AMIS-30623 Datasheet, PDF (63/65 Pages) AMI SEMICONDUCTOR – LIN Microstepping Motordriver

AMIS-30623
19.0 Soldering
19.1 Introduction to Soldering Surface Mount Packages
This text gives a very brief insight to a complex technology. A more in-depth account of soldering ICs can be found in the AMIS “Data
Handbook IC26; Integrated Circuit Packages” (document order number 9398 652 90011). There is no soldering method that is ideal for
all surface mount IC packages. Wave soldering is not always suitable for surface mount ICs, or for printed-circuit boards with high
population densities. In these situations reflow soldering is often used.
19.2 Re-flow Soldering
Re-flow 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, stencilling or pressure-syringe dispensing before package placement. Several methods exist for reflowing; for
example, infrared/convection heating in a conveyor type oven.
Throughput times (preheating, soldering and cooling) vary between 100 and 200 seconds depending on heating method.
Typical re-flow peak temperatures range from 215 to 250°C. The top-surface temperature of the packages should preferably be kept
below 230°C.
19.3 Wave Soldering
Conventional single wave soldering is not recommended for surface mount devices (SMDs) or printed-circuit boards with a high
component density, as solder bridging and non-wetting can present major problems. To overcome these problems the double-wave
soldering method was specifically developed.
If wave soldering is used the following conditions must be observed for optimal results:
• Use a double-wave soldering method comprising a turbulent wave with high upward pressure followed by a smooth laminar
wave.
• For packages with leads on two sides and a pitch (e):
• Larger than or equal to 1.27mm, the footprint longitudinal axis is preferred to be parallel to the transport direction of
the printed-circuit board;
• Smaller than 1.27mm, the footprint longitudinal axis must be parallel to the transport direction of the printed-circuit
board. The footprint must incorporate solder thieves at the downstream end.
• For packages with leads on four sides, the footprint must be placed at a 45º angle to the transport direction of the printed-
circuit board. The footprint must incorporate solder thieves downstream and at the side corners.
During placement and before soldering, the package must be fixed with a droplet of adhesive. The adhesive can be applied by screen
printing, pin transfer or syringe dispensing. The package can be soldered after the adhesive is cured.
Typical dwell time is four seconds at 250°C. A mildly-activated flux will eliminate the need for removal of corrosive residues in most
applications.
19.4 Manual Soldering
Fix the component by first soldering two diagonally-opposite end leads. Use a low voltage (24V or less) soldering iron applied to the flat
part of the lead. Contact time must be limited to 10 seconds at up to 300°C. When using a dedicated tool, all other leads can be
soldered in one operation within two to five seconds between 270 and 320°C.
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