saa5290ps NXP Semiconductors, saa5290ps Datasheet - Page 68

• Manufacturer Part Number: saa5290ps
• Description: Economy Teletext And Tv Microcontrollers
• Manufacturer: NXP Semiconductors

Philips Semiconductors
18 SOLDERING
18.1
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. However, 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.
18.2
18.2.1
The maximum permissible temperature of the solder is
260 C; solder at this temperature must not be in contact
with the joints for more than 5 seconds. The total contact
time of successive solder waves must not exceed
5 seconds.
The device may be mounted up to the seating plane, but
the temperature of the plastic body must not exceed the
specified maximum storage temperature (T
printed-circuit board has been pre-heated, forced cooling
may be necessary immediately after soldering to keep the
temperature within the permissible limit.
18.2.2
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 above it. If the temperature of the soldering iron bit
is less than 300 C it may remain in contact for up to
10 seconds. If the bit temperature is between
300 and 400 C, contact may be up to 5 seconds.
18.3
18.3.1
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 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.
1998 Dec 14
Economy teletext and TV microcontrollers
Introduction
Through-hole mount packages
Surface mount packages
S
M
R
OLDERING BY DIPPING OR BY SOLDER WAVE
EFLOW SOLDERING
ANUAL SOLDERING
stg(max)
). If the
68
Typical reflow peak temperatures range from
215 to 250 C. The top-surface temperature of the
packages should preferable be kept below 230 C.
18.3.2
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:
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 4 seconds at 250 C.
A mildly-activated flux will eliminate the need for removal
of corrosive residues in most applications.
18.3.3
Fix the component by first soldering two
diagonally-opposite end leads. Use a low voltage (24 V 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 2 to 5 seconds between
270 and 320 C.
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 1.27 mm, the footprint
– smaller than 1.27 mm, the footprint longitudinal axis
The footprint must incorporate solder thieves at the
downstream end.
For packages with leads on four sides, the footprint must
be placed at a 45 angle to the transport direction of the
printed-circuit board. The footprint must incorporate
solder thieves downstream and at the side corners.
longitudinal axis is preferred to be parallel to the
transport direction of the printed-circuit board;
must be parallel to the transport direction of the
printed-circuit board.
W
M
ANUAL SOLDERING
AVE SOLDERING
SAA5x9x family
Preliminary specification