
Philips Semiconductors
SC16C650A
Universal Asynchronous Receiver/Transmitter (UART)
with 32-byte FIFO and infrared (IrDA) encoder/decoder
Product data
Rev. 03 — 13 March 2003
45 of 49
9397 750 11207
Koninklijke Philips Electronics N.V. 2003. All rights reserved.
12. Soldering
12.1 Introduction
This text gives a very brief insight to a complex technology. A more in-depth account
of soldering ICs can be found in our
Data Handbook IC26; Integrated Circuit
Packages (document order number 9398 652 90011).
There is no soldering method that is ideal for all IC packages. Wave soldering is often
preferred when through-hole and surface mount components are mixed on one
printed-circuit board. Wave soldering can still be used for certain surface mount ICs,
but it is not suitable for ne pitch SMDs. In these situations reow soldering is
recommended.
12.2 Surface mount packages
12.2.1
Reow soldering
Reow soldering requires solder paste (a suspension of ne solder particles, ux 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 reowing; 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 reow peak temperatures range from 215 to 250
°C. The top-surface
temperature of the packages should preferably be kept:
below 220
°C for all the BGA packages and packages with a thickness ≥ 2.5mm
and packages with a thickness <2.5 mm and a volume
≥350 mm3 so called
thick/large packages
below 235
°C for packages with a thickness <2.5 mm and a volume <350 mm3 so
called small/thin packages.
12.2.2
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 specically
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.