture itself bolted onto 1.26cm thick aluminum plate (size: 17.5cm 17.5cm) which serves additional heat-sink. Thermal joint compound applied between base-plate fixture, also between fixture heat-sink. Ambient temperature 22oC. extra cooling provided. Fig. shows simulated temperature "AA" cross-section under watts power dissipation. Thermal images (Fig. were taken while chip attenuator dissipated power. chip resistor
Figure MAFRIN0472.
Figure Simulated temperature crosss-section "AA" 1(a). Temperature gradient between lines about Four areas around chip attenuator labeled through were monitored surface temperature with different power inputs. (R1: chip, next chip, test fixture, housing.) results tabulated Table Please note that temperatures uniform within individual areas, both minimum maximum listed. important temperature, concerning power-handling capability chip, area next chip i.e. part expected survive large reflected power extended period time, crucial provide proper heat-sink chip resistors lower temperature
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M/A-COM Inc. affiliates reserve right
make changes product(s) information contained herein without notice. M/A-COM makes warranty, representation garantee regarding suitability products purpose, does M/A-COM assume liability whatsoever arising application product(s) information.
North America Tel:800.366.2266 Fax: 978.366.2266 Europe Tel:44.1908.574.200 Fax: 44.1908.574.300 Asia/Pacific Tel:81.44.844.8296 Fax: 81.44.844.8298
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Base Plate Tempurature Ferrite Isolator/Circulators Application Note
Table Surface temperatures. Surface Temperature min./max 25.4/33.0 26.2/27.6 25.4/26.2 25.1/25.9 29.2/51.2 32.4/35.3 29.2/30.3 29.2/30.0 43.8/115.6 53.8/61.4 43.1/45.6 43.2/44.1 55.1/160.8 73.6/83.7 57.2/60.9 58.2/59.2 65.5/223.6 101.0/114.5 75.4/79.9 76.2/77.6
ANI-004
Power level
Table Thermal Conductivities. Material Cold Rolled Steel (CRS1010) 49.8 Free-Cutting Brass (C36000) Aluminum Alloy (6061-T6) Tough Pitch Copper (C11100)
measured (and simulated[2]) temperatures were plotted Fig. same plot also shows specification chip attenuator) with proper de-rating factor. When large power being dissipated, temperature outside base-plate good indication chip-resistor environment (relevant health chip resistors). This situation different from normal operation, when fixture temperature Figure M/A-COM circulator with steel machined good estimation junction temperature (relevant housing. proper operation circulators/isolators). Thermal grease underneath base-plate reduce Conclusion: this application note, M/A-COM detemperature area much case fines "base-plate temperature" (the area botof watts dissipated power. side housing assembly beneath chip Base-plate Material: Thermal images simula- termination/attenuator), based experimental tions confirm that temperature difference between simulated results. operating temperature considR2 (area next chip) (fixture) ered same base plate temperature unless substantial; even though both copper brass otherwise specified. applications where circulagood heat conductors. (MAFRIN0472 uses copper tors/isolators expected sustain large disbase-plate, M/A-COM part#: 1000010333-0008). sipated power, M/A-COM recommends using copper parts that base-plates made from material with poor other material with good heat-conducting property) thermal conductivity (such steel), heat will base-plate material assist heat removal. Ther"trapped" around chip. This results even greater grease underneath base plate also highly rectemperature differences between region ommended. Table lists thermal conductivities materials. separate experiment, chip attenuators were mounted onto steel base-plates (Fig. temperatures monitored area were substantially higher compared previous experiment (copper base-plate). Consequently, resistor survived dissipated power greater than watts more than seconds unless unit placed cold plate temperature lower than -10oC.
References
Product Catalog 2004-006, Barry Industry, Inc. Walton Attleboro, Massachusetts, 02703, U.S.A. IcePak, Version: 4.1.12, Fluent Inc., Cavendish Court, Centerra Park, Lebanon, Hampshire 03766, U.S.A.
Page
M/A-COM Inc. affiliates reserve right
make changes product(s) information contained herein without notice. M/A-COM makes warranty, representation garantee regarding suitability products purpose, does M/A-COM assume liability whatsoever arising application product(s) information.
North America Tel:800.366.2266 Fax: 978.366.2266 Europe Tel:44.1908.574.200 Fax: 44.1908.574.300 Asia/Pacific Tel:81.44.844.8296 Fax: 81.44.844.8298
Visit www.macom.com additional data sheet product information.
Base Plate Tempurature Ferrite Isolator/Circulators Application Note
ANI-004
Figure Thermal images MAFRIN0472 while dissipating power.
(Top Chip) (Next Chip) (Fixture) (Top Can) (Sim. Steel B.P.) (Sim. Copper B.P.) Surface Temperature
Spec.
Spec. de-ra
ting
Within Spec.
Dissipated Power (Watts)
Figure Base-Plate Temeratures versus Power Dissipation.
Page
M/A-COM Inc. affiliates reserve right
make changes product(s) information contained herein without notice. M/A-COM makes warranty, representation garantee regarding suitability products purpose, does M/A-COM assume liability whatsoever arising application product(s) information.
North America Tel:800.366.2266 Fax: 978.366.2266 Europe Tel:44.1908.574.200 Fax: 44.1908.574.300 Asia/Pacific Tel:81.44.844.8296 Fax: 81.44.844.8298
Visit www.macom.com additional data sheet product information.

ANI-004 Introduction: This application note defines "base- checke

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