charge . The complementary MOSFETs may be used to
Reflow Soldering
The choice of heating method may be influenced by plastic QFP package). If infrared or vapor phase heating is used
and the package is not absolutely dry (less than 0.1% moisture content by weight), vaporization of the small amount of
moisture in them can cause cracking of the plastic body. Preheating is necessary to dry the paste and evaporate the
binding agent. Preheating duration: 45 minutes at 45 °C.
Reflow soldering requires solder paste (a suspension of fine solder particles, flux and binding agent) to be applied to the
printed-circuit board by screen printing, stenciling or pressure-syringe dispensing before package placement. Several
methods exist for reflowing; for example, convection or convection/infrared heating in a conveyor type oven. Throughput
times (preheating, soldering and cooling) vary between 100 and 200 seconds depending on heating method.
Typical reflow peak temperatures range from 215 to 270 °C depending on solder paste material. The top-surface
temperature of the packages should preferable be kept below 245 °C for thick/large packages (packages with a
thickness 2.5 mm or with a volume 350 mm3 so called thick/large packages). The top-surface temperature of the
packages should preferable be kept below 260 °C for thin/small packages (packages with a thickness < 2.5 mm and a
volume < 350 mm3 so called thin/small packages).
Wave Soldering: Conventional single wave soldering is not recommended for surface mount devices (SMDs) or printedhigh component density, as solder bridging and non-wetting can present major problems.
Manual Soldering: Fix the component by first soldering two diagonally-opposite end leads. Use a low voltage (24 V oapplied to the flat part of the lead. Contact time must be limited to 10 seconds at up to 300 °C. Whtool, all other leads can be soldered in one operation within 2 to 5 seconds between 270 and 320 °C.
