2004 Jan 28 17
NXP Semiconductors Product specification
22 W BTL or 2 11 W
stereo power amplifier TDA1519C
SOLDERING
Introduction
This text gives a very brief insight to a complex technology.
A more in-depth acco unt of soldering ICs can be fou nd in
our “Data Hand book 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 fine
pitch SMDs. In these situations reflow soldering is
recommended. Driven by legislation a nd environmenta l
forces the worldwide use of lead-free solder paste s is
increasing.
Through-hole mount packages
SOLDERING BY DIPPING OR BY SOLDER WAVE
Typical dwell time of the le ads in the wave ranges from
3 to 4 seconds at 250 C or 265 C, depending on solder
material applied, SnPb or Pb- f ree respectively.
The total contact time of successive solder waves must not
exceed 5 seconds.
The device may be mounte d up to the seating plane, but
the temperature of the plastic bod y mus t not ex ceed the
specified maximum storage temperature (Tstg(max)). If the
printed-circuit board has been pre-heated, forced cooling
may be necessary immediately after soldering to keep the
temperatur e with in the pe rmissible limit.
MANUAL SOLDERING
Apply the soldering iron (24 V or less) to the lead(s) of the
package, either below the seating plane or not more than
2 mm abov e it. If the temperature of the soldering iron bit
is less than 300 C it may remain in contact for up to
10 sec onds. If the bit temperature is between
300 and 400 C, contact may be up to 5 seconds.
Surface mount p ackages
REFLOW SOLDERING
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, stencilling or
pressure-syringe dispensing before package plac ement.
Several methods exist for reflowing; for example,
convection or co nvection/infrared heating in a conveyor
type oven. Through pu t times (preheating, soldering and
cooling) vary between 100 and 200 seconds depending
on heating method.
Typical reflow peak temperatures range from
215to270C depending on solder paste material. The
top-surface temperature of the packages should
preferably be kept:
below 22 5 C (SnPb process) or be low 245 C (Pb-free
process)
– for all the BGA, HTSSON..T and SSOP-T packages
– for packages with a thickness Š 2.5 mm
– for packages with a thickness < 2.5 mm and a volume
350 mm3 so called thick/large packages.
below 24 0 C (SnPb process) or be low 260 C (Pb-free
process) for packages with a thickness < 2.5 mm and a
volume < 350 mm3 so called small/thin packages.
Moisture sensitivity precautions, as indicated on packing,
must be respected at all times.
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 p res ent major problems.
To overcome these problems the double-wave soldering
method was sp ecifically developed.
If wave soldering is used the following conditions must be
observed for optimal results:
Use a double-wa ve soldering meth od comprising a
turbulent wave with high upward pressur e followed by a
smooth laminar wave.
For packages with leads on two sides and a pitch (e):
– larger than or equal to 1.27 mm, the footprint
longitudinal axi s is preferred to be parallel to the
transport direction of the printed-circuit board;
– smaller than 1.27 mm, the footp rint 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 plac ed at a 45 angle to the transp ort direction of the
printed-circuit board. The footprint must incorporate
solder thieves dow nstream and at the s id e c orners.
During placement and before soldering, the package must
be fixed with a droplet of adh es ive. The adhesive can be
applied by screen printing, pin transfer or syringe