AMIS-4168X Datasheet, PDF (18/20 Pages) AMI SEMICONDUCTOR – Fault Tolerant CAN Transceiver

AMIS-4168x
10.0 Soldering
10.1 Introduction to Soldering Surface Mount Packages
This text gives a very brief insight into 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 (PCBs) with
high population densities. In these situations re-flow soldering is often used.
10.2 Re-flow Soldering
Re-flow soldering requires solder paste (a suspension of fine solder particles, flux and binding agent) to be applied to the PCB 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 the 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.
10.3 Wave Soldering
Conventional single wave soldering is not recommended for surface mount devices (SMDs) or PCBs 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 PCB;
• Smaller than 1.27mm, the footprint longitudinal axis must be parallel to the transport direction of the PCB. 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 PCB. 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.
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