june 2011 doc id 10738 rev 2 1/5 AN2027 application note mounting recommendations for ceramic dmos packages introduction this application note provides mounting recommendations for ceramic packages used in the assembly of dmos radio frequency transistors suitable for applications such as ism and fm broadcasting. www.st.com
mounting recommendations for m174, m177 and m244 AN2027 2/5 doc id 10738 rev 2 1 mounting recommendations for m174, m177 and m244 1.1 mounting recommendations ensure holes in heatsin ks are free from burrs minimum depth of tapped holes in heatsinks is 6 mm use 4-40 unc-2a cheese-head screws with a flat washer to spread the joint pressure the minimum flatness of the mounting area is 0.02 mm mounting area roughness should be less than 0.5 m (micro) avoid, as much as possible, use of flux or flux solutions because flux can penetrate even when hermetically sealed ceramic-capped transistors. tin and wash the printed- circuit board before mounting the power transistors, then solder the transistor leads without using flux transistor leads may be tinned by dipping them full-length into a solder bath at a temperature of about 230c. no flux should be used during tinning recommended heatsink compounds : wpsii (silicon free ) from austerlitz electronics, 340 from dow corning etc. 1.2 mounting sequence apply a thin layer of evenly distributed heatsink compound to the flange position the device with flat washers in place tighten the screws until finger tight (0.05 nm) further tighten the screws until the specified torque is reached for m174, m177 & m244 type of packages, torque should be minimum 0.6 nm and 0.75 nm max. table 1. dmos packages - list of materials package type description flange leadframe ceramic insulator plating torque (nm) leads flange min. max. m174 0.500 dia 4l non herm w/flange cu alloy 42 (fe58 / ni42) beo (99.5% min) au (100 min) over ni (100 min / 350 max) ni (100 min) + pd (10 min) 0.6 0.75 m174 (moly disk) 0.500 dia 4l non herm w/flange (moly disk cu-mo-cu alloy 42 (fe58 / ni42) beo (99.5% min) au (100 min) over ni (100 min / 350 max) ni (100 min) + pd (10 min) 0.6 0.75
AN2027 mounting recommendations for m174, m177 and m244 doc id 10738 rev 2 3/5 m177 0.550 dia 4l non herm w/flange cu-mo-cu alloy 42 (fe58 / ni42) beo (99.5% min) au (60 min) over ni (100 min / 350 max) au (100 min) over ni (100 min / 350 max) 0.6 0.75 m244 2x 0.400x0.425 wide 2l lap n/h flange w (85%) - cu (15%) alloy 42 (fe58 / ni42) beo(99. 5% min) au (60 min) over ni (100 min / 350 max) 0.6 0.75 table 1. dmos packages - list of materials (continued) package type description flange leadframe ceramic insulator plating torque (nm) leads flange min. max.
revision history AN2027 4/5 doc id 10738 rev 2 2 revision history table 2. document revision history date revision changes 27-sep-2004 1 initial release. 08-jun-2011 2 document reworked to improve readability, no technical changes.
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