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ASDL-7021 Scheda tecnica(PDF) 22 Page - Lite-On Technology Corporation |
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ASDL-7021 Scheda tecnica(HTML) 22 Page - Lite-On Technology Corporation |
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22 / 23 page ![]() Recommended Reflow Profile Process Zone Symbol DT Maximum DT/Dtime or Duration Heat Up P, R 5°C to 50°C °C/s Solder Paste Dry P, R 50°C to 00°C 60s to 80s Solder Reflow P, R P, R4 00°C to 55°C 55°C to 00°C °C/s -6°C/s Cool Down P4, R5 00°C to 5°C -6°C/s Time maintained above 7°C > 7°C 60s to 50s Peak Temperature 60°C Time within 5°C of actual Peak Temperature > 55°C 0s to 40s Time 5°C to Peak Temperature 5°C to 60°C 8mins The reflow profile is a straight-line representation of a nominal temperature profile for a convective reflow solder process. The temperature profile is divided into four process zones, each with different DT/Dtime tem- perature change rates or duration. The DT/Dtime rates or duration are detailed in the above table. The tempera- tures are measured at the component to printed circuit board connections. In process zone P1, the PC board and ASDL-7021 pins are heated to a temperature of 150°C to activate the flux in the solder paste. The temperature ramp up rate, R1, is limited to 3°C per second to allow for even heating of both the PC board and ASDL-7021 pins. Process zone P2 should be of sufficient time duration (100 to 180 seconds) to dry the solder paste. The temper- ature is raised to a level just below the liquidus point of the solder, usually 200°C (392°F). Process zone P3 is the solder reflow zone. In zone P3, the temperature is quickly raised above the liquidus point of solder to 255°C (491°F) for optimum results. The dwell time above the liquidus point of solder should be between 20 and 40 seconds. It usually takes about 20 seconds to assure proper coalescing of the solder balls into liquid solder and the formation of good solder con- nections. Beyond a dwell time of 40 seconds, the inter- metallic growth within the solder connections becomes excessive, resulting in the formation of weak and un- reliable connections. The temperature is then rapidly reduced to a point below the solidus temperature of the solder, usually 200°C (392°F), to allow the solder within the connections to freeze solid. Process zone P4 is the cool down after solder freeze. The cool down rate, R5, from the liquidus point of the solder to 25°C (77°F) should not exceed 6°C per second maximum. This limitation is necessary to allow the PC board and ASDL-7021 pins to change dimensions evenly, putting minimal stresses on the ASDL-7021. 50 100 150 200 250 300 t-TIME (SECONDS) 25 80 120 150 180 200 230 255 0 R1 R2 R3 R4 R5 217 MAX 260C 60 sec to 180 sec Above 217 C P1 HEAT UP P2 SOLDER PASTE DRY P3 SOLDER REFLOW P4 COOL DOWN |
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