Fuse Mounting Accessories Page 18 Fuse & Mounting Accessories

2017 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 03/03/17 Surface Mount Fuses Ceramic Fuse > 437 Series Average Time Current Curves .250A 4A 3.5A 3A 2.5A 2A 1.75A 1.5A 1.25A 1A .500A .375A 7A 5A .750A 8A 0.001 0.01 0.1 1 10 TIME IN SECONDS 0.1 1 10 100 CURRENT IN AMPERES Reflow Condition Pb - free assembly Pre Heat - Temperature Min (T s(min) ) 150C - Temperature Max (T s(max) ) 200C - Time (Min to Max) (t s ) 60 - 180 seconds Average Ramp-up Rate (Liquidus Temp (T L ) to peak) 3C/second max. T S(max) to T L - Ramp-up Rate 5C/second max. Reflow - Temperature (T L ) (Liquidus) 217C - Temperature (t L ) 60 - 150 seconds Peak Temperature (T P ) 260 +0/-5 C Time within 5C of actual peak Temperature (t p ) 10 - 30 seconds Ramp-down Rate 6C/second max. Time 25C to peak Temperature (T P ) 8 minutes max. Do not exceed 260C Soldering Parameters Temperature Re-rating Curve 40 60 80 100 120 140 -65 -45 -25 -5 15 35 55 75 95 115 135 155 TEMPERATURE (C) PERCENT OF RATING Time Temperature T P T L T S(max) T S(min) 25 t P t L t S time to peak temperature (t 25C to peak) Ramp-down Ramp-up Preheat Critical Zone T L to T P Example: For continuous operation at 75 degrees celsius, the fuse should be rerated as follows: I = (0.80)(0.85)I RAT = (0.68)I RAT Note: 1. Re-rating depicted in this curve is in addition to the standard re-rating of 20% for continuous operation. Wave Soldering 260C, 10 seconds max.

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